wsmalley

My Feedback: (6)

I bought a TF P-40 from an estate that had been crashed. The original had a 1.20 and I'm putting a Saito .80 4S in it. I noticed that I can't seem to get the right and down thrust dead on to match the nose of the cowl and chin profile as exact as the previous owner had. The question is what effect does each- right thrust and downthrust- have, and what if I'm a degree or two off in either direction? I'm still trying to shim here and there to get it right. Then, how the heck does one accurately measure the right/down thrust in the first place? You have to hope you get the firewall offset correctly in the first place, I guess!

alan0899

G'day Mate,
Right thrust helps to keep the plane tracking straight when doing loops, & nose up type manouvers, eg. it won't yaw left, as much, but this depends on lots of variables, like type of plane, props & so on.
Down thrust, is used to stop the plane climbing excessively as speed is increased, again lots of variables, eg. airfoil shape, speed range, balance point & so on.
So, just set it up as best you can & fly it, if you need more or less of either right or down thrust, you will be able to adjust accordingly as you trim it, which in my case, can take weeks to get the plane to fly the way I like.
Too much or too little of either of these things, within reason, won't make your plane fall from the sky, they are just compromises to help you control the plane.

wsmalley

My Feedback: (6)

Thanks for the informative explanation, Mate! I seldom try to come in behind someone else's work, or change engines but thought I'd give it a try. I did find that the correct settings are 0 deg down, and 2 degrees right. Guess I'll try my laser and see how close I can get. All I have to do is figure the correct thrust line, hmmmmmmm. Bill