I recently boat a boat that was in awesome shape except this...
I thought no big deal, I can replace it. There are plenty of people that have splash rails hanging around in their garages...But, that's not what I did. I made a mold of that part from another boat, then fiberglassed, sanded, fiberglassed sanded....sanded, sanded, painted.
I made a mold of that part from another boat, then fiberglassed, sanded, fiberglassed sanded....sanded, sanded, painted... And finally it looks like new
Thanks fbjru for posting that photo sequence. I once used Marine-Tex (an epoxy with filler) to fix a virtually identical problem area. But your approach is nicer as it's not easy to get the original shape back with the method I used.
I just made a mold of that end from another boat. I put the mold under the broken end and then laid fiberglass on top. Then it was just a lot of work to lay fiberglass and sand.
So, to answer your question, I only used the mold to fix the broken end. The rest of it is original.