Portland Guitar Co.

( 116 ) 17-Feb-2013

Now I turn my attention to making the braces. Here I am laying out my set of templates.

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I use a sanding guide to shape the bottom of the braces. The braces need to fit the shape of the sanding bowls that have te shape of the top and back..

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Here I have mounted a brace blank on to the sanding guide.

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I lay out the brace blanks on the sanding bowl. The green bowl is for the back, and the blue bowl is for the top.

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I trace the outline of the rim onto the back plate so I can cut the brace blanks to their proper lengths.

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I mark the layout of the braces.

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I do the same thing for the top plate.

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Now back to the braces. To reduce the mass of the braces while maintaining their stiffness I make my braces into something similar to aircraft struts. Ultimately the braces will have an I-beam cross section with circles cut out of the webbing. Here I am drilling out the holes.

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Lots of holes.

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Next I use my router table to route out the I-beam channel.

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For the main X-braces I use my bandsaw to trim the brace blanks.

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And my oscillating sander makes the height consistent.

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The X-braces get a notch cut out using the bandsaw.

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A good fit, snug but not overly tight.

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Now I start to shape the X-braces using my belt sander.

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The two legs of the X-brace are asymmetric. The bass leg of the brace is trimmed so that it will be less stiff than the treble arm of the brace. This asymmetry will broaden the frequency response function of the guitar helping to create a more even set of tones across the fretboard.

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The treble leg is stiffer than the bass leg.

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I use the bandsaw to rough out the tops of the braces.

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And my disk sander finishes up the job.

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Here we I have laid out the braces on the top to make sure they fit.

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Working on shaping the finger braces.

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I use my oscillating sander with a small cylinder to create the I-beam profile.

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The end of the A-frame portion of the top braces get profiled so they fit together.

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And back to the disk sander for more shaping.

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Here I have laid out the back braces, one more time.

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I use my drum sander to reduce the thickness of the back plate. Cocobolo is a very heavy wood and I don't want it any thicker than necessary.

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Very nearly 100 mils thick. When the guitar is finished the back will end up being about 90 mil thick.

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The drum sander leaves sanding marks, so I use a palm sander to remove them.

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One more time marking out the rim profile. The washer gives me 1/4 inch extra. This will be trimmed off after it is glued to the rim.

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And laying out the the braces once again to check their fit. It was a beautiful spring day when I was working on this and you can see the sun shining in my open garage door. Hey, we get 300 days of sunshine in Portland, beleive me, I wouldn't fib to you now would I.

( 151 ) 17-Feb-2013

Now with the braces shaped I spend time sanding them smooth... Wayne Henderson will tell you that this helps the notes get out of the guitar better... who am I to argue with Wayne Henderson.

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A bit of hand work with a piece of sandpaper.

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When I am finished we end up with little bits of beautifully sculpted spruce. Following are a few art shots of the back braces.

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Description

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Now I am ready to rough out the back plate with my bandsaw.

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Cocobolo is a very oily wood. To ensure we get a good glue joint the oils near the surface need to be prepared. Alcohol is used to wipe down the surface causing the oils to crystallize. This will allow the glue to penetrate the surface and form a good bond.

( 163 ) 17-Feb-2013

I like to apply a stoichiometric amount of glue to the bottom of the braces... not too little, not too much.

( 164 ) 17-Feb-2013

To glue the braces in place I use a go-box and go-sticks. The back plate is centered in the sanding bowl that has the shape of the back I am after. In this case the bowl has a 16 foot radius of curvature. The go-sticks press the braces into the back and the back into the bowl.

( 165 ) 17-Feb-2013

Lots of go-sticks. The sticks with the black tips are stiffer than the sticks with the red tips. The tips are made of rubber so I don't crush the braces.

( 166 ) 17-Feb-2013

After the glue cures over night. I won't remove the cutaway section until I am ready to glue the back onto the rims.