Portland Guitar Co.

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Portland Guitar Pretty Good Intonation (PGPG) System

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Finished Build

Large Jumbo 8 String Wedge Cutaway

Serial # LJ8C 2.1.55

Page 3

(105) 21-June-2012

I have joined a booked matched set of Cocobolo veneers and laid out a ring for the rosette.

(106) 21-June-2012

And then laid out the rosette on the top plate.

( 107 ) 21-June-2012

I use a circle cutter on the milling machine to cut out the rosette.

( 108 ) 21-June-2012

The rosette and its jetsam.

( 109 ) 21-June-2012

I use the circle cutter again to route out the channel in the top plate.

( 110 ) 21-June-2012

This circle cutter mounted in a boring mandrel lets me accurately cut the width and depth of the rosette channel.

( 111 ) 21-June-2012

The Cocobolo ring neatly drops into the channel.

( 112 ) 21-June-2012

I have also routed two narrow channels that will hold a set of pinstriping.

( 113 ) 21-June-2012

A bit of glue will secure the rosette.

( 114 ) 21-June-2012

The rough rosette pieces sit proud of the surface.

( 115 ) 21-June-2012

To make sure they are firmly seated I weight them down.

( 116 ) 21-June-2012

I use my drum sander to level everything off.

( 117 ) 21-June-2012

And in the end we have a handsome rosette. Once I am happy with the front of the sound plate I use the drum sander again to dimension it to about 110 mils.

( 118 ) 21-June-2012

I also sand the back plate to about 100 mils thick.

( 119 ) 21-June-2012

A little bit of palm sanding removes the sanding marks.

( 120 ) 21-June-2012

Now I am turning my attention to the braces for the top and back plates. I use a template guide to sand the bottom of each brace.

( 121 ) 21-June-2012

A little bit of hand sanding makes sure the bottom of the braces match the curve of the forms.

( 122 ) 21-June-2012

Here I am checking the fit of the braces.

( 123 ) 21-June-2012

I use the band saw to rough out the shape of the top of the braces.

( 124 ) 21-June-2012

I use my oscillating sander to dimension the height of the main X-braces.

( 125 ) 21-June-2012

Here I am tracing out the interior of the rim onto the back plate.

( 126 ) 21-June-2012

And then I layout the position of each brace onto the backplate.

( 127 ) 21-June-2012

I use set of Forstner bits on the drill press to make holes in the braces.

( 128 ) 21-June-2012

Lots of holes. Since the holes lie on the neutral axis of the braces, they reduce the mass of the braces while maintaining their stiffness.

( 129 ) 21-June-2012

Here I am laying out the position of the braces on the top plate.

( 130 ) 21-June-2012

To further reduce the mass of the braces I use the router table to route out the side channels.

( 131 ) 21-June-2012

I end up with a brace that is shaped like an I-beam with the web cut out. Technically this results in a brace with a high moment of inertia and low mass. Stiff and light.

( 132 ) 21-June-2012

The disk sander is used to shape the top and sides of the braces.

( 133 ) 21-June-2012

I end up with a graceful cool looking brace that has all of the desired properties I am after.

( 134 ) 21-June-2012

Here I have laid out the braces on the back.

( 135 ) 21-June-2012

In this picture I am laying out the Indian rosewood bridge plate.

( 136 ) 21-June-2012

I bevel and shape the the bridge plate on a disk sander.

( 137 ) 21-June-2012

Here I am shaping a finger brace on the disk sander.

( 138 ) 21-June-2012

I use my bandsaw to create the lap joints in the main x-braces.

( 139 ) 21-June-2012

I carefully cut out the channel in each brace.

( 140 ) 21-June-2012

These two channels are matched at their proper angle.

( 141 ) 21-June-2012

When the braces are joined they make a tight and strong joint.

( 142) 21-June-2012

A small detail requires beveling the tail plate to match the kerfing.

( 143 ) 21-June-2012

I use a fiducial button to let me position the top and back plate on the rim.

( 144 ) 21-June-2012

I put a small drop of glue in the end of the button and then position the rim on the plate. After the glue dries the button sticks to the plate. I can now repeatedly place the plates on the rim exactly in position.

( 145 ) 21-June-2012

I need to trim the X-brace so they will butt up against the kerfing. To help position the rim I use a set of guide blocks.

( 146 ) 21-June-2012

And to position the X-braces I use another set of fiducial buttons.

( 147 ) 21-June-2012

Once the rim is precisely positioned I use a sharp blade to score the brace at the kerfing. I then cut off the ends of the braces at the score marks.

( 148 ) 21-June-2012

After laying out the sound hole I cut it out on the bandsaw

( 149 ) 21-June-2012

And in the end the rim snuggly fits up against the braces.

( 150 ) 21-June-2012

Now with all of the braces made I start to glue them in place. I use a go-box to press the braces in place.

( 151 ) 21-June-2012

Lots of go-sticks.

( 152 ) 21-June-2012

Lots and lots of go-sticks. That arc in the top plate of the go-box is not an artifact of the camera lens.

( 153 ) 21-June-2012

The back braces get the same treatment.

( 154 ) 21-June-2012

I make sure that the braces make near perfect contact with the plate. I really want a good joint here.

( 155 ) 21-June-2012

The sound hole gets trimmed up on the oscillating sander.

( 156 ) 21-June-2012

A look at the top plate with the braces in place and the cutaway removed.

( 157 ) 21-June-2012

Another look.

( 158 ) 21-June-2012

The back plate gets a set of fiducial buttons.

( 159 ) 21-June-2012

A look at the back plate after the cutaway is removed.