PVC stringers?

[Billkuma]

Exactly. Easy to learn the first time after you mate the wrong length of PVC pipe to a coupler when installing all new plumbing in an old house.

 

[AShipShow]

I've been down this road before... I was curious too and basically ended up going the safe route and using wood for my stringers... Most plastics are going to be a bad choice as a structural element as they have a tendency to stress relax or creep over time... So you're hull may end up taking on a new shape after a couple years in the hot sun...

If your end goal is a structure that won't rot, you really have two options... Pay up for some coosa (fiberglass reinforced foam) or you can build "hollow" stringers...

I contemplated going down the latter route with my rebuild but ended up not wanting to take the time/money to do it...
My plan was to build the stringer "structure" polyisocyanurate foam (the stuff that typically has foil facing on it at the big box stores). This foam won't react to the solvents in poly resin. I was then basically going to use that as a mold to form my fiberglass over... then When it was done, remove the foam and then you're left with hollow stringers/bulkheads.

This would require substantially thicker laminate for the structure though vs using wood.

 

[f_inscreenname]

Foam, seacast, 2X10, plywood, air, balsa, etc, etc.... have all been used. IMHO the more solid the core the less glass you need. In the Nova race boat they are balsa with a least a 1/4 to 3/8ths of a inch of glass on all sides. In the 1959 Biesemeyer its a 2X10 ...covered just enough you can still see the measurements written on the board.