> I'd like to see someone look at semi-monocoque aluminum construction
> as a design exercise. Floatation bags would be important, eh.

If you are looking for rigid, but heavy, paddle craft you might want to browse the web searching through the many references to concrete canoes. These things have been raced by college teams -- usually the same engineering students that designed and built theme -- in competitions for over 20 years. Photos of current boats that I have seen include a few with partial decks. A complete deck is certainly possible to design.

Hull weights seem to be about 150 pounds for competititve boats, but if you think about it, a 50 pound kayak that has a capacity of 500 pounds when fuly loaded is no different from a 400 pound concrete kayak with a 150 pound paddler. You could even get away with a heavier boat by simply increasing the hight of the sides. Performance would be awful, but if it banged against the dock I would not worry about dinging the boat! I've seen stories on sailboat hulls made of iron or steel mesh and filled in with concrete. Ferro-concrete is what the stuff is called.

Making one of these things is not currently on my schedule, however, if you would like to try....

You could try using the station forms for a stripper and covering them with several layers of small mesh fencing. When you have 4 to five layers, and it appears to be mostly metal, use some short pieces of wire to hold these layers together. Slather some sandmix over the mesh, being sure to force it gently through all layers of wire. Squeegee both inside and outside to remove any concrete that is not trapped in the weave of the metal mesh, and let the thing set. I uncerstand that if you keep it wet for a while the concrete will get stronger, so once it has hardened, sink it in the local creek and come back in a week. Don't worry about someone stealing it while you are away. No one is going to be that crazy. If you can get it out of the creek, let it dry well before trying to paint it.

I'd guess you'ld use 2 or three rolls of chicken wire fencing, at about $10 a roll, 3 to 4 bags of cement and about the same of sand, or some other filler. Some of the racing canoes use perlite, and I've hear of portland cement/chopped styrofoam combinations. With an 80 pound bag of portland cement going for about $5 at the local hardware store, the cost of a 300 to 400 pound boat is going to be awfully cheap, but the roof rack for it is going to be expensive, to say nothing of beefing up your car to carry such a monster :)

I would not recommend using these materials for making a matching paddle.

One of the rules for college competition is that the boat stay afloat even when completely filled with water, so sealed areas are designed in. Don't think that a concrete canoe is going to sink like a rock. if it is well designed, then even without flotation bags, it won't.

Get back to me if you want URLs to some of the concrete canoe sites, or check with Yahoo or Lycos os some other search engine.

Best of luck.

Paul Jacobson