Wing Sails on Proas!
Thanks Skip for the encouraging words, but wait there’s more. I’m considering pivoting the cam off center to leeward rather than just sliding fore and aft to get closer to the wind. This is where I’m in over my head, any comments or suggestions would be welcome.
Best regards, Roy
Thanks Skip for the encouraging words, but wait there’s more. I’m considering pivoting the cam off center to leeward rather than just sliding fore and aft to get closer to the wind. This is where I’m in over my head, any comments or suggestions would be welcome.
Best regards, Roy
You’re welcome for the words, they were deserved.
Will have to think on the pivoting rather than sliding, have been content at this stage with the idea that more displacement of the cam results in more angle of attack and as appropriate at this stage of development, all the bits are adjustable.
Philosophically I’m a little leery of having more asymmetry than necessary.
Skip
Thanks Skip, it’s just an option that was obvious when I started with the longer radius pivot that results in next to nil asymmetry. I’m looking at the Eisenlohr notched plate adjustment like he uses to set the angle between the two elements to act as “throttle” setting.
Best regards, Roy
Below is a sketch for an endplated, tail controlled wingsail configuration. The aim is to get the centre of effort lower, whilst maintaining good efficiency.
What I have tried to do is to incorporate the tail fins (two in this case) into the endplate to increase the effective span as much as possible. The result is that you can use a main wing with a relatively low aspect ratio without sacrificing too much efficiency. The downside is the relatively high centre of gravity of the rig and the added drag of the endplate itself.
That looks like a really neat design, Mal.
The downside is the relatively high centre of gravity of the rig and the added drag of the endplate itself.
But the whole rig is lower, no? And the endplate adds efficiency where the wind is strongest.
The intention is that the whole rig is lower, to lower the centre of effort, although if you prefer you could keep the rig the same height and benefit from the higher L/D.
The endplate adds efficiency by increasing the effective span. I’m not sure how the wind velocity near the end plate affects the magnitude of the improvement, but you might be right. There is an assumption in this design that you would design the deck near the foot of the wing so as to maximise the end plate effect there as well.
Mal.
Mal,
Looks like you have choose a tuff nut to crack. I like the end plates but would go lower with the counter weight.The Harbor Wing comes to mind but carbon fiber $$ scares me. What do you think about this whole arrangement mid wing. I’m still looking for a good simple solution for this problem.
Best regards, Roy
Roy,
You could put the counterweight lower down. However, earlier in the thread someone (Tom Speer I think) mentioned that if you put the counterweight higher up, it can be lighter. This assumes that the counterweight is used to damp out oscillations due to rolling and that the boat does not sail heeled over significantly. If the boat does sail at large heel angles (monohull), the counterweight needs to balance the weight of the tail regardless of it’s vertical position, whereas if the boat sails essentially upright, the counterweight only has to balance the roll induced oscillations.
On a multihull which doesn’t sail at large angles of heel, weight aloft is not a problem like it is on a monohull. As long as the centre of gravity (CG) of the rig remains to windward of the centre of buoyancy (CB), the weight of the rig actually contributes to stability. So for a Pacific proa, the wing rig would best be mounted far enough to windward of the vaka so that the CG of the rig was still to windward of the CB of the vaka when flying the ama at the optimum heel angle.
Mal.
Both the autonomous Atlantis and Peter Worsley’s catamaran are, I believe, fully counterweighted. A fully counterweighted wing could also be mounted on a mast which was canted to windward.
Does that endplate become an uncontrolled sail as the boat heels?
Both the autonomous Atlantis and Peter Worsley’s catamaran are, I believe, fully counterweighted. A fully counterweighted wing could also be mounted on a mast which was canted to windward.
Although I understand the logic behind using a smaller counterweight higher up the rig, I admit that I am skeptical about using an unbalanced wing rig on a boat. I can see how it could work on a land yacht, but boat motions are larger, lower frequency, and the roll centre will change depending on the wave pattern at any given time. I think an un-balanced counterweight arrangement might have to be tuned for a particular wave pattern and boat heading, meaning that it won’t work so well in other conditions. As you mention pr1066, if the boat (or rig) is heeled, then you will need a balanced counterweight arrangement regardless, unless the tail is light enough that the wind alone can support it’s weight, and that would depend on the wind strength.
Mal.
Does that endplate become an uncontrolled sail as the boat heels?
That’s almost another topic in itself.
I think in this case if the heel angle is small, the end plate is rigid and the end plate remains roughly perpendicular to the boats axis of travel, it shouldn’t be a problem. There will be a small lift component along the wing rotation axis when the boat heels.
In the past I have experimented with kites mounted on at the mast top on models that sail with significant angles of heel, which showed that there can be some benefits in suitable conditions. It’s extra sail area with no added heeling moment.
Mal.
In the past I have experimented with kites mounted on at the mast top on models that sail with significant angles of heel, which showed that there can be some benefits in suitable conditions. It’s extra sail area with no added heeling moment.
Mal.
This is a lot like winged keels, isn’t it? Love your endplate setup, in general. I think if you ran the numbers, you might be able to build a shorter wing, with a higher L/D and a net lower (or at least equivalent) center of gravity, to a bigger taller plain rig. Nice concept.
Dave