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I build cigar box musical instruments but have only ever done guitars up till now. My wife 'suggested' she would like to learn to play violin so I of course foolishly suggested I might build her one.
Much research and a moderate amount of work later I put together a nice little CBV (cigar box violin). Some constructive criticism of the video I posted on here (and my own experience of actually playing it) led me to the conclusion that the action was too high near the body - OK for playing first position but would rapidly become very hard to finger. I also felt the neck profile was too fat and square.
Thankfully my research had led me to discover the benefits of hide glue, in my case specifically a ready made (yet using a traditional recipe with no modern additives) product called Old Brown Glue. I used that for all parts of the assembly of the CBV so it meant I had a fair chance of modifying the instrument without damaging it.
This morning I removed the strings, tailpiece, tuning pins and chin rest to be left with a bare instrument. I wrapped the body in a plastic bag so it would be insulated from the next stage of the process (I had glued the two halves of the cigar box together using the same adhesive so did not want that joint to open up) and put a small pan of water to boil on a little electric ring my wife uses for cooking dye materials.
Five minutes of moving the neck back and forth upside down through the steam from the boiling water, the application of some very gentle leverage between the neck and the fingerboard and hey presto! Off popped the fingerboard completely intact, similarly no damage on the neck either. I sanded down a couple of loose flakes of glue but did not worry about removing every last bit of residue - one of the other nice things about hide glue is that it will stick to itself (unlike regular white PVA wood glue).
I have now manufactured a thin wedge which I have glued onto the neck, once that is dry I will re-glue the fingerboard and we should be good to go.
Some work with a rasp has re-profiled the underside of the neck, I may yet slightly enlarge the cutouts either side of the body for a little more bow clearance when playing the outer strings and I will replace all the other bits and pieces and hopefully have a much more playable instrument.