I'm trying to cut out the coaming base rings out of 1/2" A/C grade exterior plywood from Lowes (ala Yost kayaks/plywood stacked coamings). It's been in the garage for a month or two and it's fairly been wet/humid lately. (OH! And, I'm kind of an idiot when it comes to this stuff.)

Ok, so that's the background.

I'm trying to cut a fairly simple curve of the interior coaming ring (even the long side). It seems like I'm hitting something hard inside of the plywood. It seems like I hit it and it grabs the blade and pulls it out of the socket/connector/thingie. There are times I can barely go 1/4" before the blade pops out.

I've tried...
- making sure I'm not pushing on the blade;
- trying to make the blade go faster/slower;
- trying a new blade;
- trying a more coarse blade (I'm using "fast sheet metal" blades for a nice clean cut);
- trying to attack the cut from the opposite direction.

I do feel like the piece is fairly securely mounted/clamped.

Is this just simply the wood being damp from the humidity (MD area)? I'm not sure what to do differently - I tried just pushing through tonight, but I was a good chunk of time in and hadn't cut out of the interior of the ring.

Ideas? I'm fairly irked.

-Doug