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Warped body!?

roberthabraken

roberthabraken

Jan 8, 2009
1,999
6
The Netherlands
#1
I'm currently building a bass in a very slow pace, due to limited time. A little over six weeks ago, I glued the figured top and veneer to the body core. It was completely flat back then, when it came out of the clamps. Now, it has warped, became concave on the front, so it warped towards the front / top. If you put a ruler on the body, exactly one month ago, the deviation was 0,8 mm, measured at the center. Today, it's 1,16 mm. I probably should mention that the core's a very, very light swamp ash out of one piece.

I am surprised that such a thick body (43+ mm) still moves. Also, if it is because the moisture introduced by the Titebond while glueing on the top and veneer, I'd expect the body to bend the other way: the top of the ash would've expanded, making it bend backwards! The only reason I can think of is that it expanded as a whole and that the ash expanded more than the maple top, making it warp the way it did...

So, I'm curious if anyone can explain to me what is going on?

And, what shall I do with this body?
  1. Ignore the fact that it bent, with the risk of a curved and not so nice neck pocket and a not very well fitting bridge.. hoping that it'll stop warping.
  2. Try to route or sand it flat, with the risk of ruining it and not knowing what will happen afterwards..
  3. Wet the top amply and clamp it, forcing it back to flat and leave it clamped for a week or two.
  4. Start over...

All help and suggestions are very welcome!

These pics illustrate what I'm talking about (look at the left and right bottom of the side view, you can look underneath the body lying 'flat' on the table):

building a bass
 
#3
Hey Rob,
it seems that the moisture curse have fallen on you.
Either your wood supplier does not fall in the "ready to use" category or Tilburg weather is tricky or too much beer around got your wood stoned or all of the above ;).
Now seriously.
It doesn´t seem to me as a huge deal (judging from the picture) as long as the warping ceases for wood soon. I understand that you haven´t route the neck pocket yet. I´d work in the neck, that will give the body a couple of months more to stabilize. Once the neck is finish you can route neck pocket. As for the bridge, if warping is really serious I´d recess the bridge so that it gets leveled. You can always keep the body clamped all this time, that should help.
Btw: To make sense out of what I´ve said the neck pocket template needs to be suspended so that it´s perfectly parallel to the ground (supported by the table), not just laying it over the body since it´s not flat and even. You understand what I mean?
 
#4
Not an expert, just thinking out loud, but here goes....

The issue here is that the moisture is not escaping through the top anymore I reckon. Ie. the back has swollen as the moisture is coming out the back. I've seen the same thing on a wooden chopping block we have. Moisture on one side means the wet side sucks it in and swells. Same thing with your body I think. The water from the tightbond coupled with the strength of your veneer/dried tightbond means the spot that can give and let the moisture exit is the back. Does that make sense?

I think the solution is the lay the body face down in a warm dry space for a month and let the moisture leech out of the back. I suspect it will return (mostly) to it's original shape once you've done this.
 
#5
I cant see it being an issue, seeing as its very small. But if it worries you I see no reason why it would "risk ruining" the bass by planing/scraping/sanding it flat. It will most probably not move again after doing so.
 
#6
whodom said:
~1 mm warpage over ~350 mm width of the body? I wouldn't worry about it. This is a wooden bass body, not a cylinder head mating surface for a diesel engine.
Click to expand...

True, but it's hard to lay down flat and get the holes drilled perpendicular for the bridge, string through and to get the neck pocket flat. Also, I'm worried or curious if it'll warp more than it already did. So I thought I'd ask for everyone's opinion on TB. But indeed, your suggestion of not worrying may be a very good one.

octaedro7 said:
Hey Rob,
it seems that the moisture curse have fallen on you.
Either your wood supplier does not fall in the "ready to use" category or Tilburg weather is tricky or too much beer around got your wood stoned or all of the above ;).
Now seriously.
It doesn´t seem to me as a huge deal (judging from the picture) as long as the warping ceases for wood soon. I understand that you haven´t route the neck pocket yet. I´d work in the neck, that will give the body a couple of months more to stabilize. Once the neck is finish you can route neck pocket. As for the bridge, if warping is really serious I´d recess the bridge so that it gets leveled. You can always keep the body clamped all this time, that should help.
Btw: To make sense out of what I´ve said the neck pocket template needs to be suspended so that it´s perfectly parallel to the ground (supported by the table), not just laying it over the body since it´s not flat and even. You understand what I mean?
Click to expand...

