light displacement sailboat

Preview: What About a Sailboat’s Displacement? Doug Hylan Discusses Light and Heavy

A mong the dockside pundits, the discussion of light vs. heavy displacement usually revolves around the ability of a cruising sailboat to carry the necessary provisions and gear for extended cruising. I would like to consider the question from another angle: appearance and cost.

L ight displacement boats have some real advantages. Up to a certain point, lighter displacement saves money, both in initial cost and continuing expenses. Cy Hamlin pioneered this idea with his Controversy yachts produced at Mt. Desert Yacht Yard in the 1960s. Many people are surprised to learn that boats, like meat, tend to cost by the pound, not the foot. Compared to a heavy displacement 40-foot sailboat, a lighter boat of the same length will require smaller sails, lighter rigging, smaller ground tackle, a smaller engine, and less ballast.

U nder many conditions, lighter boats can also be faster. For one thing, they can cheat the devil of hull speed, even plane if they are very light and have the proper hull shape. This was one reason that MARY ANN, the first Barnegat Bay A Cat, was able to sweep aside the older heavier competition on the bay, even though they sported vastly bigger sail plans.

N at Herreshoff, the Wizard of Bristol, took advantage of both of these factors. One of the many facets of his wizardliness was his intuitive feel for light, stiff and strong construction. His boats generally had lighter structure than the competition, making them both cheaper to build and faster under sail. Even when a rating rule demanded that boats be of a certain displacement, lighter construction meant that more of that weight could be put into ballast. Ballast is not only one of the cheapest components per pound in a boat, but a greater proportion of ballast increases stability, meaning that the boat can stand up to more wind before reefing.

A esthetics, however, is one area where lighter boats have trouble competing. While they may not be able to enumerate the reasons, most people will admit that older boats tend to look more graceful and appealing than their modern sisters. Although several factors are involved, a major one is freeboard, or the amount of hull that shows above the waterline. Older boats generally have less, and just as with cars, lower and sleeker usually looks better.

I n the world of boat design numbers (called hydrostatics), the relative “lightness” or “heaviness” of a boat is defined by its displacement/length ratio, usually abbreviated as D/L. I’ll spare you the formula, but keep in mind that this is a dimensionless number – in other words, it makes no difference if the boat is a dinghy or an ocean liner. If her D/L is 400 she is considered to be in the heavy displacement realm. If the D/L is 150, she is pretty light.

W hy do lighter boats tend to be higher sided? Archimedes who purportedly jumped out of his tub and ran naked through the streets of ancient Syracuse shouting “Eureka!” is credited with the answer. The heavier a boat is, the more there is of it under water. The more there is under water, the less of it there needs to be above water to get the same amount of headroom.

C onsider the two boats shown below, one an old style heavy cruiser (D/L 400), the other a modern light displacement sister (D/L 150). Both boats have an overall length of 33′, a waterline length of 28 feet and a draft of 5 1/2 feet. They both have the same 6-foot headroom, but the cabin sole of the lighter boat must be much higher, so either the topsides or the cabin (usually both) has to be moved up to get the same headroom.

S o, tall people who are unwilling to bump their heads (or bend over to avoid it) can be the ruination of good looks in small, light displacement boats. Daysailers, where headroom is not considered essential, are generally immune to this problem, and once a yacht gets to 60 or so feet in length, there is plenty of height in either type for homo erects.

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10 Responses So Far to “ What About a Sailboat’s Displacement? Doug Hylan Discusses Light and Heavy ”

Paul Rybon says:

One of the most puzzling riddles is with the incessant pitching of my Wittholtz designed Dickerson 35 ketch. Hull specs and profiles are online. The other annoyance is with the ultra-quick movement unless hard-pressed with sail. Also, even in small-to-moderate waves, it comes to almost a complete stop upon meeting a wave. So here’s my question; I’m about to replace the bottom because the seams and frames are worn out. Do you think the boat would have better riding characteristics if I widened it at the same time? Should I add more ballast? Spread out the ballast? Lower the sides? Instal heavier masts? Mr. W. is gone, can’t ask him. Any ideas? Paul on the Chesapeake Bay

Charles Zimmermann says:

It would be great to see this blog continued regarding the difference in sea keeping, movement through the waves, interior livability, and aesthetics – with a focus on sailors who are over 50 years old and simply want to sail down the coast and maybe reach Martha’s Vineyard if the winds are favorable, or maybe just spend a night in Provincetown if the winds are not. In other words, a focus on the kind of cruising in which two to four people could get out on the water and have fond memories when they get back to the boat’s home port. Also I’d like to add a comment on headroom. I am 6 feet 2 and I couldn’t possibly afford a 60 foot boat; I have a heavy displacement traditionally built 30 foot boat which was custom built for someone about 4 inches shorter. Every time I hit my head I wish he had been a little taller.

William Lavender says:

With your experience with Quiet Tune, how do you think Joel White reconciled these factors in his adaptation of this design?

Doug Hylan says:

QUIET TUNE is pretty light, something LFH, who by this time was abandoning any concern for rating rules, achieved by lengthening the waterline (reducing overhangs). In fact the displacement length ratio for the two boats is for all intent and purposes, the same (222 for GRACE, the first CH 31, and 231 for QUIET TUNE). GRACE is 1 1/2 feet longer and has about 4″ more freeboard. Both boats have about 50″ of headroom: Joel could match the headroom number (about the minimum necessary for sitting headroom) through the 31’s bigger size, higher freeboard and beamless cabin top. Most of the subsequent Center Harbor 31s had their sheer raised 3″.

Cold molded construction and a lighter rig allowed Joel to put a bit more of that displacement into ballast, but QT is no slouch in the ballast ratio department. But QT is badly under rigged, and Joel, who by that time had embraced computer aided stability calculations, was able to confidently correct that situation.

In fact, I don’t believe that the Center Harbor 31s owe very much to the QUIET TUNE design. Yes, they are both daysailers of essentially the same size. But as much as any boat can be considered an original design after several centuries of precedent, the CH 31’s are pure White, much more an evolutionary step in Joel’s work than an adaption of LFH’s.

Thanks Doug! I’ve always loved Quiet Tune’s lines (She’s my “Someday I’ll build that…” boat) and I appreciate any chance to learn more about her. Love your video by the way.

This is a great article and I too hope to read more about the details of displacement!

Steve Stone says:

Thanks Doug… a picture’s worth a 1000 words. Intelligent analysis of two contrasting images side by side… priceless. It cleared up the “why?” about modern boats’ tendency toward high freeboard, and perhaps part of the logic behind straight sheers as well (for, among other things, more standing headroom amidships?). This brought home the point more clearly than I’ve seen before.

Sounds good, so far. How about a ‘page 2?’

Benjamin Mendlowitz says:

Thanks Doug, this is a really informative discussion in clear simple language. I would love to see it continued regarding the differences in sea keeping, movement through the waves, interior livability and aesthetics.

When Robin Knox-Johnson rounded the world in SUHAILI in 1969, he did it in the type of boat that was considered best suited for roaring forties sailing at the time — a very heavy double ended ketch. At that time it would have been considered suicidal to go very far out of sight of land in the type of boats that now regularly complete this race. These ultra light sloops with huge open sterns never heave to. The harder it blows, the faster they sail! Although I doubt that comfort at sea plays a very big part in these sailors’ decisions about what type of design they should use, clearly the boats, if properly handled, can handle horrific weather, and I doubt that their voyages could be much less comfortable than Knox-Johnson’s.

Charles Barclay says:

It’s also been described as “shortening the period of discomfiture”.

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Light Displacement vs Heavy Displacement Of The Boat: 9 Questions Answered

Displacement is the weight of the volume of water the boat is displaced when it is afloat.

The ratio of a boat’s displacement over the boat’s loaded waterline length (the DLR or D/L ratio) decides whether the boat is a light displacement or heavy displacement. if the ratio is over 300 then this boat is heavy displacement. if the ratio is lower than 180 then this boat is light displacement.

Table of Contents

What does light displacement mean?

Light displacement means the ratio of a boat’s displacement over the boat’s loaded waterline length is lower than 180.

Light displacement also means the boat is light, has less material, maybe smaller sail, light rigging, etc.

The Displacement over loaded waterline length ratio (DLR or D/L ratio) formula is below Displacement in long tons /(0.01x loaded waterline length in ft)^3

Are lighter boats better?

It depends on how you are going to use the boat. A lighter boat is awesome for racing because it is much easier and quicker to change direction, and speed up.

The lighter boat sits higher in the water so it will have less drag. The lighter boat is easy to sail with litter wind.

Most sailors do not suggest a lighter boat for an offshore cruise, because a lighter boat tends to roll over or demast in extreme weather. In the worst case, a light boat can be smashed by big wind or a big wave.

What does heavy displacement mean?

The ratio of a boat’s displacement over length is over 000, then this boat is considered a heavy displacement boat/sailboat.

A boat with a heavy displacement means the boat is heavy. The material of the boat is sturdy and heavy.

Are Heavier boats better?

Heavier boats are good for rough weather because the weight of the boat can give you a smooth ride. Heavier boats are more stable than lighter boats.

Normally heavier boats will have heavy rigging and more sail area, making the sailing complex. It might need several people to sail a heavier boat.

Light wind can hardly move a heavier sailboat. A heavier boat sails better on windy days. Heavier boats are not a good choice for new sailors.

What is a planing hull?

A planing hull is a very light displacement hull. The majority of the time the boat cruise on the surface of the water. A planing hull is fast but less comfortable for people.

What is a semi-displacement hull ?

A semi-displacement hull is a combination of a planing hull and a displacement hull. Most coast cruise boats have a semi-displacement hull because a semi-displacement hull has the speed advantage of a planning hull and also has less draft than a full displacement hull.

A semi-displacement hull has more speed than a full displacement because it sits higher in the water and has less drag than a full displacement hull.

A semi-displacement hull also consumes less fuel than a full-displacement hull because it needs less power to propel.

What is a full displacement hull?

A full displacement hull is typically round in shape. The hull sits lower in the water.

A full-displacement hull has deep draft than any semi or light-displacement hull, it needs more power to cross through water.

A full displacement hull is good for an offshore cruise because the displacement hull makes the boat stable and gives you a smooth ride during rough weather. The drawback of a full displacement hull is its slow speed.

Here is a good video to explain planing hull, semi-displacement, and full displacement hull

What is maxed displacement on a boat?

The maximum displacement of a boat is the same as its full load displacement. The water weight displaced when a boat is fully loaded is its maximum displacement.

What shape of boat holds the most weight?

If only concerned with the carrying capacity, a boat like a box holds the most weight. Such as a barge in a rectangular shape with a wide flat bottom will hold the most freight than any other shape of the boat.

