Official Luthiers Forum!
http://w-ww.luthiersforum.com/forum/

Crack in top found while finishing.
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=55788		 Page 1 of 1
Author:  Colin North [ Tue Jul 25, 2023 10:06 am ]
Post subject:  Crack in top found while finishing.
Found what I think is a slightly depressed crack in the upper bout above the UTB. gaah gaah gaah
I suspect this happened when clamping it in my holder for sanding the pore fill on the sides, got to fix that with thicker/lighter foam, no space for a Troji.
There seems to be no gap at all and the area is pretty much flat.
It's about 3/4" away from the neck block, which flares slightly (masked off area is for fretboard)
My first though is to glue a long cleat about 1.5 - 2mm thick behind it, slightly (say 5 degrees) on the diagonal, maybe an inch wide and clamp everything flat to fix it and ensure the is flat.
Any help/alternative suggestions greatly appreciated.

Image

Image

Sent from my moto g(50) using Tapatalk
Author:  jfmckenna [ Tue Jul 25, 2023 10:55 am ]
Post subject:  Re: Crack in top found while finishing.
That's so tight it's hard to see. I'd glue it shut and call it a day. The FB will be all the 'cleat' you need from the top side.
Author:  Ken Nagy [ Tue Jul 25, 2023 10:59 am ]
Post subject:  Re: Crack in top found while finishing.
The cleat may give you peace of mind. I can't imagine the crack ever going past the liner or the UTB. When will it have that much stress again? The liner and the UTB will act just like the cleat you want to add.

But then, I don't worry about anything.

I have a similar type of crack; from clamping. The clamp slipped too far past the edge. I HEARD it! But it was very hard to see until varnish! I put CA on it, but I could not get it to move at all there, it is very stiff. No way to get to it to even attempt a cleat. I used a bar clamp instead of the spool clamps I made up specifically for gluing tops and back. My fault.

Battle scar.

I see that I should take PHOTOS of all my work so I can see the flaws that I don't notice at all! Wow.

Attachment:
IMG_1375.jpg
Author:  Colin North [ Tue Jul 25, 2023 11:05 am ]
Post subject:  Re: Crack in top found while finishing.
jfmckenna wrote:
That's so tight it's hard to see. I'd glue it shut and call it a day. The FB will be all the 'cleat' you need from the top side.

If only!
FB doesn't cover the cracked area duh
Author:  Colin North [ Tue Jul 25, 2023 11:10 am ]
Post subject:  Re: Crack in top found while finishing.
Ken Nagy wrote:
The cleat may give you peace of mind. I can't imagine the crack ever going past the liner or the UTB. When will it have that much stress again? The liner and the UTB will act just like the cleat you want to add.

But then, I don't worry about anything.

I have a similar type of crack; from clamping. The clamp slipped too far past the edge. I HEARD it! But it was very hard to see until varnish! I put CA on it, but I could not get it to move at all there, it is very stiff. No way to get to it to even attempt a cleat. I used a bar clamp instead of the spool clamps I made up specifically for gluing tops and back. My fault.

Battle scar.

I see that I should take PHOTOS of all my work so I can see the flaws that I don't notice at all! Wow.

Attachment:
IMG_1375.jpg

Trouble is the top is slightly depressed at the crack as I mentioned in the OP.
I didn't see it, even under Naptha, or the shellac which I sealed the spruce with before getting a couple of coats of finish on, it becomes obvious.
Author:  phavriluk [ Tue Jul 25, 2023 12:12 pm ]
Post subject:  Re: Crack in top found while finishing.
I think OP will sleep better if a known flaw is resolved before proceeding farther. I sure would if this problem was mine. What's inside that could impede gluing and cleating?
Author:  Colin North [ Tue Jul 25, 2023 1:09 pm ]
Post subject:  Re: Crack in top found while finishing.
phavriluk wrote:
I think OP will sleep better if a known flaw is resolved before proceeding farther. I sure would if this problem was mine. What's inside that could impede gluing and cleating?
Exactly.
Pic below, with small rare earth magnets positioned (knew they'd come in handy some day) n the corners against the fretboard extension (trapeziod shaped) under the soundboard - where it meets the linings at top, UTB at the bottom one The crack is just maybe visible, and runs straight up from the middle of the bottom 3mm diameter magnet.

