: I have readily available dodgy quality 4mm plywood sheets (2440x1200mm) for
: around $20 australian a sheet to build a S&G guillemot. This plywood is
: completely random, i have no idea what grade it is or anything like that.
: It looks relatively knot free on the exposed surfaces which also happen to
: look quite ugly. My question is should i even consider using this stuff,
: it is around 3 times cheaper than high quality marine or exterior grade
: plywood of the same thickness. If anyone here is from australia, its
: bunnings plywood in 4mm.

: My 2nd queston, is 4mm plywood really thick enough? I have no doubt that for
: the general hull this should be more than adequate, but im curious how it
: will handle my entire body weight on one spot when i step one foot into it
: as i get into it off a jetty (i weigh about 98kg ~ 240lb?)

Up until maybe 10 years ago I would have said you'd probably be ok as long as it was exterior grade ply. Not anymore, the cheap stuff is junk, wouldn't use it to build a dog house, certainly not a boat of any kind. Most non-marine grade ply is full of voids, the glue is suspect at best, tends to fall apart just sitting in your garage before you try to use it for anything. Now days you have to be really careful even with marine grade to make sure it really is. Best to buy from reputable sources and look for stamped ply, to insure it's quality.

Bill H.