T-88 Epoxy, Versus Titebond II tests (2024)

Mar 28, 2017, 05:53 AM

• #1

epoxyearl

Thread OP

Discussion

In 2014, I started a project that needs a dependable, trustworthy glue for secure joints.

Using 3/4" square Sitka Spruce, #1 White Pine, and 1/4 " Aircraft Plywood, several test pieces were made in duplicate. The 3/4 " Sq strips were cut to a 9" long scarf joint..The Plywood was set on edge into grooves 1/4" wide X 1/4" deep.

All mating surfaces were carefully sanded to a gap-free fit, then scraped with a furniture scraper to a high gloss finish, where possible. The wood had been 'acclimated' for 3 days inside the building area at around 75 degrees. The glues were applied to the test pieces, and clamped between straight hardwood blocks about 16" long. Left alone for three days, they were unclamped, and stood in place in an unused corner of the garage.

In the three years since, those pieces have been standing in the corner, waiting for the 'test'......The results were anti-climactic,,,,All the glue joints held, with none separating at the connecting surfaces, but with the wood breaking Outside the areas !

I'm not sure where one glue could be described as 'better' than another, in this situation, although I'll use the T-88 as recommended by the pros.

Mar 28, 2017, 07:07 AM

• #2

sensei

Although I'll use the T-88 as recommended by the pros.

So who are the pros?

Bob

Mar 28, 2017, 09:38 AM

• #3

epoxyearl

Thread OP

F A A, as far as recommending the Epoxy.......I'm building an Ultralite, and although it's outside their 'Jurisdiction', I'm sure if I crash, they'll all nod their heads and say " yes he should have used T-88 Epoxy "....

I saw the results of the shear tests, and I trust each one equally....

Mar 28, 2017, 10:02 AM

• #4

campbelltf

I found a lengthy write up named The Glues We Use - by Graham H. Hicks. Mr. Hicks tested several brands of epoxy, aliphatics, CA's, and others like Ambroid and Sig Super Weld. He had access to a machine which applied and measured shearing forces. He was very methodical gluing 3 sets of identical blocks with each glue in the same environment, etc. In the end, ALL of them survived over 5,000lbs (yes, five thousand) of shear force.

For me, it seemed to show that application technique (surface prep, correct amounts) and curing/drying environment are more important than which adhesive used as far as strength goes for model building. Also choosing your glue based on working time, viscosity, and gap filling can be the primary decision drivers. Sounds like you were able to comment on longevity of glue strength which was not part of Mr. Hick's tests, but it sounds like time also doesn't have a great effect.

Mar 28, 2017, 11:24 AM

• #5

epoxyearl

Thread OP

Part of my training as an apprentice was repairing Wood Yachts, in the 40 to 50 foot range....Amazingly a large percentage of companies used flexible compounds below the water line...(Bedding Compound, White Lead caulking , and the like)....coupled with the Cypress wood, and to a large amount, Mahogany Planking, to seal out the water..

Above the water line, I used mostly the Powdered Resorcinal Mixes during that time. (60' s and 70's). They seemed identical to the holding powers of today's glues- any fractures were not at the glued joints...

Not to any 'Ulterior Motive', I had nearly forgotten about these pieces, and their 'longevity'... My Grandson and I are remodeling the garage with new Drywall, Paint, Heat, and Air Conditioning....They were 'rediscovered' during this effort.
I have no test equipment to show 'shear' strength, but a mighty blow with an 8 pound hammer duplicated any 'crash' impact.

I believe we'll put the remnants submerged in water, for a while, then check those results, as well.

Mar 29, 2017, 07:24 AM

• #6

Mike Denest

AC 43-13-1B covers wood repairs for certificated aircraft while the standard document for experimental amateur built is CAM 18 (available from EAA). However, the principles contained in both documents are the same. Note that resorcinol is the only adhesive recommended by the FAA. Epoxy adhesives that meet a Mil Spec, Aerospace Material Spec (AMS), or Technical Standard Order (TSO) are acceptable for use in certificated aircraft. These recommendations are reflected in experimental amateur built techniques.

T-88 is not "recommended" but meets one of the requirements for an acceptable epoxy adhesive, therefore, it is "acceptable" as an adhesive. As in all wooden aircraft construction, clean, tight joints are a must. Epoxies do a better job at gap filling but resorcinol is a lousy gap filler. The joint can actually be weakened if not precise.

Mar 29, 2017, 10:24 AM

• #7

carlgrover

A few other considerations when choosing the type of glue to use are cleanup, sandability, working time, glow fuel resistance, and wood warping.

