Aldo Cernezzi wrote:
any excess in speed
will be transfered to the water instantly: a big energy loss!
(a student has calculated the amount of energy needed to accelerate
100 grams of water from 0 to 60kts in a few seconds: it's about 3
times as much as the energy that would keep you flying level at the
same speed).


I'm puzzled by the apparent assumptions here, why would any of the rain drops, other than that hitting the stagnation point on the leading edge, be accelerated to 60 Kts? It's much more likely that a high proportion of the mass of the rain drops would simply bounce off with very little momentum transfer. The rain which stuck, a much smaller proportion, may get accelerated to 60Kts, but there is only a limited amount which the wing could accommodate anyway. When I experimented with rain on the wings, I found the sink remained constant even though the speed increased, in which case my glide angle was getting better as I went faster. I must admit I didn't experiment with flaps, but I will, all these comments I've seen so far provide food for thought on how to get the best out of the glider in poor conditions.

Rgds,

Derrick.