I'd say not true! Just being me again :)
Racking loads and torision have been figured out. Open 60 trimarans fly two hulls sailing on a single down wind ama.
Mast doesn't need to be (in) windward hull could be outside to windward or leeward of windward hull. Stick a mast just infront of the campainion way on a harryproa beef up the beams to that of what a trimaran would have or better yet a catamaran would have.
As you heel wind will spill of top of sail not catch more wind especially in critical or extreme heel angles way before center of gravity shift will capsize boat. Unless of cousre your already a beam vertical from lee to windhull on a face of a wave with a greater beam than your boat.
With mast to windward the down wind ama will resist greater heeling force before mast to leeward on leeward hull. boat for boat sail area for sail area that is.
Mast to leeward balances more naturally with aft set sail areas. Less area from steering appendages needed to direct boat.
Showing mast between two hulls centered with two different types of sails.
http://www.youtube.com/watch?v=Swciuyypot4
With the larger sail area later that day I'm pinching to windward with hull and the wing notice the deeper angle of attack, sail to wind. Sail is not rotated foward as much as it would be for maximum foward drive this is to keep from capsizing. If i did rotate sail foward the pressure differential over wing sucks/pulls boat over in the upper wind range.
Vs with the deeper angle of attack sail flatter to the wind and point of sail/direction saling the capsize is more due to wind strength vs the boats ability not to capsize by weight to windward and ama to leeward of mast position. Notice wing position when model heels pretty flat to the wind for the most part.
Todd
--- In harryproa@yahoogroups.com.au, Mike Crawford <mcrawf@...> wrote:
>
>
> I'd say there are several disadvantages.
>
> - As you point out, masts can't help prevent a capsize. Once you're
> over, you're over. With the rig(s) in the lw hull, you might have the
> chance to pop back up if things get pushed too far.
>
> - The shorter ww hull provides fewer options for sheeting angles.
> With rigs in the lw hull, you can sheet out further to the bows and/or
> back to the ww hull.
>
> - As you fly a hull, the sails raise higher into the air, getting more
> wind high up, and adding their area to the area of the tramps/deck
> that's catching wind. With rigs in the lw hull, the sails lower as the
> boat flies a hull, and the tramps/deck blanket the rigs.
>
> - The ww hull has to be a lot stronger to handle the structural loads,
> adding weight to the boat.
>
> - The ww hull would also lose some accommodation due to the masts.//
>
> - The fore/aft rig loads and fore/aft hull loads would be on different
> hulls, requiring the beams to carry a lot of torsion/wracking loads,
> requiring stronger beams and attachment points, adding weight to the
> boat. With rigs in the lw hull, the wind and water loads all line up on
> the same axis.
>
> Mike
>
> //
> On 11/10/2010 6:01 AM, John wrote:
> >
> >
> > In a weight to windward proa, what are the benefits/disadvantages of
> > putting the rig on the windward or leeward hulls?
> >
> > With a single mast I can understand the problems of a windward rig -
> > mast in the way and stronger construction required. However with a
> > schooner rig aligned with the crossbeams both of these disadvantages
> > appear to disappear. An advantage would be even greater weight to
> > windward. Maybe a disadvantage would be when blown over the rig hits
> > the water when the proa is beyond the point of no return but this
> > should not affect a cruiser.
> >
>