Flexible and Strong Wood Glue

Stuart Ablett

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Tokyo Japan
I'm in the process of bidding another chair-like prop for my favorite Canadian Circus (please don't say their name, just trying to keep a low profile).


This will be a chair or two (I'm trying to get them to buy two for a good price, as we all know with chairs making two is NOT double the price as you already have all the jigs and such built) that is used in a highwire act......


highwire_chair.png



Twice daily the chair gets dropped from a height onto the wirenet then when the act is over the wirenet gets released the the chair hits the stage from about 6 feet up, it comes down a different way each time and over time the chair gets busted up.


The chair is reinforced in key areas with steel, which I'll have to make as well, and the weight is to be between 6-7Kg 13-15lbs about. I've already identified some things that can be improved upon the existing design, that will make it a lot stronger and will not add any weight.


OK what I'm putting out there for everyone is what kind of glue should I use?


A typical PVA white glue would work, I'm sure, but what about something that is good and solid but has some flex to it?


A gorilla glue or an epoxy?


I'm open to all ideas here, this is a high end build that has to be better than good, and it has to be durable too.


The wood used will be Beech, I think it is a good choice for strength and durability, it is often used in chair construction and is not bad to work with. It is expensive here in Tokyo, but hey, so is everything else. I'm planning on using typical mortise and tenon joints and I think I'll pin these joints to make them extra strong. I have a time frame that the chairs would have to ship before the middle of June, so I do have some time, but as you know I'm really busy with other stuff too, so I need to get in front of this, so I'm looking for ideas.


I cannot share the plans with you for obvious reasons, but it is a basic chair, the base is a bit wider side to side and back to front than the seat, but not much, the legs have about a 3 degree splay. The chair back is straight up and down, not like a real chair, it is a prop.


Your thoughts on all of this would be appreciated, I have a pretty good idea about how I'm going to prototype it and then build it, but I would be a fool if I did not ask for more input.


Thanks!
 
Can't help with the glue very much but I would think that epoxy would be strong but brittle.

I just built my grand daughters vanity from beech. $1.80/bf. I'd never used it before and I found it easy to work but not as strong as oak or ash. Also, while jointing I noticed occasional sticky spots on the wood. I don't know if they were pitch pockets or something else ??? The sap wood is super soft.
 
If using epoxy, the 5 minute version is more brittle than the 18 hr or 24 hr cure type. Golf club makers generally the latter as it is strong, yet resilient enough to withstand impact, plus it allows for more working time. Although this one (http://www.golfsmith.com/product/30089618/clubmaker-shafting-epoxy-1-2-pint-black-fe#) cures black, as is most common for golf clubs, you can get this type of epoxy in the clear version if you prefer.
 
Well I would think using the same kind of glue that is used to do strip canoes would be a good starting point and if i recall that is system west epoxy. Reason i am thinking this way is the flex a canoe has to withstand and not crack. May be worth thinking about ripping off some of the canoe logic given when the strips are covered the way its done it ends up looking like wood but has a coat of glass beneath that smooth layer and its clear as daylight. Other thing i can think of that would add strength is laminating as in making up laminated beams or boards. But hey there has to be a limit to the cost so making ones own lumber can only go so far. Just on the risk management side i take it you have considered the insurance aspect of being covered from any potential liability in this case.
 
Well I would think using the same kind of glue that is used to do strip canoes would be a good starting point and if i recall that is system west epoxy. Reason i am thinking this way is the flex a canoe has to withstand and not crack. May be worth thinking about ripping off some of the canoe logic given when the strips are covered the way its done it ends up looking like wood but has a coat of glass beneath that smooth layer and its clear as daylight. Other thing i can think of that would add strength is laminating as in making up laminated beams or boards. But hey there has to be a limit to the cost so making ones own lumber can only go so far. Just on the risk management side i take it you have considered the insurance aspect of being covered from any potential liability in this case.

Epoxy is certainly on the table, but I need to find out more about it.

Liability is an issue that is addressed and covered. :)
 
I would specifically exclude polyurethane glue, of which Gorilla glue is a major brand. It does stick to slick surfaces (like something that was previously finished) and does expand to fill gaps, like sticking to a very rough surface like stone, but as it expands, it becomes foam-like, and that foam is VERY weak. I do use it occasionally, but never for joints that I can control. The only joint that I ever had fail (other than when I said "I wonder if I can just glue this to fix it") was with Gorilla glue - luckily I caught the mirror as the frame came apart.

