Official Luthiers Forum!

Looks like you might have glued it up on a flat surface and lost your neck angle?

Filippo,

Don't tell me you forgot to remove the clamp that holds the soundboard to the solera!

Steve

Did you forget the top?

Oh that would SUCK!

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I feel your pain brother! I'm working on #3 and I have found some pretty creative ways to make mistakes. Hoe you can make it work without too much extra work.

Good Luck
Danny

Great topic BTW

Haha, that would be time to try a large soundport.

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Evan McCartney

Two ways of doing it. Parting knife and let the glue/joint crack. That's often used by the Violin repair people to remove Backs/tops. Generally speaking it relies on a relatively weak glue mix. There's always a danger of taking off wood if the joint is too strong. You also have to be aware of grain runout.
I've never tried it but I have heard of people feeding in strong alcohol, which is supposed to make the glue more brittle.
The other method is to use a parting knife but to feed hot water into the joint. Give it plenty of time to work.

Forgot to mention. You may be well advised to pull a few strips of masking tape across the Back Joint, where it goes over the slipper foot. There's always a danger of freeing the joint when trying to remove a Back.

Man, Filippo! I feel your pain. I had to take the back off of #2, glued with fish glue, and it was a beast. The back and linings came out OK, but I had to replace all the braces. I recommend getting some moisture in the joints with pallet knives or sharp putty knives sharpened and dulled, so there are no sharp edges. Keep them in hot water - the hotter the better, and while wet work them into cracks, while heating the joint with an iron, carefully. Check your joint carefully, and find a likely starting place. You will make a mess, but it should clean up pretty well. It warped my back pretty bad, but I was able to get it settled back down once dried out. Fish glue is not friendly in the removal area. I've never tried getting the joint to crack, like you would on a bridge, but I suppose that might work too. The thinness of the back would scare me out of that, but it might be a very legitimate way to do it.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I wonder if a fein cutter or dremels new oscillating cutter would be any good for this type of thing??

Too tired at this hour to understand what went wrong, but having to take the back off surely sucks. You have my sympathy....

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Build log

Not really. or rather they might be a very last resort. Any saw type cutter is going to remove material (however little) and it's not really necessary in this case. Don't forget that there are folk out there taking apart some very precious and expensive instruments and putting them back together again. Think Strads, Torres. Lacotes et al. Fillipo really has to release part of the sides and the slipper foot. For this type of work you really do need patience. Rush it and something is almost certainly going to go with a crack.
I;m not the best at that type of work. Unfortunately I'm far too 'A' type. Hopefully Fillipo is more B.

I think the A approach was what cost me my braces!

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I'm kinda lost, what's happened here?

When I do up a neck, I leave a ton of extra material on it and then thickness etc... later when I carve it.
If you've done the same thing, you might be able to make up the angle when you shape up the neck rather than taking it apart.
I can't see the head to be able to tell whether or not this is a possibility for you.

Good luck.

Dave

PS, glueing things together without taking the clamp block out of the workboard is a bad mistake to make too.
Been there, done that.

I really lke Daves advice particularly if you have a thick FB
Isnt the typical lift only around 1-2mm over the length of the FB?

Hold it Fillippo!
From your description it sounds as if you were tryng to put a negative angle on this?! (i.e. the nut being lower than the plane of the top) as opposed to the positive neck angle or "lift" that is properly found in the classical guitar.
Am I misinterpreting your verbal descripton??

If indeed your neck/top are in the same plane, you can create the proper "lift" simply by tapering the fret board......no need to remove the back.

I took it to read as that there is too much of a positive angle, hence the gap between the reinforcing strip and the heel.
Once you have established the correct angle for your particular model you can fix that angle permanently into your solera. It shouldn't ever become an issue again, unless of course you change some of the other parameters.

Right now, precisely, what is the distance between fingerboard plane and top, at the bridge (mention if frets are included). Make sure the FB is well pressed on the neck when measuring, and tell us the thickness of the FB at each corner.

Even if we decide the geometry is OK, a gap between foot and back seen from the soundhole is not the best thing you could show someone inspecting your work!

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Build log

I understand it now. The gap is between the heel and the actual Back - which would indeed indicate more of a negative angle. 3/16" gap is too large to ignore IMO - even though the majority of that gap will be towards the front edge of the slipper foot.

Filippo,

My condolences. The back on the one I've kept for myself had to come off for the same reason. Using the Schramm method, I measured and got my shims together, and then glued up the back without the shims in place. Maybe this is the downside of the method. If the geometry really is fixed by the solera, none of this messing around.

Fish glue is a bear to undo. Waddy's advice is good. I didn't lose any back braces on mine. (I glue braces to the back first anyway, not to the sides

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Jim Kirby
kirby@udel.edu

Don't take the back off, just work out the geometry you need to get the right bridge height/action and taper the fingerboard. A lot of the great builders did it this way, in fact it is the most traditional way of doing it.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Colin. That would only work if the neck was in the same plane as the body. A 3/16 th's gap suggests that it has gone a bit too far the other way, and of course tapering the fretboard will not close that gap between the foot and the Back.
I guess the worst that can happen is a new Back but providing real care and time is given to removing the original it really should be possible to release it and save it. It's just a matter of using the correct technique and approach. Think of it as a real valuable Torres! Tends to focus the mind.
Filippo, you can also glue a 'dummy' back to a 'dummy' slipper foot and practice removing the joint. In fact you can do several to get a feel for what is required. It's much better to do that than diving head first into your actual Back.

Fillippo,
Richard Brune' specifies a 2mm lift at the nut (2mm above the plane of the top) in his specs for the '37 Hauser plus a tapered board. Did David actually specify a neck angle? Or is he relying on the builder to determine it from his method?
That way of getting the angle seems difficult to me. I did it simply by working on a flat solera and blocking up the top with a 2mm thick piece of illustration board shaped to the plantilla under the top with the nut end of the neck clamped to the flat surface to create the 2mm lift. I'm now using a Solera wth this angle built in so I hardly have to think of it at this point.

I would not take the back off but would attempt to fix the back strip issue by popping that section out and fitting a new section which matches the rest.
If indeed your neck and top are in the same plane (which many builders did) a tapered board (say 7mm down to 4) should allow the correct action height (4mm bass 3mm treble) using a slightly taller bridge but you will need to determine the actual measurements.

Fillippo, I hope this helps to illustrate (albeit crudely) what I am talking about.

The built up area of Waddy's form (and mine as well) is to create a drop off at the back of the guitar which enhances the doming (why you scooped out your solera) of the top.
Postive neck angle as illustrated places the neck fingerboard mating surface ABOVE the plane of the top (as illustrated). The flatter this angle is, the more you can taper the fretboard to create it.