1. 1 Revised 07/10/06

2. 2 What is the mission? The mission is to design a Water Rocket Vehicle capable of accurately targeting a specified bullseye. While promoting Space Propulsion Awareness, the Water Bottle Rocket Competition serves to familiarize students with the basic principles of rocketry, design engineering, manufacturing engineering, and presentation skills. Students will design and manufacture a water rocket using a 2-Liter bottle as the pressure vessel. The rocket must be capable of accurately targeting a specified bullseye launching from the UTC Rocket Launcher. The design must be supported by technical documentation and presentation outlining all mathematical and scientific principles used. Additionally, each team will develop a patch design, used to symbolically commemorate the objectives of each team. The team’s complete success will not solely be judged on rocket performance, but the combined effort of the team....……………………………......GOOD LUCK and Safe Flying !! *** Remember you will never be a winner unless you try and if you try your best, you have already made it to the bullseye :-) *** (Refer to Rules & Guidelines and “How to Build Rockets” manual for detailed information.)

3. 3 Rules and Guidelines

4. 4 Keys for Safe & Enjoyable Launch Activities: Extreme caution should be used at ALL times during launch activity. The Water Rocket Launcher and Water Rockets are NOT toys; thorough understanding of their function is required prior to conducting ANY launch activities. Safety Goggles/Glasses shall be worn during all launch activities. NEVER stand directly in front of launcher at ANY time. NEVER approach a rocket that is under pressure. No running, horseplay, etc. around launch area/ during launch activities. Be attentive at ALL times. Use Only single CLEAR 2L bottles for rocket pressure vessel (Bottles should be in good condition without kinks, cracks or dents). Always use a CLEAR audible countdown (5!... 4!... 3!... 2!... 1!) before EACH launch. All Rockets should be thoroughly inspected prior to launch. Do NOT over-pressurize rockets 80psi MAX. Use ONLY Large open fields for Launch…..250m or MORE of down range distance is preferred. Rope-off or clearly mark Launch Area/Field. Always conduct a trial launch at low air pressure (e.g. 35-40psi) to get an idea of how far your rockets will travel with respect to a given launch area.

5. 5 1. Maximum number of 6 students and a minimum of 4 students per team are allowed. 2. Each team is required to submit a completed technical paper, rocket design, technical drawing and patch design to qualify for the awards. Note: Awards will be presented at the annual FACTRAC banquet. 3. On the day of competition, (but prior to launch) an actual operating rocket with its launching requirements [1. volume of water in milliliters and liters, 2. air pressure in psi (min 30 psi & max 80 psi), 3. Dry Weight in grams, and 4. Nozzel Exit Radius in inches, and 5. Calculated Final Range in meters and feet], corresponding technical drawing, and patch design must be submitted in order to compete in the competition.(Ref. Required note card detailed in Technical Drawing Section, page 12) Note: 1) At this time each entry must pass a visual inspection and weight requirement in order to be eligible to compete. Entries that fail inspection will be given ONE opportunity to make modifications to pass inspection, prior to the beginning of the water rocket launching competition. 2) Technical paper must be submitted on _____________________________ 4. An overall winner will be judged upon the following criteria detailed on page 17. 5. The objective of the contest is for each team to construct a rocket propelled by water and air which will be launched at a 45 degree angle to hit a target that will be positioned 61 meters away (distance from HP Rocket Launcher to red bull’s eye; ~200ft), in the target area zone, see Diagram 1a. The target area zone is a 45 degree zone (25 degrees from each side of the target area centerline) if your rocket lands outside of this zone 50 points will be deducted from the accuracy of trajectory score, see Diagram 1b.

