Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Sat, 03 Aug 2002 23:43:54 -0400
Message-ID: <redirect-1681616@logan.com>
Reply-To: "Dan Schaefer" <dfs155@earthlink.net>
From: "Dan Schaefer" <dfs155@earthlink.net>
Subject:  LNC2 Trim Tab Size
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To Rob Wolf, re: size of aileron trim tab.

Rob, I used the same type of tab you're considering (I have an older 235)
and find it perfectly adequate.

My tab is an 8 inch long (approx.) section of the extruded Al. hinge
material, located close to the inboard end of the aileron. I cut a slot in
the trailing edge of the aileron (mine are blunt, about a quarter inch
thick, per the instructions for my airplane) on the aft center-line. A
number of 1/8" holes were drilled in the inserted aluminum, which was then
layed on the top of the aileron in the position it would be when inserted in
the slot and three or four of the hole locations marked on the surface. I
drilled 1/16" pilot holes in the trailing edge to line up with the holes in
the aluminum to provide for aluminum pins to be floxed in to insure the
hinge wouldn't pull out. (This was probably over-kill as filling the holes
with flox would likely have been sufficient since there's little stress on
the trim tab in shear).

In any case, the slot was primed with flox, the hinge holes were packed with
flox and inserted till the hinge loops were just flush with the trailing
edge. Flox was forced into the through-holes and the pins were inserted (I
made the pins slightly short so the flox could be sanded flush with aileron
skin). Before the flox cures, you've got to be sure to clean off any
squeeze-out around and in the hinge loops or you'll play hell attaching the
trim tab later.

I riveted an aluminum control horn to the underside of the tab for
actuation. I didn't like the idea of the additional weight of the servo to
the aileron, so I installed it inside the wing (accessible through the
inspection plate on the bottom of the wing - the primary reason for the
lateral location of the tab was to line up with this access hole, by the
way) and devised a small "walking-beam" reversing lever attached to the
inboard edge of the aileron to transfer the servo push-pull to the tab. By
arranging the lever so the input from the servo was aligned with the aileron
hinge, control movements of the aileron has very little effect on the tab
position.

Bottom line, the 8 inch piece of hinge provides more than enough trim
authority for my airplane regardless of whether I have a passenger or not
and for any other flight conditions I've encountered. In fact, the trim tab
is never very far from neutral because it's quite effective. The only
down-side is that it's not as elegant as the cut-in tab but it meets my KISS
requirements just fine. (Incidentally, I will measure the exact length of my
tab the next time I'm at my hangar, if you're interested).

Hope this helps some,

Dan Schaefer