#1
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back plate and upper rib angle
Firstly happy thanksgiving to all the American folk on the site.
I have a question that maybe someone can answer ... I am almost ready to put the back(round-back) onto my French bass after replacing the linings . Now the upper ribs have been cut back slightly , I think that this was simply part of the standard building plans and not done at a later stage in the basses life . When I clamp the back plate on, the plate will have to bend to meet the ribs on the upper bout seeing that the back plate inside edging is ruler flat.The widest part of the gap is about 20mm. Its easy to simply glue and clamp the plate back on BUT surely its not a good thing to have the upper back bout pulling against the neck block etc . It wont come off but Im worried about the seemingly unnecessary tension on the instrument. Any insight would be great .. |
#2
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I found this pic .Is this the way to go perhaps , cutting an angle into the back plate ? The angle on my bass is not quite so steep.
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#3
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So is your back bent (like the one in your photo) and it just isn't a steep enough angle to mate up? Or was it made flat? I'm wondering how it was attached before... or was it?
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#4
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Thomas yes the bass was built like that , the back is not bent (cut) to the angle of the upper bout ribs ,but it does not require any major torque(due to the flexibility of the thinnish maple back) to get it flush with the ribbing and the button . Once glued properly especially to the back of the neck heel it will easily stay in place and be a perfect 'visual' fit.... BUT there will always be that bit of pressure pulling away from the heel and thats what I'm interested in / can this actually inhibit the sonic potential of the instrument ....??? My understanding is that an instrument does not want to have any unnecessary structural tension related to it's build ?!? |
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#6
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There are 3 possibilities 1. as you say , the back lost its shape 2. the ribs were cut down at some stage 3. the maker didn't mind 'springing the back' I have attached pic with a torch shining in the gap to highlight the gap... |
#7
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Make sure the back makes good contact at the upper bout linings and neck block. Of course you want to size the blocks. Then glue the back on starting at the tailblock, and working your way up. (You'll need to keep it temporarily clamped at the button area to maintain alignment.) This method will spread the "spring", just like the original maker did. Hopefully, you have already flattened any obvious high spots, and made sure the glue surfaces are true. The small amount of spring in the back will actually tend to counteract the string tension, so don't be concerned.
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#10
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I was doing it in order of thread ... BTW how did that 2'' sprung flat-back ,back sound and play when you were done with it ? |
#11
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French Backs..
Ok, I waited to reply and didn't see anyone mention this.
French basses are often built with a gradual bend from the upper corner block to the neck button as opposed to the obvious upper back bends as seen on many German, Viennese, Italian and English basses. This is normal for French basses. Here are the links to 3 of my French basses (past and present) with gradual bends to look at and compare. It is quite common on French basses. http://www.kensmithbasses.com/double.../jacquet-gand/ http://www.kensmithbasses.com/doublebasses/vuillaume/ http://www.kensmithbasses.com/double...uet-pillement/ Follow what Arnold has told you. He is the most experienced restorer here on the Forum and knows his stuff. Thank's Arnold for chiming in. |
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