6. 6 NOTE: Launch accuracy will be scored using the distance and angle from the target the rockets hits in the target area. The scoring equations is as follows: 1875 * 1 + 1 r+30 C+50 Where r = radial distance of rocket from target C = distance of rocket centerline to launch target area centerline (see Example below) Example: Lets imagine five rockets, Rocket A, Rocket B, Rocket D, Rocket E and Rocket F, have launched and this is where they landed ( see Diagram 1b). Rocket D wins First Place for the accuracy of trajectory. Who wins Second Place? Third Place? If r B = r A, Rocket B would win second place for this scenario, as it is closer to the trajectory path. This is because the trajectory path deviation factor “C”. C A is greater than C B, therefore Rocket B wins Second Place in lieu of r B = r A. and Rocket A wins Third Place for accuracy of trajectory, for this scenario. Also Rocket E and Rocket F will have a 50 point deduction for landing outside the target area zone.

7. 7 GENERAL AUDIENCE Launch Command Launch Operator Launch Controller HP Rocket Launcher Diagram 1a ** Note: Field markings in FEET.

8. 8 A B D Launch Target Centerline r CACA CBCB Scoring Example Scenario Diagram 1b HP Rocket Launcher Target Area Zone E F

9. 9 1. The pressure vessel must be ONE clear 2 liter bottle, see Diagram 2. 2. Water and air pressure will be the sole source of propellant. Before launching rocket, water volume (liters) and air pressure (psi) must be given. NOTE: The air pressure minimum is 30 psi and maximum is 80 psi. 3. Do not use metal, glass, or spikes to construct the rocket. *Use of these materials will automatically disqualify the team from the competition.* 4. On the bottom of the rocket, leave 7.5 cm from the throat of the exit plane clear of any coverings (paint, markings, drawings, etc.), see Diagram 2. 5. Maximum total height of rocket is 76.0 cm, see Diagram 2. 6. Nose-cone tip must have a minimum radius of 1.5 cm, see Diagram 3. 7. No forward swept type of fins are allowed to be used on the rocket. 8. The maximum fin width distance from the bottle is 10.0 cm (or 16.5 cm from center of bottle axis).

10. 10 Nose Cone Fin Pressure Vessel (Clear 2 Liter Bottle) Bottle Height (max. 76.0 cm) Rocket Clear of Any Coverings (min. 7.5 cm) Bottle Throat Diagram 2 Rocket Identification Throat Exit Plane

11. 11 Nose Cone Diagram Diagram 4 Fin Diagram Diagram 3 Cone Tip max 10.0 cm max 16.5 cm Min Cone Radius = 1.5 cm R

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13. 13  Each entry is to be prepared and submitted by the teams who will be participating in the Water Rocket Design Competition.  Patch designs must be submitted on 8.5”x11” paper.  All entries must contain the team name as well as a detailed explanation of the patch design  All teams participating in the Water Rocket Competition must be prepared to display their patch at the Mini-Design Review.  Patches must be hand-made original work.  Ink pens, pencils, markers or paint may be used. AT THE COMPETITION, THE PATCH DESIGN WILL BE JUDGED ON: ORIGINALITY - Innovativeness of the design. 30 CREATIVITY - Uniqueness of the information depicted 30 APPEARANCE - The attractiveness and neatness of the presentation 20 CONTENT - Design representation of the Team’s name and SECME theme 20 100 What is a “Patch”? It is a creative display that reflects the dedication and mission of the team. This symbolic picture must comply with the following rules:

14. 14 “Here is an Example...” Explanation of Patch The propelled rocket represents the school system, supported by the educators and students, following a path towards excellence. The radiant five 4-point stars symbolize the five colleges of Tuskegee University. Where as, the seven 8-point stars represent for the seven business units of United Technologies. The three distinct contrails steaming behind the rocket, symbolize the support offered through Students, Tuskegee University, and UTC. The ring before the rocket depicts the student’s path through the FASTREC program, returning full circle to support the efforts of the program. As we approach the new millennium, the sun over the horizon symbolizes of the induction of the new Water Rocket Design Competition into the FASTREC program. Accuracy, the focus of the contest, is represented by the target created by the outer ring, deep space, and the earth. The border is supported on either side by the chemical symbols respectively, for water and compressed air, which are used to propel the rockets.

