How Do I Prop Electric For Efficiency
 

Hello,

I have a Giant Big Stick with electric power. I want to know the best way to prop the plane for maximum efficiency. The plane performs wonderful on my current set up, but flight times are somewhat short.

Here is what I have.
-63mm x 64mm 245kv "160" motor
-10 cell 5000 mah lipo
-APC 19x10 E Prop

On the ground the system pulls around 70 amps, produces7800 rpm and 22 #s of static thrust. The RTF weight of my plane is 14.5#. From these stats you can see that the plane flies with authority. What I'm wondering is can I use a different diameter or pitch prop to allow the plane to fly well while pulling less current? I'm ok with some loss of performance to gain flight time. My thought would be to go to an 18x10? Or would 18x12 be better for higher pitch speed at agiven RPM.

Thanks for your input.

RE: How Do I Prop Electric For Efficiency
 

Drop it to around a 16 x 10 and you'll drop around 15 or so amps, thrust will be around 16 pounds, and speed increase of around 10 mph. Flight time at WOT would increase around 2 minutes more. So just a hair over 4.5 minutes using up 80% of the pack capability.
Efficiency should go from around 78 to 87%, per MotoCalc.

RE: How Do I Prop Electric For Efficiency
 

Thanks for your reply. I didn't think I would need to drop 3 inches off the diameter. I guess the lighter prop will have less inertia and gain efficiency. With my current set up I rarely use full throttle. I'm used to flying glow aircraft thatr don't even come close to the performance of this electric. Throttle management is likely the best way to extend flight time, but this power is so addictive!

RE: How Do I Prop Electric For Efficiency
 

Why change the prop?  Just throttle back for reduced draw?  This will reduce battery draw and extend your flight time.