ADVANCED STOMP ROCKETRY
Note: I have experimented with launching maple seeds
and paper helicopters up so they are released at their highest point, but I
have not yet refined them enough to make up instructions. There is also a waterproof
version of the rocket I make out of a cut-up 2-liter soda bottle.
And then there is a fascinating phenomenon that I call
"paddle wheeling." The rocket goes straight up as usual. But instead
of diving straight down again, at its peak it starts to spin and glide, making
a gentle landing. I have had rockets that spontaneously did this, but I had
a maddening time trying to reproduce the effect when making another rocket.
However, I got an e-mail and, later, pictures and details from a gentleman named
Rob F. His son Rolf seems to have made a breakthrough in reliably making this
kind of rocket (Rob calls them "sidewinders)! I print below the e-mails
verbatim. Rob starts out talking about a competition and gives some tips. The
second e-mail goes into the sidewinder, and the third gives more details. I
hope other people will jump in, experiment and share their results.
Hi Slater,
Let me start by saying your web site is awesome! I was able to keep two 11
year olds and a 13 year old occupied all day on Saturday (note, there were no
computer games or TV shows involved) testing various air rocket designs. Some
of the hypotheses were validated by testing, but I was surprised at some of
the results.
We are having an air rocket competition this Thursday and I was wondering
if you had any "secret tricks" of increasing hang time. I tried (very
dismally) to add a parachute. I think the key is going to be altitude as the
competition is based on hang time. Here's what the boys and I discovered: Long
rockets go higher than short ones. Card stock rockets go higher than magazine
(could be weight related). Fins which cause the rocket to have more spiral slow
it down, thus reducing altitude.
I'm in the process of optimizing our design in preparation for Thursday. Any
ideas you could offer would be appreciated. I'm particularly interested in experimenting
with adding weight and with using a 3-liter bottle instead of a 2-liter bottle.
It seems that more air might give more altitude. I'm also considering plugging
the end of the launcher to get more pressure buildup before launch. As you can
tell, I'm taking this much to seriously :-)
Take care,
Rob
Hi Slater,
Well, our competition was on Thursday and of 21 rockets entered (three were
mine), I swept all three categories (head-to-head, longest hang time (during
competition #1) and longest distance)! My rockets were all made of 1/2 sheet
11x17 card stock, split lengthwise. This was a competition between mostly engineers.
I was very happy.
The reason I'm writing this, though is to let you know what my 11 year old
son came up with that wound up winning the hang time competition (9.43 seconds!).
On Wednesday night, before the competition, he was playing with one of my discarded
rockets (I was still in final design mode). 
He
came in the house and said, "Hey Dad, come out and see what I did to the
rocket!" He had bent the fins in kind of a strange angle (I'll try to describe
it in a minute) so the rocket had spin on it. We launched it and it went up
straight, turned to level, and spun on the (very slow) return to the ground--hang
time 9.4 seconds! The best I'd previously gotten from any rocket was 6.5 seconds.
I worked on getting the center of balance right (wraps of duct tape just above
the fins) and managed an even better time by the beginning of the competition.
Note from Slater: Based on my experience, this wrap of
duct tape near the bottom of the rocket--or rather the weight from it--is very
important, not only the bend of the fins.
Here's what he did (I'll send pictures later this week--I have the rockets
mounted outside 
my
cube for bragging rights for couple of days :-) The fins were mounted at the
base of the rocket. He bent the fins twice. The first was to bend the tail of
the fin at a 45 degree angle (to produce clockwise spin). Then, he bent the
first fold in half (back to parallel with the body of the rocket). This produced
a spin and a braking action that caused the rocket to literally float back down.
It didn't get as much height (of course), but it produced fairly consistent
results. You should have heard the cheers as it made its maiden flight! It was
near the last and the previous best time was 7.2 seconds (one of my other rockets).
Something like this:
NOTE: Just see the pictures above Hope that comes
through ok...like I said, I'll send pictures later this week. Another thing
that made a huge difference in the head-to-head competition was the nose I used
on my straight-up/straight-down rocket (which won that competition--sidewinder
had one bad flight :-( I bought 1 inch styrofoam balls which I cut in half and
taped on top of the rockets. Our head-to-head was done in the parking lot and
you had to use the same rocket for what ended up being five launches. The nose
was crushed after each flight, but I just pulled it off and taped on another
for the next round. The body of the rocket remained nearly undamaged, while
I watched the competitor's rockets break in half on impact.
Well, enough bragging. You have a great web site and I (and my son, his friends,
and my coworkers) had a *wonderful* time building and flying our air rockets.
Take care!
Cheers,
Rob
To: Slater Harrison Subject: Science: Sidewinder Rocket Details
Hi Slater,
Yes, I was able to reproduce the "straight up, sideways down"
design.
Before the competition, I had a duplicate rocket to the one for the
actual competition and I went out during lunch to figure out how much
tape to use. For my rocket, made from 67# Vellum Bristol card stock
(that my lovely wife uses in her art instruction business--she made me
say that), five wraps of duct tape provided consistent results. I went
in and wrapped Sidewinder and the rest is " Rocket Championship"
history. The rocket is 17 inches long and the center of gravity is
almost exactly six inches from the base of the rocket.
I've attached pictures of the rocket. One is a kinda close-up of the
rocket. The second is one that shows a better picture of how the fins
are bent (I think the way they were bent causes the straight upward
flight path, because it produces a spiral), and the third is a picture
of my 11 year-old rocket scientist.
One thing I forgot to mention about the competition (that a coworker
reminded me of today) was that one of the main crowd-pleasing aspects of
Sidewinder's second flight was that the other rocket went much higher
and everyone expected me to lose....until the rocket turned over and
floated to the ground!
Take care, Rob
Note: There is only one finished link here so far. It
shows how to make a quick-change adapter so that you can simply un-screw an
old bottle and screw on a new one in seconds. The part is made from a bottle
cap, melted over a candle and re-formed. To see the instructions for a quick
bottle changer, click here.
In the summer 2004 I will add sections about sending
up payloads of paper helicopters and maple seeds. The basic idea is to form
a paper cup at the top at the top of the rocket. When the rocket gets to the
apex of its ascent, it turns over and dumps out the payload. Sometimes it works
great. But after the cup hits the ground a few times, it can form a crinkle
that the payload gets stuck on. So I'm developing the idea a bit more.
Then there is what I call "paddle wheeling."
If the rocket fins are taped on more toward the middle of the rocket rather
than the bottom, sometimes it will go up the usual way but not speed down. Instead
the rocket spins a lot and glides, making a soft landing. If you cut an ordinary
piece of paper to be a rectangle about 1" by 2", then drop it, you'll
see what I mean by paddle wheeling. It's very cool, but very complex. If the
fins go up too much, the rocket veers off wildly--perhaps dangerously--on the
way up. Needs more work.
Finally, I will have a link with instructions for making
waterproof stomp rockets. They are made from a narrow piece of cut-open soda
bottle which is rolled 90 degrees to the way it was first curved, then taped.
The fins are made of soda bottle, too. I've had a major breakthrough with the
design of these. More soon.
To make an adapter to quickly change
the bottle on the launcher click here or on
the picture. |
I'd like to know how this project goes for you. I'm happy to answer questions
about it. Feedback from you is an important way for me to know what works and
what needs clarification.