Nacell Construction: Basic shape of nacells and current materials about to be used. Not going to use wood, will be using carved styrofoam covered with fiberglass. I found a place behind my house that builds prefabricated walls (Structall) and they had lots of left over styrofoam they weren't using. I managed to talk him into giving me (15) 8'x1'x6" pieces! I intend on contact cementing some together and cutting them up with a handsaw, then sanding and fiberglassing over.
Main propulsion unit Construction: Archimedes Screw. This one kept me up at night thinking of an easy and cheap way to build. I basically started with a 3' long, 3/4" steel pipe and started wrapping double-stick foam tape around it. I layered the tape on top of each other following each strip closely. Eventually (30 layers later), I ended up with a 2-3/8" wind, which when taken into account the width of the pipe, ends up with a 6" diameter screw. The pictures below are the screw being fiberglassed and the clear 3' long, 6" wide, 1/8" thick clear pipe it fits perfectly inside (ordered special from online McMaster catalog). I'm using a clear tube not only because it really looks cool, but because the sprocket I'm using has an inner radius of exactly 6" and Schedule 40 PVC is a bit wider than 6" exactly, and is a huge, 1/4" thick. Much too heavy for what I needed. Luckily, McMasterCarr saved the day with this very nice 6" Acrylic tube. (Also shown is the bike the sprocket came off of and the sprocket).
Engine: Using an excercise bike picked up at the Flea Market down the road for a song. You can see how easy it will be to mount this to a boat platform. We will remove the bike seat, cut the tubing and replace with a hard plastic airport seat (still combing the Goodwills) at the same level as the boat platform.
This week: We'll be finishing the screw, and maybe testing the bouyancy of the styrofoam in my neighbor's pond across the street.