Doug,
From what I can see on Brett's NZ proa, he's got a standard
single-skin junk rig that doesn't create an airfoil shape. If
that's true, the sail would indeed be pushing against the mast on
one shunt and pulling away on another.
The swing-wing is a different design, though, with double-sided
wishbones that create a sail with two skins.
The way the wishbones work is that the leeward edge of the sail
has a nice smooth curve to it, while the windward side gets the
kink. This is less than ideal, but also still a better airfoil than
a single skin sail. For each shunt, the leeward surface is smooth.
To get a better idea of how it works, check out these photos:
Nice leeward surface for generating lift:
http://api.ning.com/files/OX6wi*XepeSFiOcN2A1LCruxG28UbW2T02hM1KC3mXMkg5J5D*9b2qh2350oH2Rv9oBLKC3AuWV9WVK3HiLPURXItsWuRpJb/178f2009042200PHAwithitsnewdoublewisbonesintandem.JPG
Corresponding kinked windward surface:
http://api.ning.com/files/8ZicrvcPCMAFxbwHBScmeROW*xJLvh1BnaXKVECpl9rETD3muuQn3pqV0nlR3LNyk6JoZyiD-TBUivh0Bmsl8yxjrNX*bsNh/178gUKJRA0002.JPG
Interior (to see how things might push against the mast):
http://api.ning.com/files/-1yR27opppagPAzdnm*JUW1PwlPrg*WP4CHraDW*Yptmb-pI6CheiXxsLX2itDcZSVU3AbJyOktv7NdXUO*0KzkHniwieOY0/176b200806010037.JPG
- Mike
Doug Haines wrote:
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For the unbelievers, I might say that the
thing looks like a pile of crap - but somehow
seems to go alright (James Brett's NZ proa on
youtube) and get's favourable comments.
How can the sail have good curving when it
has to go on one side of the mast - which looks
ok one one tack/shunt, but then it pushes into
the mast and must make a huge kink in sail shape
when on your other tack(shunt)?
The battens would be pushed up hard against
the mast (like sail against spreaders on normal
boat). The tack with the wind cxominjg from
......need drawing.
Wondering if we could infiltrate Sailing
Anarchy, just so as to use more photo uploading
things
DOug
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