15. 15 As a part of the Water Rocket Competition, the team is required to write a Technical Report describing the design, construction and operation of the Water Rocket. Reference numbers 1, 2, 3, 4 and 6 are required to be presented together within a maximum of 7 pages. Add pages as appropriate for number 5. Drawings, sketches, and tables may be included in an appendix (optional). 1. COVER PAGE (Required to contain): Title of Technical Report The team’s name Names and disciplines of team members Date 2. ABSTRACT (One half to one page summary of the Technical Report) 3. INTRODUCTION 4. DESIGN BACKGROUND 5. CALCULATIONS :Table of equations and constants Assumptions Mass flow rate calculations Drag calculated assumptions Trajectory calculations - location of bottle when all of its water is expelled - final destination point of bottle (Hint: diagram of time vs. distance traveled) {Calculations will be scored on units, assumptions, accuracy, etc..} 6. CONCLUSIONS/RECOMMENDATIONS AT THE COMPETITION, THE WATER ROCKET DESIGN TECHNICAL REPORT WILL BE JUDGED ON:  ABSTRACT10  DESIGN BACKGROUND 10  PAPER STRUCTURE 5  CALCULATIONS40  CONCLUSION/RECOMMENDATIONS20  GRAMMAR 15 100 points

16. 16  Overall Winner  Best Technical Paper  Accuracy of Trajectory  Best Technical Drawing  Best Patch  Best Design Review Presentation

17. 17 Overall Winner: Accuracy of Trajectory25 Technical Paper35 Technical Drawing15 Patch Design10 Design Review Presentation10 Innovative Design 5 100 Points: Best Patch: Originality(30) Creativity(30) Appearance(20) Content(20) Accuracy of Trajectory: Target Position (100) Best Technical Paper: Abstract(10) Design Background(10) Paper Structure(5) Calculations(40) Conclusions(20 ) Grammar(15 ) Best Technical Drawing: Resemblance(25) Scale(25) Name/Labeling(25) Appearance/Neatness(25) Best Presentation: Effectiveness (40) Creativity (10) Content/Communication (25) Appearance (25)

18. 18 Calculations Manual

19. 19 Although you may be anxious to begin building your rocket, some important decisions need to be made about launch conditions that can help ensure a more accurate launch. Remember: the goal of the competition is to launch the rocket a specific distance. Your task is to ensure your rocket meets that requirement. The following calculations will help you determine what choices to make to predict how far your rocket will go! These calculations are what is known as an iterative (repeated) process. First, choose the amount of air pressure and water to add to the rocket. Then calculate approximately how far your rocket is predicted to fly. If the resultant distance is not what you desire, choose another value for air pressure or water and re-calculate until you reach the answer you want.  Note: How your rocket really flies will not be exactly what is predicted here. The actual launch will vary due to real world elements such as wind changes, drag and differences in your rocket’s physical design that will not be accounted for now. These factors are left out to simplify calculations. But the following pages will give you a general starting point for choosing water and air pressure values and will show you their effect on your rocket’s flight. 

20. 20 Assume: ¬ Air pressure of the bottle rocket (from 30 to 80 psi) This is the amount of pressure that will be pumped into your rocket at the time of launch.  Choose the mass of water you will use to fuel your rocket. Remember mass= density x Volume. So, for example, if you plan to add 1Liter (volume, about the amount in a sports drink bottle) of water: Vol= 1Liter= 1000mL= 1000cm3 or 0.001m3  = Density of water= 998 (kg/m3)( a constant) mH2O =  x Vol (in kg) Find:  The Average Mass Flow Rate, , of the water. This is the amount of water (mass) that flows out of the “rocket nozzle”, or throat of the bottle over a period of time ( in a second). (kg/sec) Õ Where A= Area of nozzle (m 2 ) =  x r 2 (r is half the diameter of the 2 liter bottle’s throat) Õ cd= Discharge Coefficient= 0.98 (a dimensionless constant based on nozzle shape and flow conditions) Õ  = Density of water=998 (kg/m 3 ) ( a constant) Õ  P= (1+(Vi/Vf)(Pi)/2. (N/m 2 ) Õ Pi = Initial Air Pressure of bottle (N/m 2 ) Õ Ref: Atmospheric Pressure= 14.7(psi) (or 101,353.56 N/m 2 ) (a constant) Final air vol = Vf = 2L Initial air vol = Vi = 2L – initial water volume

