The "hull stiffeners" need to be replaced with the same thickness core. It might be difficult to remove one without removing other, especially if they are covered with the same piece of fiberglass.
The two inner most stringers are removed (one piece) and now the questions. The stringers are made from 3/4 pine board, or at least its not plywood and are 10" at its tallest. I don't think I will be able to find a pine 1x12 18 foot long, so I am planning on using 3/8 douglas fir.
I assume you mean laminating 2 layer of plywood? that is what I would do.
I will be using epoxy, but am not sure which weight of biaxial to use on stringers. Also not sure how many layers to use.
12 oz tape for the tabbing, and 17 or 1708 to cover them. You need to replace at least the old thickness
I am confused about using mat and epoxy, seems some say it isnt necessary.
matt is not necessary for strength (with epoxy) , but it does add thickness more quickly than only biax.