Split in soundboard - can I do anything about this ?

[Dave Olds]

Bit of a set back with #3.

Tonight I noticed there is a split in the soundboard, which has only just appeared. It was definitely not there 2 nights ago !! The box has been closed up for approx 5 weeks and the soundboard had been in the workshop for about 12 months before that. I do not have a humidity controlled environment, but I am not at all convinced that this is due to humidity changes anyway. Prior to joining the top, there was a split in one of the plates, roughly along the same line as where this has appeared. When I traced the position of the top on the plates I made sure that I cleared the split piece by at least 1 cm - but maybe there was a structural fault along this line.

Anyway - the split is currently very thin - but who knows what will happen from here. It runs for about 4 cm - from near the heel block through to around where the lower of the two tone bars crosses. When you tap on the guitar you hear no difference in sound around where the split is.

Is there anything I can do about this - or is it firewood !! Would CA glue be any use - I guess the issue of staining would be a problem. It would be very hard to get a patch on the inside due to the position - and I am not sure what effect that would have anyway.

I'm totally pissed at the moment - as the guitar was coming along nicely - but I guess this is what we learn from huh !!

[kiwigeo]

What sort of spruce is it? Where abouts on the guitar is it?

When I see a crack like this in seasoned wood then humidity is the prime suspect. What you could do is bump up your humidity a bit and see if the crack closes up and the maybe glue in some reinforcing patches along the crack on underside of the soundboard.

Alternately you could flex the top so the crack opens up a bit and then work glue into the crack. Close the crack up using masking or binding tape until glue sets. Ive seen some people use clamps (bar clamp or long cam clamp) to close up the crack.....the clamp pressure is applied to the sides of the top with careful use of cauls to prevent damage to side of guitar.

[Craig]

[quote="Dave Olds"]Bit of a set back with #3.

When you tap on the guitar you hear no difference in sound around where the split is.


G'day Dave,

You only usually get a buzzing sound when the sides of the crack are making contact with each other . This is quite common on pianos ( I'm a Piano Tech by trade ). Chances are that if the guitar takes in more moisture ( with a high humidity change ) you may get a buzzing sound as the crack closes up a little . I've seen ( unglued ) wedges being placed in soundboard cracks to keep the split apart and thereby stop the buzzing, but this is not a good fix.

A split doesn't seem to affect the performance of the soundboard ,provided it's not causing a buzz , so no need to be too pissed off !

The fix is simple and almost invisable. Carve open the crack to form a " V " for the full length of the split . You don't need to make it wide . A very skinny V is good . I have a V shaped chisel I made to do this job . I'm sorry I haven't got a picture .You should be able to come up with something you can make yourself to do the job. Flatten the end of some 1/4 " steel rod on two sides to form a V shape . It'll look something like a screwdeiver tip, in fact an old screw driver would be ideal. Now true up those beaten sides first with a file , and then a sharpening stone so they form a slender and well polished edge but Leave the burr on . (the cutter ). Pull it along the crack gently so that the burr removes a little spruce . Repeat until you have established the "V" It's important you cut some spruce out of the crack to form this V profile rather than just compress the wood to form a V split . You have to take care that you keep the split a uniform width for it's entire length . I fashioned a little depth stop on my chisel for that very reason.

Make yourself a wedged shape slice of Spruce of the same V profile. Trial the fit , and make sure the wedge fits well in width and length . I like to use hot hide glue for the repair. Once dry , plane/sand off the wedge level with the soundboard and you'll find it to be almost invisable.

Some of the old piano makers would subject their soundboards to all sorts of very dramatic climatic changes in order to cause splits on their boards prior to assembly . They would then repair them as I've described above in the hope that the soundboard ( having suffered all the extremes it's likley to encounter ) would never develop any future cracks in it's lifetime.

Good luck with it Dave , but I'm sure you'll be O.K.

[Steve]

Robbie O'Brien ran through some similar stuff recently:
http://www.youtube.com/watch?v=Oj8F-gA9 ... _embedded#
Steve

[Bob Connor]

I concur with Craig's analysis of the situation and subsequent solution.

[kiwigeo]

Bob and Craig, while a splint is a normal course of action for a crack that cant be closed up this crack looks like it might respond to a simpler repair as I outlined above.

Just my thoughts and Im quite happy to be proved wrong.

