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

[MPraamsma]

Too bad you guys can't knock back a couple of beers over the web, otherwise I think you would be seeing eye-to-eye...

[Windmaster]

Originally Posted by MPraamsma

Too bad you guys can't knock back a couple of beers over the web, otherwise I think you would be seeing eye-to-eye...

Very true - I think we need to let the matter rest for a while

[Windmaster]

Originally Posted by Externet

Hi all.

http://www.main.org/polycosmos/silicbar/sailscrw.htm

Built one years ago, tried a few times always on uneasy conditions of too much wind and rough sea. Someday perhaps soon will find proper conditions and a matching propeller to report behavior.
Design is not good to build a boat (that must head in all directions); just to demonstrate the 'directly against the wind' possibility.

The ruler is 15cm, overall length is 85cm, shaft is 8mm ⌀ hollow carbon fiber, aft turbine is 42cm ⌀. The 'fore' 25mm nut is just weight to keep the pulling propeller submerged; the tilt angle varies with wind force and by sliding the 'float' position to avoid splashing. Am a believer

Miguel

Miguel

I noticed that you did it the opposite way round from David Santos. He used quite a large area aluminium blades for his wind turbine and a model airplane prop for his water prop. You seem to do it the opposite - you used a model airplane prop for the wind and a model boat prop for the water.
Did your's work ok? I really think his would have worked a little better than yours.
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[Windmaster]

Appropriate to this thread is a new prop I recently made for one of my direct-into-the-wind models. It worked very well and pulled the boat to windward ok.
(comments welcome)

[backyardbil]

Originally Posted by Windmaster

Appropriate to this thread is a new prop I recently made for one of my direct-into-the-wind models. It worked very well and pulled the boat to windward ok.
(comments welcome)

Excuse me mentioning it, but isn't this a little crude?
Seems amazing that something so simple should work as you say? Why didn't you use a "proper" water prop? I'm mystified!

[Windmaster]

Yes, it is rather basic. Deliberately so. Allow me to explain.
When I first started making these boats to go directly to windward I stuck strictly to theory and made the blades of my windrotor to an exact aerofoil (US airfoil) section, and used model aircraft prop underwater. They worked well. Later, another experimenter who sometimes posts in this forum, Richard Miller, sent me a picture of a model boat he had tested and it did not have aerofoils on the blades, simply flat plates. He assured me that the boat worked well, so to test this I also made a boat with a flat plate blade section and to my surprise it worked well also.
Then the idea occurred to me - how simple and "crude" can a system be and it still have the efficiency ratio to go directly into the wind that powers it! Consequently, that is how that water-prop came into being. The boat had flat plates for blades both on the air-rotor and the water-prop. It worked!
These results seem to go against the generally held belief that all the complicated paraphenalia of theory was necessary to obtain even a marginal advance against the wind.
The successful model described above was also very simple in that it was of the single shaft variety that is the wind-rotor (at the back of the boat) and the water-prop were on a common sloping shaft which left the wind-rotor in the air and the water prop beneath the surface forward of the boat.
Interestingly enough, there are videos on Youtube of a model aircraft experiment where the "camber" is removed from the wing leaving a flat plate aerofoil and the aircraft performs just as well - if not better.
So it may be, as U. Norberg famously has said "Aerodynamics is not an exact science"!
Attached is a picture of another model boat, not made by myself or Richard Miller that also uses flat plates.
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[Guest625101138]

The difference in efficiency between a flat plate propeller and a thin foil propeller of similar plan shape is about 10%. You do not need very high efficiency to get something to go directly into the wind.

If you want to get performance that will match a sailing skiff then you want efficient foils for the propeller and turbine blades.

Also you can have perfect foil shapes and, if they do not suit the operating conditions, they will have poor efficiency. Most boat propellers are well shaped foils but they often achieve an efficiency of no more than 60%. Under certain conditions a flat plate would do better if sized to suit.

If you look at the Aeolus racers you get an idea of relative performance:
http://www.youtube.com/watch?v=UuffDMkHhEo&eurl
He is some more description.
http://www.ewec2009proceedings.info/...esentation.pdf
The Stuttgart team averaged about 18kph over the 1000m on their best run. The Flensburg Headwind trike was very slow. I think it needed to be pushed most of the time once on the flat. The trike pilot in one of the video clips said it will take him an hour to finish. I cannot find actual results for any but the first three: in order Stuttgart, DTU and ECN. The Stuttgart team achieved 64% of the measured windspeed

So, as I have often pointed out, it is not difficult to make something that goes directly into the wind. It is another matter to have something that does it in an effective fashion.

Compare this vehicle with the Aeolus racers:
http://www.youtube.com/watch?v=TRFRQXPtXTs

Rick W

[Windmaster]

Originally Posted by Rick Willoughby

If you want to get performance that will match a sailing skiff then you want efficient foils for the propeller and turbine blades.

