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A bit of topic, but would appreciate the advise...
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Author:  cyborgcnc [ Sun Mar 23, 2008 9:04 am ]
Post subject:  A bit of topic, but would appreciate the advise...
Hi All,

I am in the process of a '59 Les Paul replica, and so far, things are going nicely (especially for the neck) but not so good for the body.....

After cutting and joining my body blank (mahogany), and then gluing the top on it (Quilted maple), to my surprise, after a couple of days, the whole blank has "bowed" upwards....I payed attention to lay it flat, but for some strange reason it bowed, after making sure that both the top and bottom were perfectly flat (I used a planner to get them to the right thickness, and dead flat). I am sure this was not caused by the clamps, since after I removed them, the blank was dead flat. The halves and top were joined with Titebond.

I am not sure what went wrong, but is there a way to make it flat again? I tried leaving it for a couple of days with some weight on top of it, but it is still bowed....

I was wondering if any of you had any suggestions, that will allow me to salvage this, as the top has some very nice quilt. Planning it again would not be a good thing, as I would loose the thickness required..

[headinwall]

thanks in advance for any suggestions.
Author:  Don Williams [ Sun Mar 23, 2008 9:22 am ]
Post subject:  Re: A bit of topic, but would appreciate the advise...
Sounds like moisture was your enemy, and wood that was flatsawn? Bummer....I feel your pain!
Any particular reason reason for quilted maple rather than curly?
Author:  burbank [ Sun Mar 23, 2008 9:23 am ]
Post subject:  Re: A bit of topic, but would appreciate the advise...
Not OT at all.

If by bowed upwards, you mean that the middle bowed upwards, I would guess that it's because of the water from the glue that the wood absorbed. The body blank was wetted on only one side, which caused it to swell.
Author:  TonyKarol [ Sun Mar 23, 2008 9:25 am ]
Post subject:  Re: A bit of topic, but would appreciate the advise...
Bowed how much ???? Most will say the titebond did this, and I agree to some extent due to its water content, but I have made a bunch of laminated guitars ala LP with TB and never had this problem .. wood dryness and shop climate is more likley the culprit

Since you are doing a LP .. you need to carve away most of the outer edges to do the violin carve anyway .. will it matter ???
Author:  Hesh [ Sun Mar 23, 2008 9:29 am ]
Post subject:  Re: A bit of topic, but would appreciate the advise...
Many builders will maintain a relative humidity of 42-48% in their shops or wood can vet uppity..... You also want to allow time for your wood to acclimate to the stable humidity environment as well.
Author:  cyborgcnc [ Sun Mar 23, 2008 10:15 am ]
Post subject:  Re: A bit of topic, but would appreciate the advise...
yes, it bowed in the middle. I know that the top will be carved, but the bottom will still be bowed...not sure if this will matter, but would rather have it flat.

I did not wet one side...just spread glue on both sides, and clamped...it was dead flat for a day, but then 2 days later, bow...

oops_sign

So I guess I am SOL??? :-)
Author:  Mike_P [ Sun Mar 23, 2008 10:34 am ]
Post subject:  Re: A bit of topic, but would appreciate the advise...
I think what burbank meant was that only one side of the woods got wet (that wetness coming from the glue) as opposed to both sides of each piece being wet...

the best simile to this concept I can offer is a rule I learned about making custom bookmatched panels of solid resawn pieces of wood being glued to lets say 1/8" plywood...when one does this it is a dang good idea to laminate to both sides of the 1/8" as when the glue dries its putting a load on the core (the 1/8") which causes it to warp...by gluing up to both sides this is prevented...as wood glues dry they first expand into the grain of the wood then shrink as they finally cure...

I've read an article by a person who made a Les Paul and he detailed how he did his glue up of the top to body and then did the final thicknessing after the glue had cured, which sounds like a dang good idea...I would just flatten the back and carve the top of your project and approach your next in a different manner...

did you use African Mahogany for your body blank? I've heard that this species need be well quartered to use for a solid body, whereas 'genuine' can be flatsawn...

as far as the quilted top...well I agree, those rock!

as Hesh has pointed out, letting woods acclimate to the shop environment is a necessity...in the old days hardwood floor installers used to let the woods sit in their intended environment for up to a year so that they would do their thing before they got installed..
Author:  Brock Poling [ Sun Mar 23, 2008 10:48 am ]
Post subject:  Re: A bit of topic, but would appreciate the advise...
Here are a couple ideas for you.

If you are going to make a LP custom style instrument (I know you were planning on doing a '59 LP standard... but customs are cool too). Plane the back flat and laminate on an extra piece of mahogany (use epoxy instead of a water based glue). You don't need to worry about the top being flat as much because you are going to carve it, and it sounds like the bow is going the right direction. Then, when you bind the back the bindings will hide the seam.

And for future reference (I learned this the hard way too) use epoxy to laminate your plates to the body, and always plane to final thickness after the block is glued up.

I feel your pain.
Author:  Mark L. [ Mon Mar 24, 2008 7:38 am ]
Post subject:  Re: A bit of topic, but would appreciate the advise...
The wood fibers have probably swelled due to the moisture in the glue. This causes the wood to develop a cup due to one side having more moisture than the other. If you simply spray a little water on the back side and let it lay overnight with the back side down on a flat surface, most, if not all of the cup will disappear. I have had boards used to build cabinets, shelves, etc. that were cupped due to one side drying out more than the other, and this method has removed most of the cup, usually overnight. I would let the glue cure a few days, then see if it is still cupped, if it is, then I would try this method. Good luck!
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