[liam_fnq]

hey Craig, any chance of a pic of this v shaped chisel you made

[Antipode]

Hey Brother
if the sound isn't effected why not just let the finish get in there. Looks too close to the heel to glue or patch inside anyway. Don't know if you have noticed but finishes stick to timber, they are generally pretty hard. Just treat it like a bit of grain runout

[Dave Olds]

Hey guys - as usual, thanks for the replies and excellent suggestions.

I have also had it recommended that I could attempt to re-humidify the guitar to see if the crack closes, then attempt to stabilise the area with white glue and a cleat or two on the inside. I think I will give that a crack.

It will likely take a few days to re-humidify the guitar - and I will post a picture if successful. I plan to do this with a moist sponge in a container inside the guitar - and with the guitar is a sealed plastic bag.

Thanks again - I'm not so pissed now that I have a couple of possible solutions.

Dave

[Craig]

hey Craig, any chance of a pic of this v shaped chisel you made

I made this many years ago . It needs another sharpen !. The Pics aren't crash hot but hopefully you'll get the idea .

I use a delicate pull stroke with very little pressure so as to cut the wood rather than compress it .



A little piece of felt on the depth stop to save marring the soundboard



You may be able to notice I've filed a V notch into this pullside of the blade , but this probably isn't necessary. Establish a good burr

[John Steele]

Dave;
I can feel for ya...
Perhaps the best course is to wait a bit and see what happens. If the crack remains the same, a splint might be called for if you want to save the top. If it closes up, then perhaps something like Martin suggested will be fine. My money is on the splint, as it looks like a shrinkage crack. I think a guitar can handle expansion pretty well, shrinkage, not so much. Just my thots. Nice work, either way.
Nice cutter too Craig.
J

[Allen]

I just had a similar crack develop in one of my ukes that was up in Ravenshoe for 2 weeks on display when the hot dry westerly came in. Simple to rehydrate. Just get back to Cairns. Fixed it by warming up the hide glue and rubbing in some thinned glue into the crack, then some full strength stuff. I managed to feel inside that the glue had penetrated enough to have wicked all the way through. Then just wiped the top clean and set it aside to dry. Strung it up the next day and it's as good as new.

I can't even tell where the crack was, and I'm the one that fixed it. Always a good sign.

[kiwinoz62]

G'mornin all,
2 part question guys. . .

1.
I have the same problem Dave encounted, but to a lesser degree.
I sprayed the soundboard only to find 2 hairline cracks, about 1" past the bridge, an inch apart & about an inch long. Without finish on the soundboard, you can't see them, apply finish and you notice them. I might point out, you can only see them if you sight down the soundboard at eye level.
I have viewed Robbie O'Briens video, but has anyone out there got any other ideas/suggestions?
Also, I think this has occurred because of the Sydney weather, cool morning, hot day, irregular humidity.

2.
When not working on your build, how do you store it?
Humidity controlled room, guitar case, closet?

I'm thinking of buying a spare guitar case to keep work in-progress in.

Any help appreciated. . .

[Taffy Evans]

Hi Dave, in the photo I just posted you will see [or not see] an open joint I have just repaired. It went from the start of the tail-block the length of the soundboard and into the soundhole.

I had the guitar laid out for a pre-repair photo but got called away. I left the guitar on the bench but covered with a towel and did not get back to it until the next day. When I uncovered the guitar I found that the humidity in the shop had started to close up the gap, I quickly parted the closed part of the seam and rubbed glue into it. I then placed a damp sponge into the box under the open part of the gap and covered the soundhole, this dampness and the moisture of the glue, I think, closed up the rest of the seam. Before the glue set I made sure that both sides of the join was level.

I then glued small cleats inside the guitar spaced out along the joint.

Sorry this post is a bit late, busy busy busy.

DSCF0106.JPG (76.3 KiB) Viewed 16425 times

[Dominic]

Hey, rather than do the fix after it has cracked, its better to prevent it in the first place. In the Kent Everett DVD he advises you to glue 2 small diamond top off-cuts onto the unsupported area of the seam behind the tail block and one between the two tone bars. If your design is different to this you just want to add small 12mmsq patchs where ever there is a large unsupported space on the seam. These get carved right down at their edges and Kent warns that they can effect the sound so tapper them off and make then as thin as possible. A little bit of insurance. This is the spot that seems to get bashed on the edge of the coffee table the most.
Good luck with the repair.
Cheers
Dom

[Taffy Evans]

Yes dead right Dom, the picture shown is of a Martin guitar, I do the little patches on my guitars.