Long term integrity of resorcinol glue

[Scott Black]

on my airplane there is no evidence of the glue drying out or turning to powder. also the airplane has never seen any direct moisture. So my iterest is more in any historical tracknrecord of degradation. knowing that Bellancas and Robins (which my Jodel is an ancestor of) have a solid service history is reassuring. I will read the paper quoted above. Thank you everyone.

 

[Aviacs]

The problem with Urea formaldehyde glues is that they have a known half life. Basically generic "urea" glues degrade in place to about 1/2 their original strength, in 20 years, give or take, based on humidity and heat/solar exposure. At least according to one of my manuals based on (citing) FPL data. This may or may not apply to specific brands which formulas could be tailored at the factory for somewhat more favorable characteristics.

According to my late chemist dad, (& unverified by me) Phenol-resorcinal properly mixed, clamped, and cured is essentially an analog of lignin, the bonding "resin" in natural/tree carbon fiber (wood) & is practically as durable under the same conditions.

smt

 

[Doran Jaffas]

Just to be clear, that is NOT the glue in question. Weldwood plastic resin glue is a UREA-formaldehyde glue and is not suitable for primary structure (I know, people do).

The glue in question is RESORCINOL-formaldehyde glue and IS suitable for primary structure.

The primary source for documentation on wood glues is the US Forest Products Laboratory. There are many scholarly articles there on Resorcinol-formaldehyde glue as well as Urea-formaldehyde and the epoxies such as FPL-16a (for which FPL stands for Forest Products Laboratory) and others. Interesting reading!

Yes,,, excellent information.

 

[geraldmorrissey]

I recently did a distructive test on a rib I built in 1965 with Weldwood Plastic Resin just for the hell of it. It has sat in an uncontrolled indoor environment with no varnish or coating of any kind. Hi humidity and +100/0 degrees F. Granted, no fatigue, however the glue lines remained intact when peeled, in tension, smashed and surgically dismanteled. In all cases the wood was split, shattered into kindling. Looks like pretty darn good adhesive. Back in the day it was pretty popular, however we never thought our planes would last 60 years.

 

[ToddK]

Pretty sure Culver Props still uses Weldwood Plastic Resin.

 

[BJC]

Pretty sure Culver Props still uses Weldwood Plastic Resin.

So do some others.


BJC

 

[TFF]

Weldwood glue is not used correctly. Failures are clamping without enough pressure and too cold of temperatures when applied, not degrading. What it wants is you working in a 100F shop and just short of wood crushing clamping. It does not penetrate the pores deep without help. A fillet of this glue does nothing. If you have a homebuilt in the 70s, it’s better chance than not it was glued together with Weldwood. I believe Culver elevates the temperature and only presses one prop a day. Building in Florida in summer with no air conditioning is not an issue. Wisconsin in a winter basement is.

 

[geraldmorrissey]

Scott, is it beyond the realm of possibility that a bit of the airplane could be sacrificed to address your concern? A dissected trim tab or control surface might be revealing and useful to other owners. Destructive testing means just that, so it will be important that its well planned. There are more then a few on this board that can advise on that. The next owner will appreciate your insight.
Gerry
Patrol #30

 

[BrianW]

Monday at 7:19 AM

ToddK said:
Pretty sure Culver Props still uses Weldwood Plastic Resin.

So do some others.
BJC

I asked Alana yesterday if this was the case. She confirmed it.
Brian W

 

[BJC]

BTW, the ideal wooden propeller is just strong enough for all flight loads, but self-destructs to protect the engine when it hits the ground.


BJC

 

[Doran Jaffas]

QUOTE="BrianW, post: 563113, member: 65758"]
Monday at 7:19 AM

So do some others.
BJC

I asked Alana yesterday if this was the case. She confirmed it.
Brian W
[/QUOTE]

On that note...Weldwood Resourcinol glue is the one to use. I did some wood failure tests with Weldwood and Elmer's resourcinol glue and the Weldwood was better.

 

[Rockiedog2]

In the 70s I was building Acrosport 1 wings. Had a 3 day layover in the Amarillo Holiday Inn so took enuf stuff to build a few ribs. Cold as hell. Heater couldn’t hold it 70 degrees and I was using Weldwood plastic resin. Got those ribs in the bed with me.
Weird.

 

[Pops]

Back when I was building the KR-2 with Weldwood Plastic Resin glue I did the gluing in the family room of our house where it was warm. You can use to much pressure in the glue joint and squeeze the glue out of the joint and have a starved weak joint.