If not required as a boat, the pontoons could be filled with soil / rocks to weigh down the floor of a shelter . Another can be raised to act as an insulated wall.
2m Long with foam core grp fibreglass pontoons & Deck made from composite door off cuts.
They are strengthened with 2m door edge strips of grp skin plastic core strips. These strips still floats & is a similar density / weight to hardwood
Pontoons will be filled with insualted panel 2m long offcuts that consist of polystyrene, plastic & mdf. Voids will be filled with expanding foam.
Showing the 3 basic parts, 2 pontoons & a deck. If the pontoon is attached directly underneath the deck, it may only need 3 sides.
It is intended to bolt the deck to the pontoons
Underside of thinner deck showing panel type construction
Close up of top of Deck showing stregthening with edge strips & screws using Lumberjack pu glue.
I have started using self tapping torx screws which do not need pilot holes, though a bit more expensive. I dip the screw point in glue to lubricate on entry & stengthen screw join & help stop splitting.
Lumberjack glue by Everbuild is sea water resistant
I experimented with a second type of pontoon, binding the buoyant core strips together with pvc straps & screws
Then encasing the buoyant core with a grp roofing sheet & screwing shut
Folding the front end to make it streamlined, ready to accept a nose cone or fibre glassing (undecided as yet)
Pontoons will most likely be covered in fibreglass.