# Vertical Windmills...

Discussion in 'Boat Design' started by cstretten, May 26, 2007.

1. ### Guest625101138Previous Member

I have a vague recollection of a video of this very simple device going to windaward but cannot find it.
http://www.main.org/polycosmos/silicbar/sailscrw.htm

I did make a model windmill boat many years ago that progressed slowly to windward.

I have since improved my knowledge of foils and prop design and have derived the following relationship for the boat going directly into the wind.

Air Prop Load = Hull Drag / (% + Vwind /Vboat * % -1)

% is the overall efficiency of the two props and the mechanical efficiency. Really good props could each get efficiencies of 88% and two precision right angle drives would have a combined efficiency of 94%. Hence % in the above equation would be 0.73. So if we want to do 10knts in a light weight displacement boat with a hull drag of 200N in 8knts of wind the force on the air prop will be:

Fap= 200 / (.73 + 8/10 * .73 - 1)
= 200/ 0.314
= 637N

Basically you need to make a high efficiency air prop that gives 5.5kW at the shaft in apparent wind of 18knts connected through right angle drives to a high efficiency water prop that produces 837N thrust at 10knts.

I can give you the prop designs and hull design if you want to build it. I also can recommend some competively priced right angle gearboxes.

I expect you would need variable pitch on the air prop to make it practical and enable optimisation off the wind.

Rick W.

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### TroutcatcherJunior Member

Wingsails are a much better choice than a windmill. A much larger sail area can be reached whitout any mechanical complexity at all.

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### Otter 33Junior Member

Vertical Windmill Fan

I think that windmills may never replace sails for racing sailboats. However, there are a couple advantages of windmill propulsion that I have not seen in this thread yet.

1. Most boats spend 99% of their time not sailing... this is just the reality of boat ownership. A windmill on a boat, with electrical power transmission, could produce clean power whenever the wind blows. This could be stored onboard in batteries for "power sailing", or it could be grid intertied at a marina to "pump" power into the power grid.

2. There are advances being made in the efficiencies of cyclodial "vertical" windmills that use servos to control the angle of attack of each rotating blade. This comment is more in the what if category... please bear with me. There could be a way to efficiently construct a freestanding vertical windmill by using a very large bearing assembly on the cabin top roof, each blade would be load bearing, creating a stable tripod that would not need a strong carbon spar in the center. This structure would also be aeronautically efficient in that almost all of the structure would create lift.

3. A lot of people are turned off to sailing because of the complexities of sail power. There are also many older sailors that convert to the dark side of power boating when they feel they can no longer handle the stresses of sailing. A vertical windmill (or an automated wing sail) would be a point and go boat that would appeal to broad range of people. In ten years from now, the price of fuel may be so high that most families will no longer be able to afford a 2 nautical mile per gallon power boat.

4. ### Guest625101138Previous Member

Downwind Prop

I have made an upwind prop boat at scale level and have done numbers on a light boat that can carry me. What I did not realise is that you can sail faster than the wind down wind. Now this really gets my attention.

Here is a video of a road version:

If you cannot work it out then this test on a running machine helps understand how it works:
http://www.ayrs.org/MOV05703.mpg

This explanation is also very good:
http://www.ayrs.org/DWFTTW_from_Catalyst_N23_Jan_2006.pdf

I built an air prop for one of my boats but damaged the tips in testing when the wind gusted to about 15kts:
http://www.rickwill.bigpondhosting.com/Air_Prop.jpg
The blades flexed and started clipping the vertical shaft.

It was impossible to slow it by holding the shaft once it got to speed so I am confident about the power output. The blade is based on a high L/D foil section - MA409. However these foils only have a thickness ratio of 7% so a bit too flexible.

My own prop testing and the little DWFTTW wind cart have given me some encouragement to get on and make a stronger air prop. I will go up to a 10% thickness section.

Rick W.

5. ### xaraxPrevious Member

Vertical axis wind turbines / Voith-Schneider propelers

Any comments? That is obviously the most natural and symmetric solution to the propulsion AND transmission problems.

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### WindmasterSenior Member

Hi. I wish people would use the right terminology here. "Prop" is short for propeller - which is something that pushes you along, therefore it is used under the water to push the boat. If you are gathering energy from the wind you are using a "turbine" not a propeller. I presume Rick Willoughby is referring to an air-turbine in his post not a propulsion device.

