Fin Shape Science Experiment Kit

Transcription

1 Kit #00524 Fin Shape Science Experiment Kit Test Different Fin Shapes to Find Out Which One Performs the Best! P/N Description Qty AT-18/5.4 (Fin Shape Sci Eng. Mount Tube) AT-33/3 (Payload Tube) AT-33/4 (Fin Can Body Tube) AT-33/9 (Main Body Tube) Coupler AC-33 (red) CR 13/18 (blue) Centering Ring /8 Launch Lug 1 Long Balsa Sheet 3 X 9 X 1/ Elliptical Fin Sheet (Balsa) Trapezoid Fin Sheet (Balsa) Rectangular Fin Sheet (Balsa) Shark Fin Sheet (Balsa) Plywood Ring Set (Fin Shape Science) PNC-33mm (BT-55) Crimped Engine Hook Apogee 12 Plastic Parachute Pack # Kevlar X 6 ft Clay mass - 5 grams Small Screw Eye Instruction Sheet A Instruction Sheet B Fin Shape Science Data Collection Sheet /18mm Display Stand (Cardstock) mm 3-Fin Alignment Guide (Cardstock) Decal Sheet (Fin Shape Science) Clear Plastic Bag 10x6x24 1 Skill Level 2: Previous Rocket Experience Suggested A fun science project is to test various fin shapes on a rocket to find out which one is best. The key to any good experiment is to limit the variables so that just one item affects the outcome. In this kit, we ve designed the rocket so that the rocket stays the same and only the fin shape changes. We further isolated the shape of the fin by making sure that the surface area is identical from one shape to the next, and that the fin span (how far it sticks out into the air) is also the same. In this kit, there are four pre-cut fin shapes you can test, and another eleven patterns that you can choose from to make your own hand-cut fins. To change out the fins, you simply slide the fin unit off the rocket and slide on a new one. The shapes can be swapped out in just a few seconds! p/n Other Tools and Materials Needed Pencil Ruler with a straight edge Hobby knife Wood glue Rubber cement, spray adhesive, or glue stick Masking tape Paper towels Paint supplies (spray paint, brushes, etc.) Wood sealer Sandpaper (220 and 400 grit) and sanding block Q-Tip or wood dowel for spreading glue inside tubes The Fin Shape Science Experiment Kit is another fine product from: Colorado Springs, Colorado USA web site: Page , Apogee Components, Inc.

2 Fin Shape Science Rocket Assembly 1. Remove the parts for the fin alignment fixture from the cardboard sheet. Dry assemble the parts as shown. Make sure the tabs on the cross pieces protrude through the side plates. Apply a bead of wood glue over the tabs on both sides of the tool. Set the piece aside to allow the glue to dry. Glue (both sides) 2. Fine sand the balsa wood laser-cut sheets using 200 and then 400 grit sandpaper before removing the fins. Carefully remove all the pieces from the sheet by freeing the edges with a sharp hobby knife. 1 It is probably wise to leave the edges square and don t round them with sandpaper. That way, all the edges of the fins are identical, even though the rocket won t fly as high. Remember, you re testing the fin shape, not the edges. 2 There are four pre-cut shapes you can test in this kit. The pattern sheet (page 8) has 11 other shapes you can try if you want to cut out some additional shapes yourself. Align wood grain with the pattern 3. Test your own fins: It is recommended you make three photocopies of the fin pattern sheet. With scissors, cut out the patterns you wish to test. Arrange the patterns on the balsa sheet, assuring that the fin grain direction on the pattern matches the direction of the wood grain on the balsa wood. This will give the strongest fins that won t easily snap during launch. Tip: You may have to flip one of the patterns over to get three fins to fit on a single sheet of balsa Once you have the orientation of the pattern to the wood grain correct, affix the patterns to the balsa sheet with rubber cement, spray adhesive, or a glue stick. Don t use liquid glue, or it will be hard to remove the paper after it has dried. 4 Cut out the pattern using a ruler and a sharp hobby knife as shown. 5. Sealing the surface of the balsa with sanding sealer makes the surface of the wood consistent. It also improves the rocket s appearance. Apply the sealer with a paintbrush. When dry, sand it with 400 grit sandpaper. Repeat the procedure until the balsa grain is filled and the fins look and feel smooth Test fit each of the fins into the slots on the fin alignment fixture. If they are too tight, you will need to sand down the thickness slightly. 6 Page 2

