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Wing Sails on Proas!

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Hey, why don’t we make a thread just for wing sail discussion?

Great idea, Mike.

[ Edited: 05 January 2014 09:05 AM by Editor ]

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tdem - 02 January 2014 08:20 PM
Skip - 30 December 2013 08:00 PM

Peter Worsely’s circular cam

This cam sounds interesting. I’m having no luck on the internet, could you explain what it does?
-Thomas

Here I go hijacking one of Chris’s threads again wink

The circular cam at neutral is concentric with the pivot axis of the wing-sail.
The cam is made so that it can slide fore and aft along the axis of the boat.

There is a parallel arm follower around the cam pivoted on the axis of the wing-sail.

Add linkage back to the tail plane and that’s it.

The attached drawing is from first geometrically correct done today (since you asked) for the Broomstick, distance back to tail-plane shortened for clarity.

Flap operation not shown, still a lot of noodling to do for the whole deal ....but it is truly elegant as far as I’m concerned. Peter has been gracious in permitting individuals to use his patented idea freely but I plan on donating something to the cause when the time comes just to help keep karma in alignment.

Cheers,
Skip

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I’m not sure I’m getting it.

I thought that the purpose of the whole shebang was to keep the tailplane trimmed the same way, or not at all, no matter what the angle of the wing to the boat.

The centered cam satisfies the “not at all” requirement.

But if the pivot for the follower is anchored on the wing, when the wing turns relative to the boat the tailplane will trim more and more as the wing rotates clockwise with the cam slid all the way to the left, until just after its perpendicular to the centerline of the boat.

What gives?  Which part aren’t I seeing?

thanks,
chris

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Luomanen - 04 January 2014 05:18 PM

I’m not sure I’m getting it.

I thought that the purpose of the whole shebang was to keep the tailplane trimmed the same way, or not at all, no matter what the angle of the wing to the boat.

The centered cam satisfies the “not at all” requirement.

But if the pivot for the follower is anchored on the wing, when the wing turns relative to the boat the tailplane will trim more and more as the wing rotates clockwise with the cam slid all the way to the left, until just after its perpendicular to the centerline of the boat.

What gives?  Which part aren’t I seeing?

thanks,
chris

You’re right on both counts.

With the cam centered the whole shebang is feathered no matter what direction the wind is coming from.

When the cam is “throttled” in either direction the relative angle of incidence (and drive) will vary from zero when the wind is dead ahead (or astern) to a maximum with the wind directly on the beam.

Consider (gasp) tacking. That’s pretty much exactly what you want to happen. As the boat turns thru the eye of the wind drive and drag fall off to almost zero headed into the wind and automatically pick up thrust as the apparent wind starts to come from the opposite side of the boat.

For shunting all that’s required is to slide the throttle from one direction to the other. The whole shebang (I like that phrase) rotates around and automatically feathers thru the middle of the shunt if you time your slide just right.

Proas are supposed to be (in my mind) low drag relatively high speed craft with most of your time spent with apparent wind fairly well forward where lift/drag ratio are relatively important. I think there’s a lot of merit to the deal so I’m planning on playing with the idea a bit. Not sure it’s a viable or best answer to a lot of conditions but would be fun to find out.

As I said in previous post there’s a lot of noodling to be done, I’ve got my linkages/cam direction bassackwards (I think) and the geometry needs massaging plus the whole area of flap actuation needs investigation.

Hope that helps, I’ll try to spend some more time on the details this next week,  too damn cold to work outside on the boat.

Cheers,
Skip

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Thanks for the explanation and diagrams. It’s certainly very clever! Would the sail trim properly with the wind from behind? Or is the idea to go fast enough to avoid downwind courses?
-Thomas

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tdem - 05 January 2014 02:48 AM

Thanks for the explanation and diagrams. It’s certainly very clever! Would the sail trim properly with the wind from behind? Or is the idea to go fast enough to avoid downwind courses?
-Thomas

I don’t know but hope to find out, apparently most fast multi’s already tack downwind and in my own experience the proas I’ve been involved with suck downwind.

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Hi Skip,

I think the drawings as you have them are correct - with the tail angled the right way to give lift on the main wing in the right direction. If you don’t want to cross over the control rods (cables?) for the tail then you could put the pivot for the square stirrup towards the leading edge of the wing. This would also help the counter-balancing a (very wee) bit.

As far as I can see, the only, trivial, drawback to the design is that you can’t get underway if the wind is dead ahead or astern since moving the cam doesn’t move the stirrup. For all the times that is going to happen you can carry a paddle…  :o)

Peter

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pr1066 - 05 January 2014 09:45 AM

Hi Skip,

I think the drawings as you have them are correct - with the tail angled the right way to give lift on the main wing in the right direction. If you don’t want to cross over the control rods (cables?) for the tail then you could put the pivot for the square stirrup towards the leading edge of the wing. This would also help the counter-balancing a (very wee) bit.

