On Fri, 06 Jan 2006 18:00:32 GMT, Richard Lamb
wrote:



Roger wrote:

On Fri, 06 Jan 2006 05:59:37 GMT, Richard Lamb
wrote:

If a fiberglass patch on an aluminum backplate stays on for one entire
trip around the pattern, I'd be flat out amazed...

Properly preped it'll stay on as well as the paint, better in some
cases. Without a good degrease and prep I doubt it'd stay on past the
run up. :-)) Many of our "plastic" planes have Aluminum to
glass/resin bonds.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com


I know, Roger, but....

Someone who is actually building a plastic plane should step up to the
microphone and tell how those metal plates are installed.

As for the three methods described below you will find photos at
http://www.rogerhalstead.com/G3_file.../glasair11.htm along
with some description. As you'll note, these are not just "slapped"
in. :-))

It depends on which part and where.
Typically, you'll find captive nuts like the K2000-4 (If I remember
the number correctly) both pop riveted in place and then have the
"ears" glassed in with two layers of cloth and resin. The "glass
serves as much to keep from losing the captive nuts as it does
structurally. Lose one of those suckers and it means cutting a hole
in the horizontal stab, glassing in a new K2000-4, and then patching
the stab so it looks like you never had to bore a hole in it.

The backing plates for the engine mount attach bolts (which are held
under considerable compression) are of 0.10" SS. The face and edges
are thoroughly sanded and these are bonded on the face and sides to
the engine mount attach point reinforcements using a resin and mill
fiber mix. For six attach points there are a total of 96 individual
lay-ups just for the reinforcements, plus six more two layer lay-ups
used for forms.

The third method which is *similar* to what he's asking about is the
fuel tank filler neck. There the outer ring is set into a tight
fitting opening just a tad forward of the windshield. This pieces is
held entirely by a resin and mill fiber mix. which is built up around
the neck. This is in an area which would receive pretty much the same
kind of stresses as the cowl crack and receives a lot of stress from
expansion and contraction of the machined Aluminum filler neck and
cap.

*However* how I've seen a cowl patched, and the only way I've seen it
done was to first, "stop drill" the crack. Then a small "doubler" was
made out of Aluminum about the same thickness as the cowl. As the
crack included the leading edge of the cowl where the edge is rolled
back and extended back about 2 inches. ( Of course the thing would
never crack where it's easy to fix)

(Yah ever try to type with a lap full of a 16# cat? At least he
didn't have his claws out when he jumped up.)
Slight distraction there.

At any rate, The entire area was thoroughly cleaned, sanded, cleaned
again, the doubler fitted, then flush riveted in, and finally the
whole thing was glassed over on the inside with two layers of glass
and resin. The glass was a last resort as the doublers were refusing
to hold.

Hmmmm... Good thing I'm not writing and this has a back space key.
He just knocked over the waste basket. I think I have a cat who wants
some attention.:-))

I know of no structural design that has aluminum plates "glued" on to
glass.

Nor do I, but didn't he ask about patching a cowl crack? It is
structural, but only for vibration and a slight wind load. Of course
it does depend on where in the cowl as well and I'd still want to use
a doubler..

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

My best guess is that they get "bonded in" by covering them with more
layers of glass. - in effect, the metal is burried inside the glass.

That's not he case here.


Richard (the skeptical cave) Lamb