The Flensburg Headwind trike was very slow. I think it needed to be pushed most of the time once on the flat. The trike pilot in one of the video clips said it will take him an hour to finish. I cannot find actual results for any but the first three: in order Stuttgart, DTU and ECN. The Stuttgart team achieved 64% of the measured windspeed

So, as I have often pointed out, it is not difficult to make something that goes directly into the wind. It is another matter to have something that does it in an effective fashion.

Compare this vehicle with the Aeolus racers:
http://www.youtube.com/watch?v=TRFRQXPtXTs

Rick W

Point One
Presume you mean here the direct upwind performance of a sailing skiff vmg by tacking.

If you mean that, then the way to (theoretically) achieve that is by a direct analogy.
On the sailing skiff, by definition, the sail moves at exactly the same speed as the boat 1:1.
If we were using a wind-turbine powered boat then each blade of the turbine, which we can conveniently call a rotary sail, is likely, through the gearing, be moving at a greater speed than the boat. It may, in fact be moving as fast as, or faster, than the sail on the sailing skiff. But, because of the gear ratio, the boat must be moving slower.
If if could be arranged that the rotary sail moved the same distance as the boat, then indeed the boat would move directly upwind as fast.
However, if the gearing was arranged in this way (1:1) then there would be a shortfall in force because the rotary sail would not be of the same area as the skiff's sails.
If the rotary sail area was increased to the same as the skiff then you would have a completely analagous situation between the skiff and the rotary sailing boat.
However, this would probably be very difficult to arrange in practice.

Point Two
In the case of the Aeolus racers, the Flensburg Headwind Trike probably suffered somewhat by being much lower to the ground, and because of the wind gradient, was not receiving as great a windspeed. This would partly, although maybe not entirely, account for its poor performance.

Point Three
According to the Greenbird website, the record of 126mph was achieved in a windspeed of between 30 and 40 mph.
At this speed the apparent wind to the craft would have been nearly directly ahead (as shown in the video), but because of the differential between the speed of the craft and the speed of the wind, its heading relative to the true wind would have been more than 90 degrees. That is to say partly downwind.
As the sailing speed of any directly driven sailcraft is increased, the less close to the true wind it can sail (because the apparent wind draws ahead).
So it wouldn't be fair to compare the performance of Greenbird with a direct-into-wind sailing craft in this case, unless you tested Greenbird's vmg directly against the wind using tacking. If we had information on how Greenbird would perform in this regime then it would be a fair comparison and it's likely that it would be a good deal less than 126 mph.

Point Four
The theoretical speed limits for direct-upwind sailing boats may seem low, but it needs to be borne in mind that the average speed overall of traditional ballasted monohull sailing boats is also low. So the average sailor who is used to this kind of sailing would probably not be unhappy with these direct-into-the wind speeds.
As an example, the average overall speed for Robin Knox Johnston's first solo circumnavigation around the world was only 3 knots!
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[Guest625101138]

Originally Posted by Windmaster

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As an example, the average overall speed for Robin Knox Johnston's first solo circumnavigation around the world was only 3 knots!
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The modern tris do the loop in under 60 days. The world has moved on and sailing boats are faster and more reliable through design and development.

A slender hull with efficient turbine and propeller coupled through a low loss CVT will outperform a sailing skiff under certain conditions. It will have a lot of similarities to the Stuttgart Aeolus racer rather than the Flensburg Headwind trike.

Depends on your objective. You may be satisfied with wowing the ill informed bystanders that you can make a boat that will go directly into the wind. It is a different matter if you want to make a boat the will make certain progress from point A to B under varying conditions.

Rick W

[Windmaster]

Originally Posted by Rick Willoughby

The modern tris do the loop in under 60 days. The world has moved on and sailing boats are faster and more reliable through design and development.
Rick W

According to Wiki
The record for single handers round the world westabout (against prevailing winds) in a monohull is 122 days by Jean Luc van den Heede at an average speed of 7.4 knots. This was in 2004.
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[Guest625101138]

Originally Posted by Windmaster

According to Wiki
The record for single handers round the world westabout (against prevailing winds) in a monohull is 122 days by Jean Luc van den Heede at an average speed of 7.4 knots. This was in 2004.
...

Not sure what this has to do with your previous post.

I have attached an image of the current solo circumnavigation record holder. The leader includes the average speed.

Rick W

[Windmaster]

Originally Posted by Rick Willoughby

Not sure what this has to do with your previous post.

I have attached an image of the current solo circumnavigation record holder. The leader includes the average speed.

Rick W

Firstly, I was talking about ballasted monohulls. This is not a ballasted monohull.
Secondly, I was talking about sailing against the prevailing wind - that is East to West. This is West to East (downwind).
You need to read the posts carefully.

