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#1
11-04-2019, 02:58 PM
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Partial crack in the top
Hello, I have an old classic acoustic with solid spruce top. Itīs got some cracks in the top. None of them all through the wood. The biggest is from approximately the middle of the saddle to the protective purfling.
The matter is the crack has slightly raised edges. Like when a plough has been run through the soil, sorry but I canīt find any better comparison. How could it be adressed, please? Is this a humid crack? Caused by too high humidity? Regards 
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#2
11-04-2019, 03:12 PM
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Cracks are typically caused from lack of humidity not too much. Something like that can be difficult to repair. I think what you are describing is a crack on the center seam? From the center of the bridge to the tail block? If it's a fan braced guitar then there might be a brace that runs right along that crack in which case you cannot simply clamp it back together. It's probably best to take it to a good repair tech to analyses it.
If you provide pics it might help too. I know what you mean by the plowed up surface, the wood or finish may have curled right there at the location of the edge of the crack. To see if it is indeed a crack through the wood in a dark room you can stick a bright light source inside the guitar and see if any of it comes through. If it is just a finish crack then it can be filled, sanded, and buffed out.
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#3
11-04-2019, 03:59 PM
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#4
11-04-2019, 05:57 PM
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I have never seen a crack in the body of an acoustic guitar that doesn't go all the way through. I believe it is physically impossible, due to the nature of thin, brittle wood. Cracks are less visible inside, due to the unfinished surface and poor viewing conditions.
A raised crack can be difficult to deal with. One way is to install a continuous cross-grain cleat, similar to the back seam reinforcement. It would have to be securely clamped in place in order to press the top flat. This usually requires some tools and planning, especially in the area south of the bridge.
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#5
11-06-2019, 10:33 AM
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Hi, thanks for your replies. I appreciate the advice or reminder to put a light inside and yes John, of course you are right, it is cracked all through.
I moisturise the guitar to close up the cracks. I have an idea to make support to put inside then clamp from the outside and maybe press the cracks together with clamps on the sides too. Do I need to use tonewood for cleats or if I put it this way; if I donīt use tonewoos cleats is that of any importance for the result, please? Kind regards
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#6
11-06-2019, 01:36 PM
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I would put this in the advanced category of guitar repair and is not really a DIY kind of thing but if it's a relatively cheap guitar and you don't care then...Since you could see light coming through then it's probably not the case but, make sure to check that the crack doesn't run right along the center of one of the fan braces. If it does then clamping that back together probably won't work. If it runs right along the side that presents another issue.
You will need to do two things here, one is to clamp the two halves of the crack flat so that the two planes that make up each half of the crack come together perfectly and two, clamp the top edge of the lower boughts so as to clamp the crack shut. You don't want to use a tremendous amount of pressure here. Seeing some squeeze out in the crack is always a good thing. If the crack extends under the bridge then you will need to remove the bridge. To flatten the two halves I use some sort of caul protected by wax paper or something so as not to glue it to the inside of the guitar and a piece of plexiglass on the top so I can see whats going on when everything is clamping together. I have clamps long enough to extend to every corner of the inside of the guitar. But if you don't then like you said you could create some sort of 'go bar' system on the inside but that's going to be tricky too. To squeeze the crack together I make cork lined cauls by tracing the lower bought on a block like a 2x4 and using a bandsaw to make the outline. Always do a dry run first, in fact do it twice maybe. Use Titebond glue and clamp it for at least 12 hours. Once you clean it all up it's best to use spruce for your cleats inside the guitar. Typically we make them in a diamond shape with the long points of the diamond going in line with the crack and the grain of the cleats perpendicular. Magnets are wonderful for aligning and clamping cleats.
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#7
11-07-2019, 02:18 AM
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Thank you so much for your response. Iīve made some repairs to a vintage ukulele before (neck reset). Bur suppose this might be more advanced. The guitar and the ukulele are also completely different instruments.
From your response I draw the conclusion that the choice of wood is of less importance as long as it is spruce, i.e. the matter of tonewood or just any matured spruce is a no question, right? Best regards
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#8
11-07-2019, 07:32 AM
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#9
11-08-2019, 03:23 AM
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I make my own patches and these work well for me, the patch which is 6/10mm wide, The centre 6mm width is 1.2mm thick and tapers out to 0 at the 10mm width.
Low profile and plenty of strength Steve
__________________
Cole Clark Fat Lady Gretsch Electromatic Martin CEO7 Maton Messiah Taylor 814CE
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#10
11-13-2019, 04:45 AM
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So, I went to both the violin maker and the luthier in the city. By the luthier I was told that "This kind of cracks we would fill with glue. But no cleating. The bracing will keep the instrument stable and together." The last sentence he stressed twice.
The violin maker was very kind and told me that: "guitars are difficult", but gave me small pieces of tonal spruce that could eventually be used for cleats.
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#11
11-13-2019, 09:39 AM
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Well hopefully the Luthier at least looked inside the guitar. I've seen a lot of vintage guitars with cracks repaired with saw dust and hide glue. Seems like an old school method of repair. He's probably right that the bracing will hold everything together but there are better ways to fix it imho. As I mentioned before if it is a classical guitar with the fan brace running right down the length of the crack then it essentially is cleated and so you would not do that.
Pics would help but from the sound of it what I would probably do is first make sure the guitar is hydrated. Then I would clamp it up dry to see if the crack comes together tightly. If it does then I would glue it shut and cleat it. If not then the other option would be to splint it.
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#12
11-18-2019, 11:47 AM
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https://www.dropbox.com/s/nmuhmui2os...01343.jpg?dl=0
https://www.dropbox.com/s/4rix8o8ujt...01344.jpg?dl=0 https://www.dropbox.com/s/f3xy3sm0sm...01348.jpg?dl=0 There is also a crack that runs in parallel to the fretboard about one cm from it. But it is pretty closed up. The saddle isnīt completely attached to the top. At both sides of the crack there is a gap between the top and the saddle. At the gap it is attached to the top. Regards Last edited by Henning; 11-18-2019 at 11:26 PM. Reason: Completement
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#13
11-18-2019, 03:37 PM
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By the looks of the second pic it's not the center seam so there is probably no brace running right along it but there probably is one crossing it depending on how the guitar was braced. It also looks like it extends right across the bridge. So there are a lot of potential issues there. You would probably have to remove the bridge to get it done right. If there is a bridge patch, some classical guitars don't have them, then it makes it potentially more difficult.
If the crack shows movement then it should be dealt with. If it comes together easily then you could glue and cleat it. If not then a splint might be the better option especially if it crosses a bridge plate and braces. Again it's hard to say without seeing it. You might want to take it to another guitar tech or luthier for a second opinion. It's also quite possible that if you put a set of strings on it you can get away with playing it like that for years.
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#14
11-18-2019, 06:00 PM
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Yep, find a good local luthier not a guitar tech, I suspect its lattice braced and that would contribute to that long crack.
Sight unseen, check for loose braces, glue and cleat exposed crack, job done Steve
__________________
Cole Clark Fat Lady Gretsch Electromatic Martin CEO7 Maton Messiah Taylor 814CE
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#15
11-19-2019, 10:31 AM
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Thank you for the answers. The top looks fine. Itīs straight, no dipping into the soundhole. The bracing is a traditional sun feather and no lattice!
It is built in the 1960s or perhaps early 70s. You can see the bracing of the top here. I donīt have equipment for reattaching the saddle. I donīt intend to get that in the first place either. Regards
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