average sailboat speed

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Average Speed of a Sailboat

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What are the average cruising speeds for a 30-40' displacement and semi displacement hull sailboat?  

6-9 knots depending on conditions and the boat.  

If you are talking about averages over the course of a long sail, I think that is a bit high.  

As was said, this is a tricky question. But, for consideration, a well-sailed cruising boat on passage will make about 75-80% of her hull-speed potential over a 24-hour period. Example: Waterline length: 34' Hull speed: 5.8*1.4 = 8.2 knots 80% of hull speed: 6.56 knots 24-hour run: 157.4 nm Mine does a bit better, averaging 6.7 knots or 160 nm per day on offshore passages on a 34.2' waterline (27K lbs displacement, 42' LOA). Obviously, there are many variables. But, the "80% rule" often comes close, I've found. Bill  

I'd agree with what our esteemed moderator has said. Low, about 4 knots. High, about 6 knots. Subject of course to weather being higher or lower than usual. With GPS, you'll know your speed over the bottom. With a wood or stryofoam chip, timed from bow to stern, you'll know what your speed through the water is. They you'll know if you're sailing in current. But our estimates on the web don't mean much to you on the water, you'll have to take both an over-ground and a through-water speed, then compare to see if you are in a current and if so what its direction is.  

All these guestimates also need to take into account the point of sail and the wind speeds vs the different designs. I suspect there's little difference between "displacement" and "semi-displacement" designs. However a boat that can outright plane in certain conditions will have a much higher potential threshold with the right wind speed, course and sea state. JRP's estimates for overall average speed look good.  

To figure out how long it will take to get somewhere, figure 5kts as a average. When bragging at the local sailing bar, figure the hull speed plus 10%. Unless you are in the trade winds, then figure on 75% of hull speed depending on the skipper, condition of sails, the load of the boat multiple times a random number derived from adding up the letters of the words "silly question". Sorry, had to do it.  

chucklesR said: To figure out how long it will take to get somewhere, figure 5kts as a average. Click to expand...

I measure average speed in quarts of rum per hour. Is that incorrect?!?  

What are the average cruising speeds for a 30-40' displacement and semi displacement hull sailboat? Click to expand...

Thanks for all the feedback. Everyone's answers was exactly what I was looking for.  

One variable no one mentioned is where you are cruising. When we crossed Lake Michigan years ago, we used to figure 5 knots as minimum speed, because the run was about 60 NM where we usually crossed, and we always liked to do it in the 7 AM to 7 PM time frame. If the wind fell off and our speed dropped below 5 knots, we would start the engine. However, when crossing an ocean, you really don't want to start the engine because you don't carry enough fuel to run the engine for a couple weeks!  

Gunny!! Yer back!! Where ya been??  

Hey CamJ Just living life. Merger-ed myself out of a job, took up selling health and life insurance. That took sometime to get the license and learn selling skills. I still get out in the bay. Have more time to go thru the board since I work from a "home" office, (read bunny slippers, coffee, computer, and telephone.) (Ok I really don't wear bunny slippers).  

I'll chime in on the 5 kts average. That's what I use when cruising under conditions that don't allow for long term use of engine when the wind dies. The times you are bombing along at 8 kts are offset by the times when you are drifting in circles. And of course all bets are off it you are going to windward in light stuff.  

I use a 6 knot average when I am planing a cruise. I find it easier to do the time, distance and speed calculations in my head when I use 6 knots. I aways late though.!!!  

Of course you all realize that the amount of marine growth on the bottom makes a difference also. Ultra clean bottom 6+ kts Average clean bottom 5+ kts grassy bottom 4+ kts botanical gardens on the bottom 2+ kts Now how close am I??  

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Speed of an average sailboat

Discussion in ' Sailboats ' started by Hebron Watson , Jul 13, 2007 .

BarendGrobler Junior Member

You mention a couple of sailboat books. I am in fact a powerboat designer by trade (fast ferries etc) but I am becoming more and more interested in sailing boats. I know there are quite a lot of books listed on the forum that deal with the topic of sailboat design, but their descriptions are very short and simple so one can’t really get an idea of the contents or the quality thereof. Can you perhaps suggest any books? I’m looking for literature (preferably one single book) covering most arias of the design (hull-hydrodynamics as well as sail design and aerodynamics and stability; structural design I don’t need). I am more interested in multi-hulls, particularly tri’s. It can be complex, I don’t mind; as I said, I have a boat design background. Thnx! Leke dag!!! Barend  

Trevlyns Senior Citizen/Member

Hi again Barend I think your best single choice would be Principles of Yacht Design by Lars Larsson and Rolf E Eliasson. I have a copy myself and am always referring to it. It basically is about the full design process of an imaginary yacht, the YD 40 (Yacht Design 40 footer). Here is a list of the chapters 1. Design Methodology 2. Preliminary Considerations 3. Hull Geometry 4. Hydrostatics and Stability 5. Hull Design 6. Keel and Rudder Design 7. Sail and Rig Design 8. Balance 9. Propeller and Engine 10. Rig Construction 11. Hull Construction 12. The ABS Guide 13. Layout 14. Design Evaluation Mine is a first edition (1994), but I think more recent ones also cover power boats and planning hulls as well. Chris White’s book The Cruising Multihull is not as detailed technically but is an absolute must if you’re into multihulls (like I am!) It still covers virtually every aspect of design and construction but obviously applied to catamarans and tri’s (separate chapters on each). I couldn’t be without that one either. I’d say start with those two; I’m sure they’ll cover everything you could think of. Sure you’ll find them at bigger or specialist book stores back home. If not, then both titles are also available on Amazon . Good luck and happy reading  

PAR Yacht Designer/Builder

Gutelle's "The Design of Sailing Yachts" will be helpful, considering your back ground.  

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Great stuff!!! I'll get those ASAP!!! Thnx for the advice; from those chapters of Principles of Yacht Design it certainly seems like the ideal starting point. Have a good one!!! Lekke dag!!! Barend  

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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.

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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)