Best way to counter cup?

[Kevin Smira]

Tried searching, but that's a lot to weed through. I just bought a really nice pc of sapele. It was quartersawn and was about 1/4" shy of 11' long and right at 19" wide, I bought it for my upcoming dining room table project. Went to get cherry, but couldn't pass up the sapele. It's just georgeous. A uniform 1" thick and already planed both sides. I had the lumberyard cross cut in half. I put it in the back of the pickup and drove home in the sun about 2 hours. Once I got home, I noticed that it had a slight cup in both pieces. One pc is not terrible in that the cup is about 1/4" "out of flat" while the other is about 1/2" out. So, my options include letting it stabilize or ripping the board in half (or more pcs) and planing it out. I don't want option #2 because I want to keep as much of the 1" thick as possible. So, I'm perfectly fine with letting it stabilize as my daughter has a table already. So, all that to ask...what's the best way to allow the cup to return to normal? I've read to place it back in the sun, put it inside, etc. currently, it's inside leaning against the wall. Is this the correct/best way, or should I lay it flat and sticker it, let each pc lay flat? I've got plenty of room inside the house in a spare room to let it stabilize and time is not of the essence.

Thanks,
Kevin

[Mel Fulks]

Sounds like you are not ready to use it. I would store it out of sunlight ,with air on both sides: each board leaning against the wall. When you are ready to use it take most of the wood off the convex side. That usually make the wood react by actually moving flatter.

[pat warner]

Not what you want to hear. But I've never flattened anything with sun or water tricks.
I had to re-mill or scrap.

[John K Jordan]

I've had somewhat different experience and have flattened a lot of cupped boards, pine, oak, cherry, etc. Persimmon and dogwood, not so much.

- Maybe the difference is how long the board has been warped?
- Perhaps it makes a difference whether the lumber was air dried or heated/kiln dried. All my experience is with air dried lumber, most I've sawn myself.
- I also imagine overall dryness of the board would make a big difference. Air dry equilibrium around here is 12-15%.
- I suspect the species probably also makes a difference.

Kevin, the first thing I'd do is use a moisture meter and check the moisture on both sides. If the boards cupped towards the sunlight that side is probably drier than the other. Two hours in the sun is a long time...

If the cupping is from one side drying out too much I lay the board flat in the sun. I have done this many times with rough lumber I use in the shop or around the farm and it usually doesn't take long. I usually put the cupped side directly on the ground (on gravel) to add a little moisture to that side but I would hesitate to do that with nice planks of sapele. Once fairly flat I take them inside, allow to acclimate, then mill as needed. I have no idea if this would also work for your specific boards.

(I've also used the sun method to dry green 4/4 eastern red cedar when I was in a hurry to use it. Lay out the rough-cut boards directly from my sawmill in the sun on my big trailer until they barely start to cup, flip them over and wait until that side just starts to cup, then repeat. It doesn't take long before cedar is dry enough for my use, flat, and stable.)

I have learned to wrap lumber in tarps to keep out of the sun and weather. Hauled some big slabs that way from PA to TN in the back of the truck not long ago.

JKJ

[Wayne Lomman]

Set the boards up so you can wipe the concave side with a damp rag every now and then until they are straight. It will take a bit of time but it will work and you will be able to control what happens. Once they are straight you need to sticker them to hold them straight using decent size sticks and clamps. They won't stay straight without help. This is why half the effort in table making goes into keeping the top flat. Also putting it back in the sun is too severe and changes colours. Again much of the effort in polishing is to protect timber from the sun. Cheers

[Mel Fulks]

I think the add water type fixes work best where there is "compression ring set" on table tops that have been wiped off with damp cloths over time. The remove wood from convex side often fixes and never makes the problem worse. Way under used mainly because of liability fears of jointer manufacturers.

[Wayne Lomman]

Wetting one side has worked for me on many table tops where the tops sit around the factory for some time before completion of the job. In a batch of twenty or so you always get a cranky one. It works for mahogany, oak, pine or whatever. I haven't used it on sapele as that is not generally a furniture timber in Australia.

The technique does not pretend to replicate any natural process. You are simply swelling one side artificially and then holding it straight while it dries.

Leaving the timber to sit for a few weeks and then dressing it flat again is an option but would leave a half inch thick table top which is a bit light on. Cheers

[Scott Dorrer]

Convex side toward the sun has worked for me many times over the years. Laying the lumber on the grass will also help as it will introduce moisture evenly to the concave side.

[Brian Holcombe]

Stand it up for a day or two, it may relax on its own. I recently sawed some Honduran mahogany to thickness, the off cut turned into a salad bowl..so I chucked it into the junk pile. Surprisingly enough, a few days later it was nearly flat again.

[Larry Copas]

.It was quartersawn and was about 1/4" shy of 11' long and right at 19" wide.

Seems odd to me as true quarter sawn seldom cups. Could this be a sawing defect that you didn't notice?

[Kevin Smira]

Seems odd to me as true quarter sawn seldom cups. Could this be a sawing defect that you didn't notice?

Yeah, that was my thought as well. When I went back and looked at the grain, it's actually rift sawn. I pulled a pc of 8/4 out of the same bin that was QS to show the wife what I was talking about and took it from the "salesman" who said it was QS. No biggie...still a nice pc of sapele...