Ship Combat - Take me out to the Black tell them I ain't coming back

This is a work in progress. I am working on converting a 3.5 modification to piloting rules to 5th ed. So look it over and offer any suggestions. I will be editing this a lot over the next few days

Preparation

Formations
Ships on the same side can be in formation or docked before combat begins.

Crew and Passenger Locations
It should be noted which ship component each PC and important NPC is in. Unless a ship has been surprised, you can assume that everyone is at their duty station.

Initiative
Each ship makes an initiative check, using the initiative modifiers of the helmsperson.
Combat Round

A combat round takes 1 minute. A ship at high speeds takes longer to manuever into position than individuals creatures battling one another. A 1-minute turn also gives PCs chance to position themselves at any location on their ship at the start of their turn. Should regular combat occur (as a result of boarding action), that combat can be played out as normal. It is assumed that the entire boarding action combat takes place within the 1-minute ship turn.

A ship’s turn has the following phases:
Action. PCs and NPCs choose a ship action.
Maneuver. The ship’s maneuver is resolved, which will give the ship’s distance and bearing to other vessels.
Ramming. If the ship is on a collision course with a target, the helmsman may opt to ram the target.
Weapons. The ship’s weapons shoot.
Action during a Turn

On a ship’s turn, each PCs and important NPCs can move to any part of the ship and choose one of the following actions. The order in which characters move and act is usually not important. There are six actions: command, navigation, rigging, helm, weapon, damage control. Some actions require the character to be in a particular ship component.

Multitasking
If a character spends the whole turn in the same ship component, they can perform two different actions. If they do so, they have disadvantage on all related rolls.

Help
Each action can only be performed once, per turn (e.g. two characters cannot both perform the Rigging action). However, a PC in the same location can use the Help action (PHB p. 192).

Command

Navigation
Location. Helm or Rigging.
A character can take the Navigation action to help the ship avoid a hazard (such as debris dropped by a jettison). This is an Intelligence check with a DC determined by the type of hazard. On a success, the ship may make a Dexterity saving throw made to avoid the hazard.

Rigging
Location. The character must be in a rigging component or an oars of the void component.
A character taking the Rigging action helps the crew operate the rigging or oars. The character makes a DC 15 Strength check, adding their proficiency bonus if they are proficient with Vehicles (Spelljammer). The character may instead make a DC 15 Charisma check if they are acting as a botswain in charge of 8 or more other crew operating the rigging. On a success, the ship has advantage on any maneuver checks it makes this turn.

Helm
The helmsperson chooses a ship maneuver (see below). They can instead take a Ready action (PHB p. 193).

Direct Weapons
Location. The character must be in a weapon component.
A character taking the Weapon action helps oversee the attacks made by the weapon battery. The character makes a DC 15 Dexterity check. On a success, they add their proficiency bonus to the attack roll made by the weapon battery.
Alternately, the character can have a weapon component take a Ready action. The Ready action is triggered if a vessel attempts to ram the character’s ship, and the weapons may attack before the ram is resolved.

Damage Control
Location. A damaged component.
A character with the appropriate tool proficiency and set of tools can attempt emergency repairs. For T+ ships, two such characters must be present. Typical required proficiencies are carpenter’s, sewist’s, smith’s or tinker’s tools. On a successful DC 15 ability check, the component is jury-rigged and is not considered damaged.
Jury-rigging is a temporary repair. After 1 hour, the vessel makes a DC 10 Constitution check when the component is used. On a failure, the component is damaged again. On a success, it continues to function for another 1 hour.

Rescue
Location. A destroyed component. Creatures in a component when it is destroyed might become trapped by wreckage. A character (or two characters for T+ ships) may make a DC 10 Strength check to free the survivors.

Ship Maneuvers

Once all actions have concluded, the ship maneuvers.

