Hi CBTerry, are you planning to sit inside the hobie 18 hull or on top of it?, they're not very beamy, the AI overview says 20 inches wide and I cant reach mine easily [but they don"t look close to that wide] if you can fit your hips in your legs will be pretty cramped, if you are going to sit on the deck and put your feet in the hull the area where you sit and rest your feet will all need to be reinforced. The cheapest glue that will work is a polyurethane type, one brand is Gorilla grip over here,[ marine polyester resin and 6 ounce glass matt is pretty cheap and is all you need]. If you are going to bolt or screw plywood on use epoxy to reinforce the hole and paint all end grain well . It is easy to add material that is too heavy so try and avoid it. I think you could keep the dagger board case in place and the deck around it which to sit on, the decks are generally very soft if it is an old one so not suited to standing on without it collapsing, you will need to locate buoyancy in each end [as suggested], there is polystyrene blocks in the hull[ unless thats only the H16] you can paint with polyurethane or waterproof pva [ large plastic drink bottles tied in would work too] and strap and glue then in. I'm in the[stalled] process of altering hobie 18 hulls and using them as my new floats for a tremolino. An old canadian canoe is probably cheaper in the end and a simpler more practical fit for an outrigger is my guess but your idea would be go faster and handle chop , I have posted my build process here years ago, it is fun messing about with boats. Weigh your hull before you start and each addition ongoing. This post will self destruct in a few days if no interest is shown, regards.