If you are concerned about the speed, the bow has to be in a V shape or U shape to have less drag.

What is the most efficient hull design?

A planing hull is the most fuel-efficient hull design. The planing hull is a light displacement hull so the boat basically cruises on the surface of the water. when a boat cruise on top of the water then there is not much drag underwater, and the boat can speed up quickly with little fuel.

The drawback of a planing hull is its stability. This kind of hull is best used in a calm, protected river or lake. It is not suggested to use a planing hull in offshore cruises because the boat is easy to roll over and break in the rough weather.

Multi-hulled boats are more stable than mono-hull boats. Two hulled catamarans offer remarkable stability and enormous space.

How do you maximize buoyancy on a boat?

To increase buoyancy on a boat you can do 3 things. Increasing the volume of the submerged part of a boat, increasing the density of the fluid, and removing some weight from your boat.

Increasing the volume of the submerged part of a boat

Some boat owners add foams to their boats to increase buoyancy.

You can also make the bottom of a boat wide and flat, this will also increase buoyance.

Increasing the density of the fluid

Boats sail fast in salt water than fresh water, because salt water is denser than freshwater

Removing some weight from your boat

Removing anything unnecessary from your boat can increase buoyance.

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A Closer Look at the Rationale Behind the Ratios

Sailboat performance varies based on the eye of the beholder. Racers want light-air alacrity and a willingness to plane while cruisers want directional stability and reasonable speed with moderate sail area. A boats design dimensions and a few simple ratios give some hints about these attributes.

Most performance-oriented boat designs focus on around-the-buoy racing; these assume that there will be a large crew to keep sail area and trim optimized and to provide movable ballast and that the boat must cope with windward and leeward legs of a race course. Offshore, point-to-point race boat designs are greatly influenced by racings handicapping rules. In either case, these rules penalize performance, and design factors like ultra-wide beam-intended to leverage crew weight for righting moment-are of little value to shorthanded cruisers. Make sure that the boat youre looking for is fast in the context under which it will be sailed.

The sail area-to-displacement ratio (SA/D) compares energy and resistance-much like a horsepower-to-weight comparison in an automobile. As the SA/D ratio grows higher, so does the vessels potential speed under sail. However, too much sail area and too little righting moment means a very tender boat. Too little sail area and too much displacement means you can brag about carrying full sail in 20 knots, but your boat will move like a sea buoy in 7 or 8 knots of breeze.

The ballast-to-displacement ratio (B/D) of a boat tells you how much secondary righting moment to expect from the keel. The smaller and lighter the vessel, the more important it is for this number to be higher for stability as well as for performance reasons. Bulbs and other keel-tip shapes lower the vessels center of gravity (CG) and can lessen the need for a 40-percent B/D ratio. A deeper draft can also lower the CG and can improve on-the-wind performance.

A boats displacement-to-length ratio (D/L) has a lot to do with the resistance of a hull shape moving through the water, and since skin drag is the big enemy at lower speeds, the D/L ratio tells us a lot about a boats light-air performance. By increasing the boat length and keeping the displacement the same, decreasing displacement, or doing both, the D/L ratio decreases, and the boat will go faster in light air. Wave-making kicks in as the major resistance at higher speeds, and the implications of the D/L ratio lessen.

In a nutshell, when it comes to performance under sail, light displacement is fast; deep-keel boats point higher and sail more efficiently to weather; full, flat sections aft cause a boat to plane sooner; and more sail area delivers more power. When it comes to delivering the goods in an open-ocean context, seakeeping ability is an important factor in performance as is the amount of punishment the boat and crew can endure.

Ordered by sail-area-displacement (SA/D), this table illustrates a progression from a heavy-displacement cruiser (Westsail 32) to a fast and light racer (Farr 400). Note how the designers altered ballast, sail area, and displacement to reach their goals.

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Basics of Sailboat Hull Design – EXPLAINED For Owners

There are a lot of different sailboats in the world. In fact, they’ve been making sailboats for thousands of years. And over that time, mankind and naval architects (okay, mostly the naval architects!) have learned a thing or two.

If you’re wondering what makes one sailboat different from another, consider this article a primer. It certainly doesn’t contain everything you’d need to know to build a sailboat, but it gives the novice boater some ideas of what goes on behind the curtain. It will also provide some tips to help you compare different boats on the water, and hopefully, it will guide you towards the sort of boat you could call home one day.

Table of Contents

Displacement hulls, semi displacement hulls, planing hulls, history of sailboat hull design, greater waterline length, distinctive hull shape and fin keel designs, ratios in hull design, the hull truth and nothing but the truth, sail boat hull design faqs.

Basics of Hull Design

When you think about a sailboat hull and how it is built, you might start thinking about the shape of a keel. This has certainly spurred a lot of different designs over the years, but the hull of a sailboat today is designed almost independently of the keel. 

In fact, if you look at a particular make and model of sailboat, you’ll notice that the makers often offer it with a variety of keel options. For example, this new Jeanneau Sun Odyssey comes with either a full fin bulb keel, shallow draft bulb fin, or very shallow draft swing keel. Where older long keel designs had the keel included in the hull mold, today’s bolt-on fin keel designs allow the manufacturers more leeway in customizing a yacht to your specifications.

What you’re left with is a hull, and boat hulls take three basic forms.

• Displacement hull
• Semi-displacement hulls
• Planing hulls

Most times, the hull of a sailboat will be a displacement hull. To float, a boat must displace a volume of water equal in weight to that of the yacht. This is Archimedes Principle , and it’s how displacement hulled boats get their name.

The displacement hull sailboat has dominated the Maritimes for thousands of years. It has only been in the last century that other designs have caught on, thanks to advances in engine technologies. In short, sailboats and sail-powered ships are nearly always displacement cruisers because they lack the power to do anything else.

A displacement hull rides low in the water and continuously displaces its weight in water. That means that all of that water must be pushed out of the vessel’s way, and this creates some operating limitations. As it pushes the water, water is built up ahead of the boat in a bow wave. This wave creates a trough along the side of the boat, and the wave goes up again at the stern. The distance between the two waves is a limiting factor because the wave trough between them creates a suction. 

This suction pulls the boat down and creates drag as the vessel moves through the water. So in effect, no matter how much power is applied to a displacement hulled vessel, it cannot go faster than a certain speed. That speed is referred to as the hull speed, and it’s a factor of a boat’s length and width. 

For an average 38 foot sailboat, the hull speed is around 8.3 knots. This is why shipping companies competed to have the fastest ship for many years by building larger and larger ships.

While they might sound old-school and boring, displacement hulls are very efficient because they require very little power—and therefore very little fuel—to get them up to hull speed. This is one reason enormous container ships operate so efficiently. 

Of course, living in the 21st century, you undoubtedly have seen boats go faster than their hull speed. Going faster is simply a matter of defeating the bow wave in one way or another.

One way is to build the boat so that it can step up onto and ride the bow wave like a surfer. This is basically what a semi-displacement hull does. With enough power, this type of boat can surf its bow wave, break the suction it creates and beat its displacement hull speed.

With even more power, a boat can leave its bow wave in the dust and zoom past it. This requires the boat’s bottom to channel water away and sit on the surface. Once it is out of the water, any speed is achievable with enough power. 

But it takes enormous amounts of power to get a boat on plane, so planing hulls are hardly efficient. But they are fast. Speedboats are planing hulls, so if you require speed, go ahead and research the cost of a speedboat . 

The most stable and forgiving planing hull designs have a deep v hull. A very shallow draft, flat bottomed boat can plane too, but it provides an unforgiving and rough ride in any sort of chop.

If you compare the shapes of the sailboats of today with the cruising boat designs of the 1960s and 70s, you’ll notice that quite a lot has changed in the last 50-plus years. Of course, the old designs are still popular among sailors, but it’s not easy to find a boat like that being built today.

Today’s boats are sleeker. They have wide transoms and flat bottoms. They’re more likely to support fin keels and spade rudders. Rigs have also changed, with the fractional sloop being the preferred setup for most modern production boats.

Why have boats changed so much? And why did boats look so different back then?

One reason was the racing standards of the day. Boats in the 1960s were built to the IOR (International Offshore Rule). Since many owners raced their boats, the IOR handicaps standardized things to make fair play between different makes and models on the racecourse.

The IOR rule book was dense and complicated. But as manufacturers started building yachts, or as they looked at the competition and tried to do better, they all took a basic form. The IOR rule wasn’t the only one around . There were also the Universal Rule, International Rule, Yacht Racing Association Rul, Bermuda Rule, and a slew of others. 

Part of this similarity was the rule, and part of it was simply the collective knowledge and tradition of yacht building. But at that time, there was much less distance between the yachts you could buy from the manufacturers and those setting off on long-distance races.

Today, those wishing to compete in serious racing a building boat’s purpose-built for the task. As a result, one-design racing is now more popular. And similarly, pleasure boats designed for leisurely coastal and offshore hops are likewise built for the task at hand. No longer are the lines blurred between the two, and no longer are one set of sailors “making do” with the requirements set by the other set. 

Modern Features of Sailboat Hull Design

So, what exactly sets today’s cruising and liveaboard boats apart from those built-in decades past? 

Today’s designs usually feature plumb bows and the maximum beam carried to the aft end. The broad transom allows for a walk-through swim platform and sometimes even storage for the dinghy in a “garage.”

The other significant advantage of this layout is that it maximizes waterline length, which makes a faster boat. Unfortunately, while the boats of yesteryear might have had lovely graceful overhangs, their waterline lengths are generally no match for newer boats. 

The wide beam carried aft also provides an enormous amount of living space. The surface area of modern cockpits is nothing short of astounding when it comes to living and entertaining.

If you look at the hull lines or can catch a glimpse of these boats out of the water, you’ll notice their underwater profiles are radically different too. It’s hard to find a full keel design boat today. Instead, fin keels dominate, along with high aspect ratio spade rudders. 

The flat bottom boats of today mean a more stable boat that rides flatter. These boats can really move without heeling over like past designs. Additionally, their designs make it possible in some cases for these boats to surf their bow waves, meaning that with enough power, they can easily achieve and sometimes exceed—at least for short bursts—their hull speeds. Many of these features have been found on race boats for decades.

There are downsides to these designs, of course. The flat bottom boats often tend to pound when sailing upwind , but most sailors like the extra speed when heading downwind.

How Do You Make a Stable Hull

Ultimately, the job of a sailboat hull is to keep the boat afloat and create stability. These are the fundamentals of a seaworthy vessel. 

There are two types of stability that a design addresses . The first is the initial stability, which is how resistant to heeling the design is. For example, compare a classic, narrow-beamed monohull and a wide catamaran for a moment. The monohull has very little initial stability because it heels over in even light winds. That doesn’t mean it tips over, but it is relatively easy to make heel. 

