# Windmill or Wind Turbine- powered boats: how many are out there, and are they viable?

Discussion in 'Projects & Proposals' started by Duma Tau, Oct 9, 2006.

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### WindmasterSenior Member

Here is the gearing system I devised for my "mark II" boat.
I used a cycle derailleur. It worked well, but I didnt test it much. In use, I found when I changed gear it did not have much effect on boat speed, just changed the speed of the windrotor.
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2. ### Guest625101138Previous Member

If you go back a few posts you will see I mentioned the Coanda effect. This is the term given to the attachment of flow over a curved surface - taking the name of the experimenter who observed it. You will find description here:
http://en.wikipedia.org/wiki/Coandă_effect

With hulls there is even a more interesting phenomena than the attachment up a curved hull. If you look at the pressure distribution near the transom of a planing hull the pressure is lower than atmospheric pressure so the hull is being forced down at the stern. This is due to the water actually accelerating backwards behind the hull trying to fill the trough behind the hull.

Intuitively most think the pressure at the transom is higher than atmospheric but not so.

The lesson is that blind faith in what you read or were taught is not sufficient. You need to test the wisdom or otherwise by your own observations. You do not need to be very bright to realise the "joined-up" theory is nonsense because a flat plate will generate lift. You do not need a curved surface. If you have ever carried a piece of ply in a bit of a breeze you would experience this.

Rick W

3. ### Guest625101138Previous Member

Peter
Was this with variable pitch as well?

For me the advantages would be:
1. Easier starting. I would gear low initially so the turbine spins easily to get into an efficient Reynolds number.

2. In low wind I could make headway because with lower gearing you can tolerate lower efficiency.

3. In moderate wind I could creep the gearing higher to get the highest possible speed as there is a slight increase in efficiency as it speeds up. The hull drag eventually limits this but my hull has relatively low drag.

4. Reaching I could alter gearing a bit higher to get better speed.

5. Going down wind I could alter gearing significantly higher even to the point of powering the air propeller from the water turbine. This gets to the possibility of exceeding the windspeed downwind.

So I see lots of opportunity and my high speed 2-bladed turbine would benefit more than a low speed multi-bladed turbine.

If you read the Ventomobile blog you will see they used bicycle gearing to keep the weight low. They blew it up at the end of the first day. This gets back to the power transfer capability as the speed increases. It is a much more severe limit than you get with ordinary sails. The ECN vehicle had much heavier gearing but the extra weight made it slower overall.

I am certain my turbine would blow up bicycle stuff. The problem would come at the instant of changing gear because the turbine would be continuing to power.

Rick W

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### WindmasterSenior Member

Yes it was with variable pitch. As you know, my system was low speed/low adverse thrust, so it coped with the power ok, and the gear changes were surprisingly smooth.
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### Leo LazauskasSenior Member

I'm not sure what you mean by that. Depending on the shape of the airfoil, and the angle of attack, the flow can separate from the surface in a turbulent mess, sometimes it can reattach, and sometimes it can form vortices, and bubble-like structures and many other complicated flow patterns.

If you are looking for simple introductory discussions of flight, you might find something of interest at the NASA web site. There was a lot of activity there during the recent anniversary of the Wright brothers achievements, IIRC.

As to the sinkage and trim of hulls, I'd say it is the combined effect of the distortion of the free-surface of water and the dynamic forces and moments induced by the passage of water over the hull. And it doesn't necessarily have to be a "highly-rockered" hull. If you are really nerdy, the equations for the dynamic forces and moments induced by the flow over thin hulls are given in a report at:

At higher speeds, the dynamic force reverses direction, and then we might have "true" planing (or some other ill-defined state). In the infinite speed limit, the planing equation is almost identical to the lifting surface equation of classical aerodynamics.

You might have seen references on boatdesign.net to Savitsky formulas. These empirical formulas are very widely used in planing calculations because the numerical solution of the so-called planing equation is extremely tough. Some progress has been made for hulls with planforms that are made up of straight edges, but curved planforms can create problems.

