Tom,

I'm a bit confused. You say you have 4mm, but the post title is asking about 1/4 inch (6 mm). As far as I remember, the Chesapeake 16 uses 4mm, so if that's what you have you're fine. If you use 1/4 instead, you may not be able to make some of the bends, especially the foredeck, and te boat would be substantially heavier even if you did manage.

Laszlo

Tom,

I believe 4 sheets should be enough for the C16, though I'm not 100% sure about that.  The 1/2 and 3/4 inch should not even be considered for a boat project of this size as they'll be too hard to bend and far too heavy.  The 4mm should be plenty as that's what the kits use.

FrankP 

Laszlo, sorry for the error in my initial post.  I have 1/4 inch stock not 4mm.  Both you and Frank P confirmed my suspicions relative to applpicability of stock I have in the basement.  I had hoped you were going to say something else.  Still going to attempt the build, it just means buying more material.  Buying the material will be easier than explaining why the "perfectly good" plywood in the cellar isn't suitable.

On a Chesapeake 16 you couldn't do the deck or the bottom panels in 1/4-inch.  Just wouldn't make the bend.  It'd also be surprisingly heavy.  That boat was pretty much designed backwards from the bending characteristics of 4mm okoume, for better or worse.

Thanks for the inputs.  You have all convinced me that it has to be 4mm.