A catamaran, on the other hand, has very high initial stability. It resists the heel and remains level. Designers call this type of stability form stability.

There is also secondary stability, or ultimate stability. This is how resistant the boat is to a total capsize. Monohull sailboats have an immense amount of ballast low in their keels, which means they have very high ultimate stability. A narrow monohull has low form stability but very high ultimate stability. A sailor would likely describe this boat as “tender,” but they would never doubt its ability to right itself after a knock-down or capsize.

On the other hand, the catamaran has extremely high form stability, but once the boat heels, it has little ultimate stability. In other words, beyond a certain point, there is nothing to prevent it from capsizing. 

Both catamarans and modern monohulls’ hull shapes use their beams to reduce the amount of ballast and weight . A lighter boat can sail fast, but to make it more stable, naval architects increase the beam to increase the form stability.

If you’d like to know more about how stable a hull is, you’ll want to learn about the Gz Curve , which is the mathematical calculation you can make based on a hull’s form and ultimate stabilities. 

How does a lowly sailor make heads or tails out of this? You don’t have to be a naval architect when comparing different designs to understand the basics. Two ratios can help you predict how stable a design will be .

The first is the displacement to length ratio . The formula to calculate it is D / (0.01L)^3 , where D is displacement in tons and L is waterline length in feet. But most sailboat specifications, like those found on  sailboatdata.com , list the D/L Ratio.

This ratio helps understand how heavy a boat is for its length. Heavier boats must move more water to make way, so a heavy boat is more likely to be slower. But, for the ocean-going cruiser, a heavy boat means a stable boat that requires much force to jostle or toss about. A light displacement boat might pound in a seaway, and a heavy one is likely to provide a softer ride.

The second ratio of interest is the sail area to displacement ratio. To calculate, take SA / (D)^0.67 , where SA is the sail area in square feet and D is displacement in cubic feet. Again, many online sites provide the ratio calculated for specific makes and models.

This ratio tells you how much power a boat has. A lower ratio means that the boat doesn’t have much power to move its weight, while a bigger number means it has more “get up and go.” Of course, if you really want to sail fast, you’d want the boat to have a low displacement/length and a high sail area/displacement. 

Multihull Sailboat Hulls

Multihull sailboats are more popular than ever before. While many people quote catamaran speed as their primary interest, the fact is that multihulls have a lot to offer cruising and traveling boaters. These vessels are not limited to coastal cruising, as was once believed. Most sizable cats and trimarans are ocean certified.

Both catamarans and trimaran hull designs allow for fast sailing. Their wide beam allows them to sail flat while having extreme form stability. 

Catamarans have two hulls connected by a large bridge deck. The best part for cruisers is that their big surface area is full of living space. The bridge deck usually features large, open cockpits with connecting salons. Wrap around windows let in tons of light and fresh air.

Trimarans are basically monohulls with an outrigger hull on each side. Their designs are generally less spacious than catamarans, but they sail even faster. In addition, the outer hulls eliminate the need for heavy ballast, significantly reducing the wetted area of the hulls. 

Boaters and cruising sailors don’t need to be experts in yacht design, but having a rough understanding of the basics can help you pick the right boat. Boat design is a series of compromises, and knowing the ones that designers and builders take will help you understand what the boat is for and how it should be used. 

What is the most efficient boat hull design?

The most efficient hull design is the displacement hull. This type of boat sits low in the water and pushes the water out of its way. It is limited to its designed hull speed, a factor of its length. But cruising at hull speed or less requires very little energy and can be done very efficiently. 

By way of example, most sailboats have very small engines. A typical 40-foot sailboat has a 50 horsepower motor that burns around one gallon of diesel every hour. In contrast, a 40-foot planing speedboat may have 1,000 horsepower (or more). Its multiple motors would likely be consuming more than 100 gallons per hour (or more). Using these rough numbers, the sailboat achieves about 8 miles per gallon, while the speedboat gets around 2 mpg.

What are sail boat hulls made of?

Nearly all modern sailboats are made of fiberglass. 

Traditionally, boats were made of wood, and many traditional vessels still are today. There are also metal boats made of steel or aluminum, but these designs are less common. Metal boats are more common in expedition yachts or those used in high-latitude sailing.

Matt has been boating around Florida for over 25 years in everything from small powerboats to large cruising catamarans. He currently lives aboard a 38-foot Cabo Rico sailboat with his wife Lucy and adventure dog Chelsea. Together, they cruise between winters in The Bahamas and summers in the Chesapeake Bay.

A Complete Guide to Displacement Hulls (Illustrated)

The displacement hull is the classic go-to hull design for sailboats and one of the most recognizable ones out there. In this guide, I explain all there is to know about them.

What's a displacement hull? A displacement hull is a boat hull design that uses buoyancy to support its weight. It lies partially submerged and displaces water when moving, hence its name. The amount of water it displaces is equal to its weight. It's very stable in rough waters. That's why this design is widely used on cruisers and sailboats.

Displacement hulls are great and reliable. Below we'll talk all about that. But they all have one major setback. Read on to find out what.

On this page:

Displacement hull features, how a displacement hull actually works, why it's so fuel-efficient, setback: maximum hull speed, advantages & disadvantages of displacement hulls, who might like this type of hull, in conclusion.

Nearly all sailboats have displacement hulls. Displacement hulls are great for operating in rough waters. They are less affected by waves than planing hulls. Because they're so steady, they are to go-to design for many ocean-going boats. Examples of boats with displacement hulls are: sailboats, canoes, and fishing boats and trawlers.

The displacement hull is:

• the most reliable & efficient hull in rough water
• the most fuel-efficient hull
• the most buoyant hull
• the hull with the largest cargo capacity

I'll explain all these points later on, but first, I want to just describe the hull design for you.

Design Features

Displacement hulls are pretty bulky. They have round bilges. The bilge is where the boat's bottom curve meets its vertical sides. The hull itself is round. It's round because that creates less resistance when moving through the water. That roundness is what makes it such a comfortable ride, even in waves.

But that roundness also makes it easy to roll (think of canoes, for example). That's not a good feature in heavy weather. To offset it, sailboats have a heavy keel that runs deep into the water. This counterbalances any roll, making the boat very stable. Sailboats with a long keel are very difficult to capsize.

The hull is rounded throughout, running from bow (front) to aft (back).

The displacement hull is generally pretty heavy. That's okay, since it is supported by its buoyancy, so it doesn't need a lot of power to propel (more on this later). The weight actually helps it be more stable and unbothered by nature's pull. I think it's fair to call the displacement hull with the whale among boats . It uses the water's upforce to carry it, and gently peddles along.

How Fast Is It?

Since this hull needs to move a lot of water before going anywhere, displacement hulls are pretty slow. Actually, it very well may be the slowest hull type out there. On average, their cruising speed lies anywhere between 6 - 8 knots. They can go faster, but most boats with displacement hulls don't have the power to do so.

They are great at low speeds. Thanks to their shape, they are easy to move and don't require a lot of power. They're actually one of the most fuel-efficient designs out there.

Compared to other hull types:

• Displacement Hull - Partially submerged, buoyant, moves water
• Planing Hull - Glides over water surfaces, generates lift |
• Semi-Displacement Hull - Displaces at low speed, lifts partially at cruising speed

I've written an Illustrated Guide to Boat Hull Types , where I go over 11 different examples of the most common boat hulls . That article will give a great and quick overview to get you up to speed, so if you don't know anything about boat hulls yet, that article is a great place to start.

The shape of the hull creates a sort of air bubble that floats on top of the water. At the same time, the weight of the boat pushes down (or actually, gravity pulls it down). This submerges the boat a bit, anchoring it, in a way. This push-pull gives it its characteristic reliability, making it more stable and better at keeping course.

As with anything that is really good at floating, it doesn't require a lot of energy to propel it. Since it can use the water to carry it, it's great for carrying cargo. You can really load her up without drastically increasing fuel consumption.

A planing hull needs to get up to speed before it generates lift, and until it does, it's absolutely rubbish in terms of a smooth ride. That's why planing hulls can get so uncomfortable in waves. They can't get up to speed, and their hull isn't made for displacing - rather flying - so it becomes a terrible ride.

The one major setback for displacement hulls is the upper-speed limit. As I've noted before, they are pretty slow. But the thing is: they can't go beyond their upper-speed limit, even if you gear her up with massive outboard engines and so on. The reason for this is called the maximum hull speed .

To understand the maximum hull speed and how it works, I want you to think of yourself lying in the Mediterranean Sea. That's just arbitrary, but since I can pick any sea I like in these kinds of visualizations, I prefer the Mediterranean. So you're lying in the Meds and along comes a sailboat. The sailboat hauls a rope behind it (I know, a line). You grab on to the rope and hold tight. The sailboat gently drags you along. It accelerates. The pull increases, you have to grab on even tighter. It accelerates even more. You have to really clench now.

The reason you have to increase your grip when the sailboat accelerates is simple. Your body displaces water when you move. When the speed increases, it has to displace the same amount of water, but faster. The water resistance (drag) increases.

The power needed to displace water increases exponentially with speed.

So now you can probably imagine that there will be a point where you can no longer hold on and have to let go. You have to slow down. That's your maximum hull speed working.

In the same way, there's a point where the boat's drag becomes so large, that it becomes almost impossible to propel it, no matter the amount of power. That speed is called the maximum hull speed. Every displacement hull has one, and it is a direct correlation with the boat's length. If you want to check out the maximum hull speeds for different boat lengths and learn how to easily calculate it yourself, you can check out a previous article. In it, I go over average sailboat speeds and the formula for calculating maximum hull speed .

By the way, the reason planing hulls can go faster, is that they generate lift at a certain speed. In terms of our story just now, that's the same as if you got yourself a wakeboard. Then, when the boat accelerates, at one point you pull yourself out of the water, and glide over the surface, instead of lying in it.

As with anything, this design has both pros and cons. I'll go over each one briefly down below.

• handle well in rough waters
• very hard to sink
• smooth ride
• large cargo capacity
• requires little power: very efficient
• very dependable
• can be very heavy
• large range

Disadvantages

• has a maximum hull speed
• tends to roll
• can capsize if it has no keel
• if it does have a keel, it has a deep draft

If you don't care about speed and are all about range, safety or comfort, the displacement hull is the way to go. It's by far the most comfortable ride of all hull types and will get you anywhere. You can cross oceans, cruise inland - it doesn't really matter. It has the largest range of all the hull types, and the fuel-economy is really impressive. With cruising speeds averaging between 6 - 8 knots, this hull type is the slowest, but also the steadiest. The perfect boat for long-range cruisers and liveaboards.

