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Keels or Daggerboards, the pros and cons

When writing about foils (ie boards, keels and rudders) it is easy to baffle people by talking about lift to drag ratios, NACA sections, end plates, twist, stall, Karman vortices and all the rest. So I won't - it's probably best to leave all that to designers and hydrodynamacists Instead I'll try to help those who want to know the basics; like should they have keels or boards on their multihull?

I'm not just a multihull designer; I'm also a (home) boatbuilder and owner. Currently I own two catamarans, one with daggerboards and one with keels. Over the last 30 years I have owned five cruising catamarans with keels, nine with daggerboards and one with one centerboard. Furthermore, I am one of the few designers who has fitted LAR keels and boards to the same hull (on Strider, Sagitta and Banshee) and then sailed them against each other.

As with everything to do with yacht design, leeway prevention is a complex subject. And it is not helped by the fact that boats are not just for sailing. You load them down and treat them as a floating cottage when you live aboard them. You motor them, you dry them out (either when the tide goes out or when stored ashore in a boatyard). And you have to pay for it all.

===========================

First a bit of simple theory

The main factor determining the efficiency of a foil is its "Aspect Ratio" (AR) or the ratio of it's depth to width. I think we all know that a high aspect ratio foil is more "efficient" than one with a low aspect ratio. A 3:1 AR is generally considered ideal for rigs but is usually too high for foils. In fact a 1:1 AR is OK for keels, although 2:1 or a bit more is better. In other words, a 1.5m deep daggerboard on a 10m boat will be about 750mm fore/aft (or more properly called it's "chord"). And it will be about 75mm thick, as the thickness of a foil should be about 8-10% of the chord.

Despite the fact that high AR foils are more efficient, there are a couple of reasons for limiting AR. As the AR increases the chord decreases and so the foil becomes thinner and clearly it is then also weaker. Unfortunately the foil loads have gone up (because the deeper the foil the further the Centre of Lateral Resistance (CLR) is from the bottom of the hull, so the lever has lengthened). So long, narrow foils are more prone to damage (one reason all those monohull keels have snapped off - a J800 lost one just recently).

In addition, the higher the AR the easier it is to stall the foil. When a foil stalls it stops "working", this is most obvious after tacking in a sloppy sea and you find that the boat won't sail properly for a couple of boat lengths. That is because the foil has stalled. In other words, you have to be sailing in flat water and be a very attentive helmsman to avoid stalling a high AR foil.

The lower the AR the bigger the foils area has to be to compensate for the reduced efficiency, however a lower AR is more tolerant of shape, surface roughness and angle of attack (which basically makes it easier to sail)

So how big should a foil be? Roughly 4% of the sail area is a good starting point. Some designers use very small boards. That may be OK in theory, which says that you sail in flat water at maximum speed, but in practice I find you need a bigger board to cope with waves and slow sailing, never mind tacking in a lumpy sea.

Whilst on the dangers of too much theory. Many race boats use sophisticated shapes and low drag sections. Don't use them unless, like top racing boats, you also dry sail your boat. Only the simplest shapes work with a rough surface (even new, clean antifouling is considered rough), these fancy shapes need a smooth, ie a mirror finish, to be of benefit.

I definitely don't like asymmetric foils. True they may give a bit more lift but only one can be used at a time, the other HAS to be raised. So you are carrying around the extra weight of a second board and box plus wasting time adjusting boards after each tack which all makes it not worth the very small efficiency gain.

Many people, especially cruisers, don't mind compromising on performance if it means an easier life, more load carrying and greater protection for the rudders and propellers. And that is why Low Aspect Ratio (LAR) keels are so popular. In much the same way as monohull sailors buy a long keel boat rather than one with a fin keel.

Unfortunately, using LAR keels results in a slower boat and more pitching. That is because to optimize speed you need a hull with buoyancy in the ends, not in the middle (technically you need a high Prismatic Coefficient - Cp). Clearly adding a LAR keel adds buoyancy in exactly the wrong place. Furthermore the midships buoyancy makes the boat pitch more as the hull is more "diamond-like". Having said that the buoyancy in the keel adds to total displacement, so you can carry more gear. And you can use the keel as a water tank/shower sump or even somewhere to fit an engine.

As I have just said, a lower AR means having a bigger foil and so clearly a LAR keel has to have much more area than a daggerboard. Thus the wetted surface area (WSA) is significantly increased, especially when sailing offwind compared to a daggerboarded boat with raised boards. And WSA is the prime source of drag at low speeds. So most designers draw a compromise keel which is smaller than strictly needed to balance the sail forces. But these forces must still balance and this can only be done by having a wider sheeting angle. Which in turn means a LAR boat cannot point as high as one with daggerboards.

So all in all boats with LAR keels are slower on all points of sail and in all conditions when compared to a daggerboarded boat. Say 5deg more leeway and 2deg less pointing. Remember it is hard to tell ones real leeway from looking back at the wake as in a seaway the top 2-3ft of water is blown sideways by the wind. So unless the keel is in deep still water you don't notice that you are drifting sideways until you look at the gps.

Further Design Considerations

Boards can be daggerboards (ie adjusted vertically) or centerboards (ie adjusted by rotating). Even though centre boards sometimes fit better into the accommodation layout and can pivot aft without damage when hitting the ground, daggerboards have proven far more popular. Probably because the centerboard pivot bolt often leaks, while it is very difficult to stop the water surging in the case with the board down, and it is easier for "Stuff" to get stuck in the gap between slot and board, thus jamming the board. A centerboard box/centerboard is probably heavier than using daggerboards. And finally it is harder to remove a centerboard for painting/maintenance.

Angled boards actually take up little interior room and can always be incorporated into accommodation dividers - the nav table bulkhead on a Banshee, the hanging locker on a Sagitta, against the hull side on a Merlin for example. More important is that they then don't bang around in a sloppy sea. Providing the board is angled at under 15deg to the vertical I haven't found any disadvantage in using angled boards. Nor have I noticed any difference between boards placed on the inside of the hull and those on the outside. Certainly there is no advantage in having vertical boards fitted on the hull centerline.

Don't use central boards though the bridgedeck. They simply don't work well. The Prout brothers discovered that in 1953 when they fitted a central board on the prototype Shearwater. By 1954 they had fitted boards in the hulls. The Stiletto catamaran started with a central daggerboard but owners quickly found that converting to ones in the hulls improved performance significantly.

The bottom of a LAR keel should be horizontal, otherwise you'll dry out at angle (OK I know that in many areas boats never dry out, but you want your boat level when in a boatyard) Even worse is a keel that is too short as then the boat can fall forward or aft when people move to bow/stern. Clearly dangerous and damaging to crew and boat.

Building Considerations

Boards are heavy, and more expensive than LAR keels, there's nothing one can do about that. To save weight you can make a short board, so that when down the top of the board is below deck level. Daggerboards can be profiled over their full length. But in that case you need to make the board first, and then make the box round the board. So you need to make expensive boards early on during the build.

The alternative is to profile only the below water portion, leaving the rest rectangular. This means the box is also rectangular, so the board can be made after the box. True, there is some extra turbulence when the board is half raised, but you can negate much of that by fitting a profiled cover plate on the outer side. Also I've found that there are less chance of leaks with a rectangular box and more important, weed, twigs etc are less likely to get between board and case and jam the board.

Many people suggest building a "crash box" to absorb any grounding shock. But be warned! I made one once years ago as an experiment on a dinghy. I ran aground and the board moved back into the crash box, exactly as planned. But then jammed - not part of the plan!! I had to capsize to free the board so I could raise it. Hardly practical on a cruising catamaran!

I haven't used a crash box since, relying instead on a very heavy laminate at the back of the box. My reasoning is that the tapered trailing edge of a board is far weaker than the box and so will always fail first. I proved that when hitting an unmarked reef off Nicaragua and we lost about 300mm x 100 mm of board, yet the box itself was undamaged.

Boards are generally made in timber or foam/glass. I prefer plywood over laminated timber as it is easier to profile. Foam boards are attractive in theory, but it is very hard to stop them warping and getting the correct shape without making a mould first is almost impossible. If you do make a mould you have to join the two halves, and remember boards don't just bend they also twist.

If you can, fit LAR keels as late as possible, this keeps the boat nearer the ground during building and saves a lot of ladder climbing.

What about in use?

Unlike boards, LAR keels are very much fit and forget. So there isn't much to say about keels, except to make sure you have a good sacrificial beaching strip and keep it maintained.

It is sensible to lift the lee daggerboard when reaching, as I have found that most breakages are of the lee board as it gets very loaded at speed. However lifting both boards in a big cross sea is not a good idea as that loads the rudders and that, apart from anything else, makes it heavier to steer, so have both boards half down.

Not being able to lift the lee board for half the time is one reason why I don't like using only one board in one hull. Doing so also means the board is much bigger so there are more local loads and of course it is harder to adjust. And it doesn't seem right to have the CLR so far offline. However if you do fit one board don't fit it in the galley hull as that is always heavier than the other hull.

Lifting the lee board to allow the boat to slip sideways is commonly thought a good idea. I'm not convinced. Tank test work has shown that having a deep lee hull actually helps prevent capsizing. That is because the windward hull lifts to a breaking sea, the sea goes under the bridgedeck and hits the lee hull. Because it is deep it is pushed sideways, which dissipates any overturning energy.

People often think you need a long keel (monohull or multihull) to steer straight "hands off". That simply isn't true. Good directional stability depends on the hull balance. A properly designed daggerboarded boat will sail as straight as a LAR keel one, and have the additional benefit of being quicker to tack and maneuver when necessary.

Finally, if you run aground, you can lift the boards to get off, but remain stuck with keels.

If you don't ever expect to race then keels are OK

If you think crosscut Dacron sails are good enough then keels are OK

If you trail your boat regularly fit dagger boards

If you have wheel steering and inboard engines and expect to dry out often fit keels

If you want the best performance then fit dagger boards, but be prepared to use them

• DESIGN TOPICS
• Daggerboards vs. Fixed Keels

Daggerboards or Mini Keels for Catamarans?

Comparing fixed keels and daggerboards. 

Fin keels, fixed keels, minikeels, skegs. Call them what you like, we know what you’re talking about. Choosing between fixed keels and daggerboards is probably one of the most debated options for a cruising boat and a difficult decision for a first time boat builder or purchaser. There’s no doubt high aspect ratio daggers give the optimum lift to windward and quicker tacking, but how significant is the downside of going to fixed keels, and are there significant disadvantages to living with daggerboards?

Fixed keels often get a bad rap. But it’s largely because there’s a lot of fixed keels out there that aren’t well designed. Poor section shapes and too shallow are the main problems.

Not all fixed keels are created equal, and because fixed keels by nature have a lower aspect ratio than a daggerboard, the foil section and planform (side view) selection are critical to minimise the tip loss - or the flow that runs under the keel and reduces the lift which provides windward ability. Obviously a relatively deep keel of moderate length will develop more lift than a long shallow keel, and this can be further improved by fitting an end plate to the base of the keel.

Construction Time and Cost

The dagger and dagger case combination probably take a little longer to manufacture and install and you will need to use carbon in the spar caps, but otherwise there is no significant difference in materials costs. 

However for daggerboards you do need to pay particular attention to the hull to dagger case bonding areas which need to be de-cored and strongly reinforced. Also there is the additional hardware involved in the controls required for daggerboards, and a little extra deck clutter.

Asymmetric boards? These are totally inappropriate on a cruising cat in my view. With asymmetric boards the windward boards should ideally be lifted each time you tack or it will be causing drag. This means each board needs to be larger to get the same lift. An unnecessary complication for a minimal difference in performance on a cruising boat.

Building Implications

The keels are at a disadvantage here in that the building space will require 500mm or more of roof height if they are attached to the hulls at the start of the project. This also means more climbing and more scaffolding to work on the boat. One option here is to fit the keels and glass tape them to the hulls after the boat is extracted from the building space and lifted to the required height.

Performance Comparison

The difference in windward performance between fixed keels and daggerboards on cruising cats varies depending on the conditions. In very light airs the daggerboards have a clear advantage, providing reduced wetted area and greater lift at angles of attack where a large percentage of the fixed keel’s area is likely to be suffering from flow separation. The boat with a fixed keel is likely to point nearly as high as one with dagger boards, but will lose ground though increased leeway.

As the wind strength increases the fixed keels will typically operate much more efficiently and from personal experience the difference in performance between two similar cats -one with efficient fixed keels, the other with daggers - is minimal in 10 knots or more of breeze, and negligible in 15 knots and above.

The boat with the fixed keel might be expected to suffer more friction drag downwind due to increased wetted area, but once again from personal experience this disadvantage is only clearly evident in light airs.

