Paul, Hi, where are you from? I can't see how it works in the pictures. I suppose I should look on the web, but it would be nice to just get the answer given to me straight away here. So I figure that the chinese did it because you can lace or tie the sail on to the mast and don't need much hardware? They maybe didn't sail to windward much? How old ids that design anyway? This tends to sound like a proa group effort at reinacting the ancient pacific canoes of Oceania or something. If there is something useful in an old tradition then it should be kept alive in favour of modern "improvements". I don't know that a harryproa is really a copy of older forms of
craft. I think you could have gotten to it just from looking at trimarans and catamarans and then leaping out sideways into double ender symmetrical stuff. Sorry to digress. Doug
--- On Fri, 27/5/11, Paul Wilson <opusnz@yahoo.ca> wrote:
From: Paul Wilson <opusnz@yahoo.ca> Subject: Re: [harryproa] Re: Swing-wing rig....junk To: harryproa@yahoogroups.com.au Date: Friday, 27 May, 2011, 15:52
I think the sails are sewn so that they have a curved pocket, even
though the battens are relatively straight. With the mast close to
the leading edge of the sail, it being either to leeward or windward
should have little effect on the shape of the sail.
When I saw her sailing, she was surprisingly fast and weatherly.
James seemed to have all the bugs worked out.
More photos here:
http://www.brettmarinedesign.com/apps/photos/album?albumid=8809918
Cheers, Paul
On 5/27/2011 3:35 PM, Doug Haines wrote:
Yeah, Maike, so what I was asking was how
does Brett's boat seem to go so well?
Or why would people choose that strange
unsmoothness?
--- On Fri, 27/5/11, Mike Crawford <mcrawf@nuomo.com>
wrote:
From: Mike Crawford <mcrawf@nuomo.com>
Subject: [harryproa] Re: Swing-wing rig....junk
To: harryproa@yahoogroups.com.au
Date: Friday, 27 May, 2011, 10:48
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:
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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