HISTORICAL PERSPECTIVE: THE EVOLUTION OF SAILCLOTH

Title: The Evolution of Sailcloths for Sailboats

(Historical Perspectives)

Grade Level(s): 6-8

Introduction: The most important and obvious feature of sailboats are the sails. Sails have evolved throughout the years, not only in their shape, but their sailcloth material. The most common sailcloth today is Dacron, which is an extremely durable yet inexpensive sailcloth developed by Dupont in the early 1950’s. Until the 1980’s Dacron was the only sailcloth in use. However, the last few years have seen a virtual explosion in the development of new woven and laminated sailcloths. Today’s cloths include not only the familiar woven Dacrons and woven nylons in various weights and finishes, but laminates using Kevlar, Mylar, Technora, PBO Zylon, Pentex and Spectra yarns.

Woven polyester sailcloth is extremely durable and rather inexpensive. Specific styles of woven polyesters are commonly named by weight, such as “6.1 oz. Dacron”, or “8.3 oz. Dacron.” Usually the unit of weight in the United States is ounces (oz.) Per “sailmaker’s yard,” which is 36 inches by 28.5 inches.

More and more sailors are turning to laminating sailcloths because laminates are lighter for their strength than Dacron. Laminates also have superior shape-holding ability. As the name implies, laminates all have some cloth or yarn glued to one or more layers of Mylar.

In the following class activity, the students will use Dacron sail pieces, available from any sailmaker, and other common materials to simulate other sailcloth materials. A common burlap bag will simulate the canvass sails used by ancient mariners on their clipper ships and transparent gift-wrapping cellophane to simulate modern laminates such as Kevlar and Mylar.

Learner Objectives:

• The student will be able to compare and contrast sailcloth materials used throughout the years and test the cloths for stretch (Durability), permeability, and resistance to puncture.
  
  
• The student will be able to discuss the advantages and disadvantages of the three different sailcloth types.

Sunshine State Standards: Science: Sci.H.1.3.5:, Sci.H.3.3.4

Competency-Based Curriculum: Science: M/J1-IA6 M/J1-VIA2

Materials:

4 1ft. x 1ft. pieces of burlap bag
4 1ft. x 1ft. pieces of Dacron sail
4 1ft. x 1ft. pieces of transparent cellophane paper water for each group

Activity Procedures:

1. Divide the class into four groups and each group receives one sample of each of the three simulated “sailcloths.”
2. Each group will perform several different experiments to test the durability and effectiveness of the “sailcloths.”
   1. Manually pull the edges of all three “sailcloths” to test for material stretch and flexibility.
   2. Pour water on each of the three “sailcloths” to test for permeability
   3. Puncture each “sailcloth” with a pencil point, and then pull the edges of the sailcloth to test for durability of material.

Student Assessment:

Allow students to answer critical thinking skills questions assigned by the teacher.

1. Which of the three simulated sailcloths stretched the most when the edges were pulled? Which sailcloth was most resistant to stretch?
   
   
2. Which of the three simulated sailcloths allowed the most water to pass through it (permeability)? Which sailcloth was the least permeable?
   
   
3. Which of the three simulated sailcloths resisted stretch after puncture? Which of the sailcloths (if any ripped after puncturing and stretching?

Activity Extensions:

1. 1. From the data obtained from the tests why would racing sailboats use plastic composite sails rather than the Dacron or canvas sails
   
   
2. 2. From the data obtained it was shown that the plastic composite sailcloths have a tendency to rip apart easily when punctured. Dacron and canvas sails were sewn using needles and thread to give shape to the sail. So, knowing that the composites sails puncture easily, how would panels of these composites sails be joined together to give the sails their shape?

Home Learning Activity:

Research the price differences for Dacron and composite sailcloths. Calculate how much it would cost to design various size sails based upon the cost of materials.

Vocabulary: Dacron, Kevlar, Mylar, Technora, PBO Zylon, Pentex, Spectra

References/Related Links:

http://uksailmakers.com/encyclopedia2.html
http://www.sailing.org/youth/sailingsmart.html
UK Sailmakers Encyclopedia of sails, 1999 - Sailcloth information
Yachting World Magazine (2000). Cotton on to new materials.