3 7. Sand off the little nubs of paper on the ends of the tubes using medium grit sandpaper and a sanding block. 8. Slide the fin alignment fixture onto one of the 4 inch (101mm) long body tubes. Test one set of fins into the fixture. Position the bottom edge of the fins on one edge of the tube. When you know how the fins are attached, you can remove them from the fin alignment fixture and apply wood glue to the root edge and then return them back into the fin alignment fixture. Allow the glue time to dry before removing the fin fixture. Repeat this for all the fin shapes you plan on flight testing. These sections are now called the fin-cans Add wood glue fillets to the fins where they touch the body tube. Even out the glue with your finger. Lay the fin-cans horizontally to let the glue dry. 10. Locate the engine mount tube. The aft end is the side closest to the etched lines as shown. READ THE FOLLOWING PARA- GRAPH FULLY! IT IS VERY CRITICAL. Place a small amount of wood glue on the tip of a Q-tip or a wood dowel. Smear the glue around the inside perimeter of the tube, at the cut-out made in the tube. Using a rocket motor, push the blue ring into the tube so that the front end of the ring is even with the front of the cutout. IMPORTANT: Once the ring is in place, there should be a slight slot at the base of the blue ring and the cutout. This is for the engine hook. 11. Tie one end of the yellow shock cord around the front end of the engine mount tube. Locate the plywood ring with the small notch. Slide the ring over the front end of the tube, threading the shock cord through the notch in the ring. Glue the ring to the front end of the engine tube. Put a fillet of glue around the perimeter to hold the ring and the cord in place. Allow the glue to dry Aft end Ring with small notch Small gap between blue ring and cutout. 12. Locate the two red tube couplers. Mark the approximate middle of the tube with a pencil as shown. p/n Page 3

4 12. Locate the plywood centering ring without any notches on it. Using wood glue, attach it to the inside of one end of a red coupler Apply wood glue to the threads of the metal screw eye, and screw it into the plywood bulkhead. Do not twist it in past the threads on the shank. Apply glue to both sides of the bulkhead where it exits the hole Glue the bulkhead into the remaining red tube coupler using wood glue. Recess it slightly into the end of the tube. When the glue has dried, put a fillet of glue on both sides of the bulkhead where it touches the inside of the tube Take the engine mount tube from step 11. Put a bead of wood glue around the outer perimeter of the plywood ring and a ring of glue just forward of the cut-out as shown. Slide the red coupler from step 12 over the rear end of the engine mount tube so the coupler is even with the front end of the plywood centering ring. Wipe off any excess glue that oozes out onto the surface of the coupler, and allow the glue to dry. 16. Take the metal engine hook and put the tab on the front into the slot at the rear end of the cutout on the engine mount tube as shown. Locate the plywood centering ring with the wide notch on the inner circle. Slide the notch over the engine hook and glue the ring between the etched lines on the engine mount tube. Put a fillet of glue on both sides of the ring where it touches the tube Slot Notch for engine hook Etched lines 17. Glue the two launch lugs onto the 9 inch long tube inside the rectangles that are etched into the surface of the tube. Make sure the lugs are aligned straight so they will slide easily on the launch rod. Apply a fillet of glue to both sides of the lugs and allow them to dry. Page 4 17

5 18. Glue the coupler with the screw eye into the 3 inch payload tube (the one with the small holes in the middle. It is positioned so it sticks out half way as shown Pass the yellow shock cord out the rear of the engine mount tube so it stays out of the way. Glue the red tube coupler attached to the front end of the engine mount into one end of the tube with the launch lugs. The edge of the tube should be even with the half-length line you drew in pencil on the coupler. Wipe off any excess glue that gets on the surface of the red coupler. When the glue is dry, pass the yellow shock cord back through the tube so it comes out the front end. 20. Tie the free end of the yellow shock cord to the eyelet on the base of the payload tube as shown. Put a dab of glue on the knot to prevent it from coming untied. Temporarily place the nose cone on the front end of the payload tube Place one reinforcement ring on each of the corners of the parachute canopy. Take a sharp pencil or knife and poke a hole through the plastic in the center of each ring Cut the shroud lines to make a total of three lines of equal length. Then pull each parachute line end through a parachute reinforcement ring and tie using two overhand knots. Repeat for all the corners as shown. 23. Holding the parachute at the center of its top, pull the lines together to even up the ends. Thread the three looped lines through the eye on the base of the payload tube. Next, take the top of the parachute and pull it through all three string loops at the same time. Finally, pull on the strings to tighten the knot. This securely attaches the parachute to the rocket Thread lines through eyelet Canopy through line loops Pull tight Page 5

