GP Profile P-38 Build Question

I am just at the point where I am about to epoxy the motor mounts to the booms. Why do the they offset the motor mounts (4 degrees) differently for each boom. The right boom has the offset measured from the back of the engine mount and the left has it measured from the front. Would it make it any differnece if the offset was set the same for each boom...i.e. either both from the front or both from the back?

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I'm gonna bet the right thrust is more for the right boom than the left. Torque will pull the plane to the left, and a "left engine dead" is a serious situation. Many pilots, both full scale and model, have turned into the dead engine and the plane has not survived. The thrust and torque from the outside engine may pull the plane into an unrecoverable spin. By using more right thrust on the right engine, it somewhat counteracts this problem. Kinda think of it as dihedral for thrust lines. Dr.1 Driver "There's a Hun in the sun!"

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Each engine points 4 deg. out to help keep the plane flying when one engine quits. Check out RC Universe on the P 38

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Yes, it would make a difference, especially in an engine-out situation.

Having the engines offset like that helps to counteract the effects of losing an engine.

The left engine needs less right thrust, or even some left thrust, because if the right engine goes out, the plane will yaw SEVERELY to the right. Having the engine-torque/gyroscopic-precession/P-factor tending to pull the plane to the left will counteract the tendency to yaw to the right.

The right engine needs more right thrust than normal because if the left engine goes out, the plane will yaw SEVERELY to the left. Right thrust is generally set to counteract engine-torque/gyroscopic-precession/P-factor. Additional right thrust would make the plane yaw right in a normal situation, but since the engine is offset to the right, it will counteract the tendency to yaw left instead.

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Mathew Kirsch

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