This makes perfect sense and it's basically saying the same as whodom, to not worry and take good care when proceeding with other work on the body.

FYI: I keep the body in a more or less controlled environment. My workshop is heated and I monitor temperature and humidity. Temp varies between 14.5 and 17.5 Celcius. Humidity varies between 47 and 61. As I see it this is not a perfect environment but it's okay.

reverendrally said:
Not an expert, just thinking out loud, but here goes....

The issue here is that the moisture is not escaping through the top anymore I reckon. Ie. the back has swollen as the moisture is coming out the back. I've seen the same thing on a wooden chopping block we have. Moisture on one side means the wet side sucks it in and swells. Same thing with your body I think. The water from the tightbond coupled with the strength of your veneer/dried tightbond means the spot that can give and let the moisture exit is the back. Does that make sense?

I think the solution is the lay the body face down in a warm dry space for a month and let the moisture leech out of the back. I suspect it will return (mostly) to it's original shape once you've done this.
Click to expand...

There are some contrary things in your explanation. From what I know, if something gets wet, it swells. As it dries it shrinks. You say the wet side sucks in and swells, okay, but you also say the back has swollen as the moisture is coming out (= drying), but then it would a) shrink and b) curve the other way. Also, if the moisture couldn't escape from the top anymore (your first conclusion), it would be more wet and thus expanded and thus warping the other way than it actually did. So I cannot follow your theory very well...

Meatrus said:
I cant see it being an issue, seeing as its very small. But if it worries you I see no reason why it would "risk ruining" the bass by planing/scraping/sanding it flat. It will most probably not move again after doing so.
Click to expand...

Thanks. To explain: I do not have a drum sander (and do not know any people how do living closeby), that would be perfect to do this kind of correction. So to get it flat I would have to make up a jig with the router and it's a bit hard to get it seated level in the first place. Furthermore I would have to redo the roundovers and any work with a router is a risk (mistakes or tearout for example).
 
#7
Mmm, I can see what you are saying. I'm guessing your front (maple?) veneer is denser than the back ash. Correct? So the back has soaked more of the moisture out of the glue than the front. Does that make more sense? That would explain why it's come out there instead of the front.

Course I could be completely wrong your air humidity could be off the scale and the ash has acted like a spong. Or, it wasn't dry enough to begin with the warping has nothing to do with the glue, but i tend to think it has.
 
#10
reverendrally said:
Mmm, I can see what you are saying. I'm guessing your front (maple?) veneer is denser than the back ash. Correct? So the back has soaked more of the moisture out of the glue than the front. Does that make more sense? That would explain why it's come out there instead of the front.
Click to expand...

Yes that could be it, didn't think of that, but it sounds plausable!

reverendrally said:
Course I could be completely wrong your air humidity could be off the scale and the ash has acted like a spong. Or, it wasn't dry enough to begin with the warping has nothing to do with the glue, but i tend to think it has.
Click to expand...

As posted above humidity is at 47 to 61 since I glued, could be somewhat higher before, so humidity level dropped rather than increased.

pilotjones said:
How long did you have the ash before it was glued up?
Click to expand...

Just over a month.
 
#12
It is possible that the maple veneer has dried out a little as the ash has absorbed moisture from the glue. I agree with the idea of turning it face down for a while letting the ash dry out.
In the past I have straightened warped hardwood boards by setting them in the direct sun on wet pavement. I am not recommending you be this drastic. The idea is to balance the moisture levels.
 
#14
1 month drying in your working room is a bit short to glue up such a big slap of ash I think. Especially when it is a one piece body.
I don't think the titebond (wet)on the fineer etc has got anything to do with it. I glue my wood always with titebond and then a wet (water)sponge over it to remove excess glue. It gives a real tite glue joint(no glue visible).
I think it has to do with the grain of the ash wood. On one end grain is almost horizontal the other side it is quarter....
 
#15
I wouldn't put it face up or face down... that is, I wouldn't put it with either face blocked. Let it sit with both faces exposed, (like stickered lumber), so it can have its moisture fully equalize, and find out what shape it is going to take in the long run.
 
#16
Thank you all for your input and suggestions.

pushifier said:
1 month drying in your working room is a bit short to glue up such a big slap of ash I think. Especially when it is a one piece body.
I don't think the titebond (wet)on the fineer etc has got anything to do with it. I glue my wood always with titebond and then a wet (water)sponge over it to remove excess glue. It gives a real tite glue joint(no glue visible).
I think it has to do with the grain of the ash wood. On one end grain is almost horizontal the other side it is quarter....
Click to expand...

