I suspect you wrapped the Saran all the way around which held the gunnals in. When the boat is floated open-topped the gunnals are likely to flex outward at times. You have a bare minimum of framework, a minimal displacement and a fairly long span without any thwarts to tie the sides together. When you get the boat skinned set it up on horses and push down where you would be standing when you get in. You'll see what I getting at.

: Hi all,
: I am looking for advice on skinning options for an SOF canoe. I
: know similar topics have come up before, but couldn't find
: anything quite right in the archive.

: What is the lightest weight skin and coating you can use, but still
: get a reasonably durable boat? The boat will be used on mountain
: lakes, so it wont so much be run into stuff in the water, but it
: will likely get rammed into branches during portages. I am
: partial to things I can sew on, but am open to all suggestions.

: What I am working on is a boat that I can schlep into mountain
: lakes around Banff. Weight is a factor, the finished frame is a
: hair under 10 pounds (and admittedly slightly overbuilt) so I
: want to add as little more weight as possible.

: About the boat itself, its 11' x 28" x 13" the frame is
: mostly red cedar, with a yellow cedar thwart and stems and five
: ash ribs (the tree was grown in Calgary so its really dense
: wood), I didn't so much use plans as I just built something that
: looked right, I blame the inspiration for the boat on DGentry
: and his transparent wee lassie. I have had it on the water with
: saran wrap, and it is way more solid than you would think should
: be given the rib spacing, it paddles well, tracks straight, and
: is as stable as rec boat.