: in relation to skinning a kayak, what are darts and what are thier purpose
: and what are the indications for thier use?

Darts are sections where you overlap or cut out a wedge of fabric and sew it back together. Their purpose is to help the skin follow curves and angles without wrinkling. In my limited experience (two Greenland boats), I've found that if you tension the fabric lengthwise (the "hammock" method) and stitch it tightly (I like Bill Low's method), you can avoid darts, even with a stiff fabric like 13 oz. polyester. However, this is highly dependent on the boat design. The steeper the stem/stern plate to keel angles, the more likely that darts will be needed. From the pictures of your frame, I wouldn't think that you would need to use darts.