Other Factors

Most of the cruising boats I have designed have been fitted with fixed keels - even though an option for dagger boards is provided in the plans. This is mainly because of the advantage of being able to dry the boat out on the beach with the hull bottom easily accessible for cleaning, but also for the protection the keel provides to the rudder and sail drive leg.

These factors don’t rule out dagger boards - most boats will sit on the hull bottom and the rudder without suffering damage to the rudder stock - however I do recommend that the dagger board, if fitted has a restraining strap or line which can be released to prevent the board being raised above the height of the rudder tip or sail drive leg when sailing.

Keep in mind that with fixed keels you will have less draft than a boat sailing with the boards fully down so the chance of a grounding is increased with daggers, and because the fixed keel has an angled entry profile it is less subject to damage from a sudden collision. Dagger boards take very high loadings and cedar and glass construction is generally more forgiving than amateur composite construction.

Daggerboards can be noisy inside the case, both when raised or lowered. This problem can be minimised with soft bearings at the top and bottom inside the case (synthetic grass or carpet) but is not always easy to completely avoid.

On a boat any bigger than about ten or eleven metres the daggerboards are a big chunk of stuff and can be difficult to raise and remove from the boat for maintenance.

We sometimes hear the argument that fixed keels could cause the boat to trip and capsize sideways in a sea. In steep seas you're most likely to be running (possibly with a drogue) or laying to a sea anchor.

I've never heard of a cat tripping sideways over its' keels but please enlighten me if this has been the case.

Making the Decision

I generally recommend that daggerboards are a worthwhile investment if the owner has a preference for sailing to windward rather than motoring or waiting for a favourable breeze, and if the boat is going to be kept light enough to have a power to weight ratio that will do justice to the dagger board configuration. 

As a rough guide I would suggest that a 40’ cat which had a sailing weight of six tonnes or less would benefit from dagger boards, while a relatively heavy cruising cat would gain very little  benefit from the more efficient foils. On a 50’ cat the cut off point is probably about 10.5 to 11 tonnes.

Dagger boards should be at least partially raised when reaching at high speed, and the need to raise and lower the board at various times is an added complication that a lot of cruising people would prefer not to have.

Daggerboards do break from time to time. Until now I have not heard of a cat having a structural problem with fixed keels, except for one that was washed sideways across a coral reef and then mercilessly pounded by waves. In that case the keels may have provided some additional safety.

 Generally speaking cruising cats with fixed keels are probably easier to resell than cats with daggerboards. If you’re finding it difficult to make the decision and you're not interested in racing then it’s likely that fixed keels are right for you.

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Multihull Keels and Daggerboards

Fountaine Pajot BELIZE 43 resting on her keels, showing good bridge deck height

Uncovering the compromises of both underwater appendages and analyzing their disadvantages and merits.

Man has learned much from nature, and sailboats and their underwater appendages are one of the areas that we have applied what works and what doesn’t. As we all know, boats – as most things in life- are compromises and often we are prepared to make concessions in one area in order to gain an advantage in another. Not only should this brief discussion illustrate the basic virtues and drawbacks of daggerboards and mini keels on multihulls, but also point out their active and passive safety aspects.

Most multihulls in todays marketplace come in two varieties. By far the vast majority of the production cruising catamarans (about 90%) are keelboats and have low aspect ratio, unballasted keels. These well known French, Australian or S.African boat manufacturers market their boats for private ownership and the charter industry and make a great product. Without sounding too general, these boats have very spacious interiors and are perfectly adaptable for live aboard families or the charter trade. This multi million dollar charter industry, has an obvious influence on the requirements and design of their charter fleet, which further has a trickle down effect to other builders who also market their cats for private ownership. Design parameters for these charter cats are often centered around 2 week multiple family vacations in the steady Trade Winds and day sails between closely spaced islands of the Caribbean. The features of these keel catamarans obviously put less demand on pure sailing performance or extreme upwind sailing characteristics, but rather try to please by offering solid construction, live aboard comfort and simple and reliable handling characteristics.

The other type of multihull is the catamaran with articulating daggerboards or centerboards. Centerboard and daggerboard multihulls both share the same basic concept, except their deployment and storage relies on different principles. The daggerboard lives in a scabbard, or daggerboard trunk. It moves up and down, vs. a pivoting centerboard, which is raised and lowered around a massive pin. High aspect ratio daggerboards are by far the most efficient foils. They have none of the problems associated with centerboards, which when fully lowered are only braced by a small area on top. When going upwind in a hurry, loads on the trunk act as a giant lever, which constantly work to spread the trunk apart. This is the reason why it is recommended to operate foils as pairs in heavier conditions to divide the loads. Also the large area of the remaining centerboard slot creates a lot of unwanted turbulence making them unpopular for performance minded sailors. Lastly declining popularity of the centerboarders can also be lead back to the often large intrusion on the interior space the trunks create. Although the Gemini catamaran is a good example of a very popular and well thought out production catamaran, there are few other mass produced centerboarders around. It should be noted that one great advantage centerboards have vs. any other underbody configuration is that they theoretically retract when colliding with an object. In spite of this, most offshore or performance orientated sailors clearly favor daggerboards or low aspect ration keels.

Illustration A

Daggerboard catamarans have several advantages over their keel counterparts, some of which are well known and others that are more subtle and sometimes only recognized by people who have used them. Active safety aspects are advantages created by speed and the ability to retract underwater appendages.

I am a firm believer of “faster” rather than “slower” on ocean going performance multihulls. Many people might say, going fast is only for racers. But lets think about this. The ability to reduce exposure time through speed is invaluable for cruisers. If say on a transatlantic passage you can shave off 5 days you have already increased your safety factor, in some cases, by 25%. Not being a “sitting duck” is a nice thing indeed. By being able to have the choice, bad weather can be avoided, which can sometimes lead to a negative spiral of incidences. In general, especially on long passages, a daggerboard cat will have the edge on speed over her keel counterpart.

Lets face it, we are all in it for the fun of sailing as famed designer Francis L. Herrshoff said: “The fun of sailing is directly proportional to the speed of sailing”. Maybe this is the reason he designed Amaryllis, his revolutionary catamaran, which was later banned from racing. Generally speaking daggerboard catamarans will always be slightly faster than their keel equivalents. The speed advantage of most daggerboard catamarans vs. keel catamarans though is often exaggerated. On a typical day sail a well trimmed and tuned keel cat will only be slightly slower than a daggerboard cat.

Multihulls lack the feeling of being in the “groove”, which monohull sailors enjoy. Effortless high average speeds, acceleration and sustained high velocity surfs is something fast multihulls compensate with. It should be noted that anything (even a barn door) surfs in the right conditions. Even keel catamarans can surf at speeds up to 30 knots down large seas.

Upwind Advantages: Depending on sea state going upwind, daggerboard catamarans vs. their keel relatives will point up to 5 degrees higher and also experience 2-5 degrees less leeway, which isn’t much one would think. But in an uncomfortable 100 mile beat this ads up to being more than 17 miles closer to your destination! (Illustration B).

Illustration B

sin A=a/c (sin A) c =a (0.1736) * 100 = a a = 17.36 miles

Lets take a 45’ catamaran: the lift (to windward) generated by a daggerboard is almost twice that of a low aspect ratio keel and the drag with the board all the way down would be almost 20% less. The most recent generation cats with large beams and stately bridge deck houses benefit especially from high lift foils, since the windage of their projected area can ad up quickly. The same cats with keels usually suffer from excessive leeway and sideslip. Keel cat’s however, especially in a calm sea state, lessen this disadvantage as boat speed and flow over their keels increases.

Reaching and Running Deep: When running deep in fresh conditions the fixed could act as a brake, that one cannot disengage. Since they cannot be retracted, their volume and resistance slows the boat’s progress and in combination with the forward pressure of the sails forces the bows down. This is especially the case with catamarans that have long bridgedecks, heavy extremities and low volume- fine bows. The bigger the friction in the water, the bigger the pressure on the mast and the more the boat is burdened. Another neat trick is lifting the daggerboards, one can actually increase apparent wind by pointing up and induce leeway, crabbing faster to ones destination.

Tacking and Helm Feedback: Cruising catamarans are often mistaken to tack slowly and behave sluggishly to movements of the helm. This is certainly true for some heavy keel catamarans and much less so for ones equipped with boards. In complex seas, some of the heavier keel cat’s only option for a safe tack is back winding the jib. Monohulls with only one fin will always tack quicker than multihulls, just as foil equipped catamarans will be more responsive than keel multihulls. Modern hydraulic steering systems are easy to build and with most forward helm stations behind the main coachroof, pose sometimes the only alternative for the builder. Mechanical steering and daggerboards will give the ultimate feedback and fun at the helm…if one is driving at all, since usually the autopilot is engaged for longer legs.

Inclined foils on the Aeroyacht H42 performance catamaran built by Edel

Another advantage of daggerboards is the better maneuverability under one engine. If you loose one engine and retract the board on the hull which has no engine power, but leave the powered hull’s foil down, the boat will turn easier. Because of the retracted foil on the un-powered side there will be much less drag induced turning moment, the boat will be more balanced and the other sides deployed board will provide sufficient bite for “survival” steerage. Especially in high crosswind situations a catamaran with both boards down is much easier to maneuver than one with shallower keels. Usually harbor maneuvers under power are low speed operations, and this is where the high lift capacity of twin boards excel yet again and facilitate handling and precision steerage. Daggerboard cats also can motor a bit faster, since by retracting the foils they have less resistance.

Keel and daggerboard cats usually have less draft than keel monohulls, opening access to shallow anchorages. An advantage daggerboards have, are their gauging characteristics when entering shallow harbors or unknown territory. By lowering them, one actually creates a “safety depth”. When they touch bottom one still has the possibility of raising them, performing a U-turn and getting into deeper water. With fixed- non retractable keels, especially with a monohull, groundings or unplanned bottom encounters could end tragic. At least a monhull can attempt in heeling the boat to reduce draft and re float. This obviously is not an option on a keel cat. If you get stuck in the mud you are dedicated to await the next high tide to get you off. Crashing into a coral reef could be a different story altogether and only a haul out can asses and repair damage. Depending on their design, boards could be rotated or flipped, and even repaired underway. In general daggerboard cats also have less draft than keel multihulls allowing access to even more harbors and anchorages. They can be beached high up for repairs or inspections, increasing the window of exposure time between tides. I know, I once performed a 5 hour long emergency repair on our 43’ catamaran this way, saving 1000’s in yard bills and days of headaches.

It should be notes that keel catamarans however, can be beached just as easy as daggerboard cats. They can be left sitting, high and dry, completely safe on their keels, without having to worry about damaging the hulls or getting debris or sea life stuck into the vulnerable daggerboard trunks.

Bruno Nicoletti is an old friend and one of the most low key-expert sailors I know. He has logged more than 130,000 miles (geriatric miles as he calls them) on his 44’ daggerboard catamaran.. At a recent meeting with him in France we talked about his experiences of his record, double handed – one stop- Southern Ocean circumnavigation at age 63. The French Press compares Bruno to sailing legend Vito Dumas and has published his accounts in an article called: “The Impossible Route”. He explained, that in the Southern Ocean, in the most convoluted conditions he would simply raise both boards, lock the helm to windward and lay a-hull with no sails. “Brumas Patagonia” would safely slide down the steep faces of waves and minimally drift to leeward at about 1 mile per hour while he was either resting or reading. The water spoil of his side wards drift would help keep the edge off cresting waves and often prevent them from breaking (Illustration D) While it was blowing 70 knots and higher he felt very safe and in fact the world around him turned peaceful and quiet. His confidence in this system is impressive: I am currently helping him with sea trials on his new 47 footer for a yet another go at a High Latitude – geriatric- circumnavigation. This time he is planning to take his 78 year old brother and do it non stop !

Illustration D

It is not only in the Southern Ocean that one encounters steep, breaking waves. Major capes or the Gulf Stream are notorious for rough conditions where the ability to navigate safely becomes imperative. In these environments any proven and strongly built daggerboard cat would have a slight advantage by lifting her boards, although a well designed keel catamaran could get through unscathed. In extreme weather, and I am talking beyond Force 10, it is very important to enable a catamaran to side-slip rather than encouraging the possibility to trip, and maybe flip. A catamarans behavior in towering side waves is decisive and the possibility to lift underwater appendages is essential, especially if one has lost the ability to steer. The disadvantage of a keel catamaran in huge beam seas is more psychological than real, as these types of vessels typically also slip sideways. In survival conditions or emergencies, the use of parachute anchors, which force the boat into a certain attitude is often thought to be the only answer for most boats. In my mind this tactic is questionable since it puts enormous strains on the boat, is accident prone and renders one helpless when the odd rogue wave from a different direction smacks into the boat. It is better to manage survival conditions, by controlling and slowing the vessel with the use of drogues.

