Gorilla Glue?

http://www.gorillaglue.com/theglue/

Any opinions? Is a two-part epoxy like T-88 inherently superior to a
one-part catalyzed polyurethane? Why?

One thing is the level of craftsmanship required.
Polyurethane glues need exceptionally tight joints to
develop any strength. Where there is any air space
the glue will "foam" up. The foam has very little
strength...

T-88 is more of a gap filling glue, and much more
consistant.

Richard

Corrie wrote:

http://www.gorillaglue.com/theglue/

Any opinions? Is a two-part epoxy like T-88 inherently superior to a
one-part catalyzed polyurethane? Why?

On Mon, 18 Aug 2003 16:36:46 GMT, Richard Lamb
wrote:

One thing is the level of craftsmanship required.
Polyurethane glues need exceptionally tight joints to
develop any strength. Where there is any air space
the glue will "foam" up. The foam has very little
strength...

T-88 is more of a gap filling glue, and much more
consistant.

Richard

Not only that T-88 cures slowly. It's best for gluing wood. You lay
some on a scarf joint and it will migrate into the wood over a period
of hours before it cures. This gives you a real strong bond once it
cures. Experiment with it. I've made but joints with it using spruce
and Canadian white pine, let them cure for two days, and tested them.
I've put them in a vise and smashed them with a hammer, the wood
almost always fails somewhere other than the glue joint. In other
words, the T-88 joint is stronger than the surrounding wood.

Of course that's a problem in some cases because the added strength of
the glue joint actually concentrates the stresses at that strong
point. Most people don't understand that but here's a simple example:

Take a yard stick and clamp one end of it to a table. Put a 50 pound
weight on the other end and watch what happenes. The whole yard stick
will bend like a willow and support that load.

Now go out to about 30 inches on the yard stick and put a support at
that point near where you are going to place the load. Put the load
on it and the stick will snap at the support point. What you did was
concentrate all the stress at the point where you beefed it up. You
need the whole stick to take the load, not just one tiny little point.
The problem wood builders have is that many of them don't follow the
plans and they beef up a certain area using T-88. All they do is
concentrate the stresses at those strong points and can actually cause
a failure because of it.

Same thing with T-88 itself. The stuff is so good, the scarf joint
won't be the point of failure but the loads will concentrate there and
cause the wood just outside the scarf joint to fail.

Be careful. Follow the plans. I saw a guy add extra drag braces to
his Minimax wings once. Later on they caused him problems because of
this. The wings didn't flex enough to take the turbulence loads.
They were too rigid. He had to cut them out and destroy a perfect
fabric job to do it.

Badwater Bill

(Badwater Bill) wrote in message . ..
On Mon, 18 Aug 2003 16:36:46 GMT, Richard Lamb

....snip all...

Thanks very much, guys. I appreciate it. (Also, a techie thank-you
to the geeks at google - my message had the same title as a
three-year-old thread containing very useful info, so it appended my
note to that thread. Gotta learn to use google to search inside the
newsgroup.)

Corrie

Does T-88 cure to a flexible state or a brittle state?

How much flexing can it take when cured?

I know it is poor craftsmanship to glue different materials together,
but how well would it handle gluing two layers of different material
together, with the materials having different rates of expansion. For
example, plastic glued to aluminum, two different thicknesses of
aluminum glued together, fiberboard and spruce, etc.

Thanks for any info.

Gyro,
I have read about aluminum bonding as told by I believe jack lambe
(spelling?) and the consensus is that unless you are able to etch, prime and
then bond with a high quality control then bonding aluminum to aluminum is
not recomended. The cause for failure of the bond is that the bond line is
to the aluminum oxide that forms rather quickly on the surface of the
aluminum and not the base metal. therefore a weak bond and one that most
likely will fail.

As to wood to aluminum I have not a clue, I have seen aluminum plates bonded
to wood as a bearing plate and as such would really not be adversely
effected by a failure of the bond line as the bolt would hold in place at
any rate.

Fiberboard I can reasonable say will fail before t-88.

as to the flexibility the flexural modulus of t-88 is 375,000 and that would
compare with nylon at 380,000 or abs plastic at 405,000, stiff but not
really brittle.

all the best
Sean "dusting off the sawdust" Trost
"gyrobob" wrote in message
om...
Does T-88 cure to a flexible state or a brittle state?

How much flexing can it take when cured?

I know it is poor craftsmanship to glue different materials together,
but how well would it handle gluing two layers of different material
together, with the materials having different rates of expansion. For
example, plastic glued to aluminum, two different thicknesses of
aluminum glued together, fiberboard and spruce, etc.

Thanks for any info.

You could start here. http://www.thistothat.com/index.shtml
"gyrobob" wrote in message
om...
Does T-88 cure to a flexible state or a brittle state?

How much flexing can it take when cured?

I know it is poor craftsmanship to glue different materials together,
but how well would it handle gluing two layers of different material
together, with the materials having different rates of expansion. For
example, plastic glued to aluminum, two different thicknesses of
aluminum glued together, fiberboard and spruce, etc.

Thanks for any info.

In article ,
(Corrie) wrote:

http://www.gorillaglue.com/theglue/

Any opinions? Is a two-part epoxy like T-88 inherently superior to a
one-part catalyzed polyurethane? Why?

A problem with a lot of polyurethane glues is that they eventually fail,
due to water vapor in the air. That is what causes poly foam to
self-destruct over time.

I would not recommend poly glues for long-term structural applications.

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"Jimmy Galvin" wrote in message ...
You could start here. http://www.thistothat.com/index.shtml

No offense, but I don't think I'm gonna use Elmer's yellow glue for my spar caps.

One fellow told me about the way he built a gas tank.

Formed endplates and a wrapper - all about .040 5052-H32.

Then etched and assembled with PL-1 (polyurethane construction
adhesive) and a few pop rivets. Flanges faced out, btw.

He said it worked well, had so many hours on it.

But I never had the guts to try it.


Richard