Naval catapults and ballistae and their issues

Problem here is very simple, they aren't efficient enough in the mechanical sense. Any catapult or trebuchet capable of launching projectiles big enough to cause significant structural damage reliably would be absolutely massive, and ballista may never even get there in the first place because of material limitations.

Furthemore, weight of projectiles themselves is an issue - since they are moving slower than cannonballs, they need to be bigger to get the same destructive effect, and that weight has to be carried by the ship that already has trouble because it is primarily oar-powered and needs to house and supply the oarsmen. Trebuchet projectile weighs about 50-500kg, cannonballs in Borggard's Ordnance are 4-42 lbs, so about 2-21 kg. That is the reduction of ammunition weight by a factor of about 20. I couldn't find any good data on powder weight, but later ratios suggest about 1:4, so total ammo weight is 5-52 lbs, a still huge ten to one in favor of cannon.

There is also accuracy, but we'll get there.

All of this means that there is no way to have siege engines for direct hull destruction, so you only take ones that are good for destroying either people or sails. These can be made a lot smaller, but there will still be only a few of them, and they will therefore have supplementary role instead of being the primary weapons.

Fire attacks

Using flaming arrows or fire pots was definitely done - but boy, do you have to be careful when using them. First of all, there are all the range and accuracy problems we'll get to later, but let's say you actually managed to set the enemy ship on fire.

First of all, you can't capture that ship - it's on fire and will sink with all the booty and lucrative people to ransom and/or sell into slavery. It's not talked about too much, but slave trade was well and operational around the European frontiers, especially in the Mediterranean and along the Eurasian border.

Second problem is, you are at close range and now you have a ship that will sink, and is made for ramming. That enemy crew now has a hell of a motivation - literal fire lit under their bottoms - to ram and board you, and will fight extra hard to sieze your ship. It's the only way for them to live, and if they can't, then there is a solid chance of them taking you down with them, because a ship that is on fire just rammed you.

You can still use fire attacks, and people obviously did, but you need to make sure all of these things are accounted for - maybe you are on city walls, maybe wind is in your favor, or the enemy ship is too slow to catch you.

Last issue is that, well, you need to have an open fire somewhere on a wooden ship, and should that be lit when the enemy is shooting at you, an unlucky hit could very well spill your own incendiary weapon - sure, you can remove fire source from where you store weapons, but wood will still burn, and you just made logistics for your fire attacks harder.

I suspect that one aspect that made Greek fire work was that it was relatively safe to store, but who knows.

Early cannon and how they solve nothing

Problem of early cannons is that they aren't that powerful in proportion to their weight. Sure, you have some like houfnice that are meant for short range and light load, but those meant for sieges?

Spoiler: Hussite tarasnice and houfnice, c1400
Show


Spoiler: Dardanelles gun, Ottoman top of the line bombard, 1465
Show


So while the weight of ammunition has been somewhat mitigated, the weapons themselves are extremely heavy if they are made big enough to damage ships. That means you can't fit enough of them on a ship, since they have to be spinal mounts.

Quote Originally Posted by Pauly
It took the development of 2 things
1) Wheeled naval gun carriages so that the recoil of the gun was not transferred to the deck which allowed guns to be side firing.
2) gun ports that allowed the guns to be run inboard for loading
That allowed sailing ships to deliver effective broadsides that ended the galley as a main battle weapon.
Not really, the order of inventions is almost the other way around.

Both gun carriage and gun ports were feats of engineering people were capable of well before advent of age of sail style gunnery. Problems are in cannon metallurgy and gunpowder manufacture - you needed cannons that were small enough to fit on a broadside (cannon exploding on you is not a good thing on land, and even worse on a ship) and powerful enough to punch through ship hulls (there were significant improvements in manufacturing process of powder, and they don't get a lot of attention). Once they were developed and it suddenly made sense for them to be fitted on ships, gun ports and carriages were promptly developed.

Accuracy - by volume

This is the largest problem here, and will remain an issue until mechanical ranging computers will solve it. It is really hard to fire from a moving platform, really hard to hit a moving target, and even harder to do it of either or both are moving in such a way that their range changes. The maths there gets fiendishly complex, and some of the methods, like integration, will not be invented until Newton-Leibnitz feud.

What's more, should the range be far enough, there is the possibility that the defending vessel will change course after the shot was fired and before it hits. With gunpowder, you need a lot of range, but something slower like a trebuchet will run into this issue a lot sooner - Warwick castle treb has top speed of 70 meters per second, so even if that speed was constant - and it isn't - a target a kilometer away would have 14 seconds before the rock hit.

That means one thing - you either need to be really close, or have a lot of guns so that some of them hit, and preferably both. Age of sail cannons had effeective range in the ballbark of a kilometer or two at best, but real ranges were often as little as 50 meters and most often well under 500.

Conclusion - useful for TTRPGs

So, if you want your ships to be able to wreck each other realistically, you need a weapon that fulfills the following:

  • enough power to reliably damage vessel hulls
  • enough accuracy to hit at least somewhat reliably
  • ammunition of which enough can be stored in the space available
  • safe enough to not damage own ship


Provided you have no magical range-finders capable of calculating firing solutions (or hitscan weapons, in the forms of speed of light beams or just really fast projectiles), your weapons have to be short ranged and you need a lot of them for a broadside, which means your weapons also have to be:

  • small enough to fit multiple of them to the sides
  • ammunition needs to be even smaller


And that is a pretty stringent list of requirements.