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Author Topic: Matching prop size to Amps under load  (Read 96 times)

Offline MikeB

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Matching prop size to Amps under load
« on: June 23, 2020, 03:06:01 PM »
I am just setting up a electric motor on a new plane which is a low wing super 60, not generally thought of as a performer.

I have one query. With a 12*8E prop it gives
out 48 amps on a 4s battery and a 60 Amp ESC.
That would be 107 Watts per pound at 3.7 v per cell.
Is it worth going up to a 13*6E prop which  gives out 51.5 Amps to get 115 watts per IIb.
It should fly on both reasonably comfortably according to guidelines.


 

Offline IanF

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Re: Matching prop size to Amps under load
« Reply #1 on: June 23, 2020, 03:37:22 PM »
To compare props I use
2 x diameter + pitch calc
Both give a number of 32 so in the air they would both feel the same, with the 13 x 6 a bit slower, which is what you need.
As it’s a vintage model, I’d go for the 13 x 6 or a 14 x 4 to slow it even more. It would be a relaxing fly then.

The current draw is so close it wouldn’t make any difference in my opinion.

BTW what is the motor?
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Offline MikeB

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Re: Matching prop size to Amps under load
« Reply #2 on: June 23, 2020, 04:37:11 PM »
Haha...you should not ask

The balance of the plans was severely to the rear and it weighed about 16oz heavier than Phil's so I put in a Ripmax Quantum 40
Rather than the smaller motor recommended

The 4s 3300 was right at the front of the cockpit  and I was worried about a bigger 4as with the smaller motor

Offline IanF

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Re: Matching prop size to Amps under load
« Reply #3 on: June 23, 2020, 05:45:36 PM »
Good to see you using a heavier, more powerful motor rather than lead to balance .👍
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