Drying large timbers

[Farrell]

Re: Drying large timbersDale,

I'm not an expert at wood drying, but I did air-dry my first couple loads of Sitka that I bought a few years ago. Some of the boards I have dried were two inches thick and some one inch thick. Whereas I was not able (no moisture meter) to measure the actual MC of the wood, I found that one-inch boards could be dried with minimal checking in just a month or so - dry enough that no additional checking occurred when brought into my 50% RH shop. Drying times for additional thickness is an exponential function. I had a formula for it, but can't find it (sorry).

With your local 30% RH levels - air drying without some method to slow the process will likely result in some degree of end checking (but maybe for crosses, that is not a big issue). My guess is that your 8-inch sections will require at least a year to come down to some reasonable MC - maybe a lot more - but your low RH is going to move the process along pretty fast also. Air movement through the stack is also a BIG factor in drying rate (and also in mold/fungi growth). 

Consider also your final construction method. How are you going to make the cross joint? Are you going to make it flat - i.e. cut a notch half-way though each timber? If so, then take advantage of Ron's suggestion and cut the wood into one or two-inch-thick laminations - the criss-cross every other lamination to make your joint - it will be very strong. And like Ron says, even if you aren't making the joint flat, cutting into thinner laminations and then gluing back up will hasten the drying process.

Or are you not going to glue the joint and instead rely on mechanical fasteners? If so, why even worry about the drying (although I guess you never know how much it's going to warp). I suppose you could assemble the cross any time after the darn thing stops dripping!

If I were building a big cross, I'd cut one or two-inch thick laminations and alternate the cross pieces making a flat joint and use pretty much any type of water-proof glue/adhesive to assemble.

Terry Farrell

PS: Sorry you and many others were not at NEECSO this past week/end - a great belly experience was had by all!  It was great seeing David Anderson.
  ----- Original Message ----- 
  From: Ron Overs 
  To: Pianotech List 
  Sent: Monday, April 28, 2008 1:11 AM
  Subject: Re: Drying large timbers


  Dale,


  The rule of thumb is 1 year for every inch of thickness. If you want them to season faster you may need to break them down into two or three slices, then glue them together once they've dried. This is why most piano makers laminate the back post and beams from three or more pieces. It saves them having a yard full of lumber which they've paid for, but can't use just yet. Furthermore, the greater the section size the greater the risk of checking during the seasoning process.


  Ron O.


      Hey all woodchucks
      We hav a project in progress at church which requires air drying Ponderosa pine.  I have section that are 8 inches square.  They were cut green in January & are now stacked and stickered in a barn drying. Our Humidity levels have been in the mid to upper 30% region. We will make replica crosses out of them & install them outside. SO how long will this take?
     My guess is by August they should be plenty dry
      What say yee oh wise ones
      Dale
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