[Guest625101138]

Had another test of the turbi-prop boat today.

Wind was really a bit light and variable today to get the best from it. There was not much difference in speed on any point of sailing because the apparent wind to windward was not stressing it while the apparent wind downwind was too little to get the speed up.

Best speed today was again 5kph. My son took some video and I have attached a clip.

The control was very good. As long as there was some breeze I could go wherever I wanted within the limitations of the poor turning circle with my pedal boat rudders.

There ware two lasers on the lake as well. They could make way all the time and in the gusts were quite fast. In steady wind of good strength, say 20 to 30kph, I might be able to just better them in VMG going directly up wind. On all other points they would kill it.

The turbine is a good diameter and pitch for this. It needs a larger diameter prop and CVT to get the best from it.

Rick W

[Windmaster]

Originally Posted by Rick Willoughby

Had another test of the turbi-prop boat today.

Wind was really a bit light and variable today to get the best from it. There was not much difference in speed on any point of sailing because the apparent wind to windward was not stressing it while the apparent wind downwind was too little to get the speed up.

Best speed today was again 5kph. My son took some video and I have attached a clip.

The control was very good. As long as there was some breeze I could go wherever I wanted within the limitations of the poor turning circle with my pedal boat rudders.

There ware two lasers on the lake as well. They could make way all the time and in the gusts were quite fast. In steady wind of good strength, say 20 to 30kph, I might be able to just better them in VMG going directly up wind. On all other points they would kill it.

The turbine is a good diameter and pitch for this. It needs a larger diameter prop and CVT to get the best from it.

Rick W

It's working as predicted. On into-wind videos the "wavelets" give a greater impression of speed than it really is. This is also apparent on my own model videos.

On a boat such as this with very small air drag and beam to length ratio for highest speed then the biggest hindrance to its speed "directly against" is the drag of the rider himself.
If, for instance, a competition was established for boats similar to the Wind Energy event for land craft, no doubt the rider would be enclosed in a streamlined fairing.
It might be interesting to send this boat off without a rider, "directly against" with a tether to measure the "bollard pull", and then try the same thing with the rider aboard to measure the difference in thrust.
However, as the wind is constantly varying you would only get an approximate answer.
I have to say that in my own opinion its working the same as my own boat of this type, and this indicates that whether a high-speed rotor is used or whatever speed rotor is used that, if adjusted correctly, you will get satisfactory performance.

It is obvious that a Laser would have a much better performance on all points except "directly against" (Even amongst boats of a similar type, the Laser is reckoned to be one of the fastest).
Think of it this way. It may well be that in a crosswind the individual blades of the wind turbine are travelling much faster than the Laser's sail, but because of the way they are geared to the boat the boat must necessarily be going much slower.
If you could arrange a 1:1 ratio then the turbi-prop craft might well rival the Laser. However, there might not be much point in that since the Laser already has a 1:1 ratio (the sail moves at the same speed as the boat), and this would not be a suitable setup for a turbi-prop boat going "directly against".

Regarding the possibility of developing such a boat as a practical craft as against a one-off proof of concept craft such as this is:
Due to the fact that this is built hastily from available parts, it does not have, and would need to have, variable pitch wind-turbine blades which would allow the rotor to be feather and in consequence, would allow a design of rotor head which would find the wind automatically rather than having to use manual control to turn the rotor to a "no thrust" position, this would also relieve the pilot of having to consider the wind direction constantly as well as steering the boat. My 1995 design had these features.
Also, I feel that a low-speed wind-turbine option would be preferable for the following reasons:

1.
Safety; with a tip speed of (for example) only 1, the blades never travel faster than the windspeed and therefore danger to the operator and any bystanders/other boats is much reduced.

2. From experience, I find that blades and rotating parts do not have to be perfectly balanced, in fact, I have never paid any attention to balance and never found it necessary.

3. Due to the slow rotation speed, bearings can be simple.

4. Blades are not subject to the high stress levels that high-speed blades suffer.
Therefore they can be made considerably lighter.

5. With tip speed on only 1, half the lift force is used to turn the turbine with only 50percent adverse thrust, therefore relieving the stress on the drive system.

6. Tests show that low speed windblade rotation works as good, or even better than fast-spinning blades even without any blade twist. Untwisted windblades are much more simple to make than twisted blades therefore costs are reduced.

7. Whatever the windspeed, the wind-turbine won't overspeed or run out of control.

Practically, I think that a wind-turbine powered boats will not be truly practical and safe without the rotor diameter being less than the beam of the boat. If it is more, there is always the possibility of chopping up trees, boats or other people. Obviously, because of the greater beam width, this is easier to achieve on a catamaran or trimaran than a monohull.

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[srimes]

re laser vs. Rick's: To me the obvious reason that the dingy is faster is that it's harvesting energy from a larger area. Any idea of the difference?