# Polyurethane glues?

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#### Mike.Smith

##### Member
Are polyurethane glues like Gorilla Glue suitable for any aspects of aircraft construction? I have used it with great success building furniture, but of course airplanes are not furniture.

#### George Sychrovsky

##### Banned
The gorilla glue is the same stuff as the expanding insulation foam for filling cracks and gaps, its about as strong as dry gorilla snot

#### orion

##### Well-Known Member
To interject a translation of the above - not very.

The polyurethane has the same basic properties as Clark-Foam, the material commonly used for surfboards. It ends up with a brittle, fryable surface (it damages easily) and the whole makup of the glue ends up being realtively susceptible to shock and vibration, at which point it just disintegrates and comes apart.

It's use on parts that are not subject to repeated loads and/or vibration is OK, but of course that's not an airplane.

#### Falco Rob

##### Well-Known Member
"Are polyurethane glues like Gorilla Glue suitable for any aspects of aircraft construction?"

Absolutely - you can use them to build your workbench . . and nothing else.

#### Medic9204

##### Well-Known Member
What about Liquid Nails and stuff like that?

#### wally

##### Well-Known Member
The Liquid Nails would probably work ok on something like attaching foam ribs to plywood when building an ultralight. Other than that, no.

If you are thinking about trying to save  on glues when building something like a "real" airplane with a decent size engine, you aren't going to save much. The cost of glue for a wood airplane is a small percentage of the complete expense.

For wood, use T-88 epoxy or whatever the plans call for. You will sleep better at night knowing it won't be a failed glue joint that "bites" you.

Oh, are you asking what liquid nails is made of? Just re-read your post. I think it is an organic adhesive refered to generally as mastic. I am sure someone else will know.
Good luck,
Wally

#### Falco Rob

##### Well-Known Member
Wally is right on the money.

To put things into perspective -

The cost of glue as a percentage of the overall cost of an aircraft is miniscule - probably about 0.5% (about $500 in$80K in my case)

Considering that your very life may depend on it there doesn't seem to be a good arguement for skimping on it.

Money can be saved in lots of inventive ways, but cost cutting on structural issues can lead to a world of hurt.

#### Medic9204

##### Well-Known Member
Money isn't really a concern for me. I'm more looking at availablity and ease of use. I don't think you can get T-88 at the hardware store.

What does anyone think about Aircraft Spruce's "All-Purpose Structural Adhesive?" It claims "similar" properties to T-88 but is available in a slower gel time (up to 2.5 hours). Is there any disadvantge to this product in the end result?

Wilke

#### Medic9204

##### Well-Known Member
Dried gorilla snot

How stong IS dried gorilla snot, anyway?

#### Falco Rob

##### Well-Known Member
In response to your second post - you don't see many gorilla's with their finger glued up their nose (well . . . not forever, anyway) so I guess the answer is - "not very" !

Back to the subject of glue - Have you considered West Systems epoxy?

I'm using it for exactly the reasons you've quoted - it's very user friendly and it's readily available (even in Aust).

The primary reason for my choice however is that it was specifically designed as a wood adhesive, not a general purpose glue.

#### org

##### Well-Known Member
I've used T88, APCO, resorcinol, and West System epoxy as glue at different times. They all work well, with resorcinol being the most critical of conditions and fit of parts.

The APCO you ask about is easy to use and shares the T88's tolerance for temperature, and is cheaper to boot. I've always liked it.

Right now I use West System. It's not as viscous as the others, but can be thickened by adding SMALL amounts of colloidal sylica. West seems to be pretty available locally at least in larger metro areas. For me, the West is easier to work with and makes for an easier cleanup of squeezed out glue. Since it has several hardeners it can be used for glueing, laminating of fiberglass, and protective coating.

Your mileage may vary so far as ease of use is concerned, but if you use good techniques, I think any of the epoxies mentioned will do a good job for you.

Olen

#### Bluerooster

##### Member
Epoxy or Resorcinol. According to AC 43.13.1b Resorcinol is the only approved adhesive. But the Epoxy adhesives are mentioned as being acceptable. Resorcinol requires the parts to fit very tightly, with no sanding to fit.