Official Luthiers Forum!
http://mowrystrings.luthiersforum.com/forum/

Cracks in side and top
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10137&t=50307		 Page 1 of 1
Author:  Conor_Searl [ Thu Feb 15, 2018 12:17 pm ]
Post subject:  Cracks in side and top
I've got this Seagull guitar here that looks like it took an accidental kick.

Inside, the braces look like they are all still intact, although I'm going to double check with a feeler guage to be sure, the impact which caused the crack made the wood pop up a bit, (I was able to pop it back in.) I'd be surprised if a brace didn't come a little loose.

If the bracing is fine it seems the top crack is a pretty straightforward fix which I feel comfortable with. But I'm not sure about the crack along the binding. I'm assuming gluing the separation along the binding is the same principal as any other top crack?

The crack in the side is a different story. This crack doesn't move when I press on it at all, and so it seems like it may be more of a dent then a real crack (which is what it certainly looks like), however the sides on this guitar are solid so I don't want to assume that its not going anywhere. If it is a crack, do we deal with cracks in the side the same as on the top or back of a guitar, by gluing and cleating? The other complication is that the crack in the side is right over the kerfing, so there would be no place to attach a cleat, but the kerfing should act as a cleat anyway correct?

Thanks again for your time and all the great help everyone provides.
Author:  Freeman [ Thu Feb 15, 2018 4:12 pm ]
Post subject:  Re: Cracks in side and top
The side crack looks to be right where the edge of the kerfing would be (which is a common place to break). Have you looked inside with a flashlight? Also hold the flashlight on the outside of the crack and look inside with a mirror - often you can see the light shining thru the crack.

Its pretty hard to cleat a crack like that. If it were in the middle of the side you could bend a piece of wood to match and glue it on the inside but that would be very hard next to the kerfing. I've been able to stabilize cracks like that with a piece of surgical gauze tape, after getting it stuck in place soak it in CA (which is going to be hard to do in this location) or wipe it with Titebond.

Once it is stable you can do a CA repair from the outside and then decide how you want to deal with the finish.
Author:  Barry Daniels [ Thu Feb 15, 2018 9:26 pm ]
Post subject:  Re: Cracks in side and top
It's a good idea to try to reinforce the side break after gluing it or it will possibly break again due to it being the location of a stress riser. A cleat can be shaped that will fit over the top of the kerfing and extend down the side for approximately one half inch. One cleat placed in the middle of the crack will probably be sufficient.
Author:  Conor_Searl [ Fri Feb 16, 2018 12:15 pm ]
Post subject:  Re: Cracks in side and top
Thanks guys.

What is common practice on dealing with the finish with cracks like those. Should a customer expect cracks to become invisible once repaired, or is that a further step most luthiers will tackle if the customer is willing to pay for the extra time and effort?

It seems like the one in the side will likely remain visible, unless I refinish the side which seems unnecessary from a practical perspective. But with top cracks, tite-bond has worked well to seal the crack up, but if i run my fingernail gently along the top I'll still feel the crack, and it will of course be visible. I've used CA to fix small chips in poly before with good results, achieving a nice and level surface that doesn't stand out from the surrounding finish once it's polished and buffed. However it seems to darken the spruce differently than the surrounding wood, and this top is still super white, (it's a pretty new guitar) so I'm hesitant to jump to that conclusion in such an obvious location.
Author:  B. Howard [ Sat Feb 17, 2018 9:35 am ]
Post subject:  Re: Cracks in side and top
I use linen cloth and glue to reinforce those nasty cracks along the bottom of the kerfings because as noted cleats do not work.
Author:  Conor_Searl [ Sat Feb 17, 2018 11:41 am ]
Post subject:  Re: Cracks in side and top
B. Howard wrote:
I use linen cloth and glue to reinforce those nasty cracks along the bottom of the kerfings because as noted cleats do not work.


