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Very Unpleasant Surprise.


NotYou
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:D

This is my first post here.

I left my shop for a couple days while working on the body of a guitar. I live in Denver, so the air is very dry and it got cold when I left, which means it got even dryer. When i came back to the shop I found a crack going right up the middle of the body between the pickup cavities. :D

I made that part thin on purpose to resonate better. It worked great until this happened. There was a small chip on the top of the bridge cavity (it's in the picture) and that seemed to have been the trigger.

The wood is jatoba, which is VERY hard and chips and splinters a lot. I wasn't expecting this crack though.

To fix it, I'm going to lay in a stripe of ebony and black and white ebony, which will match the fretboard and fretboard binding. So, all isn't lost. I was working on a way to fix that chip and I guess this actually solves the problem.

Anyone else have any issues like this?

http://img516.imageshack.us/img516/8393/img0028an9.jpg

http://img516.imageshack.us/img516/5767/img0029sj6.jpg

<edit: images exceed maximum allowable size of 640 x 480. one pic per post please!>

Edited by Prostheta
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I made that part thin on purpose to resonate better.

?????

is it a solid body?

you want the piece between the pickups to resonate better?

sorry, but I don`t understand.

about the fix:

you don´t have to inlay anything in there.

just glue some other wood underneath it, and fill the gap with glue+wood dust, I think it will be invisible, look like a grain line. and nobody will be able to tell that it was repaired.

Edited by Hector
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I made that part thin on purpose to resonate better.

?????

is it a solid body?

you want the piece between the pickups to resonate better?

sorry, but I don`t understand.

about the fix:

you don´t have to inlay anything in there.

just glue some other wood underneath it, and fill the gap with glue+wood dust, I think it will be invisible, look like a grain line. and nobody will be able to tell that it was repaired.

It's a chambered body. It's almost completely hollow, though. Jatoba is a heavy wood, so I wanted to drop as much weight as I could. It still weighs as much or more than a Les Paul body.

Making that part thinner made it MUCH louder. It won't make a huge difference plugged in, but enough to be noticeable.

I'm never working with jatoba again, unless a customer requests it and is willing to pay extra for the hassle. Carving that wood is like carving stone. It's beautiful though, so it should be worth it. This piece is full of birds eyes and has a nice contrast in the grain.

I don't recommend trying to build with it though, unless you can CNC it. It's a great looking and sounding tonewood, but it might not be worth tearing your hair out for it.

Edited by NotYou
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I'm definitely not repairing the crack. I wouldn't feel right selling it with a flaw like that. Before it happened I was debating putting an inlay there. Adding ebony and glueing it should strengthen it more too.

I'll post pictures when it's all done. I think it's going to look great.

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Half the skill of a good woodworker is fixing mistakes. If you can repair the crack and it looks like you didn't repair it then you should be fine.

I moved to northern CO (front range) about 4 months ago from the northeast so I see humidity can be an issue here. On the other hand it gives you 365 days out of the year to build since you do not get the heavy northeast humidity problems in an non climate controlled shop. But the same rules apply here as in the northeast, you cannot use wood until it has a chance to acclimate to your shop and the season. If you are lucky enough to live in your own house and your shop is heated and cooled; add a humidifier to the system for the extra dry winter months.

If you are in a garage or unheated shop use shellac to help slow the humidity changes on end grain like you experienced. Use it in the cavity not over the entire guitar. But the best cure is making sure the wood is properly seasoned and acclimated before use. Patience is a requirement here.

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well, heres a word of advice then

"i fought the flaw, and the flaw won"

if your going to sell it still, dont bother inlaying over the crack (essentially hiding it :D), since that is no better than filling it (which is invisible); with standards such as that, that bodys toast, sorry man. you could run the top of the body through a bandsaw and put sometype of top wood on it, and rerout the cavities....

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Half the skill of a good woodworker is fixing mistakes. If you can repair the crack and it looks like you didn't repair it then you should be fine.

I moved to northern CO (front range) about 4 months ago from the northeast so I see humidity can be an issue here. On the other hand it gives you 365 days out of the year to build since you do not get the heavy northeast humidity problems in an non climate controlled shop. But the same rules apply here as in the northeast, you cannot use wood until it has a chance to acclimate to your shop and the season. If you are lucky enough to live in your own house and your shop is heated and cooled; add a humidifier to the system for the extra dry winter months.