We have learned a great deal from aerospace industry and the trickle down effect to monohull keels. Multihull designers and builders greatly profit from the advanced research, that has been done in the field of NACA sections (National Advisory Committee for Aeronautics) and foil performance. Keels and daggerboards come in a variety of aspect ratios but most are based on low speed foils, which drag/lift characteristics have been optimized. To increase lift even further, some performance catamarans even utilize asymmetrical shaped daggerboards, shaped flat on the outside (leeward) and cambered on the (windward) inside. As they can only be used one at a time asymmetrical boards are somewhat limited in their adaptation for cruisers. (Illustration E)

Illustration E

Since multihulls do not heel, their underwater appendages are more effective in retaining positive flow than their monohull relatives.(this is also the reason why autopilots burn out less often and can be used in heavier conditions on catamarans) As the monohull heels, not only is the upper part partly blanketed by the underbody of the vessel but also flow is lost as the water slips past the angled keel to leeward. (Illustration F) This was especially prevalent on the early IOR monos, which had extremely beamy and shallow bilges and high prismatic coefficient center sections. To compensate for this loss of heel induced flow, monhulls need deep draft keels to make good progress to windward. The keel or daggerboard catamaran on the other hand can more efficiently create lift for the same keel plan view area, not only because it has two vs. one keel, but also through its minimal heel is able to keep its underwater appendages perpendicular in the water.

Illustration F

Usually catamaran daggerboards have a higher aspect ratio and are deeper than the equivalent length monohull, since they have the ability to retract them and therefore have no draft considerations. It is therefore not surprising to see that in wind speeds starting at around 10 knots a well designed and sailed daggerboard cat, will often outpoint and outpace a performance monohull. Even well sailed keel catamarans can often arrive earlier at an upwind destination compared to heavy monohulls. The couple of degrees they sacrifice in their ability to point to windward is often made up by their higher speed and VMG (Velocity Made Good). This performance difference increases proportionally to the wind speed and is very noticeable in F.4 conditions and beyond.

A well known fact and possibly the single biggest psychological deterrent of daggerboard cats is the vulnerability of the boards and trunk in collisions. The true Achilles heel are actually ill constructed and designed trunks, which cause flooding in an impact. This obviously is not the case with keels, which would deflect a minor obstacle, or in case of hitting a container or whale, simply break off. In the case of sacrificial keels, they would sheer leaving the hull completely intact.

Obviously the most critical area in daggerboard design is the construction of the daggerboard trunk. It is usually heavily reinforced with massive gussets, especially at its aft bottom end and extends from the bilge to the overhead. Typical forces on the trunk easily exceed the pressure of the wind on the sails. Dynamic forces of wave action and the shock loads of slamming into seas or solid objects must make this area one of the strongest and best engineered of the entire vessel. Usually the foils are located just aft of the main- mast bearing crossbeam and are somehow tied into this unit to profit from its stiffness. The more “left over” daggerboard remains in the scabbard in the fully down position, the better it is braced, so it is not surprising to see foils that are 18’ long for a 60’ boat. Builders who take their job seriously go through great lengths to make this key area as strong as possible. In a recent conversation with the manager of a reputable French production yard it was pointed out that the daggerboard trunk is engineered and constructed 7 times stronger than the composite board. In case of a violent impact, the foil, which has weak spots designed into it, will snap and leave the daggerboard trunk unscathed. It is a type of sacrificial impact philosophy or a safety fuse, just as it is used on sacrificial fixed keels. The careful engineering and experience necessary in building reliable daggerboard or keel cats stresses the importance of a production yard, which has consistently built them. This aspect should not be taken lightly if one ventures out into the open sea, even if it is only 20 miles offshore.

Often builders of keel cats ad daggerboards to their designs, with the objective to market increased performance and safety. This usually ends up in a compromise, since the hydrodynamic hull requirements of both types could differ substantially, let alone the experience of proper integration, engineering and construction might be lacking altogether. Building with keels does not require the experience, careful construction and engineering which are necessary with retractable foils.

Keels offer advantages, as they do not need to be operated at all. They do their work silently and its usually one less thing to go wrong. On the other hand people who have never sailed with daggerboards think their operation is complicated. In fact they are as easy to use as outhauls or travelers. In normal conditions with 2 people – one pumping the daggerbaords up haul line directly at the board- the other taking up the slack of the up haul, it literally takes 3 seconds to raise a 15’ daggerboard. Single-handed it is a 10 second affair involving 2-3 wraps of the up haul around a winch and 10 cranks. Most boards are slightly heavier than the water they displace and often only weigh 80 lbs. Dropping takes half a second, by simply opening the up haul sheet stopper and easing the foil down. Loads on the boards increase as the speed and pressure builds, so if one has the choice, these maneuvers are usually performed just before tacking. It is a misconception that the operation of foils will depend on the wind speed. It is rather the boat speed, in regards to sea state – which in turn limits progress – which dictates the proper positioning of the daggerboards.

Nothing is perfect and this analysis would be worthless without mentioning the pro’s and con’s of either underwater appendage. Daggerboards, their surrounding structures and systems are more expensive to build, so builders prefer to stay away from them given the choice. In some catamarans, especially smaller ones or ones that have the trunk in the center of the hull, the interior passage in the hulls can be crammed. Lastly it should be mentioned that incorrectly designed and constructed, daggerboards multihulls can be more of a detriment than virtue and in some cases can be extremely dangerous. If the trunks are not massively reinforced and in case of a violent collision one could flood one hull and cause a capsize. In this case one is better off with a well designed and constructed keel multihull than a mediocre or untested one with daggerboards.

Yet daggerboards give you choices, that keels deny you. It is like the new generation of cars with Tiptronic gearboxes, which offer you an automatic transmission with manual override. By physically selecting the proper gear, torque can be adjusted to suit the conditions. It’s the same with the daggerboard equipped catamaran. The boat can be fine tuned to optimize the level of efficiency of the vessels motion through the water. By being able adjust the foils, superior sailing characteristics result in speed and generally more fun on the water. Active safety aspects of reduced exposure time, better maneuverability and shallow draft provide significant benefits.

For safety reasons, most catamarans builders opt for fixed keels and completely separate the keels from the hulls, a feature which preserves and protects the water tightness of the boat in the event of violent impact. Furthermore, if such a situation arises, it makes them easier to repair or replace. Fixed keels require no manipulation, such as daggerboards and give perfect protection to drive shafts, propellers, rudder blades and hull bottoms in the event of grounding. Lastly the absence of a centreboard case means saving of space in the interior of the vessel and usually results in a larger living space.

Back to the birds. We all know the giant Albatross as an extreme example of a sorer that can glide for days in varying conditions, without having to move its wings. This Southern Ocean beast, who calls his home the most inhospitable area on our planet, is better adapted to handle extreme circumstances than any other flying animal. The Albatrosses’ wings are sophisticated in shape, but basically are articulating high aspect ratio foils very similar to daggerboards. Similar to the Falcons “high speed” wings, the Abatross can modify its wings aspect ratio to adjust to the breeze. The designers of the Polynesian multihulls, legendary Viking long ships and American Cargo Schooners understood this too. By adding movable leeway devices, center- or daggerboards, they made their boats more seaworthy and even sailors in the past preferred them over fixed keels.

Today we continue to strive to find the perfect compromise in our vessels to satisfy our most important requirements. We should be extremely thankful to the 1000’s of keel multihulls that have revolutionized the charter industry and many good boats have evolved from this trend. Reputable dagger board catamarans and well designed keel multihulls will continue to be the choice of future generations of serious offshore voyagers. Both offer their advantages and disadvantages and it is important to understand both in order to make the proper choice.

Gregor Tarjan, a trained naval architect and longtime multihull enthusiast is writer of numerous articles for Multihulls Magazine and various other trade publications. He has been involved in Dennis Conner’s “Stars and Sripes” 1984 Americas Cup Campaign, is the founder of Aeroyacht.He is also the co-editor and contributing author of the “Sailors Multihull Guide”, the book by Kevin Jeffrey.

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Sailboat Keel Types: A Complete Guide

A keel is a very important part of a sailboat, crucial to its stability and ability to sail upwind. This article will discuss the fundamentals of all keels down to the details of the best keel for your boat. We will answer questions including what it does, what it's made of, and even some problems that a keel can cause. By the end of this article, you will be an expert on all things keels!

Table of contents

What Is a Keel?

A keel is the robust underwater centerline of a boat, and often extends into a long, hydrodynamically shaped blade.. It can vary in size and shape depending on the make and model of the boat. But, generally, it will look very much like a fin. If you imagine the fin on the underside of a surfboard you will have a pretty good idea of what it looks like under the boat.

It is crucial to helping with steering and control. The word keel itself comes from Norse and Dutch roots. The word simply means a structural component of the boat. You may have heard the term keel-haul, where pirates would drag someone underneath the boat across its keel. This is pretty barbaric, but it shows just how long a keel has been an important part of the boat. From Vikings to pirates to modern sailboats it has always remained an important part of a sailboat.

What is a keel made of?

A keel will typically be made of whatever the rest of the hull is made of. If the boat is wooden, it will most likely have a wooden keel. If the boat is metal, the keel will be metal, and so on. Sometimes, particularly on fiberglass boats, the core of a keel will be reinforced with lead or a similar ballast while the outside is covered with fiberglass.

The keel needs to be strong enough to withstand a lot of pressure and strain. Traditionally Viking sailing boats would have a wooden keel with some metal plating on it. Casting metal was tedious so putting it on your boat was seen as a waste. Traditional wooden sailing boats, like you would imagine pirates sailing, would also have a wooden keel. It would be made from thick hardwood like oak and could also be metal plated.

Since it is used to control the direction it must brunt the force of the change of direction. If you imagine a boat turning sharply, there will be a lot of pressure on the side that is on the outside of the turn. The hull of your boat will stand up to this pressure easily, as it is very large and very strong. The keel must be strong enough to withstand this too. The keel also can drag on the ocean floor or the boat ramp as the boat is lowered into the water. For this reason, it needs to be strong enough to hold up to the weight and pressure of the boat too. If it were made of plastic it would break every time you brought the boat in and out of the water.

What does a keel do?

The keel is there primarily for stability and guidance. The keel provides all sorts of benefits to the boat. It improves the righting moment and controls the boat’s sideways movement. The keel will also typically hold the boat’s ballast. The ballast keeps the boat weighed down and helps prevent capsizing. The ballast is typically made of lead, sand, or water.

Keels can be fixed or moveable. Some keels can be removed completely or may just retract slightly so they aren’t damaged when the boat enters or exits the water. When a boat leans to one side, because it is turning or there is strong wind/waves, the keel provides the righting moment that keeps the boat from flipping. On larger boats, it is designed to be so heavy that ig will be able to recover a boat from almost any angle of heel. Without a keel, your boat may tip too far or roll completely. On bigger ships, this can be disastrous. In its ability to prevent this alone, the keel is one of the most important parts of the ship.

Does my sailboat need a keel?

Yes, you do need a keel. Pretty much all sailboats have a keel, with exceptions for multi-hulled and/or smaller boats.  

In the case of catamarans, the very design principles that lead to the dual-hull design render the keel obsolete. The stability introduced by the outrigged, dual-hulls replaces the necessary righting moment from the keel. Because almost all the structure of a catamaran is between the two hulls, unlike a monohull which builds out from and around its centerline, there is not a lot of weight pressing out to flip the boat. Related to this, since most catamarans have the length of their hulls pressing into the water, the steering force normally placed on a keel is distributed across the length of the two hulls, which additionally will carry their own ballast.

On smaller dinghies, a small swinging centerboard or daggerboard will suffice to play the role of a keel. The centerboards can be big enough to keep the boat flowing nicely through the water without the need for a large keel. Additionally, it is not a disaster for a small sailing or racing dinghy to capsize, as they are designed to do so and recover rather easily, so the ballast from the keel is also not terribly necessary. 

If you have a motorboat you wouldn’t need a keel, unless it is a very large container ship or military vessel. The reason being that they are outboard propelled. The leg provides enough stability on its own. This is only the case with full plane powerboats. Displacement (even semi-displacement) craft will still need a keel of sorts for stability purposes.

What are some downsides to having a longer keel?

If you have a long keel that doesn’t retract or detach, you may have some problems coming in or out of the water. The keel extends far below the bottom of the boat, so if you are bringing your boat up or down a boat ramp you may find that it scrapes on the bottom. If you are not careful, you may damage the keel rather badly.

Since the keel is made of metal, wood, or fiberglass it can bear the brunt of the weight quite well. If you are putting your boat in the water and cannot retract the keel, it is a good idea to go as far into the water as possible before taking your boat off its trailer. The deeper you are in the water when the boat is released the better.

