Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Pleasure boats, Sports, Race, Power and Leisure Boats: => Topic started by: chris1 on December 26, 2014, 07:38:11 pm
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Hi there, i've dug out an old Graupner Cobra and intend to go brushless. Not going to use the 'hydrospeed' drive, preferring a fixed prop shaft and separate rudder. I've found a nice strut/rudder on ebay for a 1/8" flexi shaft. I want a fast boat, not stupid fast, but not a slow-boat:-) i would also like to stick to 3 cell lipos, purely because i have some. Can you guys offer some advice on motor / prop sizes?
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Hi
I Believe your boat is 535mm length beam 160mm
Two ways to go!!!
Hobbyking F3 sprint outboard with 28mm motor 3000kv on 3S battery 2650mah 32mm x 1.4 pitch prop(very quick boat).
Or go inboard with 4mm flex small strut and small rudder.
Motor going over 700watts in that size boat would be a handle full and total insane to drive.
My 600mm shallow vee has one of the Hobbyking outboards on the stern and on a flat calm day in a straight line full throttle in sits on the prop with no hull in the water.
So the upgrade 2836-3700kv motor 4S battery and 32mm x 1.4 pitch 3 blade prop is going to another project.
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Thanks canabus! I've already got the strut / rudder for a 1/8 flex shaft so i'll go inboard rather than outboard. So if i go for a 3000kv motor on 3 cells, and 32 mm prop i should have decent performance.
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I fitted an IC engine to mine! {-)
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I gave the 3000kv motor a quick run on 4S(the motor spec. do not say it supports 4S).
Totally insane!!!
So I would look for a 700watt 28mm motor which will handle 3S and 4S(also the ESC).
So you can have a bit of flex in your setup.