DaveVman 10th October 2016, 10:32 PM So a bought a 285mm wide x 19mm DAR clear pine board from Masters to do my first little project. Something the wife wanted. 285mm wide would be perfect.
I took it into the workshop and left it face down on the table for a week. All ready to work on the following weekend.
Came back to start on the project and the board is already warped!!
Cupped.
No doubt something about change in humidity/temperature that I barely understand and can't control.
So I've been using it as scrap to try out a few things since I'm learning.
However if I buy another board, I image that same thing will happen.
It looks like all that DAR stuff in big box stores, is all plain sawn, not quarter sawn. Although I'm no expert.
I don't have a jointer or a thicknesser.
I could hand plane it 'flatish', if I can figure a way to clamp it down - but the point of buying DAR was to not need to do that.
What is a bloke to do?
Kuffy 10th October 2016, 10:55 PM No doubt something about change in humidity/temperature that I barely understand and can't control.
You kinda can control it. Leaving a board face down on a table for a week exposes one side of the board to the atmosphere while the face down side is relatively protected. So the exposed side will either take up moisture or release moisture at a different rate to the face down side. To prove the point quickly, leave a board face down for a while in the sun. The side which takes the beating by the sun will dry out and cause that face to shrink and become the concave face of a cupped board. which is exactly how you might be able to flatten your cupped board. place the board with the convex side facing the sun. watch it like a hawk because it rarely takes long.
When I have perfectly straight machined boards to an exact size but need to do other things for a few days, I will put those boards on a flat surface (usually one of the carpeted spare rooms in the house) covered in plastic all around, ideally inside a black garbage bag out of direct sunlight. They usually stay nice and flat, or only give minimal movement.
Chief Tiff 10th October 2016, 11:28 PM Unfortunately all the DAR pine in the big stores is rift sawn cheap pine and will almost certainly cup. If you plane it flat, in a week it'll have cupped again. There are ways to reduce it though.
Firstly look really, really hard for quarter sawn boards; the wider the board the more chance it'll have been ripped from the centre of the tree. Then rip out the centre section with the heart and reglue the remaining pieces, so in your case I would have looked for a 300mm+ wide board and cut a bit out of the middle to get the 285mm width.
Or, build your board from smaller planks jointed together, just alternate the grain direction between planks. Again; try for quarter sawn boards and cut out the heart if it appears in the plank.
Alternatively you can buy boards made from finger jointed pine strips; these are as stable as you can get with pine.
What's the project?
auscab 11th October 2016, 08:12 AM If you buy another board when you get it home lay it flat on the bench or floor and cover it with other boards until you want to use it . Or roughly cut it to the lengths you need and lay them flat on each other ,then find something else to cover the top one .
joe greiner 11th October 2016, 02:37 PM If the board is to be used with a good side showing and the other hidden (as well as the ends), you can effectively flatten it with multiple saw kerfs part way through. The remaining thinner part will be flexible enough to lie flat when attached to supporting framework.
Cheers,
Joe
Chris Parks 11th October 2016, 11:56 PM Wet the concave side and place the wet face down on the floor and it will flatten out, how close to flat depends on your patience. I use a spray bottle and damp it down to see what effect it has. I have seen badly cupped boards straighten in under 30 minutes so it is a good idea to keep an eye on it.
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