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Centreseam gap
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Author:  Bosco Birdswood [ Wed Dec 30, 2015 7:33 am ]
Post subject:  Centreseam gap
I'm building an acoustic and I joined the plates really invisibly, but then realised a brace was the wrong way around (blame Compiano!) and took the fatal decision to apply heat from an iron in order to loosen the glue. This worked very well, but also predictably undid my nice centre seam. You live and learn. It's stable but is now quite visible since being re-glued.

From what I have read, I have 4 options.

1. Glue in a splint. Instructions for this gratefully received!
2. Wet the plates either side of the joint am to encourage it to expand and close the joint. I'd have to dig the glue out first. Both of the above make me nervous. Again, instructions on this method gratefully received.
3. Mix some sawdust in with some tightbond and try to fill / hide the gap with that
4. Leave it. It's not that bad. But I know it's there.
Author:  Hesh [ Wed Dec 30, 2015 7:44 am ]
Post subject:  Re: Centreseam gap
Question what kind of humidity control for your shop and work in progress are you using AND do you have a hygrometer and is/has it been calibrated against a reference standard?

To your questions:

1) Splints often show.
2) Using moisture only temporarily expands wood it will shrink again and if it can't separate in the original seam it may very well likely split the top elsewhere, something has to give...
3) Any filler will show with spruce... AND is not structurally sound enough for this important joint.
4) It will bother you forever and keep you up at night until it becomes an obsession and you can think of nothing else. This will lead you to excessive drinking, job loss, relationship failures, the IRS on your arse, and receiving unwanted membership offers from the AARP that ruin your day.

If it were me I would be keen to cut the joint out, true up for a new joint and make it so if the top material is large enough for this.

There is a tradition on the OLF for over a decade now and it's commonly heard as well and goes like this: Do it over and make it right! :)
Author:  SteveSmith [ Wed Dec 30, 2015 8:18 am ]
Post subject:  Re: Centreseam gap
Redo it and make it right. I just finished a guitar that I re-topped because the first top just wasn't right. I'm glad I took the time to redo it. In the future, if a brace isn't right, then just carve it off.
Author:  kjaffrey [ Wed Dec 30, 2015 8:38 am ]
Post subject:  Re: Centreseam gap
I would be with the others. Carve off the braces and redo the joint. Still being early in the build it totally takes care of something that you will regret later and doesn't waste time on a fix or two that likely won't be ideal. In my builds I have wasted too much time trying to fix something the easy way only having to go back and redo it in the end.
Author:  DennisK [ Wed Dec 30, 2015 9:06 am ]
Post subject:  Re: Centreseam gap
Here's an idea to make lemonade out of your lemon... if you have all the braces glued on, carve them and tap and flex the top and get a feel for how the tap tone and stiffness change as you remove brace material. Keep going until you're pretty sure you've gone too far for it to survive under string tension. And then keep going further, until it's just too floppy to even bother, and finally chisel/plane the braces off. Redo the center joint, rebrace, and carve again with your enhanced knowledge of when to quit :)
Author:  meddlingfool [ Wed Dec 30, 2015 12:53 pm ]
Post subject:  Re: Centreseam gap
FWIW, you could have left the brace as is. It makes very little difference which way the braces are slanted.
Author:  Ruby50 [ Wed Dec 30, 2015 1:14 pm ]
Post subject:  Re: Centreseam gap
Replace a back late in a build - check. Refinish before the finish is done - check. Toss out a neck and make a new one - check. You WILL NOT be happy with it if you don't fix it now.

Ed
Author:  Rod True [ Wed Dec 30, 2015 1:56 pm ]
Post subject:  Re: Centreseam gap
Yup as all the others have said. Make it right. You'll always wonder. Brace wood is cheap when looking at the entire build cost (time included) of an instrument.

Plane off the braces, cut the plates apart, re-shoot the joint and glue it back together. All other options are either a bandaid or a repair on a completed instrument which has been in service for some time.

