internal collapse in 8/4 QSWO lumber, questions

[Kelvin]

Well, maybe some of you thought this might be coming.  You might remember me wondering how i could get out of buying a scale and measuring the MC of the wet lumber?  Well, some thought i was being cheap.  By the time is spent $29.99 at office Max pn a scale i was at 40%MC, this is what happens...









Now my question is does this type of internal collapse telescope out or stay put.  The lumber is pretty well dry at 7-8%MC.  Should i expect this to move?  I am making stair treads for a customer, and i've been dripping super glue in them on the exposed ends to try make sure they don't move from my woodturning background.   For those of you not familiar with this type of kiln drying problem this is a big one for white oak when its dried to quickly in the beginning.  It is usually 80%MC when green, and should only be allowed to loose a max of 2.5% MC per 24hrs according to the Nyle kiln manual.  I believe my kiln was built a little too leaky as i followed a conservative schedule and still had this happen to about 50-60% of 1000 bd ft 8/4 quarter sawn white oak, maybe a couple thousand dollars worth of lumber....  Live and learn, i guess i have to always touch the hot stove to know what "hot" means.

Any thoughts?
Thanks
kelvin

[beenthere]

Kelvin
Check out the kiln operators manual

http://www.fpl.fs.fed.us/documnts/usda/ah188/ah188.htm

and in particular Chpt 6, figure 6-4, page 10 and thereabouts

and also Chpt 8, figure 8-7

These parts of the manual may help you evaluate how much damage is done.

[Gary_C]

I would call that internal checking rather than collapse. It can certainly be caused by too high of temperatures, but the primary cause is drying the outer surfaces, especially the ends too fast while the centers remains too wet. It's extremely hard to prevent in 8/4 oak in any kiln, regardless of temperature. Even if you did end seal all boards, you probably would see that type of internal checking. Vacuum kilns are supposed to do a better job on thick oaks and especially the white oaks.

You can do some equalizing of internal stresses and get those checks to close up, but they will still be there.

Not sure if that board is suitable for stair treads the way the grain runs. You could see some cracks eventually show up on the lower surface where the grain runs out at a flat angle. But if it has not cupped or twisted by now, it may not.

[low_48]

Is the customer going to stain the treads? I once bought some 8/4 red oak, real cheap, with the same cracking. I made a couple of beds from the stock. It was in my staining days (only natural finish now), so on went the stain. The cracking was basically invisible. Since the cracking is on the ray fleck, that also helps disguise it. I say go ahead and use it. The guy could have an elephant walk up those and not have any problems.

[SwampDonkey]

Looks like honey combing to me. The outer layers of the wood dried too fast to below FSP and the greener core collapsed. Your dry bulb temperature was too high before the free water was removed from the piece. It doesn't usually check all the way to the surface and is not a defect under hardwood grading rules.

[source: Textbook of Wood Technology, 4th Ed, 1980]

[Den Socling]

I would call it honeycomb also, but here is my theory on cause. If you dry the shell too much, it sets it's size and shape over a swollen core. Then when the core dries and shrinks, the stress causes the wood to tear at the rays. It is a bad defect in my book because you can't see it until the wood is machined.

[beenthere]

Agree with Den, cause he knows. 

[Kelvin]

Howdy,
Thanks for the info.  The machining has been done, and i've been able to hide the bad edges during glue ups as none of the honey combing was noticeable on the outside edges, mostly in the middle.  Any thoughts as to how stable it is?  Will i hear about cracks coming through in a couple of years?  Any experience in using this stuff?
Thanks
kelvin

[SwampDonkey]

I'm not sure the explanation is any different.   To me, not really, but to others ...well maybe.  

But as to your further question on whether the wood will worsen,  I've not personally used honeycombed lumber myself. So pays your dime, takes your chances.

[Ianab]

I haven't used Oak, but the Bluegum eucalyptus that grows here has exactly the same problem.

The usual strategy to handle it is to quarter saw, so the internal checking remains inside the finished board. If it's flat sawn the cracks will usually show on the surface, but q-sawn, it's like your picture.

Once it's dry it seems stable, I doubt it's going to split more in out lifetimes.

Ian