Each year some students have a contest to build and race concrete boats. any advise to make them float?

Question

Each year some students have a contest to build and race concrete boats. any advise to make them float?

Answer 1

sneak some wood in

Answer 2

First answer about water displacement is right. Anything will float even concrete as long as it displaces enough water to support its weight. Basically you would be looking at something that is thin to keep the weight down, and has a large surface area with a slight vee to it so it will displace as much water as possible. Make the nose into a gradual point and you will be good to go.

Answer 3

I don't know what the rules are, but if you can use some kind of filler, try a small amount of sawdust. That should lighten the concrete a bit without weakening it too much. If you can do that, be sure to expirement with the mixture. Aside from that, build it wide and deep. Be sure to let the sides curve back to the stern for a clean flow around the hull. Making it an efficient shape will mitigate the problems with a deep draft. Typically, deeper is better than wide. Too wide, and the frontal cross section is going to hurt you. Imagine a wedge shoving through the water.

Answer 4

Make them as light as possible and wide. They will float very well!! For power you can use a man powered cement mixer on the stern!

Answer 5

advice to make them float?  make sure the water they displace weighs more than the boat.

but that goes for everything

Answer 6

http://www.concreteships.org/history/