Repairing / Hiding a Top Defect

Construction and repair of Classical Guitar and related instruments
CarlJones6108
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Repairing / Hiding a Top Defect

Post by CarlJones6108 » Wed Apr 12, 2017 5:10 pm

During the process of trimming the top flush to the body in preparation for binding, my chisel slipped and I put a nice cut right into the top. I did a quick repair with a splinter of WRC from the edge and some fine dust from sanding that same piece of wood, and a drop of CA glue. After some scraping and sanding, I'm not too crazy about the repair; photo attached. I'm thinking now of perhaps adding an extra ring around the rosette to remove the defect and cover the area, maybe as much as 3/8" wide, with a ring of plain black walnut, same as the back and sides. Any thoughts on this or alternative methods to fix this spot?

caj
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Tom Wimsatt
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Re: Repairing / Hiding a Top Defect

Post by Tom Wimsatt » Wed Apr 12, 2017 5:19 pm

Perhaps you could cut a "dutchman" patch of similar grain?

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Brian McCombs
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Re: Repairing / Hiding a Top Defect

Post by Brian McCombs » Wed Apr 12, 2017 9:37 pm

I think attempting to cut in another rosette channel at this stage would be harder and invite additional modes of possible failure. It would be easier try and patch it with similar wood of which you probably have....I can't tell exactly where geographically this damage is. Are you sure your not making a flamenco guitar? I mean a golpeador would hide that quite proper.

CarlJones6108
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Re: Repairing / Hiding a Top Defect

Post by CarlJones6108 » Thu Apr 13, 2017 2:44 am

I do save my scraps of WRC, so I expect I could match it readily enough. It's not a flemenco, it's a basic, traditional classical, so I don't think a flamenco-style golpeador or an American folk pick guard would be appropriate, although that would be a good, easy solution. The ding is on the treble side, just at the lower right of the soundhole. I agree that trying to add more rosette would be very risky; my concern with the patch would be that it would be highly visible, even if I match the grain exactly.

If I did that (patch), would it be possible to touch it up and hide the join lines, maybe after the first sealer application?

gjo
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Re: Repairing / Hiding a Top Defect

Post by gjo » Thu Apr 13, 2017 7:08 am

Do not try to "repair" it, it will be visible whatever you do. Inlay something fancy and it will be looking "good" or at least "interesting". Repair it and it will look "repaired".

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Michael.N.
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Re: Repairing / Hiding a Top Defect

Post by Michael.N. » Thu Apr 13, 2017 7:47 am

This shows the method of repairing such a defect. Don't even attempt to try it on the actual soundboard until you can do 5 or 6 successful attempts on off cuts. That could mean 15 or more attempts altogether. Eventually you get proficient at these things. If you can line up the grain lines so much the better. The eye tends to follow grain lines but picks up any disturbance or misalignment in them. It is possible to get these patches looking near invisible, such that you have to very carefully look for them to find the patch. If you have the off cuts from the soundboard you've already got a big advantage, just bear in mind the reflection and don't flip the piece for the patch. Cedar is a touch easier to disguise than spruce. If your attempts at a patch fails then you can always switch to the inlay route.

viewtopic.php?t=61226

Oh and don't use CA to glue the patch. At least with Hide glue it's a simple matter to remove the patch and try again. CA is too much of a one way street.
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Andy Culpepper
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Re: Repairing / Hiding a Top Defect

Post by Andy Culpepper » Fri Apr 14, 2017 12:10 am

I would definitely not use thin CA glue, in fact I never get the stuff near softwoods as it wicks into the soft grain and causes discoloration under finish.
Very nice tutorial there Michael N. This one looks trickier as it spans multiple grain lines though?
I think a little decorative inlay mirrored on both sides is probably what I would do.

CarlJones6108
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Re: Repairing / Hiding a Top Defect

Post by CarlJones6108 » Fri Apr 14, 2017 4:15 am

Nice tutorial, and his patch did exceptionally well. I think I will try this approach, with some practice runs as suggested, and if that doesn't work well I'll do a small decorative inlay over that spot.

Thanks for the suggestions.

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Michael.N.
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Re: Repairing / Hiding a Top Defect

Post by Michael.N. » Fri Apr 14, 2017 7:13 am

Andy Culpepper wrote:I would definitely not use thin CA glue, in fact I never get the stuff near softwoods as it wicks into the soft grain and causes discoloration under finish.
Very nice tutorial there Michael N. This one looks trickier as it spans multiple grain lines though?
I think a little decorative inlay mirrored on both sides is probably what I would do.
The one that I showed crossed grain lines, just not as many. If it means doing two patches side by side or overlapping, so be it. I've done these type of patches many times over the years. They are always superior to any type of filler and I've messed around with fillers for endless hours trying to get a good match.
There's no excuse, unless someone doesn't want to pay the money for the amount of time taken to do high quality restoration work. Unfortunately that happens even with relatively expensive guitars, so the filler comes out. In this particular case money doesn't apply, it's more about pride and saving a soundboard. Someone with a restorers mind set will see it as a challenge, the challenge being to make the defect disappear. Most guitar makers who never do this type of work see it as a defect that's fatally flawed, so in the bin it goes. This repair is relatively straight forward in comparison to some. If an off cut of the original material isn't available then the difficulty shoots up by many factors.
Certainly not mine but here's an example of just what is possible with this worm eaten violin.

Image

Image
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CarlJones6108
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Re: Repairing / Hiding a Top Defect

Post by CarlJones6108 » Wed Apr 19, 2017 4:30 am

Most encouraging, thanks. Today I worked two or three hours at patching a spot 3/8 x 5/8 in scrap material. I could cut out a nice area that size and inlay a fresh piece, carefully cutting a downward slant on the edges so that the inlay fit well when pressed in, and the long edges looked good; the short ones, however (the edges 90 degrees to the grain lines), were always too apparent. Reviewing the tutorial, I see that the "rugby/football" shape of the cutout sort of ducks that issue. I'm going to take another run at this, maybe with two or more footballs side-by-side to cover the width of the ding.

The violin repair is amazing.

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Michael.N.
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Re: Repairing / Hiding a Top Defect

Post by Michael.N. » Wed Apr 19, 2017 6:48 am

Not sure why you state that it ducks the issue. Can you see any obvious or apparent 'joints' in my example? The patch should be larger than the recess and of course you do need to get a good fit. Even if you can't get it to that standard you should be able to make a huge improvement on the sawdust filler.
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CarlJones6108
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Re: Repairing / Hiding a Top Defect

Post by CarlJones6108 » Fri Apr 21, 2017 3:32 am

No, that's what I mean. The issue I was referring to was the apparent joint line, and the shape of the cutout makes it much less apparent. I've been working at this today with the oblong patching technique. I'm right properly amazed at the difference. See photo
IMG_20170420_181758672 - Patch Practice a.jpg
On the right are two attempts using rectangular patches, numbered 4 and 5. While they fit well enough, they are quite obvious. So today I did number 6, outlined in pencil, using two of the football-shaped patches side-by-side. It doesn't have the abrupt joint line crossing the grain lines. This might yet be a bit crude, and I'm going to practice at it some more, but I'm much more confident now that a patch like this will do the job.
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Michael.N.
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Re: Repairing / Hiding a Top Defect

Post by Michael.N. » Fri Apr 21, 2017 5:14 am

Your patches aren't quite fitting well enough. Make sure your scalpel is extremely sharp, you need very clean edges. The patches should be oversized when you glue them in, clamp the patches.
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