21. 21 Find: ¯ Find the Thrust, f t, of the Rocket. This is the amount of force that pushes the rocket in a forward direction. ( in Newtons) Find: ± Thrust isn’t the only force acting on your rocket. There are also forces acting against the rocket’s motion. The weight (m ave x g) of the rocket acts against its attempts to move forward. Drag (f d ), (the force of wind acting against the surface of the rocket) also acts on the rocket, but for these calculations, drag will be neglected. (in Newtons) Õ f d = 0 since the rocket is very small. Õ M ave = ave. mass of the rocket= [M empty rocket + M h2o )/2 Õ g = gravitational acceleration constant= 9.8 m/sec 2 Find: ® Use your result from to find the Exit Velocity, V, (velocity at the bottle exit), of the water. (m/sec)

22. 22 PScholar’s note: You may be beginning to see how the amount of water you add affects thrust. The Range equation (equation 8) shows that the higher the water mass, the longer time the rocket will be propelled, therefore seeming to increase the Range. So why not just fill the bottle up with water and make it soar? Well, keep equations 6 and 7 in mind. The mass of the water, has two functions. It not only increases the time the rocket is propelled, but it also adds to the force acting against the motion of the rocket (weight), decreasing acceleration. Too little weight can also be harmful; it can make the rocket easily affected by the ‘neglected’ elements discussed earlier, like wind changes. A balance must be achieved. am ave f  (force in Newtons: N) Find: ² Find the Acceleration, a (m/s 2 ), of the rocket. Use the equation: g V RRange bottle  2sin 2   (in meters)  Where : taV bottle   m m ÕtÕt OH  2 Time when all of the water is expelled from the Rocket.   angle Rocket is being launched = 45 o ³ Now find the Range, R, or distance the Rocket will travel, for the water and air pressure conditions you have chosen.

23. 23 D c =.21D c =.20D c =.19D c =.23 ´ Now, multiply your Range (R) times the Drag Factor following the equation below: CHART A

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26. 26 So, you’ve calculated the Range, or distance the rocket is predicted to travel, would the rocket reach the target? Would the rocket fly too far? Vary the values for water mass and air pressure. How does the Range Change?

27. 27 How To Build A Water Rocket

28. 28 Newton’s First Law: The Law of Inertia The Law of Inertia says, “A body in motion remains in motion, a body at rest remains at rest, until acted upon by an outside force.” Inertia is the tendency to resist any change in motion. It is associated with an object’s mass. At rest: Forces are balanced. The force of gravity on the rocket balances with the force of the launch pad holding it up. In Motion: Thrust from the rocket unbalances those forces. The rocket travels upward until it runs out of fuel. FUNDAMENTAL PRINCIPLES OF ROCKET SCIENCE HEAVIER rockets have MORE Inertia, because they have MORE mass. MORE Inertia will offer GREATER resistance to a change in direction. Therefore the wind will have LESS effect on a bottle with MORE INERTIA. A LIGHTER bottle rocket has LESS inertia,because it has LESS mass. LESS inertia means the rocket will have LESS resistance to change in direction. As a result, the wind has a GREATER effect on the rocket’s path of motion. Wind Direction Desired Path of Motion   (Trajectory)

29. 29 Newton’s second law says: Force = (Mass)(Acceleration) F = ma The pressure created inside the rocket is the force (thrust). Mass represents the mass of the rocket and its fuel supply, which in this case is water. Therefore, the mass of the rocket changes during flight. As the fuel is used and expelled, the rocket weighs less and acceleration increases. Thrust continues until the water is completely expelled. Acceleration Newton’s Second Law: Force depends upon Mass and Acceleration F = ma implies that if the forces are the same, then the bigger the mass the smaller the acceleration. The smaller the mass, the larger the acceleration. Force

