I'm Hoping Someone Can Check These Statistics.

I don't know what equipment they were using at that time or how they were checking at low speed. It's very difficult to get a feel at those speeds. You're sampling flow which is easy when you have a gallon per minute flowing but when it's only 7/1000th of a gallon then it's difficult unless you do it for a longer time than they do in a test. Note also they were dealing with a brand new boat and engine. Their emphasis in the test is not usage at idle. I've been around a lot of boats and read thousands of boat tests.

I just searched to find another test with usage per hour like that. A 40 hp Mercury at 2.9 knots on a Bass Buggy uses 0.4 gph. Even a 190 hp Mercruiser at 600 rpm (2 knots) uses 0.7 gph. I cannot find any inboard at any rpm that comes under 0.7 gph. I found a 225 hp VW with 0.7 gph at 4.7 knots and 720 rpm. I'm not saying the numbers in the charts are impossible, just that I've never seen similar and never seen it in a real application. A 250 hp Lugger uses 1.2 gph at 1000 rpm.

The conversion from engine HP to fuel per hour is simple math. A really good marine diesel engine has an efficiency of around 60%. A gallon of diesel oil has around 140,000 BTU worth of energy in it. converting horse power to watts is similarly easy. The problem is installing the wind turbine onto the boat. It's super easy to install a 6KW wind turbine on land, the sort of thing you can have a teenager do in an evening. If you tried to install that 6KW generator on a boat small enough to go 7 knots on 8 horses worth of engine output a wind strong enough to make the generator work that hard is going to blow the boat over, maybe even blow it over completely and dunk everyone on board into the water.

Stability calculations are something you CANNOT ignore on a boat under any circumstances. Every boat design discussion should revolve around stability calculations. If you are building a canoe it's possible to get a feel for it and build a working canoe with no education or calculations, just based on copying what others have done. If you buy a production boat they had a naval architect with literally years of intense schooling using computers way more powerful than the computers that sent us to the moon working on them. Every year backyard boat builders destroy countless hours of work or get wrecked and need to be rescued or even die at sea because they didn't pay attention to the non-trivial task of establishing and maintaining stability.

If you look at the energy required to deliver HP to the water the turbine has to be collecting more energy than that, and since it is collecting it from the wind you are being pushed by the wind at least more than that. in order to not die, you have to either be in a craft that can handle being flipped by the wind or be in a craft that can handle having that kind of force applied to the end of a stick that goes 40' up in the air. That is not trivial to calculate. And a monohull that can handle that kind of dynamic load is not going to be able to perform anything like 7 knots with 6KW of power driving it forward, not by a long shot.

* too late to edit. Probably two evenings to set up a wind turbine at home. Concrete needs time to set.

That is not enough information to do the calculations, but I suspect that it isn't nearly enough. If you have a wind turbine that is that low you risk killing someone with the blades. Additionally you are going to be paying a big performance penalty due to the interference you get from the shockwave off the blade bouncing back up off the deck, and from the much lower windspeeds at the water surface, and it is going to be very unpleasant to be that close to those spinning blades of death because of the barotrauma.

You actually have to know what the hull is shaped like to figure it out. Absolute best case scenario for initial stability for a monohull is a barge. 22,000 lbs on a barge 40' long and 14' wide is going to be about 9.6 cubic meters of total displacement (cold salt water has a specific gravity of about 1.035) or about 7.25" of draft. If we assume that you've gone with a lead bulb on a short keep and moved the center of gravity down below the deck of the boat at deck level (which is extremely generous) and we look at the righting lever we first start with the center of buoyancy. Since we are giving you the superior barge shape we have a lovely right triangle to work off of, and the center of buoyancy is going to be at h/3 from the right corner. I ran the numbers for various angles of heel to figure out how far that 10 metric tonnes of mass would get you in terms of a righting moment and I figured out that it levels out around 15 degrees of heel at 20 meter tonnes; this is fine because your turbine is going to stop working long before you start running it at 15 degrees of heel. Well if you have it dangerously low like you are planning the center of effort is going to be at 4.877 meters above the deck, meaning that you can have a force equivalent to 4.1 metric tonnes at rest, or 5.4 horsepower if you go through several inefficient steps and assume 100% efficiency ( a wind turbine is marvelously efficient from an economic sense, but when it's lateral load you are worried about, it's going to be in the 70's peak).

That is really the highest level of performance you can get out of a simple monohull that is 14' wide after I made several assumptions in your favor that were wildly unrealistic. The ride on that thing would be positively terrifying, even though you would be looking at less than 3 knots of speed (because the hullform has a lot of wetted surface area). You could probably go faster downwind (because the wind drag and the push force from your prop would be in the same direction and because you have a better righting moment if your long access is with the wind rather than your short access) but it is unlikely that you would outperform someone with a sail.