6 24. Fold the parachute and insert it into the rocket along with the shock cord. Temporarily place one of the assembled fin-cans over the engine mount and exposed end of the tube coupler. DO NOT GLUE! 25. Roll a piece of paper and insert it into the back of the rocket to hold the model while you paint it. Similarly, roll a sheet of paper and insert it into the back of each fin can so you hold them while you paint them. For best results, paint the model with primer before using the final paint colors. Follow the directions on the paint can, and always paint outdoors with the wind against your back. Let the paint harden at least 24 hours before proceeding. You may paint the model your favorite color NO Glue Allow the paint time to dry and install the sticker decals as desired. 26. Remove the display stand parts from the laser-cut sheet. Glue them together using wood glue as shown. Allow the glue time to dry. You can place your rocket on the display stand for everyone to gaze at when you are not launching it. Congratulations! Your Fin Shape Science Experiment rocket is now complete. Launch Supplies Needed To launch your rocket you will need the following supplies: 26 A model rocket launching system Flame resistant recovery wadding Altimeter to measure the height of the rocket Data sheet to record the results of your project. Recommended Rocket Engines: B6-4, or C6-5 Rocket Preflight A A. Tie a string from the altimeter (NOT INCLUDED) to the loop on the nose cone. This is recommended in case the nose comes off during flight. Remember to turn on the altimeter and make sure it is ready to launch. B. Wrap a single layer of tape each around the perimeter of the rocket over both the nose cone joint, and the fin can joint. This is what holds them on during flight, and allows the fin cans can be swapped between launches. B Joint Joint Tape Tape Page 6

7 C. Crumple and insert three sheets of recovery wadding into the body tube. D. Fold the parachute and insert it into the tube with the shock cord. Then insert the nose and payload section onto the tube. E. Insert the rocket motor into the aft end of the rocket by bending the clip back slightly and sliding it in. F. Insert and secure the engine igniter as directed on the package the engines came with. Countdown and Launch Procedure Fly your rocket on a large field that isn t near any power lines, trees, or low flying aircraft. The larger the field, the greater your chances of recovering your rocket. The launch area around the pad must be free of dry weeds and brown grass. Launch only during calm weather with very little or no wind and good visibility. C D Spike Canopy 1 2 Fold 3 4 Roll Sides Inward Peak Down 5 Lay Excess String on Top of Canopy Loosely Wrap Any Excess String around Canopy And Insert 10. Remove the safety key from the launch controller. 9. Slide the launch lugs over the launch rod to place the rocket on the pad. The rocket should slide freely over the rod. 8. Attach the micro-clips to the igniter. The clips must not touch each other or the metal blast deflector. 7. Stand back from your rocket as far as the launch wire allows (at least 5 meters - 15 feet). 6. Insert the safety key to arm the launch system. The light (or buzzer) on the controller should come on. E Clip over end of motor Give a loud countdown LAUNCH! Push and hold the the button until the engine ignites. Then remove the safety key and place the safety cap on the launch rod. Misfire Procedure Occasionally the igniter will burn, but the motor will fail to ignite. If this happens, the F cause is that the pyrogen on the igniter was not in contact with the engines propellant. When an ignition failure occurs, remove the safety key from the launch controller and wait 60 seconds before approaching the rocket. Remove the old igniter from the engine and install a new one. Make sure that the igniter is insert fully into the engine and touches the propellant. Secure the igniter as directed on the engine package and repeat the countdown and launch procedure. Always follow the NAR* Model Rocket Safety Code when launching model rockets. *National Association of Rocketry **Kevlar is a brand name of E.I. DuPont for their selection of aramid fibers. Only DuPont makes Kevlar Page 7

8 Forward Edge Extra Fin Shapes Page (please find this page in the actual kit). Forward Edge Other Fin Shapes You Can Test! 1.0 inch Fin Area = 4.09 sq. inches Span = 2.5 inches Forward Edge All the fin patterns on this sheet have the same surface area and the same span (measured from the tip to the tube). If you want to make your own fin shapes, be sure to follow that criteria in order to minimize the variables in the flight tests. Before cutting the balsa, be sure to orient the fin pattern so that the wood grain aligns. This will make the strongest fin that is hard to snap off. Page , Apogee Components, Inc.

