Sunday, March 29, 2015

A Pirate's Life II: Naval Combat

Last time we went through a game structure for ship movement during naval combat. It wasn’t super simple, but the result was (hopefully) something intuitive with strategic depth. Let’s do the same for the combat itself. The limitation of the ruleset is that it only keeps one player occupied at the table unless each player is commanding a different ship. So we need things for the other players to do that are also intuitive and have strategic depth, while not creating anything already covered in the rules.

Where to start? I’m tempted to go with officer actions, but a review of naval combat in the DMG itself is in order to know what holes need to be filled. A ship’s combat statistics are AC, HP, and Damage Threshold (the minimum damage needed to lower a ship’s HP). Weaponry comes in the form of Siege Equipment (DMG 255), each entry being an object that has AC, HP, Damage Immunities, and special rules. Cannon will be the average ship armament in a pirate campaign. It has an AC 19, 75 HP, immunity to poison and psychic damage. In addition, it takes one action to load the weapon, one to aim it, and one to fire it, meaning it takes a minimum of 3 characters to fire it in a round.

For the Naval Combat ruleset, a round is a minute long. A little research says rate of fire for cannons in the Age of Sail were about 100 shots a day, meaning 1 shot every 15 minutes. Wikipedia says by the late 18th century says a well trained crew could fire 2-3 shots per 5 minutes. Knowing this, firing a cannon every 6 seconds, even with 3 people manning sounds ludicrous. For the sake of verisimilitude and 1 minute rounds, let’s go with a crewed cannon being able to fire 1 shot every 2 minutes. This means one turn to load it, and one turn to fire.

Looking at the rest of the Cannon entry we have the stat block for the weapon itself:
Cannon Ball. Ranged Weapon Attack: +6 to hit, range 600/2,400 ft., one target. Hit: 44 (8d10) bludgeoning damage. If we were to consider the Cannon as a monster using the Monster Statistics by Challenge Rating table (DMG 274), the Cannon has an offensive CR of 6 and a defensive CR of 9, and a Final CR of 8. So your average gunner has the proficiency bonus of at least a 5th level hero, and a Dex of at least 16! I’ve got a feeling when they picked an attack bonus it was completely based on ship ACs and not thinking at all about who might be firing it.

At the end of the DMG, the Bandit and even the Veteran NPCs have a ranged bonus of +3, which is what I’ll be using for NPC controlled Cannons in my games. Next, the range seems fine. Needing to be 6 squares away to fire without disadvantage gives a good reason to get close, and 24 squares with disadvantage will keep encounters starting at long range from being completely dull. The AC and HP are pretty reasonable for a heavy metal object.

Damage means seven hits should destroy and average sailing ship. Cursory research shows some sailing ships have a traditional armament of 20 guns! Let’s we’re using 10 of those since the cannon are split between the two sides of the ship. If two Sailing ships from the DMG were within 6 squares of each other, each with 10 cannons to fire, and using the +6 ranged attack bonus each cannon has a 60% chance to hit. An average of 12 Cannons should hit per round dealing an average of 264 points of damage! At a range beyond 6 squares it each cannon has a 35% chance to hit. Meaning 3.5 hits should do an average of 154 damage a round. This will make naval combat an average of 2 rounds. That sounds a little too lethal. If we change the attack bonus to +3, two Sailing ships with 10 cannon each within a 6sq range should hit 45% of the time, and dealing 198 damage. Outside 6 squares 25% and dealing 110 damage. This lengthens combat to an average of 3 rounds at this range. Still too short. I don’t want to take any more off the attack bonus so let’s knock off some damage dice, 2 to be precise. The average damage is 33 per hit, making about two hits at point blank range deadly and four hits at ranges beyond 6 squares. With smart maneuvering battles could go for 5-7 rounds. Sounds like a reasonable length of time for any average combat. Damage threshold might make it a little longer. I’m not a statistician so not going there. Fog could really make things difficult from bad weather or magic users.

A note about ranges, I dug up’s source material for the ranges (a book on google called “Artillery Through the Ages”) and the descriptions there say while the maximum ranges were possible, gunners weren’t sure of hitting their targets at the extreme end of point blank range. Also, the distances are given in yards and max range for 6lb cannon could translate to 400 squares - not conducive to gaming. I’m going with the max point blank range being the furthest that can be hit with disadvantage, and roughly a quarter of that using a regular attack bonus. This will cause effective attacks needing to take place 4 squares away or less, which should be a good thing since it will add another round to the short combat length.

6 pounder. Ranged Weapon Attack: +3 to hit, range 400/1,500 ft., one target. Hit: 33 (6d10) bludgeoning damage.

Before moving on there’s one more thing I’d like to address about damage, which is the difference between hull damage and sail damage. It’s a idea from Sid Meier’s Pirates! that I’ve always liked. We could keep track of two separate hit points, but it doesn’t really add to player choice. Instead, I’d like to just make a note that when a ship loses a third of its HP it also loses 1sq of movement, and another square when it loses two thirds. When HP goes to 0 the ship has been scuttled (sailor speak for sunk). This way I get to give verisimilitude a nod without burdening the players.