30. 30 Newton’s third law says, “For every action, there is an equal and opposite re- action.” A rocket takes off when it expels liquid. Action: The rocket pushes liquid outward. Reaction: The liquid exiting the bottle causes the rocket to move in the opposite direction. The Action (Thrust) has to be greater than the weight of the rocket for the Reaction (Liftoff) to happen. UP DOWN (Bottle + Water Mass) x (Bottle velocity) EQUALS (Ejected Water Mass) x (Ejected Water velocity) Essentially, the faster the fluid is ejected, and the more mass that is ejected, the greater the reaction force on the bottle. Newton’s Third Law: Action and Reaction

31. 31 Air Resistance causes Friction which will slow down the rocket. UP DOWN Air Friction (DRAG) MOTION MASS EXITING How to reduce DRAG? A more pointed nose cone will decrease the air resistance at the front of the rocket, but keep in mind that the minimum nose cone radius is 1/2 inch. Drag Equivalent to Air Resistance

32. 32 The center of mass (CM) is the point at which all of the mass of an object is perfectly balanced. Around this point is where an unstable rocket tumbles. Balance: Center of Mass and Center of Pressure The center of pressure (CP) exists only when air is flowing past the moving rocket. Flowing air rubbing and pushing against the rocket can cause it to move around on one of its three axes. It is extremely important that the CP of the rocket is located toward the tail and the CM is located toward the nose. When the CP and CM are located in the correct place, the rocket will tend to have more stability.

33. 33 Brainstorm The first step in the design of a water bottle rocket is brainstorming. Brainstorming is a problem-solving technique that involves the spontaneous contribution of ideas from all members of the group. Design Possibilities The following are illustrations of possible designs for the fins. Any variation of these suggested designs may be used and found to perform better than another when combined with various bottle designs. DESIGN AND DEVELOPMENT !Stop! All fins must be at least 4” from the throat exit plane of the bottle (see page 21). This schematic is provided solely to give examples of fin design. We encourage you to be creative.

34. 34 Choose best design Square fins create more stability, but also produce greater drag. Triangular fins introduce less drag, but yield less stability. Taking into consideration the principles of projectile motion, choose the proposed design which best satisfies the objective of the competition. Design Tips: Lengthening the rocket makes it more stable by moving the center of mass of the rocket closer to the nose. Adding fins to the rocket makes it more stable by moving the location where drag forces act on the rocket further to the rear. Adding mass near the tip of the nose cone makes the rocket more stable by moving the center of mass closer to the nose of the rocket. Heavier rockets have more inertia; therefore they have more stability. However, remember not too heavy, because the rocket needs to liftoff.

35. 35 MATERIALS AND CONSTRUCTION The following list of materials should NOT be used in any form in the construction of the water rocket. They are dangerous and could cause harm to the operator and those in the presence of the water rocket launch. Off-limit Materials Metal Glass Spikes and Antennas of any kind.

36. 36 Material and Tools Needed Pressure Vessel (Clear 2-Liter Bottle) Note: Be certain that your clear, 2-liter bottle is free of scratches, nicks, dents, and discoloration. Adhesive Foam mounting tape (approximately 1/16 thick, 2-sided adhesive) Carpet tape (thin 2-sided adhesive) Clear packing tape or Strapping Tape Use adhesive to bond fins, nose cone, and other allowed materials onto the water rocket Cutting utensils (Scissors, Hacksaw Blade, Utility Knife, etc.) Safety First: Children should be supervised at all times while constructing their Water Rockets For Fin Construction: Balsa and Bass Wood, Cardboard, Plastic, Foam Board, 1/4” to 1/2” thick Styrofoam & Etha Foam, Plastic Plates, and PE (2L) Bottle Material

