Replace Broken Mandolin Top Plate

[rockies]

I need some advice on replacing a mandolin top too badly broken to repair. My own fault I must confess, this a new build from scratch, mandolin all together working on headstock and broke the top badly. Really don't want to describe my stupidity but will blame it on old age and poor eyesight. Is there a way to replace the the top plate without taking the whole mandolin apart ? I've been trying to visualize how to remove binding, cut through kerfing but how to solve the headblock, maybe remove fretboard and extender and cut across just behind the neckjoint. Any advice if anyone has done something like this would be greatly appreciated. Thanks
Dave

[Lefty Luthier]

What kind of adhesive did you use. If hide glue, a hair dryer may soften things up enough to avoid more damage but if Titebond or other similar glue, it will be a bit more difficult to not do more damage.

[rockies]

Byron, thanks for the reply, the adhesive is fish glue on the top and will let go with heat and a little water so I can get it unglued, the problem is how to proceed in the headblock area ? To get the whole top plate off it would mean removing neck etc to get the plate off. I was wondering if the top could be cut through just behind the spacer. I'm sure with all the expertise hear someone has replaced a top and can describe some ideas.
Dave

[Steve Sorensen]

Remove fingerboard and fingerboard extension support block first.

Steve

[rockies]

Steve, thank you, that was the only way I could visualize doing it. Now I'll have to scrounge up some top wood. The piece I used was Adirondack I got from Jamie Wiens (Wiens Mandolins) who lives about 20 minutes away. Hopefully he maybe has another piece he will part with. Thanks again for the help.
Dave

[fscotte]

I have done this a few times and just use a handsaw to make a cut into the extender just below the fretboard. You can clean wood off the underside of the fretboard with a chisel.

[Mark Christensen]

An animal based glue will come (relatively) apart easily once the fingerboard ext. block, fingerboard, binding etc. is removed. A lot of violin repair guys use a fine syringe filled with denatured alcohol, insert thin Luthier knife and squeeze out just enough as you work around the top. You will hear the glue crackle as it comes apart. The noise is the indicator to continue moving the knife, alcohol, knife etc.. I've found this to be easier and less potentially damaging than heat as the denatured alcohol evaporates quickly and usually releases the glue instantly, be careful of the finishes though as the alcohol will do damage. Tape off ribs etc. Try this technique on a test piece first to get used to it. Good luck.

[rockies]

Thanks all for the advice ! Mark I'll try the denatured alcohol method and see how it works. There is no finish on the mando it's in the white, when the "accident" happened. LOL I'm interested in what fscotte is describing to cut below the fretboard on the extender. Sounds like that may be a method to avoid removing the fretboard. Just need a better a little more detail. I hate having to heat up the fretboard if I can avoid it, there's always some damage to dot inlays etc if nothing else.
Dave

[fscotte]

interested in what fscotte is describing to cut below the fretboard on the extender. Sounds like that may be a method to avoid removing the fretboard. Just need a better a little more detail. I hate having to heat up the fretboard if I can avoid it, there's always some damage to dot inlays etc if nothing else.
Dave

The saw cut is made to the support block and cut almost to the 15th fret crosspiece. Stop just short of the crosspiece to avoid damage to it. The cut alleviates pressure on the fingerboard as you work to remove the top plate. I use a very sharp fine tooth blade to cut away the rest of the initial cut up to the crosspiece. Once that cut is made, the top plate is now separate from the fingerboard. Proceed with removing the top plate however you choose. You can remove wood from the underside of the fingerboard using a chisel. Just lightly scrape it away, no need to use a hammer. Any residual wood fibers can be scraped or sanded away carefully.

The biggest issue is replacing the support block. I make sure to take my time on this for a precise fit.

[Bernie Daniel]

An animal based glue will come (relatively) apart easily once the fingerboard ext. block, fingerboard, binding etc. is removed. A lot of violin repair guys use a fine syringe filled with denatured alcohol, insert thin Luthier knife and squeeze out just enough as you work around the top. You will hear the glue crackle as it comes apart. The noise is the indicator to continue moving the knife, alcohol, knife etc.. I've found this to be easier and less potentially damaging than heat as the denatured alcohol evaporates quickly and usually releases the glue instantly, be careful of the finishes though as the alcohol will do damage. Tape off ribs etc. Try this technique on a test piece first to get used to it. Good luck.

