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split repair

 
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Mat Roop
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Joined: 24 Mar 2007
Posts: 911
Location: Wyoming Ontario

PostPosted: Sun Jun 25, 2017 9:33 am    Post subject: split repair Reply with quote

So I have this idea...
a long split repair needs a multitude of cleats... they are an obvious add-on with added on weight.

post and bar splits need carved patches.... very time consuming

what would be wrong with a matching set of router style bits one convex the other concave to create a divot and a perfectly matching counter button to fit the divot?

That would create a neat fix, not add wood, and look professional.... and be quick to complete.

Thoughts? good idea or bad??
Cheers, Mat
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FiddleDoug
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Joined: 08 Sep 2007
Posts: 227
Location: Hilton, NY

PostPosted: Sun Jun 25, 2017 12:28 pm    Post subject: Bad Idea Reply with quote

Bad Idea! Generally, removing wood is worse than adding wood. Adding wood cleats is reversible, cutting divots isn't. Soundpost patches are an exception, as they deal with point pressure from the soundpost, and the hinging action created. Bass bar cracks don't require carved patches, just cleats under the bass bar. Also, every time that you cut into the plate, the cavity has endgrain that you're gluing against. Gluing to endgrain is the weakest kind of joint. As far as "looking professional", the only people that are likely to see it are other luthiers, and the general consensus might be for them to say "What hack cut divots into the plate of this instrument."
I can comment knowingly on this, because I have an instrument that someone inlaid cleats into, and when this was shown to a very fine restorer, he shook his head, and said basically that.
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Doug Wall

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Mat Roop
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Joined: 24 Mar 2007
Posts: 911
Location: Wyoming Ontario

PostPosted: Sun Jun 25, 2017 3:45 pm    Post subject: Reply with quote

Thanks Doug... good points! ... especially the end grain issue for strength.
I guess some brainwaves can be bad ideas:)
Cheers, Mat
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L P Reedy
Super Member


Joined: 02 Apr 2009
Posts: 276
Location: Brevard, NC

PostPosted: Sun Jun 25, 2017 3:56 pm    Post subject: Reply with quote

In addition to what Doug said, the weight of well-made cleats is extremely small. But possibly more important is the fact that a spinning bit cannot cut in the very center. If you don't believe that, try it. When you wet the cut you will find a little bump. Unless you were to wet both pieces and manually trim off those bumps, you would have imperfectly-fitting cleats.
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Michael Darnton
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Joined: 23 Mar 2007
Posts: 1281
Location: Chicago

PostPosted: Tue Jul 18, 2017 9:21 am    Post subject: Reply with quote

Mat, in the restoration business ANY removal of original wood is usually considered near-butchery. It's becoming more common in restoration even to avoid soundpost patches for this reason--the tendency is to glue it up skillfully and see if it sticks, and often it will.

I cringe any time I see someone inventing a fancy new tool or technique designed to remove original wood when there are so many ways to do the job well without that. Any time you put in new wood you run the risk of near-inevitability that the new wood and old are going to move at different rates at some point, that something will happen to telegraph the presence of new wood out to the surface, and that this damage will now never be able to be reversed.

I have seen some incredibly clever repairs (for their time) go horribly wrong simply because of this fact, usually when the instrument is taken to a different climate than where the repair was done.
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Mat Roop
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Joined: 24 Mar 2007
Posts: 911
Location: Wyoming Ontario

PostPosted: Tue Jul 18, 2017 10:51 am    Post subject: Reply with quote

thanks Michael... your and Doug's points came thru loud and clear. I quite dislike doing soundpost patches... so was happy to hear that a skilful reglue often works.... difficulty is getting the glue fully into the crack without expanding the crack

On that point, I keep thinking if a vacuum system could work well to draw the glue fully into the crack... sort of like what is used for windshield repairs... has anyone tried it? .. probably would work best with the top off.

Thanks again!... Mat
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Michael Darnton
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Joined: 23 Mar 2007
Posts: 1281
Location: Chicago

PostPosted: Tue Jul 18, 2017 1:59 pm    Post subject: Reply with quote

I use a suction cup to pump glue into the cracks. It keeps my dirty finger off the crack and really moves glue.
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