prop sizing for application

[Mich. Maniac]

Hey, I am wondering if anyone has any experience and would kindly share their knowledge with props. I am fine with the prop im running but wonder if its ok to go to smaller diameter with much more pitch or larger diameter with less pitch. Its on the SV and wonder what I would gain or loose with both options.
Thanks
Mike

[Flyguy55]

Hi Mike
It would be a lot easier to comment if we knew what prop your running now :-)
Dick

[Mich. Maniac]

Im afraid you didnt understand. I should have worded it different. Say im running a good setup but want to experiment. Is it better to go up in diameter with less pitch or lower in diameter with more pitch? Or will it all stay the same? If it stays the same which way is better simply on wear of motor?

[icelert]

My guess would be that it would depend on the kv of the motor. If the motor is in the upper range of kv's for the type and size of hull you're running, it should be better to go smaller dia /increased pitch to let the motor spin. If it were a lower kv motor for the type and size of hull then go bigger dia/less pitch and use the torque of the motor to get you more performance.
Of course that is how I picture things, a data logger/gps would eliminate any doubts!

[G Doggett]

I usually compare the calculated pitch to get an idea of motor load.
For example an X640 has 64mm of pitch ( 40 X 1.6 ), while an X442 has 58.8mm (42 X 1.4 ) so speed and load will be higher for the X640 in theory.
Two important things to consider however -
1) if the diameter is too small, even with high pitch, the thrust cone diameter may be too small to move a heavy or large hull.
2) If the diameter is too large, even with low pitch, you will have severe torque roll and prop steering problems on a mono or DV hull.
At best all this theory is just a starting point as trial and error is required to find the best prop for your boat.
Thats half the fun as no two boats are ever the same.
Graham.

[Flyguy55]

rule of thumb for speed. the smallest dia and most pitch with out too much slipage is fastest ...... of course keeping the temps with in limits.
that may not be the fastest combnination around an oval course.

[SweetAccord]

Two important things to consider however -
1) if the diameter is too small, even with high pitch, the thrust cone diameter may be too small to move a heavy or large hull.
2) If the diameter is too large, even with low pitch, you will have severe torque roll and prop steering problems on a mono or DV hull.

Absolutely correctly stated.