We have build a real-sized catapult, for our medieval fighting and sieges.
The beast used more than 60 meteres of natural hemp rope, 200kgs of woods, metal accessories, chains, etc.
When you charge it with the crank you start earing noises and crakcing from wood and rope.
The first times we used it we were impressed.
An overall intimidating picture.
W've have laso built a man-operated trabuchet, where men provided the "weights" with their arms. It's not exactly the same of a counter-weighted trabuchet, but it is close enough.
Rain is a killer.
the rope is the engine. You will torque the rope in opposite direction simultaneously. The energy is stored in the hemp, since it's very elastic (doesn't work with synthetic ones).
For this the catapult can be operated only for a certain amount of time, then the rope must be relaxed a bit.
Wet rope loose much of it's elasticty and the overall performances are scarce.
The ironings will rust easily, and will work much worse.
The wood can become softer and start to dent, fall and deform.
For trabuchet the rope issuses are lessened, but the other points apply as well.
The overall structure will be "softer" and more inclined to damage.
As noted by someone esle, even the servants and the projectiles themselves are affected.
My two cents.
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