Moisture Distribution in Western Canadian SPF, and pre-sorting

[R Kiesling]

What would be a typical range of standard deviation in correctly dried SPF?  I would imagine this would be impacted by the percentage of each species in a kiln charge.  Is much pre-sorting done in Western Canadian mills to deal with possibility?

[Craig Jensen]

We sort the Alpine fir out and dry it separately
our SPF is actually Engleman Spruce and Lodgepole Pine.  We see deviations between 4.2 and 2.9.
We are a stud mill and do up to 9' long, 2x3, 2x4, and 2x6.  Typically from less than 20' diameter logs.
Hope this helps.

[PhilM]

One thing to keep in mind is that the standard deviation is going to be impacted by the actual final moisture content. So, a higher average final moisture content is very likely to have a larger standard deviation than a lower average final moisture content.  Hence fir dried in the same kiln with pine and spruce will be wetter and have a higher SD (within the fir) compared to the SD for each of the other species, as well as making the SD of the total kiln high.  The species mix will have a large impact, as you suggest, since the spruce might dry (fastest) with a SD of 2 to 3, the pine might be slower drying since it is denser and hence have a higher SD of about 5, but then the slow drying fir might have a much higher SD (say 9 or 10). 

I cannot speak to the status of sorting today, but years ago a large manufacturer decided not use weight sorting for SPF.  Of course one concern is that if you do sort, how does it impact marketing if sorting impacts other properties (eg if the customer buys SPF that is actually all fir, will they be happy? Or, if all my dense lumber goes into one sort, is that a good or bad impact?)