Spring clamps were good enough for epoxying my outwale as it was relatively thin but they didn't have enough oomph for the inwale I needed to epoxy in place so I knew I'd need a lot more strong clamps than I had. Clamps are expensive and I really didn't want to buy a bunch more so, as usual, I cobbled something together from scraps laying around the shop.
Cut a bunch of 1x2's down to something like 9" and then squares of 2x4 the same thickness as my inwale and outwale added together (to keep the jaws square). Drilled a hole a little below center in half the 1x2's and then paired each of them up with an undrilled 1x2. The final result worked out great.

20150111_001 by Alan Gage, on Flickr
I ended up using 9 of these DIY clamps and would have made a lot more but when I stopped at the hardware store they had Irwin clamps on sale ridiculously cheap so I bought a dozen of them. Had I known these were going to be so easy to make and work so well I might have not bought them after all.
Alan
Cut a bunch of 1x2's down to something like 9" and then squares of 2x4 the same thickness as my inwale and outwale added together (to keep the jaws square). Drilled a hole a little below center in half the 1x2's and then paired each of them up with an undrilled 1x2. The final result worked out great.

20150111_001 by Alan Gage, on Flickr
I ended up using 9 of these DIY clamps and would have made a lot more but when I stopped at the hardware store they had Irwin clamps on sale ridiculously cheap so I bought a dozen of them. Had I known these were going to be so easy to make and work so well I might have not bought them after all.
Alan