sliding dovetail to prevent warp?

[Mark Vaughn]

I am making an 11' long 2 1/2" thick bar top out of old pine and i was wondering if putting in sliding dovetails in the bottom of it would prevent warp? any suggestions? i'm kinda thinking that if it wants to move it won't be stopped by some these little dovetail rails. thx for any input

[Sam Yerardi]

If you are talking about dovetails at right angles to the direction of the grain, then sliding dovetails should work insofar as helping to keep the wood secure to its foundation while allowing it expand/contract. Lengthwise (dovetails parallel to the grain) I would think you will see very little if almost no movement in that direction so dovetails in parallel will more than likely work against you as the wood expands in width.

If there is reaction wood present in the timber, etc., then I would be reluctant to say that any method will work as good as you want it to. Since it sounds like you are talking about old timber, and I am assuming it has been cut and dimensioned to (or close to) the final dimensions of the application, it doesn't sound like you will have much of a problem at least with the dovetail approach. However you do the dovetails I would make sure that there is no gripping or wedging, etc., as the dovetails engage and traverse.