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Inspired by the Punkin' Chunkin' contest in southern Delaware (yeah, it used to be in Delaware), myself and a couple fellow mechanical engineers decided to create a pneumatic water balloon launcher.

So we bought some 4" PVC drain pipe, caps, reducers, and a 2" PVC ball valve from Home Depot.  The bottom section of PVC pipe was capped on one end and we drilled and tapped in a quick release fitting for filling.  The 2" ball valve was at the other end of the tank then we widened back out to 4" for an open ended barrel.

The first couple shots were at low pressure but we quickly determined that a person rotating the ball valve was too slow - the projectile would leave the barrel before the valve was completely opened.  So we put a pneumatic actuator on the valve handle to rotate it as fast as possible.

The next few shots at increasing pressures were promising but eventually the water balloon started to fail in the barrel and we would only shoot tiny water droplets mixed with some balloon shreds.

Next step was to create a sabot.  The first was probably too fancy.  We created a hot wire cutting rig to make a nearly hemi-spherical cut in some styrofoam (what a smell!).  This worked well but eventually broke.  The next was just a folded piece of cardboard.  This held up remarkably well for many shots.

Firing over an agricultural field at the south end of the UD campus, we peaked at just over 1,000 feet.  Not bad but the current record for Punkin' Chunkin' is close to 4,700 feet.