I am not an NA, I can do some of the calculations because I paid attention in physics and calculus class and because my father was a boat builder and I read some of his books on the subject (the one he wrote and the several he purchased over the years). I can't do these calculations with the speed of someone more practiced and the specialized software tools required. But really look into multihulls. The most critical requirement for your application is initial stability and nothing matches a multihull for initial stability. I think that the gentlemen who made the catamaran we talked about earlier put a lot of thought and effort into his design, and had a lot of highly qualified professional help. I suspect that they settled on a multihull for a reason, and that that reason is probably the same as my reasoning for suggesting one. If you don't go down the multihull route you are talking about using extremely expensive and complex composites and complicated systems like canting keels and drop foils to develop the righting moment you need to keep your rig working at all, and for what it would cost you to build this beast that goes 4-5 yachts you could built a gazelle that can plane at 14 knots and hire a professional crew to sail her for you (with you on board should you wish) for the rest of your life.

I normally associate the word barotrauma with a change in pressure not a change in velocity.

Maybe you should read some more books.

Myth Alert

That would be a "really good marine diesel" indeed. The highest available today is just over 50 percent and that engine is a very large slow speed 2 stroke.

While it might seem like "simple math" it is definitely not a simple matter to map efficiency of an installed marine diesel installation across its power output range.

Only when used in shore based power plants that recover heat (combined cycle) does thermal efficiency approach 60 percent. Most of the engines used on "yachts" of the size people here talk about probably don't achieve better than 40 percent even when operating at a peak efficiency point and we will probably see a Mr. Fusion installation on a yacht before we see a combined cycle plant.

For some reason yacht designers completely ignore heat recovery techniques to make the boat more efficent.

The builders also provide some substantial opposition to anything different to what they have done before. They will cite costs, weight, loss of range, extended delivery times and the old nugget less Owners space. They especially thrive on this last one while consuming all available storage spaces with technical things.

A particular favourite seems to be to fit switchboards and equipment smack bang in the middle of any space they can rendering it useless for anything else.

I am not singling out any particular yard here either, they are all as bad as each other at this practice.

Small house or village sized windmills are super common in Alaska, I grew up within sight of a windmill dealer and have stayed in cabins powered by them. Barotrauma is the word I used because it's the word I meant. There is a shockwave off of the blade tips and it can hurt you even if the blade itself doesn't touch you, it does so by rapidly changing the pressure in such a way as to damage your tissue ... barotrauma.

Marmot. My impression was that an appropriately sized diesel engine can get 60% of the energy in the tank into the shaft if it's really at the top end. I think that losses further on down the line are to be expected. I'll be sure to update my position in the future, thanks.

In the end I think that what matters most in this application is how wind capture ability translates to horsepower, and how horsepower translates to movement. I was mostly trying to get past a question about something that isn't even really a pertinent topic for this application.

It would be helpful to have the following issue of that magazine to see if they posted any corrections to the data - very common for errors and omissions in boat tests.

I looked up a 3116 Fuel Map and at 1200rpm, was getting data at 1.8 - 2.0 gph, while the "test" states 0.8gph, seriously doubting their accuracy.

If it sounds too good to be true, then.........

I'm thinking engineering is more a science than an art.

It's got art and science to it. Coming up with clever solutions is an art, making sure they aren't too clever by half is science.

I really mangled that second paragraph on my long post. I went back to cut some of it out because I started writing before I ran all the numbers and I didn't rectify the grammar and for that I am sorry.

What I was saying is that I assumed for the same of argument that it was a flat square barge, because that is the shape with the most initial stability. I figured out how deep it would be with that much displacement. I then assumed there was a ball of lead on a keel that brought the center of that mass right down to deck level. From there I used the square shape of the barge to figure out the center of buoyancy and used the center of buoyancy to figure out how much force the hull would apply to right itself at various angles (I made a stability curve). Then I looked at how much energy you could get out of a magical 100% efficient turbine 16' up off the deck (which I set as the center of mass) without tipping the boat over.

I can understand wanting something self righting, but a wind turbine is going to need an extremely high initial stability, and high initial stability and self righting don't often go hand in hand. There are strategies and devices to right a catamaran that has capsized. They might be worth investigating if you are particularly worried,

The difficulty a lot of engine mounted flow meters that feed the ECM's have is the lack of temperature compensation which can create quite a difference between what is actually burnt and what the computer sees as being burnt.

The early electronic 3412's were particularly bad examples of the factory flow monitoring