Delaminating glue joint outside
I have a problem with some glue-ups.
Situation: The deck is Angelium Pedra a Brazilian Mahogany look alike. It is very oily but machines well, and the cutting edge of the tools to not degrade quickly. One web site: http://www.eceurope.com/showrooms/details.htm?itemID=676&session
The customer wanted handrails 2″ thick and machined, and the spindles are also glued together and then cut. We used 5/4 x6 boards and epoxied them together horizontally during the summer. They have 2 or more coats of Penofin on them (not on the epoxied surfaces).
The glue we have used is West Systems 51 epoxy.
It makes no difference if we flattened, acetoned and then epoxied the boards, or just slapped them together – the glue line is de-laminating in many boards.
The epoxy rep suggested that no matter what we do, the boards are going to delaminate outside because of wood movement, and suggested that I unscrew all the handrails and but in dowels, biscuits or screws (hidden under the rail) then re-attach them.
Does any one have any other solutions? What about the spindles? Should I herringbone 4-6 finishing nails in each one to stop the delamming?
Quality repairs for your home.
Aaron the Handyman
Vancouver, Canada
Replies
I had a problem with gluing up some fake mahagony a few years back. Some chemical reaction turned Titebond 2 into soft goo after about 16 hours and the bent lamination cleared my work bench of tools when it let go.
I told the GC that I would re-do it with honduras or he could find someone else. I no longer mess with the exotic stuff at all. Who knows what poisons lurk within?
Clampman
"The epoxy rep suggested that no matter what we do, the boards are going to delaminate outside because of wood movement,"
I don't buy that.
If I understand you correctly you are just taking thinner material (1 bys?) and gluing them up to get some fatter stock.
All of the grain is going in the same direction, right.
It does not matter if it expands 1/10% or 10%. It is all going to move the same amount.
Almost. If the grain were in exactly the same perfect orientation you'd have that situation. I'll bet that the wood wants to cup or twist also. But, the epoxy should be good for 1000 or better PSI strength on that glueline. It should actually be stronger than the wood. If it's delaminating either you're getting more force than that (I'd guess no) or the epoxy is not holding as well as it should. Take a look at the glue line. If you can see half the fibers torn out of the wood, then I might consider the rep's opinion. If you can see that the wood is nice and smooth, then the epoxy has let go and it may be his problem. Virtually every glue is stronger than the wood. If you don't see fibers torn out you have a glue problem or a surface prep problem.
Aaron,
How dense is this wood? If comparable to true mahogany, I'll bet the oil is the problem. If it is much denser than Honduras mahogany, then the West System epoxy is unsuitable (from their own literature), and resorcinol is what I would use. The other poster's points about movement and glue degrade are well to consider also. Maybe the wood machines so well because the tools are swimming in oily plant juice, keeping the edges cool and lubricated? Nails probably will be of little use in keeping it together if the glue joint is feeble. Good luck solving this one.
Bugle