David,
You are not the first to think of PVC pipe as a kayak frame and probably won't be the last. The archive to this site is full of it's mention. It won't work. A SOF frame is supposted to have a LITTLE give but PVC pipe would flex enough to scare your pants off.
You need wood (your choice of species) or 6061, T6, schedual 40, 3/4 inch aluminum tubing. There are some space-age things,like fiberglass wands or tubes,that will work but they are not as available as the two items mentioned.
Remember, the Inuit kayak (wood framed) has between 1000-2000 years of developement by people who bet their lives on what they built. All of us build with that in mind.
Charlie

: I'm currently attempting to build a skin-on-frame kayak, as my first boat.
: The frame is 1/2' PVC pipe, made so I can disassemble it into many pieces
: for transportation. I'm contemplating different types of material for the
: skin, and this leaves me with a bit of a question. The forerunners so far
: are Marine Vinyl and Canvas. I know Marine Vinyl is waterproof, and canvas
: is not so it would have to be treated somehow (I don't know how). Is
: sewing required of whatever material I use, or can someone suggest a
: better way than going to an upholsterer? Anything someone could tell me
: about kayak skins would be helpful.