Displacement hulls have been around for centuries, and they are the most well-known hull for a reason. They're reliable and efficient. Those are perhaps the two most important trades when you're at sea. Nearly all sailboats have displacement hulls, and for cruising, the benefits outweigh the drawbacks big time. If you like speed, however, you should consider getting something with a planing hull or semi-displacement hull. You can learn everything about semi-displacement hulls here .

Jacques Burgalat

Great tutorial ! Do you know of anyone (or company) who could help me with using a fully electric power train on a 19m/40 ton Tjalk? I (and the tjalk) are currently on the Saint Johns River (Florida) which is more akin to a lake or canal than an actual “river”, so fighting waves and currents is not an issue.

Thank you for your help.

Leave a comment

You may also like, the illustrated guide to boat hull types (11 examples).

I didn't understand anything about boat hull types. So I've researched what hulls I need for different conditions. Here's a complete list of the most common hulls.

Semi-Displacement Hulls Explained (Illustrated Guide)

Displacement

There are three main types of displacement. Which one is used in stating specifications is frequently a mystery, since designers and/ or builders and marketers seldom identify which type they are reporting. Hence, unfortunately, the type of displacement quoted in sales brochures and boat magazines varies, and this can cause confusion and hinder calculation of some performance parameters such as the D/L ratio (see next page).

Dry displacement, sometimes called light displacement, is the hull and rig weight excluding weight of crew, equipment, fuel and water, stores, outboard engine if any, and so on. This number is helpful in determining trailer-towing weight. However, "dry" displacement, if shown in brochures, may or may not include water ballast on boats that use that type of ballast.

Loaded or sailing displacement is the weight as equipped for sailing, including crew, equipment, fuel and water, stores, outboard engine if any, and so on.

Half-load displacement is a variation on loaded displacement, being the weight with normal crew and equipment, but with half-filled fuel and water tanks. In theory, either loaded or half-load displacement should be used for calculating various performance ratios such as B/D, SA/D, and D/L (see pages 9, 12, and 13).

Differences between displacement types can be substantial, particularly in small cruisers. For example, designer Charlie Wittholz specifies that the loaded displacement of the Cape Cod Cat 17 is 2,800 lbs. However, he suggests taking off two or three people and their gear, weighing approximately 600 lbs. in total, to obtain the boat's trailering, or dry displacement. Thus he estimates dry displacement at around 2,200 lbs.

But in reality, we believe most sales brochures use dry displacement as the measure of displacement for all purposes—and for lack of a better method of determining half-load or full displacement using our vast collection of sales brochures, we are stuck with using whatever displacement the sales brochures declare. Consequently, in this guide, the number reported is usually dry displacement. Typically, sailing magazines and books also use this same dry displacement to calculate SA/D and D/L ratios. Technically, this is incorrect, but for comparing one boat to another, if done consistently, no great injustice is done.

Even if displacement reported in sales brochures uses the correct definitions, the number can still be grossly in error. For example, in the original C&C Bluejacket 23 sales brochure, the displacement was erroneously listed as 6,000 pounds—much too high for a sleek racer-cruiser of that size. Later the number was amended, without explanation, to 4,000 pounds.

Continue reading here: Sail Area Displacement Ratio SAD

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Related Posts

• Ballast Displacement BD Ratio
• Catamaran Design Guide - Catamarans Guide
• Displacement Length Ratio DL
• Average PHRF Rating - Cruising Sailboats Reference

Readers' Questions

What boat builders use half load displacement?

Most boat builders use half-load displacement when calculating the displacement of a boat. This calculation is typically used to determine the weight of a boat's hull and the amount of ballast needed for a vessel to remain stable in the water. The displacement includes the weight of the boat transom and hull, plus the weight of the fuel, water, and occupants.

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Listed Displacement vs. Max Displacement

• Thread starter odlide
• Start date Nov 22, 2023
• Forums for All Owners
• Trailer Sailors

I know there is a lot of old discussion on this, but I'd like to try again and keep it simple. Is the Listed Displacement the "Maximum" Displacement (i.e., the weight of the water displaced when the waterline is at the painted boot stripe on the hull) or is it the "Delivered" Displacement (i.e., the weight of the water displaced the first time the boat is put in the water after taking delivery and before loading it with accouterments)? So is the Listed Displacement the "Maximum" or the "Delivered" by the definitions above? Thank you!  

It's not simple. Everyone has different definitions -- hence all the different terms you cite. Sometimes it's one thing, other times something else. It can be a number the Naval Architect calculated based on gear that he includes when he adds it up. You have to ask him what he includes. The stove or engine may be heavier or lighter than he thought, so it could be off. Sometimes the waterline is in the wrong place, too.  

Here is what Sail Boat Data has to say " DISPLACEMENT: If you weigh the boat on a scale, that is her actual displacement. It is the weight of sea water that she will displace when she is afloat. Many designers figure displacement when half loaded with stores, liquids and crew. Some report light displacement which is the weight of the hull and permanent equipment but with empty tanks. Light displacement does not include stores, removable equipment (ex. Sails) or crew."  

The listed displacement is the designed displacement or the naval architects best guess as to the boats displacement. As @PaulK notes there are many places where weight can be added or subtracted. Use a little more resin in the build and the weight goes up, heavier sailcloth and the weight goes up. Install a lighter engine and weight goes down. And so forth. The location of the waterline also depends on the actual weight of the boat and the water it is floating in. Boats in fresh water often sit lower in the water than in salt because fresh water is less dense. SailboatData.com has a new interesting data point, pounds per inch of submersion, the amount of weight required to submerge the waterline by one inch.  

Crazy Dave Condon

Is there a specific boat in the mix?  

Crazy Dave Condon said: Is there a specific boat in the mix? Click to expand

odlide said: Looking for a trailer for my Cal 29. Regarding the responses above, if some manufacturers use "Delivered" weight and others use "Maximum" weight as the Listed Displacement, how could you ever know which boat is heavier? You'd be comparing apples and oranges. Seems like there must be a standard (or something close to a standard). A follow up question: Assuming the Listed Displacement is the "Delivered" weight of the boat, how do you find the "Max Load" (i.e., Maximum Displacement minus Delivered Displacement)? Or am I wrong to think that 30'-ish sailboats have a Maximum Displacement (and therefore lack a Maximum Load)? Thanks again! Click to expand

dlochner said: Trying to use builder's information will just drive you nuts. Use the builder's specs as a starting point and realize it is probably a low estimate of the boat's weight. Click to expand

You should see a mfg tag on the trailer if used or new. You will see or find the weight of the trailer and then total weight to include trailer. Once you know the weight of the boat, you will need to see if it falls within the allowed limits of weight being towed on the trailer. It sounds you are trying to find the specific weight of the cal 29. Start with Sailboat Data and then the builder’s specs. Each builder must include dry weight to include boat, keel/rudder, mast/sails, diesel engine, head, galley, etc… For your boat, I would suggest adding 500 pounds to get the weight of your boat. Then add another 10-20 per cent total weight of boat to the mix and see if that falls within the allowable weight to be towed for safety. You will need to confirm the tire load range too I use to be a sailboat dealer and helped designing boat trailers  

Project_Mayhem

JBP-PA said: " DISPLACEMENT: If you weigh the boat on a scale, that is her actual displacement. It is the weight of sea water that she will displace when she is afloat Click to expand

Davidasailor26

Project_Mayhem said: This definition makes it sound like water and a boat weight the same per cubic foot Click to expand

The trailer you are looking for I would suggest four supports each side regardless of pads or bunk boards with a stout keel tray. If you intend to trailer launch, a long extension should be considered. One other thing, the axles need to be adjusted to distribute the load with a 10% of the load on the hitch to prevent the trailer from swaying. Brakes are required. Electric brakes are fine if hauling a boat with a travel lift;,otherwise, I recommend surge brakes. If you hav any questions , just ask. There are no stupid questions in this case  

Crazy Dave Condon said: The trailer you are looking for I would suggest four supports each side regardless of pads or bunk boards with a stout keel tray. If you intend to trailer launch, a long extension should be considered. One other thing, the axles need to be adjusted to distribute the load with a 10% of the load on the hitch to prevent the trailer from swaying. Brakes are required. Electric brakes are fine if hauling a boat with a travel lift;,otherwise, I recommend surge brakes. If you hav any questions , just ask. There are no stupid questions in this case Click to expand

@odlide Take some pictures of the hull and post them here on blisters in a different thread If fouled with algae and/or barnacles, I would suggest a power washing of the hull first.  

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PHRF Racing: Choosing a Boat

• By Bruce Bingman
• Updated: September 18, 2013

Many factors go into buying a sailboat, including price, availability, style, and how much the boat will be used off the racecourse. At the risk of adding another facet to an already complicated decision, we tasked PHRF guru Bruce Bingman with identifying a few boats that are likely to sail above their rating in certain conditions. As is the case with any single-number rating system, every boat will have a sweet spot, a combination of wind strength, sea state, and course configuration under which it will be tough to beat.

For this exercise we asked Bingman to focus on boats that would be predominantly raced in club-level weeknight or weekend races. We wanted boats that are lively, fun to sail, and available. In addition, we restricted him to boats with an average PHRF rating of 30 or greater. Below that number you tend to find dry-sailed race boats requiring professionally managed programs, which are beyond the scope of this exercise, and usually too fast to really race in most local series.

It goes without saying that for any even halfway serious racing, preparation is as important as the boat selected or the handicap rating with which it comes. We’ve all heard it 1,000 times before: There is no substitute for good sails, reliable gear, and a smooth bottom. You may think your two- or three-year-old sails look fine, but you will pick up 6 seconds per mile and more with a new inventory. The most carefully selected boat or the most favorable rating won’t help you overcome a mid-race breakdown such as a broken halyard or jammed winch. A dirty bottom can cost you 30-plus seconds per mile. Even a thin layer of slime will cost you 3 seconds per mile. So pick your weapon, gear up, burnish your bottom, and head for the start.

• Typical conditions: Waves and chop, strong but fading sea breeze
• **Typical racecourses: Multiple lap windward-leewards **

My summer weeknight beercan series is conducted outside the harbor, on an exposed ocean racecourse, so it’s usually choppy. Winds are typically strong sea breezes (15-plus knots) at the start of the race, but lighten as the race progresses. The race committee typically runs one long, three-leg, windward-leeward race.

Here’s where you want the dependable offshore workhorse, and there are many options. A moderate displacement boat, a powerful rig, and a sea-kindly hull will produce a boat that drives upwind, through chop, and carries a spinnaker large enough to preserve a lead.

PHRF 30 to 70: The Beneteau 40.7 is a great offshore racer that provides superior upwind ability in choppy, breezy conditions. Great for a distance races, too.

PHRF 71 to 114: The Beneteau 42s has power and waterline rolled together in a single package. The sails are big, so it requires recruiting some young bucks to help get around the course.

