I did the NE Dory, and I made a bunch of those pvc clamps out of 4" PVC. I cut them about 1.5" wide. They worked okay, but they don't have a ton of clamping force. I ended up using all my c and bar clamps. If you put one around the other of course you get more force, but it's hard to use. I thought of making a special opener for it, but I just borrowed still more normal bar clamps. I think the harbor frieght clamps would be a better choice. I think you can find them for under $3 a pop. I wouldn't get the bar clamps with rubber jaws though. The bar clamps with a screw type thing to tighten are great as are the c-clamps. I'm thinking of buying a box of them for the mast. If I were going to use the pvc I'd doube or triple them up and make a tool. I don't think the 1.5" pipe nominal diameter will be useful as a clamp as you won't be able to open it much. 

   THANKS GRIGGS.  I just noticed the grip clamps I have and more from a friend will work with the outwales.  I should have check before I posted.    I just got started week ago on the prim and did not think that far in advace until after I posted to check it out.  Slow at times in preparing.  I will not do the PVD clamps from your response and I find grip clangs will work.  Thaks again.

   Nick -

Where are you?  I'm in central Massachusetts, and I've got a whole lot of clamps, both spring clamps and C-clamps, from my Skerry build.  If you're anywhere close, perhaps we could meet up somewhere.  I'd be happy to let you borrow them.

hokker

   Thanks Hokker,  I am on West Coast across the sound from Seattle.   Between kayaks and boats, this will be my 7th boat.  I  just checked, I have enough grip clamps from a friend that should work for outwales.  Thanks for the offer.

NickL

   I used 4-inch diameter PVC, cut maybe 2 inch wide on my combing, along with the other clamps I had, spring, c-clamps, etc. They worked fine for me.

   PVC clamps worked fine for me on both a Northeaster Dory and a Shearwater Sport Sectional. As Ralph indicates, cut them wider for more clamping pressure. Narrower clamps are easier to attach. You can spread them to more than 4".