Spin her up!! Rev it up high! (maybe)

[tiqueman]

High rpm alone is simply not always the best route. The motor/hull combo will determine the best prop and rpm to use. Sure there are times when a lower pitch prop will give higher speeds - if the original prop was placing too great a load on the motor and forcing it out of it efficiency range. There are just as many cases when a higher pitch prop will give higher speeds, sometimes with lower amp draw too.

The bottom line is you have to experiment with your setup to determine which prop works best. Then if you change the setup a bit - raise the prop, better cells, different motor - you'll have to start over again. This is one of the parts of the hobby that keeps me here for so many years....


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Very well put Fluid.

[ReddyWatts]

Anytime you can lower the amps and get more speed in sport running, its makes your boat more reliable. Less smoke, more fun.

That is why I run this, it is one of my favorite economy setups: Mean Machine - Feigao 540 14XL, 8s, 100 amp HV esc, X537/3

I noticed the smaller prop power band thing in this setup. Cant explain it, but its there.

[Jeepers]

here is my observations in race conditions, in our N2 sport hydro class there are high rpm setups and low rpm setups , the low rpm set ups with bigger props have NO problems keeping up with the high rpm small prop set ups. most of the low rpm boats keep propping up and going faster while the high rpm boats are already maxed out due to temp issues mostly esc temps.

Sorry I have no data to give other than the guys saying" this motor/esc is not even getting warm, I think I will put a bigger prop on it"

[Jeff Wohlt]

When racing oyu will find the smaller props will get you thru the corners better...just have to find the perfect combo for both.

[supafastsupra2]

Wouldn't a gear drive have the same effect without the cost of cavitation with a smaller prop?

[ReddyWatts]

Yes exactly, but less reliable. "gears"

Its cool when you do find the right combo for the motor that is not to small and hits the powerband for more speed than what you can get with a larger props.

[FighterCat57]

Gears are a neat idea... I was thinking of building a hard prop shaft and using gears to get the exact RPM/torque I wanted... But, they introduce many other factors I don't want to deal with at this point.

Thanks for all the replies and input, all good stuff. I really don't know what the right prop/volt combo is on this setup yet, but wanted to share the unexpected success and see what others had to say about it.

Think I have time for an afternoon run. On windy days, calm water is 20 minutes away...

[supafastsupra2]

I guess I'm just weird but I see a gear drive as more efficient than overstressing a motor and drawing so many amps as most people do on here. I believe with a smaller motor spinning more rpm you can achieve the same power output with less heat and a smaller motor for a given application. It's how it works on car applications and some airplane applications. I believe the only motors that should be direct drive are outrunners because of their inherent torque due to their large rotating mass. Am I just completely off pace or does this make sense in real world application. All the Neu motors are rated for ~60k rpm, so you could run them at say 50k with a 1.67:1 ratio. You can also increase efficicency this way because you can use small gears and use very little bend in the stuffing tube going from the gearbox output or use a wire drive. If I do end up doing another boat anytime soon (when funds allow) it will be a geared setup as described.

[Jeff Wohlt]

It is a great system...10 years ago it was the only way to spin big props on 05 motors...now we have the motors to eliminate the gears. Still not a bad option if you can still find them. You are right with you assumptions.

[Jeepers]

When racing oyu will find the smaller props will get you thru the corners better...just have to find the perfect combo for both.

I don't know if i totally agree with that, my Whiplash corners way better with a large prop over a smaller one. However my old Lifter hydro corners smoother and handles better on high rpm then it does on a low rpm set up. I think it has more to do with hull design than just small vs. big prop.

[Jeepers]

. There are just as many cases when a higher pitch prop will give higher speeds, sometimes with lower amp draw too.
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This is true at least with my P sport Whiplash with a 1521 1.5d. without water cooling on the motor with a m645 prop it would come in at 130F after 1mile plus full mill lap, on a 648 it will come in at just over 100 degrees with same run time. again no water cooling on motor.

[BHChieftain]

One thing I've recently discovered quite by accident is that a low kv motor gives you the best of both worlds-- I've got a 1500kv neu and I'm currently running 4s1p, and I'm increasing the prop size until I either get some heat in the motor or get too much prop torque effects-- so far I am up to a 1.4 x 48mm prop with zero heat (the can is literally cool to the touch). I will be trying an x450 prop next week when it comes in...

I can go the opposite route and run 6s on the same motor with a smaller prop. I figure I've got enough combinations to keep me busy the rest of the year...

Chief

[Raydee]

This is true at least with my P sport Whiplash with a 1521 1.5d. without water cooling on the motor with a m645 prop it would come in at 130F after 1mile plus full mill lap, on a 648 it will come in at just over 100 degrees with same run time. again no water cooling on motor.

Yep my Whip with a 1515 1Y runs hotter with a 42mm prop than with a 45mm prop. I guess it all depends on the setup and the motor. Some motors need the right load (prop) on them to work efficiently. With a Neu motor I usually know when I find the sweet spot with props because the boat's seem to come to life and run much cooler. When I ran Fiegao motors they seemed to like smaller Diameter, higher pitch props. Once you started to go up in diameter everything just kept running hotter and hotter. So far with all my Neu's that hasn't been the case.