PHRF 115 and up: The Cal 40 is a classic design with the ability to go up and down the course in any condition.

• ** Typical conditions: Flat water, shifty winds can be strong or light**
• Typical racecourses: Mix of random leg and windward-leeward

My local weeknight beercan series is conducted on a sheltered, narrow lake, with very shifty winds, but no current. Winds tend to be at either end of the spectrum: It’s either drifter light or wipeout windy. Because of the prevailing direction and narrowness of the lake, there’s usually a lot of maneuvers on the random-leg courses.

In this scenario we’re looking for light boats that are on the smaller end of the size range for each of the rating bands, but still retain the ability to perform in breezier conditions.

PHRF 30 to 70: Although the Henderson 30 can be a handful in bigger breeze, it’s an excellent light-air performer and reaches like a bandit.

PHRF 71 to 114: The Antrim 27 is a very fast and fun light-air performer that’s great in a breeze, so long as there’s not a lot of chop.

PHRF 115 and up: The B-25 , Leif Bailey’s original sporty speedster, is almost unbeatable under these conditions. An excellent, all-around performer that’s easy to drive around the course, and can still be found at reasonable prices.

• ** Typical conditions: Flat water, moderate winds**
• Typical racecourses: Random legs, all points of sail

My weeknight series is conducted in protected bay waters, with an average current of .5 to 1 knot, and generally flat water (with some chop at the upper wind range). Winds in the summer average 10 to 15 knots, and the organizing committee will typically run courses using government marks, requiring a mix of sailing angles.

In this scenario we want a boat with good all-around performance, especially for headsail reaches, a point of sail where many modern boats with non-overlapping headsails struggle. The 10- to 15-knot wind range is plenty to power most boats, so a very light boat, carrying a penalty for high sail-area-to-displacement ratio, will be at a disadvantage. This is particularly true in a “waterline” race, where a higher hull speed trumps maneuverability. On the other hand, a moderately light displacement boat with not too much wetted surface will ensure you’re not left out in the cold should the wind go light.

PHRF 30 to 70: The J/120 has consistently demonstrated excellent all-around performance to its typical rating.

PHRF 71 to 114: Either the Frers 41 or the J/29 masthead outboard. Both of these boats have overlapping headsails and enough power to get around the course and through the reaches. Which one is best would be dictated by local class splits. It’s generally desirable to be toward the faster end of the class.

PHRF 115 and up: The S2 9.1 was a MORC slayer in its heyday. It’s a very fast, but comfortable, 30-footer with a powerful overlapping headsail and long waterline.

• Typical conditions: Steep chop, moderate winds
• ** Typical racecourses: Windward-leeward**

The races in my weeknight series are held on open, exposed, and typically choppy water, especially in moderate winds. The summer average is 10 knots, and the race committee usually runs windward-leeward courses.

Windward-leeward races are typically won upwind and lost downwind. In this scenario we’re looking for boats that will have good light-air performance to weather while retaining the advantage downwind. We also want to look for boats with relatively fine bow sections to get through the chop.

PHRF 30 to 70: The Farr 30 is still one of the best small windward-leeward boats ever designed (owner bias aside). It’s light and easily driven, but has a fine bow that can cut through the chop when needed. Thanks to the masthead spinnaker, it excels downwind in all breezes.

PHRF 71 to 114: The J/35 has excellent all-around traits. This workhorse provides great performance in the medium breeze, and the overlapping headsail really helps drive through the chop.

PHRF 115 and up: The C&C 35 MK I is often overlooked. With its low wetted surface, overlapping headsail, and narrow beam, it’s an excellent performer, particularly in the chop. The Mark III model, which has a deeper keel and more modern rudder design, is a strong windward performer, but pays in the rating game and is typically a good deal more costly.

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How Sailboats Measure Up

• By By Jeremy McGeary
• Updated: October 17, 2012

Sailboats by the Numbers

Boat reviewers rely on numbers to describe some of the key attributes of their subjects, such as length, beam, draft, and displacement. And while judgments on interior layouts and decor are subjective, these figures describing dimensions are not. There are, however, other numbers commonly cited in spec boxes that can prove more elusive, since they attempt to put a numerical value on how a sailboat might be expected to perform while under way. The commonly used ratios are sail area to displacement (SA/D), displacement to length (D/L), and ballast to displacement (B/D). And though they’re so commonly used that a certain amount of dogma has accrued around them, these figures can, in fact, be misleading, or at least misunderstood. And the result is that a boat can be assigned attributes based on numerical values that don’t take into account how sailboat design has changed over the past several decades.

Here, then, is a look at those ratios, what they attempt to describe, and how they should be interpreted when you go off exploring new and used models. (Click to page 2 for a more in-depth explanation.)

Sail Area/Displacement (SA/D)** An automobile buff seeking a high-performance ride looks for a high power-to-weight ratio and compares the horsepower/curb-weight ratios of different cars. For a sailboat, the SA/D provides the same metric. The horsepower comes from the wind on the sails and is proportional to the sail area; a boat’s weight is its displacement (in pounds, kilograms, or tons).

Initially, the SA/D only really gives a measure of potential acceleration rates (in case any physicists are reading this), but since displacement is a key factor in the resistance a boat encounters when moving through the water, SA/D also has a bearing on potential maximum speed.

The traditional calculation for SA/D compares sail area in square feet to displacement in cubic feet. In the formula, displacement in pounds is divided by 64 (the density of seawater) to obtain cubic feet, which are in turn converted to square feet to make the ratio unit-free.

On a spreadsheet, the formula would be S/(D/64) (2/3).

Nominally, the higher the SA/D, the more lively the boat’s sailing performance. The vessel will accelerate more quickly and have the potential for higher speed. But to be able to compare boats with any degree of precision (or fairness), we have to use similar numbers. The displacement must be in the same condition, either light ship (nothing on board) or fully loaded, and the sail-area measurement must reflect the normal working sail plan. Racing boats have measurement certificates from which these numbers can be reliably extracted. The specifications provided in cruising-boat brochures might not be consistent between builders, but we have to assume they are.

Boats measured in the 1970s and the 1980s for racing under the International Offshore Rule for the most part had SA/Ds between 16 and 17, based on the sum of the mainsail triangle (M = P E/2) and 100-percent foretriangle area (100%FT = I J/2). The measurement system favored small mainsails and large headsails, and since designers of cruising boats stuck close to the IOR sail plan, the IOR value for SA/D became the yardstick. An SA/D above 17 said “fast boat,” and anything below 16 said “slow boat.”

After the IOR fell out of favor, cruising-boat design drifted away from raceboat design, and sail plans began to change. Today, many boats are designed with large mainsails and small jibs, and most builders publish a “total sail area” number that includes the standard jib (often as small as 105 percent) and the roach in the mainsail (which is significantly greater on modern boats with full-battened mainsails than on IOR boats).

These builder-supplied numbers are more readily comparable against competing models, but using them in the SA/D formula makes the boats look “faster” than older models. This is a false comparison, because the sail area used for the older boats doesn’t include the extra area in, say, a 150-percent genoa.

The table “Sailboats by the Numbers” (see page 79) illustrates this. It shows SA/Ds calculated for a selection of modern boats and boats from past eras, all about the same length, using different numbers for sail area. For each model, it shows five SA/Ds. SA/D 1 is calculated using the sail area provided by the builder. SA/D 2 is calculated using M (P E/2) and 100% FT (I J/2). SA/D 3 is calculated using M + 105% jib. SA/D 4 is calculated using M + 135% jib. SA/D 5 is calculated using M + 150% jib. The only SA/D that includes mainsail roach is SA/D 1.

Let’s look at some examples. The 1997 Beneteau Oceanis 411 has a published sail area of 697 square feet on a displacement of 17,196 pounds. That gives an SA/D 1 of 16.7 (the same as SA/D 2), which for decades was considered very respectable for a cruising boat.

In 2012, the current Beneteau Oceanis 41 has a published sail area of 902 square feet (453 mainsail + 449 jib) and a published displacement of 18,624 pounds, to give an SA/D 1 of 20.5. Wow! Super-high performance! But this is for the standard sail area, with the 449-square-foot jib (just about 100% FT and typical of the trend today toward smaller jibs that tack easily). Plug in the calculation using I, J, P, and E and SA/D 2 drops to 18.9 because it doesn’t include mainsail roach, which is about 16 percent of the total published mainsail area.

Go back to the 1997 model, tack on a standard-for-the-day 135-percent genoa, and the SA/D 4 becomes 20.7. (If we added in mainsail roach, typically about 11 percent of base mainsail area before full-battened sails, we’d have 21.4.) The 1997 boat has essentially the same horsepower as the 2012 model.

Looking at current models from other builders, the SA/Ds based on published numbers hover around 20, suggesting that designers agree on the horsepower a cruising sailboat needs to generate adequate performance to windward without frightening anyone.

The two boats in our chart that don’t at first appear to fit this model are the Hunter 39 and the Catalina 385, but they’re not really so far apart.

The Hunter’s SA/D 2 is 16.1. Its standard jib is 110 percent (327 square feet), and the rest of the published sail area is in the mainsail—664 square feet, of which 37 percent is roach!

Catalina is a little more traditional in its thinking. If you add the standard 135-percent genoa, the SA/D becomes 21.2—right in the ballpark. (It’s still there at 19.7 with a 120-percent genoa.)

The table shows that, for boats targeted at the “performance cruising” market, the SA/D numbers using actual sail area lie consistently around the 20 mark. To go above that number, you have to be able to fly that sail area without reefing as soon as the wind ripples the surface. To do that, you have to elevate stability—with broad beam, lightweight (i.e., expensive) construction, deep bulb keels, and fewer creature comforts.

Displacement/Length (D/L)** While sailboat builders and buyers are interested in displacement in terms of weight, naval architects view it as volume; they’re creating three-dimensional shapes. When working in feet, to get a displacement in pounds, they multiply cubic feet by 64, the density in pounds per cubic foot of seawater. (Freshwater boats displace more volume because the density of fresh water is only 62.4.) The D/L ratio is therefore a measure of immersed volume per unit of length—how tubby the hull is below the waterline.

According to conventional wisdom and empirical studies, the lower the D/L, the higher the performance potential. This is mainly due to wavemaking resistance being lower for slender hulls than for tubby hulls.

In the D/L formula, displacement in pounds is divided by 2,240 to convert it to tons to bring the values to manageable numbers, so D/L is displacement in tons divided by .01LWL (in feet) cubed.

In a spreadsheet, the formula would be D/(2240*(.01L)3), where D is the displacement in pounds and L is LWL in feet.

