glue for bent laminations

Rick Thom

Member
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51
Hi all,
I am considering trying to make a chair that would employ bent laminations for strength... probably @1/8" lams. Is there anything special required in the way of glue, or is carpenters yellow or Titebond 3 ok?
Thanks, Rick.
 
There are those that claim White glue is best because of the longer set time. As for me I have been using Yellow for a long time and find it will stay smooth long enough for most laminationn applications. But that is my opinion and the experts who read more info than practice will always argue.

Back in the dark ages there was a veneer mill not far from a school I once taught WWing for the 7th & 8th grades. They would offer their culls and large bundles of defects. We gladly took these free goodies and had the students laminate to make small projects such as back scratchers, salad forks & spoons, desk sets and whatever they could imagine to make. We were very successful with working with Yellow glues and students didn't seem to run out of time during their glueups.

I feel white glue is lacking in so many bonding features that the risk of delamination from moisture exposure is more of a problem than the set time.

Maloff fans can start their preaching now...:wave:
 
My preference for bent stuff is plastic resin glue, like this. I've had yellow glue creep on me, whereas the plastic resin has not. Take that with a grain of salt, since I've not done a lot of bent lamination stuff, but that's been my observation and experience.
 
I use titebond original on everything.
Yes it creeps some, but has always held whatever I've laminated together.
Bendable staircase railing, etc.
 
I've used weldwood plastic resin glue and tightbond 3 with success. Weldwood is the stuff if you can't tolerate any springback (I was doing a 1 3/4" x 6" curved door jamb with a 40" semicircle that HAD to fit inside another as tight as possible). In the same house I did an eliptical french door jamb that was thinner and a bit more forgiving spacially. Over 5' there was about 1/4" to 1/2" spring away from the eliptical form on a 3/4" lamination. Tightbond is much easier to work with, especially if you've never used the plastic resin before, and I think they've got about the same open time.

John
 
Andy Rae (Furniture and Cabinet Construction) agrees with Vaughn and John. Plastic resin (resin powder/water powder). Open time- 20 min./20min. Clamp time- 1 hr./12 hrs.

I just happen to be reading his book.
 
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Thanks all for the input.
I made a table recently that involved veneers being placed on the curved apron similar to a demi-lune table but 6" wide. I hadn't had any experience with veneers previously and read a recent article in FWW describing the process and was quite surprised to see their experts recommending and using regular carpenters glue rather than hide glue. It appears that our modern glues have a very wide range of applications.
 
I've used weldwood plastic resin glue and tightbond 3 with success. Weldwood is the stuff if you can't tolerate any springback (I was doing a 1 3/4" x 6" curved door jamb with a 40" semicircle that HAD to fit inside another as tight as possible). In the same house I did an eliptical french door jamb that was thinner and a bit more forgiving spacially. Over 5' there was about 1/4" to 1/2" spring away from the eliptical form on a 3/4" lamination. Tightbond is much easier to work with, especially if you've never used the plastic resin before, and I think they've got about the same open time.

John
Springback is related more to the number of laminations than to the glue or the thickness of the laminations. A good guide to the amount of springback you will encounter is the equation:

y = x/(n^2)

Where:
y = springback
x = the original amount of deflection
n = the number of laminations

So the best way to minimize springback is to increase the number of laminations. Springback decreases with the square of the number of laminations.

Mike
 
I think the formula for springback applies to the original springback.

Normally I appreciate the creep of PVA (Titebond, Bordens Carpenter, etc.) when I am joining different species with slightly different expansion coefficients, or similar woods where the grain isn't perfectly aligned. It also works well for bentwood laminations, but (at least in theory) the pressure remains and the PVA will creep over time. The plastic resin glue doesn't creep over time so I expect that the original springback will also be the future springback if you use Plastic Resin. Therefore that is what I use when I do veneering, or bentwood laminations where I want to know what the final product is like.
 
Mike,
That is an interesting formula but it does not account for radius of bend or especially the relationship between amount of deflection and chord length.

Can you elaborate?

Thanks (from an old metal deformer),
Frank
 
This is the formula I got from someone at the 'creek a while back, used it once and it was almost dead on !!

Rfinal(n-1)/n = Rform

Example: to get a 5" radius, 10 ply lamination

5"(10-1)/10 = 45/10 = 4.5"
 
Hi Mike,

You know, its funny, but I never thought of it that way, now I'm kind of kicking myself! Of course the thicker lamination will be stiffer, just like a thick board (or head in my case)! Now I want to go and experiment with different glues on the same thickness pieces. Maybe its time to build a couple demi-lunes.

Just gotta finish the house first.

Probly the guest house too.

Oh well, one day.

John
 
This is the formula I got from someone at the 'creek a while back, used it once and it was almost dead on !!

Rfinal(n-1)/n = Rform

Example: to get a 5" radius, 10 ply lamination

5"(10-1)/10 = 45/10 = 4.5"

I know very little about this subject, so it's very helpful to be able to ask questions of those who have practical experience with it.
If you were going to make a piece with 2 identical laminated parts, does it make sense to make 1 wider piece and cut it down the center yielding the 2 pieces, or just make each piece separately? An example might be back splats for a chair? One negative may be that it is more difficult to bend a wider board than a narrow one. Maybe for woods and pieces of the same wood with a fairly uniform grain pattern, the characteristics causing spring-back are the same making them behave in the same way. Then would it be more a case of which would be the more efficient way.. 1 piece and cut, versus multiple narrower pieces to form, glue-up etc?
I already learned my lesson about air dried wood vs kiln dried when making some larger shaker boxes. Much harder to uniformly bend the wood, the wider that piece is.
 
Actually Bill when I attended the workshop at Sam's shop and he showed us how he does his rocker laminations I seem to recal he used Tightbond 3.:wave:


Interesting :huh:
I was on another forum discussion on this manner and also expressed Titebond as my prefference and denounced White glue and was chastized by a self proclaimed rocking chair "expert" claiming Sam Maloff "Always uses White for his laminations"

Goes to show you that this information highway is full of misdirections, guess I'll do some researching :type:
 
I guess I'll go out on a limb and suggest something else here. I work in a wood crafts shop on nearby Luke Air Force Base. We make lots of flag boxes, shadow boxs, etc. One of the shadow boxes we make is shaped like a master-sergeants' rank insignia, which is curved on the bottom. I make this part by laminating 8 to 10 strips. Iv'e tried all the glues. Yellow glue-not enough open time, tightbond III is better but still have to rush, and it creeps. Plastic resin glue worked well but is very temprature sensitive, (I believe it needs to be above 70 degrees) and basically takes overnignt to set up. So I tried poly glue; Gorilla glue, Elmers Ultimate, etc. I didn't have much experience with it and heard lot of people don't like it (mostly because its messy). But it has worked great for me and I don't find it all that messy once you get the hang of it. It has plenty of open time, cures in 3 or 4 hours and makes the bent-lam plenty rigid, and no glue creep. I've never heard anyone metion using poly glue for bent-lam and am kind of curious why. I've made dozens of shadow boxes with poly glue-lam with never a failure in the lamination. I also use it for my end grain cutting boards, prolly at least 100 with never a failure. Not to steal the thread, but I'm very interested in hearing other opinions on this. Barry
 
Barry, I've never tried Gorilla Glue because, what I've heard, is that it expands while curing, thus opening the joints.

Again, this is what I've been told by others and read in books (mags)...... so I never tried it.
 
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