Which motor/drive + prop

[t_boy]

Hello,

I need some help . My project is catamaran-like boat, about 0,4m 3kg.
I intend to put two motors , no rudder. My first question is could I use to 380 size Drives from Robbe/Graupner to move it at 5-8 km/h ? Also what size propelers should be - 30 ,35 ,40 ,45mm...?

Thank you.

T_boy

[boater_dave]

3kg seems a bit heavy for a boat that is only ,4m long. What is it a modeled after?
I have used geared speed 400's in PT boats. 1.5:1 with a smallish prop for speed and the amp draw is under 10 amps. Reduce the prop speed with a 3.5:1 (or more) reduction and turn a larger prop for moving a displacement hull around and your amp draw may still be under 10 amps.
Does the drive you are looking at have a gear reduction?

Dave

[toesup]

My project is catamaran-like boat, about 0,4m 3kg.
I intend to put two motors , no rudder. My first question is could I use to 380 size Drives from Robbe/Graupner to move it at 5-8 km/h ? Also what size propelers should be - 30 ,35 ,40 ,45mm...?

As its a bait boat http://www.rcgroups.com/forums/showthread.php?t=721067 :p that has extra weight to carry, you would probably be better off to go for two 550 type motors and gear them down probably 2:1 or 3:1.
Someone like Stock Drive Products can provide the gears and / or the Gear / belt drive you need. https://sdp-si.com/eStore/
Prop size depends on what you can fit, go for the larger size... at least then you can reduce it if necessary following tests.

[frankg]

:) T BOY- Try looking at the MACK Products Model Marine Motor #1885G. The motor gives all kinds of power with a ball bearing gear box, with three gear ratios included with the motor-gearbox. The unit can be seen at www.mackproductsrc.com on page 2 of the power units section. :)