How would showers/continuous rain affect the performance of the various types of siege engines (catapults/ballistae/et al)? As adversely as bows/crossbows?

(As a side question, btw, do the various inclement weather conditions that affect a bow similarly affect a crossbow--or is one hardier than the other?).

Does not a Trebuchet rely on a dropped weight creating turning motion a round a pivot? (ie no 'strings'). I guess this would mean it would be little affected mechanically.

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Plots and schemes are the same thing..

I agree--I think the Trebuchet would be little affected.

Trebuchet's wouldn't be affected mechanically.
But the crew servicing the engine would definitely not be at 100%.
Anyone who's tried to handle rigging in wet conditions will know that has a substantial effect.

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Leave the gun, take the cannolli.

In our gaming group bows are unstrung until it is time for combat. Otherwise they would stretch out the cordage and lose tension. Game mechanic used is that the effective range is halved if you wish to keep them strung, a suitable discouragement.

Any tension bow though will be affected in the cordage is kept taut. As far as humidity is concerned it simply swells the fibers, thus increasing the effort needed to get the desired range. Modern synthetic cordage is not affected as much, but natural fibers are a real bear.

More importantly it makes judging the angle needed to get too that distance very difficult. In addition the firing condition it will constantly be changing as water is "wrung" out of the cordage by successive pulls. Which is why our ancestors who used a bow in that time period kept a least one (and usually more) bowstrings coiled up in their helmets. Kept them reasonably dry, warm and (somewhat disgustingly) well oiled.

As a side note, the (very good) silk bowstring was seldom seen west of Arabia/ Eastern Mediterrean region. Archers in England usually used hemp, cat-gut and (for the truly desperate) linen for bowstrings.

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...and I'm not dead yet...

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.

For catapult:
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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Si vis pacem, para bellum
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