Aerodynamic analogies (e.g. arguments from the behaviour of airfoils and finite aspect wings) aren't always completely inappropriate or inadequate in describing some hydrodynamic phenomena, but free-surface effects complicate the situation enormously. So, yes, you could think of the hull being pulled down into the water because it acts like an airfoil, but only a little bit.

I am fairly pessimistic about our ability to solve to engineering accuracy many fundamental hydrodynamic problems. For example, I have an interest in trying to calculate the lift and drag of a simple flat wing with a circular planform. Although an exact solution is known, it is not easy to get better than about 4 decimal places using commonly used computer techniques. It may seem it has very little to do with hydrodynamics, or your original question, but if we can't solve fairly simple aerodynamic problems, then we have little chance of success when we include a free-surface and ambient waves. Using techniques and arguments that work for airfoils or wings hasn't helped all that much yet as far as I can tell. In short, I'd be wary of pushing your airfoil analogy too far.

All the best,
Leo.

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### WindmasterSenior Member

I think there is an insurmountable problem here. You would never be able to get identical wind conditions in different places at different times. Even in the same place you get local variations (that's why sailing races are so interesting).
I would favour a competition of models, simple and cheap, that even teenagers and poor people could take part.
The only rule being the diameter of the windrotor.
It could be, for example, the diameter of the "windspinner" model's rotor.
If released at the downwind end of a pond these models automatically find the wind and end up at the upwind end of the pond. It would be a simple race of who would get to the upwind end first. You couldn't get a truer test.

In the interests of fairness, I am at the moment trying to make a two blade high-speed windrotor version of "windspinner" with the same rotor diameter so I can compare it with the normal 8-blade version. But I am a little stuck as to what water prop to use.
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### MPraamsmaJunior Member

Rick

A few years ago, a friend asked me if I could convert his boat to electric drive. The boat was an Angelman conversion of a WWII lifeboat, so the hull was pretty heavy (around 4 tons with deck and mast and sails). The original engine was a 7 HP BMW diesel, and the prop was about 8 inches in dia, and was cut down from a bigger prop. When I installed the electric motor, it had so much power at low RPM you could hear it cavitating, but pooped out at high RPM. When I changed the prop to a much larger high pitched type it really worked great, almost giving you whiplash when it took off, and produced considerable thrust at low RPM. Even though the electric motor was only 3 HP, it performed better than the diesel, which only ran well once it got up to speed.

8. ### Guest625101138Previous Member

The boats should be in line with what you proposed originally as your objective when you set out - a boat that can carry a person along a river without the need for constant tacking.

There are Guinness records set all the time in different locations. It reduces the cost of competing.

The angled shaft is not ideal for high aspect blades as it creates some nasty forces but does not alter efficiency too much. I would consider using a spring wire shaft that could be flexed into an 'S' shape but it requires roller bearings otherwise the shaft drag would be intolerable.

If I was making a model boat I would go for the highest pitch model plane prop I could get for the diameter for the turbine and select a propeller about 1/4 of the diameter and 1/3 of the pitch of the turbine if available otherwise the highest pitch available.

Turbine something like this:
http://www.hobbycity.com/hobbycity/..._15x13_/_381_x_330mm_Poly_Composite_propeller
Make sure the lift surface is facing backwards.

Propeller something like this or a bit bigger:
http://www.hobbycity.com/hobbycity/...duct_Name=GWS_EP_Propeller_(DD-3030_82x76mm)_

Rick W

9. ### Guest625101138Previous Member

I have tried a few electric drives. I got 6kts from a 59g motor on the V11 boat using about 250W. I bought the motor for a model but decided to see what is could do on a boat that can carry a person.
http://www.boatdesign.net/gallery/data/500/V11JE_10kph.wmv
The motor is miniscule compared with the belt drive. It has a 12:1 reduction in two stages. I used a 350mm prop to get high efficiency. It is a model plane prop. The efficiency of a propeller or turbine is strongly related to the power for the swept area, smaller better, and the aspect of the blades, higher better. Most of my blades look similar to model plane props or are model plane props.