Are there any nautical traditions about the keel of the boat?

The keel is interestingly very important when it comes to boat or shipbuilding.

Traditionally, the keel is one of the first parts of the ship to be made, as the rest of the ship must sometimes be built around it. This tradition is called “laying the keel,” and is a momentous occasion. It is essentially the boat’s birthday. The boat’s age is dated from this moment, and there is also typically a celebration of sorts. This goes back to the days of seafaring exploration. The only day more important in a boat’s life is the day it is finally launched.

Can other types of boats have keels?

Yes! Many other types of boats have keels, not just sailboats. A good example would be a big shipping trawler. These trawlers are very large and need all the help they can get to stay balanced. Because of this, they often have what’s called a bar keel. This is a large rectangular piece of metal that runs along the bottom of the boat’s hull. It is very thick and heavy. The idea is that it gives the boat some more directional control when steering.

Furthermore, it helps keep the trawler balanced when out at sea in rough conditions. The extra weight keeps the boat’s center of gravity as low as possible. This makes tipping the boat almost impossible. It does slow it down a bit, but that is a small price to pay for increased safety.

Huge cargo ships also have a keel, though it is different from a bar. Their keel is known as a plate keel. It is essentially another layer of the boat under the hull. Its only purpose is added weight and protection. A plate keel runs along the centreline of the bottom plate of the ship so the weight is all concentrated in the lowest place possible. This kind of keel works similarly to how the spine of a person does. It keeps your back strong and as straight as possible.

How important is it to keep my keel clean?

It is very important to keep your keel clean, just as it is important to keep the rest of your hull clean.

For any boat kept on the water rather than hauled out every day, there is always the need to clean the hulls and keels of any barnacles and other sea growth. Barnacles not only affect your performance, but can, in the long run, greatly increase your maintenance costs if not regularly addressed. 

To do so, you have to do what is known as scraping. Scraping is the process of physically scraping off all the barnacles and other sea life that has attached itself to the underside of your boat. Many marinas offer this service, but you can do it on your own with a basic plastic paint scraper and a wetsuit. When you do this, it is key to get all the way down to the bottom of the keel and all across the hull. If you don’t scrape it off, it can start to erode your boat away over time. It can also slow you down.The barnacles and other marine life create a very rough bottom. This creates more friction and will reduce your speed more and more the worse it gets. 

It is important to check with your port authority before you start scraping. Scraping is not allowed in some places as you may introduce invasive species to the area. It depends where you have been more than where you are. If you sailed from New York to Chicago, you will be fine. If you sailed from Cuba to New York, probably not so much.

How to maintain a sailboat keel

As mentioned above, it is important to scrape your keel from time to time. While racing boats will actually do this before every day at an event, it is at least a good idea for you to do this a couple of times a season. A great time to do this is when you plan on applying that season’s bottom paint, though anytime you plan to go on your boat is a good excuse to maintain!

You may want to cut off any of the kelp and seaweed that wraps itself around the keel. This is more likely to happen if you have a fin keel. If you do find that there is a lot of kelp and seaweed wrapped around it, you will want to buy yourself a kelp cutter. Unfortunately, the only way to cut the kelp off without taking the boat out of the water is to dive in and do it yourself. It is a good idea to do this in shallow-ish water with the proper flags displayed to inform other boaters that there is someone in the water. Swimming around under your boat, even when it isn’t moving, can be dangerous.

What do I do if my keel breaks at sea?

It is very rare for keels to just break off. It is even rarer at sea. After all, what is going to break it off? The only way a keel will break off ordinarily is if you run aground.

If you should accidentally make your way into shallow waters and break your keel off it is a good idea to set sail for home. You will manage well enough in the short term but will struggle over time. You are far more likely to capsize without the keel keeping you balanced.

If you have a detachable keel it is a good idea to keep a replacement. If one breaks off, you can just install the spare one. This isn’t the easiest thing to do at sea in rough conditions, but it is possible. Make a judgment call using your common sense whether it is worth the risk or not.

Another reason your keel might break or come loose is if the keel bolts come out. These bolts are what holds the keel in place. If you happen to have a keel held on by bolts, then doing proper maintenance is even more important. If the bolts come loose, the keel can come loose.

Since the keel is typically welded on to the boat’s hull the chances of it coming off completely are slim to none. Most often, running aground on a sandbar or anything short of an incredibly rocky bottom in heavy weather will crack off a piece or severely bend the keel, which requires a major repair. If you do notice that the keel is loose, you are better off taking it back to the marina. The bolts may not come off without using some machinery, meaning you might have to take your boat out of the water. If your keel starts to rust, you may need to speak to a professional.

What are the different keel types?

Now you know what a keel is, what it does, why it is important, and how to care for one it is time to learn about the specific types of keels. Big trawlers and cargo ships have bar or plate keels, but sailboats do not. Here are the 6 different types of keels typically found on sailboats and their purposes:

The full keel is one of the most common types of the keel that you are likely to see on a sailboat. A full keel runs from end to end of the boat lengthways. A full keel, as the name implies, runs almost the entire length of the boat. At a minimum, it must run 50% of the length of the boat. A full keel is one of the most stable keel types, which is why it is so common. Full keels are also safer should you run aground. If a boat with a full keel should come ashore, it will cut its way through the sand and eventually land on its side. Whether you are grounding your boat intentionally or not, your boat will have far better odds of surviving the ordeal with a full keel.

A fin keel is similar to a full keel, just shorter. There may be one or two fin keels along the length of the boat hull. A fin keel is defined by being less than 50% the length of the boat. The fin keel works almost entirely the same way that a shark's fin does. When you wish to turn, the keel provides the resistive force that keeps you turning. This means that it essentially acts as your tires going into a turn. Whereas a full keel is essentially just a long fin, a fin keel has very different benefits. A full keel is more stable and safer overall. A fin keel is sleeker, smaller, and most importantly makes you faster. Most racing sailboats have fin keels.

A bulbed keel is very similar to a fin keel. In fact, it is possible to make a bulb keel by shaving off part of a fin keel and attaching a bulb. Once the keel has been made substantially shorter, the bulb is fitted. The bulb is shaped similarly to how a torpedo would be on a submarine. This keel works the same as a fin keel does, offering a slightly more stability without sacrificing speed. The biggest difference between a bulb and a fin keel (besides shape and length) is where they are used. Bulb keels are most commonly used in places with very shallow waters and lots of rock/shale/coral outcrops. Somewhere like the Caribbean would be the perfect place for a bulb keel. The rounded bulb bounces off the rocks and is less likely to break off. It just isn’t going to be as quick as if you used a fin keel.

The wing keel is another alternative to your standard fin keel. Just like the bulb keel, a wing keel is an extension to the standard fin keel with an extra fitting at the bottom. A wing keel is far more streamlined than a bulbed one, at the expense of being more susceptible to breaking. A wing keel looks very similar to the tail of an airplane. It works the same way, too. The water can pass by either side of the wings, allowing you to adjust your course easily. But, a wing keel does have one major problem. If you do run aground, digging out a wing keel can be very difficult. Whereas digging out a standard fin is as simple as scraping sand away from the sides of it, a wing keel must be dug out completely. The wings act like little shovels and wedge themselves into the sand. These are generally limited to higher performance racing classes.

Centerboard Keel

A centerboard keel works similarly to a fin keel but it can retract slightly. It works by having a dagger that folds out downwards. When you are sailing, the dagger protrudes outwards and offers you all the stability and balance of a fin keel. When you are in shallow water, the dagger can be retracted upwards, essentially shortening the keel temporarily. This should be done when you are sailing in shallow waters or removing the boat from the water entirely using a boat ramp. Some centerboards work on a loose hinge. When the boat is sailing along, the dagger is out and the fin works as normal. If you should bump into something though, like some shallow rocks, the hinge would push the daggerboard back inside. This stops the keel from breaking, instead, it just moves out the way. This only works if you are only just deep enough. If you are in very shallow water you would just break the centerboard off.

Canting Keel

A canting keel also works on a hinge. Instead of working end to end, it works port to starboard. When the boat turns a corner, the canting keel swings from side to side. This allows the boat to maximize its balance and speed. Eventually, this will become the norm in racing. But at the moment it is still quite experimental. The biggest downside is that the hinge works on hydraulics, and hydraulics can fail. If they should fail at sea there is very little you can do to repair them. Once they have perfected these canting keels, they will move first into the racing classes and high performance boats, then to all new cruising boats as boatbuilders improve the technology. .

Hopefully, you now have a good idea about what a sailboat keel is,how it works, why it is so important, and, of course, all the different types. Chances are, when you buy a sailboat , the keel it has is going to be at the bottom of your list of priorities. That being said, if you are planning on sailing somewhere in particular, it is a good idea to think about what keel type you are using. Replacing them doesn’t have to be expensive, but you can go a long way to saving yourself that money either way by being prepared for your home waters!

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Daniel Wade

I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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Do Catamarans Have Keels? Uncovering the Truth

Have you ever wondered what makes a catamaran so different from other types of boats? You may have noticed that a catamaran appears to lack the long, central keel that other boats have.

So, do catamarans have keels? In this article, we’ll go beyond the surface level to uncover the truth about catamarans and keels.

We’ll look at what a catamaran is, what a keel is, and why catamarans don’t have keels.

We’ll explore the advantages and disadvantages of not having a keel, as well as the different types of catamarans and their popular uses.

By the end of this article, you’ll have a better understanding of why catamarans are the way they are.

Table of Contents

Short Answer

Catamarans typically do not have keels.

Instead, they have two hulls, or parallel hulls, connected by a frame.

This design reduces drag and increases stability, allowing catamarans to move quickly and remain upright in rough seas .

Keels are typically seen on monohull boats, which are boats with a single hull.

What is a Catamaran?

A catamaran is a type of boat that is made up of two hulls, or parts, that are connected by crossbeams and struts.

Compared to single-hulled boats, catamarans are more stable and provide greater stability due to the weight being distributed over a larger surface area.

This design also allows catamarans to be more easily maneuvered and to move through shallow waters.

As a result, they are often used for recreational activities such as fishing and sailing.

Catamarans also typically lack a keel, which is a fin-like structure that is found on the bottom of a single-hulled boat that helps provide stability and also helps protect the boat from waves or other environmental forces.

Instead, catamarans rely on their two hulls to provide stability and protection.

What is a Keel?

When it comes to boats, the keel is perhaps one of the most important components.

A keel is a long, heavy, and usually flat piece of metal, wood, or fiberglass that is attached to the hull of a boat and extends below the surface of the water.

This structure serves several important functions, including providing stability, generating lift, and helping to steer the boat.

The keel also serves as a counterweight to the wind and wave forces that push against the hull of the boat.

It also helps to disperse the weight of the boat, allowing it to remain level in the water.

While a keel is present on most traditional boats, it is not present on catamarans.

Why Don’t Catamarans Have Keels?

When it comes to boats, the keel is an integral part of the design.

It provides stability and helps the boat to move through the water.

So why dont catamarans have keels? The simple answer is that they dont need them.

Catamarans are designed with two hulls that are connected by crossbeams and struts.

This design helps to provide greater stability by distributing the weight of the boat over a larger surface area.

The lack of a keel also allows the catamaran to be more easily maneuvered and to move through shallow waters.

This design also allows catamarans to be more fuel efficient than traditional single-hulled boats, as the two hulls help to reduce drag.

Additionally, the lack of a keel reduces the overall weight of the boat, making it easier to transport and launch.

The design of the catamaran also helps to make it more stable in rough seas, making it an ideal choice for recreational activities such as fishing and sailing.

The design of the catamaran also allows it to be more responsive to the waves and wind than traditional single-hulled boats, as the two hulls move independently and respond to the conditions more quickly.

This makes them ideal for sailing and other activities, as they are able to turn faster and more accurately than single-hulled boats.

In short, the lack of a keel on catamarans is one of the main advantages of the design.

The two hulls provide greater stability and maneuverability, and the overall lighter weight of the boat makes it easier to transport and launch.

The lack of a keel also makes the catamaran more fuel efficient and responsive to the waves and wind.

As a result, catamarans are often used in recreational activities such as fishing and sailing.

Advantages of Not Having a Keel

The absence of a keel on catamarans can be advantageous in many ways.

First, it provides greater stability than traditional single-hulled boats.

Because the weight of the boat is distributed over a larger surface area, the catamaran’s two hulls are able to withstand more force from waves and other conditions.

This makes them an ideal choice for recreational activities, such as fishing and sailing, as they are able to remain steady in choppy waters.

Furthermore, the lack of a keel allows catamarans to be more maneuverable than single-hulled boats.

