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I just closed my wings last week at Aircrafters Builder Support Center in
Watsonville CA. I would like to extend my thanks to the guys up there, and
pass on something I learned about the Hysol bonds that we use to close out
wings, tails, stub wing skins, yada yada yada.
I was ably assisted by Harold Bunyi, an Aircrafters employee who has worked
for ten years at both the Lancair facility in the Philippines and at the
Redmond facility. Harold tells me that he has assisted in the building of
close to 60 Lancairs, so I listened to him pretty closely. (I also had the
opportunity to see his impeccable workmanship on other airplanes there at
Aircrafters, and was fortunate enough to have him glass in my aileron transit
tubes. I'm sure they won't leak...) He also has a degree in aeronautics,
and is a pretty nice guy, too.
My early 320 FB manual (circa 1993) calls for smearing on pure hysol, and a
1998 amendment pertaining to the horizontal tail calls for pure hysol
augmented by a hysol + flocked cotton mixture. For the record, I am using
the term "flocked cotton" rather than "flox", since "flox" implies to me an
epoxy + flocked cotton mixture rather than just the cotton by itself.
Harold had me do it this way, and says that this is how it's done now at the
various locations which form the international Lancair mega-conglomerate....
First, you mix up some hysol. Smear it onto the bonding surfaces on both
sides of the joint (i.e. both the capstrip and the skin). Then, scrape it
off, leaving only a very thin layer. The objective here is to wet out the
surface with hysol, but not put enough on to do any real bonding. If the
surface looks wet, that's good enough. If it looks gray, you probably have
too much hysol. Harold uses a metal paint scraper for this but I used a
plastic Bondo scraper. It doesn't really matter, but a tongue depressor
won't scrape off enough.
Since you put the scraped off hysol back in your cup, you now have almost as
much as when you started. Mix in flocked cotton until it's too thick to run.
The 1998 supplement to my manual says "like peanut butter" but I'd have to
say it's almost but not quite that thick. Perhaps like warm peanut butter
that's been stirred up a little. (Oh ... it should go without saying that
we're talking about smooth peanut butter -- not the chunky stuff....)
Put the thickened hysol on the capstrip. Build a little triangle-shaped
ridge along the length of the capstrip. You can use a tongue depressor for
this. The hysol + flocked cotton mixture can be zero thickness at the edge
building linearly to 3/16 inch thick in the center. (Just run the tongue
depressor along the edge, tilted so that it's 3/16 inch above the capstrip in
the center.)
Put the skin on and weight it down with sandbags, shotbags, dried cow chips,
or whatever you're using. You will notice that there are no heinous hysol
drips, since the flocked cotton keeps it from running. You can wipe off the
squeeze-out on the outside, but the stuff on the inside will stay in a nice
little bead along the junctions. However, there may be a small glob at the
corners, where squeeze-out comes from two directions at once.
When we closed out the wings, I briefly removed the sandbags from the area
around the aileron bellcrank access panel (leaving the bags on the, er,
leading and trailing edges) and reached in to remove the squeeze-out with a
plastic scraper. When I looked into the open fuel cap with a flashlight, I
saw a nice smooth bead of hysol -- no drips at all.
By the way, it takes a complete 1-quart kit of hysol to close out each 320
wing. It takes most of a 1-quart kit to close out two stub wing skins.
- 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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