Typical boat props are lucky to get 60% efficiency whereas I can approach 90% in the things I am working on.

I have a couple of Mars motors that are rated at 4.5kW on 48V. I will be setting up a drive system using this early next year. I made an electric outboard with one of the Mars but did not like the drag from the leg.

The electrical parts are developing rapidly making an electric system easy to do and relatively cheap. Even lithium batteries and solar panels are coming down in price.

Interestingly I do not think there is a proven MPPT turbine controller for the size of turbine I am building. Hopefully this gap will be bridged soon.

Rick

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11. ### Guest625101138Previous Member

Rob Denney sent me a video clip of a brief documentary of his turbi-prop Iroquois catamaran that I have attached.

Rob achieved 6kts to windward in this boat so has done considerably better than my pedal boat conversion.

I am looking for a nice breezy day to do my last mechanical test before going electric.

Rick W

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### WindmasterSenior Member

That's a very interesting film, but it does point out that this kind of design is rather frightening and a bit of a monster. In fact, if I remember rightly Rob Denney himself has admitted this later in other forums.
As you know, I'm working on a low-rotor speed version, and I don't believe it's necessary to have a rotor diameter greater than the beam of the boat. You would certainly expect something of this size to go faster than a smaller setup.
My tests of two-bladers against multibladers suggest that they are about equal given constant wind strength, but in a real-world situation, where the wind is constantly varying and you have gusts and lulls, the multiblader windrotor version can pick itself up and start sooner than the two-blader, which either does not self start, or is very slow to start. This is something I had not thought of until I actually tested the two together on the model pond. It's obvious really when you think of how much "sail" area the multiblader has compared with the two blader. This is the reason yachts have to put so much sail out to catch light airs.

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### megsaniJunior Member

Wind-powerd boat

Dear Windmaster,

I am new to this forum. So please excuse if this post falls outside the category.

I am building a prototype SWATH fishing boat with a total tonnage of 20T. Initially I plan to power it using diesel-generating set (with electricity driven propeller motors) combined with wind power (for other electricity uses). My questions are:

[1] has anyone actually used A SWATH boat for fishing? I have searched and found no answers yet. The only reason I can think of is the draft as it may not be suitable in shallow waters and berthing issues.

[2] is it practical to use wind-power for the underwater propellers as well? Your experience seems to indicate "yes"

[3] what cruising and max speed would be achievable for my type of boat? I know this is difficult as it is based on boat design, weather and sea conditions and wind conditions throughout the year. Just to get some ideas.

[4] I am based in Malaysia. Supply shops for boat enthusiasts are practically non-existent. Can you point to stores that provide affordable construction materials for my boat?

[5] Are there funding institutions that may provide for this kind of venture?

Your help is great appreciated.

Thanks.

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### Ad HocNaval Architect

megsani

Welcome to the forum.

If your boat is going to be roughly 20t, this means roughly 10tonne per tube.
This equates to around 15m length and a draft around 2m. The size of tubes will not allow your drive to be installed in them so this shall be on the deck. So deck spaces become a premium.
In addition using diesel-electric drive, whilst in principal sounds ok...is way way too heavy for this application. The numbers wont stack up.
Addiontally, SWATHs are very draggy hull forms. They are the best hull form for seakeeping, but very draggy.
Lastly, SWATHs hulls are constant draft vessels and very sensitive to small additions of weight. Therefore, you would need to build in a load of reserve buoyancy (which means your hull must be bigger) and lots of additional high power water pumps, (more than normal) to balance your boat when fishing and with a catch. This adds even more weight and complexity.
So, for just 20T, you wont get very much at all....larger yes, this size, no way!

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