Without the additional weight of a keel, catamarans can turn more quickly and easily, making them ideal for racing and navigating through tight spaces.

Additionally, the absence of a keel allows catamarans to move through shallow waters, which is beneficial for exploring areas that would be inaccessible to single-hulled boats.

Lastly, the absence of a keel also contributes to the overall design of the catamaran, as the two hulls are connected by crossbeams and struts.

This design helps to increase stability and reduce rolling.

Additionally, it can provide greater visibility, as the two hulls can extend farther out from the center of the boat, providing a better view of the surroundings.

Disadvantages of Not Having a Keel

The lack of a keel on catamarans can be both a blessing and a curse.

While having two hulls instead of one provides greater stability, this also means that the catamaran is more vulnerable to strong winds and choppy waters.

Without the keel acting as a counterbalance, the catamaran can be more easily pushed off course.

This is especially true if the boat is not well-balanced, as the weight distribution is less evenly distributed without a keel.

Additionally, a keel can provide additional lift to the boat, which can help to increase speed and maneuverability.

Without a keel, catamarans will often be slower and less responsive than a traditional single-hulled boat.

Finally, the lack of a keel also means that the catamaran is more vulnerable to capsizing, as the boat is more top-heavy without the keel acting as a counterbalance.

Different Types of Catamarans

When it comes to catamarans, there are several types that have different designs and features.

The most common type of catamaran is the pontoon catamaran, which is composed of two hulls that are connected with beams and struts.

This type of catamaran is often used for recreational activities, such as fishing and sailing, because of its stability and ability to maneuver in shallow waters.

Another type of catamaran is the trimaran, which is composed of three hulls connected by beams and struts.

The trimaran is designed to provide more stability than the pontoon catamaran, and is often used for racing and long-distance sailing.

The third type of catamaran is the hydrofoil catamaran, which is composed of two hulls that are connected with beams and struts.

This type of catamaran is designed to reduce drag and increase speed by using hydrofoils to lift the hulls out of the water.

This type of catamaran is often used in high speed boat racing and can reach speeds of up to 40 knots.

Finally, there is the semi-submersible catamaran, which is designed to be partially submerged in water.

This type of catamaran is often used for research and exploration, and can be used to explore shallow waters where traditional boats are not able to go.

No matter the type of catamaran, they all have one thing in common: they do not have a keel. Instead, they are designed with two or more hulls that are connected by crossbeams and struts. This design helps to provide greater stability and allows catamarans to be more easily maneuvered in shallow waters. As a result, catamarans are often used in recreational activities, such as fishing and sailing.

Popular Uses for Catamarans

Catamarans are popularly used in recreational activities such as sailing, fishing, and even racing.

Their unique design allows them to maneuver easily in shallow waters, which makes them ideal for these activities.

Additionally, catamarans are often used for chartering and cruising, as they are more stable than traditional single-hulled boats.

The lack of a keel also allows catamarans to move more quickly through the water.

Furthermore, the spacious living area provided by the two hulls makes catamarans an ideal choice for extended trips and vacations.

Catamarans are also used in commercial activities such as ferrying, transport, and research.

Their stability makes them perfect for transporting cargo and passengers over long distances.

Additionally, the two hulls provide more room for researchers to conduct experiments and surveys.

The shallow draft of catamarans also allows them to navigate shallow waters, which makes them ideal for research purposes.

Lastly, catamarans are also used in rescue and emergency operations, as their stability makes them perfect for difficult and dangerous conditions.

Final Thoughts

In conclusion, catamarans are unique boats that are designed without a keel for added stability and maneuverability.

While they do not have the same advantages as a single-hulled boat with a keel, they are popularly used for recreational activities such as fishing and sailing.

With the knowledge of why catamarans do not have keels, you can now confidently choose the right boat for your next adventure.

James Frami

At the age of 15, he and four other friends from his neighborhood constructed their first boat. He has been sailing for almost 30 years and has a wealth of knowledge that he wants to share with others.

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Catamaran Sailing – What’s the Difference?

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What is a Catamaran?

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Performance Study of Daggerboards Versus Keels

Story by Phillip Berman / August 17, 2018

By: Phillip Berman, published with editor’s permission from Boating NZ and  Blue Water Sailing

In my forty-five year career in the catamaran industry there’s been a relentless debate on the virtues and vices of daggerboards versus fixed keels. This debate has, however, mostly been waged without “hard numbers” from which to compare performance differences. As we have had requests at Balance Catamarans for both keels and daggerboards, Anton Du Toit (my design partner) and I felt we should conduct a study, the results of which follow.

When we first set out to design and construct the Balance 526 we were aiming for cruising couples who wanted more performance and quality than they could find in mass production cats, but also more interior space, payload capacity and ease of use and maintenance than consumers focusing primarily on speed. Our intent was to find the balance – not to create the “lightest and fastest 52” in the world, or the “largest 52,” but a catamaran that could sail swiftly on all points of sail, carry significant levels of payload, yet still be gracious to live on. We also wanted her to be pleasing to the eye.

Our focus at Balance brings us an interesting range of buyers, some of whom are more focused on strength, space, safety and comfort rather than all out speed (cruiser types), others who are more speed focused, less value oriented, and prepared to give up comfort, ease of operation and payload capacity to go a bit faster (racer types). The later sorts of buyers are mostly what I affectionately call “spreadsheet guys.” (Full disclosure: I am not a spreadsheet guy. I am far more focused on how a boat lives, how tough she is, what she can carry, and how simple she is to sail and maintain without a professional crew.)

As we have gone along a few of our customers have asked if we would create the 526 with performance keels rather than daggerboards. They felt that the advantages of keels trumped the performance advantages of boards. We were happy to comply, so Anton set about to design high performance keels for the 526. (Note: On our 451, we only offer her with dual daggerboards and two shallow permanent fixed minikeels. On all other Balance designs it remains customer choice which configuration they wish to have.)

What we were not prepared to do was tell 526 buyers how much faster or slower the two different configurations would be. We felt it best to heed Lord Bryon’s advice to evade “kant and hyperbole” (the language of the day at boat shows!) so we hired the Wolfson Unit for Marine Technology and Industrial Aerodynamics at the University of Southampton to conduct comparative studies of the two configurations on identical 526 models. When you are comparing identical products with just two different variables it seemed a worthwhile study to undertake and share with our customers. It also becomes, to some extent, a  worthwhile study for anyone considering a new or used catamaran purchase who is curious how the two different configurations impact performance.

While Anton and I believe these studies can be used by consumers to compare the relative performance differences between boards and keels, it is important to note that the 526 is a very light, narrowhulled epoxy performance cat and the keels we install are considerably finer, deeper and more carefullyshaped than those found on mass production designs. Additionally, we conducted the study with the daggerboards in the fully down position on all points of sail to reduce the studies complexity. The daggerboarded 526 would be marginally faster than the study indicates off- the-wind with boards raised due to a further reduction of wetted surface.

The disparity between keels and boards on a mass-production cat compared to a Balance or any other performance cat would be exaggerated considerably compared to the study that follows. I would note that we erred on the side of caution in setting our lightship weight for this study at 12.5 kg. We have carefully lode cell weighed our 5th boat and the actual lightship weight is 12,215 kg, or 26,930 pounds for the keeled 526 and 12,261 kg, or 27,030 pounds for the daggerboarded 526. Our lightship weight could be lower for customers prepared to put their boats on a diet, or sacrifice quality in several areas, but we have found that they want as much cabinetry as possible, folding tables, glass salon windows, Corian counter tops, and high-end flooring inside and out, etc. Spreadsheet guys miss the mark on this subject constantly in my experience. They also wrongly compare boats based on length, rather than the interior volume of the hulls and bridge – what I call the sum total of fiberglass parts. Regardless, the polars closely mimic the high performance our yachts have proven in real life cruising, fully laden, so this gives us great confidence in the studies accuracy.

Performance, of course, is not the be all and end all, so it is important to examine the advantages and disadvantages of boards versus keels beyond speed. They are as follows:

Advantages to Keels:

• No moving parts. One less thing to operate or break.
• If you ground the boat you hit the keels and they are easily repaired and at a low cost generally.
• You can chock the boat more easily on the hard and it is easier to beach in some circumstances.
• They cost less to fabricate.
• You get more room amidships for additional cabinetry.
• The keels add a bit of buoyancy. On a 526 about 1,600 pounds as our keels are large and mostly hollow inside.
• Daggerboards are typically a bit heavier. On the 526 each board and trunk weigh about 50 pounds more.
• Poorly designed boards and trunks can allow the boards to rattle when they are not under load. Keels do not rattle.

Advantages to Daggerboards:

• Boarded cats point higher and side-slip less as the study shows. I have noted that on keeled production cats you can “stick them up into the wind” but they tend to crab horribly when pinched, as such that you must crack off considerably to reduce leeway and sustain momentum. On most of the sea trials I conduct on production cats we “close reach” to windward on sea trials. This is less the case on deep, finely shaped performance catamaran keels.
• The draft on most keeled catamarans is deeper than the draft on daggerboarded cats. Our 526 keeled version draws about 12 inches more than the daggerboarded version. On daggerboarded cats the rudder tip usually represents her deepest draft. It is important to note that some cats carry very stubby keels to sustain shallower draft, but the shallower the keel the less well she performs when sailing close to the wind. This is important to keep in mind if you are comparing performance on fixed keeled production cats.
• Off the wind with the boards raised to 1/4 there is less drag and the boat steers and sails faster and more playfully.
• The daggerboarded cat is a bit faster and makes less leeway on nearly all points of sail as the study shows in the majority of wind conditions.
• An equally efficient set of keels have much more wetted surface than daggerboards, almost 4 times more. This is the case on our 526 keels.
• Daggerboards set properly can assist in preventing a cat from a “tripping capsize” in very high winds with large breaking cross seas. Both boards can be fully raised, or only the leeward board raised, so the boat can side-slip easily.
•  Daggerboarded cats tend to have a bit higher resale value due to the fact that so few are produced in mass production. A buyer that wants boards will only focus on catamarans that have them.

Shifting our focus now to the performance data generated by Wolfson Unit. Their analysis returned the predicted boat speed and leeway angle for the Balance 526 with a keel design and daggerboard design for all combinations of true wind speed from 4 to 25 knots and true wind angles from 40 to 180 degrees. We can begin comparing these two configurations by directly comparing the speed and leeway at major points of sail, specifically beating, close, beam and broad reaching.

While beating the two designs are predicted to perform as follows: To summarize the upwind comparison, the daggerboard design is, on average, expected to sail 1.5 knots faster and 1.75 degrees higher. While close reaching the daggerboard design has less of an advantage than when beating, as can be seen from Table 2:

While close reaching the daggerboard design is expected to sail 0.5 knots faster and 0.75 degrees higher.

As the true wind angle approaches 90° for a beam reach, the keel and daggerboards become more closely matched.

In the beam reaching comparison the daggerboard design will sail slightly higher with a leeway advantage of about 0.25 degrees but it’s speed advantage in 5 knots TWS of 0.3 knots will fade to a 0.5 knot deficit in 16 knots TWS. At this point of sail the two designs are considered to have equal performance as the differences in leeway and boat speed are negligible.

Finally, while broad reaching the following speeds and leeway’s are expected.

In summary, when broad reaching the daggerboard design regains a slight advantage, as it maintains an additional 0.5 knots of boat speed. Leeway differences are again negligible.

Considering the above analyses, it can be seen that the daggerboard design will typically not only outperform the keel design but also out point it, make less leeway close to the wind, therefore giving the daggerboard design a substantial advantage when racing, or for performance focused sailors.

This data gives a fair comparison of the two designs at specific true wind speeds and angles but in order to fully understand the performance trends and enable better predictions between them, one must consider the entire range of wind conditions and all points of sail. This is best done with the use of speed and leeway deltas, where the differences between the two designs are calculated and analyzed.

The following two figures display the average speed and average leeway deltas. The calculation process to determine the deltas is chosen such that a positive value for the delta indicates an advantage for the daggerboard design, and a negative value favors the keel design. For example, a speed delta of +2 knots and a leeway delta of -1 degrees means that the daggerboard design is 2 knots faster than the keel design under the same conditions but would sail 1 degree lower than the keel design.

Counter to this, while still on a beam reach but when moving from a low wind condition to a high wind condition, the keel design begins to perform better. This is now taken from the green line (14 to 25 knot TWS range) and gives a -0.6 knot reading. Therefore the daggerboard design is now expected to be about 0.6 knots slower than the keel design under the new, higher TWS conditions.

