Outdoor capable laminations

[Brian Holcombe]

Afternoon gents. I'm building a chair which will spend its life outdoors, but will be sheltered from the rain and snow and actually the majority of the sun.

For the back, I'd like to do a bentwood lamination, rather then attempt to steam bend the mahogany that I will be using. In doing so I need a glue that will not creep and will be capable of surviving in mildly harsh outdoor conditions.

Thanks in advance.

Cheers
Brian

[Mike Henderson]

Titebond III will work for you. Sam Maloof used titebond on all his rockers, and he laminated the skate.

I've done a fair amount of laminate bending with Titebond and no problems with creep or anything else.

Otherwise, use a UF glue or epoxy.

Mike

[James Waldron]

Afternoon gents. I'm building a chair which will spend its life outdoors, but will be sheltered from the rain and snow and actually the majority of the sun.

For the back, I'd like to do a bentwood lamination, rather then attempt to steam bend the mahogany that I will be using. In doing so I need a glue that will not creep and will be capable of surviving in mildly harsh outdoor conditions.

Thanks in advance.

Cheers
Brian

For outdoors (and in my case, on boats), it's hard to outperform a two part epoxy. For convenient sourcing and convenient guidance and convenient usage, I'd suggest West System, http://www.westsystem.com/ss/ ; System 3, https://www.systemthree.com/ ;or if you don't mind a messy web site (but with a good price point), you can go to Progressive Epoxies, http://www.king-cart.com/cgi-bin/cart.cgi?store=epoxy . The West site has really good tech information and the tech service people there are quite helpful by phone or e-mail if needed.

The one area to be careful about is the need to protect exposed epoxy (i.e., coatings, not glue lines) from uv exposure (sunlight in particular), as it will yellow over time (in the tropics, over a frustratingly short time). A good marine varnish over the surface will do, but as with any outdoor varnish finish, the varnish will need refreshing from time to time.

For laminating wood, it's good to add a reinforcing filler (cotton flock or milled glass fibers) to the mix. If you laminate with oily tropicals (teak, etc.) or with acidic wood (white oak, etc.), wash the bond surfaces with acetone and allow the residual acetone to evaporate before applying adhesive mix.

For the record, Titebond I, II and III will creep over time under stress, as in a bent wood laminate. Read the label.

[Dave Anderson NH]

Another option which stands up well in marine use is resourcinol but it is becoming harder to find.

[Mike Henderson]

For the record, Titebond I, II and III will creep over time under stress, as in a bent wood laminate. Read the label.

I've heard that story many times but I've used Titebond for laminate bending in many different applications and never experienced any creep in the laminates. And as I mentioned earlier, Sam Maloof used Titebond for the laminate bends in his rockers and I've never heard any stories of creep in his furniture.

I asked Sam directly what glue he used and he pointed to a shelf where he had Titebond glue. He said, "I use one or the other depending on the color of the wood" referring to Titebond I or III.

Mike

[Brian Holcombe]

Thanks gents, appreciate the information. On a separate topic, should I be at all concerned with spindles being cut into a bent lamination?

[James Waldron]

Used indoors, with controlled temperature and humidity, stressed Titebond PVA glue laminate joint creep may not show up for decades. Outdoors, exposed to high temperature and high humidity, things are quite different and bentwood laminate failures can occur in a matter of a few months. That's why the labels warn about creep and explicitly disclaim use of Titebond PVA as a structural adhesive. Again, read the label.

Or live dangerously. You pays your money, you takes your chances.

[Eric Schmid]

For exterior furniture I'd use epoxy. Polyurethane glues also work well, but I don't like combating the expansion in a bent lamination. If you have several pieces to glue at the same time, a slow epoxy provides plenty of time to get the surfaces coated and clamped.

I got scared off from TB 3 when some post wraps came undone on me a few years back. It probably was not all the glue's fault, but we did a few with Polyurethane on the same job and none of those failed.

Keep in mind that much of my work lives fully exposed to the elements, so I tend to stay on the safe side. That's not to say TBIII would not be suitable for your chair, it might hold just fine. For me, the extra effort and mess of Epoxy and Polyurethane glues are offset by the peace of mind (assuming proper technique).

[Curt Putnam]

@ 150°F, TB III is weaker than the wood - confirmed by Franklin. I would use epoxy or a UF glue like Unibond 800.

[Derek Cohen]

West Systems epoxy. I used this to repair my surfboards and windsurfers for many years, plus it was the choice of custom builders. Today I use it in situations where woodwork is exposed to rain and sun. Excellent track record.

Use packaging tape over the formwork, and then wax it for release.

Regards from Perth

Derek

[Mel Fulks]

One glue company rep told me they can't say glues are structurally safe without paying for expensive Independant tests. If they don't think that is a market they get a big piece of they decline to pay for the testing even if they think the product would be approved. So I make my own judgements based on what info is available and type of job.

[Mel Fulks]

I agree with Mike that creep is not a big deal now. When white glue was big,it was. A perfectly surfaced mortise and tenon joint could need some more work the next day, and I remember pieces sent to finishing room would be sent back for fix.

[Pat Barry]

@ 150°F, TB III is weaker than the wood - confirmed by Franklin. I would use epoxy or a UF glue like Unibond 800.
The glass transition temperature of the west systems epoxy is less than 150F. Onset temperature for glass transition is about 125F. The epoxy loses significant stiffness / strength at increasing temperatures above this. For example, sitting baking in the sun. Better epoxies (industrial) are heat cured and have significantly higher Tgs. Now I can't say how west systems epoxies will perform in your application, just that epoxy is not the perfect answer. Epoxies are also notoriously hygroscopic (water absorbing) - this can lead to adhesion issues / delamination. Forgot to mention the more obvious issues of measuring the two parts, mixing, pot life, cleanup, bond line thickness. Again, epoxy not a perfect solution. If it were me I'd go with the TB3.

[keith wootton]

don't worry about the strength of your bent laminations. they will be at least as strong and resist bending as well as single piece of wood that is steam bent. and it will never lose any of it's bend over time in any weather. and much stronger than a piece sawn to shape.

i have had good luck with gorilla (polyurethane) glue. simple to use, plenty of open time, sets fast, and i think forgiving. any excess will ooze out and be easy to remove (use duct tape on cauls and straps), you can use lots of pressure, and you will get very little springback.

you will also be able to shape your pieces after laminating easier than if you you use epoxy that hardens any wood it soaks into....that said, west epoxy would be my second choice, but you have to be careful not to starve the joints.

good luck!

[Sam Murdoch]

Thanks gents, appreciate the information. On a separate topic, should I be at all concerned with spindles being cut into a bent lamination?

Not any more than with solid wood of the same dimensions. The laminations will actually be less compromised by the "interruptions" than the solid wood.

[Brian Holcombe]

Thanks Sam, that confirms my gut feeling. I should have mentioned this from the get-go; I have a vacuum press and so Unibond 800 is an option in addition to other glues that require a vacuum press.

[William Fretwell]

I made a large complicated arch to hold a big solar panel off the back of a boat. I used 4 mahogany slices 3/16 thick glued up on forms with TB3 glue. Considerable clamping force was used on the forms and I expected some spring back but there was none! The initial stress in the laminations must have been very high but wood learns its new shape.
I examined the offcuts very recently from 3 years ago. There is no sign of creep even at a steep curve where it was cut. The curves are very strong. It is a fabulous technique to play with. You can incorporate hardware into the laminations for great strength.

I used TB3 as an economical choice as the total glue up area was considerable, I would not hesitate to use it again.

The whole arch was wrapped in carbon fibre cloth soaked in West epoxy, a messy dirty and most difficult procedure. This was given 3 coats of good marine varnish. It is very strong, flexible, and looks somewhat cool.

[Brian Holcombe]

Thanks William. This thread has been insightful. It's good to know that many processes can lead to a quality result. I'll study up some more before committing but I'm glad to hear of so many successes.

[Michael Feldman]

Sorry for being so late to the conversation, but I did an outdoor table with bentwood laminated legs and used a product called Ultra-CAT PPR Veneer Glue from VeneerSupplies.com. I had excellent results and the table has been outdoors since 2013 in coastal Rhode Island and it still looks great. I used black locust for the wood -- which I found a misery to work with -- but that's another story.

