Adjusting the height control. Click here for larger photo showing Marco, Malin, Steve and Pete

In mid flight.

Again in mid flight.

Taking a dive!

Mail Malin Dixon for more information.

The boat took a long time to develop. What we ended up with was something like this. This is from memory, so there might be small errors.

Motor and drive. Model car motor, about 11 turns, driven from 8 C-cell NiCd batteries and electronic speed controller. 6:1 gearbox and 55mm pitch propellor, 32mm diameter. Gives about 3kg thrust when stationary.

Hull is from a model planing craft, but the total weight is now 3.8kg. Wings are made from the front wing of a Trampofoil A1 cut into several pieces. Span is about 250mm and chord about 60mm both ends. Take off speed is about 1.5m/s. Top speed is much faster, but we haven't measured it yet.

Controls. Standard radio control gear controls motor power and rudder. Rudder is on trailing edge of front strut and is not very responsive. Turning radius is several meters.

All that is the easy part. Here is the difficult part.

The boat is unstable in height and roll, so control systems have been fitted for both of those.

Height. Capacitive level sensor fitted in front of front strut measures ride height and controls angle of attack of the whole front wing. High speed servo motor (100ms) is used. There is no driver input. We still have some problems. What we think is happening is that as the rear takes off, this causes the front angle of attack to fall, and the height control system is too slow or has too little gain to stop the front falling. When the front is low, it starts to rise, but when the front is low, the rear is pointing down (it has a fixed angle to the boat), so the rear falls just as the front rises, and the cycle starts again.

Roll. The rear wing is in 3 parts, separated by the rear struts. The middle part is fixed, and the two outer parts, about 70mm of span each side, move in oposition for foll control. A pendulum angle sensor is used for slow roll control, with a gyroscope for fast roll control. These control a fast servo motor which moves the outer wing parts. There is also an input from the rudder, to alter the angle as a turn is started. This seems to work well, but there were a lot of bits to get working.

The boat is not very difficult to drive. Without the control systems it would be impossible. The battery life is about 5 minutes.