I am fortunate enough to have a quantity of highly figured 5/4 walnut feather/flame crotch that is almost fully air dry. This winter I’ll bring some into the heated space to take it down to the 7% to 8% at which indoor wood reaches equilibrium in this climate.
Later this winter, I want to use two pieces to make a coffee-table top. The way they were sawn, each piece roughly forms an elongated parabola. My idea is to cut them into true parabolas — using a template to remove the natural edge identically on each piece, and join the pieces in the middle in order to form an oval top. This will concentrate the near identical grain towards the middle of the table, much like book matching.
Here is the question: will such a top be prone to serious movement and warping, and if so, how can I damp it down? I had already thought of cross-batons using sliding dovetails, but the design would be adversely affected.
Joe
Edited 11/20/2008 9:19 pm ET by Joe Sullivan
Replies
Joe,
"will such a top be prone to serious movement and warping"
Only if the wood did not dry uniformly throughout. If it's going to equilibrate at 7% MC and its current MC is much higher than that (say, up at 11-13% MC) before you bring it inside, it's going to take a lot longer than "later this winter" to be able to use it. And still longer if its MC is higher.
You'll need to weigh it, or a sample to determine when it's stopped losing moisture. Record the weight every week until it's stable.
Remove material from each side until you have your curved shape. If it moves as you do that, allow it to settle down and remove a little at a time. It should then be stable in the final shape even during humidity changes. But if it's not, there is nothing you can do to confine any movement that it wants to do. Constructing furniture in which movement is going to happen, such as a breadboard end against the rest of the table top, wide tennons, etc., involves ALLOWING for movement, not trying to restrict it.
"Clamping down" wood that is trying to move due to RH changes in the ambient air will result in SOMETHING cracking. Whether it's the clamping structure or the piece being clamped. It's inevitable.
Rich
Highly figured pcs. like crotch figure have a lot of internal stress built up as the 2 sentions of the crotch were pulled in different directions with the weight of the rest of the limbs. Any work you do will release some of the stress, resulting in out-of-flat movement. So be sure to do the same thing to both sides - sanding, etc.
I had a couple big walnut crotch figure slabs - 8/4 x 24" x 52". One slab did not have any of the feather figure in it and it behaved really nice. But the next slab (off the same tree) had a 30" feather in it. It was the ponit at which the most stress was. I just could not keep it flat. Kept chasing a slight cup around the feather from one side to the other. Finally gave when I got it down to .125".
So process it, but let it sit a while to see if it moves.
Edited 11/21/2008 7:12 pm ET by BoardmanWI
Thanks, both responders. I take your points. I was a bit worried about the reaction wood in the feather, but it is so lovely!I have a good electronic moisture meter. Do you think that is an adequate read, or do I need to weigh it as well?Joe
Moisture meters are very accurate for telling a kiln operator which batches of lumber contain more water than others so he can move them around. Not that the readings are accurate in themselves, but relative to each other are accurate for those various batches.If you can accurately track the average relative humidity of your shop environment, and you know (from charts) the EMC for the wood specie you're drying vs ambient RH, a meter can get you close to knowing if the wood is at EMC. Maybe.It's a little bit more work, but when the wood, or a representative sample from it stops losing weight, you KNOW it's in equilibrium with the shop.Rich
This forum post is now archived. Commenting has been disabled