I've built two guitars now that I've re-toped a total of 3 times (4th top worked out) due to poor "repair" or design flaw. You only learn to do it right when you actually step back and decide to do it right.
Author:  Tai Fu [ Wed Dec 30, 2015 1:58 pm ]
Post subject:  Re: Centreseam gap
Unfortunately splints will always show. I had a guitar in my shop that had those belly cracks (possibly due to dryness?) and since they were left that way for a long time I had to dig the old wood out (it was caked with dirt) and glue in a splint. I reinforced the underside too (it was moving). I used the same wood species as the top wood but unfortunately it still showed. Even tried touching up with some Vintage Amber tint but it still showed. Owner was ok with that, he was more concerned with the structure than the look but if it were my choice I would have refinished it.
Author:  Bosco Birdswood [ Wed Dec 30, 2015 2:59 pm ]
Post subject:  Re: Centreseam gap
Hi guys,

Thanks for all of your replies. I should have probably qualified in saying that the guitar is basically complete. The ship sailed a long time ago with regards re-doing the top. This is the first guitar I have built on my own (I built one on a course in 2011), and it has been a massive learning curve. I completely agree with your collective ethos regarding re-doing the top. My fatal mistake was adding heat, rather than doing the now obvious thing of planing the brace off.

If you see my other posts you'll see that I've also just re-winged and re-veneered the headstock to great effect having got to the point where there were too many flaws with it. This is absolutely the way I would go with the top next time.

Anyway, rather than wallowing in my own shoulda-woulda-coulda I've just got to make the decision in these crucial final stages as to how and indeed whether I fix this cosmetic issue. The split is structurally sound and has reinforcement on the other side, so it won't come apart. It's just not invisible. The attached picture is of it glued up. Basically the imperfection is filled with glue. It's just a little unsightly.

Given this new info, what would you guys do?
Author:  Rod True [ Wed Dec 30, 2015 3:47 pm ]
Post subject:  Re: Centreseam gap
A new guitar, I'd still re-top it. It's brand new....... [uncle]

I've had a few of my own builds with bridges on and all finished up and still didn't like a "repair" to the top so I re-topped it.

It's up to you but you will always look at that and continue to wonder weather you should have put a new top on it. It's just time and a bit of money for a new top, brace wood and binding. What you learn from redoing it is invaluable.
Author:  Imbler [ Wed Dec 30, 2015 4:02 pm ]
Post subject:  Re: Centreseam gap
I'll be a contrarian and say just leave it or splint it. It is your first, and you don't want it to be so frustrating that it takes the fun out of it.

I'm also reminded of the Cat in the Hat story where the cat keeps trying to remove a small stain in the snow, and it just gets diluted and gets bigger and bigger and everything is stained. Retopping, while valuable experience, could leave you with greater cosmetic flaws than you currently have.

If you splint, my approach would be to take a dremel with a router base and tape a guide on the top, then route that glue section out about 2/3 thickness of the top. If you try to carve it, the hard glue vs the spruce would be tricky. Once you have routed that section of glue, you could use a v chisel to v out the gap and form a shim to fit. Others can probably give better advice on how to approach it, though.
And even adding a splint 'could' make it worse cosmetically. Your call - isn't this fun?
Mike
Author:  George L [ Wed Dec 30, 2015 4:19 pm ]
Post subject:  Re: Centreseam gap
Depending on where this gap is in relation to the rosette or binding you may be able to cover it by inlaying a complimentary design element. Of course, that could go terribly wrong and necessitate a re-top, so... idunno

If it makes you feel any better, we've all been in similarly tough spots. Keep it fun and everything will work out fine in the end.
Author:  Mike OMelia [ Wed Dec 30, 2015 5:10 pm ]
Post subject:  Re: Centreseam gap
Post a pic in bright light of the whole top to give the split a big more context. Also, is this a keeper? (Self use)

Edit: that looks very small. You could drop fill that with finish (would take a long time), or some West System Clear epoxy, tape off the area well, scrape back. Much faster. Then use a nice Amber finish. Do not use super glue. You can have weird colorings result with spruce.
Author:  wbergman [ Wed Dec 30, 2015 7:24 pm ]
Post subject:  Re: Centreseam gap
I assume that you were making this for yourself. I have travel guitars that I do not have to worry about taking on vacation. Maybe you could use it similarly.

You can consider an opaque colored finish, e.g., Hesh's black ones.

When you say "basically complete", I do not know how far along. If the rosette is in and the neck and bindings on, there seems not too much difference to fix it in a few years if you cannot get used to it or if the joint opens.