White PVA glue is reversible and flexible, but is not as strong as yellow glue. Both have enough creep that different species, with slightly different expansion characteristics, can be glued together. I use Elmer's carpenter's glue or Original Titebond - both are reversible with effort, and fill small gaps (the almost perfect joint). They have excellent adhesion to porous surfaces (unfinished wood). They have high initial tack (after the first few seconds, the joint is hard to slide). Titebond 2 and 3 are not reversible.

I am a big fan of plastic resin glue - also called urea formaldehyde. (The amount of formaldehyde in a typical batch is smaller than the amount your body exhales daily). I buy powder that is mixed with water 20 minutes before use. It has a long open time, and no creep. A no-brain choice for veneer, excellent for bent-wood lamination (no creep is no spring-back), and also usable for work requiring a long open time. It has low initial tack, which may be good or bad, and cures in 8-12 hours.

I occasionally use epoxy, but am not as expert as others on this forum.
 
I'll contact West Systems and see what they say, but for now, I think that the Titebond III is leading the pack, the other stuff that Charlie is recommending, the "plastic resin glue" sounds interesting as well, but I don't know if I can source it here or not. Charlie, do you have a brand name?

Cheers!
 
I'll contact West Systems and see what they say, but for now, I think that the Titebond III is leading the pack, the other stuff that Charlie is recommending, the "plastic resin glue" sounds interesting as well, but I don't know if I can source it here or not. Charlie, do you have a brand name?

Cheers!

Maybe look under "resorcinol", "resorcinol glue", and "resorcinol glue vs epoxy".
 
I don't believe you will find anything stronger than yellow PVA glue on the wood to wood joint. The joint when glued with yellow PVA -titebond II - is #1, stronger than the surrounding wood. #2 - stronger than gorilla glue or any other glue. The closest contender was hide glue. That was all in an article I read in one the woodworking magazine.

I was making a sign and I needed to bond - dissimilar materials together. I had PVC, HDU (signfoam), and painted aluminum. I asked the sign makers forum guys what they use, and if there was any testing done. They were not aware of testing but many recommended "LORD" epoxy. I got it from www.mcmaster.com . It is not brittle like those spoken about here.

I bonded the dissimilar materials mentioned above and let the epoxy set a couple of days. By hand I could not break any of the bonds. I was able to break the aluminum to HDU - but it was the HDU that separated. HDU is by itself not all that strong. The remaining joints needed to be pried apart and none were easy. In ever case except one the epoxy did not fail, rather the material failed. The one joint where the epoxy failed was painted aluminum to painted aluminum. It was pried apart but with significant effort.

I FORCED every joint into a failure. Under anything normal, I would trust the painted aluminum to painted aluminum as a bonded joint with LORD epoxy.

I do not have any idea what would bond steel to wood, but I would do some testing with LORD epoxy.

Under the conditions that you are talking about, there needs to be expectations of built in failure.

What about not wood at all - what about a welded aluminum chair? Sorry - that is not wood. You could get it made and sell it to them. Or what about a welded aluminum frame - covered with wood.
 
Stu, I've used DAP Weldwood Plastic Resin Glue:

http://www.amazon.com/00203-Weldwoo...0&sr=8-1&keywords=weldwood+plastic+resin+glue

Like Charlie said, it has no creep, which may or may not be a good thing with this particular project. I've used it primarily on higher-end cutting boards like the quilt pattern boards I did a few years back.

I have seen the DAP. Someone gave me what was left in an unlabeled 25 pound bucket, no instructions, so I got the DAP instructions, used the glue up, and liked it.

Then I bought a 25 pound bucket of this: http://www.veneersupplies.com/products/Ultra-CAT-PPR-Veneer-Glue.html (for about $80, a lot less per pound than DAP from Amazon.) It looks and acts like the DAP.

Why did I buy so much? This is stupid logic, so you can skip my rambling. I figured that I needed more than a 5 pound pail for a large table veneering job. 5 pounds was $25, and since I wasn't sure how much more than 5 pounds, I am in for $50 for two buckets. But for $80 I can get 25 pounds, AKA lifetime supply. You can guess what I did.
 
Welded Aluminum WILL crack guaranteed that is why you see aluminum stock trailers and truck trailers in the repair shop all the time they just wont hold up to shock. Thats also why you dont see welded up alum Aircraft except Eclipse it is fusion stick welded which is really cool to watch
 
My first thougth: NOT CA
There are many kinds of epoxy glues. The ones used on fiberglass boats comes to mind. They take a lot of pounding and flexing.
Second thought: Does the chair have to be made of wood? How about a white durable plastic. Delrin, with proper sealant would last and last. Of course, that way you would not get repeat orders. :rolleyes: Delrin would flex without weakening or breaking.
 
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