wood glue

[n6346m]

I'm getting ready to order some wood for my L-2 from aircraft spruce. I need to get some glue as well. The aircraft spruce book has five pages of glue but I can't figure out what to order. The L-2 structural repair manual calls for a glue which conforms to spec AN-G-8 or commercially available Uformite CB-551. Do any of the glues there meet that spec or is there an FAA approved substitution available.

Bob Picard

[Guest]

Rescorcinol glue, look it up in AC43.13-1b.

Easier took this up => MIL-A-22397

Here is some=> http://aircraftproducts.wicksaircraf...ype=2&filter=1

[n6346m]

Thanks Dave

[Robert Lees]

I would agree with the use of Rescorcinol, commonly called Aerodux. It has its limitations, mostly in terms of its gap-filling abilities, which are poor, but is a good all-round adhesive. It is now sold as "Prefere". You have to be careful to mix it either by weight or by volume; each part has slightly different densities. I have a very small digital weighing scale for small quantities by weight.

But it's great advantage is that it remains liquid for quite a while (longer pot life), as you clamp the parts together and make final adjustments. It is dark brown in colour, and you may see it typically in wooden propellers between the laminations...it is quite striking.


An alternative is Aerolite. This is one-part powder, and one-part liquid. Again pros and cons. The pros include it has no colour, has better gap-filling qualities, has no pot life (you coat one wood part with the liquid, the other with the powder).

Cons: Once you put the two parts together, that's it, no movement time.

Structural epoxy wood adhesives can suffer from heat degredation. They are not allowed in the UK for that reason, but thay are permitted in the US homebuilding world, but I doubt allowed in the US Certificated world.

Whatever method is used, use the required clamping pressure. Like the photo attached.



Just my view.

Rob

[Guest]

This is from AC43.13-1b (change 1) chapter 1 page 4 (page1-4);

(4) Federal Specification MMM-A-
181D and Military Specification MIL-A-22397
both describe a required series of tests that
verify the chemical and mechanical properties
of resorcinol. Resorcinol is the only known
adhesive recommended and approved for use
in wooden aircraft structure and fully meets
necessary strength and durability requirements.
Resorcinol adhesive (resorcinol-formaldehyde
resin) is a two-part synthetic resin adhesive
consisting of resin and a hardener. The appropriate
amount of hardener (per manufacturer’s
instruction) is added to the resin, and it is
stirred until it is uniformly mixed; the adhesive
is now ready for immediate use. Quality of fit
and proper clamping pressure are both critical
to the achievement of full joint strength. The
adhesive bond lines must be very thin and uniform
in order to achieve full joint strength.

[N96337]

Wasn't it on this board that someone had helped on writing/updating the adhesive section of AC43? I remember on one of the boards I visit, getting to talk to the person. It was very interesting!!
John

[waltermrich]

I think you are right it was a few years back

[astjp2]

FPLA-16 was approved at one time but is almost impossible to find.

[Edwin Otha]

AC 43.13-1b with change 1 has a section on epoxy. I've used West Systems and have great results. The heat thing is a little overblown. In order to get any release of the cured epoxy the wood has to be nearly singed by the heat source. Until we start to have wood structures burst into flames by sunlight on the ramp I'll still use it.
EO

[Guest]

Edwin,
Yes what you said is 100% correct and in that section of AC43.13-1b it says that epoxies that meet the requirements
of a Military Specification (Mil Spec), Aerospace Material Specification (AMS), or Technical Standard Order (TSO) for wooden aircraft
structures are satisfactory providing they are found to be compatible with existing structural materials in the aircraft and the fabrication
methods to be used in the repair are acceptable.

Does West meet any of those specs?

Dave

[Edwin Otha]

Mil-A-81236 and ASTM D6416
EO

[skip]

A few years ago when I rebuilt my Taylorcraft wings I used Resorcinol. It is not as difficult to use as folklore would lead one to believe. Gaps are well within reasonable woodworking tolerances and the biggest difference with epoxy is the clamping pressure. As mentioned above, get a digital kitchen scale and mix by weight. That said, my Acrosport is going together with West Systems epoxy.
Epoxy does get gooey at moderately high temperature. The key spec to examine for your epoxy is the glass transition temperature. If the internal structure reaches this temperature, the epoxy will start too loose strength rapidly. It is difficult under normal circumstances to get internal wooden structures up to most epoxy's glass transition temps.

[kauaicuda]

The EAA loves T-88, is that not an option ?