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What glue for curved plywood bar stool back?

macgyver

Stainless
Joined
Aug 2, 2012
Location
Pittsburg, KS
I am most likely going to be making some bar stool backs in a few weeks, I have no problems making the parts and the pattern/mold, but I am not sure what glue I should use. I plan to use bender ply, 3 pieces 1/4" thick to get 3/4" thick. These are going to get upholstered and the sample they gave me to match is pretty scruffy, so they don't need to be high end, just need to stay together. I don't want to get carried away and go overkill on the glue, but I don't want to cheap out and have to fix these later either.

What would you guys suggest to use?

Thanks,
Jason
 
If you can clamp the pieces properly and don't mind a little post drying clean up, Gorilla Glue works very well, especially as you are going to cover the lay ups afterword.

Stuart
 
Actually, I'd recommend against standard yellow (or white) aliphatic resin or PVA glues. They can creep, and a bent lamination is exactly the sort of thing that will encourage creeping.

Resorcinol-formaldehyde glues are good for this application, as are most epoxies. Old-school hide glue is also pretty creep-resistant.

Maybe Stephen Thomas will comment on this...
 
Titebond dies too fast you need time to get stuff clamped
doing lamination.

made some cafe chairs that have a U shaped base and curved backs.
Gorilla glue works but is real messy, I used weldwood plastic resin glue.
powder you mix with water.
they are still in good shape almost 20 years later no creep.
 
Unibond 800 from a veneer supplier is very good. Mix with water and measure carefully.
Slowly add powder to the water in your mixing pot to avoid lumps. Power mixing with a small paddle is very helpful.
I use a battery drill and it speeds up the mixing time nicely.

Hard glue line, long pot life, no creep and dries in about four hours. Perfect for curved laminations.

Good luck,
Michael
 
Thanks guys, I have used unibond before at the old job to lay up veneer, but hadn't thought about it for this. Will look into all of the suggestions, of course the budget will dictate a less expensive option....

The parts are only app 11" x 16" and it is a pretty large radius, haven't measured it accurately but laying it on a table, over the 16 width the center is only app 1" off the table and it flattens out to closer to the bottom it gets.
 
The unibond is very reasonably priced.
That shape means your form will be a bit harder to make, a consistent radius from top to bottom is easier, however I do think the material will conform due to the gentle shape.

Michael
 
1/4" bendy ply is pretty flexible stuff, and thats a pretty mild curve. I think you'd be just fine with Titebond. Everyone talks about it creeping, but has anyone actually experienced it, other than at high heat?

If you are really concerned, urea resin is a safe bet, and easy to use. The only time I use Gorilla glue is for stuff that has to be boiled or steam bent, I handles that heat and moisture easily!
 
I go back and forth between epoxy and Titebond Extend for bent laminations.

A lot of what I have bent has exterior exposure, so WEST is it.

For interior items Titebond works well. I initially started to use it on the theory that it would be faster to de-clamp. I'm not so sure it is, maybe 1/2 the time in clamps? Because if the bend is tight, titebond will creep if it is unclamped too soon. And one is never quite sure if that is 3 hours or 8 hours.... Bending ply is very low stress, though.

Besides the often useful extended working time, Extend is stronger (per Tightbond's own data sheets) and I believe harder (more creep resistant) than original titebond.

WEST with fast hardener takes about 8 hrs at 70°F.

I have a bar stool in the office made from shop sawn 1/8" W.oak veneer about 35 years old that I glued up with Titebond. I think Extend had just come out and that I used that, but not positive. The stool is fine and nothing has delaminated or moved much. The blank did move over a couple weeks as it dried out. Basically, I glued up a 6" wide blank, and sawed it into 4 equal sort of S-curve legs, re-assembled with a center post.

With epoxy, if you establish the necessary over-bend for a given curve and laminae family (thickness, species, number of plies) It is pretty darn consistent as far as springback. With a "large number" of plies, there is very little springback even with fairly extreme curves.

When I started experimenting with Titebond Extend, I did seem to notice that the curve varied after being unclamped, and sometimes over several weeks or so, it actually got tighter as the moisture was fully off-gassed.

I think you are going to have trouble with only 3 plies (2 glue joints only 1/4" apart) in maintaining the curve with bending ply. But I don't think I have ever used it.

What I tend to do when making plywood bent parts, is laminate 1/8" baltic birch. Or sometimes one layer of 1/4 in the middle, and 2 layers on each side. (4 glue joints)

I am obsessive, but have also found that for me, I will not laminate parallel grain plywood. I always (OK, almost always) cross the grain at each glue joint.

I have often mentioned using urea resin when I started because it was one of the few "high end" glues on the market. It never worked well for me, and not long after starting I read several articles that indicated that urea glues essentially self-degrade over time, except in near perfect conditions. That played to my developing prejudice :) & I have not used it since.

smt
 
I have talked to Franklin (Titebond) chemists, and the formulations in the retail packaging (gallons on down) were renamed long ago, different from the industrial.

"Original Titebond" is actually their Hi Tack Assembly glue (higher solids, faster setting)

Titebond Extend is the original, regular Titebond

Titebond II & III are Multibond, self catalyzed PVA

Or were the last time I asked...

I use the TB Extend exclusively these days. It's been so many years since I bought 5 gal paila, I don't know if they are also renamed. Back then we used to have a pail of regular and slowset (for lams). Replaced yearly just in case.
 
Richard, that is interesting.

My memory is that back in the 80's when i started using TB extend, the PSI rating was 4,000, and original was around 3500.

(Edited: tried several times for direct link. Apparently in the following links you have to click on "physical properties" to get the strength and failure tables)

Now extend is rated 3,500
Titebond - Product

At room temp, Titebond "original" now has a PSI rating of 3600.

Titebond - Product

But notice that it has almost no resistance to elevated temperature! The wood failure is a mere 1% at 150 °F! (Meaning 99% glue failure). Strongly suggesting not a lot of heat resistance even between, say 70° & 150°.

ASTM D95 - 8(213) Standard Test Method for Strength Properties of Adhesive Bonds in Shear by Compression Loading

Then it gets even more interesting.

Titebond lll, supposedly the ultimate in their line, has a rating of 4,000 psi, but only 57% wood failure at room temp, and 0% overnight at 150°F

Titebond - Product

Coldpress veneer fails mostly in the glue, not the wood, at any temperature.

Of course any of these may still be adequate for the proposed work.

Extend still appears to be among the most durable of the offerings.

But I want my old Extend back!

smt
 








 
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