9 Fin Shape Science Data Sheet Date: Time: Weather Conditions: Flight Number Fin Shape Empty Wt of rocket Engine Used Altitude Max Speed p/n Page 9

10 Suggestions for Your Fin Shape Science Experiment How to Eliminate all the Variables That Could Affect Performance The critical part of any science experiment is to eliminate all that variables that could affect the results except the one that you are testing. In this project we ve tried our best to eliminate most of the variables that could affect how the rocket flies, but here are some other suggestions: Variable: Fin Area When we created the fin patterns, we used a computer program to determine the exact surface area of the fin. We adjusted the shape to ensure that all the shapes on the sheets have the same area. If you decide to make your own, you might have to use a CAD software to find out the suface area of your custom shapes too. Make sure your customized fins have a surface area of 4.09 square inches. Variable: Fin Span Another variable that people overlook is how far the fin sticks out from the rocket. This is called the fin span. The fin span is critical, because it greatly affects the drag on the rocket. Again, if you decide to create your own custom fin shapes, make sure that the fin span distance is 2.5 inches like the rest of the suggested shapes in this kit. Variable: Rocket Lift-off Mass One variable that we have not eliminated in the kit is the mass of the rocket. As you can guess, the rocket that is heavier is not going to fly as high as a lighter weight one. Even though the fins have the same area and theoretically they should have identical weight, the material they are made from has an effect on the final weight. The reason why is that balsa wood is a natural material and one tree may be denser than another. In addition, how you attach the fins to the fin can tubes can also affect the weight of the rocket. The amount of glue you put on when attaching the fins will vary slightly from one fin to another. Because of the varying mass of fin cans, we ve included in the kit a small amount of clay weight. Use the weight to adjust the mass of the rocket prior to installing the rocket motor. Here s a hint: weigh all the fin cans separately. Find the heaviest one, and put that one on the core tube with the engine mount. Weigh it again and record the mass. When you fly the other fin shapes, add a small amount of clay weight into the payload tube so that the entire rocket weighs the same as the heaviest fin shape. Between flights, always weigh the rocket and add or remove clay mass so that the lift-off weight is the same. This will eliminate the variable of weight and make sure that you re only testing the shape of the fin. Also remember to use the same amount of tape to hold on the nose cone and the fin can. It is recommended you measure the length of tape, and use the same length every time so any extra length of tape won t change the mass of the rocket. We suggest 4.25 inches long. Variable: Launch Angle Eliminate this variable by always launching the rocket with the launch rod pointed straight up. Don t angle it into the wind. Variable: Weather Conditions This is a hard variable to eliminate. The only way to do that would be to launch all the fin shapes at the exact same time so that they are all affected by the same weather (wind, temperature, humidity). This is a great idea, but it is a bit impractical because it involves a lot of rockets flying at the same time and much more sophisticated launch equipment. The next best thing to do is fly all the rockets on the same day. Hopefully that will reduce some of the variables like temperature and humidity since they probably won t vary much between one launch and the next. The wind will vary between flights. You never know when a gust of wind will come through the launch area and affect the trajectory of the flight. Ideally, you want to fly on a day with zero wind. If you have a choice, try to schedule your launches on a calm day. If there is any breeze, what you should do is fly the shapes multiple times and average out the results. So if one shape flew to 200 feet on the first launch and 220 feet on the next launch, the average altitude for that shape is 210 feet. But don t fly the same shape in succession. After each flight change to a different fin shape. Why? Because that will allow you to test other shapes when the temperature and humidity are fairly consistent. If you fly one shape four times in succession, it could be a long time before you get to the next shape. In the mean time, the temperature could have changed significantly. Variable: Rocket Motor Performance Unfortunately, this one is out of your control. Motors can vary a little bit in how much thrust they produce. In order to eliminate this variable, you ll need to fly your rockets many times and average out the results. Don t just do one flight per fin shape. The affect of the motor would be too significant. The more times you fly the rocket, the better. I hope this helps you with your project to find the best fin shape. Please let us know how your experiment turned out. Page 10