I don't know a lot, but it is of public knowlege that Hydroptere uses a computer to control the main foils, in part to cope with stability problems.

The comment that hydrofoils stability with waves is no small issue comes from Aldis Eglajs, designer of the Catris. Each time I send him a photo of Hydroptere he writes "note that all those pictures are taken with flat seas".

My inexpert analysis/opinion follows:

Water movement within a wave ciclicaly modifies the foil's angle of attack (plus each wave is different). An active sensor helps cope with that, but it will necessarily be placed in one fixed position, so for this purpose it is necessarily optimized for one certain wave amplitude in each boat speed.

If this reasoning is correct, then a bow sensor like in the Trifoiler is optimized for higher speeds-larger amplitude waves, while the Rave's lateral sensors would be optimized for slower speeds-smaller amplitude waves.

Adding to the seas influence in angle of attack, the required angle of attack is also changing due to the secondary effects of the waves: zigzag of the boat over the water, pitch, roll, inconstant wind, etc.

Passing the sensor's information through a computer probably helps optimize the work of the angle of attack actuator, but the programming is not exactly easy.

Does all this coincide with your experience or at least make sense??

Cheers,
Luiz