ORIGINAL: FBodyexpert
Your downthrust from the pilots view should actually be down-right and is usually 2 deg in each direction. Sometime a little more for a plane that has a higher power to weight ratio. Start by using the thinnest washers and work from there. Yes you can use shim stock to make your own washers. Really the best way to check for the right downthrust is to fly your plane. When in strait level flight, open up the throttle. If the plane rolls left, not enough right thrust. If it pitches up, not enough downthrust.
G'day Mate,
Your statement about right & down thrust, are not quite correct.
Depending on the plane, it may need right thrust, but no down thrust, & if the plane needs right thrust, it won't roll, if it needs more, it will yaw, left.
To test for needed right thrust, fly full power, trim for straight & level, hands off.
Pull up into a vertical climb, & watch the nose, trim for straight up climb with rudder. you may need to do this multiple times.
Land & measure rudder angle, on the ground, with radio on.
The amount of right thrust required, is 1/2 the rudder angle, measured.
The amount of down thrust is tested by, flying the plane at full power, straight & level, trim for hands off, & chop the throttle, & watch what the plane does, if it continues on, without any pitch change, thrust is OK, if it pitches up, a lot, you have too much down thrust, if it pitches down, more down thrust needed.