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Is this flaw fatal?
http://luthiersforum.com/forum/viewtopic.php?f=10101&t=38931		 Page 1 of 1
Author:  Spyder [ Mon Jan 14, 2013 3:37 pm ]
Post subject:  Is this flaw fatal?
Seems that after all this time and work, I may have made a fatal error in this one. I didn't realize it until i routed off the bindings I'd installed so I could recut the channels to proper dimensions. Then I found it.

Apparently, I had a bulge in the side where it met the back in one spot. And while sanding everything flush after gluing on the back, I almost sanded through the side in one spot.

gaah gaah gaah

Best I can measure, there is about .010 of side material left over the lining. On the plus side, it is only in this one spot, on the top it appears full thickness. And, if I press with my finger, it doesn't feel like it would be that easy to poke through. But, I am afraid now that this one should not be sold, unless at a very discounted price.

So what are my options here? Should I finish it anyway for the practice? And when done, use it for a banger/travel instrument? Or just call it, write it off as lesson learnned, and start over on the next one? I'm afraid that the top may have a slightly odd contour because of this, meaning I'm not sure if it could be reused. (I didn't have forms for these first two.)

Any suggestions?
Author:  WudWerkr [ Mon Jan 14, 2013 3:44 pm ]
Post subject:  Re: Is this flaw fatal?
Larger pic of guitar showing exact location ? Upper bout ? lower bout ?
Author:  arie [ Mon Jan 14, 2013 3:47 pm ]
Post subject:  Re: Is this flaw fatal?
imo keep it, experiment on it, throw darts at it, but don't sell it -your reputation will be damaged unless your repair is awesome and totally transparent. take your licks and never speak it's name again. :-)
Author:  Casey Cochran [ Mon Jan 14, 2013 3:49 pm ]
Post subject:  Re: Is this flaw fatal?
I would brace it and finish for use as a campfire guitar. More importantly, have you figured out what caused the hump?
Author:  Spyder [ Mon Jan 14, 2013 5:03 pm ]
Post subject:  Re: Is this flaw fatal?
Hey everyone, thanks for the replies. You've given me plenty to think about. As for the location, if you consider the back as a clock, with the neck at 12:00 and the tail end at 6:00, this flaw is at 6:30. At the same position on the top it is fine.

I glued this up free form. I thought I was being careful, but as my wife says, "another thought, another mistake."

I'm not sure exactly what happened. I know the sides had several minor bumps after it was all glued up, so looking back, my best guess at this point is faulty bending. This was my first attempt at bending guitar sides on my home made hot pipe, and I noticed that ash (even quilted) bent much easier and better than the walnut. I suspect that may have been the big contributor.

So if I remove the back, will it be necessary to replace all the linings?
Author:  askins [ Mon Jan 14, 2013 10:04 pm ]
Post subject:  Re: Is this flaw fatal?
If you have another set of sides, perhaps bend another thin set and laminate it to the outside of the existing sides?
Author:  Mark Fogleman [ Mon Jan 14, 2013 10:49 pm ]
Post subject:  Re: Is this flaw fatal?
How about Weymann ribs?
Author:  jfmckenna [ Tue Jan 15, 2013 8:47 am ]
Post subject:  Re: Is this flaw fatal?
You have the best advice given so far but let me just tell you my story. I did the same thing on my second guitar I ever built. This was when I was still learning basic wood working never mind luthiery. I even sanded to the linings on the very top edge which eventually was cut out for bindings but it just goes to show how close I was. Anyway, I did nothing and this guitar I still have, a 12-string, and it's 20 years old now.

Having said that, if I had advice like is given here I'd probably follow it. But at that stage of my building I felt it was better to just move on to the next learning experience.
Author:  Tom West [ Tue Jan 15, 2013 9:06 am ]
Post subject:  Re: Is this flaw fatal?
Just a thought.................Boy that sounds so dangerous....!!! If sides are bent with lots of water they will tend to end up wavy across the width. The outer edge will tend to be more proud and perhaps this is the case here. The thinnest wood may be at the edge with .030" or so thicker at the centre section. Just something to consider. If you do deside to proceed with the reenforcement,don't forget to back up the lining. The back looks like it's holding on by a very slim amount. Hope you get it worked out.
Tom
Author:  Mike OMelia [ Wed Jan 16, 2013 12:18 am ]
Post subject:  Re: Is this flaw fatal?
Campfire guitar? For sound or heat? Sorry this happened. I think the best thing is to figure out how it happened. Do you use a solid mold? It looks like you might not have done that.

Mike
Author:  Mike OMelia [ Wed Jan 16, 2013 10:38 am ]
Post subject:  Re: Is this flaw fatal?
Yeah, I agree. It's harder to do with an outside mold, but not impossible. I use outside molds and spend a LOT of time checking the fit and making adjustments. I'm guessing that the OP was trying to sand away a distortion in the shape. The top is the easiest thing to remove (least costly, and does not need matching). So if you want to save it, remove the top. Add a patch, and keep it in your collection.

This makes the body a bit thinner, right? (talking about back to front)

Mike
Author:  Spyder [ Thu Jan 17, 2013 12:20 am ]
Post subject:  Re: Is this flaw fatal?
Thanks everyone for the replies, and I think several of you nailed the problem. I am now convinced it was poor bending of the sides to begin with. This was my first attempt using my home made hot pipe, and I struggled. I have made quite a few dulcimers with walnut, and those sides all bent well. All i had to do was clamp the piece in my workmate, apply dry heat with a heat gun, be patient, and it would bend fine. Later I learned to dip it in boiling water in an electric skillet then apply dry heat, sped things up a bit. But, I learned there is a BIG difference between the sides of dulcimers and guitars. Dulcimers are narrow sides with gentle bends, guitars are wider sides with much deeper bends.

These sides were flat sawn, chosen for looks. (My first choice was gonsalo alves, but the back split on me so this was a way to keep going since I had the material on hand.) I had a lot of trouble getting the curves bent, and ended up with some cupping. I managed to get most of it back out, but not all, hence the buldge in question here.

In hind sight, I should not have used these sides, but made better ones at that stage of the process. I checked today, and I don't think I have enough thickness in one spot to survive finish sanding without sanding through. But, today I am where I am, question is, which way do I go from here?

I am thinking now to take a design cue from the old bowl back mandolins, and add a decorative wrap around feature on the end of the guitar. It will make finishing more difficult, but will look different and if I pull it off, will look pretty neat.

Or, I can remove the back. Mike, is the top really easier to remove? And why?
Author:  Alain Lambert [ Fri Jan 18, 2013 10:22 am ]
Post subject:  Re: Is this flaw fatal?
Bend and fit an inside patch, same thickness as the side (same material preferably) glue it with HHG.
There should be a way to hold the patch while the glue set without removing the top or back.
This will take care of structural integrity.
Finish the guitar, if you do not sand through, your are good to go. If you sand through on that spot, then make it a black guitar!
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