Prop for 22inch cat?

[brons101]

hey im new here and dont have alot of rc boating exprience and it would be great if someone could help me out.

my question is what would be a good prop to run on a 22inch catamaran with a 3900kv seaking on 3s lipo? thanks so much for your help!

[CraigP]

your motor kv is way too high. It's figuring about 43,000rpm. You need a motor to get you to about 34,000 - 36,000. In that range, the Octura M440 is a good prop. I have no recommendation for your current setup.

[brons101]

your motor kv is way too high. It's figuring about 43,000rpm. You need a motor to get you to about 34,000 - 36,000. In that range, the Octura M440 is a good prop. I have no recommendation for your current setup.


May I ask why you think it's way to high?? I'm assuming those rpm numbers are "unloaded"
I've ran this setup in a 16 inch cat on 3s with a 30mm 1.4p prop , although very fun and challenging it did torque roll way to much. I would think the 22inch hull would be much more appropriate for the 3900kv motor I'll be running two separate cooling lines one for the esc and one for the motor. Are you worried about temperature or it being to much Motor for that size hall?

I appreciate your help

[CraigP]

I base my numbers off of good reliable sport boating. If your racing, then maybe the racers can chime in and guide you. But my thinking is that every prop comes out of the water from time to time. When that happens, the motor goes to unloaded speed. At over 40,000 rpm, a significant amount of prop torque is encountered when the prop hits back it in the water. This can give a hull big handling issues. Also, very hard on the drive line and the batteries see a huge current spike when the prop hooks up again. But if your racing, the rpm is better than the ills of a prop that's too big. In that case, many run it harder on the nose to keep it handling decently. Those are my thoughts, I'm sure there are other opinions as well.

[CraigP]

For comparison, I'm running a 1400kv on 6s in a DF29 mono... Which is slow. Just got this boat, so I may be looking at a motor change.

[fweasel]

For what it's worth, I run a 27" cat, 3080kv motor on 3S with an ABC 1614 prop, runs greats, Electrics barely warm up over ambient

[brons101]

For comparison, I'm running a 1400kv on 6s in a DF29 mono... Which is slow. Just got this boat, so I may be looking at a motor change.

Thanks for the info, well I'll try it out and see what happens , if it handles poorly or over heats , what motor would you recommend for it that would work on 3s and a 60amp esc, would love to be able to hit at least 50mph. Thanks

[CraigP]

For what it's worth, I run a 27" cat, 3080kv motor on 3S with an ABC 1614 prop, runs greats, Electrics barely warm up over ambient

OP wants to do this with a 60a ESC... I'm thinking he needs a 120a, what do you think?

[brons101]

For what it's worth, I run a 27" cat, 3080kv motor on 3S with an ABC 1614 prop, runs greats, Electrics barely warm up over ambient

Sorry didn't see your reply till now, that's sounds good if this motor isn't suitable I'll get something in the lower 3000kv or high 2000s , thanks

[fweasel]

OP wants to do this with a 60a ESC... I'm thinking he needs a 120a, what do you think?
mine is a 220A SF pro. :laugh:

[CraigP]

OP, the concern is you're ESC is not high enough current for your expectations. Just food for thought...