Re-glueing wooden mast

[PAR]

Yokebutt, the glue I use and most folks I know is, Weldwood Plastic Resin, by DAP. Technically it's a pre-catalyzed, water activated, urea-formaldehyde and barium chloride mixture, which meets government MMM-A-188C, type II adhesive spec.

Temperature effects the pot life and clamping pressure time, boiling down to, warmer temperatures decreasing the pot life and clamping times.

It doesn't penetrate like epoxy does, so the vast majority of it can be scraped or sanded away in preparation of a new gluing surface which will be just as strong as it was. This isn't the case with epoxy coated surfaces, unless you sand below the penetration of the glue (which can remove a lot of wood)

Masts and spars in general, last quite a while because they have rather limited exposure to moisture. They see very limited soaking and a reasonable coat of paint/varnish can keep them stable. As Cyclops points out, they fail from breaches in the coatings used (paint/varnish) or joint racking caused by the continuous loading and unloading they see in use. Eventually the wood fibers crush along the joint lines or internal stresses in the lumber work their way to the surface, when moisture can find a way in, to further along the break down of the structure, on a cellular or mechanical level.

For a bullet proof job I use resorcinol because it's water proof (the same glue used in plywood panels) but it does have an offensive glue line to some folks and requires well fitting joints. Plastic resin also requires well fitting joints, but the brown glue line is hidden easily in the grain. I do use epoxy on birds mouth spars if requested. Epoxy doesn't require well fitted joints (in fact they shouldn't be) and doesn't need very mush clamping pressure (just enough to hold the parts in contact and alignment) Because of these two features in epoxy use, the glue lines end up being quite a bit larger and can really stand out on a brightly finished mast. These reasons plus the mess, cost and weight of the goo, leads me away from epoxy, much more often than not.

By their nature, spars should have good, tight joints. We usually rely on the properties of the wood to provide the temper of the stick. The stave widths and thickness are selected by the designer to give an element of mast bend under specific loads. Epoxy as an adhesive and particularly when encapsulation is done, changes these properties. I have no problem making something better then it was, but do have issues with arbitrarily changing the dynamics in a design for no good reason.

[Aurora]

Hello Par, Is there a mail order supply that I can buy some of the resorcinol from?

[PAR]

West Marine and BoatUS carry it, though not always in stock. Most every marine supply outfit will be able to get it also. Resorcinol requires very well fitted joints because it doesn't fill gaps and also needs plenty of clamping pressure to insure a good bond. If you setup carefully, you'll have good results. This glue typically is used on painted masts because of the purple glue line. Plastic resin (available at Ace Hardware and other stores) is the glue found most in spar construction and likely what you have as well. It's cheaper, easier to work with (resorcinol is a two part adhesive) and has a pleasant colored glue line, so varnishing isn't an issue. Both glues will bond stronger then the wood's strength.

[Aurora]

The plan is to keep the mast varnished so it looks like I have to decide between epoxy and the plastic resin. I really don't want a blue line down the mast. What is the working time of the plastic resin?
Thanks,
Paul