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<< Lancair Builders' Mail List >>
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In a message dated 9/2/01 9:16:00 PM, Jim Cameron wrote:
<<hey, it's a Lancair! After a while you don't expect anything to fit, you
just sit down and figure out what you have to do to get something you're
satisfied with.>>
I've just started on my 360 wingtips this week, and this quote made me roll
on the floor laughing! While I generally have had pretty good luck with
parts fitting each other, the wingtips are definitely less than optimal.
However, I happened on an approach which works fairly well, so I thought I'd
pass it on.
First problem was that the tips are different widths. The tip tops are about
one inch wider than the tip bottoms. Plus, while the tip tops fit in the
wing joggles rather nicely, the tip bottoms don't. (Probably because the
lower joggle is partly wing-top-and-D-section and partly lower-wing-skin.
The joggle is a straight line on top, but has a bend in the middle on the
bottom skin.)
First trick is to run a straight line from the wing root to the wing tip
trailing edge. Straightedge or string -- I started with straightedge but the
string works easier. Make the trailing edge of the tip line up with the
string and do what you need to so that the tip bottom fits in the joggle.
Some trimming will be required. Keep in mind that the trailing edge can be
adjusted somewhat with micro/flox later. Oh by the way, finish this entire
operation before trimming your ailerons.
Cleco the tip bottom to the wing. The manual suggests that a couple will do,
but I used about 5.
Line up the tip top with the tip bottom. You'll have to trim the outer edges
to get them even close to lining up. Also plan on trimming a whole bunch off
the inboard edge to line it up with the joggle in the wing. Cleco the tip
top to the wing. Again, more clecoes are better. I used about 6.
Run 2-BID around the outside for as far as you can. The manual suggests that
a few 1-inch wide strips will hold it in place until you can get the whole
thing with 2-BID, but I was able to get 2-BID from the front to about halfway
to the back. This really makes it rigid!
Take this opportunity to add flanges to the outboard aft end of the tip rib.
Do this with release tape on the wingtip. The objective is to extend the
wing joggle all the way to the back. You can gently pry the tip bottom down
to do the upper flange, and in a separate operation do the lower flange.
When you do this, one of the tip pieces (top or bottom) is clecoed into
place, and the other one is free. I used this operation to micro-closeout
the tip rib all the way back at the same time.
Tape the trailing edge together, add micro where you need it, and finish the
exterior 2-BID.
This is as far as I've gotten so far. The manual, umm, suggests an approach
for finishing the wingtip. The main lesson I want to pass on is that:
1) Yes, the tips don't fit together that well.
2) Cleco one piece to the wing and make the other one fit the first one.
3) Clecoing the parts to the wing help enormously in the fitting process.
4) Joining the top to the bottom along the outer edge, even partially,
rigidizes the assembly and makes subsequent work easier.
5) Don't despair. You can make a beautiful product even with poorly fitting
raw parts, and it really isn't that hard. (It only seems impossible before
you start...)
- Rob Wolf
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LML website: http://www.olsusa.com/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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