Poplar stress

[PA_Walnut]

Sawing some poplar yesterday (wide 5/4) that had a few minor stress cracks on either end (not both).
So much stress that when I took the board off the cant, it checked a couple feet and some took off  about 10 outta the 12 feet of length.

I couple I sawed the next board to see and some did the same, others not. The next log, I rolled it and cut the other way, and again, some did and some didn't.

I don't saw a lot of poplar, so it's not familiar to me. Do I need to revise my technique or just the nature of the beast. Thanks in advance for an tips or wisdom.

[samandothers]

I have battled poplar and I think we are at a tie.  Many logs have a lot of stress and bow when or worse the can't will raise off the mill and I'll aboard thicker in the middle.  I think I am not rotating often enough. 

I have only had cracking or splitting show up as it dries.  These are usually in boards near the pith.  I am cutting trees cut from the side of a hill and near the edge of the wooded area.  I assume my issues are related to stress that shows up as it dries.

[WDH]

That is the way yellow poplar is.  I found that logs less than about 16" on the small end have the most stress.  The really big ones behave much better.  Small logs can be awful. 

[PA_Walnut]

Thanks for the sanity check. They are unwieldy for sure. I have some really big ones that I plan to QS. That may help.

The problem logs were in the 20" range or so.

[opticsguy]

I cut poplar (cottonwood ) up here in Washington state. Certainly not my favorite but it is the wood i have available to me.

I was cutting a 16" diameter log yesterday and as I cut 2x material the whole tree/beam continued to reshape itself during each cut.  This required an additional "leveling" cut between each board. 
Some cottonwoods will not move at all and some seem to almost explode on the mill.  I had cut some 2x material many months ago and several of the 2x6 boards warped so much they bent almost 90 degrees in a 16 foot length. 

As always, have fun!!!!

[Ron Wenrich]

Some tulip poplar has spiral grain.  You can see it in the bark, as it seems to twist around the tree.  That gives it added stress.  Some is more pronounced than others.  Might be part of the reason. 

I never had too much problem with poplar splitting like you're talking about.  I've had it with ash.  I've probably sawed about 20 MMbf of poplar.  Some of them really big.

[Magicman]

Pay very close attention to the log ends and note the direction of the pith checks.  If you are turning 90° be sure that the largest pith check is perpendicular to the sawmill bed on the first face opening.  This will put it parallel to the bed on the saw-through which will minimize the boards splitting.  Not eliminate it, but minimize it.

[PA_Walnut]

Thanks for the tips. I was paying close attention to the checks and rolling the cant more often. Still got some checking, but not wicked ones like before. I do know that the trees all came from a hill, so probably grew with some stress.

Also noticed some of the spiral twist that Ron mentioned. I guess it's just the nature of the beast.

Thanks again.

[Don P]

Where does the stress go when the tree gets bigger?

[WDH]

It is the juvenile wood that splits and has the most stress.  The larger the stem, the greater the proportion of mature wood to juvenile wood since the size of the juvenile core is fixed. 

[YellowHammer]

Pay very close attention to the log ends and note the direction of the pith checks.  If you are turning 90° be sure that the largest pith check is perpendicular to the sawmill bed on the first face opening.  This will put it parallel to the bed on the saw-through which will minimize the boards splitting.  Not eliminate it, but minimize it.

Sawing pattern and knowing the desired end product is a great way to optimize the stress in logs, not just poplar, but other higher value, high stress species such as walnut.  If sawing for flatness, i.e. no bow, then mill perpendicular to the stress crack.  The boards can be edged or straight lined later, but will not have to be face jointed.  The boards will curve outward but will remain flat.  If sawing for high yield, then mill parallel to the cracks and trap them in one or two boards.
Of course other techniques also help, such as minimizing pith, minimizing sapwood, proper cant rotation, and holding your mouth just right. ;D

[Percy]

Where does the stress go when the tree gets bigger?

As the tree gets larger/older, it can afford to take a vacation once in a while helping relive stress considerably 🤓

[Don P]

So if you rotate the log removing the jacket, once you're down to a 16" cant, the stress is the same as in a smaller log? The log again acts as a smaller log?

[WDH]

Depends on the pith and the location of the juvenile wood.