Dumm question for the week

[tacks Y]

Will quarter sawn oak dry a lot slower than regular sawn  in a kiln? It has been a while and down only to mid 7s.  Thanks

[WDH]

I believe so because of the orientation of the rays.  In quartersawn, they run parallel to the face versus perpendicular to the face in flatsawn.  At least in my experience, quartersawn sure seems to be harder to get that last bit of water out.  The wood that has fooled me the most in drying is quartersawn white oak. 

[Southside]

Time to break out the chickens and candles.... :D

[Mike W]

Ok @Southside, your just trolling @WDH with the chickens and such, next you'll be asking about his bowl of grits, and did he purchase them with SGU's  :D :D :D

[Southside]

It's actually a highly recommend procedure for stubborn lumber, I am mearly passing along what I was taught by the RRRQS master himself.  If you can find him he has the answers you seek.  :D

[YellowHammer]

Not only will it dry slower, but it will shrink more.  

The board, not the chicken. 

[GeneWengert-WoodDoc]

The number we use is that true quartersawn will dry 15% slower than true flatsawn.  As already stated, the reason is that the ray cells help flatsawn dry faster, as the rays are a connection or provide a short passageway between the interior up to the faces of the lumber inflatsawn.

With a load of lumber, many pieces are rift sawn, so the bulk of the lumber dries faster than the true quartersawn as well.  So, when choosing kiln samples, we need to make sure that we have several true quartersawn pieces if we want to make sure all lumber is dry.  Yet, to avoid over-drying the riftsawn and flatsawn, we need to use an equalization setting near the end of the cycle before any true flatsawn pieces become too dry.  This equalization setting might be started five or more days before the expected end of the cycle.  In fact, for oak, it is suggested that the kiln never have an EMC condition under 5.5% EMC.

[tacks Y]

Thanks guys.

 Gene, so how do I do this with my solar kiln?

[GeneWengert-WoodDoc]

In a solar kiln, the humidity in He afternoon is a bit too low and in the late nighttime hours, a bit too high.  It balances to about 11% EMC IF YOU KEEP THE FANS RUNNING ALL THE TIME.  WE GET A BETTER BALANCE IF WE RUN THE FANS DURING DAYLIGHT ONLY.  The EMC is 7% average...perfect.  Vents are closed except for a tiny crack.

OK.

[tacks Y]

Thanks Gene. I need to be away for a week so plan to open vents all the way and just leave it. Right idea?

[scsmith42]

Not only will it dry slower, but it will shrink more.  

The board, not the chicken.

Yes but only in thickness.  In width QS shrinks less than FS.
Typically Flatsawn Oak will shrink 1/16" per inch of thickness, whereas QS oak will shrink 1/8" per inch of thickness.  Amounts are reversed for width shrinkage.

[GeneWengert-WoodDoc]

With fans not running, then vents maybe half open. Depends on vent size.

[YellowHammer]

Not only will it dry slower, but it will shrink more.  

The board, not the chicken.

Yes but only in thickness.  In width QS shrinks less than FS.
Typically Flatsawn Oak will shrink 1/16" per inch of thickness, whereas QS oak will shrink 1/8" per inch of thickness.  Amounts are reversed for width shrinkage.

Yes, many a QS board will not clean up to 3/4" because the sawyer didn't anticipate the shrinkage amount.    
It's a shame, but we get calls from folks who have had so and so sawmill up the road QS some oak and cut it too thin, and then no joy for the customer because the wood won't plane out due to the QS shrinkage.  They ask me what can be done, expecting some miracle answer, and I just tell them "cut it thicker."

If your wood is at mid 7's, I'd say take it out, it's done.  Put another load in and leave for the week.

[GeneWengert-WoodDoc]

Shrinkage values in the book are not perfect.  They are based on very thin pieces of wood.  The thicker the piece, the less shrinkage.

 Book values are tangential and radial, so are based on perfectly flat grain or perfectly quarter grain.  Lumber is seldom perfect flat or quarter, so the actual shrinkage is less than flatsawn and more than quartersawn values.

Slow drying means slightly lmore shrinkage due to less stress build up when drying.

Hot temperature drying has slightly more shrinkage than cooler.

Book values are an average, but, as might be expected, some pieces will shrink a bit more and some a bit less.

Within the red oak group, or white oak group, there is a large difference between species.  For example, red oak species range from 8.6% to 11.3% for tangential shrinkage, green to dry, which is the width of a flatsawn board or thickness of quartersawn.   White oak is 8.8% to 12.7%.  So, a white oak true quartersawn piece can shrink in thickness when drying to 6% MC,  0.070" to 0.102" (over 3/32") and red oak, 0.069" to 0.090" (3/32").

To clean up lumber when planing, we also need to consider cupping.

For each 3% MC drier, we can add about 1% more shrinkage.

BOTTOM LINE...IT IS NO WONDER THAT 4/4 QUARTERSAWN oak LUMBER IS OFTEN SAWN 1-3/16" thick so that it will clean up at 15/16" after drying with careful planing.