Wats the lowest useable kv

[hugh hargett]

Ive been looking at the huge outrunners under 500kv. Is it possible with a prop large and with enough pitch????

What do you guyz think???????

 

[ken turmon]

What kind of voltage are you thinking. If I understand corectly your thinking big prop turning slower to get the speed??. Bigger load larger amp draw? amp draw is somewhat lower when the voltage is higher so it could be do able if you get the right balance of voltage and prop size.Data logging would be a big plus since your really treading in unfamiliar water...lol. But it would be a great experiment since there are a ton of lower kv outrunners to choose from.

 

[hugh hargett]

Well im thinking in terms of gas props and 15-20k @ around 42 volt or 10 s lipo. So maybe 470-500 kv maybe :unsure:

 

[ken turmon]

The one factor I don't know is how rpms affects amp draw. I suppose at some point in the rpm curve the motor reaches peak efficiency But outside of that would it draw more amps at higher or lower rpm's. I see Ben at fightercat has some hv esc's with data logging in the works. Might be just the ticket for such an experiment. The other question would be hull choice. Gas size hull or normal fe size?

 

[raptor347]

You could build a pretty fast boat with a healthy 500kV outrunner. Prop selection and tuning becomes more critical. A converted gen 2 Whiplash could be very fast turning 18-19k loaded with something along the lines of a 2716 on the back.

 

[hugh hargett]

The one factor I don't know is how rpms affects amp draw. I suppose at some point in the rpm curve the motor reaches peak efficiency But outside of that would it draw more amps at higher or lower rpm's. I see Ben at fightercat has some hv esc's with data logging in the works. Might be just the ticket for such an experiment. The other question would be hull choice. Gas size hull or normal fe size?

The faster you try to spin a larger prop the more amp draw

BUT amps and torque go hand in hand in FE. You cant have torque without amp draw. A lower kv motor will have more torque than a higher kv @ the same amp draw. This is is proven by calculating your KT which is the torque constant for an electric motor. Its found by 1/kv=kt take the kt and mutiply it by the amps and you get the torque output @ that amp draw.

Brian, Im thinking along the line of a gas shovel hull.

 

[raptor347]

RaceMechanix ran a CC/Neu 2028 in a converted Hyperformance Thunderoat hull. 8S2P 5k's and I want to say a 2614? Well over 200 amps, but seriously fast.

Only reason I won was he didn't have it dialed in the corners yet. He had an easy 5 mph on me in the straits. http://www.intlwaters.com/index.php?app=gallery&image=9117

A converted Tboat turning that 2716 at anything over 16k will be a fast/fun boat.

 

[hugh hargett]

NICE! I love those big dawgs.

 

[hugh hargett]

"I suppose at some point in the rpm curve the motor reaches peak efficiency "

Ken id be inclined to think the motor would be its most efficient at its most efficient amperage load. Typically the manufactures give you the peak wattage or work. Id shoot for rms power given my voltage.

given 5000 watts

5000/1,41 > 3546/8s = 105 amps that would be my goal as an average maybe 20 percent more with adequate watercooling,prop work,etc. 126 amp with about a 180 amp peak. Thats where id shoot for. I know it can be done as the fellas in WA. Ran skorpion outrunners on 8s with x457's pushin 50 plus. Running turnigy 80 esc's. 8s lipo,and 300 amp speed controls with the proper batteries,I could easily see pushing x470's and such right on up there. Those big props thrive in race water. I have a 1667 with 6.0" cup,nd a 43 inch sprint cat, anyone willing to trade me 540 kv 5035 skorpion,2028 leo or tp 5692 no more than 750 kv for a new Neu 1527 1.5 y?

 

[ken turmon]

How many kv's is the neu.

 

[wayne middlemiss]

hugh i have a 2220 2y 550kv to do the same thing there is a few vids on you tube of sport hydro setups its a aeromarine hull

 

[hugh hargett]

Ken a made a boo boo its a 1527 1y 1250 kv . Good for Q or S power.

Hugh

I have a new one and a factory refurbished one

 

[hugh hargett]

Brian whos the guy on the far right of the photo?

 

[hugh hargett]

No takers on the neu trade? Comes with cooler and collet??????

1527 1 y 1250kv

 

[hugh hargett]

I was thinking something like this: