Bent wood lamination

[wtnhighlander]

Greetings and happy holidays to all!

Do any of you have experience using polyurethane glue ( gorilla glue ) in a bent wood lamination? I'm planning a round table that will require bent aprons. Several anecdotes I have read indicate PVA glue does not cure hard enough to prevent tension in the wood from slowly pulling the layers apart. Epoxy has been recommended, but I can obtain the necessary volume of poly glue much easier.

Any thoughts?

[dwacker]

PVA works fine. If your radius is too tight for the pva it's too tight. 

[Grain Guy]

For sure pva. The only time polyurethane glue comes out is for a bent handrail on a staircase or anything when you need lots of working time. I just completed some bent aprons myself.

[Alan Bienlein]

I use Titebond cold press veneer glue as it dries hard unlike yellow glue that remains flexible. Ive done plenty of bent laminations with this glue and have virtually no spring back and can remove them from the forms in less than an hour.

[dwacker]

TB cold press is a very weak non structural glue unibond would be a better choice if you wanted a real hard glue line and strong glue. On the other hand any glue rate for RF curing will give a hard glue line. TB2 is one of them, not as hard as unibond but good enough for most applications. In fact plain old white glue is good enough for most applications. Sam Maloof used plain old TB on his rockers and other laminations.  

[TRBaker]

I've used Titebond III for exterior laminations for years and never had a failure.

[Alan Bienlein]

TB cold press is a very weak non structural glue unibond would be a better choice if you wanted a real hard glue line and strong glue. On the other hand any glue rate for RF curing will give a hard glue line. TB2 is one of them, not as hard as unibond but good enough for most applications. In fact plain old white glue is good enough for most applications. Sam Maloof used plain old TB on his rockers and other laminations.  

Here is a quote direct from Titebond's web site. "Titebond II Premium Wood Glue is not for continuous submersion or for use below the waterline. Not for structural or load bearing applications."http://www.titebond.com/product.aspx?id=2ef3e95d-48d2-43bc-8e1b-217a38930fa2 Click on limitations to read it in its entirety. 

[krtwood]

Here is a quote direct from Titebond's web site. "Titebond II Premium Wood Glue is not for continuous submersion or for use below the waterline. Not for structural or load bearing applications."http://www.titebond.com/product.aspx?id=2ef3e95d-48d2-43bc-8e1b-217a38930fa2 Click on limitations to read it in its entirety. 

 

Don't use the table underwater or drive a truck over it and you should be good to go then

[Bombarde16]

Sounds like our esteemed host is due for another round of BS busting tests.  It worked with the "non-dewaxed shellac under polyurethane" myth...I wonder what the straight scoop is on this.  I too fell into line that yellow woodworking glue can't do cold laminations and ended up using Unibond.  (Excellent product)  Curious to see a side by side of someone doing a controlled round of bends to see how the various glues hold up.

[wtnhighlander]

Not specific to bent laminations, but Mattias Wandell has done several glue joint failure tests. The most recent one I've seen showed a huge amount of strength difference in Gorilla glue with and without a gap between the pieces. In a well-fitted joint, the gorilla glue tested stronger than PVA, but with a slight gap the PVA was much stronger.

One reason I asked about the gorilla glue is because it cures without air, and I had considered using stretch wrap to 'clamp' the laminations around a cylindrical mold. A couple of band clamps should do fine, though.

[dwacker]

Here is a quote direct from Titebond's web site. "Titebond II Premium Wood Glue is not for continuous submersion or for use below the waterline. Not for structural or load bearing applications."http://www.titebond.com/product.aspx?id=2ef3e95d-48d2-43bc-8e1b-217a38930fa2 Click on limitations to read it in its entirety. 

 

Structural was not really the right wording. Tite bond cold press should not be used for any assembly period other than veneer. It is essentially a sustitute for contact cement and has about the same strength. It should not be used to join wood together. Just as you should not use it to assemble a mortise and tenon joint or edge joint boards it should not be used for bent laminations. Any modern pva glue is much stronger.

 

Open ended bent laminations sometimes will benefit from a very rigid glue line, This helps prevent spring back, this is where epoxies, UF and specialty glues like unibond and uric 185 are especially handy. For the most part in general woodworking these are not necessary for thing like table aprons and the like. That being said Tite bond cold press is not adequate and will fail over time. 

[dwacker]

  I too fell into line that yellow woodworking glue can't do cold laminations and ended up using Unibond.  (Excellent product)  

 

Im not sure what people though they used before uni bond. Another hobby woodworker myth gone wild on the internet. No different than all the lumber siesta myths. Some glues have some advantages but they are not necessary to everyone. Unibond came after the days of urac 185 it was great stuff especially if you were working with walnut or you were a bow maker. The reality is you could use hide glue if thats what you wanted to use for general woodworking bent lamination like table aprons.