Engine center problem
 

I placed an OS70 in my GP RV4 and find it is well right of center with the offset built into the kit.... I am looking for the best way to correct since significant shimmying might be in order. Any tricks on how to properly center an offset? The distance from Firewall to aft spinner is right-on but the offset is way off.

Thanks.

RE: Engine center problem
 

The kit's are designed with right thrust to compensate for the engine torque. It is not uncommor for the right thrust to be 2 or 3 degress. If it is excessive, I have used fender washers as a shim to bring it back. Good Luck, Dave

RE: Engine center problem
 

David,
This is well over 1/2 off to the right.... quite a big shim. I take it "fended" means triangulated to keep both shim surfaces flush?

Thanks.

RE: Engine center problem
 

I THINK Dave means "fender" washers. These are large diameter wshers with a small hole in the center. The large diameter keeps them from sinking into the firewall when the motor mounts are tightened.

RE: Engine center problem
 

You best check the fit of the cowling before making any corrections. On mine, the front of the cowling is canted to give proper fit with the engine angle.

Les

RE: Engine center problem
 

With the cowl in-place, I have 1/2 inch right of centerline..... the correct thrust line appears to be set but the spinner will be out-of-center much too far.... I am guessing this is a typical problem with the OS70 on this plane. I will take the offset out and then have to use rudder to fly straight.... quite a shame.

RE: Engine center problem
 

The nuns always frowned upon significant shimmying....:D Sorry, Navy!

RE: Engine center problem
 

I believe to be geometrically correct where you have x degrees offset the vertical centerline moves a calculated distance the other way (left for right offset). This keeps the crankshaft centered in the vertical plane. I have the formula to calculate that somewhere around the shop - but God knows where. I will see if I can locate it this weekend.

Dan