Board Width and Panel Stability

[Pwk5017]

This came up in a relatively recent Wood Talk episode, and I have seen a few threads here and WoodWeb that brought this topic up. Matt and Marc made it seem like growth ring orientation were irrelevant to overall panel stability. Their argument made sense that properly dried wood shouldnt warp/bow/whatever if properly handled anyways. Next, I read a few threads on Wood Web(this is mostly pro forum) where a guy had a panel cup on him, and everyone berated him for using 7" wide maple boards. Two parts to my question, does growth ring orientation affect a panel and are wide boards doomed to ruin a glue up? Growth ring orientation makes sense to me if the panel is subjected to humidity changes, so I will continue to do so. The board width thing to me doesnt make as much sense. I get that wider boards typically have more tension or stress, but i was shocked to see people freak out over 7" wide boards. I routinely work with 7"+ wide material, and havent had problems yet, but certainly cause for concern. Do you flip flop growth rings? Do you avoid wide lumber?

[Pwk5017]

28 minutes ago, Mike. said:

Unless you live in area of nearly constant EMC, all wood moves.  Build to deal with it.

 

Yeah, Im not arguing with movement, im concerned with movement resulting in warpage/bow. In the Wood Web case, the guy made a table top or island top. In any case, he just made a big wood panel and movement was accounted for, but the thing still bowed. Furthermore, If you produce a panel from stable, well dried material, that is dead flat and then it is exposed to greater or less moisture, what causes it to warp other than the orientation of growth rings?

[Eric.]

I find the "alternate growth rings" thing to be rubbish.  All else being equal, I will orient them in alternate, but I will not sacrifice grain match to do it.  It's way down on the priority list when I'm putting together a panel.

Also, a 7" wide board is going to only be a fraction flat sawn, with the majority being rift sawn to quarter sawn.  The flat sawn is really the only material that I worry about warping much.  And since I use properly milled and kiln dried lumber, I don't worry.

Most panels large enough that you'd worry about movement...they'll be forced into flat by something else anyway, be it a frame or just held down with screws like a table top would be.

In summary, I think alternating ring patterns is probably technically best,  but in practice it makes very little difference.

[Unknown craftsman]

I think it has more to do with the wood species than growth rings. Maple is one of those wood that needs to be milled and used the same day.Ya just can't let it sit out on your bench for a week or couple days and expect it to still be flat.

[Janello]

I've had 3" wide pcs of purpleheart cup and 24" pcs of mahogany not cup. I think it's how well it was dried, what MC it is, what kind of tension was in the board, how you milled it. That's why it's always a good idea to mill in 2 stages, so you can see how it's going to react. I don't think a wide board has any more chance of cupping than a small one if all those factors above are par. 

I find it's evident pretty quickly when I start a project if the wood will be fussy. My purpleheart little jewelry box caused me fits...while a large cherry coffeee table was stable as can be. Just the way it goes.

[Pwk5017]

Maybe I need to clarify a bit. One, My question is posed more towards massive panels 36-48" by 72-96" like table tops etc. Im by no means looking to buck the system and prevent wood from moving; however, i do what to understand the best way to construct things for stability. It seems like Wood Talk and this forum believes that properly dried and stable material will never cause problems no matter what RH it is in. Similarly, i think we would all agree that 7-12" wide boards in a panel arent a bad thing. I guess what sparked this is the opposing ideologies between Marc, Matt, and Shannon(experience WWers in their own right) and the guys at Wood Web who are grizzled professionals, in most cases. These guys were stunned to hear that the troubled OP made his counter out of 10/4 7" boards and how they would have never taken that job. It sort of turned everything I knew on its head. As I read it, I was thinking, '7" wide boards? I do that all the friggin time!'. You all seem to be reinforcing what I practice and what I know. 

[h3nry]

Mike 's post above pretty much seems to cover it.

As I understand, there are two reasons boards cup due to moisture:

1) One side of the board is exposed to higher moisture than the other.  proper drying, milling and air-flow should keep this under control

2) Because wood expands more tangentially (around the growth rings) than radially (across the growth rings), so even with an even moisture change on both sides of the board it will still cup slightly if the board contains a significant curve in the growth-rings. Wide panels should either try to minimize this by paying attention to the growth rings, or be able to force a panel to stay flat by proper joinery and design. With 4/4 boards it seems the experience expressed in this thread is that the latter is usually good enough.