I had a good look at the site and I am quite impressed. The sail shape is very nice. I am not sure why the curve couldn't be done with a flexible batten.
--- In harryproa@yahoogrou
>
> Rudolph,
>
> Thanks for the detailed reply. I was actually in the process of
> writing an "I posted to soon" post. When I originally looked at the
> link you sent, my browser bombed out and didn't load the bottom half of
> the page. I wasn't aware of the 2008 and 2009 design upgrades.
>
> The 2009 wishbones do look much better in terms of the red padding
> used to keep the wood off the mast. That might be enough to cut down on
> clatter and wear if the downhauls are reasonably snug. I'd definitely
> want as much padding and as little friction as realistically possible
> (given weight and materials limitations)
>
> The shape on the leeward side of the sail with the 2009 double
> wishbones is beautiful. I can't think of a nicer shape. Plus, it will
> keep that shape without constantly trimming strings and watching telltales.
>
> As with Gardner, I do worry a bit about the hinge joint if running in
> a strong breeze.
>
> I'd feel better with a magical indestructible composite batten that's
> light enough to taper into a nice curve on its own, without a hinge, and
> tough enough to take the bend produced by a serious gust. That would
> allow the wishbone fronts to be made from wood while using the benefits
> of composites for the batten.
>
> Is this realistic? I've seen fishing rods that can bend in a 360
> degree arc, so my hope is that it would be possible to create such a batten.
>
> If not, I suppose one could argue that each wishbone is so lightly
> loaded that the hinge strength won't matter, and that the double-frame
> system is always going to create an ideal shape, whereas a batten will
> curve differently in different wind strengths.
>
> But I still like thinking about a system without a hinged joint.
>
> - Mike/ /
> / /
> / /
> Rudolf vd Brug wrote:
> >
> >
> > HI Mike,
> >
> > From what I understand the wishbones are as little and loosely
> > connected to the mast as possible.
> > The latest version wishbones have a sort of brace on front of the
> > mast, that's all. Windward side rests against the mast.
> > http://wharrambuild
> > <http://wharrambuild
> > about 5/6ths down the blog. There are a lot of photos but this one
> > shows the inside of the sail, the wishbones have red spiral wound
> > tubes to protect the mast.
> > With type of rig you don't want to add things/ropes or whatever, you
> > try to loose as much stuff as possible.
> > A shunting schooner doesn't seem very handy witth this rig, I agree.
> > It might not be a very good rig for shunting at all as the sheets may
> > get tangled when shunting. A tacking boat only has one set of sheets,
> > but two sets may cause trouble.
> > I know of at least one (small) shunting proa using a junck rig. So it
> > can be done.
> > The multiple sheets are the reason the loads are small, replacing them
> > for a boom brings us to the high loaded rig we already had.
> > Battens could be composite but probably at great cost as there are
> > moving parts, so dimensions are critical.
> > Wood would be a bit heavier but much cheaper. I don't see rot as an
> > issue here.
> > The double wishbone as seen in the blog gives a shape that leaves
> > little to ask, in my opinion.
> >
> > regards,
> > Rudolf
> >
> >
> >
>