The Forestry Forum

General Forestry => Drying and Processing => Topic started by: JRHD on January 17, 2019, 12:25:03 PM

Title: Dose size matter?
Post by: JRHD on January 17, 2019, 12:25:03 PM
Would you use the same moisture content schedule to dry random width & length 8/4 walnut as you would dimension stock?
8" x 16" x 2 3/8". I get very little h/c in a 30,000' charge of 8/4 but will see 5 to 6% h/c in a charge of 35,000 pieces of the dimension. The dimension pieces are defect free, waxed on both ends, and have sticks every 5".
Title: Re: Dose size matter?
Post by: GeneWengert-WoodDoc on January 18, 2019, 03:49:45 PM
Short dimension pieces have more surface to volume, so they dry faster, which means more risk.  Also, Dimension can have a defect an inch or two from the end, but this defect was cut off.  Overall, this means cross grain at the end of a dimension piece, which again is more defect prone.
Title: Re: Dose size matter?
Post by: JRHD on January 18, 2019, 04:26:19 PM
Thanks for your input. I forgot to mention that in both cases I am talking about walnut.
Title: Re: Dose size matter?
Post by: YellowHammer on January 18, 2019, 08:25:20 PM
As said, the higher the relative surface area, the more forgiving the kiln schedule must be, especially if starting higher than the fiber saturation point.  I don’t go as conservative as a 4/4 schedule, but certainly dial it back a little whenever I’m drying small chunks, especially high value walnut.  I will also run cooler temperatures, and try to get to the characteristic “walnut stall” point, then I increase the temps, and then finally drop the wet bulb.  

I assume you are using a steam kiln?

  
Title: Re: Dose size matter?
Post by: JRHD on January 22, 2019, 04:58:24 PM
Yes steam kilns. These charges are pretty green. Usually start in the 70 to 80% moisture range. I start with a 4 degree depression and stay a step behind where 8/4 would be for any given moisture content. These are mostly all plain sawn with little to no figure.