Heat Curled Edges
Building STRONGER Rockets
From Plastic Soda Bottles
by Gary Ensmenger
02/28/98
Heat Curled Edges is new technology for
building Water Rockets. It's something I developed (remember who should
get credit for it) last year as a means to strenghten the bodies of the
rockets. Heat Curled Edges has dramatically changes
the way we approach making water rockets. It's easy and safe, and almost
always gives good results. Just follow my steps below for "tried &
true" proceedures.
Brief background. In the last
couple years, many of us tried reshaping PETE(soda bottles) with heat. Sure,
heat (about 160 degrees F or more) from any source can easily changes the
shape of these PETE bottles. The problem was that the finished product was
a mutilated bottle that was totally useless.
The challenge is to reshape the bottles
into something useful. Clifford Heath, from Austrailia, was the first "water
rocket scientist", to develop a proceedure for thermoforming the bottle
by making a "Guppy Nose". With careful exposure of heat and some
internal pressure, Cliff was able to bulge the bottom of the bottle into
a bullet nose shape.
This inspired me to try for a second useful reshaping process.
I soon came up with the "CURLED EDGE". It's fast, relatively safe,
requires no pressure, and versitile. It's become the backbone of all my
new rocket designs in 1998.
Currently, there are different types of heat curled edges.
(1) The Full Curled edge. This is used for two purposes:
(a) "Circumference Layered Splice Joint", used to join to bottle
bodies together.
(b) "Removable Tail Fin Assembly", a handy way to reuse fins on
many different rocket bodies.
(2) The Slight Curled edge. This is used to make
a water reservior in the nose cone for extra weight, for ballast.
HOW-TO-DO-IT Heat Curled Edges
It starts with clean, DRY, bottles with the labels removed.
Depending upon the application, the bottle is cut at the appropriate location
around the circumference. A metal plate, like a circular saw blade, is place
upon the element of a SMALL electric element. On my stove, MEDUIM setting
is perfect temperature. When water droplets begin to SIZZLE on the metal,
it is the right temperature. Hold the opposite end of the bottle & LIGHTLY
press the cut edge against the hot metal. The plastic will begin to curl.
Try to keep the sides of the bottle perpendicular to the hot metal, so the
curled edge will be straight.
Here's a great tip: As soon as you have the desired amount
of FULL CURL, immediately lift the bottle off the hot metal, and then press
it over a glass applesause or pickle jar (room temperature). The glass jar
will SET the shape the softened circumference into a perfect circle. It
puts a beautiful shape to the curled edge.
Another trick when making a "Circumference Layered
Splice Joint", used to join to bottle bodies together: Even though
you attemped to make the curled edge perpendicular, it's probly at a slight
angle. That's ok. Before you glue, pre-assemble the three parts and INDEX
the parts by rotating the edges until you see an alignment of the curled
edges against themselves. Look at drawing. Figure A show misalignment and
Fig B shows optimal alignment. I use a felt tip marker and mark the bottle
(as shown in red in Fig B). Diassemble and the reassemble with PL Premium
Construction Adhesive.
....that's all for now....... to be continued......more
later