If you are in a garage or unheated shop use shellac to help slow the humidity changes on end grain like you experienced. Use it in the cavity not over the entire guitar. But the best cure is making sure the wood is properly seasoned and acclimated before use. Patience is a requirement here.

It's funny you say that. I just moved here too and I'm originally from the Northeast (Ohio, but most recently NYC)

I actually did shellac the cavities. If you look real close you can see it shimmering a little in my crappy pictures. My shop is heated all the time, which makes the temperature steady, but it also dries the air significantly, as I now see.

This mistake is getting fixed, no doubt, but I'm not just filling in the crack like everyone seems to think I should. I'd be pretty pissed if I bought a guitar and later found a repaired crack right up the middle.

Technically, I'm not inlaying either. I'm completely removing a section of that piece, a little more than half an inch, and I'm inserting a new ebony piece. I already have a whole "emergency surgery" planned. This way, it won't look like a fixed mistake. There will be no crack to maybe see and no evidence at all of anything gone wrong.

This isn't covering up a mistake, I'm trying to %100 fix it. As soon as it's all glued in and sanded I'll post pictures to show how it went.

Edited by NotYou
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if I can make a repair so good that`ll be invisible, then to me, it´s not a mistake.

sh*t happens, woods crack, that happens a lot in any woodshop.

i don`t think putting glue in a crack and closing it is a repair at all. it´s just what we all do everytime something like this happens.

a lot of times, dealing with thin acoustic sides, i had little cracks. but none of the wood is gone, it´s still there, just put glue and pressure and everything is fine again.

a router tearout is another story, you have to fill the gaps etc...

sorry man, but it seems to me that your standards are set way too high. much more than every other builder around here.

and one other good point is that luthery is all about dealing with this kind of thing, it makes you think of ways to do something, how to make it easier, how to make it faster, how to make it better, how to fix little things like this and a lot of times, how to fix something that seems impossible to fix.

it´s all good!

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i filled a small crack on one of my fretboards (nut side, about .5" long all the way through) and i loved the board so much i decided to try and do the glue repair. i smothered it with titebond (before it was radiused and whatnot) and clamped with a little more than normal pressure, once it was all radiused on one of my jigs i couldnt find ANY evidence of a crack being there previously.

plus the glue bonds stronger than the wood :D so technically if you were ever to do a "repair" of that sorts you would be strengthening the area, rather than weakening.

i wouldnt be able to justify "repairing" a top on an acoustic guitar, or a guitar where the top is used to amplify vibrations (arch top, or whatnot) if i were as concerned as you were, i would cut off the entire top, and simply glue a new one on, but then again

my standards for the wood i use are much lower than my tolerances, being as wood is an organic substance that moves and shifts, and is bound to have imperfections.

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I agree about glue making things stronger. I actually just said that exact same thing on another thread a couple hours ago.

I also agree that wood should look natural, that's why I love this piece so much. If you look at the pictures you can huge separations in the grain, which I think is gorgeous.

I think you guys convinced me to at least try filling the crack. If it doesn't work, I'll continue with my plan of using the ebony. No loss there.

I don't think it will work on this particular crack though. It wasn't hit by something and cracked or anything like that. It cracked from drying, which means the sides of the crack pulled away from each other. The gap is a little too large to fix convincingly.

I've filled cracks before, but I think this one is just too wide. I'll try it though.

I agree with Hector that luthiers have to be extremely clever and work with their problems. That's why I'm not tossing this out.

And, yeah, my standards are very high, but I'm proud of that. I went to a brutal art school for five years. After that I'm very particular about what I put my name on.

Whatever happens, I'll post pictures.

BTW, I'm glad I signed up on this forum. Everyone is very honest about their responses. I think that's a great thing.

Edited by NotYou
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so now it´s the time to tell you why the piece cracked.

wood expands and contracts with humidity. if you take a acoustic guitar for example, and glue the top (unradiused, not domed, or anything. just flat) when the humidity is 80%, the dimensions of the wood are bigger than it would be at 40%.

so what happens is that you secured the borders of your wood to the sides, and as the humidity drops, the piece starts to shrink (in a very very small way), but the piece is glued to the sides, and not going anywhere. here is where your wood cracks. imagine yourself pulling a piece of paper with both hands. it´ll rip at some point. it´s the same with the wood, imagine that you are holding the paper very steady and pulling it tightly, if the paper could shrink, it would rip.

in my city, we get humidity as low as 13% in the dry season, you can guess when it´s the time I do more repairs to acoustic guitars. a domed top, will allow the top to expand and shrink some more (convex when it`s more humid, and getting almost flat or even concave when it´s too dry).

my advice? whenever you´re gluing wood like this, do it in a humidity controlled room. 43% is my choice. lower if its possible, but never more than that.

hope i'm being clear, english is not my first language.

