Standards

The 6mm exterior plywood that I ordered turned out to be barely 5mm thick and only 3 ply. It was CE marked at least, but take a careful look at that mark:

A Chinese CE Mark

Notice anything different about it? If you look at the tips of the letters, they taper in slightly. I don't know how true it is, but I have heard that this is the Chinese Export mark.

So I checked out the EN number:

EN 636 2G

EN 636 2G is defined as:

"Humid Use - Most construction uses fall into this category as they are covered or rarely exposed to weather, but still at risk of wetting"

The G indicates that it's a general purpose board (an S would indicate that it's for structural use).

So, as I need the punt to be structurally sound and it will be getting a little more than humid when in the water all components will be liberally sealed with epoxy resin and the outside of the hull will be sheathed in two layers of woven glass mat (plus double thickness tape along the edges). Then painted of course.