Help explain wood movement

Cabinet plywood is all I use for sleds.
The multi direction of grains holds it from moving.
There is no MDF in my shop.
New England humidity fluctuations are brutal on wood, especially composites.
I also try to keep wax on my sleds to keep the moisture out.

Good luck,

Lisa

-- Imagination rules the world. ~ Napoleon Bonaparte ~ http://quiltedwood.com

Makers of radius dishes for guitars, if they opt for MDF, will make them 2” thick. You’ve just discovered why.

Even plywood can bow, some more than others. For this application in your conditions, I’d use Baltic birch plywood…the more layers and the less voids, the better.

-- jay, www.allaboutastro.com

The surface that is on top or up has the air moving over it. This drys and shrinks. When it is smaller than the other side it bows up on the ends. Turn it over and you will shrink the other side and it will eventually curl the other direction. This will coninue until the moisture content is equal all through the MDF. There is nothing to prevent this in MDF. The more layers the more table like sniper states. If you had this in the shop a couple of weeks before you cut it…..maybe this wouldn’t happen. Try the Baltic Birch as suggested. Store it in the shop for a couple of weeks before you begin and see what happens.

I had the same experience with 1/2” Baltic Birch ply so that ain’t the answer either! Post the solution when you get it please.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

I don’t have that problem with the plywoods. Not noticable. I think it is moisture content in the product.

We don’t have enough moisture in SW Oklahoma to use lick and stick postage stamps. How would I know?

I think you guys are right. Grandpa has the best explanation. I’ll try some plywood, but it often doesn’t stay flat either.

Maybe I’ll try to catch it while it is flat and wax it????

Thanks for the posts.

-- Trees, a wonderful gift --Joe--

Also you need to add a hardwood front and rear rail to help keep it stable.
Like this one

-- Imagination rules the world. ~ Napoleon Bonaparte ~ http://quiltedwood.com