So do you cut a strip to cover the entirety of the crack, soak it in glue and then attach it? Do you allow it to cover the kerfing a little bit, or lay it beside the kerfing? I'm picturing something similar to the linen that covers the joint on an x brace.
Author:  Freeman [ Sat Feb 17, 2018 12:26 pm ]
Post subject:  Re: Cracks in side and top
Conor_Searl wrote:
Thanks guys.

What is common practice on dealing with the finish with cracks like those. Should a customer expect cracks to become invisible once repaired, or is that a further step most luthiers will tackle if the customer is willing to pay for the extra time and effort?



Conor, Brian is by far the best person to respond to the "what do I do about the finish" issue but I think you are more like me so I'll tell you what I tell folks.

With a crack or damage to the wood, assuming I think I can do the work (and in this case I do) I would tell them that I will glue the crack and reinforce it - it should be structurally sound. I will try to fill the crack on the show side - usually with thin or medium CA and I will level it as best I can. I tell them that I cannot "fix" most modern finishes (Brian can) and I'm sure that a Seagull is a modern finish. I tell them they will be able to see the repair - that will remind them to be more careful in the future. If they are not OK with that I turn down the project.

This can change depending on the guitar and the situation - I can do reasonable repairs on lacquer finishes, altho again, I might choose to not attempt it on a valuable guitar. I also know how hard it is to match any stains or colored finishes - I'll have that discussion with the customer before I try.

As far as the crack reinforcement - as I said in my earlier post I have been using surgical gauze tape, about 1 inch wide. It is sticky so I can work it into position and stick it down along the crack. My preferred next step is to coat the tape with thin CA but that can be very awkward thru the soundhole (and all the fumes come right back in your face). If I can't get the CA on to the tape I might put some Titebond on my fingers and spread it around on the tape.

Here is a picture of an archtop that I was building and I was really worried about cracks around the F-holes. I've put the tape before I cut the holes, coated with CA, then routed the holes. I went on to bind them but I feel confident that they won't crack out

Image
Author:  Conor_Searl [ Sat Feb 17, 2018 1:57 pm ]
Post subject:  Re: Cracks in side and top
Freeman wrote:
As far as the crack reinforcement - as I said in my earlier post I have been using surgical gauze tape, about 1 inch wide. It is sticky so I can work it into position and stick it down along the crack. My preferred next step is to coat the tape with thin CA but that can be very awkward thru the soundhole (and all the fumes come right back in your face). If I can't get the CA on to the tape I might put some Titebond on my fingers and spread it around on the tape.



That makes sense Freeman, so this crack is right along the edge of the kerfing as you guessed. Will you lap the surgical tape over the kerfing slightly, or just lay it along the kerfing?

Conor
Author:  Freeman [ Sat Feb 17, 2018 4:09 pm ]
Post subject:  Re: Cracks in side and top
Conor_Searl wrote:
Freeman wrote:
As far as the crack reinforcement - as I said in my earlier post I have been using surgical gauze tape, about 1 inch wide. It is sticky so I can work it into position and stick it down along the crack. My preferred next step is to coat the tape with thin CA but that can be very awkward thru the soundhole (and all the fumes come right back in your face). If I can't get the CA on to the tape I might put some Titebond on my fingers and spread it around on the tape.



That makes sense Freeman, so this crack is right along the edge of the kerfing as you guessed. Will you lap the surgical tape over the kerfing slightly, or just lay it along the kerfing?

Conor


I would want the crack to run right down the middle of the tape so I would lap it over the kerfing.
Author:  Conor_Searl [ Mon Feb 19, 2018 6:36 pm ]
Post subject:  Re: Cracks in side and top
Freeman wrote:

With a crack or damage to the wood, assuming I think I can do the work (and in this case I do) I would tell them that I will glue the crack and reinforce it - it should be structurally sound. I will try to fill the crack on the show side - usually with thin or medium CA and I will level it as best I can. I tell them that I cannot "fix" most modern finishes (Brian can) and I'm sure that a Seagull is a modern finish. I tell them they will be able to see the repair - that will remind them to be more careful in the future. If they are not OK with that I turn down the project.