I have heard that Greg Smallman (classical in Australia going for $30,000) commonly removes tops and replaces them as he builds if he doesn't think the sound is perfect. Do any of us do that??
Author:  johnparchem [ Wed Dec 30, 2015 7:50 pm ]
Post subject:  Re: Centreseam gap
The gap is small. I would say make sure it is level, fill if necessary and finish the guitar. I would probably apply a wash coat of shellac to the top and use medium or thick CA to fill. Level and apply your finish.
Author:  Bosco Birdswood [ Wed Dec 30, 2015 9:06 pm ]
Post subject:  Re: Centreseam gap
So I took everyone's advice on board and decided to use a test piece of bunya to see how good I could get a splint repair. I was pretty pleased with the results after a few attempts, so decided to just proceed with this repair on the guitar. It took a couple of attempts, but I'm really happy with how it turned out. You can still see the last few cm of join, but hopefully by the time it's sanded, shellac'd etc etc that will be pretty insignificant. As Cocobolo said, I don't want to start making a small issue big by not knowing where to leave it.

Thanks as always for all of your advice. Here's the finished result.
Author:  Mike OMelia [ Wed Dec 30, 2015 11:14 pm ]
Post subject:  Re: Centreseam gap
Who is cocobolo? Lol.

I think ur repair is quite good
Author:  Rod True [ Wed Dec 30, 2015 11:36 pm ]
Post subject:  Re: Centreseam gap
Mike O'Melia wrote:

I think ur repair is quite good


Agreed. Sorry for the retro advice. I thought it was worse than it actually was I guess.



Sent from my iPhone using Tapatalk
Author:  jac68984 [ Thu Dec 31, 2015 3:09 am ]
Post subject:  Re: Centreseam gap
meddlingfool wrote:
FWIW, you could have left the brace as is. It makes very little difference which way the braces are slanted.


This advice is both sound and worth repeating. The likelihood you could hear any meaningful adverse difference caused by reversing the direction of the lower face brace, especially on an early guitar, is slim to none.

If this were for a client, retopping would be in order. But for a personal, first solo build, I like that you went with the splint. It adds charecter and will someday make you appreciate how much improvement comes as you continue to build. My first guitar is far from perfect; I now have the chops to "fix" a fair number of those imperfections, but unless they affect playability I never will.

Nice work.
Author:  SteveSmith [ Thu Dec 31, 2015 7:54 am ]
Post subject:  Re: Centreseam gap
Nice job on the repair.
Author:  wbergman [ Thu Dec 31, 2015 8:34 am ]
Post subject:  Re: Centreseam gap
You mentioned there is still a small gap. If no glue filling it, use white glue and sand in some dust from the top. I built a guitar years ago that had some prominent gaps between the spruce top and the binding (no purfling on this one). I put in some Elmer's glue and sanded dust from the top, avoiding sanding the binding. I was pleasantly surprised that the gap became invisible. I still have this guitar and I cannot find the repair areas, even though I know I did this. This is a time honored method. I think one of the others above posted this as a suggestion instead of the wood sliver, but you did a great job with the wood sliver.

Some people sand in top dust routinely to fill the gaps around the rosette during installation. It's nice to have a perfect rosette fit, but you can be fooled. If you routinely add some wood dust from the top you have some simple insurance on the possible gaps. If you do not do this step and have a gap with glue filling it, it is too late once the glue dries.
Author:  kencierp [ Thu Dec 31, 2015 8:55 am ]
Post subject:  Re: Centreseam gap
I repectfully disagree with the glue and dust gap fill method on light color woods. If not immediate the repair is likely to darken over time and actully tends to highlight the defective area. With dark woods this can be effective provided the area is sealed prior to using any type putty.
Author:  douglas ingram [ Thu Dec 31, 2015 11:31 am ]
Post subject:  Re: Centreseam gap
For where you are at, you made the right choice. Repair it, move on, build a new guitar. In this instance it really wasn't so terrible that your reputation was at stake.
Author:  Bosco Birdswood [ Thu Dec 31, 2015 3:12 pm ]
Post subject:  Re: Centreseam gap
Hi guys, thanks very much for all the votes of confidence. I'm pretty happy with it. I actually had tried the glue with dust method but maybe didn't add enough dust. The result was what I initially posted above.


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