Figure 2 is used in the same manner as Figure 1 but shows the leeway angle of each design rather than boat speed. Focusing again on a beam reaching condition, the leeway deltas indicate that the daggerboard will always out point the keel design as all three lines (TWS from 4 to 25 knots) indicate. positive values of 0.3, 0.35, and 0.1 degrees at 90 degrees TWA. Overall, Figure 2 shows that the daggerboard design has a significant gain in leeway over the keel design at all wind speeds and angles. This reaches a maximum when beating (TWA ±40-45 degrees) of 2 degrees, and declines to zero when running (TWA ±180 degrees).

With respect to the average boat speed deltas, Figure 1 shows that the daggerboard maintains a higher boat speed when sailing in light and medium winds (red and blue lines in Figure 1). In stronger conditions (green line) the daggerboards yield better boat speed when beating but the keel surpasses this between TWA of 60 to 145 degrees. Keeping in mind that the study was conducted with the daggerboards fully down at all times, in reality, the daggerboards will be raised in the 60 to 145 TWA range. As such the study slightly underestimates the speed of the daggerboard design over this TWA range.

Overall the daggerboard outperforms the keel in both boat speed and leeway in the vast majority of sailing conditions and is thus considered to be the better design choice if achieving ultimate performance is the key criteria. It should be noted that this study is specific to the Balance 526, but corresponding trends can be expected in performance cats of similar size and design.

In the end, and it is a point I cannot stress enough to any boat purchaser, all boats are sets of compromises and trade-offs, and so too with features – helm designs, sheeting systems, rig layouts, bimini designs, bed designs and locations, baths, engine placement, etc. Because I have been deeply involved in brokerage catamaran sales much of my life I recognize there is no one right or wrong boat, certainly no perfect boat, only a boat that happens to be a better fit for a particular sailor and his or her budget, cruising agenda and specific aesthetic proclivities.

At least now we can say that if someone wants a 526 with keels, here is how she will perform compared to a boarded version. It is then up to the buyer to decide which configuration is the most appealing to them. I will say that, based on the five 526 we have sailing today, with over 60,000 miles of sailing behind them, those owners with keels seem quite happy, just as those with boards.

Alright spreadsheet guys, here’s your numbers to mess with!

Phil Berman is a former Hobie Cat World Champion and the founder of The Multihull Company, a global catamaran yacht brokerage firm. He is also the owner of Balance Catamarans, a boutique brand of high-end performance voyaging catamarans. He can be reached at [email protected] .

About Phillip Berman

• Are you a Spreadsheet Guy?
• Balance Catamarans is Born: A Bold Move in a Challenging Market
• Can a catamaran really sail upwind?
• Catamaran Depreciation
• Catamaran Vs Monohull
• Daggerboards vs. Keels
• Lessons Learned From A Free Spirit
• Placing a Boat Into Bare Boat Charter
• Post Survey Negotiations
• Saildrives or Straight Shafts? Which is Best For Me?
• Seller's Guide To Yacht Sales
• The 14 Biggest Mistakes When Purchasing a Used Catamaran and How to Avoid Them
• The 14 Biggest Mistakes When Purchasing a Used Cat…and How to Avoid Them Part Two
• The Perils of Internet Catamaran Shopping
• The Ten Commandments of Buying a Catamaran

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Catamaran basics The daggerboards: understanding and adjusting them

Having a catamaran with daggerboards means enjoying better pointing ability than an equivalent model equipped with fixed stub keels, which are inevitably shorter. It means that you can also optimize drag, speed and even safety. Partially integrated, with foils...an inventory of the daggerboards on our boats and how to use these appendages.

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1) All the Catanas are equipped with daggerboards. They are very long, and held structurally in their cases by the whole height of the hulls. Simple and strong, but beware of the significant windage in the raised position.

2) The latest Catana models are equipped with curved daggerboards. On the 59, the foil effect is worth 500kg at a speed of 15 knots.

3) The latest Outremers have adopted shorter structural cases, to reduce the size of the daggerboards. Less windage in the raised position and less weight, but the construction is more complex…

4) Numerous trimarans are also equipped with daggerboards/centerboards. They can be central and integrated into the accommodation, as aboard this Dash 750.

5) Other trimarans, such as the Tricat 25, are equipped with centerboards integrated into the floats.

6) Builders such as Outremer provide stopper knots for the daggerboard control lines; a good way to judge the position when the daggerboard is not visible.

7) Once the daggerboard is out of its case, it is easier to judge: the lifelines are an excellent adjustment indicator!

8) To windward in light weather, the daggerboards are fully lowered, to take advantage of maximum 'grip' on the water.

9) When the speed increases, it is worthwhile raising the windward board to optimize drag. Note: a daggerboard which moves is no use. Therefore we raise it!

10) But for safety, it is preferable to raise the leeward appendage: in the case of a strong gust, the risk of the boat ‘tripping up’ is thus reduced. The compromise could be to raise both the daggerboards by half... It’s up to you to judge!

11) Downwind, the daggerboards are no longer useful, especially when the boat exceeds 10 knots... Keeping one third of the surface can however help the helmsman or the autopilot to steer a straighter course.

12) Heavy weather? Raise them completely so the hulls slide. On the other hand, with big seas from behind, (just like downwind in more manageable weather) it may be useful to keep a little daggerboard lowered to avoid yawing.

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What is a Boat Keel? & What Does It Do? – Detailed Explanation

Written by J. Harvey / Fact checked by S. Numbers

Knowing the different parts of a boat is important for any mariner. If you look at your vessel exterior, one of the things that’s noticeable is the keel. But what is a boat keel and what does it do?

The keel is a horizontal structure at the bottom section of the hull, which acts as the boat’s main support. We’ll cover keel definition boat use and other relevant information.

Keep reading to learn more.

Table of Contents

The Boat Keel and What It Does

6. centerboard and swing, frequently asked questions.

The keel of a boat is a beam that acts as structural support for the hull and entire vessel. It has many types, and varying designs lead to differences in appearance, with some being longer and extending deeper into the water.

However, serving as support for the hull is not the only purpose of a keel on a boat. It also counterbalances a vessel, which helps to keep it in place and not be displaced by external factors. It is also partially responsible for moving a boat forward and aids steering.

The keel of a ship functions similarly to the keel on boat, serving as the backbone and ballast. It is often the first thing to be constructed on a ship.

Types of Keels

This type usually covers the entire length of the vessel and is one of the most common types used. This keel offers a high degree of safety, owing to its very stable performance along with the ability to run through sand without breaking off.

This is similar to the full keel but shorter, running less than 50% of the length of a vessel. This difference allows it to contribute to a boat’s ability to turn while also giving improvements to its speed. This type is commonly found in racing models.

This keel boat part is similar to the fin, except for the bulb attachment at the bottom, which resembles a torpedo.

The shape of the bulb also makes it less likely to be damaged by contact with rocks, and this type is excellent for cruising.

This design extends the length of the keel, making it similar in appearance to an airplane wing. This design allows a vessel to turn and maneuver more easily, but it is more susceptible to breaking or digging into the ground.

Instead of just one at the center, the bilge keel has one for each side of the hull. A vessel with this type of keel has less roll, which gives better comfort on the water. It also has a lower draft and allows easier anchoring on shallow waters.

These are two different types of keels but are grouped because of their similarities in design. These can adjust their length, making them usable for both deep and shallow water. However, centerboards only partially retract, while swing types have their entire length fully adjustable.

These have the advantage of adjustability but less performance, and they also have more components that require checking compared to fixed keels.

This is similar to the swing keel in that its entire length is connected to a hinge at the bottom of a sailboat but adjusts from side to side, starboard to port, and vice versa.

It can boost speed and maneuverability by wetted surface reduction and weight shifting. This is often used for racing vessels but is still considered experimental as there is a high rate of failure due to its reliance on hydraulics.

Hull and keel: what is the difference?

The keel hull confusion likely stems from the fact that the keel is often part of the hull. However, they are two entirely different things, since the hull is the main body of the boat while the keel is a beam that is connected to the bottom of the hull and may extend farther down from it.

Do all boats have a keel?

Most boats do, but not all boats, as flat-bottomed ones are the exception. The keel boat Lewis and Clark Expedition used in 1803 is a well-known example. This was a barge, a type of flat-bottom vessel that was a boat without a keel.

How is the keel of the boat different from the keel at the bottom of a ship?

Both ships and boats have keels that function in similar ways, but how they are constructed and even the keel shape are different. While most types of sailboat keel are fin-like in appearance, a keel ship needs to be much wider to be able to support the entire ship’s size.

Knowing what is a boat keel is a very important matter that you should no longer have trouble with. Now, you can move on to learning other major parts of vessels. Just remember to consider the draft and use a boat keel guard to safeguard your vessel.

Which type of keel is best in your opinion? Tell us all about it in the comments section below. We’ll be waiting to hear from you.

Remember to boat safely.

“My intention from the first day establishing Boating Basics Online is to provide as much help as possible for boaters who want to experience a first safe and convenient trip. So feel free to join us and share your beautiful journeys to the sea!”

Practical Boat Owner

• Digital edition

Keel types and how they affect performance

• Peter Poland
• June 19, 2023

Peter Poland looks at the history of keel design and how the different types affect performance

The Twister is a well-proven example of a generation of production yachts with ‘cutaway’ full keels and keel-hung rudders. Credit: Graham Snook/Yachting Monthly

Having been a boatbuilder for around 30 years until the very early ‘noughties’, I’ve already witnessed – and even taken part in – a lot of changes in the world of yacht design and building.

Yacht design originally evolved as traditional workboats developed into leisure craft.

In his History of Yachting , Douglas Phillips-Birt writes that the Dutch, who gave the name ‘yacht’ to the world, were probably the first to use commercial craft for pleasure in the 16th century.

They created the first yacht harbour in Amsterdam in the 17th century.

When the schooner America visited the UK in 1851 and raced around the Isle of Wight, this led to the America’s Cup and the resulting merry-go-round of race-yacht design that continues to this day.

The Jeanneau Sun Odyssey 35 offers three different fin keel configurations with different draughts plus a lifting keel version with a centreplate housed in a shallow winged keel stub. Credit: David Harding

The creation of what is now the Royal Yachting Association ( RYA ) in 1875 led to the introduction of handicap rules, establishing the sport in Britain.

These rating rules – and their numerous successors down the ages – have helped determine the evolution of yacht design and keel shapes.

Many early yachts were closely based on workboats, commercial cargo carriers or even privateers and naval vessels.

Initially, the ballast was carried in a long keel and the bilges .

New racing rules of the day taught designers to seek and tweak performance-enhancing features.

Maybe racing did not always improve the breed, but it certainly kept it moving ahead.

Artwork inspired by Ted Brewer’s illustration of keel types (excluding centreplate or lifting keels)

The late, great designer David Thomas believed that fishing boats, pilot cutters and oyster smacks had a large influence on the sport of sailing.

Each type of workboat was built to fulfil a specific purpose. And many had to be sailed short-handed while carrying heavy cargoes.

So they needed to combine form and function, sail well and be able to cope with heavy weather.

Proof of the versatility of working boat designs was provided by Peter Pye and his wife, Anne.

They bought a 30ft Polperro gaff-rigged fishing boat (built by Ferris of Looe in 1896) for £25 in the 1930s.

Having converted her to a sea-going cutter, and renamed her Moonraker of Fowey , they sailed the world for 20 years.

It proves how the simplest working boat design can cross oceans and fulfil dreams.

Racing influence on keel types and design

Most early yacht designs were schooners, but during the latter half of the 19th century the gaff cutter rig started to dominate the scene.

Many notable yachts were built at that time and the most important racing design was probably the yawl Jullanar (1875).

Designed and built by the agricultural engineer EH Bentall, she had, in his own words, “the longest waterline, the smallest frictional surface, and the shortest keel”.

She proved to be extremely fast and in her first season won every race she entered. Jullanar became the forerunner of such famous designs as GL Watson’s Thistle (1887), Britannia (1893), and Valkyrie II and Valkyrie III , both of which challenged for the America’s Cup during the 1890s.

Compare the She 36’s graceful overhangs with the vertical stems and sterns of most modern cruiser/racers

In the USA, Nat Herreshoff experimented with hull forms for racing yachts and produced the ground-breaking Gloriana in 1890.

She was a small boat for the times, with a waterline length of 46ft. Her hull form was very different to anything yet seen in the USA.

With long overhangs at bow and stern, her forefoot was so cut away that the entry at the bow produced a near-straight line from the stem to the keel.

It was a revolutionary design, and nothing at the time could touch her on the racecourse.

Many French models, such as this Beneteau, have opted for substantial pivoting keels. Credit: Peter Poland

Herreshoff wrote: “Above the waterline everything on Gloriana was pared down in size and weight… and every ounce of this saving in weight was put into the outside lead.”

