Glue - A bit about the Sticky Stuff
With the glue being a very important part of a mast or spar, we are
asked on a regular basis 'what sort of glue do we use?'. So in an
attempt to provide an answer an put some common myths to bed, this is
where we stand:
There are many glues around all with place in the market and using the best glue for the application is really the key. Think as though you would not try and stick a broken plate together with Pritt-stick; but it is very good when used on paper. The same goes for a small wooden dinghy mast, such as an Enterprise, that may only have 12mm walls as a gluing surface, bending and flexing all over the place, dunked in the water every so often, and used as the cover ridge pole throughout the winter; and not forgetting it needs to withstand at least 30 years of this type of abuse.
The answer in this case is the Urea-formaldehyde Aerolite 300 adhesive; and before anyone starts to point out the shortcomings with this glue, please remember it was developed to stick the Sitka Spruce parts in planes together, and a good glue joint is said to be 3 times stronger than the spruce itself. There is no pre-mixing, the glue is spread from the pot onto one surface, the acid hardener is spread onto the opposite surface, and the two are then simply pressed together. Great commercially as there is zero waste, and also with it being clear, the glue lines are completely invisible in most cases.
While Aerolite is good on the small Sitka mast, it does not perform as well when it comes to Columbian Pine spars, so we switch to a resorcinol phenol formaldehyde resin. The 'traditional red boatbuilders glue' as it is sometimes referred to, but a true structural adhesive, and if some basic application 'rules' are followed, it's a hard one to beat. We use resorcinol for all Sitka spars over approximately 30', nearly all Pine spar produced, and with its ability to flex and move with the wood, combined with excellent UV stability; it is definitely a firm favourite.
Although you will find a small pot of Epoxy in our glue cupboard it is not something we use when it comes to gluing up masts. Some people will, but for us there are too many reasons why it does not match the properties of resorcinol - in our given application. Single part Polyurethanes likewise have been a great breakthrough when it comes to joinery work, but once again when you're dealing with a glue-lam construction one has to tread with caution. Similarly melamine glues are on par with resorcinol, but unfortunately out of reach when it comes to cost and availability. The glue market is constantly changing with what were at one time Aerospace glues now readily available in your local hardware shop, but the one thing we do have a tendency to do is stick with what we know and trust, as all our products rely upon it.