RCU Forums - View Single Post - Prop Chart and Basic Electric Setup Sticky

08-07-2011 | 06:43 AM

#14

im_a_rcav8r

Joined: Jul 2002

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From: Land O Lakes, FL

RE: Prop Chart and Basic Electric Setup Sticky

Quote:

ORIGINAL: M9cat

So I just bought some pusher props for my Super Cubs..I didnt know that they were counter rotating props so i just switched the red/blue wires from my motor to esc...How well or will the plane even fly right? It seems to be working just kinda scared to put into the air..

I am not 100% clear on your question but I will make a go at it.<o

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>If I understand correctly, you have a front engine type airplane and you have purchased ‘pusher props’. When you put the pusher props on your airplane and power up, the plane wants to got backwards – so you changed the motor to spin the opposite direction.<o

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>Will this work? Well…. Yes, sort of. Is it recommended or a good idea? NO. <o

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>The propeller ‘pusher prop’ you have is designed to be mounted on a rear engine plane where the propeller ‘pushes’ rather than ‘pulls’ the airplane along.<o

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>If you take a close look at the propeller you will see it is in-fact an airfoil – like a wing. As the propeller spins it creates lift. It is the lift (and some deflection) that causes the ‘pull’ force or thrust.<o

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>Again, taking a close look at the propeller you should see one side (the side away from the motor) has a slight curve (convex shape) and is thicker at the leading edge and thinner at the trailing edge. The other side of the propeller is flat, or is some cases concave.<o

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>By spinning the propeller in the opposite direction you completely defeat the engineering that went into the design. It is like putting your airplanes wing on upside down and with the trailing edge forward.<o

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>Because of the pitch in the propeller, it will deflect the air and produce thrust but it will not produce lift. You will get substantially diminished performance and unpredictable behavior.<o

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>In addition to the diminished performance, you will be introducing stress and loading to the propeller that was never intended. The propeller may tolerate the stress or it may fail. If the propeller fails when someone is in the path of the debris the results could be disastrous.<o

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>If the propeller is designed to push, let it push – don’t make it pull.

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