Prop question
 

Well I've got my electrics ready to fly and I've been doing some run times trials and also measuring the Amps and Watts that the motors are pulling. I've got a question reguarding the length and pitch of a prop. For an example, and I'm not sure there are even props this size and pitch..but lets just say there are, I'm running a 8 x 5 prop and i'm pulling 24amps. Would a 9 x 4 prop be just about the same since I'd be cutting back on pitch but lengthening it? I'm just trying to understand what is happening. I know higher pitch like a 8 x 6 would pull more amps and a 9 x 6 would pull more amps than a 8 x 6. Is there a general rule here?
Thanks for all your comments.
Palmer

Prop question
 

There is a rule but it's not very simple.

You can calculate the power required by the propeller. For a given speed it increases directly with the pitch but goes up by the 4th power of the diameter. So generally a small change in diameter makes a lot more difference than a small change in pitch. Of course it then gets confusing because the larger prop runs slower and that reduces the power required to some extent.

I bet that was a lot more than you wanted to know ;).

Steve