[quote/] Back on topic. Does anyone have any ideas about this? I can think of several reasons for not doing it but there are a couple of reasons for doing ot as well. I would be interested to hear other peoples views.
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First of all, I'd like to make it clear that what I know about foiling could be fitted on the back of a postage stamp with room to spare. Also, my engineering / hydrodynamics knowledge is only a little above Ladybird book level.
However, using my completely unfounded logic, I reckon it might go a little bit like this:
1. Upward lift from a centreboard T-foil is a function of forward speed (actually squared in some way I think).
2. The foil would need to lift something in the order of 200kg (boat and crew combined).
3. Say for example the critical speed at which the foil produced 200kg of lift was 20knts. At 15 knots it might produce 150kg of lift, but this isn't enough to lift the boat out of the water at all, not even a little bit. All it would do is produce drag.
4. At exactly 20knts the boat would lift neatly out of the water and start travelling faster.
5. At 21knts it would get completely airborne and the t-foil would break the surface.
However, I had a thought a while ago about whether an inverted christmas-tree arrangement might work. The idea would be that you would have say 4 horizontal elements on the daggerboard, each about 30cm below the one above. The one closest to the hull would have the widest span, getting to a progressively narrower span as you go down. As the boat accelerates and starts to lift out, you would get progressively less lift as more elements break the surface. As long as the bottom element was small enough to not break out in anything less than 30 knts, you might be OK.
N.B. in reality I have no desire to go full foiling in a Cherub, and this thing would never work due to too much drag, inability to raise the daggerboard etc.etc. But just an idea I thought I'd share with you.
