Trebuchet Combat


Water balloon fights are fun. Throw in two or more trebuchets throwing water balloons at each other and you add a dash of history, ballistics, engineering and teamwork that lends itself to off-beat competition. The object is to score direct hits on the opposing trebuchet and its team. What is needed are a couple of trebuchets that can fling water balloons a decent distance; I think 150 feet is far enough to make it interesting. A trebuchet with a standard eight foot 2x4 throwing arm with a dumb bell weighing 90 to 100 lbs. can achieve this with ease, and isn't too expensive to build.


Each trebuchet has a captain who adjusts the sling length to vary the range and pulls the launch trigger; a loader who grabs the launch arm after a launch, pulls it down and engages the trigger; and an armorer who tends the water balloons and loads the sling once the throwing arm is cocked and locked into the trigger by the loader. Working as a team the rate of fire can be increased through motion analysis and practise.


The battlefield needs a couple of launch sites free of overhead wires and tree branches, and one launch site needs to have a linear distance of at least twenty feet in line with the other launch site so that one trebuchet can be positioned at different points along it and will be explained below. If the trebuchets are designed with wheels (floating carriage type) then the launch sites must be flat and paved. An empty parking lot will do just fine, but so can a paved, level path or sidewalk.

Limited Ammunition

The teams start with a dozen water balloons, each of uniform weight (nominally a little less than two pounds). Both teams fire on each other until all the balloons have been launched, unless it is agreed that it is a sudden death competition, i.e. where the first direct hit decides the winner. If all balloons have been fired by both sides with no hits, the average distance of the closest three balloon strikes is taken and the team with the lowest average distance wins.

Game Day

At the beginning of the competition the distance between the trebs is decided by chance (distance is written down on two or more cards and one is selected from the others by pulling one from a hat); this injects some initial uncertainty into the mix. Neither treb team will know ahead of time exactly how far apart they will be other than both are within the maximum range of the other. It ensures that the teams will need to make range adjustments (varying the sling length is the fastest way to accomplish this). Once the distance is determined and the trebs are transported to their respective battle positions, neither treb is allowed to move other than from recoil from a launch.


Trebuchet combat should be safer than running with scissors. That being said, the trebs do have moving parts the operators need to stay clear of during a launch; in the heat of competition it is the team captain that has the best overview to keep the team out of harm's way.

The team captain directs the loader and armorer and is the only one to pull the trigger. The team captain must be vigilant so that he or she pulls the trigger only when the loader and armorer are clear of the machine and standing to the side of it.

If the loader doesn't cock and secure the throwing arm to the trigger correctly a misfire can result. Even though speed is important, the loader has to be consistent; the captain needs to crosscheck the system when it is in a cocked state. If one of the team trips over the trigger rope a premature firing will expose the team to needless hazard; to mitigate this the rope should be a bright color, only the captain should pick it up, and it should only be picked up immediately before executing a launch.

Except when the loader is pulling the throwing arm down and the armorer is putting a water balloon into the sling, nobody should have any part of their bodies above or below the throwing arm. At no time should any team member stand directly in front or in back of the treb.