Hi Larry,
Here's what I did on my CS17:
- I layed the butterflys on top of each other and drilled the 1/8" stitch holes on just the centerline joint. I used 6" spacing and later on wished I had used 4" (You need to climb aboard to epoxy the CL).
- I predrilled the sides only at the chine. After folding, it's easy to eyeball the mate and drill a hole. The side and bottom wrap with slightly different curvatures so predilling both will develop an offset as you go back (I think anyway)
- Sandwich the butterfly between two pieces of plastic covered plywood (Packing tape works well) with glass on both inside and out. Don't worry about running screws through the hull pieces. Those small screw holes are easy to patch up later. Getting a good fitting, flat butterflys is key to a balanced hull. Make sure you shoot some dimensions at the aft end of the hull & make sure the starbord & port sides are the same. I would plan on leaving the flat Graham designed in with this method. I think it really makes the bow of the boat!
Good luck, Tom