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A short scale acoustic bass guitar experiment.

#161
Starting with the X-brace. As I mentioned earlier, the shape of the trough is exactly the same as a spline curve with the same length and deflection drawn in CAD. So, as an experiment, I stretched that curve in CAD to the length of a line drawn diagonally through one half of the X-brace, printed it out and stuck the print to a piece of brace wood. I sanded the wood as near as I could to the curve and it fitted almost perfectly onto the trough. So I made two braces like that and notched them.

Body 2 027.JPG


Body 2 028.JPG


To be able to sand them to a perfect fit I made a sanding fixture. I marked out all the brace positions on a piece of MDF and pinned 'stickers' to it .

Body 2 029.JPG


Here it is with the X-brace installed.

Body 2 030.JPG


I pencilled the surfaces of the brace and It only took a few passes on the trough for all the pencil marks to disappear.

Body 2 031.JPG
 
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#162
Dave Higham said:
Starting with the X-brace. As I mentioned earlier, the shape of the trough is exactly the same as a spline curve with the same length and deflection drawn in CAD. So, as an experiment, I stretched that curve in CAD to the length of a line drawn diagonally through one half of the X-brace, printed it out and stuck the print to a piece of brace wood. I sanded the wood as near as I could to the curve and it fitted almost perfectly onto the trough. So I made two braces like that and notched them.

View attachment 7502733

View attachment 7502734

To be able to sand them to a perfect fit I made a sanding fixture. I marked out all the brace positions on a piece of MDF and pinned 'stickers' to it .

View attachment 7502735

Here it is with the X-brace installed.

View attachment 7502736

I pencilled the surfaces of the brace and It only took a few passes on the trough for all the pencil marks to disappear.

View attachment 7502737
Click to expand...
Did you use a hand sander for this final truing, or …?
 
#165
After gluing the X-brace on, I sanded a piece of padauk to 3mm (0.120") thick to make a bridge plate. Took all the 'stickers' off the board and attached the bridge plate to it with double sided tape and sanded it in the trough until all the chalk marks disappeared. It finished up 3mm thick in the middle and 1.6mm thick at each end. As I said before, everything that is glued to a curved surface gets sanded to that curve. Here it is, being glued.

Body 2 032.JPG


The other braces all went through the same process and here they all are.

Body 2 033.JPG


That's the front ready for gluing to the sides but before I do, I've decided to glue the K&K pickup to the bridge plate. Much easier than trying to do it blind after the box is closed. The saddle might not finish up exactly where I think it will be, but it won't be far out

Body 2 034.JPG


I've also made a clamping caul to fit inside the box when it comes to gluing the bridge on. Four magnets on the outside will keep the caul in place while gluing and clamping the bridge.

Body 2 035.JPG
 
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#166
Dave Higham said:
After gluing the X-brace on, I sanded a piece of padauk to 3mm (0.120") thick to make a bridge plate. Took all the 'stickers' off the board and attached the bridge plate to it with double sided tape and sanded it in the trough until all the chalk marks disappeared. It finished up 3mm thick in the middle and 1.6mm thick at each end. As I said before, everything that is glued to a curved surface gets sanded to that curve. Here it is, being glued.

View attachment 7505861

The other braces all went through the same process and here they all are.

View attachment 7505862

That's the front ready for gluing to the sides but before I do, I've decided to glue the K&K pickup to the bridge plate. Much easier than trying to do it blind after the box is closed. The saddle might not finish up exactly where I think it will be, but it won't be far out

View attachment 7505863

I've also made a clamping caul to fit inside the box when it comes to gluing the bridge on. Four magnets on the outside will keep the caul in place while gluing and clamping the bridge.

View attachment 7505864
Click to expand...


Wonderful. I love the purpose made caul and doing it beforehand while you can still get to everything to fit it. Precisely the type of thing I would think of moments after the top was glued on. :roflmao: :rollno:
 
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#168
The box is closed! First thing to do now is dismantle the go-bar deck and turn the base into the binding router set-up. I wish my workshop was four times as big. Then trim off the overhang on the front and back. I used to do this (very carefully) with chisels and cabinet scraper until I realised it would be much easier using a flush-trim bit.

Body 2 036.JPG


Trimming the overhang on the front and back.

Body 2 037.JPG


Body 2 038.JPG


The next thing is to make some bindings. Again they'll need to match the profiles of the sides as they are a really weird shape.
 
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#169
Well, I got the bindings and purflings made and installed the front ones. Which took a lot longer to do than it did to type it, and I didn't take photos, but they would've been more or less duplicates of the ones of the first body.This is what it looks like. I now need to install the back bindings and purflings and veneer the arm bevel.

Body 2 039.JPG
Body 2 040.JPG
 
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#170
The arm bevel is veneered and back bindings are installed. The arm bevel veneer went OK but, despite being made to match the profile, the binding on the bass side didn't want to fit easily into its rebate. I got there in the end, but it involved a bit of sanding-dust-and-glue gap filling here and there. Fortunately, it doesn't show.

Body 2 041a.jpg


A view of the blunt end. A fairly accurate view of the 'wedge' shape of the body and the curve of the top and back.

Body 2 043.JPG
 
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