Early English rating rules produced the ‘plank-on-edge’ yacht, where the beam became narrower and the draught got deeper.

New rating rules were then adopted to discourage this extreme type and eventually the Universal Rule was introduced in the USA and the International Rule – which produced the International Metre Classes – took over in Europe.

Yet again, racing rules proved to be a major influence on design development.

By the start of the 20th century the big, long-keeled racing yachts like the J Class attracted a lot of public attention, but after World War II everything changed. Yachts built to the Universal Rule fell from favour.

The age of the racing dinghy arrived and the ocean racer became the performance yacht of the future.

To new extremes

A 300-mile race from New York to Marblehead saw the start of offshore racing and the first Bermuda race was run in 1906.

The British were slower to compete offshore, but in 1925 seven yachts took up the challenge to race round the Fastnet Rock, starting from the Isle of Wight and finishing at Plymouth.

EG Martin’s French gaff-rigged pilot cutter Jolie Brise won the race and the Ocean Racing Club was formed.

In 1931 this became the Royal Ocean Racing Club (RORC), which remains the governing body of offshore racing in Britain.

The ‘cutaway’ modified full keel was famously used by Olin Stevens on his mighty Dorade. Credit: Christopher Ison/Alamy

The early competitors in RORC races were long-keeled cruising boats, many of them gaff rigged and designed for comfort and speed.

But everything changed in 1931 when the young American Olin Stephens designed and then sailed his family’s 52ft yawl Dorade across the Atlantic to compete in that year’s Fastnet race.

She won with ease. Then she did it again in 1933, having first won the Transatlantic ‘feeder’ race.

At 52ft LOA, with sharp ends and 10ft 3in beam, some said Dorade looked like an overgrown yawl rigged 6-metre. But her triple-spreader main mast was revolutionary. As were her cutaway forefoot, lightweight construction, deep ballast and 7ft 7in draught.

Dorade took the long keel format to new extremes.

In the USA, the Cruising Club of America (CCA), founded in 1922, played much the same role as the RORC did in Britain.

It introduced its own rating rule which influenced the evolution of yacht design in the USA.

The Elan 333. Both the deep (1.9m) and shallow (1.5m) draught models feature an elegantly faired bulb keel and spade rudder. Credit: Peter Poland

Beam was treated more leniently under the CCA rule, so wider American designs later offered more space for accommodation and a bit more inherent form stability than RORC-rule inspired yachts.

Many famous designers of long-keel racing yachts at this time developed their skills at the yachtbuilding firms they ran, such as William Fife II (1821–1902), his son William III (1857–1944), Charles E Nicholson (1868–1954) of Camper & Nicholsons and Nat Herreshoff of Bristol, Rhode Island.

Around the same time several British yacht designers made their names, including George L Watson (1851–1904) who set up one of the earliest Design Offices and Alfred Mylne (1872–1951), who designed several successful International Metre Class yachts.

Norwegian designers Colin Archer (1832–1921) and Johan Anker (1871–1940) also joined the party.

Continues below…

Boat hull design: how it impacts performance

Peter Poland explains how boat hull design has evolved over the years and how it affects boat handling and accommodation

Sail boat rigs: the pros and cons of each popular design

Peter Poland looks at the history of popular rig designs and how the different types affect boat performance

Improve performance by understanding boat design

Øyvind Bordal explains how form stability, LOA, LWL, speed tables and polar diagrams can help you choose the right boat…

Coming of age: the 1970s yacht designs that have stood the test of time

Sailing in the 1970s was characterised by innovation, enthusiasm, mass participation and home boatbuilding. Rupert Holmes reports

In 1873 Archer designed the first long keel Norwegian yacht, but his real interest was work boats – pilot boats, fishing craft, and sailing lifeboats – some of which were later converted into cruising yachts.

Erling Tambs’s Teddy was a classic Colin Archer long keel canoe-stern design in which he wandered the globe with his young wife and family.

He proved the seaworthiness of Archer’s yachts, as well as their speed, by winning the 1932 Trans-Tasman yacht race.

Fellow Norwegian Johan Anker – a one-time pupil of Nat Herreshoff – became equally famous, thanks to his Dragon-class design that still races today.

As a new generation of designers arrived on the scene in the 1930s, hull tank testing became more sophisticated.

Long keel designs became as much a science as an art.

The leader of this new wave of designers, Olin J Stephens, had been a junior assistant to Starling Burgess who designed race-winning J Class yachts, including the iconic Ranger .

Tank testing was then in its infancy but the USA was ahead of the game and Stephens stored away everything that he learned. He enjoyed a head start over his contemporaries.

Keel types: Fin keels

Between the 1930s and the 1980s more fin keel designs began to arrive on the scene and his firm Sparkman & Stephens produced many of the world’s top ocean racers.

He also designed America’s Cup 12-Metres that defended the cup up to 1983 until Ben Lexcen’s winged keel shook the sailing world.

Many S&S fin keel and skeg production boats – such as the Swan 36 (1967), 37, 40, 43, 48, 53 and 65, She 31 (1969) and 36 and S&S 34 (1968) – still win yacht races and are much sought after as classics.

The S&S 34 has several circumnavigations to its name. Stephens, of course, had his rivals.

Among these was the Englishman Jack Laurent Giles, whose light displacement race-winner Myth of Malham had one of the shortest ‘long keels’ of all time.

(L-R) A Sigma 38 designed by David Thomas and Gulvain (1949) by Jack Giles as a development of his Fastnet-winning Myth of Malham have very different keel types. Credit: Peter Poland

The Dutchman EG Van de Stadt designed the Pioneer 9 (1959) which was one of the first GRP fin keel and spade rudder racers.

Towards the end of his career, Olin Stephens also came up against Dick Carter, Doug Peterson, German Frers and the Kiwis Ron Holland and Bruce Farr.

The development of new shaped keels went hand in hand with this rapid evolution in yacht design.

The full keel, as still found on motor-sailers such as the Fisher range, gave way to the ‘cutaway’ modified full keel as famously used by Olin Stephens on his mighty Dorade , designed back in the late 1920s.

She still wins ‘classic’ yacht races in the USA. American designer Ted Brewer wrote in ‘ GoodOldBoat ’ that Dorade’s offshore racing successes proved that the full keel is not essential for seaworthiness.

The Nicholson 32’s modified ‘cutaway’ long keel results in excellent performance and handling. Credit: Genevieve Leaper

As a result of its improved performance and handling, the modified ‘cutaway’ long keel caught on quickly and became the standard for around 35 years.

This keel type is found on numerous popular designs such as the Nicholson 32 , 26 and 36, Twister 28 and many Nordic Folkboat derivations.

The modified full keel format had a cutaway profile, giving good handling and directional stability while having less wetted surface than the full keel designs.

These yachts can perform well in all conditions and have a comfortable motion.

Even though they are generally of heavier displacement than fin keelers, they are not much slower in light airs , despite their added wetted surface area.

Their main drawback is a wide turning circle ahead and reluctance to steer astern when under motor.

Keel types: Increased stability

The modified full keel was subsequently cut away more and more for bluewater and inshore racers in an attempt to reduce wetted area until, finally, some designers took it to extremes.

As a result, much-reduced directional stability produced craft that were difficult to steer in breezy conditions, broaching regularly.

Whereupon the fin keel and skeg-hung rudder took over, reinstating increased directional stability, improving windward ability, reducing drag and restoring – when under power – control astern and on slow turns.

This fin and skeg format was later followed by the NACA sectioned fin keel with a separate spade rudder .

Soon, many performance cruisers followed this race-boat trend.

The Hanse 430 has a spade rudder and bulbed keel (draught 2.16m or 1.79m shoal draught. Credit: Peter Poland

Many builders now also offer shoal draught fin keel options and shallower twin rudders.

Some, such as Hanse, incorporate L- or even T-shaped bulbs on some Hanses and Dehlers at the base of finely shaped cast iron fins.

A new international competition had encouraged the initial development of modern fin keel yacht designs.

The revamped One Ton Cup was launched in 1965 for yachts on fixed handicap ratings (typically around 37ft long).

This spawned later fixed-rating championships for Quarter Tonners (around 24ft), Half Tonners (around 30 ft), Three-Quarter Tonners (around 33ft), and finally Mini-Tonners (around 21ft).

All these yachts were eventually handicapped under the International Offshore Rule (IOR) that replaced the old RORC and CCA rules.

The revamped One Ton Cup helped encourage the developed of modern fin keel designs. Credit: Getty

Countless production fin keel cruisers designed and built in the 1970’s to 1990’s boom years were loosely based on successful IOR racers that shone in the ‘Ton Cup’ classes.

The IOR handicap system’s major drawback was its Centre of Gravity Factor (CGF) that discouraged stiff yachts.

Once the international IRC rule replaced the IOR, more thought was given to increasing stability by putting extra weight in a bulb at the base of the keel.

GRP production boats followed suit. The keel foil’s chord needed to be wide enough to give good lateral resistance (to stop leeway), yet not be so wide as to add unnecessary drag.

Exaggeratedly thin foils are not suited to cruising yachts because they can be tricky upwind.

Tracking is not their forte and they can stall out. A bonus was an easier ride downwind thanks to wider sterns.

Keel Types: Lead or iron?

And then there is lead. Almost every production cruiser has a cast iron keel for one simple reason; it is much cheaper than lead. But it’s not as good.

Not only does it rust; it is ‘bigger’ for the same given weight. A cubic metre of iron weighs around 7,000kg, while the same cubic metre of lead weighs around 11,300kg.

An iron keel displaces far more water (so has more drag) than the same lead weight. We had always put iron keels under our Hunters – as did our competitors.

But when we came to build the Van de Stadt HB31 cruiser-racer, designer Cees van Tongeren said “No. We use lead.” “Why?” I asked. Cees replied: “If we use iron, the keel displaces more, so the boat sails worse.”

Rustler 36 long keel’s cutaway forefoot delivers responsiveness and manoeuvrability – a reason the design is so popular in the Golden Globe Race. Credit: Beniot Stichelbaut/GGR/PPL

Which explains why top-flight race boats have lead keels – or at the very least composite keels with a lead bulb or base bolted to an iron upper foil, thus lowering the centre of gravity (CG).

Some modern production cruiser-racers offer high-performance lead or lead/iron composite keels – but at a price.

Many Danish X-Yacht and Elan race-boat models, for example, have a lead bulb on the base of an iron NACA section fin.

Rob Humphreys, current designer of the popular Elan and Oyster ranges, said: “The T-keel is good if you have sufficient draught available. If not, the fin element has too short a span to do its job. This is because the T-bulb doesn’t contribute as usefully to side force as a ‘filleted L-bulb.’

“I developed and tested this shape (a blended-in projection off the back of the main fin) for the maxi race boat Rothmans in 1988/9, and have since used it on the Oysters and Elan Impressions. The ‘filleted’ keel we tested for Rothmans had slightly more drag dead downwind (more wetted area) but was significantly better when any side-force occurred; and side-force goes hand-in-hand with heel angle – which is most of the time! When the model spec allows for reasonable draught, the keel option with the lowest centre of gravity will invariably be a T-keel, with a longer bulb giving the greatest scope for a slender ballast package. An L-keel is a compromise and doesn’t suffer from the risk of snagging lines, mooring warps, and nets. [many modern production cruisers have 100% cast iron L- or T-shaped keels]. A lead bulb is preferable to a cast iron keel in terms of volume and density, but it costs more. However, a lead T-keel in a production environment will almost certainly use a cast iron or SG Iron fin, which may rust.”

The Mystery 35, designed by Stephen Jones and built by Cornish Crabbers, has a lead fin keel. Photo: Michael Austen/Alamy

Rustler Yachts also uses lead instead of iron for their keels.

The Rustler 36 long keel (designed by Holman and Pye and winner of the 2018 Golden Globe Race) has a cutaway forefoot to improve responsiveness and manoeuvrability.

The long keel creates more drag but, as with the Rustler 24, the cutaway forefoot makes the 36 more nimble than a full long keel boat, which are more difficult to manoeuvre in reverse under power.

The rest of Rustler’s offshore range – the Rustler 37, 42, 44 and 57 – designed by Stephen Jones – have lead fin keels.

As does his Mystery 35 built by Cornish Crabbers.

These offer an excellent combination of directional stability, performance and lateral stability. The yachts track well, are comfortable in choppy seas, and have good manoeuvrability, all without the flightiness of shorter chord fin keels found on many production family cruisers.

A digital future

Influential designer David Thomas said: “When I started designing, I integrated sharp leading edges to the keel; until someone told me a radius was better. Then we were all taught that an elliptical shape was better still. With the advent of computers, designers could better visualise the end-product; and clever ‘faring programs’ speeded this up.”

