This is what we started out with: raw, dry wood, mostly Douglas Fir and Red Oak. We measured each piece and determined which pieces would be used for each final part in the catapult. Then, they were rough sawn into approximate dimensions. Each piece was then shaped and planed using power equipment.

The catapult/treb consists of three main sections: the throwing arm, the counterweight, and the frame.

The first thing we did was to take the wood and cut it roughly to size. The blocks pictured above are the result.

Then it was time to shape the throwing arm. It is octagonal and tapered, which made for some pretty complex woodworking. To get the right shape, we built a fixture that guided the router to shape the square chunk of wood into the throwing arm.

The throwing arm is curved, such that the base is thicker than the tip. To make the shape correctly, the long square block of wood is placed in a fixture and the shape routed onto the topmost surface. The arm is rotated 45 degrees and the same shape is recut. This happens eight times until a uniform octagonal shape is made.

I used a router on a wooden float to cut the shape. It took quite a while to remove all that wood.

Below, you can see the peg we cut into the end. Eventually, there will be a rope sling attached to the arm that will actually hold the projectile. One end of the sling will be looped over the peg.