Ruined Back

[Dave Bagwill]

You might try this guy, he may very well have a orphaned claro back available

tonewood.com/guitar-wood/acoustic-guitar-tonewood-sets/claro-walnut-acoustic-back-and-side-sets

[Dave Bagwill]

John - Before I got a drum sander, I used the following method to think back and tops, and it works fine. Patience needed, but you will get a nice flat and dimensioned back or top.

See pic attached.

The .10" strips of metal are a couple of buck apiece - mine had holes already drilled in them - I screwed them to a flat piece of mdf, and used them as bearings, basically - they keep the sanding stick from sanding thinner than .10" minus the sandpaper thickness.

The sanding stick - since you will be bearing down on it - has to be very rigid and in fact I used the fence from my bandsaw, and used spray adhesive to attach a sandpaper strip (60,80 grit or so) as long as my back was wide - I think it was 16" - the important thing is that the bare part of the bar - on either side of the sandpaper - rides on the steel strips.

I attached the outer edges of the back to the mdf using the 2 strips of masking tape and CA method, and the back stayed put no matter how much I kept at it.

Draw witness lines and go to town. It may take a half hour, or more, but the results as I said, are fine.

[Dave Bagwill]

I threw together a quick pic:

[John DiMaggio]

Thanks everyone.

Dave - I will try your method - looks good.

[John Link]

John, You might try contacting Allied Lutherie. They sell their "standard" back and side sets separately. In their "weekly specials" they list walnut sets (Back + Sides) but not in their "standard". However, I have found them very helpful when looking for something they and no one else lists. Just ask if they have an orphan back set in walnut. They might.

Ervin Somogyi says he sometimes makes backs as thin as 1.27 mm (0.050 inches) in his quest for a "responsive" back. As I understand his building, I am confident the thicknessing would be dead on accurate and homogeneous, even though he says he does it all with a hand plane.

Myself I have gone as thin as 0.0625 inches with well quartered IRW and did get a few waves after bracing that are visible with a gloss finish and viewing with side light. IRW is relatively stable and the almost absolute perfect 90 degree grain probably enabled me to get by with it to the extent I did. Eventually, however, it came back with a crack I had to repair.

One thing Ervin points out is that the most responsive back in the world does not make much difference if you hook up a strap, stand up, and let the instrument hang, resting full on the belly, with an arm laying on the top for playing.

Those belt sanders are dangerous; they wiggle, they wobble, and they destroy.

[John DiMaggio]

John - Before I got a drum sander, I used the following method to think back and tops, and it works fine. Patience needed, but you will get a nice flat and dimensioned back or top.

I attached the outer edges of the back to the mdf using the 2 strips of masking tape and CA method, and the back stayed put no matter how much I kept at it.

Draw witness lines and go to town. It may take a half hour, or more, but the results as I said, are fine.

Dave,

What is the 2 strip CA method?

Thanks

[Dave Bagwill]

My bad - I got in a hurry and didn't 'splain.
It's an easy way to make your own 2-sided tape. Some pix follow to give you the idea. A couple of pix show a bridge blank that I simply taped to the bench and planed/scraped - the blank did not move under any pressure - then releases very easily. The other pic was attaching a strip of sandpaper to a shooting device - the pic shows the sandpaper strip with masking tape stuck to it, and a matching piece of tape on the device.
Masking tape on the piece to be attached - matching tape on the piece to be attached to - and a thin bead of CA in between.

I'm almost half awake, so if this isn't clear just say so and I'll take another shot at it. :-)