Aercraft - Sailer ?

Aha, but the water ballast should give less of a drag than fluid dynamic RM in that configuration.

Consider the two mainfoil surfaces of the typical splayed leg inverted T multi with wand control flaps. This one has a center dagger so we can forget about the leeway resistance of the T's.

Case one. Every one hiked out, no ballast, neutral windward foil - reaching the limit of 'natural' (unaided) stability. Lift on lee foil = boat weight. ww foil lift = nil.

Case two. Wind is up, adding water ballast to windward hull, straight above the T. Lift on lee foil: boat plus water. The induced drag increased on the lee foil. ww foil lift = nil

Case three. Threw out the water, but we kept the speed, the wind and the trim - windward foil is starting to pull down. Since the situation other than the water is the same, it must react by providing downforce = weight of water thrown out. Thus the lift and induced drag on the leeward foil is the same as in case 2.
But you added induced drag on the ww foil.

'you only lift the water once' (don't know who I'm misquoting)

On the Wrecks, this is exaggerated, because the moment arm of the water ballast is bigger than the moment arm of the aero force from the wings.
Say the arm is twice as long. Now, that downforce from the aero wing must be twice as big as the one from the water. You can get the quick trim change from the wing, but don't throw out the water in favor of the dynamic RM!

 

VRex

Don't forget that foil lift (in air or water) increases as the square of speed. I think ditching the water ballast could be a key to top end speed-as well as the key to initial takeoff.
I imagine the foils will work just like they do on a Moth except that the faster they go the less lift will be required.

 

You are correct. That explains why I couldn't understand your use of the word leeward for something that looked windward to me.
Looks indeed like it is intended to adopt the windsurf sailing technique.

 

Although windsurfers try hard to keep the rig as upright as possible, most of the time, as it's faster.

 

VRex

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More exactly: Veal Heel which was developed in the Moth Class and has multiple benefits for a bi-foil monofoiler..... The benefits-including increased RM- go way beyond whats possible on a planing windsurfer.