Battle of the X-Planes
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Student Handout |
Material Costs
When you have determined the amount of materials needed for your design, use this chart to determine the total materials cost for your backpack. Make sure your backpack meets all the Materials Guidelines listed below.
Materials Guidelines
Thread must be used along every seam. Zippers must have a seam along both sides. Each edge must have one extra inch for a seam. Heavy-use areas, such where shoulder straps are attached to the main body of the backpack and along the bottom, require double seams.
 Material |
Cost* |
Amount Needed |
Total |
Water-resistant heavy-duty fabric |
2 cents per square inch |
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Heavy-duty fabric |
1 cent per square inch |
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Water-resistant light-duty fabric |
0.5 cent per square inch |
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Light-duty fabric |
0.3 cent per square inch |
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Expandable fabric (every square inch can equal up to two cubic inches in volume |
4 cents per square inch |
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Padding |
2 cents per square inch |
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Heavy-duty zippers |
10 cents for first inch; 5 cents for every additional inch |
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Light-duty zippers |
5 cents for first inch; 2 cents for every additional inch |
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Heavy-duty Velcro patch |
10 cents per square inch |
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Light-duty Velcro patch |
5 cents per square inch |
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One inch wide nylon strap (to adjust length of shoulder straps) |
5 cents per inch |
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Plastic piece to tighten shoulder straps |
10 cents each |
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Reflective tape |
15 cents per inch |
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Buckle (for optional waist strap) |
35 cents |
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Heavy-duty thread |
1 cent per sewn inch |
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Light-duty thread |
0.5 cent per sewn inch |
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TOTAL COST PER BAG |
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* metric equivalents
1.00 inch = 2.54 centimeters
1.00 square inch = 6.45 square centimeters
1.00 cubic inch = 16.38 cubic centimeters
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