Motor and Prop help.

[IcedStorm777]

I am wanting to make a really fast plane. I am planning on a 35" wingspan and a fairly simple design. I have a 2627 4500kv motor. I am planning on running this with a 850mah 3s or a 1350 4s. I am using a 30A esc. My question is what size prop should i swing for good speed but not to kill the motor? Thanks!

 

[Flitedesign 3d]

It seems like that motor is made ofr 64 mm edf and 3 cell lipo. If you want wo use a propeller you can forget about that 4 cell. Even 3s seems kinda much combined with a propeller, maybe you could use 5 or 6 inch quad prop.. Even that would be kinda inefficient due to the high rpm of the 4500 kv

 

[IcedStorm777]

It is from a 64mm EDF but figured if i used it with a small prop it could work and yeah 4s is a little ludicrous.

 

[Flitedesign 3d]

It is from a 64mm EDF but figured if i used it with a small prop it could work and yeah 4s is a little ludicrous.

If you dont have a watt meter the next best solution would be trying diffrent props and watch the motor temperature. If you want more efficiency I recommend using 2s lipo

 

[evranch]

You are going to need a prop with almost no pitch or it's going to be stalled all the time. Check out eCalc, you can use the free version to get an idea for a starting point.

Save yourself the trouble of burning something out. This kind of wattmeter is amazingly accurate for its price: https://www.amazon.com/dp/B06XPVKY13 and a bunch of different sellers repackage the same meter. It also measures mAh consumed, peak currents and wattages etc. It's a very handy little tool.

I have mine in my hand right now from doing some load testing. It measured 1650mAh used in flight and the charger put back 1635mAh... pretty impressive for $15.

 

[Wildthing]

My thoughts are you don't have the right motor to spin a decent prop and come up with great thrust especially with a fairly large plane at 35" WS.

 

[Merv]

Here is a motor test of something similar. This guy has done quite a few motor test, you might look at his other videos to see if he has tested your motor.