Engine centerline on Chipmunk

[Fred Shattuck]

Hey, Y'all. I am committed to changing up my Chipmunk to a stronger flapless stunt plane. The wings  are just about finished and I have started on the fuselage mods. Decided to stick with the inverted engine, though I don't care for it much. I am using a larger Super Tigre.   My question is about the centerline or thrust line . It seem to me  most planes have this line more or less in line with centerline of the main wing. Is it possible it is done this way simply for clearance purposes? It seems raising the centerline would alter the flight characteristics while inverted. My other option is to rotate the engine around 90 deg, exhaust down and center the lines more, but this would completely alter the look away from Chipmunk more than I would like. Appreciate any comments or suggestions  Fred Shattuck

[Ralph Wenzel (d)]

Actually, the thrust CenterLine is almost always 1/2" - 3/4" above the wing, and the elevator/stabilizer is 1/2" above the thrustline. This compensates somewhat for the drag and weight of the exposed Landing Gear. If you want to get the thrustline closer to the wing center, try adding 1/8" thick mounting plates between the mounts and the engine lugs.