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<< Lancair Builders' Mail List >>
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Angier, I know it's probably too late to change things but, FWIW, here's
what I did for my Mac servo driving the aileron tab.
First, I didn't want the weight of the servo in the aileron since it seemed
to me that it would take an awful lot of extra balance weight to counteract,
as the balance weight moment arm is so short. So, I mounted it inside the
wing bay where the aileron bell crank is located. It's upside-down, mounted
to the inside of the upper wing skin on a plywood plate and is accessible
through the inspection hole.
To actuate the tab, I built a small reversing lever (about 2 inches long,
pivoted in the center) mounted on the outside of the inboard aileron rib,
with it's input point directly on the aileron hinge line in order not to
impart any input to the tab with aileron deflection. (This isn't exactly
perfect as, with large tab deflection, some slight servoing with aileron
movement occurs - but not enough to cause problems since I almost never need
more than just a touch of aileron trim - I keep things balanced by using
fuel equally from each wing as I go along). The lever is attached to the rib
with a small triangular aluminum bracket used to move the center pivot point
forward enough to allow the lever to be vertical at tab-neutral. The servo
push-rod penetrates the aft spar via a small hole, into which I epoxied a
short phenolic bushing. The tab actuator push-rod then comes off the lower
end of the lever and connects to the tab horn.
I molded a small fairing to cover the upper end of the lever since it sticks
up above the edge of the wing and aileron about 1/8 to 3/16 inch. It's about
1/4 in. high and maybe 1/4 inch wide. I doubt if it presents much drag as
the flow is very likely turbulent back there anyway.
When an aileron must be removed, for whatever reason, the servo push-rod is
merely disconnected from the upper end of the lever - I never have to
disconnect the wiring to the servo.
Probably sounds like a lot of extra work (it really isn't) but I abhor
adding mass to the flight controls and the attendant extra balance weight,
if it can be avoided by any means. Besides, it's one less cover plate with
all the work needed for that.
Cheers,
Dan Schaefer
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LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
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