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Message
I am fabricating the bed mount plate for my 20B in an
rv-8. my understanding, from Tracy's advice, is to offset the engine about
1 1/2 degrees to the right if I use his 2.85 drive.
Hi
Kevin,
Sorry I didn't think of
this before, but last weekend, I measured the offset of my friends RV-8 prop,
but never did the math to see what it came out to be. Basically, I put the
prop horizontal, and measured from the tail, to each tip. The difference
was 2 inches, on a 74" prop, which works out to 1.55 degrees right offset.
The reason I measured
this was to see what his offset was, because he says he doesn't need any rudder
in cruise. My RV-8 also required no rudder in cruise, and neither of out
planes had any offset in the vert stab. Curiously, the same measurement
shows that my RV-3 (-B drive) has 1.25 degrees of left offset, and I need a
buttload of left rudder in cruise. The only thing I can concluded is that
there is right offset somewhere in the in the tail. I can't tell if
the vert stab is offset, but it might be. There could also just be
something crooked that I can't spot. I didn't build the tail,
and fuselage, or I'd know if offset was put in.
Since I'm going to
the -C drive later this Summer, I'm more than a little interested to see how the
offset works out. Since there already seems to be some other right
offset force at work, I'll probably try flying the -C drive with the left
offset still in the mount. If I'm careful, it shouldn't be dangerous, and
then I can decide if I need to remove the current
offset. If I have to remove it, I'll shim the mount a half inch on
the left to do it. I'll also reposition the cowl to keep everything lined
up. The prop won't quite be centered, but I defy anyone to
notice.
Cheers,
Rusty
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