I really like it when folks follow up on their posts and report on how things worked what they' change etc. and realize that I hadn't done that for this so here's what I learned...
Originally Posted by knucklenuts
On materials, if you use good okume ply(stay away from the fir it checks bad) there is no reason to glass in and out, just tape the corners and paint or varnish.
So a few months into my wood drybox trial so I thought I'd give an update. I did not follow this advice, for several reasons really...first this was simply an experiment to decide if I wanted to go this route and make nice, durable boxes or save for aluminum so I went with cheap or on-hand materials. 2nd - I was in a hurry and didn't have time to order/find marine here in mail-order-ville........But it's true... and I knew it going in. My box is already checked badly. Paint on CDX will not do you for the long term, I'm sure of it. I like how they work and how they came out so I will build two more this winter using better materials and a more complex design (arched or angled sides, one with kitchen box legs, integrated handles and hopefully a latch in or short camstrap hold down type system (not looped cams under the box as it is currently).
The other issue I had was I used leftover pine for the frame, which has worked fine except for at the latches. It split at the latches when I leaned back into the rowers seat (strap on plywood with high back seat, strapped through footman loops mounted to lid (so I can open the box with undoing straps)). I cut off the culprit piece of stock and replaced it with some Ipe I had laying around and it held up great for our Oregon excursion. On my next box however I'll probably use oak or ipe for the structural portions to prevent this type of tear out and ensure high strength and it really won't weigh or cost that much more. FWIW 3/4" ipe strips are stronger than a pine 2x2... and weigh about the same.
Here's a recap I posted somewhere else about how I built it:
The bottom is a pine frame (1"x 1 1/4") dado'd on the outside to accept the 3/8" plywood, glued and stapled with a pneumatic stable gun. Then I attached a 3/8" ply bottom (same dimension as outside of frame) This was glued and screwed. I ran 5/8" stringers up the corners and glued and stapled the ply to the stringers and bottom frame. Up top I used 3/4"x 1" pine to make a frame around the outside of the box (about 1/2" below the top of the plywood). I just tacked this together with screws (I moved it later...). The lid is similar to the bottom but bigger, I made it so it just fit over the top of the box. For this I made this frame the same dimensions as the upper lip (that was just tacked in place) and it lies directly on the lip with just a little slop side to side (so the lid can move around about a sixteenth). Once this was done I removed the lip so that the lid sat directly on the top of the plywood then reinstalled the lip tight to the lid with glue and screws from the inside (take care that you're close to final install position when you tack it up so you can reuse the holes through the ply). You could probably carefully measure and do this in one step, but I wanted the lid to touch the inside of the box at the same time it touched the lip all the way around and thought this would be the easiest way. I put gasket on the underside of lid. I then put a 1/16" shim between the lid and lip and attached a piano hinge across the back. Removed the shim and then install the gaskets. The 1/16" gap is ideally there so the lid closes evenly all the way around. You might want to install the gasket and then install the hinge... what ever works. Originally I put a different gasket on box side against the lip, but had to remove that when I replaced the front lip with Ipe and just stuck with the gasket on top. I have not found a single drop of water in it, following time on the river or sitting in torrential downpours in the drive way. It's never been flip or submergence tested.
Another way to look at the lid, is it's basically just a shoe box style lid with the lip around the edge acting as another place to seat/seal.
Finally a pic showing the basics...