Very interesting!

I had NO idea that absolute ethanol would release hide/fish glues. :disbelief:

From a pure organic chemistry point of view it seems a bit counter-intuitive because I do not think that hide glue crystals will dissolve in denatured alcohol? Or will they?

Typically most proteins dissolve do not very well in pure alcohol.

I'd do the a little experiment on that right now but I used up the small supply of powdered hide glue I used to have. Learn something new every day!

[Bill Snyder]

Bernie try it with some Knox Gelatin.

[Mark Christensen]

Hey Bernie, Yes the alcohol actually dries the glue out and makes it brittle so it comes apart fairly easily. This is a well known technique in violin repair and can be easily googled. Using heat and or hot water actually is harder as the glue will remain sticky, it will come apart but not as easily and gums up the flow of the knife. Of course there are a lot of factors, on what strength the glue was when used and how much was used etc. I want to emphasize experimenting first on a sample as you need to know what your doing with the knife etc. Also do not get alcohol anywhere near the varnish, it must be taped off. I would read as much as possible as taking off a mandolin top is not the easiest of jobs. Good Luck

[pianoman89]

+1 for denatured alcohol. Will make quick work of any animal based glue. There is a vid on youtube (https://www.youtube.com/watch?v=QhAZSiRfDB4) of the guys at Upton bass taking off a fingerboard using this technique..

[rockies]

fscotte, thanks again for the advice on the way to keep the fretboard on (and all of you for the comments). So now I know the procedure I have to get some top wood and proceed. Hopefully Jamie at Wiens Mandolins will have something like the last wood to use. I'll contact him in 2015 after the holidays. I'll leave the mandolin top on until I have the new top ready so the ribs don't lose their shape. Again THANKS to all for the help.
Dave

[Bernie Daniel]

Hey Bernie, Yes the alcohol actually dries the glue out and makes it brittle so it comes apart fairly easily. This is a well known technique in violin repair and can be easily googled. Using heat and or hot water actually is harder as the glue will remain sticky, it will come apart but not as easily and gums up the flow of the knife. Of course there are a lot of factors, on what strength the glue was when used and how much was used etc. I want to emphasize experimenting first on a sample as you need to know what your doing with the knife etc. Also do not get alcohol anywhere near the varnish, it must be taped off. I would read as much as possible as taking off a mandolin top is not the easiest of jobs. Good Luck

Thanks. That makes some sense from a chemistry point of view as denatured or absolute ethanol dissolves water and is often used to dehydrate freshly isolated biological macromolecules like protein, RNA or DNA. I'm surprised that hide glue in the joints of a mandolin or violin contains much water in the first place. Whatever if the technique works knowing why is of lesser importance.

[Bernie Daniel]

Bernie try it with some Knox Gelatin.

Had not thought of trying that.

Of course gelatin is not really protein per se any more. It is a partially hydrolyzed collagen so it is mostly a mixture of polypeptides of varying molecular weights. I would not be surprised to know that it at least partly dissolves in absolute ethanol. Then of course hide glue crystals might be very similar to gelatin as they are also derived from collagen? So it all fits I guess.

In fact, can't gelatin be used to glue up wood instruments also?

[Bernie Daniel]

Do you happen to have a picture of the mandolin handy?

[pianoman89]

In fact, can't gelatin be used to glue up wood instruments also?

My mentor always said you can make a substitute for hide glue using gelatin with an aspirin crushed and dissolved into it. Not sure what the chemistry is behind it, but supposedly gelatin contains an additive that will not allow it to set up without the aspirin added...

[Bill Snyder]

According to Frank Ford Knox Gelatin (http://frets.com/FretsPages/Luthier/TipsTricks/KitchenGlue/kitchenglue.html) works fine (no mention of an aspirin).

