Carl,

Your concerns are probably the right ones. I certainly don't know enough to give complete and definitive answers, but here are some things to think about. I learned them slowly from the Catri designer.

1) Getting the proper angle and adjustment is a big problem. The Catri solution was using the boat's atitude as angle of attack adjustment. The rear foils work much like airplanes rear wings to keep the boat atitude where the designer wants it to be. The side effect is that pitchpoling is very unlikely. This - and other - solutions are patented.

2) Lifting and crashing is another problem. The boat needs additional energy for lifting (thus extra foil surface and drag) and has to get read of the potential energy orderly when landing, otherwise it crashes. He got read of this problem designing the foils for 90% lift only. The Catri never lifts entirely out of the water and the remaining wetted surface is a planing surface, with minimal drag. The top speed is slightly lower, but the foils can be shorter, the drag smaller and crashing is not a concern at all.

3) Very slow speeds before lift occurs: This is due to foil's drag and the additional energy to lift the boat, especially when automatic angle of attack regulation mechanisms are present. In the Catri this problem is reduced mostly using rear foils that stay out of the water in low speed and by the absence of regulation mechanisms taking energy from the boat. The designer also raised the rudder foil - it is near the surface, where it is supposed to steal energy from the rear wave. Also, thru hull canted foils can be retracted in low speeds, reducing the drag but still providing enough horizontal lift because they are asymetrical.

4) I believe that angled thru hull foils are less effective then inverted T or L shaped foils in a test tank. The advantage of canted thru hull foils is that (as demonstrated by Bruce - hence the name Bruce foils) they maintain the stability as speed increases. Also, it is impossible to reduce the working area of an inverted T or L shaped foil, but it is easy to partially retract an inclined daggerboard.
For this reason (reducing drag), inverted T or L shaped foils tend to be more symetrical and use active angle of attack regulations to increase lift, while a canted daggerboard can be more agressively asymetric.

By the way, the Spitfire's foils are canted but not thru hull as in the Catri. This means that ventilation is more likely to happen. It seems to be one of Hydroptere's problems - it is shown usin many "fences" in some photos and less in others. They seem to ignore Bill Roberts solution of canting the foils forward.

Cheers,
Luiz