Maneuver Check
Some manuevers require the helmsperson to make a maneuver check. This is a Dexterity check, using the ship’s Dexterity. In the case of an opposed maneuver check, the target vessel also makes a Dexterity check. In addition, compare the level of the spell slot expended by the maneuvering ship, and the spell slot expended by the target vessel during its last maneuver. The ship that expended the lowest level spell slot has disadvantage on the contested maneuver check.

Facing
Facing is which of your hull sections (bow, center or stern) is facing your opponents. The helmsperson chooses the facing from those allowed by the maneuver. Facing determines which weapons can be fired. Only the hull section that faces your opponent can be targeted by enemy fire.

Ranges
Far. 1200 feet.
Strike. 480 feet. A quick, close approach.
Engaged. 480 feet. This ship matching the direction and speed of the target.
Close. 120 feet. The ship is making a fast, direct approach to the target, and may choose to ram.
Contact. 30 feet. If a ship achieves Contact range with a target that made a Drift maneuver, that target can be grappled and boarded.

Vessels that are in formation are 60 to 90 feet from one another.

Outmaneuvering
When a ship is Outmaneuvering another, it may approach its target from a different facing to the one that normally faces the ship. It may approach the bow or stern instead of the center; or choose the center facing instead of the bow or stern. Outmaneuvering status is lost when the target ship chooses a maneuver (other than uncontrolled drift).

Closing
You attempt to move your ship closer to a target vessel. The helmsperson must expend one spell slot. If the target’s last maneuver was a Drift, you must succeed a DC 10 maneuver check. Otherwise, make a contested maneuver check. If the target’s last maneuver was Evasive Action, their effective spell slot level is twice normal for the purpose of determining advantage in the contested check.
If you succeed, choose one of the following:

  • Set range to Strike (480 ft.)
  • Outmaneuver the target
  • If you were already at Engaged range, you may set range to Close (120 ft.).
    If you succeed by 5 or more, choose one of the following:
  • Set range to Strike (480 ft.), and Outmaneuver the target.
  • Set range to Engaged (480 ft.)
  • Set range to Close (120 ft.)
    If you were already at Engaged range, choose one of the following:
  • Set range to Close (120 ft.), and Outmaneuver the target.
  • Set range to Contact (30 ft.).
    If you fail, set range to Far (1200 ft.).
    Facing. Your bow faces all opponents.

Controlled Drift
Set range to Far (1200 ft.), unless it is at Engaged or Contact.
Facing. Choose your bow, center or stern to face all opponents.
Evasive Action
You make it more difficult for opponents to close in or attack your ship, or to set up a Retreat. The helmsperson must expend one spell slot.
Set range to Far (1200 ft.).
Attack rolls against an evading ship are made with disadvantage.
Facing. Your center or stern faces all opponents that are not Outmanevuering you.
Hold Course
You are on a steady course without getting near to a particular vessel. The helmsperson must expend one spell slot of 3rd level or lower.
Set range to Far (1200 ft.), unless it is at Engaged or Contact.
Facing. Your center or bow faces all opponents that are not Outmaneuvering you.
Retreat
Your last maneuver must have been Evasive Action or Retreat. If your last maneuver was Evasive Action, the helmsperson must expend one spell slot.
Set range to Far (1200 ft.). At the start of your next turn, you have escaped from all ships that did not successfully take a Closing manuever against you.
Facing. If the helmsperson expended a spell slot, your stern faces all opponents that are not Outmaneuvering you. Otherwise your bow, stern or center faces all opponents.
Uncontrolled Drift
Any ship that does not have a helmsperson that took the Helm action or otherwise did not take any other maneuver.
Any object that is not a ship is in an uncontrolled drift.
Set range to Far (1200 ft.), unless it is at Engaged or Contact.
Facing. Same as previous facing.
Ramming