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It's funny you say that. I just moved here too and I'm originally from the Northeast (Ohio, but most recently NYC)

Technically, I'm not inlaying either. I'm completely removing a section of that piece, a little more than half an inch, and I'm inserting a new ebony piece. I already have a whole "emergency surgery" planned. This way, it won't look like a fixed mistake. There will be no crack to maybe see and no evidence at all of anything gone wrong.

This isn't covering up a mistake, I'm trying to %100 fix it. As soon as it's all glued in and sanded I'll post pictures to show how it went.

OK I grew up in NYC weird. But back to the problem. If you didnt undercut the body between the two pickups the crack probably would not have occured. I think this is what Hector is talking about, Maybe? More wood would have resisted the pulling forces as it dried.

Adding a humidifer to your hot air heating system should keep the moisture in your shop up when you are heating the house. A $200 plus fix.

I suggest a wedge as a repair. If you match up the pattern you should be ok. The wedge will give you a way to secure the piece while it dries, then you can plane it flat on the top and probably file the underside.

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I agree with both of you guys. That middle part was thinner than the rest of the wood. I actually made it arch into that piece to make it stronger, which seemed to work. I didn't take into consideration that, if it shrinks, that's going to be a significantly weaker spot and crack, which it did.

I plan supporting the piece I'm adding from underneath to help me glue and clamp it properly.

The piece I'm adding will be slightly larger on top, just in case, then I'll sand and plane it down.

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I had a similar issue on my second build. I believe one of the clamps slipped when I was gluing the second (right side) part of the top down. I didn't have enough clamps to glue both pieces down at the same time, so it had to be done this way.

th_8string15.jpg

(click to enlarge)

So I routed out 5/8" of material straight down the center and glued in a piece of QS Wenge. The fix isn't noticeable unless you're within a few inches of the bass. Even then, it looks like the center stripe was intentional.

8-String%20Fretted%2017.jpg

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I finally got back into the shop today.

It's warmed up here in Denver, which means the humidity is a touch higher and the heat's off, which means it's not nearly as dry. The sides of the crack are closer than they were when I took the picture, so just fixing the crack might just work now.

I glued it and all that and I'll see tomorrow how it went. If it still looks like a crack, I'll go ahead with my other plan. I already have the pieces glued and clamped (it'll be striped: B&W ebony, ebony, B&W ebony). They'll just need cut and sanded down to thickness.

@ akvguitars

There should be something like that here. I would love to meet with other luthiers. Most of us work alone, so we don't get to talk shop much.

I found a webpage a while back that lists all the luthiers in Colorado. At least the ones that registered there.

http://www.coloradoluthiers.org/

I haven't put myself on there or looked at it much yet. I've only lived here since this summer.

Edited by NotYou
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It seems to have worked. I'm waiting a bit to see how it holds up though.

http://img373.imageshack.us/img373/7362/img0034mx3.jpg

http://img116.imageshack.us/img116/7909/img0036hk0.jpg

This the piece I made that I'm thinking of implanting:

http://img399.imageshack.us/img399/6545/img0033jx5.jpg

Edited by NotYou
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It's warmed up here in Denver, which means the humidity is a touch higher and the heat's off, which means it's not nearly as dry. The sides of the crack are closer than they were when I took the picture, so just fixing the crack might just work now.

if the humidity is high and the sides of the crack are closer than they were before, and you glued them back together, can you guess what will happen when the humidity gets low again?? the wood will shrink again, and maybe crack one more time!

keeping the humidity up is not the way to work this out. you should glue it when it´s low, and fill the gap. then you don´t have to worry about it anymore.

Edited by Hector
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Filling the gap would look horrible. I realize the humidity will go down again and probably very soon. That's why I'm waiting before I settle with it. I'd be surprised if it doesn't open up again.

I like the way that ebony piece looks on it too. I'll probably add it no matter what. It'll match the fretboard and binding perfectly.

Fixing the crack was more of an experiment than anything.

Edited by NotYou
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