[rockies]

Bernie, I'm trying hard to get rid of the evidence of my stupidity as quickly as possible. A photo would just give fodder to my so called buddies who have no sensitivity or sympathy for an old guy going through major trauma. LOL
Dave

[Bernie Daniel]

Bernie, I'm trying hard to get rid of the evidence of my stupidity as quickly as possible. A photo would just give fodder to my so called buddies who have no sensitivity or sympathy for an old guy going through major trauma. LOL
Dave


Fair enough. Well good luck with getting it fixed back up. The ups and down of wood working...and you are right one should never feed the trolls! :)

[Bernie Daniel]

According to Frank Ford Knox Gelatin (http://frets.com/FretsPages/Luthier/TipsTricks/KitchenGlue/kitchenglue.html) works fine (no mention of an aspirin).

Thanks for that link! Another one of Frank Ford's usual, over the top in quality, articles!

So if you mix up a pack of Knox gelatin and use only part of it can you let the remainder re-gel or dry in the container and then later re-hydrate & heat to liquify it again for gluing another project?

[rockies]

Bernie I think those more in the know will advise if I'm incorrect but I know things like hide glue and gelatin being an animal product will turn mouldy in time even when refrigerated. What I've done with hide glue after preparing it is to put it in small jars and freeze it. The let it thaw and then heat it back to glue consistency when required.
Dave

[rockies]

Bernie just for you. please do not let anyone else see this especially my local band members LOL
Dave

[pheffernan]

At least it wasn't the Heiden!

[Mark Christensen]

Now that I see what stage your in on the build I think you'd find it easier overall to take off the fretboard so it isn't in the way. There's no binding to deal with so it should be straight forward. Just my two cents.

[Bernie Daniel]

Bernie just for you. please do not let anyone else see this especially my local band members LOL
Dave

My lips are sealed! Looks like you were coming along with a beautiful build there too bad about the damage. :crying:

I almost wonder if it could not be glued back?

[pianoman89]

Bernie I think those more in the know will advise if I'm incorrect but I know things like hide glue and gelatin being an animal product will turn mouldy in time even when refrigerated. What I've done with hide glue after preparing it is to put it in small jars and freeze it. The let it thaw and then heat it back to glue consistency when required.
Dave

I had some trouble with this, and finally realized if I use distilled water when mixing up the glue, the problem goes away. The mold is apparently caused by impurities in tap water.

[Bernie Daniel]

I had some trouble with this, and finally realized if I use distilled water when mixing up the glue, the problem goes away. The mold is apparently caused by impurities in tap water.

Or perhaps you could boil the water first to destroy the spores?

When you are finished gluing I was wondering if you couldn't just let it dry (to hardness) -- that will stop any bacterial or mold action -- then add back water when you want to glue again?

The famous experiment of Louis Pasteur (1822 - 1895) is still on display at the University of Strasbourg in France. Pasteur boiled water in a glass tube then sealed the tube so that dust particles and air could not enter it. The water in the tube has remained clear and microbe free for over 200 years now. :) That was how he first proved microbes are in the air and that the theory of "spontaneous generation" was bogus!

[pianoman89]

Boiling the water would probably work. I should say the glue began lasting long enough for me to use of what I had mixed without molding. Im sure it would mold sooner or later left out in the open. Maybe one could all a new level of sophistication to their instrument using "Earths finest water from Fiji's artesian aquifer" to mix their glue...lol

[rockies]

Well thanks to all on the forum with the great advice. Taking the extender out worked great. The alcohol trick worked perfectly to get my nerve up, and also worked to release the glue. The top came off with no damage to the kerfing or ribs. New top carved once I obtained some wood (Adirondack) and installed. As mentioned hardest part was shaping the new extender so I fit perfectly so it wouldn't affect fretboard geometry. So again thanks to all I am now back to the point before the disaster.
Dave

[David Houchens]

rockies, Hopefully there is never a next time, but I once removed a total loss top by turning it loose beneath the fret board extender and and using a long spatula between top and head block and sliding it out at that point. Thicknessed the new top to be a tight fit beneath the extender. Just another skinning, same cat.