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Hi Everyone,

I bought a classical serviced kit from LMII (Englemann Spruce with EIR Back)
Recently after bracing the back, I noticed a crack at the top part of the back where there is no back reinforcement

The struts for the back was planed to a curve.
Then the back was braced using free from (no radius dish)
method: only clamps and curved braces.
After the back was braced then I add in the back reinforcement strip.

Question is do I need to do anything to the crack?
It is located at the joint EIR - Maple strip - EIR part at the place where the Spanish heel is supposed to be

Or will it mend itself once the I glue the back to the rest of the assembly?

Thanks for the advice.
Sen

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Sen CL Goh
http://senguitar.blogspot.com

Welcome,
I pretty much agree with Hesh's assessment, except about the brace removal.

It may not be that serious, especially if the crack pretty much is closed.

As he says, what caused it. IF flexing the back or rough handling caused it then I'd just super glue and clamp.

If you do this and it holds together once released from clamping, it should fly.

If it pops open, well, then follow Hesh's plan it's a good one.

_________________
http://www.dickeyguitars.com

Hi Hesh,

Thanks for the fast response.

Ashamed to say, I did not control the RH in my room as I have no means to control the RH...
I have measured the RH; it can fluctuate anything from 59% to 80%

I will monitor if the crack develop any further.
If it doesn't, could I just glue it up the crack?
If it does then I am clueless as to what to do to remedy it...


Sen.

_________________
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Sen CL Goh
http://senguitar.blogspot.com

Hi Bruce,

It might have been caused by the curvature of the brace.
I did not use any form of radius to guide me when I plane the brace's curvature.
So the curvature at the joint might be have too steep a gradient.
What I did noticed is that if I flatten that part of the back the crack does seem to close back.

If I need to remove the back brace. How do I do that?
I am using Elmer's Probond glue to glue the back brace

Sen

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Sen CL Goh
http://senguitar.blogspot.com

If you take the brace off I just plane mine off with a hand plane and then use a scraper to clean them up.

You really need to get control of your humidity and get some form of a radius tool, at a minimium you can buy a lexan radius gage from Luthier Supplies (listed as a sponsor above) or get a radius dish. You will need this for various tasks...

Welcome to guitar building. :-) Don't sweat it. There will be lots of situations like this.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Hi Hesh / Bruce / Brock,

Thanks for the valuable advice.
What Hesh said is very true, it would be even worse and harder to remedy if the crack would develop after the guitar is closed.
I will remove the brace and glue back the crack.

I am thinking of building a box with acrylic sheet sealed with silicone at the joints and place all the wood inside it.
Then I would put some silicon gel dehumidifier (those kind used for storing camera) inside that box.
Hopefully it will work.

Sen

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Sen CL Goh
http://senguitar.blogspot.com

Hi Hesh / Bruce / Brock,

I have measured the curvature, it is indeed abit too exessive about 7-8 mm.
So I chiselled the braces away.
The bracing will be plane to a depression of about 4mm (about 20' radius)
When clamping I will use a air tight plastic bag with the silicon gels inside.

Thanks for your time and advice.

regards
Sen

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Sen CL Goh
http://senguitar.blogspot.com

Hi Goh, welcome to the OLF, I think your the first member from Singapore

Looks like you have some good advise already. I would like to talk about something else if you don't mind.

From you last picture there it looks like you just popped the brace off, is that correct? You shouldn't be able to pop the brace off with a chisel at all. There should be some wood failure otherwise your glue joint was was starved or something else. From your picture there are only slight bits of spruce on the rosewood and a few glue spots too. Now maybe you heated up the brace first, but I think you may have had a bad glue joint there.

Oh and I don't think your curvature is to much, just ask Dave White (UK) how tight his back curvature is, I think he uses 12' radius when most of us use 15'.

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I would agree with Rod here. If the brace popped of as it appeared in the photo then you would likely of had a brace failure in the future. I don't mean to be a barrier of bad news but if this is typical of any of the other braces then I would have concerns on all of them. The lack of failure in the spruce in the middle of the brace area when carving or as you did prying off would lend me to believe that you had bridging where the spruce is not in contact with the wood at all and the glue was fill a void. Or as Rod said the it was glue starved.

I certainly hope to be wrong here

Hi Rod, Michael

Thanks to all for your feedback and valuable advise.
This is such a wonderful forum; I learnt so much from you guys.

You are right, the brace came off pretty easily.
I applied the gluing evenly and thinly by hand on the brace.
I think the brace's gluing surface is not flat at some point.

Currently, I am using free hand and a Stanley block plane level the brace.
The only way to ensure the gluing profile is flat for me is by visual inspection.

Do I need a sort of jig in order to ensure the the brace's gluing surface is flat?
I guess the best way to ensure a flat gluing surface is to use a radius dish.
But importing the radius dish from the US by post would cost me a bomb.

Could it also be that, the glue is not appropriate for the job?
I am using Elmer's ProBond
In Singapore I cant find anyone carrying in TiteBond
Do you think I should use some other type of glue?
I have some HHG from LMII


Sen

_________________
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Sen CL Goh
http://senguitar.blogspot.com

Sen,

I used Elmer's ProBond on my first and it is fine, same basic glue as titebond I. You'll be fine with it. Use the HHG if your comfortable with it though.

