Noob crack repair question

[DMand]

For a soundboard crack on an old flatback, it it better to try to glue the crack first, or take the back off, adjust whatever needs adjusting and then glue? I have basic instrument-working skills and tools, just no experience with old mandos. This is an old 1915 Washburn I'm looking at. Thanks in advance! Dave

[Bill McCall]

Taking the back off is way beyond basic. You might get an experienced repair person to give you a quote on the cost of the repair if the instrument's value is a consideration. Its much easier to make a mess than to make a clean repair.

[Richard500]

Related question, re. large cracks, as in photo. Given that it’s not an important or expensive instrument, would you add a tapered shim and glue, followed with an internal cross-grain reinforcement, or try to compress the instrument (or top) to it’s original dimension, with or without removal?

[sunburst]

First question (OP):
Removing the back is a last resort. When possible, most of us repair cracks without any unnecessary dismantling of the instrument.

Second question:
Compressing the mandolin to it's original width (if we can even know what that was) very well might not close the crack because the wood may well have shrunken from it's original dimension. If the top and back are the same width, that's probably the best that can be done, so comparing the measurements is the first step. The top may need a splint to maintain a similar width as the back. (This is assuming that the back is sound, and various other assumptions I am making because I cannot examine the mandolin in hand.) As for reinforcement, I don't know without looking.

[rcc56]

Please post pictures, DMand. Without them, we can only guess what the instrument needs.
And as John said, we avoid opening mandolins except as a last resort.

As far as Richard's mandolin is concerned, even without the instrument in-hand, I have no doubts about that one. It will have to be splinted.

My rule of thumb is that if a crack will close with no more than very modest pressure, I will glue and go.
If closing a crack requires much force, the crack will either open up again later, or a new crack will develop next to the old one.

I am sure that the wood has shrunk on Richard's mandolin, and the brace[s] are almost certainly holding it open and will prevent the crack from being closed.

The only way to get around installing a splint in this case would be to open the instrument, loosen the offending braces, glue the crack, re-assemble, and touch up. I do not recommend that approach here under any circumstances. Splinting is a far easier repair and will produce adequate structural results. You won't get an invisible touch-up, but it's not a Strad. Strive for a nice looking touchup rather than a match.

If you can get clean gluing surfaces and your splint fits snugly, cleats will probably not be necessary. But if you have any doubt about the fit, a couple of cleats won't hurt. Most cleats I see used in fretted instrument repair are much too heavy. Keep them small [perhaps 1/2"], as thin as possible [.080" to .100"], bevel the edges, and install them cross-grain.

[Charles E.]

Pictures of the mandolin would help to evaluate what might be the best course of action.

[DMand]

OK. Have the back off with just a few chips of binding I'll have to replace. Found the best way to open it up was initially using a pallet knife heated with a tiny heat gun.
I'm going to remove the front ladder braces, reglue the top cracks, and reshape the sunken areas above the soundhole with steam, clamps and a basswood form.

So two questions:

1. on this oval hole Washburn 1915, should I just put the old ladder braces back on the top, or has anyone found better results with X-braces? scalloped braces?
2. a good source for thin black mandolin binding?

Thanks! DaveH

[ProfChris]

So two questions:

...
2. a good source for thin black mandolin binding?

Thanks! DaveH

Might depend where you are. In the UK, there's a limited range available.

But you can always trim down binding, making a scraper jig using a Stanley knife blade to thin it down.

Much black binding is ABS, which can be hard to glue. Celluloid would be traditional if you can find it. Or ebony if you want wood binding. Direct from China via eBay gives a wide choice of plastic/celluloid if you're not in a rush for delivery.

[rcc56]

As far as the bracing is concerned, you get to choose. If you go with ladder bracing, you can use the old bracing as a rough model, although you may wish to make some adjustments. If you use X bracing, you can check old posts from some of the English and Australian builders to see if they have posted any info on dimensions, angle, and placement. Whatever you use, make sure that the area that is in front of the soundhole and under the end of the fingerboard is adequately supported.

Black ABS binding is available from Luthier's Mercantile in thicknesses of .020", .040", .060", and .080".
Rothko & Frost in the UK sells black bindings in ABS, PVC, and CAB [whatever that is].

Black celluloid binding is available in the US from Axiom Inc. www.axinc.net. They are required by law to charge a stiff hazardous materials fee for any shipments containing celluloid; so if you order from them, you might want to order plenty of celluloid, since the fee is the same whether you buy 1 piece of binding or 100 lbs of it.

[DMand]

Wow, thank you! Great leads!

Dave

As far as the bracing is concerned, you get to choose. If you go with ladder bracing, you can use the old bracing as a rough model, although you may wish to make some adjustments. If you use X bracing, you can check old posts from some of the English and Australian builders to see if they have posted any info on dimensions, angle, and placement. Whatever you use, make sure that the area that is in front of the soundhole and under the end of the fingerboard is adequately supported.

Black ABS binding is available from Luthier's Mercantile in thicknesses of .020", .040", .060", and .080".
Rothko & Frost in the UK sells black bindings in ABS, PVC, and CAB [whatever that is].

Black celluloid binding is available in the US from Axiom Inc. www.axinc.net. They are required by law to charge a stiff hazardous materials fee for any shipments containing celluloid; so if you order from them, you might want to order plenty of celluloid, since the fee is the same whether you buy 1 piece of binding or 100 lbs of it.

[DMand]

So, finishing things up. The top was really a pain, not only warped, but really thin. I wound up rebracing entirely with carbon fiber 3mm rods and added a triangular patch of Carbon Fiber twill in the center, where the wood was very thin. That was in addition to the carbon fiber annular ring around the sound hole. The soundboard is now very stiff and light.

I added some microbead pore sealer to the front of the soundboard, from Luthier Mercantile. The cracks are now invisible, disguised by a combination of faux graining, and a bit of resin filler. If it was a new mandolin, I would have just replaced the top, but I wanted to see how I or if I could bring this little guy back from the dead using some postmodern materials.

I guess I'll see how it all sounds when everything is glued up.

I didn't cleat the cracks because the Carbon Fiber and hide glue seemed to do the trick. Will post photos when I begin sealing it up and final finish. If it breaks under string tension, oh well, but I'm cautiously optimistic. It was a learning experience, and I would certainly do a more finished carbon fiber bracing the next time, but all this was an experiment. Keep y'all posted. Dave