[andy bessette]

For bent wood lamination I would use WEST epoxy as I do on everything I build for yachts, priming first with neat resin/hardener mix, then applying a mix thickened with colloidal silica and microfibers, for the actual glue (to insure 100% void-free contact). If the assemblies are large, complex or time consuming to coat, or if ambient temperatures are high, I would use slow or extra slow hardener, to provide sufficient pot life and assembly time.

Care must be taken to avoid contaminating adjacent surfaces and to cleanup prior to cure, as the cured epoxy is very difficult to remove, and can stain the surface slightly. I clean dry, first, then with acetone. After curing, scraping or sanding can remove excess. On oily wood, like teak, I pre-wash the glue surfaces using acetone. Never thin epoxy or incorporate any additives not specifically recommended by the formulator.

[Brian Holcombe]

Thanks gents, this is an old post now. I'll probably check in on that chair sometime this spring to see how it's doing and attend to any issues that have cropped up if any.

[Stanley Covington]

Phenol-resorcinal resin is still the standard for exterior structural glulams. The Europeans have approved some other types, but aliphatic resins are not approved for exterior structural use.

PR is very good, easily applied, not especially dangerous or toxic to use, great strength and bond, absolutely waterproof, no measurable creep in the adhesive itself, but it is a dark brown/purple color.

Epoxy is just as good performance-wise, and looks a lot better, but is more time-intensive to mix, sensitive to mixing ratio, not as easy to apply as PR, doesn't play as nicely with gang clamps, and is decidedly more expensive. Probably not an issue for the volume Brian is considering.

Therefore, PR is the standard laminating adhesive for commercially-produced exterior-grade structural glulams.

I would use epoxy.

[andy bessette]

...PR is very good, easily applied, not especially dangerous or toxic to use, great strength and bond, absolutely waterproof, no measurable creep in the adhesive itself, but it is a dark brown/purple color...

...and requires nearly perfectly mating surfaces, as it has no gap-filling capability.

[Stanley Covington]

...and requires nearly perfectly mating surfaces, as it has no gap-filling capability.

"Perfectly mating" is an exaggeration. PR works fine for milled lumber.

PR does have some gap-filling capability, not as much as epoxy, but it is certainly adequate in many countries millions of times a day for milled lumber.

I doubt Brian will need to span 1/4" gaps.

[John C Cox]

I can completely understand the desire to stay away from hot bending mahogany... Of the woods I have bent - it is easily the least predictable and can be massively cantankerous with no good reason or prediction that it will be such.

Oak on the other hand is the opposite in that particular regard... Ridiculously easy to hot bend for such otherwise cranky wood...

So... If you get into this and do decide you like the idea of bent wood over glue for outdoor use - plain straight grained white oak would be my choice.

If not - I agree with the others on seeking out a good Sailboat structural epoxy... West Systems is great..

A caution.... The stuff soaks to china... And it can run up pores and end grain like mad, soak right up into the wood and diasappear... The typical procedure is to soak the glue joint grain ahead of gluing - to make sure it doesn't all soak into the wood and leave a dry/starved joint. The other down side is that because it can soak so deep - it typically darkens woods considerably.. And sometimes even quite a distance from the glue joint... It can also leave dark glue lines like Superglue often does... Especially if you are gluing end grain. I wrecked a guitar top when epoxy soaked into end grain through the rosette channel and wicked 5" up the grain... Sometimes it's OK - sometimes it's not. Test on scrap to make sure....

[andy bessette]

"...requires nearly perfectly mating surfaces..."


"Perfectly mating" is an exaggeration...
I doubt Brian will need to span 1/4" gaps.

You misquoted me...and exaggerated.

[Stanley Covington]

"...requires nearly perfectly mating surfaces..."



You misquoted me...and exaggerated.

Please observe that your post was quoted in its entirety. No misquote.

You did not mention distances, so exaggeration did not occur.

PR can handle 1/8" gaps of limited length, but not 1/4". I believe that epoxy can handle much larger gaps if it is contained in place until it hardens. Is that not the case?