Don't know what happened


Chet
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I have a panel for a project that I am working on.  It has been milled to the point you see in the photo for 5 - 6 days.  I worked with it yesterday fitting the pieces that go in the slots and taking some measurements for the sides.  Through all of this everything has been fine.  Today when I went out into the shop to continue, I found it in this bowed state.  It is setting right were I left it last evening.   There is also a similar piece that has a bow in the opposite direction.  I am in Northern California and don't usually have things like this happen.  I don't ignore wood movement but it isn't a big concern like some of you deal with in other parts of the country.  The only real difference is that it has been 10 - 15 degrees warmer the last two days compared to the rest of the week.  

Any thoughts?

IMG_5630.jpg

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Check the moisture on both sides if you have a meter. I would flip it over and add some weight & see what happens. Is the piece going to be held flat by joinery when the project is completed?

Did it bow after the grooves were cut? That might have released some stress in the board.

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That wood today has so much stress in it from being kiln dried overnight that you never know what it's going to do, but it's almost guaranteed to move.  Pine, with that much flat grain in it, will always cup over some period of time.  Kiln drying overnight means that it will move overnight.   Air dry it, and it might take decades.

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Yeah I'm with Tom...I don't think it has as much to do with moisture as it does tension.  Cutting the kerfs on the one side released tension and it cupped.

Also, if you left that board laying flat like that overnight, that didn't help.  Always sticker before turning the lights off.

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That's what I would expect in my shop right now.30+ degree temp difference from day to night.

The only chance to keep it flat would be cover it on top with a thick plywood and good weight.Either good air flow all around or no air and pressure to keep it flat.

Its about 110 in my shop right now even my dry wood is drying:huh:

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26 minutes ago, Chet said:

The piece that is cupping in the opposite direction has the same kerfs.  The kerfs have been there 5 days and it just happened over night.

Do you mean opposite direction relative to the way it's laying, or opposite direction relative to the growth rings?

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18 minutes ago, Tom King said:

Do you mean opposite direction relative to the way it's laying, or opposite direction relative to the growth rings?

If I were to lay the other piece next to the one in the picture, both with the kerfs up, they are bowing in opposite direction.  The one in the picture the high point is at the edges the other is high in the center and there is a third that is still dead nuts flat.

1 hour ago, wdwerker said:

I would flip it over and add some weight & see what happens. Is the piece going to be held flat by joinery when the project is completed?

Yes, there is a sides, top and bottom that will have a rabbet all the way around that this will set into.

Mid-week humidity was around 25 - 30 precent, today it is 10 percent.

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The growth rings are the same direction on all three panels.  They are all made up from the same two pieces of wood.  I glued each panel up separately but if I layed them end to end it would look almost as if I glued one long panel and then cut it in thirds.  They go flat real easy when I press down on them.  I have some weight on them now and won't get back to them until next Sunday and we will see what happens.  I am real sure the rest of the project will hold them flat, it was just puzzling to have them fine for five days after milling and cutting the kerfs and then to have them bow over night.  I measured the bow on both and it is a weak 3/32 of an inch.

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22 minutes ago, C Shaffer said:

 

Never leave it lay on a bench.

 

No doubt this was my big mistake and I have learned my lesson.  But my curiosity lies in the fact that I left it in pretty much the same place every night during the week and then last night it bowed.

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28 minutes ago, bleedinblue said:

My curiosity lies in that each board, with the growth rings pointed the same way relative the cuts, all bowed differently.

Yep, that is why I posted.  Actually one of the three didn't bow at all. :o

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Just curioius ... (if the back is to be hidden) might offset cuts on the back side relieve the tension and allow it to flatten naturally?

Then again, isn't this the very reason large surfaces are made by joining multiple smaller boards and alternating the grain? For lack of conventional language, it seems that boards tend to bend to the curve of their gran, which also make quarter & rift sawn wood more desirable. Correct?

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