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Grade Level(s): 6-8
Introduction: The mast on a sailing ship is a vertical, or nearly vertical spar generally made of wood, metal, or carbon fiber composites supporting the accessory spars; yards, booms, sails, and rigging. Smaller boats have masts commonly made of wood, but hollowed wood or metal construction is also employed. On large clipper ships, and square-rigged ships, the masts were made of one, or sometimes two wood sections, usually from large logs. The size of masts were often limited by the fact that long straight logs are not very common. These masts were generally large in diameter, heavy, and had very little bend. Later in history, aluminum became the most common metal for masts. Aluminum masts were lighter, stronger than wood, and have some bend. The advent of metal masts was advantageous since they were less expensive, and environmentally friendly. In recent decades, science has contributed to the use of composite masts, most notably carbon fiber. Carbon fiber masts are stronger and lighter than metal masts and can also have some bend.
The bend, or rake, of a mast is very important since it adds shape to the sail that it supports. Sail shape is important since certain wind conditions need very specific sail shape to maximize boat speed. This exercise will attempt to show how different materials can be compared to each other to simulate masts on sailing vessels. Furthermore, comparisons of weight and bend of the different materials can be used to compare optimum characteristics for an effective mast on a particular vessel.
Learner Objectives:
- The student will be able to compare and contrast different common materials that can be used to simulate masts on sailing vessels.
- The student will be able to discuss the advantages and limitations of these materials if the student was to use these materials to build a mast for a sailing vessel.
Sunshine State Standards: Science: Sci.A.1.3.1 Sci.H.1.3.5
Competency-Based Curriculum: Science: M/J1-IA6 M/J1-V!A2
Materials:
Four 3 foot wooden dowels
Four 3 foot aluminum rods - preferably hollow
Four 3 foot plastic rods - preferably hollow
Triple-beam balances
Activity Procedures:
- Divide the class into four groups, and give each group one wooden rod, one aluminum rod, and one plastic rod.
- Ask the students to describe the characteristics of the various rods by observation. These rods are three “simulated” mast types, with the plastic rod simulating carbon fiber masts.
- Ask each group to weigh each rod and record the findings.
- Allow each student in the group to bend each rod and observe what happens to each rod. Record the results. Attempt to bend the rod as much as possible without breaking the rod.
Student Assessment:
Allow students to answer critical thinking skills questions assigned by the teacher.
- 1. Compare and contrast the three rods by observation alone. How does each rod feel to the touch? Does it feel heavy, rough, smooth, strong, or flexible? Which kind of rod is most pleasant to handle?
- 2. How did the weights of the three rods compare? Which was the lightest, and which was the heaviest? Is the weight of the rod an indicator of how strong the “simulated” mast can be? Is the weight of the “simulated mast” indicative of how much sail this particular mast can support?
- 3. How much did the rods bend? Imagine if these rods were masts on a boat, which mast would have the most rake (or bend) without breaking? Is the flexibility of the rod directly related to how heavy or light the rod material is?
Activity Extensions:
- There are a variety of mast types on racing and cruising boats today. Why do some racing boats have carbon fiber masts, while cruising boats of similar size have aluminum masts? Conversely, why would some cruising boats have carbon fiber masts, while racing boats of similar size have aluminum masts? (Technology)
- In the Olympic Games, most racing sailboats have aluminum masts. The newest Olympic class boat, the 49er, has a carbon fiber rig. Should the other classes of boats (Laser, 470, Finn, etc.) Also be allowed to use carbon fiber masts?
- When constructing a new racing or cruising boat, how do you think the architects, builders, and designers choose what kind of mast they will put on the new boat?
Home Learning Activity:
Find the largest and/or tallest wooden, aluminum and carbon fiber mast ever built. Write an essay explaining the differences between these masts.
Vocabulary: masts, spars, yards, booms, sails, rigging
References/Related Links:
http://encarta.msn.com/index/consiceindex/5F/05F45000.htm/
Pepper, M. (ed.) (2000) Swan’s Latest Celebrates Maiden Voyage, Yachting World Magazine.
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