I don't have an NE Dory, but my brand X sailing dinghy is reasonably similar in terms of the skeg and general weight. Its bottom was completely covered with glass before the skeg was put on and there are no problems with delamination.

If you attached the skeg first and then glassed, any twisting of the skeg would affect the entire glass on the bottom, imparting a slight twist that could theoretically start delamination and peeling. By covering the bottom before attaching the skeg, you eliminate the twist. Having said that, the twisting forces are so low compared to the strength of the cloth that as a practical matter it makes no difference how you do it and glassing first is easier.

If you're looking for the absolute strongest way to attach your skeg, ditch the screws. They're stress concentrators. Instead, bed the skeg in epoxy/woodflour putty. Make the bed deep enough so that there is no wood-to-wood contact. Up to 1/8" is good. Then, put big fat fillets along each side. This is the one time you don't want little skinny fillets. You want them to not just support glass tape, but to also smooth the flow of water along the joint. Cover the fillets with at least 6 oz tape.

The putty bed and fillets will nicely distrubute any skeg forces evenly over the bottom. The glass will hold the skeg on better than any screws could. Use packing tape.to keep the skeg in place while it's curing,

Have fun,

Laszlo

To the OP are you saying you've seen "fiberglass fractures under NE Dory skeg" or your just worried about them?

John,

No, I have not seen any fractures.  I am in the process, albeit slowly, of building my NED and was reading a blog post on another wooden boat builders site and the topic was discussed.  The question raised was why glass the hull, then place the skeg over the glass and penetrate the glass with fasteners? Also if by chance there are any small voids between the glass and hull where the skeg is attached, might that not be a weak link since the weight of the boat will rest on the skeg while on a beach in addition to the lateral forces placed on the skeg?  Laszlo, in his inimitable way, provided both his experience with his vessel and also his opinion on how to create the strongest way to attach your skeg.