Hey, can anyone help me on the propulsion system of my sub (which will be about a foot and a half long, and about a quater foot wide), I am only 12 years old, but know more about it than u think. I know of a way using gears and all that, but is there an easier way to do all this. Or do they sell water proff electric moters, and ifso where can u get them? Thanks

What you need is called a stuffing tube, it's a piece of (brass) pipe that goes through the hull, with bearings on each end, put the propshaft in,after filling/stuffing it with grease, and you should be waterproof.

On the other hand, electric motors will run under (fresh!) water, so as a last resort, you could mount the motor outside the hull.

Regards, Jan.

Just as an aside...

What is 'fresh' water considrered to be?

discoboy,
The 'loosest' definition is water with no salt. It ranges between distilled water and what you find in a ditch. The more 'stuff' in water, the less 'fresh' it is. As far as electric motors are conserned, 'fresh' water is nonconductive, won't short the motor. The more 'stuff' disolved in water the more conductive it is. A ~very~ broad test is, would you drink it?
- 'Doc