I've got the top crack glued and it looks pretty good, but I can still feel it when I run my finger over. I feel like CA would be a good option to fill and level it, so that you can't feel the crack anymore, but will it make the spruce go dark around the crack?

Conor
Author:  Freeman [ Mon Feb 19, 2018 8:18 pm ]
Post subject:  Re: Cracks in side and top
Conor_Searl wrote:
Freeman wrote:

With a crack or damage to the wood, assuming I think I can do the work (and in this case I do) I would tell them that I will glue the crack and reinforce it - it should be structurally sound. I will try to fill the crack on the show side - usually with thin or medium CA and I will level it as best I can. I tell them that I cannot "fix" most modern finishes (Brian can) and I'm sure that a Seagull is a modern finish. I tell them they will be able to see the repair - that will remind them to be more careful in the future. If they are not OK with that I turn down the project.


I've got the top crack glued and it looks pretty good, but I can still feel it when I run my finger over. I feel like CA would be a good option to fill and level it, so that you can't feel the crack anymore, but will it make the spruce go dark around the crack?

Conor


In my experience, no. You might try rubbing some wax (candle wax, paraffin) along the sides of the crack (try to get it as close as possible without getting in the crack) then wick water thin (SM #10 or equal) into it. Usually it just kind of sucks itself in and leaves very little on the surface. The wax will keep it from sticking to the finish and you can pop most of it off with a finger nail, you'll still have to scrape it with a box cutter blade and sand with fine grit paper. The trick of cutting sand paper into strips and holding it down with a finger tip while you pull it under your finger works pretty well
Author:  Conor_Searl [ Tue Feb 20, 2018 2:30 pm ]
Post subject:  Re: Cracks in side and top
Freeman wrote:
The side crack looks to be right where the edge of the kerfing would be (which is a common place to break). Have you looked inside with a flashlight? Also hold the flashlight on the outside of the crack and look inside with a mirror - often you can see the light shining thru the crack.


I can't make the side crack move at all, and no light shines through it. I don't think I'll be able to squeeze any glue into it. Do you think it will be fine if I use the surgical gauze on the inside, and then wick CA into the finish which is flaking a little bit on the side? Or is there a trick I don't know about for getting glue inside stubborn cracks?
Author:  Freeman [ Tue Feb 20, 2018 3:19 pm ]
Post subject:  Re: Cracks in side and top
Conor_Searl wrote:
Freeman wrote:
The side crack looks to be right where the edge of the kerfing would be (which is a common place to break). Have you looked inside with a flashlight? Also hold the flashlight on the outside of the crack and look inside with a mirror - often you can see the light shining thru the crack.


I can't make the side crack move at all, and no light shines through it. I don't think I'll be able to squeeze any glue into it. Do you think it will be fine if I use the surgical gauze on the inside, and then wick CA into the finish which is flaking a little bit on the side? Or is there a trick I don't know about for getting glue inside stubborn cracks?


I think you will be fine putting the tape inside and coating it with some sort of glue, thin CA would be best but probably hard to do. Then wick the thin CA right along the crack as I discussed above - use one of the whip tips that StewMac includes or a very fine pipette and just run a very fine bead right along the crack. You might have to do several applications. Scrape, sand and polish.

One comment, I have become very sensitized to CA glue and the accelerator. If I don't wear a full NIOSH respirator I have a pretty severe reaction.
Author:  Conor_Searl [ Tue Feb 20, 2018 3:30 pm ]
Post subject:  Re: Cracks in side and top
Thanks Freeman, that's what my gut was saying, but thought it best not to assume.

I'll keep that in mind about your sensitization to CA as well.
Author:  Conor_Searl [ Wed Feb 21, 2018 1:08 pm ]
Post subject:  Re: Cracks in side and top
B. Howard wrote:
I use linen cloth and glue to reinforce those nasty cracks along the bottom of the kerfings because as noted cleats do not work.



Any tips Brian, on getting an arm that far back into the body?
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/