|Building your own rocket can be as simple as duct taping some plastic fins to a cola bottle to as complicated as a multi-stage, electronically controlled recovery, carbon fiber reinforced rocket. I have put a few things into words that could be helpful for someone wanting to build themselves a water rocket.|
Most any soda bottle will work. Pop bottles made of PETE plastic are designed to hold the pressure of the CO2 fizz to +100psi. Bottled water containers generally are not. Do not use these, they can explode. Well, I guess anything will explode with enough pressure behind it... he he he
Anyway, 20 oz bottles are more aerodynamic than a 2 liter bottle, but
they do not hold as much air. The new 24 oz bottle are nice because
they are the same diameter as the 20 oz but are longer. The more
volume you have the more oomph you will have behind your rocket. This said,
if you can join the bottles together, you may attain a higher altitude.
Your goal for fin materials: strong, waterproof, light, and aerodynamic.
That said, you can use corrugated plastic boxes, old broken CDs, credit/gift cards, balsa wood, styrofoam... the list goes on and on.
I personally have been using laminating plastic. I take the thickest laminating sheet and send it through the laminator without anything inside it. Then I take it out and put it inside of another sheet and run it through again. I end up with 4 layers of clear laminated plastic. I then cut them to the shape I want and heat up the end I want to glue to the rocket. when it gets hot enough, I bend 1/4" of an inch over at a 90 degree angle. This gives me plenty of surface area to glue it to the rocket.
Joining the fins to the rocket:
|Recovery: Lawn darts or parachutes,
that is the question.
Lawndart: If you make a rocket with no parachute, try duct taping a tennis ball the the nose. This will make your rocket last a lot longer.
Inertia cap over parachute:
Tomy Timer: named after the Tomy toy company
My design is a tube that sits on top of the rocket. I put the
tomy timer on the inside. I cut a few holes to access the jamming
hole and to stick the winding knob through. I cut an oval out for
the parachute compartment and I tape in a section of plastic bag to make
a pocket for the parachute to sit in. I also make a door to close
over the chute and tape it on at the bottom to make a hinge.
You can make a two stage rocket using a staging device that operates off pressure from your rocket. It is relatively easy to make. Bruce Berggren has a description on how to make one.
Using a nozzle can dramatically change the way your rocket performs. I have used some "tee" nozzles on my FTC rockets. A tee nozzle is one that sits inside of the rocket on top of the launch tube. When the rocket comes off the launcher the nozzle is forced to the bottom of the bottle and it tries to exit the neck of the bottle. Only you have an o-ring to stop it from coming all the way out. The remaining water has to come out of the hole in the nozzle. This makes the acceleration phase longer. The size of the hole controls how your rocket accelerates.
The one pictured is made out of 1/2 PVC pipe, a 1/2 PVC pipe coupler, an O-ring, and a piece of plastic that I turned down on a lathe. The 1/2 pipe has a deep grove in in for a thick O-ring to sit in. I glued a pipe coupler close to the O-ring but then cut it down to let the O-ring fit tighter against the pop bottle top. The hardest thing to make was the plastic nozzle. I made this one a bit elaborate, but all I really needed was to get something to block off the pipe and then drill a hole through the end.
Bernard Willaert is where I found electromagnetic deployment for the chute
I used Bruce Berggren's launcher design (dead link)
Tim Sumrall has some good ideas (dead link)
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