In the early days of fiberglass boats, the Cruising Club of America rule was the principal dictator of boat shapes. Because it was a waterline rule, designers kept waterlines short to keep ratings low and relied on long stern overhangs immersing to add “sailing length” when the boats heeled. Carbon fiber was available only to NASA, and boats had full interiors, so “light displacement” wasn’t really in the cards. A D/L of 300 was considered dashing, even risky. Many still-popular designs from the 1970s and 1980s have D/Ls as high as 400; see the Bounty II.

Fast-forward 40 years. Boats now have plumb bows and plumb sterns and waterlines almost as long as their LOAs—there are no rating penalties on a cruising boat. The boats’ weights haven’t changed much because, although builders try to save weight to save cost, the boats are so much bigger. The hull and deck surface areas are greater, and all that extra internal volume can be filled with furniture. The effect on D/L ratios has been drastic—just look at the table. A D/L ratio above 200 today describes a heffalump.

But do these lower D/Ls actually buy you any more speed? Yes and no.

Yes : Because speed is proportional to the square root of the waterline length. Today’s 40-footer has a much longer waterline than yesterday’s and ought to sail as fast as yesterday’s 50-footer. It might also benefit from reduced resistance due to a smaller cross-sectional area, but it also might have greater wetted-surface drag due to the longer immersed length. When sailing downwind in waves, though, the lower-D/L boat will surf more readily.

No : Because, as we saw above, the power-to-weight ratios (SA/D) of modern boats aren’t effectively any higher, and certainly aren’t in the realm that would allow our cruising sailboats to climb out of the displacement zone and plane. In most conditions, the lower-D/L boat is still trapped in its wave.

In the days of the IOR, a D/L of 250 was still pretty racy; see the 1978 Catalina 38. Today, even a D/L as low as 150 doesn’t make a boat a speedster if it can’t carry the sail area to make it so. To compete at a level with a Volvo 70, look for a D/L of about 40 and an SA/D of 65.

Ballast/Displacement (B/D)** The ballast/displacement ratio is simply the ballast weight divided by the boat’s total displacement. Since ballast is there to give the boat stability, it’s easy to jump to the conclusion that the higher the B/D, the stiffer the boat.

However, B/D doesn’t take into account the location of the ballast.

Take a boat that has a total displacement of 20,000 pounds and put its 8,000 pounds of ballast in the bilge. Now take the same boat and put the 8,000 pounds of ballast 4 feet deeper in a bulb at the bottom of a deep fin keel. Same ballast ratio (0.4), but very different stability.

When looking at B/D, therefore, we must ask about the configuration of the keel: How low is the ballast?

Stability analysis is complex and involves beam, hull cross-section, and length, among other factors, of which B/D is just one.

Since the late 1990s, builders of sailboats intended for sale in the European Union have been required to provide stability data, including a curve of righting arm at angles of heel from 0 to 180 degrees—far more information than anyone can divine from a B/D number and a much more useful measure of a boat’s inclination to stay upside down in the unlikely event (the way most people use their boats) that it exceeds its limit of positive stability.

CW contributing editor Jeremy McGeary is a seasoned yacht designer who’s worked in the naval-architecture offices of David Pedrick, Rodger Martin, and Yves-Marie Tanton and as a staff designer for Camper & Nicholson.

To read the related article, How To: Measure Sail Area, click here.

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14 Best Monohull Sailboats

Last Updated by

Daniel Wade

December 28, 2023

Monohulls are among the most popular boats in the world accounting for over 75% of the total number of boats.

This means that choosing the best monohull sailboats for your sailing adventures can be overwhelming. Fortunately, we're here to help you by highlighting the best monohull sailboats.

Whether you're an accomplished sailor or just starting in the world of sailing, a monohull boat is an ideal option for anyone who wants a true sailing experience.

Unlike other types of sailboats, the level of adrenaline that a monohull brings to your sailing adventure is almost unmatched.

It doesn't matter whether the conditions are rough , wild, flat, or calm, a monohull is the perfect boat type for anyone looking for the thrills of the sail.

Unfortunately, you might not fully enjoy the thrills of sailing on a monohull sailboat if you do not choose the best monohull sailboat for you.

While a monohull cannot compete with multihull sailboats in terms of cabin size, anchoring closer to the shore, and comfort, it should hold its own if you are planning to spend more time at the sea and in unpredictable conditions. ‍

A monohull sailboat will definitely be an ideal option if you're planning to go to more challenging places. This is exactly why you have to make the right choice when looking for the best monohull sailboat.

Over the years, we've sailed many monohull sailboats and that's precisely why we feel confident that we can help you choose the best monohull sailboats.

We've gone through various designs and launches, tested them, and sifted through many monohull brands to select the best monohull sailboats that we strongly believe should be on your bucket list.

So without further ado, let's walk you through them.

Table of contents

Best Monohull Sailboats

{{boat-info="/boats/amel-55"}}

For several decades, Amel 55 has not only been the epitome of easy downwind handling but has developed a cult-like following among sailors. It was designed as the successor to the legendary Super Maramu and brings to the fore incredible features that every serious sailor will value. From a sturdily built hull, solid guardrails to a skeg-hung rudder, watertight bulkheads, and lush bulwarks, Amel 55 is built with anything you could ever want in a perfect monohull sailboat.

And even with a list of standard features, this monohull sailboat is truly designed for those who want to live comfortably on a sailboat for long periods. It comes with superb sea berths with lee cloths, a dishwasher, crockery, an electric furling main and genoa, and several practical items that will make sailing very comfortable.

We have to admit that the design might look old going by modern standards, especially with the advent of easier sail handling systems. For example, the ketch rig design is no longer ideal and is out of fashion. But even with this downside, the Amel 55 remains a phenomenon; a legendary monohull sailboat that ticks all the right boxes in the sailing world.

2. Bavaria Cruise 46

{{boat-info="/boats/bavaria-46-cruiser"}}

Probably the most popular monohull sailboat in recent years, the Bavaria Cruise 46 is a formidable monohull sailboat that was voted "European Yacht of the Year" in 2015. Well, this shouldn't be surprising as you'll probably never find another monohull sailboat in its class that offers more comfort, more space, more luxury, and easier handling.

You can transform the boat's 3 cabins into 4 cabins by transforming the huge forward cabin into two smaller cabins in a few simple steps. In the bow, you'll find a large and luxurious master cabin that can be easily divided using an innovative Flexi-bulkhead.

Its sporty design on the exterior, lightweight composite steering wheels, and a flexible selection of wood tones makes it look so good while offering the best dimensions for both short and long trips. In essence, the Bavaria Cruise 46 is an elegant monohull sailboat that redefines modern sailboats with its clever and innovative design.

3. Hallberg-Rassy 48 Mk II

{{boat-info="/boats/hallberg-rassy-48-mk-ii"}}

Following in the footsteps of the original Hallberg-Rassy 48 Mk that was launched a decade ago, the Mk II was launched in 2014 as an updated version thanks to its modern profile, incredible hull portlights, and larger and frameless windows. This Swedish monohull sailboat is solidly built, gorgeously finished, and is famous around the world and among sailors for its kind and smooth behavior at sea.

Its center cockpit is a true definition of what comfort should entail at sea. This is a monohull sailboat that will provide you with steady sailing both upwind and downwind. It can effortlessly cover 200 miles a day and doesn't require you to be a pro sailor to be able to handle it. If anything, it offers smooth sailing and can be perfectly handled by a casual sailing couple .

In terms of additional features, this monohull comes with a large chart table, lots of stowage and space, a secure linear galley, as well as extra machinery and gear that would be of great help when out on the water. This is a well-thought-out monohull sailboat and is perhaps the best Hallberg-Rassy ever built. This boat guarantees reliability, top-notch quality, and superb resale value.

4. Catalina 545

{{boat-info="/boats/catalina-545"}}

As one of the largest monohull sailboats in the game, the Catalina 545 stands out in the way it's engineered and designed to make it a truly excellent monohull sailboat. If you're an ardent Catalina fan, you'll notice that the 545 has some of the most eyebrow-raising features in bluewater cruising.

For example, the fiberglass collar is designed all-round the top of the hull and shaped like a construction beam. This is to give the hull a more enhanced rigidity while providing a sturdy base for the deck. It's also designed with solid stanchions and cleats, as well as strong sheer rails.

This superb monohull sailboat is constructed with a set of scuppers that play a crucial role in draining near the waterline so that you can perfectly eliminate any development of streaks or strains on the top side of the boat. As far as the bow is concerned, the sprit brings to the table an essential but unique anchor roller, a self-tacking jib, and a light displacement that makes the boat quick even in light or moderate wind. In essence, this monohull sailboat is designed with simple but reliable systems that are easily accessible. Better still, it remains one of the biggest monohull sailboats around.

5. Discovery 55

{{boat-info="/boats/discovery-55"}}

Having been launched two decades ago in 2000, the Discovery 55 has unquestionably stood the test of time and remains one of the most preferred monohull sailboats for families and couples around the world. This is a well-balanced and elegantly designed sailboat that brings to the sailing world immense practicality, comfortable seating, a deep and secure cockpit, dedicated stowage, and a self- tacking jib among many other things.

If you've been on a sailboat and bruised or stubbed your toes, you simply appreciate hos the superb monohull sailboat is designed to keep you safe and secure at all times. From the grab rails and handholds to deep sinks in the galley, the Discovery 55 is designed with plenty of nifty details and the inclusion of many practical ideas.

This sailboat will probably never disappoint you. It is well-mannered, comfortable to live on for days if not months, and a true definition of modern and luxurious. 

6. Contest 50CS

{{boat-info="/boats/contest-50cs"}}

If you want a serious monohull boat that can help you extend your sailing ground with ease and perhaps without even realizing it, the Contest 50CS is the way to go. For close to two decades, this Dutch-made monohull sailboat has been a consistent performer even with its dry weight of 17.5 tons.

This monohull is designed with impeccable modern underwater sections and a completely balanced rudder. Although the in-mast furling may affect the boat's performance, this boat can still perform incredibly well without it.

The fact that this boat is designed with a mainsheet traveler and electric winches that can be easily accessed from the helm makes it an ideal boat for a small crew or if you're planning to sail shorthanded. The genoa is easy to tack and two people can easily gybe downwind under spinnaker.

In addition to having exceptional touches on the interior, you might be surprised to learn that the joinery finish of this boat is arguably among the best in the boating industry. This is a monohull sailboat that's easy to handle, well-built, and has weathered the test of time to still mix it nicely with the big boys of recent years. Well, the Contest 50CS might not be among the cheapest monohull sailboats around but its demand is still soaring even today.

7. Bénéteau Oceanis 45

{{boat-info="/boats/beneteau-oceanis-45"}}

Named yacht of the year in 2012, the Bénéteau Oceanis 45 remains one of the most popular monohull sailboats in the world and for a good reason. This is a sailboat that redefines the important themes that made the Oceanis 50 so popular in a much better way.

