Closing the box is a thrilling milestone in the instrument making process, but care needs to be taken to make sure that this complex joint is completed without introducing any stress which could creep up as cracks in the future.
As with any important glue joint (are there unimportant glue joints?) you want to do a trial run, the first step being to check and see that all the parts mate cleanly without having to press or bend them together. It’s tricky gluing down a top or back because of the curved geometry. The outline of the instrument is curved and, on most guitars, you are gluing an arched plate down. The kerfing, which provides the primary gluing surface, needs to have been arched to the same degree as the plate being glued to it. The brace ends need to seat snuggly into the pockets you have chiseled away to accept them.
With standard wood glues, and this includes our FGX instrument maker’s glue, you have a fair amount of ‘open time’ to set your clamps. With hide glue, it’s a real race. Even many ‘hide glue die-hards’ do not use it for these joints, saving hide glue for the top seam, bridge glue-down, and brace assembly. It goes without saying that it takes a lot of clamps to cover the perimeter of the guitar. Spool clamps are an option, but Klemmsia Clamps, used with cauls especially, are a good, strong, quick option. In addition, these clamps have many, many other uses in the shop.
In the Spanish method of classical guitar construction, ropes are used to hold down the top or back. This technique can easily be employed on just about any other type of stringed instrument. Once you have practiced and perfected the pattern of ‘weaving’ the rope around the box, it can go quickly and apply good, even pressure around the perimeter. A better, more modern approach, is to use LMI’s Rubber Binding Strap. It grabs the wood better than rope, does not slip and it’s wider than rope.