As far as I can see, the only, trivial, drawback to the design is that you can’t get underway if the wind is dead ahead or astern since moving the cam doesn’t move the stirrup. For all the times that is going to happen you can carry a paddle…  :o)

Peter

You’re right (I think) about pieces moving in the right direction. But you would get more movement of the follower if “forward” involved moving the cam backward and the link to the tail plane stayed one one side of the whole shebang.

The drawback regarding getting underway occurs on almost all saildriven craft. Reaching up and manually moving the wingsail would be analogous to backing a jib and probably easier. I always carry a paddle and usually a spare.

Skip

PS
Thanks Editor for moving the thread

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The cam system does seem to be ingenious and I can see it’s application on a tacking boat, whereby it automatically tacks the flap as you turn the boat through the tack. For a shunting proa, however, I would still prefer a constant flap angle system. The advantage of this is that if the hull goes past head to wind, the sail still heels the boat in the same direction although the drive force will now be “backwards’ rather than “forwards”.

Mal.

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Mal Smith - 05 January 2014 05:27 PM

The cam system does seem to be ingenious and I can see it’s application on a tacking boat, whereby it automatically tacks the flap as you turn the boat through the tack. For a shunting proa, however, I would still prefer a constant flap angle system. The advantage of this is that if the hull goes past head to wind, the sail still heels the boat in the same direction although the drive force will now be “backwards’ rather than “forwards”.

Mal.

Hmmmm hadn’t thought about that.
On the one hand there’s some goodness in short tacking a shunter (touched on in the Peruvian Proa thread).

On the other hand a constant flap angle does make a lot of sense in some other respects.

Gripping hand I came to this wingsail thing as an unwashed neophyte seduced by the simplicity of that circular cam, which is looking like it may be reasonably easy to implement. As of yet there is still a small insistent voice that mutters “no reefing? you must be mad.”

Skip

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“Gripping hand I came to this wingsail thing as an unwashed neophyte seduced by the simplicity of that circular cam, which is looking like it may be reasonably easy to implement. As of yet there is still a small insistent voice that mutters “no reefing? you must be mad.””

Yes it is so counter-intuitive that there is this almost emotional revolt against it!
It can’t possibly be true! It is almost in the league of a government keeping a promise. History says, “These things just don’t happen!”

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Theoretically a feathering wingsail should be OK as long as:

a) it doesn’t oscillate when feathered and

b) it has a low rotational inertia so that it can react fast enough to a change in wind direction so that the momentary heeling force due to a windshift is not enough to overcome the rolling inertia of the hull.

Regarding the cam, I think a constant flap angle system may be even easier to implement. My solution would be to mount the wing on a stub mast, which would have a vertical push rod running up the centre of it and out through the top of the stub mast. The vertical push rod can the be used to actuate a 90 degree bellcrank (inside the wing) which then actuates the flap via a horizontal pushrod.

Mal.

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This small video may help to understand the mechanics of the system…

http://www.youtube.com/watch?v=jGo4bRHI22o

And this one shows it in action on an RC catamaran.

http://www.youtube.com/watch?v=AArllt2TRZo


Cheers,

Laurent

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Mal Smith - 05 January 2014 08:18 PM

Regarding the cam, I think a constant flap angle system may be even easier to implement. My solution would be to mount the wing on a stub mast, which would have a vertical push rod running up the centre of it and out through the top of the stub mast. The vertical push rod can the be used to actuate a 90 degree bellcrank (inside the wing) which then actuates the flap via a horizontal pushrod.

I’d be concerned that in the event of something breaking or malfunctioning the vertical push rod would drop into a position that gives full power just when things are going haywire already. One of the benefits of the cam system is that the controlling hardware is close to deck height and accessible in an emergency.

Peter

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I wasn’t totally kidding about the explosive charge to jettison the rig!  A bent push/pull rod or blown bearing could be a disaster.

Or maybe the explosives are just a security blanket….which is a funny thing to say….

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pr1066 - 07 January 2014 05:28 AM
Mal Smith - 05 January 2014 08:18 PM

Regarding the cam, I think a constant flap angle system may be even easier to implement. My solution would be to mount the wing on a stub mast, which would have a vertical push rod running up the centre of it and out through the top of the stub mast. The vertical push rod can the be used to actuate a 90 degree bellcrank (inside the wing) which then actuates the flap via a horizontal pushrod.

I’d be concerned that in the event of something breaking or malfunctioning the vertical push rod would drop into a position that gives full power just when things are going haywire already. One of the benefits of the cam system is that the controlling hardware is close to deck height and accessible in an emergency.

Peter

Good point about safety. Any system is likely to require built in failsafe or redundancy, or manual override, based on a risk analysis. A spring return which will zero the flap angle on linkage failure might be a sensible addition to any system.

Mal

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