37. 37 Tip: Using a Low melt glue gun is an excellent way to quickly bond fins. First clearly mark desired locations on the bottle prior to bonding. Try applying glue to a fin; then apply the fin to one of the marked locations on your bottle. This technique will aid in preventing your pressure vessel (ie. bottle) from deforming due to the ‘initially’ very warm temperature of the glue. Tip: Using a Low melt glue gun is an excellent way to quickly bond fins. First clearly mark desired locations on the bottle prior to bonding. Try applying glue to a fin; then apply the fin to one of the marked locations on your bottle. This technique will aid in preventing your pressure vessel (ie. bottle) from deforming due to the ‘initially’ very warm temperature of the glue. Fin Design & Construction Determine a fin pattern from your analytic design or trial and error. Use the recommended materials, however we encourage you to be creative. Keep in mind not to use the off-limit materials. Cut fins out of the material you choose. You can use as many fins as you feel are needed. Attach the fins to the lower section of the rocket using glue, Velcro, tape, or other adhesives. Tip: It is easier to attach fins to a bottle that is slightly pressurized. You can pressurize the bottle by placing the bottle with its top off in a freezer for 2-3 hours. Next, take it out of the freezer and put the top on very tight, eventually, the air inside warms and the bottle will become slightly pressurized. BUILDING YOUR WATER ROCKET

38. 38 Typical Fin Patterns THIS ATTACHED SIDE WILL HAVE THE SAME PROFILE OF THE SIDE OF 2-LITER BOTTLE

39. 39 Fin Patterns THIS ATTACHED SIDE WILL HAVE THE SAME PROFILE OF THE SIDE OF 2-LITER BOTTLE

40. 40 More Fin Patterns THIS ATTACHED SIDE WILL HAVE THE SAME PROFILE OF THE SIDE OF 2-LITER BOTTLE

41. 41 Nose Cone Design & Construction: Determine what material you want to use. Pattern the nose cone and cut it out. Attach the nose cone to the top of the rocket by using some recommended adhesives. Note: Remember use only the material recommended and maintain a nose radius of 0.5 inch or greater. Tip: Add ballast (weight) to nose cone (e.g. Styrofoam-peanuts, shredded paper, etc.) to shift the water rocket’s center of mass forward and increase its flight stability. Smaller amounts of more dense materials such as clay, sand, water, etc. may also be used as ballast. Remember not to use the Off-Limit materials. Nose Cone Design & Construction: Determine what material you want to use. Pattern the nose cone and cut it out. Attach the nose cone to the top of the rocket by using some recommended adhesives. Note: Remember use only the material recommended and maintain a nose radius of 0.5 inch or greater. Tip: Add ballast (weight) to nose cone (e.g. Styrofoam-peanuts, shredded paper, etc.) to shift the water rocket’s center of mass forward and increase its flight stability. Smaller amounts of more dense materials such as clay, sand, water, etc. may also be used as ballast. Remember not to use the Off-Limit materials.

42. 42 Preferred Nose Cone Construction- Water Rocket Assembly Method Step 1 : Cut the bottom off of a 2L Bottle (discard bottom). Step 2 : Carefully align top portion of bottle on the 2L bottle to be used for the pressure vessel. Step 4 : Tape/secure the joint between the nose cone stage and the pressure vessel. Step 3 : Rotate and observe your water rocket from several angles to ensure good alignment. Tips: - Remember to add ballast to your nose cone stage. - The pressure vessel should be in good condition free of scratches and dents)

43. 43 Option 2: Ballast can be added before or after you permanently affix the nose cone to the pressure vessel. Option 1: A) The neck can be cut off of the top of the nose cone as shown in Step 4; this will slightly improve the aerodynamics of the rocket. B) The resulting hole can simply be covered with tape. (Use a hack saw blade for cutting through the thicker material at the neck of bottle. Utility and other knives are NOT recommended for this process). BEFORE AFTER

44. 44 Option 3: The length of the Rocket can be increased by adding another bottle between the nose cone stage and the pressure vessel. Remember to stay within the dimensional limits for the competition. Note: Taller rockets will not necessarily perform better than shorter ones. Try to keep your construction/assembly process as simple as possible.

