Bowing Wood in Planer

[Jerry Moore]

Hello,

I am new at woodworking and have been working on some wood for several months. The wood has sat in my shop for a couple of months. My moisture meter shows the wood to be at 8%. My shop is an attached converted guarage with heating and cooling. We live in New Mexico and use evaperative cooling. Yesterday it was raining and I jonted several boards flat. I than set up my planer and ran one of the boards through the planer twice and by the second pass the board had bowed. I tried one more board to make sure it was not just a bad piece of wood and the same thing happened. Today I went back into my shop and one of the boards I had only jointed flat on one side had bowed also. What is causing this. I am affraid to touch any more wood until I know what is happening and what I can do to stop it. Any ideas what might be happening?

[John Keeton]

Jerry, my guess would be that the wood was stable as it was. When you removed wood it changed the ever present inner stresses of the wood. Perhaps you removed more wood from one side or the other - or one edge, although that would not be a prerequisite. Wood is rarely static, and any change in its structure is liable to change its equilibrium and cause it to move. I doubt moisture had much to do with it. Wait until you run an otherwise straight, flat board through your tablesaw and end up with two pretzels!!

[Peter Quinn]

You didn't mention which species. Some are less stable than others. The best you can do environmentally is keep your shop at as consistent a RH level as possible, preferably in the 40% range, acclimate your lumber and cross your fingers. I have pulled lumber from a pack that all moved around, quite possible the boards were from the same tree, even possibly sawn and processed in sequence at the mill.

[Jerry Moore]

Thanks or the replies. I am using QSWO. The wood bowed before I could flatten the face opposite the jointed side. I never hade time to take any off from the other side. Is there any thing I can do to keep the rest of my wood from doing the same thing.

Jerry

[Per Swenson]

Are we talking bowed or cupped?
Cupped would be like a C on its back along the end grain.
Bowed would be C on its back long end to end.

If cupped add moisture sparingly to the inside of the c.

Per

[Jerry Moore]

Hello,

It is bowing like a banana from end to end.

Thanks,

Jerry

[Frank Drew]

It is bowing like a banana from end to end.

Jerry,

That sounds (possibly) more like reaction wood than a moisture inequality caused problem; in other words, there can be internal stresses in a board, often brought about by the growth habits of that particular tree, that will express themselves by causing the board to warp once some wood is removed from the surfaces of the board.

[Jerry Moore]

Hello,

Is there anything I can do about it? If I try to flatten the boards again are they going to continue to move?

Thanks,

Jerry

[Dennis Lopeman]

I don't know how drastic it is, but i remember someone here mentioned how to do it... I tried it and it worked (mostly) - had to be planed again to get the waves out, but otherwise flattened.

They said keep it wet/moist and or lay it in the grass in the sun... I did both side of the wood until I was satisfied... only took like a day...

this may not work if it stress though. I think this resolution is for uneven drying...

[Dick Strauss]

Jerry,
I'd suggest you stop using a swamp cooler in your woodshop. This can cause the RH to go from 10% to 60% in a matter of an hour or less. The monsoons can also raise the humidity very quickly. Wood doesn't like this kind of environment (changing humidity). As you expose a fresh side after planing, that side will be more likely to draw in environmental moisture (from your cooler) and lengthen. If one side lengthens and the other doesn't, you get a bowed board.

As others have mentioned, the wood could have stresses being released as well.


Good luck,
Dick

[Peter Quinn]

Jerry,
I'd suggest you stop using a swamp cooler in your woodshop. This can cause the RH to go from 10% to 60% in a matter of an hour or less. The monsoons can also raise the humidity very quickly. Wood doesn't like this kind of environment (changing humidity). As you expose a fresh side after planing, that side will be more likely to draw in environmental moisture (from your cooler) and lengthen. If one side lengthens and the other doesn't, you get a bowed board.

As others have mentioned, the wood could have stresses being released as well.


Good luck,
Dick

Not to be a stickler here, but lengthen? Wood once kiln dried grows very little over its length. It moves mostly across the grain, which for true QSWO means very little movement. Plain sawn may seem to lengthen on the sap side if moistened but its really just the longer radial rings moving sideways more than those on the heart side. QS would tend to cup more than bow and usually cup in an irregular fashion, more on the sap side where the rings are less vertical.

QSWO is typically pretty stable stuff. White oak doesn't gain moisture very quickly due to its cell structure, but it doesn't lose it very quickly either which can cause problems at the kiln. Some processors may try to push it along a bit, dry it too quick. You mentioned the moisture was at 8%. I'll assume you took at least 3" off an end and took a measurement at both the face and core to achieve this information with a good meter, corrected for species and temperature?

I have used packs of WO, mostly I've had the problem with plain sawn in 5/4 through 8/4, where the wood was dried too quickly and a lot of stress was trapped in the process. Often there was excessive checking on the board ends too which is a tell tale sign that WO has been dried too quickly. We received it shortly after it was finished drying and the moisture was in the workable range, but the wood was simply not usable. Every little bit removed during milling caused it to move. One pass over a jointer and it would spring the other way, a light rip of an edge on a TS and it would bow or twist. Some times a whole 1000BF pack, sometimes a few dozen boards in a pack. Very tense though no indication in the grain pattern that it was reaction wood. Our solution was to sit on it. Let it hang out for a few years and relax. I'm sure that is not an answer you were hoping for and I don't know if it is the one to your problem.

I've seen similar problems from WO that was TOO dry, where the core was below or near 6%, the face (top 1/4" and ends) 8-9.5%. Expose that dry core and WHAMO BATMAN, it absorbs all the moisture it can get. Water doesn't migrate well through WO so it takes a long time to acclimate and stabilize.

If you told me maple bowed on you I'd blame the swamp cooler or the rain first, ask questions later. That may in fact be the issue but with QSWO I wouldn't assume it is.

Does this add anything to the conversation besides confusion?