One of the most noticeable features of this boat is that the mainsheet is designed in such a way that it doesn't obstruct the cockpit as you tack or jibe. This just a start; the cockpit is nicely designed and will serve you just right during your sailing endeavors. This monohull sailboat comes with three or four cabins, two bathrooms, and has a larger cockpit than other boats in its class.

This is a boat that keeps up with the Bénéteau tradition of being ahead of the game in terms of innovation, attention to detail, and offering top-notch performance. Whether you're looking to live aboard or sail to the remotest of places, this gorgeous monohull sailboat has everything you need in place. 

8. Jeanneau Sun Odyssey 36i

{{boat-info="/boats/jeanneau-sun-odyssey-36i"}}

Another French monohull sailboat that makes it to this list, the Odyssey 36i is a great monohull sailboat that is acknowledged for having some excellent assets in terms of sailing as it is faster and more agile than most sailboats. This is, without a doubt, an elegant monohull sailboat that brings to the sailing world an overall melodious package in terms of its modern design, power, and capability when sailing.

Even though its hull is of modest size, this monohull sailboat offers great value as it is easy to sail, easy to moor, and dock. Its magnificent electronics, folding prop, and electric anchor winch seem to make everything so easy that you do not even need a crew to sail this boat. The hull is lively and offers good acceleration. Imagine a monohull that can clock around 6.4 knots when sailing upwind.

To be honest, the interior of this boat is still very traditional but the exterior looks quite modern. The exterior is designed like an avant-garde sailboat and looks appealing from just about every angle. In terms of performance, this boat is designed with a deeper keel, spinnaker gear, taller rig, and a much better standing and running rigging.

On the interior, the most noticeable feature is the removable dining table that can be easily removed to accommodate extra bodies. Apart from that, there is nothing complex about the cockpit and deck layout. The double-roller bow fitting is nice and it comes with an optional electric windlass. In essence, this monohull sailboat is designed with lots of features. It is good-looking and reasonably priced.

9. Gunfleet 43

{{boat-info="/boats/gunfleet-marine-gunfleet-43"}}

For many sailors who have the dream of spending most of their time sailing to exotic places, the prospects of downsizing and living most of your essentials at home can be daunting. In other words, it's almost impossible to pack all your life in a 40 feet vessel if you've lived your entire life in a 2,000 feet house. While you can't bring things like your hot bathtub to the ocean, the Gunfleet gives you the chance of bringing most of your essential onboard thanks to its immense spaciousness.

This British-built monohull sailboat is modern, sleek, but kind of feels like a classic sailboat. It comes with an efficient hull that's laid up by hand to enhance attention to detail. The reverse transom brings to the fore a three-step ladder leading to the deck and a small swim platform. It's also designed with a low coach roof and a windshield that seems to taper towards the aft of the cockpit.

Its impeccable low profile gives it a contemporary look but the center-cockpit design is the most attractive part of its design. The aft deck section is expansive and comes with excellent twin zones for sunbathing. They're divided by a skylight and a hatch that lead to the master stateroom that's located below. Its two cabins and two heads are essential if you're planning for long passages. The interior is posh and offers ample natural light.

As far as performance and acceleration are concerned, this monohull sailboat holds well. It accelerates nicely even when out of tacks since the helm is responsive no matter the point of sail. This is an outstanding monohull sailboat that has a solid feel and will most certainly boost your confidence if you're planning to go for long passages even in snobbish conditions.

10. Island Packet 35

{{boat-info="/boats/island-packet-35"}}

Designed to offer top-notch performance, stability, and comfort, the Island Packet 35 is widely known for its spaciousness, modern interior, U-shaped galley, and a vast cockpit that certainly compares to most modern 40 feet sailboats while still holding to the classic lines.

This incredible monohull sailboat is designed with a short spoon, generous spring to the sheer, and a chopped off transom. It is perfectly designed bowsprit elongates the sheerline, which essentially makes the boat appear longer, lower, and much better than it is. As far as the keel is concerned, this is a full keel that's not heavy but very moderate.

The interior of this boat will probably make you think that you're looking at a 40-footer sailboat. It's so spacious that you can use it for your liveaboard sailing escapades. It also offers notable improvements in performance and certainly surpasses some of the company's earlier models. In ideal conditions, very few boats will match the Island Packet 35 in terms of performance. This is a very stable and comfortable monohull sailboat that doesn't hold back as far as performance is concerned.

11. Bowman 40

{{boat-info="/boats/chuck-paine-bowman-40"}}

Thanks to its medium-to-heavy displacement structure, the Bowman 40 is designed to sail across open seas with ease. A modern classic, this monohull sailboat looks pretty much traditional thanks to its overhanging bow, deep-bilged, and narrow shoulders. This makes it very powerful on the waters and offers a lot easier motion during long passages.

Better still, this sailboat is perfectly stable and enjoyable since you won't be thrown about even in strong waves. It's designed with handholds within reach both above and below the deck, as well as no sharp edges to ensure that you don't injure yourself. This is enabled by the balanced hull and carefully integrated sails, as well as ample ballast that's neither heavy nor lightweight. In short, this is a solidly built monohull sailboat that will serve you diligently even when you are confronted with stormy conditions.

Honestly speaking, the Bowman 40 isn't a racing cruiser but neither is it a slouch. It has the ability to sail through the heaviest of oceans and might arrive at your destination just at the same time as other lightweight sailboats. This is, without a doubt, a sailboat that's designed to take you offshore in all weather and sea conditions. 

12. Bavaria Cruiser 51

{{boat-info="/boats/bavaria-51-cruiser"}}

Even though it is one of the largest monohull sailboats, you'll probably never notice this once you start sailing. Well, this is because it handles unbelievably so well and can easily and comfortably accommodate up to ten crew members thanks to its three cabins. To offer optimum luxury, this boat can be customized to have five cabins, which is clear evidence that it can meet various needs.

This boat isn't just about being spacious. Instead, it's designed with all functionalities to enable you to enjoy your sailing adventures. Whether you take a look at its exterior, interior, deck, or cockpit, you'll realize that every part of this gorgeous monohull sailboat oozes class. While the most striking of this vessel's interior is its enormous space, it's also designed elegantly and beautiful to ensure that you enjoy your sailing adventures.

In terms of its hull, you're getting a very agile boat that you can easily control even when the winds are extremely strong. In essence, this is a monohull sailboat that's well and generously proportioned in all aspects. It's modern, sleek, and will turn head whether at the dock or deep at sea. 

13. Wauquiez Centurion 57

{{boat-info="/boats/wauquiez-centurion-57"}}

Thanks to its exciting Mediterranean-style design and functionality, the Centurion 57 is a serious monohull sailboat that feels robust, solid, and truly marks the reincarnation of the legendary Centurion generation of luxury monohull sailboats. Designed as a racing sailboat, the Centurion 57 is thoroughbred, powerful, and impeccably maneuverable but that doesn't mean that you have to use it as a racing cruiser.

Instead, it's comfortable, luxurious, and elegant and brings to the fore everything that French boat makers are known for: class, beauty, and reliability. Its hull is unquestionably one of the most powerful and versatile. It's designed to withstand the harshest of sailing conditions .

It has a very spacious and large cockpit that's designed to afford you maximum versatility while out there. This means that you'll get lots of free space to efficiently maneuver the boat in the tightest situations and also to make things a lot easier if you're sailing shorthanded. From the electric winches to the helm position, you can easily access the transoms.

This is a monohull sailboat that guarantees calm, luxury, and comfort without compromising on performance and speed. It oozes modernity, solidity, and immense attention to details.

14. Rustler 42

{{boat-info="/boats/rustler-yachts-rustler-42"}}

If you've been looking for a monohull sailboat that combines serious performance attributes to other crucial blue water cruising elements, look no further than the Rustler 42. This is a gorgeous, fast, and reliable monohull sailboat that remains the benchmark of all monohull sailboats of its size. It not only offers directional stability but can also carry immense loads and is solid enough even for long passages.

This is a classing looking monohull sailboat that perfectly combines traditional style with modernity and innovativeness. It is not only elegant but also very stable and should be an ideal choice if you're looking for the best liveaboard monohulls.

Its spacious cabin is big enough to offer standing headroom and, of course, plenty of storage within the lockers. The hull is hand-laid using glass fiber reinforced polyester to ensure that it's solid, reliable, and durable.

In Conclusion

There you have it; the above-described vessels are the best monohull sailboats today. They are designed to enhance your sailing experience and ensure that you always enjoy your time out there on the water. Whichever boat you choose, it's essential to ensure that it's in good condition, well-maintained, and in perfect shape for your adventures.

Until next time, stay safe and happy sailing!

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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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• Aphrodite 101

The Aphrodite 101 Sailboat

The Aphrodite 101, a fractional sloop, was designed by Paul Elvstrom & Jan Kjaerulff and built in Denmark by Bianca Yachts. She is also known as the Bianca 101.

Published Specification for the Aphrodite 101

Underwater Profile:  Fin keel with Spade Rudder

Hull Material : GRP (Fibreglass)

Length Overall : 32'7" / 9.94m

Waterline Length : 26'3" / 8.0m

Beam : 7'11" / 2.4m

Draft : 5'5" / 1.7m 

Rig Type : Fractional Sloop

Displacement : 6,174lb / 2,800kg

Designer : Paul Elvstrom & Jan Kjaerulff

Builder : Bianca Yachts (Denmark)

Year First Built : 1977

Number Built : 450

Owners Association :  OTT-Yacht  

Published Design Ratios for the Aphrodite 101

1. Sail Area/Displacement Ratio:  20.8

2. Ballast/Displacement Ratio:  57.0

3. Displacement/Length Ratio:  152.4

4. Comfort Ratio:  21.6

5. Capsize Screening Formula:   1.7

read more about these all-revealing numbers...

Summary Analysis of the Design Ratios for the  Aphrodite 101

1. A Sail Area/Displacement Ratio of 20.8 suggests that, in the right hands, the Aphrodite 101 will have enough performance to leave most other sailboats of similar waterline length well astern. 

2. A Ballast/Displacement Ratio of 57.0 means that the Aphrodite 101 will stand up well to her canvas in a blow, helping her to power through the waves.

3. A Displacement/Length Ratio of 152, tells us the Aphrodite 101 is clearly a light displacement sailboat. If she's loaded with too much heavy cruising gear her performance will suffer dramatically.

4. Ted Brewer's Comfort Ratio of 21.6 suggests that crew comfort of a Aphrodite 101 in a seaway is similar to what you would associate with the motion of a coastal cruiser with moderate stability, which is not encouraging news for anyone prone to seasickness. 

