| I'm not convinced a unidirectional uncambered foil has less drag than a cambered bidirectional. But I guess it requires some analysis. A cambered foil can develop a higher coefficient of lift, so can be smaller, which might balance the higher coefficient of drag.

http://www.basiliscus.com/ProaSections/Paper/ProaSections.htm
I am sure you have read the paper. Speer stopped his camber at 2%. Why do you imagine 4% would be better?

My read is Speer didn't seem too optimistic about his sections beating unidirectional. They only beat them in that they could work without flipping.
His pro3 has problems with balance at 50% cord. There are possible practical solutions as discussed in the paper, and, I thought, that is what Rob was working on.

None of Speers' lift to drags look to beat a good symmetrical foil, and the symmetrical wont have issues like weird balance, lift curves, and drag buckets. IMHO. Do you see it differently?

So it is reasonable, to me, that Rob develop a neat unidirectional system and a, probably more complicated, symmetrical rudder. One for cruisers, one to go fast(er). But it might be one system ends up way simpler in the wash.

| But it could also be that for hydrofoils this potentially higher coefficient is not that significant, because of effects like cavitation and suction of air from surface piercing foils?

Yep. I am still getting used to the ideas of foils in water. In air, a low pressure spot can cause a bubble of air to act differently than the surrounding air. In water, that can pull a air bubble all the way down the span from the surface. Which can totally change the expected performance. So they do cuffs and forward point and other tricks.

And then cavitation adds even more complication. You can only push the foil so hard. You really want to stay in the drag bucket. Or, you HAVE TO, if I am understanding things right.

But the old unidirectional foils are well understood, so I imagine the understanding and solutions are well tread.

| Regarding reefing, I think some kind of system with ropes and pulleys must be used on a Harryproa. Otherwise, how else would you reach to the end of the boom to attach the reef if the boat is stopped with the wind abeam? (And then, how to tie in the loose sail in that position?)

Seems obviously true now that you say it.

| Regarding tillers on 50' boats, it's not completely strange.
| Tiller is the proper way to steer a sailboat, imo.

All right. A few sailors have said that now. Then why are most all of Robs'/Steinars' renders have wheels?

Are wheels super sexy in some way?