Science Buddies: "Ask an Expert"

Am I supposed to build the same shape of boats with different materials if my problem of my project is: Does the buoyancy and material of a boat affect how far it will travel in water? And if you can, can you please direct me to a link where there are instructions where I can build and attach propellers to the boat? Thank you.

Taipopo - The mass or weight of two different hulls of the same exact design will ride in the water at two different levels. This is part of the buoyancy described by Archimedes principle. Because they ride in the water at different levels, or drafts, they will have different friction levels with the water and will travel at different speeds, with a given input of propulsion, will travel different distances. As to attaching propellers and motors, that is more of a model makers skill. If you want to have an internal electric motor, for example, you will have to provide a form of 'stuffing box' which is just a tube that the propeller shaft will go through with the end inside the hull higher than the water level. This will keep water from entering the hull and sinking it.

Rick Marz

Taipopo: This is a good project to learn about different materials, what makes a boat float (buoyancy principle) --even the boat made with dense materials, in addition to learning the physics of air current and water current. I would also encourage you to look into controls and variables when designing the experiment, as there are several factors you are looking into. For eg., boat size, shape, material strength and properties, air current (are you using a fan to propel the boat in a particular direction ?), etc.

Good Luck in your project.
Raji Pingali