I'm gluing braces today. Go-bars are one of the idio-syncratic tools developed by luthiers to facilitate clamping with minimum headache. Given that the soundboard is so thin, the spans long, and the assembly awkward, the go-bar deck is an elegant solution.
My go-bars are salvaged strips of glass-fibre reinforcing. They appeared one day at Lee Valley Tools for sale on the "scratch and dent" table and I grabbed a bunch at $.75 a piece. They're not a regularly stocked item. Here I'll be gluing the treble bars. You can see that I've already got the bass or "J" bar in place.
I dab on the glue and press a bar into position, flexing it between my purpose-built table and the bulkhead above. The bars provide firm, even pressure. Another nice feature of this system is that the intersecting corners remain free and clear for me to get a chisel in there to remove squeeze-out.
Luthiery buffs who specialize in guitars might note that the grain in these braces runs parallel with the soundboard, contravening modern wisdom. This is historically accurate. Surprisingly, there is little difference in stiffness over a given span between this orientation and that of vertical grain assuming bars of similar dimensions.
I suppose the early lute makers would have used weighted blocks spanning several braces, or perhaps they simply relied on a "rub joint", where the bars are pressed into place with a little sliding motion and held until the hot glue seizes and begins to gel.
I like the way the deck looks when the bars are set up. It's a neat piece of sculpture.
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