off vertically at 100PSI and went into a flat stable glide. It was lost
some 300 feet from the launch site on the roof of a building. A sketch
with approximate dimensions follows. I have seen and heard of behavior
similar to this several times since with similar rockets.
In 2005, The Alameda Middle School Water Rocket Group built a number of
gliders with two liter bottles and typically oversized fins glued
directly to the bottles. We hot glue tack the fins to the
bottle, and then reinforce the joint with PL Premium construction
adhesive. Bottles that glided typically had fins half way up
also had a great success cutting the neck off a three liter bottle,
inserting and gluing (PLP) a two liter bottle neck inside it, and with
oversized (by eye) fins, at about 100 psi convinced this one to fly out
of sight. We never did get it back as it sailed off into the
neighborhood behind the bleachers. We were launching from the
center of the football field in the school's rocket range.
*An open nozzle launch uses the original
of the bottle's mouth for the nozzle. This is not the only way to
these rockets, nor is it going to result in the highest performance. It
probably the easiest. Some people like to fasten other sorts of nozzles
inside the bottle mouth. (There is agreement in the water rocket
that an open mouth is a maximum desirable opening.) An intriguing
is the so-called T-nozzle, which employs a full size launch tube for
acceleration, but then a fitting drops into the nozzle to reduce and
the thrust over time. For something with as little mass and as much
as a soda pop bottle, this can make a lot of difference.
WaterMotorLaunch Tube Sleeve'O' Ring
This drawing portrays my version of Ian Clark's Cable Tie Release. Cable ties are used by electricians to bind wires together. I have only shown one on the left, but I use as many as fit around the launch tube. There is a #94 rubber 'O' ring between the upper and lower parts of the launch tube. The upper part of the launch tube is snug on the inner sleeve, but is removable to exchange with others of lengths appropriate to my motors. (Long motor / long tube.) The ties are held engaged with the collar on the motor by a ring of flourescent tube cover about two inches long. To increase visibility from the pumping station, there is red electrical tape around the ring. The ring is light enough to hold itself up with friction before pumping starts. The pull down strings go to a metal ring. The remote release string is tied to a second ring on the launcher base, it passes up through the upper ring, back down through the lower ring and out horizontally to the launch crew.
Assembly is a bit tricky. I use light rubber
and masking tape to hold the ties while I position them. I place a
on the launch tube to line up the tie heads with the bottle's collar.
everything looks right, I put some cable ties around the rest (Drawing
on the left), and tighten them. If everything still looks good, I smear
warm epoxy all over this section. (Warm so it flows better.) Then I
all the ends flush. If one desires to experiment with different bottle
placings, one can use hose clamps without the glue, but it results in a
clunky looking job and the clamp can get in the way of the retaining
Contact me, Gordon McDonough, at firstname.lastname@example.org