Soundboard Repair. . . .

Construction and repair of Classical Guitar and related instruments
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Michael.N.
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Soundboard Repair. . . .

Post by Michael.N. » Wed Aug 03, 2011 3:38 pm

Bit of a nasty ding and this is after steaming multiple times. . . . .

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No idea how it happened, luckily this appeared early on in a build. 99.999% of the time they decide to make an appearance just as one is doing the final polishing.
Not to worry. Providing we have a suitable piece of Spruce we can make it all but vanish. An off cut from the soundboard is the obvious choice. If we choose the piece from the same side of the soundboard we won't have a problem with colour/reflection mismatch. It is much more difficult to execute a near invisible repair if we have to select from pieces of Spruce that do not belong to the original soundboard.
The diagram shows the shape of the patch needed - the so called rugby ball (or American football) shape. The dotted line within the patch indicates the ideal of matching a grain line - fussy but helps to fool the eye into believing we are looking at original wood.

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I use a Scalpel to carefully cut out the shape on the original soundboard.

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Now we need to cut a similar shape on our off-cut, making sure that it is a little larger than the cut on the original soundboard.

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Now it is a simple matter of transferring our patch onto the crevice we created on the soundboard. Don't flip the piece and create reflection problems. I glue with Hide and gently compress the patch into place. Clamping helps.

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Allow to dry and then scrape or sand the patch level.

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In pragmatic terms it is 'invisible'. At least it's good enough for my ageing eyes. Picking out a grain line went a long way to the success of this particular repair. I had 3 goes at this to match the grain. Sometimes it can take many more attempts than that.
Just remember: Practice on scrap.
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Robert England
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Re: Soundboard Repair. . . .

Post by Robert England » Wed Aug 03, 2011 3:45 pm

Thanks, Michael. Wonderful tutorial!
Robert

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George Crocket
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Re: Soundboard Repair. . . .

Post by George Crocket » Wed Aug 03, 2011 4:07 pm

Amazing :shock: .
George
2010 Stephen Eden spruce/cocobolo classical guitar
2012 Stephen Eden cedar/IRW classical guitar

johnparchem
Amateur luthier
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Re: Soundboard Repair. . . .

Post by johnparchem » Wed Aug 03, 2011 4:19 pm

Thank you, I will give it a try on some scrap I have. Most of my previous efforts have results that look worse than the original ding. Matching a grain line and the direction of the patch to keep reflection looking right are great insight.

Scot Tremblay
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Re: Soundboard Repair. . . .

Post by Scot Tremblay » Wed Aug 03, 2011 6:50 pm

Excellent Michael! I've got a couple superb tops with pitch pockets in almost the same exact spot as your ding. I was thinking of using them for vihuelas where I could hide the blemish with decoration but maybe...
Scot Tremblay Guitars

"One picture is worth a thousand words. So, for me, one good note put where it should be put, will say what it will take some people many notes to say. ~B.B. King, 1986

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Michael.N.
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Re: Soundboard Repair. . . .

Post by Michael.N. » Wed Aug 03, 2011 7:42 pm

I was thinking along the same lines until I suddenly remembered that I had already cut the outline for a different instrument!
Actually that soundboard is from your part of the world: Shanes bargain Lutz Spruce. It's lighter than my Euro stock and seems equally as stiff. It does seem a bit wooly and fibrous though. All depends on the tone . . .
Historicalguitars.

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Alexandru Marian
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Re: Soundboard Repair. . . .

Post by Alexandru Marian » Wed Aug 03, 2011 8:49 pm

Well done on the repair! Nothing more disconcerting than these pesky pin holes, and they always find their way on the spruce. In most cases it seems to be hide glue fragments, they are sharp and hard almost as glass.

I know that light weight tree, it is nice wood. I have a top in my stash, and Shane sent me a photo of the actual tree, it was *huge*! But Lutz can be a bit denser (and darker in color) so ime the density range is just the same as with Euro. The stiffness to weight was always excellent, clearly above average.
I agree on the "fibrous" aspect, it doesn't like to be chiseled when carving braces. One thing I found very interesting is that plane shavings seem to be a bit plastic, if you pull on them they stretch a little before failing, while Euro shavings are definitively more brittle.

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James Lister
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Re: Soundboard Repair. . . .

Post by James Lister » Wed Aug 03, 2011 10:21 pm

Hi Michael,

Nice repair job. I use much the same technique, but use a small "V" gouge - just taking it a touch deeper and longer for the repair piece. This has the advantage of getting a very good match in terms of shape/angle, but it's probably a bit harder to hit the grain lines exactly where you want. First few times I did this I used Titebond, then a while ago I tried it with hide glue, but to my surprise couldn't get as good a result on my test pieces.

James
James Lister, luthier, Sheffield UK

James Stephens
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Re: Soundboard Repair. . . .

Post by James Stephens » Sat Jul 08, 2017 9:48 pm

Hi Michael, I realize this is an old post but the pictures are not working for me. It has some message about 3rd party hosting in their place. Do you still have them? It would be very helpful. I'm doing some repairs on a guitar of mine and it has a spot that will require this procedure. Thanks!
James

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Michael.N.
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Re: Soundboard Repair. . . .

Post by Michael.N. » Sat Jul 08, 2017 10:26 pm

Wow, it is an old post. Where did the time go?
It's the new photobucket policy. Now they want money. Everyone seems to be complaining about it. Suddenly countless millions of forum posts aren't going to quite make the sense that they once did.
I'll try and recover the pictures and post them.
Historicalguitars.

James Stephens
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Re: Soundboard Repair. . . .

Post by James Stephens » Sat Jul 08, 2017 10:28 pm

Ah, I see. Thanks for the effort!
James

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Michael.N.
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Re: Soundboard Repair. . . .

Post by Michael.N. » Sun Jul 09, 2017 9:59 am

You do not have the required permissions to view the files attached to this post.
Historicalguitars.

James Stephens
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Re: Soundboard Repair. . . .

Post by James Stephens » Sun Jul 09, 2017 3:22 pm

Thanks for digging those up!

That's really impressive and will give me something to shoot for.
James

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