Un-cupping some resawn 1X cedar

[Steven Cooper2]

A few years back I was making some mailboxes form cedar, re-sawn down to ~3/8 thick as if I left it at 7/8 it was extremely heavy.

Not doing that anymore but have a few 1x10's that have been re-sawn left that I'd like to do some birdhouses for scouts and such with, but they have cupped a bit as they dried, about 1/4-1/2 inch over the width.

Any way to use some moisture to pull that back into place?

Can I soak them and clamp them as they dry? maybe a little reverse cup?

[Maurice Mcmurry]

Dad has a trick for this using a wet sponge on on side and warm sunshine on the other. Then nail the board down quick. Quarter sawn AKA vertical grain is what I look for when I want thin wood, particularly if it will be outdoors. Reclaimed vertical grain redwood or western cedar siding is my go to for bird houses.

https://www.finewoodworking.com/forum/cupped-boards

[John TenEyck]

You can get them to flatten out temporarily, but they will cup again when it dries out. The way it dried is the way it's going to be unless you mechanically alter it by face jointing/planing, etc. To preserve thickness, it's common to rip the boards lengthwise, surface them flat, and then glue them back together.

John

[Carroll Courtney]

Maybe rip down middle, run across jointer then glue. Still will have cup but not as much. Run across jointer flat, then planer. I haven’t tried this myself, but sounds like it would work to where don’t have to remove as much wood

[Steve Demuth]

Depending on how many, and how much work you want to put into it, you can probably flatten them and keep them flat using heat. I've rescued a couple of pieces of air dried wood that cupped that had enough sentimental value for a piece to make it worth the effort, by clamping onto cauls with a just a bit of reverse camber, applying heat for a couple of hours, with a bit of moisture, before cooling and drying while still on the cauls. In the winter I've done this by propping them up over the woodstove in my shop. Could probably also be done in an oven.

(Coincidentally, Dave Engel's of Engel's Coach Shop, who has a marvelous youtube channel on the wheelright and coach building trade, was doing exactly what I describe in one of his videos with the woodstove in his shop on some horribly wound and cupped, very weathered, boards, just a couple of weeks ago. You definitely can soften and reset the lignin in wood, even softwood, with heat, even after 60 years outdoors).

[John Kananis]

I wouldn't really feel comfortable running material that thin through my jointer without a power feeder.

If you're cupped and at 3/8" already, I would consider first ripping through the center of the cup and using the stock for smaller things where you can quickly shape with hand tools and not loose much thickness.

Maybe rip down middle, run across jointer then glue. Still will have cup but not as much. Run across jointer flat, then planer. I haven’t tried this myself, but sounds like it would work to where don’t have to remove as much wood

Edit: rip it on the bandsaw, not tablesaw.

[Steven Cooper2]

I'll give this a shot. I figure if they get cut down substantially smaller the cup will be less noticeable and if it's nailed together it should be fine.

At least fine enough for some kids projects that are probably going to be smashed to pieces after a few weeks...

[Mel Fulks]

Maurice, I’ve done that too ,and it worked . Yeah, there might be some failures but sometimes when they cut chunks of diamonds
they break them and just use them for smaller stuff , even stick them on saws !

[Maurice Mcmurry]

I still have to stop and think for a minute about which side to wet and which side to warm. I will run thin boards over the jointer but only with upmost care and a pair of those grippy type push blocks.

IMG_1896.jpg

[Randy Heinemann]

If it were me, my normal way of resolving this would most likely be to rip the boards into 3"-4" widths on the bandsaw, joint the ripped boards to flatten one side, plane the other side, and glue them back together to make the width boards you need. However, if they are only 3/8" thick to begin with, I sincerely doubt you'd have even a 1/4" thickness left over. So this might not be worth it.

[Mel Fulks]

I still have to stop and think for a minute about which side to wet and which side to warm .

The water goes in the “bowl” and the heat goes on the bottom….it’s just like heating canned soup.

[Maurice Mcmurry]

The water goes in the “bowl” and the heat goes on the bottom….it’s just like heating canned soup.

Now that is an instruction I will be able to remember! Thank you Mel Fulks!

[Zachary Hoyt]

I've induced cupping and sometimes been able to remove it by laying a board on a concrete floor in a heated space in winter. The side on top will shrink and the side on the bottom will expand, so you want to orient them arched up to start with. The key is to look at them often and take them off the floor when they get back to flat. I had a board years ago that I cupped back and forth a few times and kept turning over before I finally caught it at the right moment. This works faster and better with thin wood, and I think it's the same principle as described above.

[Tom Bender]

Birdhouses need ventilation and birds have no expectations about construction standards. Time to get creative. Make wonky work.