Hi Colyn-
I hadn’t thought of that particular aspect. I did use e-glass rather than carbon
so it wouldn’t be as stiff and might allow some movement. Perhaps Lancair has a
suggestion? :<) The dimensions are meant as an aid to other builders, not
cast in stone. They’re just what the CAD program told me or I measured after the
fact.
I’ve never dealt with pressurization before and it adds a layer of
complexity that I don’t always account for. I’m an airframe mechanic but not an
engineer- my guess would be that the box itself would keep the bellcrank and
torque tube aligned. For the rest there’s the ball joints on the rod ends.
That’s why the twist, to keep the rod ends centered in each bracket for maximum
range of movement.
Now, if IV-P’s vary their wing geometry when they pressurize, all
bets are off.
One might think the aileron torque tube could be affected as it
spans a longer section of the fuselage and might be compressed to some extent.
It might not hurt to have some flex on one end. -Bill Wade
Sent: Saturday, June 18, 2011 9:15 AM
Subject: [LML] Re: IV Aileron Pressure Box Part 2
Bill,
so when your fuselage puffs out there, what will keep this all lined up to
close tolerance?
Colyn
On Jun 17, 2011, at 10:46 AM, Bill Wade wrote:
Two pictures show aligning the box to locate the forward
pivot/crosstube supports before bonding the boxes in place. It took a while to
puzzle out the instructions- page 17-22 shows the forward torque tube tab
upwards. It’s not that way on the ones I got. The thing I worried about was to
make sure there was clearance from the NG well housing and that the crosstube
would be high enough for leg room. The third picture shows how I went about
that.
I used Clark foam to fill the lower gap, then bonded the box with
Hysol followed by 2 E-glass BID on each side. I gather the bottom needs to be
free for movement during pressurization but I did use a couple of BID to make
a collar through the aileron pushrod hole. My intent is to make sure the box
couldn’t debond in that area and it’d remain sealed during pressurization. The
hole needs to be opened out to allow for the extra material. Also attach the
aileron pushrods to the lower bellcrank and check for clearance through the
range of motion to get the hole sized.
When all was done I discovered the wing pushrods aren’t perpendicular to
the aileron torque tube. The lower bellcrank and intermediate rod end had to
be rotated and the shaft holes redrilled until the bellcrank aligned with the
aileron rod end bearing. The forward hole ended up 0.20 inches closer to the
flange face than the aft one. The phenolic covers mistakes. The holes ended up
roughly 0.525 and 0.555 for the forward, 0.726 and 0.750 for the aft ones;
measured from the face of the box flange.
I realize this is more than you asked for and probably more than
anyone else wanted to read but I hope it helps. -Bill
Wade
<Aileron Box
001.JPG><6-12-09 012.JPG><Crosstube
003.JPG><015.JPG>--
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