1996 Engineers Week Sink or Swim

By Juan F. Moya

Using fundamental principles in naval architectural, students build a boat out of aluminum paper. The demonstration demonstrates the concept of buoyancy, as well as introduces material science as an engineering tool in designing a boat. This demonstration will provide the students with a taste of engineering by going through the motions of a design problem and using fundamental engineering concepts. The demonstrator should begin with a brief description of a typical day in the life of an engineer, and an explanation of the concepts used in this demonstration. Present the students their design problem Sink or Swim and allow them to become Engineers for a Day! Materials Roll of aluminum paper 12 wide x 18 long x 6 deep container 3 dollars worth of pennies

scissors ruler Part 1: What is an engineer? (5 minutes or less) Give a brief overview of engineering by describing the different types, an overview of your major, where you attended school, the types of projects you work on, etc. Part 2:

1) Force = mass * acceleration; weight

2) Pressure = Force/Area

3) Buoyancy In simple terms, the principle of buoyancy is that if an object displaces an amount of water weighing more than its own weight, it will float. Inversely if the object displaces an amount of water weighing less than its own weight, it will sink. If the object displaces an amount of water that is equal to its own weight, it will remain suspended. When an object will neither float nor sink, it is considered neutrally buoyant.

Part 3:

One approach to the demonstration is to present the design problem as a contest. Divide the class into small group of 2 or 3, and provide each group with nothing else but a sheet of aluminum paper 18 x 18.

The students, as engineers with the school name Engineering Company are asked to design a boat

which will be used to carry X amount of pennies. Their boat design will be a model, or prototype, of the new full size scale fleet of ferries, which will carry people up and down the Holston River all the way to Knoxville! Each penny can represent one person. The design which carries the most pennies will be used to build the full size scale fleet!

Key to this presentation is allowing the students to create their own design. They will preliminary use

their imagination and their typical perception of boat looking like a speedboat, sailboat, yacht, etc. However, they understand and are able to use buoyancy as an engineering tool; their boat will look more like a raft or barge.

Alternative: Build a 5 or 6 different boat designs before the demonstration. Then as you get into

discussing the principles involved in this demo, you can ask the students to vote on which design they expect to carry the most pennies.

Part 4:

Once they have come up with the design, each boat will be placed on the water surface, and loaded with pennies, one penny at a time until the boat sinks. The boat which holds the most number of pennies will best demonstrates positive buoyancy.

Part 5:

Question/Discussion (whatever time is left)

Allow some time at the end of your presentation to discuss any questions the students may have on the demonstration, or engineering in general. Here is some more information you may want to use at the end of the presentation, or during the demo as you see fit: Hull Displacement Have you ever wondered why a large steel ocean liner floats, but a small steel nail sinks? The steel hull of the ship is formed in a shape that displaces much water. If the same amount of steel used in the hull of that ship were placed in the ocean without being shaped as such, it would also sink like the nail. On the other hand, speed boats have what is known as a planning hull, which allows them to obtain high speeds as power is increased. When you increase power on a speed boat, this raises the bow and causes the boat to skim across the water. Materials The most common choice for constructing a boat was wood, up until late 1800s (I think thats right, but not sure on the date) Today, pleasure boats (ski boats, sail boats, canoes, kayaks, speed boats, etc.) are built from plastic, most are built with layers of fiberglass, along with other synthetic materials. Some fishing boats are made from steel. New materials often provide light weight, yet strength and resistance to impact (for example: Kayaks)