The FB. extension support edge runs to the left side of the magnets on the diagonal.

Image

Sent from my moto g(50) using Tapatalk
Author:  jfmckenna [ Tue Jul 25, 2023 1:15 pm ]
Post subject:  Re: Crack in top found while finishing.
Colin North wrote:
jfmckenna wrote:
That's so tight it's hard to see. I'd glue it shut and call it a day. The FB will be all the 'cleat' you need from the top side.

If only!
FB doesn't cover the cracked area duh


Oh! Well I still don't see it which probably means the crack is real tight. When ya think about it we join a top and brace it leaving long open spaces without cleats in them between the braces so is that really much different?

Did you wick some naphtha in there to see if it goes all the way through?
Author:  bobgramann [ Tue Jul 25, 2023 1:21 pm ]
Post subject:  Re: Crack in top found while finishing.
I’ve had that happen more than once with tops and backs. Each time, it was in one that wa either already sold or going to be. I replaced the plate each time. I just couldn’t let one go out when I knew of the flaw.
Author:  Colin North [ Tue Jul 25, 2023 1:26 pm ]
Post subject:  Re: Crack in top found while finishing.
jfmckenna wrote:
Colin North wrote:
jfmckenna wrote:
That's so tight it's hard to see. I'd glue it shut and call it a day. The FB will be all the 'cleat' you need from the top side.

If only!
FB doesn't cover the cracked area duh


Oh! Well I still don't ............ally much different?

Did you wick some naphtha in there to see if it goes all the way through?


No, the 2 thou or so of finish might stop that as it was sprayed on just before I found the crack.
Anyway, I can see the top is slightly depressed along each side of the crack in the reflection on the finish, it is cracked.
Author:  Colin North [ Tue Jul 25, 2023 1:33 pm ]
Post subject:  Re: Crack in top found while finishing.
bobgramann wrote:
I’ve had that happen more than once with tops and backs. Each time, it was in one that was either already sold or going to be. I replaced the plate each time. I just couldn’t let one go out when I knew of the flaw.

I hear that, this one's going to a friend, and there's absolutely no way it's spreading. There's laminated linings north + nearly an inch of UTB / wedge south of the crack.
Author:  jfmckenna [ Tue Jul 25, 2023 6:49 pm ]
Post subject:  Re: Crack in top found while finishing.
I understand the replacing the top thing and I have done it on many occasions but wood is wood too. I recently noticed a crack in Old Growth BRW after finishing too and I fixed it. Not going to toss a $3k set of wood because of that. And again, how is it any different than joining a top? In fact a 'natural' crack repaired is probably even stronger than a top joint. Just a bit of food for thought. There are only so many trees in the forest. And again, I would not consider it if I thought it would make the instrument less quality, imho it doesn't (within reason of course).
Author:  Clay S. [ Tue Jul 25, 2023 8:40 pm ]
Post subject:  Re: Crack in top found while finishing.
If it cracked because of human error (misplaced clamp) I would just glue it up and make it as inconspicuous as possible (high clarity hide glue). Possibly a couple of diamond cleats on the inside or maybe a piece of back graft material if I thought it needed reinforcement. I wouldn't sweat it too much - as JF said it's really no different than an unreinforced center seam.
If people realized how much of the "new" stuff they buy has been reworked and repaired from accidents and shipping damage they would probably just shop the second hand stores. One of the touch up techs used to convince customers to let him repair the piece they had, by telling them the replacement might be in worse condition.
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/