7. ### Guest625101138Previous Member

In your terminology the downwind situation would be an air prop and a water turbine as the air prop provides the thrust and the water turbine delivers energy to the air prop. That is why it can go faster than the wind downwind.

This terminology may actually make it easier to understand the principle of operation. Most people find it difficult to grasp the concept but it is a simple matter of gearing.

Rick W.

8. ### Guest625101138Previous Member

A further note on props and turbines.

In the upwind situation the part in the air becomes a wind turbine driving the water prop. So both twisted foils can be a prop or a turbine depending on the wind direction and the gear ratio between them.

To be really pedantic we should talk about the twisted foil in the air and the twisted foil in the water. This avoids any assumption about what is driving what and what is thrusting where.

Rick W.

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### WindmasterSenior Member

Windmill Boat Model Videos

--------------------------------------------------------------------------------

I have just completed posting my radio controlled model videos on Youtube.
They show two of my models. A trimaran which can sail in ANY direction relative to the wind, (its driven by a wind-turbine with an underwater prop). Also shown is a very basic wind-turbine landsailer model on the beach.
Check out this url at: http://www.youtube.com/watch?v=GzNq3aEyP2w Many in this discussion seem to think that sailing directly into the wind is a bit marginal and rather difficult. I think this will show it's very easy and no big deal! I'm looking for comments and criticism so don't hold back. Honesty is always appreciated!

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### WindmasterSenior Member

Windmill Boat Videos

I have just completed posting my radio controlled model videos on Youtube.
They show two of my models. A trimaran which can sail in ANY direction relative to the wind, (its driven by a wind-turbine with an underwater prop). Also shown is a very basic wind-turbine landsailer model on the beach.
Check out this url at: http://www.youtube.com/watch?v=GzNq3aEyP2w Many in this discussion seem to think that sailing directly into the wind is a bit marginal and rather difficult. I think this will show it's very easy and no big deal! I'm looking for comments and criticism so don't hold back. Honesty is always appreciated!

In respect to this particular discussion, and as someone who has done a lot of experiments in this field. I don't think vertical axis machines can ever match horizontal axis ones. The hoped for advantage is that they don't have to be orientated to the wind. They would be the perfect answer if they worked well enough. But they dont.

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### yipsterdesigner

looking good Peter!
saved attached pic a few days back comparing one raked turbine blade against a wing (bottom right)

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### yipsterdesigner

yeah i'm crazy and what you proofed is allready quit an achivement that has a lot of potential too
Malcolm Tennant shows a turbine concept on one of his bigger cats
forces sound safety and other details to be worked out i guess

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### jkittelJunior Member

I've been very interested in the idea of using wind or solar for propulsion, in part becuase of the independence to oil. However conditions won't always be favorable for wind power, and the sun is only available during the day. Batteries remain a poor solution for storing energy, and I do not want to sacrifice stability and sea-keeping in return for a lighter and faster craft.

I now see that flywheels are the answer. The attention that the seakeeper gyroscope is getting is well warrented, as it allows ships to have a low draft, a light weight, AND stability. For a while now power companies have been using large flywheels for storing electricity for use during peak hours, or to provide backup power.

A large flywheel normally used for terrestrial applications, placed at the bottom of a mono or trihull boat would be able to provide far greater energy storage capacity then batteries for the same price. In addition it would be able to function as a massive gyro, keeping the ship far more stable in rough weather then any other ship of the same displacement. With the flywheel's ability to rapidly discharge, a high speed semi-displacement mode might even be possible.

In the end, it all depends on HOW the flywheel is connected to the hull. Without the gyroscope setup like the one seakeeper uses the owner would not be able to control how much of the flywheels kinetic energy is used up to keep the boat stable. This would likely lead to the ball bearings wearing out rapidly as well.

http://www.seakeeper.com/gyro.html

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### GuillermoIngeniero Naval

I agree with Xarax. Leo's proposition seems to me also the most interesting way to go.
Cheers.

Interesting:
Latest Developments in Voith Schneider Propulsion Systems

Edited: I remembered there is a thread on a similar matter at these forums. Here it is:

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### Leo LazauskasSenior Member

For those who are still interested, I've scanned in some papers I wrote when I was young and foolish...

"Experimental Verification of a Mathematical Model for Predicting the Performance of a Self-acting Variable Pitch Vertical Axis Wind Turbine",
B.K. Kirke and L. Lazauskas,
Wind Engineering, Vol. 17, No. 2, 1993.