5. The Capsize Screening Formula (CSF) of 1.7 tells us that a Aphrodite 101 would be a safer choice of sailboat for an ocean passage than one with a CSF of more than 2.0. 

More about the Aphrodite 101...

The Aphrodite 101 is a 9.9-meter (32.5-foot) monohull sailboat that combines performance, beauty, and simplicity. It is a fractional sloop with a single-spreader mast and a large mainsail. The boat has a fin keel with a spade rudder, and can be steered by a tiller or a wheel. The boat has a displacement of 2.8 tons and a ballast of 1.2 tons, giving it a good stability and responsiveness. The boat can reach speeds of up to 7 knots in light winds and up to 12 knots in strong winds.

The Aphrodite 101 was originally built by Bianca Yachts in Denmark, but later production was taken over by Copland Boats in Sweden and Ott Yacht in Germany. Nearly 500 boats have been built to date, with over 140 sailing on Lake Constance in Germany. 

The Aphrodite 101 is ideal for recreational sailors who enjoy racing, cruising, or day sailing. The boat is easy to handle, even single-handedly, and can cope with various weather conditions. The boat is also suitable for family sailing, as it has enough space and comfort for four people to sleep on board.

Accommodation The Aphrodite 101 has a simple but functional interior layout that maximizes the use of space. The boat has four berths: two in the forepeak cabin and two in the saloon. The saloon also has a folding table that can seat four people for dining or socializing. The galley is located on the port side of the saloon, and has a sink, a stove, and some storage space. The navigation station is located on the starboard side of the saloon, and has a chart table, an instrument panel, and some drawers. The head is located aft of the navigation station, and has a toilet, a sink, and some lockers.

The Aphrodite 101 does not have any other versions or options for the accommodation layout. However, some owners have customized their boats by adding or removing bulkheads, cabinets, or cushions to suit their preferences.

Hull and Deck The Aphrodite 101 has a sleek and graceful hull shape that gives it an attractive appearance and a good performance. The hull is made of fiberglass reinforced plastic (FRP), which is strong, light, and durable. The hull has a white gelcoat finish with blue stripes along the waterline and the sheerline.

The deck of the Aphrodite 101 is also made of FRP with a non-slip surface. The deck has a large cockpit that can accommodate up to six people comfortably. The cockpit has two lockers for storing sails, lines, or other equipment. The cockpit also has an outboard motor bracket on the transom for mounting an auxiliary engine.

The mast of the Aphrodite 101 is deck-stepped and made of aluminum alloy. The mast has one set of swept-back spreaders that support the shrouds and the forestay. The mast also has internal halyards that run through exit boxes on the mast base.

The above text was drafted by sailboat-cruising.com using GPT-4 (OpenAI’s large-scale language-generation model) as a research assistant to develop source material; we believe it to be accurate to the best of our knowledge.

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Marine Displacement | Calculations and Formulas

Marine displacement is a critical concept in naval architecture and marine engineering. It refers to the volume of water that a ship or boat displaces when it is floating, which is equal to the weight of the vessel. Understanding and calculating marine displacement is essential for the design and operation of ships. This tutorial delves into the formulas and calculations associated with marine displacement, focusing on length, breadth, draft, and block coefficient. This concept is pertinent to fields such as Naval Architecture, Marine Engineering, and Ocean Engineering.

Example Formula

The primary formula used to calculate the displacement of a ship is based on its physical dimensions and block coefficient. The block coefficient is a dimensionless number that describes how closely the shape of a ship resembles a rectangular block.

• Length : is the length of the ship (in meters or feet).
• Breadth : is the breadth of the ship, often referred to as the beam (in meters or feet).
• Draft : is the vertical distance between the waterline and the bottom of the hull (in meters or feet).
• Block Coefficient : is a dimensionless value typically ranging between 0.6 and 0.85 for most ships.

Impact on Society

The development of marine displacement calculations has had a profound impact on society and technological advancements. By accurately calculating the displacement, engineers can design ships and marine vessels that are stable, efficient, and safe. This has enabled the construction of larger and more advanced ships, which have been central to global trade, defense, and exploration. Additionally, this knowledge is crucial in rescue operations, preventing maritime accidents and environmental disasters.

Real Life Application in Industry

Marine displacement calculations are widely used in the shipping industry. For example, in the design phase of cargo ships, engineers need to determine the displacement to ensure that the ship can carry the intended cargo without compromising stability or safety. Knowing the displacement is also essential for compliance with international maritime laws and regulations. Furthermore, in the oil industry, displacement calculations are crucial for designing oil tankers that can transport large volumes of crude oil across oceans efficiently.

Key Individuals in the Discipline

One of the key individuals in naval architecture and marine engineering is William Froude (1810-1879). He was an English engineer and naval architect who played a vital role in the development of ship design. Froude's work in hydrodynamics and his establishment of the first experimental fluid mechanics laboratory have been fundamental to understanding ship displacement and ship hull design.

Interesting Facts

• The largest ships in the world have a displacement of over 650,000 tonnes. This is equivalent to the weight of around 5300 blue whales!
• The conceptof marine displacement was crucial in World War II, where the design of different types of naval vessels, including submarines, battleships, and aircraft carriers, played a significant role in the outcome of naval battles.
• The principles of displacement are not only applicable to ships but also to submersible vehicles and even to floating structures like oil rigs, playing a critical role in offshore engineering.

Understanding marine displacement and its associated calculations is vital for the design, construction, and operation of ships and marine vessels. The formulas for calculating displacement are fundamental tools in naval architecture and marine engineering. The advancements in this field, spearheaded by individuals like William Froude, have had a profound impact on global trade, maritime defense, and exploration. As maritime technology continues to advance, the principles of displacement will remain central to the safe and efficient design of marine vessels.

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China launches anti-dumping probe into eu pork, pig by-products.

Move in line with WTO rules, in contrast to EC’s protectionist tariffs: experts

China's Ministry of Commerce (MOFCOM) on Monday announced that at the request of the Chinese domestic industry, it will launch an anti-dumping investigation into certain pork and pig by-products originating from the EU, stressing that the move is in line with relevant Chinese laws and regulations as well as WTO rules.

Notably, the announcement came just days after the European Commission (EC), the executive body of the EU, announced last week that it would impose additional tariffs of up to 38.1 percent on electric vehicles (EVs) imported from China starting in July, though MOFCOM did not mention the EC's announcement.

In a notice on Monday, MOFCOM said that the China Animal Agriculture Association on June 6, on behalf of the Chinese pork and pig by-products industry, submitted an application for an anti-dumping investigation into certain pork and pig by-products originating from the EU. After a review of the application, MOFCOM determined that it meets the requirements for launching an investigation in accordance with the relevant laws.

The investigation starts on Monday and will be completed by June 17, 2025. The duration could be extended by six months in special circumstances, according to MOFCOM.

An official with the Trade Remedy and Investigation Bureau of MOFCOM said that the investigation was launched after the domestic industry filed an application. The investigation authorities reviewed the application in accordance with relevant Chinese laws and regulations and in compliance with WTO rules, and deemed that it met the conditions for launching an anti-dumping investigation.

"The investigation authorities will conduct the investigation in accordance with the law, fully protect the rights of all stakeholders, and make objective and fair rulings based on the investigation results," the official said.

The announcement of the probe came just days after the EC announced that it would impose additional provisional tariffs of between 17.4 percent and 38.1 percent on EVs from China, which prompted harsh criticism from Chinese officials as well as industry and business groups. Chinese officials have repeatedly vowed to take all necessary measures to defend the legitimate rights and interests of Chinese companies.

The move also followed an exclusive report in the Global Times on May 25, in which a business insider said that relevant Chinese industries were gathering evidence, as they were planning to apply to competent authorities to launch an anti-dumping investigation into imports of certain pork from the EU. On Thursday, a business insider told the Global Times that relevant Chinese industries had formally filed an application for an anti-dumping investigation into certain EU pork products.

The investigation could have major implications for the EU meat industry. In 2023, China imported $6 billion of pork, more than half of which came from the EU, Reuters reported on Friday. Spain and France are among the EU's top exporters of pork to China. In 2023, Spain exported 6.04 billion yuan ($832.4 million) worth of pork to China, the Netherlands' pork exports totaled 1.86 billion yuan and France's exports reached 1.07 billion yuan, according to the General Administration of Customs.

Stark contrast

While MOFCOM did not mention the EC's recent announcement in the notice, some Western media reports on Monday suggested that the Chinese probe was a "tit-for-tat" move against the EC's move. However, Chinese experts highlighted the stark contrast between the Chinese probe, which was launched at the request of the domestic industry in line with WTO rules, and the EC's move was launched without an application from relevant industries in the EU, and the investigation process was unfair, unobjective and in potential violation of WTO rules.

Cui Hongjian, a professor with the Academy of Regional and Global Governance with the Beijing Foreign Studies University, said that starting in 2023, there has been a significant uptick in the EU's exports of certain pork and pig by-products to China, which warrants an investigation into its pricing factors in compliance with WTO rules.

"As for the EC's investigation, there was no application from the EU industry, and the EC took the initiative. This actually shows that the EC is increasingly viewing economic and trade issues through a so-called security and political lens, which is completely different from a reaction based on market conditions," Cui told the Global Times on Monday, noting that such a shift toward geopolitics has jeopardized normal economic and trade cooperation between China and the EU.

Chinese experts said that if the EC moves ahead by collecting additional tariffs on Chinese EVs, China will take countermeasures to defend its rights and interests. While the EC announced the additional tariff rates on June 12, it will not start collecting the tariffs until July 4, which appears to have left some room for "discussions with Chinese authorities."

"There will be countermeasures against the EC's move, as Chinese officials have repeatedly vowed to take all necessary measures to safeguard the legitimate rights and interests of Chinese companies," Bai Ming, a research fellow at the Chinese Academy of International Trade and Economic Cooperation, told the Global Times on Monday.

Bai said that China and the EU could resolve trade disputes through dialogue and consultations, but "the EC has destroyed the atmosphere of cooperation" with its illegal, protectionist move against Chinese EVs.

In addition to the anti-dumping investigation into certain EU pork and pig by-products, the Global Times has also learned from a business insider that relevant Chinese industries are preparing evidence, as they plan to apply to competent authorities to launch an anti-subsidy investigation into imports of certain dairy products from the EU.

Moreover, China is internally moving ahead with a procedure to raise the temporary tariff rate on imported cars with large-displacement engines, Yuyuantantian, a social media account affiliated with China Media Group, reported last week. A Chinese auto industry insider previously told the Global Times that China should consider raising the temporary tariff rate on imported cars with engines larger than 2.5 liters - a move that could have a major impact on imported vehicles from the EU.

Cui said that China's countermeasures will focus on sending the EU the signal that if it chooses the path of a trade war, it will be lose-lose for both sides.

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