Author Topic: Temperature and humidity control (Equilibrium Moisture Content of Wood)  (Read 5200 times)

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Hartung

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Hi,

Do you control temperature and humidity of the timber you are working with? I'm especially interested in two things.

What is the temperature and the humidity of
a) the room you store your wooden bows and
b) the room you store your dry bow staves in?

Or don't you take care of those factors, just dry your staves for some time and then start building your bows?

And a third question:
c) Is there a chart that explains the ideal moisture content in the most common bow woods (yew, elm, BL and so on…)?

I ask those question because I'm afraid that my timber is to dry and I'd need to put it into another room.

Here is a chart explaining the Equilibrium Moisture Content of Wood depending on air temperature and air humidity. According to that chart, some staves I have would be under 6% of MC. They will explode if I work them like that L.



Thanks!



Offline DanaM

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Re: Temperature and humidity control (Equilibrium Moisture Content of Wood)
« Reply #1 on: December 15, 2007, 06:56:24 am »
I'm sure someone will be along that can answer your question better than me. In the summer its very humid here
so I usually keep my staves in a hot bax where I can control the humidity as a damp bow generally takes more set
and is sluggish. In the winter with the furnace running the humidity drops way down so I don't worry to much.
Woods are all a little different in how they react to humidity, hickory most likely being the worst likes it dry, I believe most white
woods absorb moisture quicker than say osage. During hunting season if I've been out in the damp I will put my bow in the hotbox for storage
and to keep MC down a bit. I think as a test you could do the bend test as outlined in TBB might offer you a clue as to what to expect.
 
"Prosperity is a way of living and thinking, and not just money or things. Poverty is a way of living and thinking, and not just a lack of money or things."

Manistique, MI

Offline adb

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Re: Temperature and humidity control (Equilibrium Moisture Content of Wood)
« Reply #2 on: December 15, 2007, 11:13:28 am »
Hi,
From my experience, moisture content is ideal at 8-10%. Less than that, and you risk breakage, more than that, you end up with slow limbs, and extra set (in the white woods, especially).
I store my wood in a small space in the basement, where I can control the temp and humidity. I use a dehumidifier, and keep the RH between 45-50%. I keep the temp at around 20C. Most kiln dried board wood has decent moisture content, and can be used right away. I mostly back board bows, hickory or bamboo.
Staves need time, and I use a hot box and a moisture meter. Be patient with staves... some need months to dry.

Offline Pat B

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Re: Temperature and humidity control (Equilibrium Moisture Content of Wood)
« Reply #3 on: December 15, 2007, 01:06:23 pm »
All my wood stays in my basement in my workshop. I do most of my bow building in the winter when the r/h is way less. While working on a bow I stand it behind the wood stove between work secessions. I can usually tell by feel and sound if wood is dry enough to stress. My finished bows are hung in the utility room with the hot water heater and washer/dryer. 
   Most woods like 8%-11% m/c but hickory likes to be drier...more like 6%. Any other wood would blow with that low m/c.    Pat
Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline Sidewinder

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Re: Temperature and humidity control (Equilibrium Moisture Content of Wood)
« Reply #4 on: December 15, 2007, 03:01:51 pm »
Good question. I like reading the answers and storing them in my pea brain for later use. Danny
"You know a tree by the fruit it bears"   God

whatareyadoin

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Re: Temperature and humidity control (Equilibrium Moisture Content of Wood)
« Reply #5 on: December 15, 2007, 04:23:20 pm »
My hickory was 15 % when I got it. And my humidity is about 87%, Personaly I think a closet about 60 degrees works to maintain constant Moisture content but then I take it out of the closet and start working with it, That changes so as soon as I am done  making whatever I seal it with finish, if it works great if not I try not to have a temper tantrum. In Other words wood is unpredictable, Happy Christmas and a merry New Year.

Offline cowboy

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  • Paul Wolfe. Springtown, TX
Re: Temperature and humidity control (Equilibrium Moisture Content of Wood)
« Reply #6 on: December 15, 2007, 08:02:03 pm »
I get em to around bow demension's then leave in the house till I work em (central heat and AC) low humidity - usually for months. Beyond that I dry em further in my heat lamp stove pipe oven till they stop losing weight, don't have any idea what the M/C is at that point but am happy with results..
When you come upon a track or trail you do not know, follow it to the point of knowing.