Rocket Launcher

Simple Water Rocket Launcher

This is a simple water rocket launcher that you can have your scouts build. It is easy to operate, safe and lots of fun. This launcher is based on a design found on Stan Pope's web site (see sources below for URL of the web site).

Materials List

one 8 foot section of ½" PVC (this is white plastic pipe you CAN NOT use for drinking water)
one section of ½" CPVC (generally TAN and can be used for drinking water)
one ½" PVC 90 degree elbow
three ½" PVC end caps (get the flat ones. Some are rounded. The flat ones are easier to drill)
two ½" PVC T-connectors
one tubeless tire valve
two pipe straps and some screws
one board about 12x12 or 12x8 to mount the launcher on.
Duct Tape
CPVC-PVC cleaner and glue (cleaner is generally purple. There is a clear version that looks better.)
Glue (either PL Premium or Household Goop)

Tools Needed

Tape measure
Pencil for marking cuts
Hacksaw for cutting pipe
File and/or razor knife for removing rough edges/burrs from cuts
Screw driver
Drill
Hammer
½" wood drill bit
Rag to wipe excess glue from joints

Assembly Notes

Have the boys do the measuring and cutting.
The boy can also glue the parts together with some adult assistance, but remind them that the glue sets almost instantly. Where a piece needs to be glued in a proper relationship with another piece, it may be advisable to have an adult put those pieces together.
Have the drawing of the completed launcher visible so the boys can use it like a blue print. Have them lay the parts to be assembled on top of the drawing to help them visualize how they are assembled. You may wish to enlarge the picture some to assist this process.
The launcher can easily be made in one evening.
Read the notes on how properly glue PVC below.

Assembly

Take one of the ½" PVC end caps and drill a ½" hole in the end. Put some glue (PL Premium or Household Goop) around the hole inside the cap. Insert the tire valve through the hole from the inside of the cap and pull through until rubber locking ridge (located toward bottom of valve) snaps through the hole. You have now assembled part H & J. This activity is best done ahead of time. I don't recommend that the Scouts drill the hole unless you have a good vise to hold the end cap while drilling.
Now cut out parts A, C, both E, F, and L from the ½ PVC pipe. Using the file and/or razor knife, clean the cut edges so any extra material is removed.
Glue the H&J assembly onto one end of part A. Then glue part B to the other end of part A.
Now glue the other end of part B to part C.
Holding the tire valve pipe assembly so it is pointing straight up(perpendicular to the ground), glue the first part D (that holds the launch rod) so the top of T-Connector is pointing up (perpendicular to the ground).
Next glue each part G to one end of each of the two part E's as show in the diagram. Glue the part E's to the second part D t-connector. Into the top of part D, attach part L. This is the anti-tip assembly.
Take the anti-tip assembly and glue into the first part D (holding the launch rod) so that the anti-tip assembly is parallel to the ground and the launch rod/tire value are point straight up, perpendicular to the ground. (It is more important for the launch rod to be pointing straight up in case the tire valve wasn't glued quite parallel to the launch rod).
Cut out part I from the ½" CPVC pipe. Using the file and/or razor knife, clean the cut edges so any extra material is removed.
Use the file to slightly round the bottom edges on one end of part I (the ½" CPVC). Next use the file to slightly widen the opening on one of part F. Now insert the rounded end of the CPVC into the widen opening of F. Using a hammer, whack F tightly over I (or I tightly into F) as far as possible. The fit will be so tight you won't need to glue it into place. If desired you may, but you will still have to whack it into place, so work fast before the glue sets.
Now glue part F into the top of the first part D t-connector.
Lay the launcher onto your board. Use the pipe straps to fasten the launcher to the board. Put a strap over part L and part C. Additional straps, if available, could also go over one of the part E's, and part C near where the pipe leaves the board.
Take the Duct tape and wrap it in a band around the bottom of the CPVC launch tube. Form it so that it is narrow at the top and thick at the bottom of the band. You want to be able to slide a pop bottle over the launch rod, and have it fit tightly over the duct tape. The duct tape will provide a friction fit, to hold the bottle into place until the pressure forces it free. You will have to periodically replace the duct tape as it wears out.

PVC Glue Instructions.

To successfully glue PVC & CPVC follow these simple rules.

Only glue a few pieces at a time
Have good ventilation as the glue and cleaner produce fumes and are aromatic. Keep containers closed when not in immediate use.
Wipe pieces to be glued so they are free of dirt and grease.
Apply cleaner only to the surfaces you are working on right then.
Apply glue to the first part, then the part it goes into, then put glue on the first part again.
Quickly insert part one into part two, and twist slightly to seat the part (1/4 to ½ twist). Make sure parts end up in correct relationship after the twist. Remember that this glue sets instantly.
Wipe excess glue from joint.

Using the Launcher

Take a 2-liter bottle and fill between 1/3 & ½ with water.
Tip the launcher on its side and slip the bottle over the launch rod, down onto the duct tape.
Put launcher back flat on the ground and with a twist of the bottle, seat it tightly over the duct tape.
Clear the launch area
Apply air pressure to the launcher using either a hand air pump or a mechanical air compressor. For safety do not exceed 100PSI.
When the air pressure exceeds the friction holding the bottle down, it will launch with a whoosh and streak skyward. If pressure reaches 100psi and the bottle does not launch, remove the air source, then depress the valve stem and release the pressure in the launcher. Standing next to, but not over, the launcher use a stick to whack the bottle loose. When loose, re-tighten on launcher and re-apply the air pressure.
When done, drain the pipe as best you can.

Safety

2-liter pop bottles can take up to 100-120 PSI of pressure without much problem. The Science Olympiad uses 75psi for their launches. I use 100psi when I can. Bottles that have been abused, or weakened by inappropriate adhesives can burst under pressure. It is important to keep people away from the bottles while they are being launched.
Bottles leave the launcher at tremendous speeds 30+mph (more like 60-80mph). It doesn't feel good to get hit by one. So never lean over a bottle on the launch rod. Make sure launch rod is always pointing up when applying air pressure to a rocket.
DON'T USE DRY ICE to pressure the water bottle rocket!!! Dry Ice can pressurize your rocket so fast that the rocket may explode rather than launch. Don't lose fingers for doing something stupid.
Bottles that go up, must come down somewhere. Please launch rockets in open areas so they don't land in streets or on your neighbors car or roof.
Liquid Nails, Super Glues, and HOT Glue Guns have been known to weaken the plastic used in pop bottles.
PL Premium (a construction adhesive found at Home Depot next to Liquid Nails) and HOUSEHOLD GOOP work good for making rockets. PL Premium is best for gluing bottles together to make bigger rockets. Household GOOP is best for gluing fins onto bottles.

Credits/More Information

The basic design of this launcher was found on the Internet in some scouting web pages created by Stan Pope. Please visit his site to see the original design and other scouting information. The web page is: http://members.aol.com/StanDCmr/rocket.html

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