My two sons were introduced to water rockets last year at our Cub Scout Pack 85. We made just a plain two liter rocket with cut off top of another bottle for the rocket top. I machined out two wooden nose tips for each rocket and glued on some triangle fins. Added some paint and we were off and running.
See the below pictures from our first attempt at rocket construction. We actually had the best altitude(s) from our two rockets than everyone else in the pack.
In fact I was asked to help lead an informal water rocket class two weeks ago to help the kids get started in their construction of their own designd for this years water rocket event.
- Mason's first rocket
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This years event would be different is what I decided after last years event. I wanted to go bigger and more sophisticated.
Mason's rocket this year was going to carry the patriotic theme again but with one extra wow trick. We decided to put a parachute on the rocket for same recovery.
Pack members looking at Mason's rocket.
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Last years rockets were dangerous. The wooden nose tip caused the rockets to lawn dart into the soft ground. After a couple of lauches I decided to pull the tips off and just use the bottle caps with ballast for the rest of the evening.
Mason's rocket is made of four one liter smart water bottles. Two are spliced for the booster and one is for additional air capacity. The fourth bottle (with stars) is the parachute housing containing the spring loaded syringe as the spring extending section that exposes the parachute allowing the chute to deploy.
The nose tip is a rubber bottle nipple that is used to feed calfs'. It was purchased from a farm and feed supply store. Actually Mason put a Lego astronaut in the tip.
The nose cone is an interferace fit with the third bottle that was shaped with an electric iron to get the correct shape while pressurised. I got the idea of the syringe as a sort shock from someone on this board. He just the syringe with just air in a compressed fashion for an ejection mechanism. I just added a compression spring of the correct length and spring constant. This work beautifully. Just sometimes a little tricky getting the nose the stay compressed befor launch. The syringe is about a 50 cc size.
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After our first flight, one fin cam off and we had to epoxy it back on for our second flight.
Me packing the chute for our second flight.
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Parker's rocket is modeled after our interpretation of the first atomic weapon that was used on Hiroshima in WW II. Little Boy is made up of about five two liter bottles spliced together. The last bottle an intact lower part of a two liter bottle. I then took a four in bottom of a bottle and inverted onto the top and glued the two together with epoxy. Before the last portion was glued together I made a straight sided sleeve for a straight wall two liter bottle and applied a coat of PL adhesive to the inside slipped all the pieces together an allow to cure. The created a cup at the top of the rocket when viewed from the top.
After all was cured and pressure tested, fins (the boxed end) were attached. The box is constructed of foam core project board. The Square is one piece that at predetermined lengths was scored through the first layer of cardboard and through the foam. At the prdetermined cuts the foam was cut out at 45º angles to allow for the piece to fold up and make a perfect square. Only one glue joint was needed for the square (box as Parker calls it). The bottle was then pressurised and measurements were made for the corner supports. The were cut from the same foam board and the whole assembly was attached with PL adhesive. Once the assembly had cured several coats of OD green flat paint were applied along with two inch letters and the radioactive warning sign.
Back to the cup, I made a parchute for both rockets out of nuylon rip stop material. I used a hobby hot knife to cut the rip stop material. Eyelets were used were the shroud lines were attached to the canopy. Elastic was used for shock lines that attached the parachtes to the rockets. All ends of the elastic were sown with synthetic thread. The shock cords were attached with screw eyes that were first pilot drilled and thread into the plastic and epoxied into place.
Another trick we had up our sleeve the event was that we placed a grenade water balloon in the "cup" with the parachute this added an extra amount of applause.
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For next years event I want to use staging and parachutes. I know I will have plenty of questions. This site is wonderful and there are a lot of talented indivduals who contribute to water rockets here.
Thank you for you post and ideas it has been great to work with my two sons and see their excitement and enthusiasm as well.
Todd