Now that we’ve crunched the numbers we know how long a combat could take. I want the players do have more to do than roll a d20 and see if they hit, just like land combat has feats and abilities to use. However, a lot of combat has to do with movement and players not piloting a ship in this ruleset currently have less options than the pilot. This is a good time to get into officer actions.

In my games, each player is an officer on one of their two ships. This means two of my 6 players can have the job sailing, though only 1 is proficient. One is a sorcerer and will likely be using spells. Further one ship is a merchantman and not a good combat ship (we’ll play with different ship stats in another post). This means when given the choice they’ll take their most effective ship into battle, and I need enough jobs to occupy four other players. Here are a few combat roles for them to fill other than helmsman: master gunner, musician/orator, and surgeon.

The idea of the Master Gunner is to coordinate the other cannon crews and make them more efficient/coordinated in firing the cannon. Tribality has a few ideas that give meaningful choices. Once per battle one of the PCs can Rally the Crew, make a DC 10 check to get advantage on one roll. Then there’s Find a Weak Spot, which is the same as Rally but allows a player to do it for cannon fire every round. The only other other one involved directly with combat is Ordering a Broadside, which lets a player spend their action to give all cannons advantage, and do half damage on a miss. This one is not only broken but a little boring. Think about it, the player is essentially forfeiting his turn to grant others a bonus. Not fun, but we can fix this one.

So let’s say we let a player be in charge of a cannon crew and using their own ranged attack bonus (assuming allowing them to add their full proficiency bonus). That’s one crew with a much improved chance to hit and do damage. If we take Tribality’s idea of letting players be in charge of other full NPC cannon crews (while using the +3 attack bonus), in addition to the one their firing they now have other chances to hit. Nothing special so far, but what if we allow a cannon crew to use the help action. They forfeit an attack to give another crew (possibly the PC’s) advantage on an attack. This gives the players choices. Do I want to take my four cannon crews and have them all fire, knowing my crew only has an above average chance to hit? Or do I have two crews use the help action? Do I have a crew help mine to make I hit, or do I have them help another NPC crew to make an average attack into an above average one? Do I want to hold fire on two crews this turn so I can fire two crews every turn (remember cannons take 1 turn to load)? The player now has meaningful choices that doesn’t involve forfeiting their turn.

All we did for the non-pilot players manning the guns is give them extra attacks and the option to sacrifice some to make others better. This one hits the mark for simple and intuitive. After some playtesting I’ll see if this option provides enough choices for players or if it needs to be revisited.

With the last part of today’s post I’m going to focus on ammunition. I’ve never liked the idea of an archer with infinite arrows, and I don’t like cannons with infinite ammo, either. Another cursory search didn’t turn anything up on the price of round shot in the Age of Sail, so I’ll wing it. The PHB prices 1lb of iron for 1sp, and we’ll ignore the price of labor to smelt into balls. So assuming 17th century technology or earlier, the average cannon was a 6 pounder (feel free to correct me if any of this is inaccurate). A broadside for a Sailing ship is about 10 shots, so 6gp per broadside. Ship’s carry things by the ton, right? Six pounds into a ton comes to a messy number that we’ll round to 350 cannonballs. This comes to 210gp per ton, but we’ll call it a flat 200gp (this is info I’ll give to the quartermaster - yep, one of the player’s jobs is to keep track of cargo and treasure). We could get really detailed and make the players account for gunpowder, but my goal is to just make sure ammunition functions like a resource and not an at-will ability. Let’s say the gunpowder comes with the cannonballs. Like everything else I’ve presented, you can use or not use at your discretion.

Like regularly weaponry, naval combat needs a few different kinds of cannon. I like Tribality’s idea and stat block for the Swivel gun - AC 19, 60hp. For a little historical verisimilitude of 16th century cannon let’s make a few adjustments.

Falcon/Swivel Gun/3 pounder. Ranged Weapon Attack: +3 to hit, range 300/1,200 ft., one target. Hit: 17 (3d10) bludgeoning damage.

Here’s a smaller one:
Esmeril/Half-pounder. Ranged Weapon Attack: +3 to hit, range 200/600 ft., one target. Hit: 11 (2d10) bludgeoning damage.

I’d like to put out more options though I’m having trouble finding info on ranges and other pertinent data to come up with other kinds of cannon with verisimilitude. Let’s see if what you come up with. If you know something about naval artillery in the Age of Sail, I want to hear what you have to say. Next time we’ll give non-combat roles the attention they deserve, such as the musician/orator and the surgeon. Below is the Sailing Mishap table I mentioned last post. Enjoy!

When a Sailing check misses the DC by more than 5, roll on the following table:

Sailing Mishaps Table
Broken Rudder. This ship can’t make Hard Turns until the rudder is replaced. Takes a Carpenter 1 hour to fix.
Almost Capsized. 2d4 crew fall overboard in the square you started at the beginning of this turn.
Ripped Sail. Speed reduced by 1 square until replaced. Takes two crew 5 minutes to fix.
Slipped the Wheel. Disadvantage On next Sailing check.
Loose Rigging. Speed reduced by 1 square this turn.
Nothing. You got lucky.
Lucky Screw Up. The wind changed at just the right moment and gave you a boost. Advantage on the next Sailing check.


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