Skimmer Ground Effects Vehicle Technology Education Gelinas Jr High School

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1 Skimmer Ground Effects Vehicle Student Name: Teacher: Mr. Moloney Technology Education Gelinas Jr High School Skimmer Page 1

2 STUDENT OBJECTIVES Define drag as the force that slows an object's movement through fluid (air or water0. Define a streamlined shape as one that reduces drag by letting fluid flow smoothly around it. Experiment with making the skimmer more streamlined and use data to choose the shape and size of the skimmer's front and back so that it moves as far as possible with the given air supply. SCIENCE BACKGROUND CAPSULE When an object moves through air, the air pushes against it, slowing the object's movement. The force that slows an object's forward motion is called drag. Drag is a form of friction. One way to reduce drag is to design an object with a streamlined shape that allows air to flow around it easily. Streamlined shapes re not pushed back easily by air so they cause less drag. Conversely, shapes that block the smooth flow of air cause the air to swirl or eddy, around them, causing drag. In Explore, students attach paper (cut in various shapes) to the front of a toy car and measure the effects of drag on each. Generally, the larger the shape's surface, the greater the drag and the shorter the distance the car will travel. In Investigate, students test body designs for their skimmers to find which shapes make the skimmers more streamlined. While some shapes will appear to make the skimmer more streamlined, shapes that are too large may add too much weight to the skimmer and reduce the distance it can travel. HOW TO A SKIMMER WORKS The skimmer functions by using air scoop to create lift. The lift is very slight but is enough to create less friction under the vehicle. The vehicle moves faster and easier due to the lift. Also, due to the cardboard construction, the skimmer weighs less and allows the lift to work its magic. The so called 'wings' stabilize the craft as it moves forward so it doesn't tilt one way over the other. Bernoulli s Theory Venturi Gravity Friction Newton s laws Drag Streamlined Principals of Flight Skimmer Page 2

3 Student Name: Introduction Skimmer Project: It is very important that you measure accurately and follow the direction. It is very important that you pay attention to the units that you are using. Equipment Pencil Standard US ruler Paper / Card Stock Glue Tape Paper fastener (optional) Lg. rubber band (optional) Procedure In this activity you will create a skimmer that will slide across the floor with ease if your measurements are accurate and your workmanship is exceptional. 1. Neatly and accurately use the plan sheet and measuring tool to draw your skimmer main body, air scoop, and two (2) fins onto the material that you will use to make your skimmer. 2. Carefully cut out your skimmer parts. Cut only on the solid lines. The dotted lines are where you will score and fold. 3. Use your ruler to draw the dotted lines on your cardboard air scoop and main body, and then fold on these lines to create a 90 angle. 4. Glue the fins to the ½ in. flap on the main body. Make sure that the angled edge faces the front of your skimmer. Glue or tape the main body back to the fins at an angle as shown in the orthographic drawing. 5. Glue the flaps of the air scoop to the inside edges of the main body with the narrow end flush with the front of the main body as shown in the orthographic drawing. 6. After all glue has dried, throw your skimmer along the floor and see how smoothly it glides. 7. You may want to put a paper fastener behind the air scoop and use a rubber band to propel your skimmer across the floor. Skimmer Page 3

4 Skimmer Plans (all measurements in inches) Skimmer Page 4

5 The project was really fun, and it had all sorts of great ties to the measurement principles. However the procedure included in the curriculum resources left a lot to be desired, plus the master teacher at the session had some really good tips and hints that I wanted to record, so I put together these steps and snapped some photos to go along so that we could all remember them. Here's what I put together. 1. Neatly and accurately use the plan sheet and measuring tool to draw your skimmer main body, air scoop, and two (2) fins onto the material that you will use to make your skimmer. You should lay out your different parts on the paper to use as many pre-cut straight edges as possible. 2. Carefully cut out your skimmer parts. Cut only on the solid lines. The dotted lines are where you will score and fold. Make sure to cut 3 in slits along the dotted lines in the back of the main body panel. These slits will be used to mount your fins to the main body panel. 3. Use your ruler to draw the dotted lines on your cardboard air scoop and main body, and then fold on these lines to create a 90 angle. You should use the ruler or an edge of a table as a guide for folding. Use one clean crease along your fold lines, do not pinch or fold it multiple times; this will cause your paper to loose rigidity. 4. Use a bead of glue to fix the back part of the main body at an angle as shown in the orthographic drawing. The very back edge should be flush with the folded down edges. Be careful not to get glue on any edges that contact the floor. Glue on the running edges will snag and create lots of friction, resulting in shorter skimming distances. Skimmer Page 5

6 5. Next, glue the fins to the outside of the half inch tabs along the sides of the main body panel. You should put glue on the fins and then carefully press the fins to the taps at an angle so that glue is squeeze upwards, thus avoiding glue oozing out on the running edge of the skimmer. Note that the back end is angled down, and this is where the fins are mounted. 6. Glue the flaps of the air scoop to the inside edges of the main body with the narrow end flush with the front of the main body as shown in the orthographic drawing. Skimmer Page 6

7 7. You may want to put a paper fastener behind the air scoop and use a rubber band to propel your skimmer across the floor. 8. Innovation is an important part of the design process! Check out these modifications. Can you explain why these modifications were made? After launching our skimmers down the hall (mine was only average) we moved on to discuss the design loop - which is the cyclical process that engineers and designers go through to move from problem to product. One of the better illustrations for this was the PBS series "Design Squad." I watched two episodes between breaks and once I got back to the dorm rooms we're staying in. The series does an excellent job with explanations as well as showing great team work Skimmer Page 7

8 Conclusion 1. How did completing the skimmer using the measuring system you are less comfortable with help to improve your skills? 2. How far did your skimmer travel? 3. Explain why your skimmer was more or less successful than your classmates. Skimmer Page 8