I wouldn't be so quick to dismiss the proa.

  Most boats aren't going to have a downwind SA/D ratio much greater than the Ex 40 or C 50 at stock mast sizes, and both can easily be fitted with taller rigs if desired.

  That's not going to necessarily do any good in a light wind if you're running straight to leeward.  Like you point out, the boat is so light that it will quickly catch up to wind, and then stall.

  But that's a serious combination of rig and light weight for tacking downwind on broad reaches. 

  My cat has about the same downwind sail area as an Ex 40, yet I still enjoy tacking downwind past monos with their kites up.  VMG to leeward is sometimes only a bit better, maybe 100 feet per tack in a 1/4 mile wide inlet in light winds, but the payoff is more in fun rather than VMG.  I've got a beautiful apparent wind in my face keeping me cool, while the mono crews sit in near still apparent wind, baking in their cockpits.

  Another benefit is that the full-batten mains are going to keep their airfoil shape without collapsing, so as long as you trim them well, you can use them in wind so light that a headsail wouldn't fly.

  You could always attach an Outleader to a hard point, but I'd personally just shoot for a high SA/D with a schooner rig and call it a day.  There's less hassle, no extra sails, you can easily singlehand the boat, and you can always completely depower the rig at any moment without chasing down a kite or soaking a sail.

        - Mike

 

I think the direction Rob is going is to an actual kite. As long as there is enough wind to fly it it can be more efficient than a gennaker.

For very light and variable winds there is no substitute for sail area. . .  and less wetted surface area.

I don't think a Harryproa design is the best design for light winds, a pure displacement hull (least low speed resistance) and a huge sail area are going to be better, since all of the speeds and forces are going to be lower.

About the mast strength, any mast is strong enough in light winds ^^  when a gennaker is most useful. The real question is at what airspeed does a gennaker have to come down? 15 knots?  The forces start rising rapidly above 15 knots.

15 knots is when sailing and kite flying start to get fun.

Talador