Okay, the project is continuing after 2 months, and we are now seeing why ignorance = failure.
I ended up making a "boat" out of folded stainless and a 25cc Talon weed eater motor. Because buying ready made parts was not part of the competition, we have also had to make our own dodgy
prop out of stainless.
The twin blade (120mm diameter) job we came up with, simply stalls the motor, or breaks the
prop shaft, partly because the engine doesn't seem to have a clutch, which means the
prop is spinning when it hits the water.
Manufacturers only seem to go to a maximum of 80mm diameter. This seems too small for a weed eater engine which produces much lower RPMs when compared to one of the off the shelf
RC motors. Does anyone have any opinions on this?
I've also got a problem where the
prop shaft goes out the transom at a very shallow angle, meaning that half of the
prop will be exposed if the boat ever gets fast enough to create a draught. I've read that some props work in these conditions, but I can't seem to find out when, or how this would work effectively. Can anyone tell me if they have seen this work?
Cheers,
Dave