after reading a bit on hull design on flying boats and usage in America's cup boats I am thinking of putting a step across the bottom of the boatd. according to the theory this breaks the flow of the bottom of the hull and stops it sucking down into the water as speed increases.

Has anyone tried this on a foil board? do you reckon it's worth a go, I remember f2 had a stepped speed board (maybe the rocket?) which had like air pipes going through the board which I assumed was a gimmick but maybe steps could be a goer.

I know the ppc board uses a seaplane influenced bottom shape with a convex/concave nose but doesn't use the seaplane step...maybe it didn't work for them.

looks like a pain to glass but no major hassle.

cheers chris

I've tried step bottom boards for windsurfing and the difference was hardly noticeable.. They even feel slower at low speeds and I'm guessing wing boards would be similar.. American Cup boats are a different kettle of fish.

I guess cause we actively pump the board up it's not so much of an issue.

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DavidJohn said..
I've tried step bottom boards for windsurfing and the difference was hardly noticeable.. They even feel slower at low speeds and I'm guessing wing boards would be similar.. American Cup boats are a different kettle of fish.

Same here, I had the Kona Mintanker (actual I still have it, gathering dust), with a step bottom in the tail.

Fun feeling, but I don't think it is worth the added drag, weight, and fuzzy rail hold.

I think this design work for engine-powerd boats where you have engine power to spare, and you do not use the rail to hold a curve.

(*) a review: forwards4cowards.blogspot.com/2012/12/kona-minitanker-review.html

The step in a float plane hull is to allow them to rotate on takeoff. When heavily loaded you actually have to "rock" them onto the step very similar to pumping in a way.

After reading "On hydrodynamic analysis of stepped planing crafts" which is available on sciencedirect.com, ignoring handling, water conditions and making some assumptions about AOA, stepped hulls only start to offer drag improvements over 10knts by which time the foils have taken over anyway. think I will keep things flat in rear end.

m04 was considered the best performing design in the study, this was a transverse step across the whole hull.

One caveat. A few good shapers online have mentioned that we mostly lift off before planing speed. The benefits of the complexity have to be weighed against the potential loss of stability (if there is one.)

I'm not that experienced but it does seem that I don't plane long, if at all. I'd love to hear from more experienced people.