Give me woodworkers glue as it is easy to wipe up the excess with a slightly damp sponge. It is also more sandable than epoxy.

Woodworkers glue is a nightmare for laminating because it will warp wood. CA or epoxy are much better choices.

If you need an instant bond to hold parts together, you won't beat CA. For other things like joining wing halves, epoxy would be a better choice due to a long open time.

I'm going to be gluing on a fin tonight. I will likely use epoxy so I have time to get it placed accurately. I will also likely tack glue the joint in a few places with CA to keep it in place while the epoxy cures.

carl

Mar 29, 2017, 11:21 AM

• #8

epoxyearl

Thread OP

I agree with the epoxy for laminating, as opposed to white glue...But in my case, there are six 1/8" thick spruce strips to be glued into the Rudder outline, and since the pieces are clamped heavily, warps are non-existent...More so, the strips are water-soaked over night for pliability, and the White glue is right at home in that circ*mstance...

If I used epoxy for the laminating, the strips would need to be soaked in the fixture overnight, allowed to dry for a couple of days, then epoxied..

The 'scarf' joints in the tests were as in the picture...none broke at the glue lines...Goody !!

Click to enlarge, and you can see the fine joint, and how well the grains match...

Mar 29, 2017, 02:45 PM

• #9

wizard of odd

[QUOTE=epoxyearl;37206307...none broke at the glue lines...Goody !![/QUOTE]

Earl, discussions like these are way more relevant when you plan on flying the aircraft from the sky, not from the ground.

It reminds me of the old joke about bacon and eggs for breakfast: The chicken is involved, but the pig is committed....

I guess you're more of a "bacon" kind of modeller

Keep up the good work!

Marius

Mar 29, 2017, 06:16 PM

• #10

epoxyearl

Thread OP

Hi Wiz...I didn't want to bring that up, so much as my great satisfaction with the comparative holding power of the two glues I tried....
One is about 5 times the price of the other, and don't you know they're both equal as far as I can tell with my small tests...
I've stopped using epoxy in any of my models..NOT because of the cost, but just in view of the security of the joints.

Mar 29, 2017, 07:35 PM

• #11

campbelltf

This is where I'm trying to get myself. Even though I see empirical evidence that wood glue is perfectly strong enough to hold a firewall in place I'm still trying to shake my long held belief in the need for epoxy. I guess I'm not chicken enough yet.

Mar 29, 2017, 08:21 PM

• #12

epoxyearl

Thread OP

I just repaired a demolished ARF Taylorcraft from the Landing gear forward...I used Titebond only during the rebuild, reassembling the 'puzzle' and adding reinforcement where necessary.
The model is a 1/4 Scale, with a zenoah 26cc engine.

I understand where your concern lies, trying to wean yourself from epoxies.
I'm an Ancient Modeler, building before Epoxy was in widespread use, when Ambroid and Testors were very popular..In that era, we couldn't believe any adhesive that cured in 5 minutes could be trusted. Then Hot Stuff was introduced and we were truly amazed.
Now, at 76, I'm in no hurry , preferring to enjoy the build in a more leisurely fashion..
-Having to 'unlearn' old habits can be scary......
If you have the patience to wait 24 hours, you'll find the firewall glued to the fuselage sides with Aliphatic resin is just as secure as with epoxy.

Mar 30, 2017, 05:11 AM

• #13

sensei

If you have the patience to wait 24 hours, you'll find the firewall glued to the fuselage sides with Aliphatic resin is just as secure as with epoxy.

If you don't have the luxury of time, then CA will certainly secure your firewall as well as epoxy if properly executed.

Bob

Last edited by sensei; Mar 30, 2017 at 06:20 AM.

Apr 06, 2017, 01:55 PM

• #14

2 Piece

Here are some good links about glue strength. One thing about epoxy is that it withstands vibrations better than most wood glues. Not all the forces our models encounter are sheer forces. I'll stick with T-88 for landing gear blocks and fire wall installations.

www.woodcraftmagazine.com/posts.php?id=56

http://www.finewoodworking.com/2007/...ing-wood-glues

Apr 15, 2017, 07:56 AM

• #15

epoxyearl

Thread OP

I have a couple of pictures of the results, in 3/4" square White Pine, the majority of my build.

This wood is two years glued, exposed to the elements of Rain , Sun , and Freezing Temperatures.. I'm satisfied the T-88 Epoxy is as strong as necessary..