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Old 10-21-2020, 07:46 PM
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Default Thrust Vector Argument, please help!

I'm embarrassed to publicly admit I don't know this, but here goes:

If a single-engine tractor prop plane comes ARF with a +3 degree up incidence (crankshaft vs horizontal stab), What kind of elevator trim will be needed at med-hi throttle???

Specifics: NIB Seagull Yak 54 put together nicely by a friend who asked me to help tune the Saito 125 and do the maiden flight.

CG specified by kit was 3/4" behind the wing tube and acted tail-heavy, but flyable by pilot experienced with intentionally tail-heavy aerobats. I noticed that on landing approach, but during straight flight, main problem is it required TONS of up elevator trim. I eyeballed the crankshaft after landing and it seemed a little "off:" measured 3 degrees UP incidence crankshaft vs horizontal stab/turtle deck. Does that make the wing pull the plane down??? Lots of maiden crashes in the old thread, not all about the above issues.

I dont want to tweak two major things at once, so I recommended moving CG forward, then start putting washers on the firewall if trim still off