One month drying is too short indeed, but it was dried already when I received it. If my shop would have the exact same humidity, further acclimatization wouldn't be necessary; that's not the case, but at around a humidity of 50, it probably wouldn't differ much so I guess if it doesn't move for one month while stored stickered, it's okay. That's what I've started with. I monitored the wood accurately, and it only started to move after glueing, so my bet is that it does have something to do with gleuing or any action afterwards.

You are right about the grain being irregular, but the bending is very regular, which doesn't compute. It's not that the 'plain sawn part' warped more than the 'quarter sawn part' (I know these terms are not correct in this application, but they illustrate best what I mean).

pilotjones said:
I wouldn't put it face up or face down... that is, I wouldn't put it with either face blocked. Let it sit with both faces exposed, (like stickered lumber), so it can have its moisture fully equalize, and find out what shape it is going to take in the long run.
Click to expand...

I think that this is the best advice. And I think this also, together with a few other posts, points out what went wrong:

I store my wood stickered. When it doesn't move over a certain period of time I start to use it and from then on, I do not store it stickered anymore, because the moisture content of the wood is equal to the environment and so it doesn't react to the environment anymore.

But... when I glued the top to it, I introduced new moisture content. But I left the body flat on my workbench afterwards. Top up. I covered it with paper to protect it, but that still ventilates better than the workbench. So, the top dried harder (being thinner and exposed) than the core. This probably made it warp to the front. I should've still stored it stickered after gleuing.

That's what I'm going to do from now: store it stickered top down (just to be sure). I keep monitoring it and work on the neck in the meantime. I hope it gets corrected or doesn't get worse.
 
#17
You may have luck with the stickering. Though the secret to successful veneering is balance - if you glue wood to one side of the substrate you need to glue the same thickness and same species (ideally) on the other side otherwise you will have differential forces, shrinkage and warping. Using Titebond is like adding water to one side - it does make a difference that is why pro shops use 2 part glues for veneering. In the future you may want to veneer the back and front of the core
 
#18
roberthabraken said:
Thanks. To explain: I do not have a drum sander (and do not know any people how do living closeby), that would be perfect to do this kind of correction. So to get it flat I would have to make up a jig with the router and it's a bit hard to get it seated level in the first place. Furthermore I would have to redo the roundovers and any work with a router is a risk (mistakes or tearout for example).
Click to expand...

Yes, I understood that from previous posts. But to remove 1mm of bow should be easily obtainable with a scraper or just an old fashioned sanding block. Just keep checking with a straight edge, just like people do when hand planing. A router planing jig wouldnt be necessary, I would also doubt the rounder overs would be noticeably affected, if they were, a quick touch up by hand should do it.
 
#19
powerbass said:
You may have luck with the stickering. Though the secret to successful veneering is balance - if you glue wood to one side of the substrate you need to glue the same thickness and same species (ideally) on the other side otherwise you will have differential forces, shrinkage and warping. Using Titebond is like adding water to one side - it does make a difference that is why pro shops use 2 part glues for veneering. In the future you may want to veneer the back and front of the core
Click to expand...

Thank you, I think you're right and that crossed my mind too. In the future I'll make the sandwich symmetric or use two component epoxy instead of Titebond.

Meatrus said:
Yes, I understood that from previous posts. But to remove 1mm of bow should be easily obtainable with a scraper or just an old fashioned sanding block. Just keep checking with a straight edge, just like people do when hand planing. A router planing jig wouldnt be necessary, I would also doubt the rounder overs would be noticeably affected, if they were, a quick touch up by hand should do it.
Click to expand...

Well, with a hand plane it could be possible, but sanding, no. I had to remove marks of the planer (about 0,2 mm deep) and that took me hours to sand out. So 1 mm would took days of sanding, especially because the maple is rather dense. A roundover of 12,7 mm wouldn't be smooth anymore after taking of more than 1 mm (that's almost 10%), but indeed, it shouldn't require much to get it back to its original shape again.

By the way, I also noticed the warp has also occured in the lateral direction, but not that much. I think the best option would be to leave it longer, stickered, and hope it'll even out and furthermore don't worry too much about it, as it's subtle and not worth all the expense to make it perfectly flat again.
 

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