Coffee table, and a question

[Kmucha16]

I was hoping to wait until this was done before I posted, but something came up with the project that I have a question about.

First off, I've been putting off building anything cause finding wood around here is tough, and expensive. So, when I found some old lumber laying around at a client's facility I had a chat with my contact and got him to give permission to take some stuff home.

In the wild:

   

Brought home and stacked:

   

That's a bunch of 11-ft long white oak boards. Brought home for the price of my time.

Wife wanted a coffee table so I built this:

   

   

Now, it's not perfect, first time doing mortise and tenon. But it turned out pretty good. These pics are before tapering the legs and gluing the frame.

My problem is the top. I expected some movement, but apparently when I built this over this past winter, in my unconditioned garage, there was significantly more humidity than there is now. I made sure it was dead flat when I glued it all up. Since then, the whole top has cupped upwards about 0.75 inch on either side. When it's raining, it flattens back out, but cups again later. I've since moved it into the house where it will be to see if acclimating it to its final resting place would be enough to flatten out. After a couple days, it's much less, but not flat yet.

Questions:
1) should I wait it out and see if it continues to flatten?
2) should I cut the top boards apart and either reglue, or not glue at all and have separate planks?
3) If it does flatten on its own, when I stain it and seal it with Poly, will that be enough to seal in the residual moisture and keep it flat? Or should I expect more movement as it gets hot here in the summer?

Thanks for the input.
Kevin

[wood-chips]

Nice score on the wood! That's a nice table too.

When you say "the whole top has cupped upwards about 0.75 inch on either side"
Does that mean at the edges or across the width of the table?

My first question is how did you attach the top to the base?
Did you allow for expansion / contraction in construction due to humidity?
Are the stretchers stiff enough to control cupping?

Others will come along with ideas/recommendations with a bit more information.
However, based on the information so far I'd favor the second part of option 2.

2) should I cut the top boards apart and either reglue, or not glue at all and have separate planks?

With this method you'll still have to leave room for expansion / contraction.

[Reverb]

3) If it does flatten on its own, when I stain it and seal it with Poly, will that be enough to seal in the residual moisture and keep it flat? 

Nope, nothing stops water, including epoxy and levees. Plan on it moving seasonally until there are no longer seasons...

[Cdshakes]

".... until there are no longer seasons."

Due to Global Warming?  I think that might take some time.  Hope this coffee table is built well!





Colin

[fredhargis]

That seems extreme, and makes me wonder how dry the wood is. But here's what I think: depending on how you fasten it to the frame, I'd bet that once tied down it will stay flat. Many might not want to take that chance, but I would. The fastening arrangement has to allow for the expansion across that width, so working out the solution may take some thought. What's your plan to hold it to the frame? Separate planks would solve the problem I think, since the stacked lumber doesn't seem to be cupped, but you' have to have a design that allows for the separate boards. Some guys (including me) rip the boards down the center and reglue them...but this is more often done with wider boards than what you have. I don't think resawing the glue joints (if that's what you asked about) and re gluing the top would solve the problem....it isn't in the glue joints. One other thing, a lot of guys advocate flipping the boards so that the bark side is up on one board, and then down on the next. I don't worry about doing that since I sometimes can't tell which is the bark side, and I always want the best looking grain on the show surface anyway.

[Kmucha16]

Thanks for the input folks. I appreciate it and it confirms a few of my thoughts.


The top isn't fastened yet. I was waiting to solve this problem before doing that. The initial plan was to use the 90 degree clips in a groove on the inside of the stretchers. Doing it that way with individual boards may be overly cumbersome. 

The current thought is to run stretchers inside the frame across the individual planks and individually screw them in from the bottom. This way I could give them a little space and they would be largely secure in both directions. Kind of a bummer as I was hoping to limit the fasteners, and I'd have to use pocket screws to hold the new stretchers in. Oh well, nobody else will notice it on the underside.

I suspect a large part of my issue was working this wood before it was really dry. It's been outside for decades and I had gross processed it and brought in the smaller chunks about 10 days before starting to mill it. It then took about a month of working on it here and there to get it where it is now. The only issue I noticed was after I glued up the top. 

I thought about flipping the boards but due to the grain patterns and defects, it turned out the best side was all one side of the boards, so there's no variation on those.

Looks like I need to get the bandsaw tuned up to slice the top apart.

Thanks all, I'll post pics when it's complete.

Kevin

[jteneyck]

I think it cupped up at the ends because the top dried faster than the bottom.  I'm sure you are right that the wood was not dry enough yet 

I would flip the top over so the other side has a chance to catch up and let it sit awhile longer to see if it flattens down to maybe 1/8" cup.  If it does, then you should be able to pull it down flat with the clips you are planning to use when you flip it back right side up and fasten it down.  Depending how much it all has to dry yet, it could take weeks/months before it's at equilibrium with your house.  it would be best to wait until it is before finishing it.  


John

[K. L. McReynolds]

A long time ago, when I was first starting serious woodworking, I bought a 4' by 6" piece of 6/4 bloodwood. It cost me a lot(for me) back then(something like $2 a board foot)sure wish I could get it for than NOW!!). I did not have a band saw, so had to resaw with my TS. I know, cringe! I sawed a piece about 1 foot long and 1/4" thick, allowing for sanding the saw marks out(no planer either).

Had to quit and came back the next day to find I now had a U shaped piece of bloodwood. Seriously, there was a 1/2" bow across the width! Man! Was I crushed!. I kinda lost interest in the project. About a month later, I was cleaning and uncovered the piece of bloodwood---which was now flat!

Just an example of how wood cups when resawn or planed. Don't give up, all that has happened is a delay.

[MstrCarpenter]

I suggest exposing the convex side (bottom) to sunlight on a dry day. It will probably start to cup the other way. If it does, mount the top (allowing for expansion) and keep it in the house for a week. If all is well you can finish at your leisure. Just make sure to finish both sides exactly the same. Depending on humidity and time, you might need to help it flatten again.

[FrankAtl]

I think it cupped up at the ends because the top dried faster than the bottom.  I'm sure you are right that the wood was not dry enough yet 

I would flip the top over so the other side has a chance to catch up and let it sit awhile longer to see if it flattens down to maybe 1/8" cup.  If it does, then you should be able to pull it down flat with the clips you are planning to use when you flip it back right side up and fasten it down.  Depending how much it all has to dry yet, it could take weeks/months before it's at equilibrium with your house.  it would be best to wait until it is before finishing it.  


John

^^^^ This would be my suggestion too.