LumberJocks

glue ups for unclampable projects #3

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Blog entry by Randolph Torres posted 883 days ago 702 reads 0 times favorited 4 comments Add to Favorites Watch

This method is for those who prefer polyurethane glues as I do. If you have a long linier glue joint leave evenly spaced sections of the joint clean (say 1/2 in. every 6” ) in this space place a dab 1 min. epoxy and try to keep the two from mixing when the joint is compressed. Push the joint together and hold for 60+ seconds. The epoxy will hold the joint together until the polyurethane glue cures, Then they will both work together. We are very fortunate today in that we have so many glues to choose from today.

-- another tip from cooperedpatterns



4 comments so far

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SASmith

1489 posts in 1486 days


#1 posted 883 days ago

I have seen a similar process used before. What I saw was a combination of PVA with dabs of cyanoacrylate gel.
Have you ever had the polyurethane glue expand too much without clamps and cause a bad/wide glue joint?

Thanks for sharing.

-- Scott Smith, Southern Illinois

View Randolph Torres's profile

Randolph Torres

295 posts in 2027 days


#2 posted 883 days ago

No, I spend a lot of time in joint preperation checking both front and back, dry fitting. I also try to glue up soon after the cut so the wood does not change shape as it looses moisture. Also we are used to really slopping on the glue, with poly glue spread it real thin but make sure both surfaces are wet with no dry spots. You should have very little to no squeeze out. If you notice the wood soaking up the poly before its spread make sure to add a little more. The trick is lean, easy on the poly. I’ve been meaning to try PVA but never got a chance to experiment with it. ?how do you like the PVA.

-- another tip from cooperedpatterns

View SASmith               's profile

SASmith

1489 posts in 1486 days


#3 posted 882 days ago

My choice in pva is titebond either II or III.
If you check my projects you will see I do mostly glue lamination work, so I buy it by the gallon. I like it because it has some flex to it, but that also leads to creep.

Do you find that polyurethane glue creeps?
Also what is your preferred brand of polyurethane glue?

For others unfamiliar with pva here is the wiki on the subject:
http://en.wikipedia.org/wiki/Polyvinyl_acetate

-- Scott Smith, Southern Illinois

View Randolph Torres's profile

Randolph Torres

295 posts in 2027 days


#4 posted 879 days ago

Thanks much for the defination, I use it all the time but didnot know it by that name, I also use it by the gallon. Like you the coopering I do requires a massive amount of cut and glue time.

?Do you find that polyurethane glue creeps? ?Can you clarify creeping. Do you mean movement prior to set-up, or post set-up movement. I have not noticed any creep using poly after set up, but it can creep before set-up. Because of its long set-up time it can be forced back into position just keep an eye on it and adjust the forces to neutralize movement.
?Also what is your preferred brand of polyurethane glue? Gorilla Glue.
Poly glue has closer modulus 0f elasticity in comparison to wood than PVA. They expand and contract bend and twist and move equally together, where carpenters glue is more brittle than wood. Here is an experiment you can do using an empty bottle of poly glue cut it open with a razor knife and pull out the glue that has dried inside you can slice this dry glue into strips and run tests on it, twist it, pull it apart until it fails, bend it back and forth until it fails, and any other test you can dream up.
I’ve done some outrageous experiments using poly glue, the most extreme one is a 3 1/2 foot tall octagon vessel of 3/4” plywood edge glued with a 15” bottom opening and 36” opening at the top its been holding together for 6 years its been moved and rolled and left in the rain and its still holding together. I still can’t believe it myself.

Because of all the odd shapes of my projects using coopering I rarely ever use clamps and often go into a gluing sesion not knowing how to proceed until I get the pieces together, poly glue has a long set-up and cure time time I need to figure out how I’am going to proceed.

I checked out some of your projects they are seriously cool, I’ve always loved the way one dementional wood projects that have three dementional look to them fooling the eye.

-- another tip from cooperedpatterns

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