I'm just kinda confused on how this boat was built...It doesn't look like other boats on I see online...The main stringer is literally just one 3/4 " plywood with two 1 inch strips at the top of 3/4.. It has several triangle pieces running east and west off the main stringer...It looks like they use some kinda box construction to gain strength....In the center under the gas tank it looked like balsa wood covered in glass? any of that make sense? thx..
Balsa is a great core material and still used today on many larger boats. the cockpit sole and the foredeck on my boat are all balsa core and even Ted's Cruiser has a balsa core foredeck
dont focus too much on the current stringer and how it was fabricated. a single piece of 3/4" with a strip at top was done to save cost and be cheap as hell. the main purpose of the stringer core material is three-fold.
purpose #1. bring enough natural strength to the job initially so a worker can step on it while draging resin-soaked cloth on top of it for the hull lay up.
Purpose #2. be wide enough to separate two layers of fiberglass. this is where the stringer strength comes from, it is the separation of two fiberlass surfaces. the stringer core needs to be sufficiently strong enough to not shear off the fiberglass. this is a lamination sandwich
Purpose #3. the core material must be of sufficient strength to hold fasteners shot into it to build the boat and rig the boat.
the stringer and bulkhead grid system is common build practice prior to todays stringer tubs. its why boxes of wine are strong with that little bit of cardboard stringer and bulkhead liner inside.
my recommendation, two layers of 1/2" or 3/4" plywood laminated together, placed in the hull in similar nature to your current layout. remember to round over the corners on top the stringers to promote the glass to curve around the edge.
If you want to use a newer composite core material, look into coosa or nida.
