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Please help re warping of fronts and back
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=14789		 Page 1 of 1
Author:  cgal_1 [ Mon Dec 03, 2007 8:06 am ]
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I'm new to building having made one guitar in my house.


I've now set up a workshop at the bottom of my garden.


I've made two fronts which were flat when I braced them, but have now gone concave when I bring them into the house. Similarly a back with a 15' radius is now flat after being inside for a few days.


Should I store my wood in the house?


Is it the changing temperature (I'm in England)


Any thoughts or suggestions would be really appreciated, I just can't afford to waste wood at this rate.


Charles.
Author:  WaddyThomson [ Mon Dec 03, 2007 8:13 am ]
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Humidity Control - 42 - 48%!
Author:  JohnAbercrombie [ Mon Dec 03, 2007 8:20 am ]
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Charles-
This is a relative humidity issue, I think. My guess is that your house is warm and the RH is lower than in your garden shop.
I had a similar problem when I put a finished guitar into a 'warm room' (closet with heater) to get the lacquer to harden up more quickly. Back went concave. Next purchase was a dehumidifier and a RH meter (Caliber III digital hygrometer).
You need to move your building work into the house, and/or get the RH under control in the shop (and house).
BTW, this sort of thing happens quite a bit- once you've chiselled/planed off the braces from a few plates, you get much more motivated to get the RH under control.

You've only wasted some time and bracing material- the plates should still be usable after re-bracing.
And, yes- your wood should be stored in a controlled RH area.

Cheers
John
Author:  WaddyThomson [ Mon Dec 03, 2007 8:21 am ]
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By the way welcome to the OLF, Charles.  Check the archives for a thread from RobertD - Humbled by Humidity.  Here it is.  Humidity control is a primary key to keeping things from warping into potato chips.
Author:  Hesh [ Mon Dec 03, 2007 8:23 am ]
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Hi Charles and welcome to the OLF my friend.

Waddy is correct as always and the relative humidity (RH) is your culprit here.

Having a place to work and store your work-in-progress that has a RH of 42 - 48% is a must for guitar building.  Even those who may get away without having a stable RH for a while have been known to have nearly completed and completed instruments fail as a result.

I live in Michigan where in the summer I have to dehumidify my shop and right now in the winter with forced air heat I am dumping water into the air with humidifiers.  There is no way around this if you do not wish to become a victim of what wood does, what ever it wises to do, with humidity changes.

We hear this often, perhaps weekly here on the OLF but once the builder creates a stable RH environment this problem is resolved.

Again welcome to the OLF.
Author:  Michael Dale Payne [ Mon Dec 03, 2007 8:27 am ]
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If not able to get RH under emediate control the brace and attach to body with 48hrs of bracing once on rim the movement is more restricted. But cincaving in even attached plates (between braces) can happen
Author:  Michael Dale Payne [ Mon Dec 03, 2007 8:30 am ]
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If not able to get RH under immediate control the brace and attach to body with 48hrs of bracing once on rim the movement is more restricted. But concaving in even attached plates (between braces) can happen

Author:  WaddyThomson [ Mon Dec 03, 2007 8:35 am ]
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Charles, I didn't mean to shout, but Hesh is right, it is a weekly topic here at OLF.  Sometimes it's how to control humidity, sometimes it is like you, something warped, sometimes it is about sling psychrometer's and other humidity measuring devices, etc.

OH, Michael, I still have that link to the typing lessons.  They are FREE!

Author:  WaddyThomson [ Mon Dec 03, 2007 8:38 am ]
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Sorry, Michael, I didn't hear you.  Stick it where?    
Author:  Michael Dale Payne [ Mon Dec 03, 2007 8:39 am ]
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There
Author:  Hesh [ Mon Dec 03, 2007 8:40 am ]
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Michael is just trying to catch up to my post count by acting like he can't type in one post and then posting the same thing, correctly speeeeled..... the second or third time........

And yeah Waddy was not yelling, he does not yell but he does fart.
Author:  Michael Dale Payne [ Mon Dec 03, 2007 8:40 am ]
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Oh.. That's right. Your not sure how to get there
Author:  Michael Dale Payne [ Mon Dec 03, 2007 8:43 am ]
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No chance Hesh.... after all I had a couple year head start.....Still cant catch you
Author:  WaddyThomson [ Mon Dec 03, 2007 8:44 am ]
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Getting the count up is why I post so many empty windows.  

I'm just another of the "Lost Boys", Michael. 

Author:  cgal_1 [ Mon Dec 03, 2007 8:45 am ]
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Thanks for all of the advice.


The big problem is that I've been thrown out of the spare room I used to make the first guitar, and have to use the workshop which has only an oil filled electric heater which cant be left switched on all of the time. I have to switch it on about 20mins before working there.


Would there be any point in putting a humidifier in the workshop and trying to match the RH to the reading in the house?
Author:  Hesh [ Mon Dec 03, 2007 8:45 am ]
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Take this then.........
Author:  Michael Dale Payne [ Mon Dec 03, 2007 8:53 am ]
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My guess is the warping was caused from a large fluctuation. 42-48% is perfect but as long as you can control the shifts you can be higher or lower and not have problems. The trick is the control more than the number.
Author:  WaddyThomson [ Mon Dec 03, 2007 9:01 am ]
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If the humidity is relatively high, a dehumidifier in your shop will also keep it pretty warm.  They produce a lot of heat.  However, if it is like it was around here over the weekend, you'll need a humidifier.  It was 20% here Saturday, for most of the day.  I find myself running both, sometimes, to keep things stable.  My humidifier doesn't have a humidity control on it.  Some of the Warm Mist humidifiers, would tend not to cool the air, at least.  I also have a oil filled radiator in my shop.  I leave it on most of the time, but on a very low setting.
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