Rolf,

I am always very careful if people tell me something about minimising drag. I don't want to have a boat minimised for drag. I rather want to have a boat optimised for speed or efficicncy or whatever. To make it clear, a boat optimised for drag is a boat without a sail, or even better: no boat at all. And it should be clear that this should not be the target for any trade.

Yes, bows generate drag, and no bows generate no drag, however bows generate also some lift (like a sail) if sailing upwind, and as with sails, bows with higher aspect ratio are more efficient than bows with low aspect ratio. Apart from that hulls accelerate the flow at the low part from the sail by displacing a volume of air and reduce the tip vortex (at the boom) around the sail. As mentioned this is explained in Marchaj's book.
Last but not least, the hulls of a beach catamaran help to make the flow around the trampolin more efficient, hence it generates more lift and less drag (this effect might be offset with a spinnaker kit). The lift of the trampolin lifts the boat (slightly) and reduces hydrodynamic drag.

All of these effects are of secondary order. But it shows that optimising a single component (the bows) of a boat for a single reason (aerodynamic drag) doesn't guarantee an improvement of the whole system (which includes much more than just aerodynamics).

Regarding the drag of the sailor traping out: The same sailor would have about the same drag while sitting on board, but he interfers less with the sail when trapping out (although I don't know if this is good or bad). Again this is a second order effect.


A bit off-topic: When building your rudders and boards, you shoudn't round the tips. Maybe you know that already.

Cheers,

Klaus