Cracked top while building

buzzsawlouie · #1 10-01-2021, 07:11 PM

This is my first attempt at building a guitar. I am at the point where I am voicing the top (torrified Sitka Spruce). When I made the initial cut of the top I left a little point on the top and bottom of the sound board thinking that it would help me properly line up the top for gluing (seen others do this on line). I determined I was able to see the centerline just fine with out these so decided to cut them off. Well when sawing a crack developed (see pics). Painful, but lesson learned.

Question I have, is this a simple fix by applying some thin CA? Or do I try Titebond? I used Titebond to join the top but I think it would be messier.

Will either effect the tonal qualities of the top, or is this ruined. I would think that it would be no different than the joint between the two top pieces.

Thanks for any advice!!
Mark

mirwa · #2 10-01-2021, 11:03 PM

I would just use titebond at his stage

Bruce Sexauer · #3 10-02-2021, 09:55 AM

I cannot see any pictures, but if a top is cracked in process anywhere but under the fingerboard extension, starting over is highly recommended.

redir · #4 10-02-2021, 10:06 AM

For a first guitar I think you are fine to reglue the top. If the crack is on the glue line then you should saw it down the center and join it again. Otherwise use titebond and clamp it.

phavriluk · #5 10-02-2021, 12:01 PM

Sounds to me like OP's got a separated glue joint, not a crack in the soundboard. I'd like to be certain that the rest of the glue joint won't fail, either. And then use some of whatever glue was used to reglue the separation. If the whole joint is weak, plane down the join edges of the panels and start over if the panels are thick enough to tolerate sanding them level again. A crack away from the joint is easier for me to respond to; I'd try to push the panels apart, push some Titebond into the crack, see that glue squeezes out, tape it up level and come back tomorrow and carry on.

JonWint · #6 10-02-2021, 12:43 PM

Crack not separation.

Glue with Titebond.

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buzzsawlouie · #7 10-02-2021, 02:35 PM

Thank you for posting the picture, i guess I didn’t link the pictures correctly. The crack is definitely not on the seam, the crack is just to the right of the seam. For what it’s worth I’m at the point where I am voicing so braces are in place.
Is it worth gluing a small cross grain tab on the back? I guess some of the crack once repaired will be glued to the heel block. Will any of this have effect on tone/sustain on top??

phavriluk · #8 10-02-2021, 02:43 PM

I can't imagine any effect whatever. Glue & cleat and on to the next adventure. This is how we learn, by experience and practice. It's a wonderful journey.

To mark my center lines of the soundboard, I drill a 1/16 hole that will disappear when the binding channel is cut. Or my pet Dremel chews a half-moon at the edge of the top.

buzzsawlouie · #9 10-02-2021, 02:48 PM

Phavriluk, great idea! Thank you and everyone else for the advice!!

redir · #10 10-02-2021, 05:34 PM

If the two halves are separated and required a lot of force to shut tight that's not good. However if it is shut tight then get some Titebond in there clamp it up and call it a day. No cleats necessary IMHO. Do you clear the center seam?

buzzsawlouie · #11 10-02-2021, 07:54 PM

Not sure what you mean by clear the seam. The joint where the two top halves are joined are intact and are fine. This is a partial crack just to the side of the center seam, extending no further than what is illustrated in the picture. I applied some Titebond in the crack and used some binding tape to hold it together. Seems to be ok now.

redir · #12 10-03-2021, 12:10 PM

I see the pic now, didn't before. You are good to go IMHO.

When you think about it, it's not too unlike joining the two top halves together. In fact the fit is arguably even better unless splinters were lost when it cracked. And many guitars have been built of 3,4 or even more piece tops. So while someone of Bruce's stature would start over, for us hobbiests we can fix stuff like that and carry on. And if done well I'm sure it will last the test of time.

Bruce Sexauer · #13 10-03-2021, 01:02 PM

I say to start over because of all the times I didn't and came to regret it. Some people refer to the top as the "Money Side". Repairing spruce is definitely more difficult to hide than most tonewoods.

PVA glues like Titebond require clamping pressure to achieve anything close to their potential strength. The crack I can now see is like to fit well, but is very difficult (impossible?) to achieve the necessary clamping press. For that reason, I would choose either HHG (it will be the least visible), or CA which will be best structurally and only visible to the trained eye, potentially. Be careful not to get any dirt in the crack.

bnjp · #14 10-03-2021, 08:10 PM

I would glue the crack with wood glue. I think your tail block will support it.

srick · #15 10-04-2021, 03:58 AM

One other alternative is to use a very sharp knife to open the crack (just a little) and use a sliver of your top wood spruce (you have the cut offs or the sound hole, I’m sure) to fill the gap. As Bruce mentioned, a small amount of CA glue carefully applied with your favorite glue dropper will do the trick. No clamping required if you have fit your sliver well.

Rick