Fiberglass adhesion to aluminum?

Sorry Dave, backing plate made me think spinner.

Richard



wrote:

Thanks for the info.
BTW, this is on the cowling, not the spinner.

Dave
Dave S wrote:
wrote:

How well does fiberglass adhere to aluminum?
What system is better.
I have easy access to the West system chemicals.

Any hints? Alodine first?

Thanks

Dave


You have to sand the AL to roughen it up, to provide something for the
epoxy to bite into. The hardpoints in the Velocity construction are
prepared in this manner. No alodining, no painting. Coarse grit
Sandpaper to roughen. I want to say we used Velocipoxy resin and
hardner, or alpha Poxy, on our work.

I am more concerned about the need to BALANCE the spinner, and if you
apply a layup on one side of the bowl, you may need to put another layup
on the other side to provide some sort of balancing effect. I am not
exactly sure of how much force is involved at only 8-10" from the hub at
the RPMS involved. I've never patched a spinner in this manner but
intuitively it COULD work.

Dave

I did some testing on this a while back.

West systems epoxy /1 inch wide fiberglass tape on bare aluminum sheet
1 square inch of adhesion area
peel strength tested

No surface preparation --- less than 1 pound of force peeled it right off.
sanding --- not much better - maybe 2 pounds of pull
Sanding and etching --- At least 20# - broke the fiberglass tape, and
it never did come off.

If the surface is prepared properly, with etchant, it will work. Otherwise
forget it.


Ron Webb



wrote in message ...
I've got some slight cracking in my aluminum nosebowl and have stop
drilled them twice.
I'm considering backing the cracks with fiberglass in hopes to keep the
vibration down.
How well does fiberglass adhere to aluminum?
What system is better.
I have easy access to the West system chemicals.

Any hints? Alodine first?

Thanks

Dave

One thing to keep in mind is that long-term it is difficult to keep a bond.
This is largely due to aluminum expanding and contracting with temperature
more than Fiberglass does. If the part is kept temperature stable it will
last longer than, say, a part that is close to the engine or exposed to
daily solar cycles. Mechanically bonding the two with some sort of rivit or
screw might help.

D


"Ron Webb" wrote in message
...
I did some testing on this a while back.

West systems epoxy /1 inch wide fiberglass tape on bare aluminum sheet
1 square inch of adhesion area
peel strength tested

No surface preparation --- less than 1 pound of force peeled it right off.
sanding --- not much better - maybe 2 pounds of
pull
Sanding and etching --- At least 20# - broke the fiberglass tape, and
it never did come off.

If the surface is prepared properly, with etchant, it will work. Otherwise
forget it.


Ron Webb



wrote in message ...
I've got some slight cracking in my aluminum nosebowl and have stop
drilled them twice.
I'm considering backing the cracks with fiberglass in hopes to keep the
vibration down.
How well does fiberglass adhere to aluminum?
What system is better.
I have easy access to the West system chemicals.

Any hints? Alodine first?

Thanks

Dave

According to the product specification sheet for Belzona 1111 (Super
Metal).
Tensile shear adheasion: When tested in accordance with ASTM D1002,
using degreased strips, grit blasted to a 3-4 mil profile, typical
values will be: aluminum 1,800 psi (126 kgs/cm2), mild steel 2,700 psi
(190 kgs/cm2), polyester/glass fiber 700 psi (49 kgs/cm2) [breakdown
in substrate], stainless steel 2,800 psi (197 kgs/cm2)

Another great thing Belzona has over other materials is the fact that
it does not rust, rot, corrode, or shrink. No solvents. 100% solids.
Chemical reaction cure.

I did it today.
sanded the area with 80 grit and alodined it to brighten it up.
mixed up some epoxy and put 3 layers of fiberglass.
Touched it up with a heat gun since it was 60 degrees in the hangar.

Didn't use any primer, just the epoxy.

If it lasts 10 years, I'll be happy.

Thanks all for the tips!!!!

Dave


Richard Riley wrote:
On 6 Jan 2006 18:20:44 -0800, "Clay"
wrote:

:According to the product specification sheet for Belzona 1111 (Super
:Metal).
: Tensile shear adheasion: When tested in accordance with ASTM D1002,
:using degreased strips, grit blasted to a 3-4 mil profile, typical
:values will be: aluminum 1,800 psi (126 kgs/cm2), mild steel 2,700 psi
190 kgs/cm2), polyester/glass fiber 700 psi (49 kgs/cm2) [breakdown
:in substrate], stainless steel 2,800 psi (197 kgs/cm2)
:
:Another great thing Belzona has over other materials is the fact that
:it does not rust, rot, corrode, or shrink. No solvents. 100% solids.
:Chemical reaction cure.

The problem is that like any adhesive bonding to aluminum, the bond
can fail over time if you don't use a corrosion inhibiting primer of
some kind. There are very long specifications to do a certifiable
bond to aluminum.

Now, for a cowl it would probably be fine.

I beg to differ. Belzona 1111 is not like the typical adheisives
available on the market.
With proper surface preperation, there will not be any bondline failure
with Belzona 1111. This has been documented by many independent and
government testing labs. Even the necular regulartor commission
approves Belzona 1111.
Belzona 1111 has been used by the USAF to rebuild areas around the
windows on KC-135 tankers.

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

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.

Oops...Make that 12 more two layer lay-ups, not six. There are two
for each side of each of the six reinforcements.

And some wonder why a G-III takes longer than some scratch built
planes. :-))



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

wrote in message ...
I did it today.
sanded the area with 80 grit and alodined it to brighten it up.
mixed up some epoxy and put 3 layers of fiberglass.
Touched it up with a heat gun since it was 60 degrees in the hangar.

Didn't use any primer, just the epoxy.

If it lasts 10 years, I'll be happy.

Thanks all for the tips!!!!

Dave



The alodine will give a pretty good bonding surface...

I had some fretting on my 1948 Bellanca cowling. It was worn clear thru.
Cleaned the area. Built up the area with epoxy and micro-balloons. Still
there 15 years later.
--
Cy Galley - Bellanca Champion Club
Newsletter Editor-in-Chief & EAA TC
www.bellanca-championclub.com
Actively supporting Bellancas every day



wrote in message news
Thanks for the info.
BTW, this is on the cowling, not the spinner.

Dave
Dave S wrote:
wrote:

How well does fiberglass adhere to aluminum?
What system is better.
I have easy access to the West system chemicals.

Any hints? Alodine first?

Thanks

Dave


You have to sand the AL to roughen it up, to provide something for the
epoxy to bite into. The hardpoints in the Velocity construction are
prepared in this manner. No alodining, no painting. Coarse grit Sandpaper
to roughen. I want to say we used Velocipoxy resin and hardner, or alpha
Poxy, on our work.

I am more concerned about the need to BALANCE the spinner, and if you
apply a layup on one side of the bowl, you may need to put another layup
on the other side to provide some sort of balancing effect. I am not
exactly sure of how much force is involved at only 8-10" from the hub at
the RPMS involved. I've never patched a spinner in this manner but
intuitively it COULD work.

Dave