very interesting concept boat rick! i'm glad you retired so you could work on such things without the distraction of a job :)

do i understand correctly that the cant of the sail is meant to keep the boat from heeling? if so, would there be less water drag if the two hulls were of equal length??

upwind i can see how the CoE is roughly between the hulls transversely and forward longitudinally, and hence results in better balance. but on a broad reach, wouldn't the sail be close to perpendicular to the hulls, and hence centered on the ww hull?

were you to scale it up to a cruiser, where would you put the accommodations? the lw hull w/o the mast?

ben

--- In harryproa@yahoogroups.com.au, Rick Willoughby <rickwill@...> wrote:
>
> Dean made the changes aimed at improvements based on first test and
> now reasonably happy with performance:
> http://youtu.be/5Cz3YKZj_XY
>
> The rigging still has some problems but much better than first test.
> Notice that the mast starts canted to windward but ends up curved
> leeward due to stretch of the two masthead stays. The sail started
> out close to giving balance but small lw hull got pressed in some
> gusts as the sail cant reduced due to the mast top going to ww.
>
> The noticeable change is the color to pink and green waterline that
> helps monitoring pitch. Other changes are more tension in the sail
> luffs and foot meaning it has less camber. Reduced rotation of the
> sail - now too little to get best speed on broad reach. Large,
> heavier hull shifted to ww side to move CoG to windward. The CoG is
> now 200mm from the ww hull so sail drive vector is now just to the
> lee of the CoG when the sail is canted at design angle of 45 degrees.
> (Will be less cant on the scaled up version because the CoG will be
> even closer proportionally to the ww hull)
>
> As the mast head moved leeward during the course of testing the boat
> gained more weather helm and lost pointing ability. It could be
> shunted through more than 270 degrees when we started out.
>
> The wind strength was mostly less today but there were gusts that
> could easily capsize it if the sail was not canted. It was capsized
> once when the sail travel got caught and pulled the bottom of the
> sail to the water rather than swinging it when shunting.
>
> It is now really well behaved. Very easy to sail. No difficulty
> getting away from a lee shore. In fact with the reduced sail travel
> it could not be balanced properly off the wind so was slower than it
> should have been when sailing fee.
>
> My idea of sailing without sail rotation control does not work
> because the most stable position for the sail is dead downwind, so
> boat gets drag sideways
>
> We did not try any automatic depowering of the rig because capsize
> was not a threat on the day.
>
> Rick Willoughby
> rickwill@...
>