Side Bracing

[Alan Carruth]

'Cloth vs Wood' side reinforcements is another long-running disCUSSion. I'll try to summarize:

The 'cloth' camp says that the reinforcement is there primarily to stop cracks. In this I've found that cotton-poly bias tape, glued with hide glue, is pretty effective, as it approximately doubles the force it takes to crack a side. Nylon tape does not glue well (I have not tried polyester), and HHG is stronger, and easier to use than Titebond. Note that the big drawback with cloth tape is that air can get at the glue, and break it down over time. I shellac my tapes after the liners are in to help preserve the glue: we'll find out in 75 years or so whether it worked.

'Wood' fans point out that the side fillets add stiffness and strength, which they certainly do. You _must_ inlet them somehow: if they end at the liner that's where you'll get cracks, just where they're hardest to fix. Wood fillets also are stronger than tape, and might be a help if the guitar is expected to lead a particularly hard life.

A cross grain wood fillet expands and contracts less than the wood in the side, and could cause a crack by not shrinking when the side does. I used to think this was merely a theoretical issue, but saw a couple of Matons a few years back with just such cracks running across the fillets. They use a pretty soft side wood in those, and they're deep bodies, so it's the worst case, but still...

A shaving might work pretty well, but then, of course, it's more like a 'tape' than a 'fillet'. When I want a shaving for something like a spiral bushing on a fiddle I find it works well to plane off the edge of a board to get it smooth, and then wet it before taking off the shaving you're going to use. That keeps the cap iron from breaking the grain (which is what causes the shavings to spiral), and makes a nice ribbon that you can work with. You can usually get a pretty heavy shaving off when it's wet, too. You could have a lot of fun with this, using fancy contrasting wood for side reinforcements. I'd stay away from curly wood, though: too much weak short grain.

Alan Carruth / Luthier

[Pat Foster]

Here's a pic of my re-kerfed kerfing, done after gluing on the kerfing with the linings attached to the kerfings, of course.

sidebraces.jpg (18.07 KiB) Viewed 3434 times

Pat

[Michael Lewis]

Such narrow strips offer less reinforcement than wider ones. To stop cracks from running you depend on the shear strength provided by the strips, and the wider they are the more shear strength they will have. There are a lot of guitars that don't have any side reinforcement.

Years ago I started using side reinforcements to flatten the rippled sides, then I learned to bend the wood so there are no ripples.