So where next? A combination of lighter and stronger materials, rapidly developing computer programs, a desire for maximum interior volume and low costs has led us to today’s production yacht.

Twin rudders improve the handling of broad-sterned yachts when heeled.

The IRC rating rule permits low CG keels, wider beam and near-vertical bows and sterns.

And designers now have an array of new computer tools at their disposal. But maybe there’s still that element of black magic?

As David Thomas so succinctly said: “You can design a yacht 95% right, but the last 5% can be down to luck.”

Keel types : the pros and cons

Full length keel

The Fisher 31 and many motor-sailers have long keels. Credit: Peter Poland

Pros: Directional stability. Heavy displacement leading to comfort at sea.

Cons: Poor windward performance. Large wetted surface leads to drag. When under power at low speeds, the turning circle is wide unless fitted with thrusters. The same applies to manoeuvring astern.

Cutaway modified long keel form with keel-hung rudder

Pros: Reduced wetted surface area leading to increased boat speed. Better windward performance and handling than full length keel. Rudder on the aft end of the keel improves self-steering ability on some designs.

Cons: Under engine, this keel form has a large turning circle ahead and poor control astern. Since the rudder is not ‘balanced’, the helm on some designs can feel quite heavy.

Fin keel with skeg-hung rudder

The skeg gives protection to the rudder. Credit: Graham Snook/Yachting Monthly

Pros: The further reduction in wetted surface area leads to more boat speed. Directional stability and close-windedness are also improved. If full depth, the skeg can protect the rudder against collision damage.

Cons: When combined with a narrow stern, this keel format can induce rolling when sailing dead downwind in heavy winds.

Fin keel with separate spade rudder

Fin keel with spade: Low wetted surface and aerofoil shapes enhance performance. Credit: Graham Snook/Yachting Monthly

Pros: The fin and spade rudder mix reduces wetted surface and gives a more sensitive helm – especially if the blade has ‘balance’ incorporated in its leading edge. Handling under power in astern is precise and the turning circle is small.

Cons: The rudder is fully exposed to collisions. There are no fittings connecting the rudder to a keel or skeg, so the rudder stock and bearings need to be very robust.

Shallow stub keel with internal centreplate.

Pros: When lowered, the plate gives good windward performance. The plate can act as an echo sounder in protected shallow water. There is normally no internal centreplate box to disrupt accommodation. With the plate raised, off-wind performance is good.

Cons: The plate lifting wire needs regular inspection and occasional replacement. Windward performance with the plate raised is poor.

Lifting or swing keel

Boats with lifting keels tend to surf earlier downwind. Credit: Graham Snook/Yachting Monthly

Pros: Shallowest draught so more cruising options; can also be moored on cheaper moorings. Surfs early downwind. Small wetted surface so can be fast.

Cons: Reduced living space due to internal keel box. With a raised keel, poor directional control. Susceptible to hull damage if grounding on hard material.

Twin or bilge keel

Bilge- or twin-keelers can take the ground on the level. Credit: Graham Snook/Yachting Monthly

Pros: Can take the ground in a level position. Modern twin-keel designs with around 15º splay, around 2º toe-in and bulbed bases perform well upwind. Good directional stability due to the fins. Modern twin keels with bulbed bases lower the centre of gravity.

Cons: Older designs do not point upwind well. Slapping sound under windward keel when at a steep angle of heel on older designs. Antifouling between the keels can be tricky. Can be more expensive than fin keels.

Wing keel: A low centre of gravity gives a good righting moment. Credit: Graham Snook/Yachting Monthly

Pros: Low centre of gravity means good righting moment. Shallow draught. Sharper windward performance.

Cons: Larger surface area means it is more likely to pick up fishing gear, like lobster pots. Difficult to move once it is grounded. And difficult to scrub keel base when dried out alongside a wall.

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Top 6 Characteristics of a Good Catamaran

What Makes a Good Catamaran?

As we (Stephen and Estelle) self-isolate during this pandemic aboard Zuri, our Bali 5.4, we thought we would share some insights about important features you should think about when buying a catamaran. We started out with 5 then at the end, Stephen threw in another 3. What are your thoughts? What are important features on a catamaran. Let us know below in the comment section.

Like all marine vessels, certain characteristics make some catamarans better than others. You will not find a perfect catamaran because no boat is perfect. Compromise is always required. But with forethought about how you will utilize your multihull, and matching your requirements to high quality design, you can get pretty close to your “dream” catamaran.

Crucial attributes to consider for a cruising catamaran are:

• Weight-carrying ability
• Bridge deck clearance
• Structural integrity and seaworthiness
• Windward ability
• Deck surface design
• Ease of handling

We will explore each of these catamaran characteristics, and how they affect performance, comfort, and, ultimately, safety.

Early catamaran designs were heavy by today’s standards. The multihulls were designed with a narrow beam, high freeboard, and inefficient underwater design. They were prone to hobby horsing and pitching. Today, with the technological advancements of lighter, stronger composite materials, catamarans performance has greatly improved.

In the last 20 years or so, boat builders have painstakingly studied and resolved the issues affecting catamarans, effectively increasing their seaworthiness by leaps and bounds. Constant reform and transformation of even the basic tenets of catamaran design continue today as is evident in the radical catamaran designs in the 2013 America’s Cup Challenge. (The foiling Gunboat G4 designs spring to mind). In fact, many of the problems of the older multihull designs have been eliminated altogether.

The new generation of cruising catamarans offers exciting, fun sailing vessels with great livability, space, comfort, and safety. This was made possible, in no small part, by the early multihull pioneers.

Catamaran Stability & Weight-Carrying Ability

WEIGHT: Unlike the monohull design that can carry weight without much loss of performance, an overloaded catamaran rapidly loses performance and, eventually, safety. In order to counter this, multihull manufacturers are continually looking for ways to reduce construction weight to increase the potential payload capacity while retaining optimal performance.To select a light catamaran, look for hulls with cored construction and interiors built with lightweight materials.  Lighter construction enables catamarans to carry more weight and perform faster, so this characteristic is very important when selecting a cruising catamaran.

Monohulls can heel and spill wind when the sails are overpowered. But a catamaran’s only available response to pressure of a wind gust is to accelerate. So the boat has to be very strong to hold together. Cored construction makes the catamaran strong and very stiff. Stiffness gives a catamaran good performance.

Consider that the catamaran’s hulls are actually two boats joined together by a bridge deck. These “boats” are constantly fighting each other and trying to go in their own direction. The boat structure must be strong enough to counter this and, at the same time, deal with the downforce of the mast in the center of the bridge deck. The catamaran performs an amazing feat contending with all the opposing forces inherent in the multihull design. For that reason, it is critical to ensure the design and manufacturer are reputable with a track record to demonstrate structural integrity.

STABILITY: Unlike monohulls that rely on a heavy lead keel to keep it upright, a catamaran relies on the beam of the boat and the buoyancy of the hulls for stability. Typically cruising catamarans will have a beam to length ratio of roughly 50%. So a 45-ft long catamaran will be about 22-ft wide, providing a very stable platform. Good stability in a catamaran is when the righting forces and healing forces are in balance. So if the righting moment is greater than the capsizing moment, the boat stays upright. When the capsizing moment becomes bigger than the righting moment due to an increase in wind, the boat starts to capsize. <

This diagram and article by James Wharram, king of “self-build” catamarans, offer valuable insight into catamaran stability. Also, read this article by Shuttleworth “ Design Considerations for Seaworthiness “.

Catamaran Bridge Deck Clearance

Bridge deck clearance is a key factor in predicting the slamming level of a catamaran design. A higher clearance produces less slamming. My rule of thumb is; 4% of the overall length is low, 5% is acceptable, and 6% is good.

When it comes to slamming, another important factor is weight. If the boat is heavy due to construction or payload, it will tend to go into a wave. This slams the chest of the boat into the wave. A lighter boat with more buoyancy will rise on the wave reducing slamming substantially. “ The Space Between ” by Sackville Currie, explains in detail the different options, problems, and compromises.

Windward Ability: Catamaran Keels vs. Dagger Boards

Catamarans with dagger boards are able to point much better than catamarans with keels. The claim is that a catamaran with dagger boards is safer because if the boards are up and the boat gets sideways on a wave, it will skid down the wave sideways. Dagger board proponents believe a keel trips the boat as it tries to navigate down the side of a wave causing capsize.

I can only speak from personal experience. I was caught sideways on a 20-foot wave a few days out of Cape Town on a 40ft catamaran with keels. The boat was hit by successive three waves before we could get it back on track. The boat skidded down the waves and there was no capsize, but it took some nifty maneuvering at the helm. My personal belief is that both types are safe and acceptable provided they are operated correctly.

Catamaran Deck Surfaces

Cockpit to Mast

Older designs often have decks with two levels from the coach roof windows to the gunnels which form a side deck with a trip hazard. Most modern catamaran deck designs are now one flat surface being wide enough to walk unhindered from the cockpit to the mast.

The cockpit and the saloon should be on one level with no step down into the saloon, if possible. Modern designs have achieved this and it really makes a big difference for ease of movement and safety while at sea.

The steps on the stern should be wide and easy to climb with a reasonable angle. If the steps are too steep or narrow, they become a hazard and lose space for recreation. The stern should be easily accessible from the dinghy.

Ease of Handling: Catamaran Deck Layout

• Both jib sheets
• The sheet from the opposite side of the boat should be run through a turn block and across the coach roof through a clutch to the helm
• Jib furling line
• Single line reefing lines
• Main halyard
• Traveler control lines.

Visibility from the helm is also very important. All round visibility while underway, maneuvering, or docking is key to safety of your boat and others’ property and life. When standing at the helm, you should be able to see both bows or, at the very least, the pulpits. The center of the crossbeam where the anchor is handled from should be visible as well as both sterns for when you dock “stern to”. If all these stations are not visible while standing at the helm where the engine controls are, you may encounter problems because of blind spots.

Catamaran Characteristics Conclusion

Modern catamaran designs are much more advanced than the early models that were slower, heavier, and underpowered. Problems like hobby horsing, burying the bows, and underpowered rigs have been largely eliminated.

Even though composite construction technology gives a huge advantage in lighter materials and sleeker designs, no one design element or piece of high tech gear should dominate the vessel to the detriment of others. With some compromise, a good naval architect can design a vessel pleasing to most people and the result can be very exciting, safe, and seaworthy.

Top Tip: Use a Broker at No Cost

Which compromises should you make when selecting your catamaran? It all depends on how you will use her. Catamaran Guru helps new and veteran multihull owners select the right boat for their dreams at no cost! The yacht seller pays broker commissions so our advice from gleaned from thousands of boat-buying transactions is free to you. We will help you find right boat, the right program, or the right situation. If you want to explore more on your own, visit our buying a catamaran section.

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Main types of the sailing equipment of a yacht

Dear friends, we shall continue our series of articles on the topic “Yachting for beginners”. In this selection, we share the information that will help you gain your desired aim of becoming a true yachtsman. Even if you do not have such ambitious plans, it will be interesting to learn some more facts about sail catamarans and their design.

Today we will talk about the sailing equipment of a yacht. It consists of sails, a mast, a boom, shrouds, a mainsail, a spinnaker, a gennaker, a stay, a jib and a sheet.

• A sail is made of a special cloth or a plate. It is attached to the hull in order to transform the airflow energy into the energy of motion. The sail has a sophisticated structure consisting of many different elements. You can see them on the picture below.
• A mast is a stand-up structure that provides the form, the stability and the flexibility of the sail.
• A boom is a facility serving for the stretching of the lower part of the gaff-sail. It is fixed horizontally on the mast, and it can be movable or not.
• Shrouds are galvanized or steel cables of the dead ropes of a sail catamaran. They fix the mast in a vertical position.
• A mainsail is the back part of a sail playing the key role in its structure. Its settings influence the running if the sail catamaran in different weather conditions.
• A spinnaker is an extra “racing” sail helping the mainsail on the high speed. It is made of light cloth and acts like a parachute.
• A gennaker is an alternative to the spinnaker, but it is smaller. It can be used not only in regattas, but also in cruises with a few people on board.
• A stay is a rigid steel cable keeping the mast from falling back.
• A jib is a triangular sail fixed on a stay in order to support the mast.
• A sheet is a rope that is fixed at the lower part of a goosewing or at the lower back corner of a gaff sail.

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Boats "sailboats" for sale in San Diego

• 36ft SAILING TRIMARAN $3,500 SAN DIEGO
• 39' Yorktown Sailboat, Great live aboard! $28,000 Mission Bay
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• 1976 Catalina 30 $8,500 Oceanside Harbor
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• Cal 34 Classic Sailboat $5,500 san diego
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• Westsail 39 blue water cutter $24,999 Coronado Cays, San Diego
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