45. 45 Alternative Example of Nose Cone Construction Step 1: Cut a Circle out of thick stock paper or thin poster material (Using 16” or larger diameter). Step 2: Cut a line along the radius as shown. Step 3: Rotate the paper into a cone. Next Tape or Glue the seam to maintain the cone’s shape. You can adjust angle of the cone with more rotation. ( Keep mind that the base of your cone needs to be large enough to fit around the top of the pressure vessel). Step 4: If needed trim the base of cone as required so that it has a uniform fit with the diameter of a 2L bottle. Uniform Fit All- Around Here

46. 46 Step 8: Secure the resulting nose cone to the pressure vessel using an adhesive like tape, glue, velcro etc... Step 6: Uniformly trim top of paper nose cone to accept a craft foam or styrofoam ball or cone. Be certain to use some form of ballast (weight) to shift your rocket’s center of mass forward. Step 7: Add the foam ball or cone to create a 0.5” or larger nose cone radius.

47. 47 More on Water Rocket Construction: A) For lengthened rockets (Option 3 Page 20) A piece of 1/2” PVC Pipe can be used to align the nose cone to a second bottle prior to assembly with the main pressure vessel bottle. B) Join the bottles together on the PVC shaft and tape the joint between bottles securely. (Make certain tape lays flat on the bottle’s surface). C) Now, remove the PVC shaft and join upper nose cone stage to the pressure vessel. Carefully align the the stages. (Note: you will NOT be able to use the PVC shaft to align the nose cone and attached bottle to the pressure vessel). Other Tips A BC Pressure Vessel

48. 48 FINS: Whether your fins are wide or thin the primary ‘assembly’ objectives/considerations should be: 1) Make certain fins are aligned with center axis of rocket. 2) Be sure fins are well affixed to bottle to prevent separation or deflection/movement during flight. 3) Wider fins (1/4”-1/2” thick) provide a larger attachment/ contact surface. They can be securely attached using tape only and are useful for quick assembly & especially when working with young children due to ease of assembly. 4)Thinner fins (3/16” or less) are excellent for reducing the effects of drag, however, more effort is usually involved with securely attaching them to your water rocket. Thin fins must be very stiff once mounted to prevent movement during flight.

49. 49 5) A minimum of three fins are recommend for stable flight (4 fins are a good choice as well) 6) All fins should be spaced equally apart regardless of the number (e.g. 3 fins-120 o apart, 4 fins-90 o apart, and so on). Note: Aligned fins are recommended, particularly when competing. Tilting fins will cause rockets to spin. This action may slightly increase flight stability but will likely make it more difficult to ‘calculate’ how far the rocket will travel. In case fins are tilted to cause ‘spin’: They must ALL be tilted in the same direction. They should only be tilted slightly (e.g. 2 o to 10 o ). The fins should be equally spaced. It is strongly suggested that you try the aligned fin approach first!!!

50. 50 Examples Section

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64. 64 Construction Help

65. 65 Building Fins From 2-Liter Bottles 1. Cut Top and Bottom Off2. Flatten and Cut 3. Reverse the Fold and Recrease Note: The method of design and construction shown here is only an example. Use your imagination to create new designs using the recommended materials.

66. 66 An Example Only: Building Fins From 2-Liter Bottles 5. Trim to Desire Sweep, Add Clear Packing Tape Over Trailing Edge. 4. Add Double Side Tape Thin Carpet Tape (Trailing Edge) Thick Mounting Tape Center Spar Note: Adding clear packing tape keeps the leading edge from curling up and mounting tape add strength and stiffness to the fin. Tip: Add a smooth fillet of glue around the base of each fin.

67. 67 Nose Cone Fin Pressure Vessel (Clear 2 Liter Bottle) Bottle Height (max. 30 inches) Rocket Clear of Any Coverings (min. 3 inches) Fins Start (min. 4 inches) Bottle Throat Diagram 1 Rocket Identification Ballast Added to the Nose Cone (e.g. Styrofoam-peanuts, shredded paper, etc.) Throat Exit Plane Min Cone Radius = 0.5 inches

68. 68 Nose Cone Diagram Diagram 3 Fin Diagram Diagram 2 Cone Tip max 10.2 cm Min Cone Radius = 0.5 inches R Note: Make certain to construct the tip of the nose cone per the minimum cone radius (0.5 inches) for safe operation. max 16.5 cm