Take a look at these sites for some idea of how you can make your own dishes. Having dish's really ensures that the brace is flat over its length, they are not necessary but they sure do help. They also really help make sure the rims are shaped the same as the back and top, glue up becomes as close to perfect as possible.

Letseatpaste's blog (he's a local OLFer)

MIMF forum

Jon Sevy Arched workboard

And some OLF discussions on arching braces.

1

And in this next one I show a simple jig to help cut the arch of the brace on the table saw, could be bandsaw too mind you.

2

So, your glue should be fine, you really want to ensure that the brace runs a consistent arch for its entire length, you don't need the sanding dishes to do this, they help in the long run though.

Hope some of this helps.

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"There's really no wrong way, as long as the results are what's desired." Charles Fox

"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman

"Generosity is always different in the eye of the person who didn't receive anything, but who wanted some." Waddy Thomson

Hi Rod,

Thanks for the links.
They are very helpful.

The dish building jig looks cool.
But for now, I think I won't be doing the dish as yet.

Your bracing jig looks simple to build.
The dowel spacing between each other and distance from the edge will determine the amount of arc, rite?
Do you have the dimensions for 15', 25 arc'
Instead of a table saw, I could use a jig saw or a plane
to do the cutting.
Sorry, my tools are pretty primitive, mostly hand tools.

Thanks once again for the links!

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Sen CL Goh
http://senguitar.blogspot.com

How are you clamping these braces?

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I have measured the RH; it can fluctuate anything from 59% to 80%





Sorry to say, but until you have the above situation resolved, you're fighting an uphill battle with no chance of success. Wood is wood, physics is physics, and you're not going win this battle. You must control your humidity better, and use wood that is acclimated to it.


Or begin building all-carbon fiber instruments.

Hi grumpy,

I intend to use a sealed plastic bag to put the wood inside with silical gel to control the moisture before I clamp the fixture.

Alternatively I can make a sealed acrylic box with silicon gel to control the moisture.

Hi Brock

I attached a pic of how I clamp.
I will improve upon the process as I am thinking of using wedge much like the way we do a back joint or top joint.

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Sen CL Goh
http://senguitar.blogspot.com

You know...

I hate to be discouraging... but I would HIGHLY recommend building or buying a few tools. It will greatly help you on your quest.

First, make a couple radius dishes. You can make them pretty easily out of MDF or high quality plywood. If you search the archive you can find a technique for doing this, but essentially you make a couple of rails with an arc cut into them that the router can ride on as you carve out a dish.

And the second thing you should build is a go bar deck (there was a recent thread about this as well). It will help a TON with clamping braces and other parts of the guitar.

Guitar building is a LOT of fun, but it does require that you build or buy a few specialized tools along the way.

And as Mario says.. you HAVE to get that humidity issue under control. It is going to plague you through the whole process if you don't.

Hang in there... we have all been there.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

You need to control the whole room, not just the wood. If you dry the wood in a bag, then bring it out to work with it and clamp stuff to it, it is moving while you work. And it will keep moving after you're done.

Not good.... Sorry, but it's the honest truth.

How fast does wood move? I thought it would be fine to build a HR controlled cabinet to store the wood in while its not being worked on. I've seen it suggested several times, especially on MIMF. I take it that this poor advice?

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Aoibeann

Hi Grumpy,

Yes I would love to control the RH for the whole room.
A RH controlled workshop with all the tools drill press, table saw etc.
Currently, I don't even have a proper workbench; I work mostly on a small portable table. (The table you saw in the last picture)
Hard on my aching back...

However the ideal condition to work with, is a dream right now.
I would love to set up that dream in near future.
As of now I could only add tools as I go along.
So the best I could do now, is to control the RH in a small confined area like a seal box or plastic bag.

Brock, Grumpy, Hesh, Rod, Michael, Bruce, and the rest of the members,

Your words have been most encouraging and helpful.
Thanks for all the help you have rendered.
I have learnt a lot, in terms of innovative building methods / tool ideas from the talented OLF community.
I will try to improvise as best I could, as I go along.

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Sen CL Goh
http://senguitar.blogspot.com

Improvising is indeed what you, and all of us, must do at each and every turn. Wood is a magnificent, but extremely variable and temperamental medium. Don't give up.

Can you make a small room, completely sealed? Think of your plastic bag, but large enough for you to work inside of?

that, is the minimum you'll need.

a "dry box" like is often suggested can work, I suppose, but how well it does depends on how wicked the change in RH is. If the dry box is at 45%, and the room at 80%, the wood will move and do the bacon right before your eyes....  

I'll throw my hat into this as well.

I've used the "dry box" the last wet season and it was a bit of an adventure trying to get things glued up. It did work but it is also a lot of work.

I did spend weeks waiting for my top and back plates to come back into shape in order to continue on with the building. Patience is definitely and asset when it comes to building in the tropics. Swings from 50 to 95% RH within days...sometimes faster depending on the way the wind blows.

This weekend I'm on the hunt for a small dehumidifier to set up a small bedroom up as a workshop. Well, just for storage and glue up. The wife would kill me if I started to make saw dust and shavings in the house.

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Allen R. McFarlen
Barron River Guitars & Ukuleles
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