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Martin 000C-16RGT Side Crack

10/2006

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1. A Side Crack can be a scary problem for a guitarist to confront. Not to worry. They are typically quite manageable. This 000C-16RGT came to us with a side crack that resulted from an impact with a foriegn object. This crack started at the pre- amp and ended at the neck block. 2. A Crack at the Lining prevents me from reinforcing the crack inside the guitar with cleats (without the costly task of breaking away small sections of the kerfed lining). Many of the more costly instruments have side reenforcement (cloth tape, cotton soaked in glue or small pieces of wood) that run the width of the sides and often behind or into the lining. This reenforcement both helps prevent cracks from occuring and spreading when they do occur.
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3. With the Electronics Removed I’ll be able to better access the crack. This crack may well have not occured if this guitar did not sport an onboard preamp mounted in the side of the guitar. 4. Gluing the Crack with hot hide glue will make future repairs more effective in the unlikely event that this crack opens again (hide glue is water soluable and therefore may be cleaned up with water, even years after it has cured). Although hide glue has a short open time (about 15 seconds) it creates a very strong bond that is reversible. I will glue and clamp the crack one section at a time. I would never be able to properly align and clamp the rose- wood within the short open time of hide glue if I attempted to glue the entire crack all at once.
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5. Spool Clamps provide quick and even clamping pressure. Since these clamps are lined with cork padding there is no risk of damaging the instrument’s catalyzed lacquer finish. 6. Glue Squeeze Out indicates that I’ve worked enough glue into the crack.
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7. Measuring for Side Re- enforcement with a divider will help me lay out the side reenforce- ment I’ll be fabricating. 8. Rough Cutting the Side Re- enforcement from some scrap Indian rosewood with a coping saw only takes a minute. The trick to using a coping saw is to make fast, light cuts, essentially imitating slow feeding into a scroll saw.
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9. Planing the Rosewood to finished width is most easily done with a block plane that sports a razor sharp blade. 10. Sanding to Finished Length with a disc-sander is loud, but effect- ive. This disc/belt sander is probably the most used power tool in our shop.
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11. Planing the Rosewood to Rough Thickness isn’t so difficult with the aid of our adjustable bench dog. 12. Fitting the Rosewood’s Gluing Surface is necessary since the sides of the guitar are not flat. I’m using a form used for assembling a guitar as a backing for some 220 grit sand- paper to shape the gluing surface.
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13. This Side Reinforcement is Ready to Rock, almost. First I’ll lightly scrape and wash the gluing surface with mineral spirits to get rid of as much rosewood dust and sanding grit that I can. This will fascilitate better gluing. These pieces of rosewood won’t reenforce the crack at the lining. They will, however, help prevent future cracks from forming in this same portion of the side. 14. Gluing the Side Reenforce- ment with magnets. The magnets act as clamps. I’ve chosen to increase the strength of these rare-earth magnets by sticking large washers on the backs of the magnets. The magnet does some kind of black magic to the washer which, essentially turns the washer into another magnet thereby increasing my “clamp’s” magnetic strength. The option of using washers gives me more versatility in clamping pressure for various jobs, thereby giving me greater control.
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15. Gluing the Side Reenforce- ment Cont. I’ve padded the outside magnet and washer with some rubberized cork to prevent my “clamps” from damaging the finish. A note of caution: these magnets are very strong. It’s important to be careful as they will literally fly out of your hands and latch onto nearby metal objects and each other. As a rule, I always put the outside mag- net in position first, then carefully place the inside magnet against the clamping surface. This is further insurance against damaging an instrument’s finish. 16. Measuring for Crack Reenforce- ment only takes a couple of minutes with the aid of our inside calipers.
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17. Laying Out the Crack Re- enforcement. Since the lining is in the way of installing cleates I’ll be gluing cotton accross the lining and the side to help reenforce the crack. It’s not ideal but breaking away enough of the lining to install cleates would be very time consuming and costly: which is usually only ap- propriate on the more costly instru- ments. 18. Cutting Out the Crack Re- enforcement from some cotton fabric.
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19. Soaking the Fabric in Hide Glue. Back in the day, this is how the manufacturers reenforced the sides of their instruments during assembally before gluing in the lining. A very effective, but time consuming method of side re- enforcement. 20. Gluing in the Crack Reenforce- ment. I’m wearing a rubber glove to keep my hands free of hide glue. By the way, I’m not too concerned about the added mass of the side and crack reenforcement effecting the tone. The sides of a guitar are meant to be a stable surface to which the bracing delivers the load of the strings. There are a lot of highly sought after guitars out there with very stiff sides made of plywood (Gibson J-45s of the 1950’s and 1960’s, for example). Reenforceing cracked plates (tops and backs), however, is a different matter.
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21. A Reenforced Side. I let the glue cure over night then went back and cleaned up the excess glue with a paper towel moistened with warm water. This trick of reenforcing side cracks at the lining came from the bench of San Francisco based repair man Frank Ford. 22. Sealing the Crack with Shellac will keep any dirt, oils or guitar cleanersand polishes from penetrating intothe rosewood’s pores. Crud in thepores would make future repairs orfinish work on this crack more difficultthan need be and, perhaps, lesseffective. I’ve taped off the sideswith “low tack” masking tape to preventexcess shellac from getting on thelacquer finish. I’ll brush a couple ofquick coats of shellac into this crack.By the way, I cleaned up any excessglue from the outside of the guitarwith warm water a few hours priorto sealing the crack with shellac.
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23. Cleaning off the Excess Shellac is pretty safe and easy with a paper towel lightly dampened with alcohol (the solvent in shellac). A little bit of alcohol will have absolutely no adverse effects on this lacquer finish. 24. Cleaning off Any Residual Alcohol with a paper towel dampened with distilled water.
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25. A Glued Crack. The owner of this guitar didn’t opt for the finish touchup, on my recomendation (it can always be done at a later date). Consequently, the crack is a bit more visible than it would be otherwise. But since I was able to accurately line the side up with itself when I glued the crack, the repair is none the less subtle. 26. All Done!