What: We are building a small boat made of a special paper foam soaked in glue and epoxy. It is aproximinatley 40 cm long and 15 cm wide. Very light. We aim to transport a single can of beer at the local sweet waters with about 30-40 km/h.
Question: We have been trying to figure out for weeks how much torque we need. After some failed attpts where the rotors move at full speed out of the water but come to a dead stop inside we figured out we need a Geared one. But how do we determine the strength and rpm?? How much gcm/ncm? The rotors are about 2.5 cm in diamater.
Please give any insight in the estimated required torque per motor.