HELP!! Really Need Your Suggestions on Warped Top

[joseph j shields]

I’m making a shaker writing desk for my church auction and I’ve run into a problem & I have to finish it this FRIDAY

The table top is 22” x 48” (made from 2 11” pieces of highly figured maple)
Because of the width of the boards, I let them acclimate to my basement for 4 weeks. I edge glued the boards with grain up-grain down. The top was perfectly flat.

I laid the top on my bench and over the past 4 days applied 4 coats of water-based poly to the topside (but not on the bottom side… I planned on getting the topside done first)

Last night I turned the top over to finish the bottom side and noticed the top had warped about 3/8 inch over the 22” width L. (when the top is on the desk, it is higher in the middle) The warp is constant… each board warped the same.

The auction is Friday night & I don’t really have time to find wood-glue-finish a new top.

SO here are my questions:

#1. What should I do? I can push the warp out. Should I tighten it down to the aprons (which are ¾” x 5” x 18” cherry) … should I saw some kerfs on the bottom to relieve the stress ??? (Size depth, spacing??) Any other ideas????

#2. What could have caused this??? Did the water-based finish on just one side cause this?? Any other ideas???

Thanks for your help!!!


-jj

[Ian Abraham]

Thats the reson you HAVE to finish both sides....

The warp is cause by uneven mositure, either from your finishing or just from the weather changing.

Good news is.. it should get better. Flip it over and finish the other side. By the time you have done that the moisture gradient inside should have evened out and the top should be close to flat again.

Then fix it to the aprons with your choice of sliding connector and pull it flat, it will be fine.

Cheers

Ian

[Gary Keedwell]

If I'm reading you right you spent 4 days putting a finish on one side only?

Your moisture and stress only had one way to go because you sealed the other way off. I bet you don't do that again, heh?
Well, I don't know what to advise, on such a short time frame, but I'm sure someone will post something to help you out. Good Luck!
Gary K.

[Howard Acheson]

As others have said, you caused it to warp by first placing it on a solid surface where air could not get to the bottom. Second, and because you uses a waterborne finish, you wetted one side which cause an imbalance in the moisture content between the up side and the down side. Any board or panel will warp given those actions.

As said, there a good chance that most of the warp can be removed by finishing the other side. But, be sure not to just place the panel on another solid surface. Raise it up so that air can get to both sides and/or stand it on edge so that air can freely circulate around it.

[Jim Becker]

As the others have stated, get the bottom finished and then use the supporting structure to bring it flat, being sure to allow for wood movement in your fastening method.

[Andrew Williams]

You can also use battens if the apron is not stiff enough.

[ROBERT ELLIS]

If you have access to a biscuit joiner you could make some slots on the inside (at the top of course) of the aprons, pull the top down with clamps and fasten it with table top fasteners. With a bow that great I would probably put my fasteners a little closer to each other than I normally would.

One other tip...the cherry furniture shops around these parts (and they have been making repoduction furniture for decades) all of them without exception, ***screw*** all of their tops to thier respective aprons, i.e., from end tables, to dressers, to dining tables. Realizing of course this goes against the "proper" way we've all been trained to attach tops. Their secret is they make the screw hole in the apron slightly larger than the screw itself, thereby giving the top a little room to move when it needs to. An older friend of mine that has been making and selling this style of furniture for 30+ years does it this way and don't know why I spend the extra money and use table top fasteners when it's much cheaper and less time consuming to use the screws. When I think about it, I don't really know why I use the fasteners other than old habits are hard to break.

If you opt to use the screws in the apron, here's pretty much how they do it. They drill the oversized screw at a slight angle through the top of the apron only. Then where the screw comes outof the apron (about an inch down, obviously on the inside of the apron) they drill a shallow hole (larger than the screw head) to accept the screw head. Then its just a matter of attaching the top to the apron by screwing it down.

As I mentioned, we've all been trained differently than this and most would be reluctant to do it this way, but I will say, the technique works, and they rarely, if hardly ever have any call backs from tops separating because of stress, my guess would be if they did, they would altogether abandon this technique.

Good Luck!

Robert

[joseph j shields]

Hey guy...

Thanks for all your advise.

I used your ideas and finished the piece.

Here are some photos & details....
http://www.sawmillcreek.org/showthread.php?t=57392

Thanks again!!!

-jj