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[octo]

good morning everyone; Is a 40mm three bladed prop big enough to
use on  a 36 inch coble, your suggestions please. Thanks tony

[Shipmate60]

Yes if you spin it fast enough.
I have a 38mm 2 blade prop on a  PT boat and she flies with a stock 540 motor on 7.2 volts.
The problem is that there are so many different pitches for 40mm.
A fine pitch will need rpm to push it along, a coarse pitch will need torque to push the model along.
What is the scale prop size for the model?

Bob

[octo]

the motor siize; is speed 600,8.4v, Ive been told this will give me the torque i require.
the scale size im building in is 1/12 scale. Tony

[BJ]

What is the scale prop size for the model?

Bob

Take your choice from attached list, (it is no longer published) .........

[octo]

 Thanks BJ; . yours Tony.

[Shipmate60]

Tony,
Speed 600 motor:

Graupner Speed 600 7.2v Pt No 1793
Product informationPowerful standard electric motor with high torque. Particularly suitable for direct drive operation on 6 cells.Specification   Nominal voltage 7,2 V Operating voltage range 3,6 ... 8,4 V   No-load rpm 18200 min–1   No-load current drain 2 A   Current drain at max. efficiency 12 A   Current drain when stalled 85 A   Max. efficiency without gearbox 69 %   Length of case, excl. shaft 57 mm   Diameter 35,8 mm   Free shaft length 8,7 mm   Shaft diameter 3,17 mm   Weight   195 g
 
On 8.4 volts about 20000rpm

That ia an awful lot or rpm for your type of model. That equates to a mild race type motor.

Bob

[octo]

bob; Thanks for the update, It looks as though ill have to changed the
subject title to "motor and prop sizes  , thanks tony