1.  Two 2 Liter Bottles from a Carbonated Drink  (Non Carbonated bottles burst at low pressures)
2.  Fin Material: Paper/Foam Laminate or stiff cardboard or other stiff but light weight material
3.  Duct Tape
4.  10 nickels
5.  Hot Glue
6.  Tennis Ball

1.  Hot Glue Gun
2.  Sharpie Pen
3.  Scissors
4.  Box Cutter
5.  Sand Paper
6.  Rule or other straight edge

1. Remove labels off of both bottles.  Remove the Cap Ring from both bottles.  (Cut off with scissors)  Be very careful not to puncture or scrape the bottle that will be used for the motor.

2.  Cut the bottom off of one of the bottles using a box cutter to start.  Scissors can be used after it is started.  Follow a mold line around the bottom or use the Sharpie pen to make a line to follow.

3.  Screw a Cap on tightly on the bottle with the bottom removed.  Turn bottle with cap downward and place 10 nickels in the neck of the bottle.  Cover the top nickel with hot glue.  Add hot glue up the inside of the neck at least 1/4 inch.  (Note that the glue will stick better if the bottle is clean and it will stick best if the surface is roughened with sand paper before using the hot glue.)  Allow hot glue to cool a couple of minutes before setting it down.

4.  Fit the first bottle over the bottom of the second bottle.  Roll the bottles on a table top to help make sure that they are inline with each other.  Use duct tape around the circumference to hold them together.

5.  Design and make fins from a stiff but light weight material.  (Do not use metal!)  Position the fins far back on the rocket, but make sure that the fins will not hang below the neck of the bottle as they may interfere with the launcher.  Attach the fins using duct tape on both sides of the fin.

6.  Mark the tennis ball with a Sharpie pen around the edge of a bottle cap.  Use a curved x-acto carving knife and a sawing motion to cut the circle out of the ball, just inside the line.  This is best done in advance)  Push the ball over the end of the nose of the rocket up to the bottle flange, where the Cap Ring was originally.  This should be a tight fit so that the ball does not easily pop over the flange.

7.  Decorate the rocket using colored marking pins (water proof) and or letters and numbers cut out of duct tape.  It can also be decorated with stick on labels.

Who ever is acting as Launch Control should inspect each rocket for the integrity of the motor bottle (no scrapes, cuts, or punctures) before applying air pressure.  Fill the motor bottle with 1 liter of H2O from a one liter bottle.  Pressurize with 60 to 80 psi air.  Keep everyone back 15 feet.  Launch!



“ I will always be safe with things that might be able to hurt people and property if used in an improper manor.”

Safety is an important issue in many activities, including water rockets. Safety precautions unique to water rockets include:

* Only use bottles that are made to contain carbonated ("fizzy") drinks, other bottles are not made to withstand the pressures used with water rockets, the rectangular shapes in many non-carbonated drink bottles are deformed by pressure.

* Assume if it can go wrong it will go wrong. Bottles may explode. Poorly designed or incorrectly used launchers may tip over. Release mechanisms may fail, causing launches to occur spontaneously, or for the pressurized rocket to remain stuck on the launcher. An abort procedure should be rehearsed. Disconnecting the pump from a long air-hose extending from the launcher will allow the rocket to depressurize, provided the launcher and air-hose do not have valves prohibiting air escaping.

* In the US, Science Olympiad events do not use more than 75 psi or 500kPa pressure in 2 liter bottles. We will be using only 80 psi. The burst point on most bottles is 120 psi and above. Smaller diameter bottles will withstand greater pressure, so are safer than 2 liter bottles at the same pressure. Damaged bottles may explode more readily than others. Nobody should be within a few meters of a pressurized bottle; this calls for a remote (e.g. string/pneumatic operated) release mechanism. Exploding bottles are a rare occurrence if the above precautions are followed.

* Falling rockets may descend at great speed, possibly causing serious injury. Rockets should be fired away from observers. In Japanese distance competitions, launches are angled 60 degrees from horizontal. Everyone in the vicinity should be observing and be aware of what is about to occur, launches should be announced. If observers are made to wear bicycle helmets they will not only be safer but will see that the potential danger is a matter taken seriously.

* Cutting bottles can be dangerous. It is safest to make a small cut with a knife, allowing a scissor blade to be inserted, then use short-bladed blunt-nosed scissors to continue the cutting where desired. Adults may use knives for most cutting, but with children it is best to provide them with a bottle, which already has a small knife-made cut, so they may continue with scissors.


  1. The result must be a water rocket capable of launching and returning to earth.
  2. The water rocket must include guidance (fins), propulsion (pressure bottle),  and recovery systems (parachute).   
  3. The pressure bottle that serves as the engine for the rocket cannot be cut, punctured, sanded or damaged in any way or the rocket will not hold the air pressure. Soak in warm (Not hot) water with some soap to get the glue to come off and only use a sponge not a scrubby as plastic is VERY soft.  
  4. The water rocket will never carry live animals or a payload that is intended to be flammable, explosive, or harmful.
  5. The pressure bottle will NOT have anything but tape used on it. This is because unless you build the rocket under pressure it will lose fins and anything that is attached when it is pressurized. Tape will give more and can be reattached if needed. Duct tape works best (See the “Red Green” show).
  6. The fins can't extend any lower than where the bottle begins to narrow into the neck. Otherwise they will interfere with the launch pad.   
  7. The rocket must not weight more than 350 grams empty.
  8. The rocket must launch as one complete unit, but may come down as separate pieces as long as they are all attached by string or cord.   
  9. On launch day, the rocket will be launched once and it will be judged on how straight it flies, how long it takes to reach the top of its flight (Apogee) and how long it takes to reach the ground or leave the sight of the judges.
  10. You can “Sleeve” the rocket. This means a sleeve is put over the pressure bottle so that the thrust is pushing into the sleeve.  You may glue and attach to the sleeve that you can’t do to the pressure bottle. Do NOT use any glue to attach the sleeve to the pressure bottle.


The water rocket will be made of lightweight materials such as paper, wood, rubber, and plastic 2 liter bottle suitable for the power used and the performance of the water rocket. There will NOT be the use of any metal for the nose cone, body, fins, or any other part of a water rocket (not even staples) as these will hurt people if they reach high speed.

·      Plastic two-liter bottle

·      Thin Soft or flexible Plastic, cardboard, flexible foam sheets for fins (hard but not too hard) Cut up bottles and then folded over work good.

·      Plastic trash bags, cloth – for the parachute

·      Other two-liter bottles for nose cone and other components that you think up

·      A weight that is not hard like rubber tennis ball


 Glue - tape - band saw / jig saw / hand saw / scissors (cutting fins)   - string / cord (to keep everything together) - disc sander/spindle sander/hand sander or sand paper (fin shaping)



Webmaster Queen Anne Cub Scouts,
May 28, 2014, 4:05 PM
Webmaster Queen Anne Cub Scouts,
Sep 22, 2010, 9:27 PM