If a ship is at Close range, the helmsman may chose to ram the target. This occurs before weapon attacks are resolved, but might be interrupted by the target ship’s Ready action. The helmsman must make a ram attack roll.
The attack bonus is Dexterity modifier + proficiency bonus, made against the AC of the hull section facing the ramming vessel. The helmsman may choose to have disadvantage on the attack roll in order to target a specific component in the target’s facing hull section. If the ship has multiple rams, make an attack roll for each ram.
The damage roll is 1d10 * (the spell slot level used in the ramming ship’s closing maneuver + the Constitution modifier of the lighter of the two vessels)
Both ships take this damage. If the ramming ship had a ram, it has resistance against this damage. The ramming ship takes damage to a random component in its front hull; the rammed ship takes damage to a random component in its facing hull. See Hits and Damage.
Weapons

After the maneuver phase, weapons that are fully crewed may fire.
Bearing
Fixed weapons may only fire at a target if the hull section they are in is facing the target. For center-hull weapons, it does not matter if they are on the port or starboard, as a ship can roll to bring all weapons to bear throughout the turn.
Turret weapons in the bow can fire at targets that the ship’s bow or center is facing.
Turret weapons in the stern can fire at targets that the ship’s stern or center is facing.
Turret weapons in the center can fire at any target.
Range
A weapon component will be at normal or long range, or be out of range, depending on the range between the ships.
Rate of Fire
Weapons may fire many times in a 1-minute turn. However, each weapon component gets one grouped attack roll. The total rate of fire of all the weapons grants a bonus to the attack roll, and the amount by which the attack roll succeeds indicates how many individual attacks hit.
Each type of weapon has a rate of fire (RoF), as shown on the siege engine table. Bows, crossbows and thrown weapons have a RoF of 10.
Rate of fire grants the following bonus to each weapon group’s attack roll:
5–8 = +1
9–12 = +2
13–16 = +3
17–24 = +4
25–49 = +5
50–99 = +6
100–199 = +7
200–399 = +8
400–799 = +9
etc, each doubling of RoF gives a +1 bonus.
Targets
If the target’s bow or stern faces the attacker, only that section can be targeted.
If the target’s center faces the attack, any hull section can be targeted.
Exposed components (e.g. rigging) can always be targeted.
If the weapon range is Normal, the attack can be directed at a particular ship component in any section that it can target, incurring disadvantage on the attack roll.
Personal Weapons against Crew
Personal weapons (longbows, etc) targeting a particular ship component can choose to fire at the crew in that component. This is often their only option if the target’s damage threshold is greater than the damage they can deal.
If the RoF is high enough to grant a bonus, instead of making an attack roll, the crew in that section makes a group Dexterity saving throw. The DC is 15 if the crew is in an exposed component (i.e. rigging) and 10 in other components. Crew in core components cannot be targeted. The DC is increased by the RoF bonus.
If the RoF does not grant a bonus, make individual attack rolls. The DC is Crew in exposed components have half cover. Crew in core components have total cover. All other crew get three-quarters cover. All hits are distributed equally among the crew.
Attack Roll
The attack roll bonus is the normal value for that weapon:
+6 for ballistas, springalds and cannons
+5 for mangonels and trebuchet
The attack roll bonus for personal weapons is +2, regardless of individual proficiency or ability.
If a character successfully used the Direct Weapons action, add their proficiency bonus.
Add the RoF bonus.
If the weapon range is Long, the roll is made with disadvantage.
If a particular ship component is being targeted, the roll is made with disadvantage.
Hits and Damage
On a successful attack roll, roll 1d6 to determine which component in the targeted hull section was hit (unless a particular component was targeted).
One shot hits, plus one shot for every 2 points the attack roll beat the AC, to a maximum of the attack’s rate of fire.
Roll damage for each hit. If there are many hits, the DM can group them together to reduce the number of rolls: roll damage once for each group. For example, if there are 9 hits, roll for damage 3 times: each roll is the damage dealt by three hits.
If a hit deals less damage than the target’s damage threshold, it has no effect.
If the damage was greater than the target’s damage threshold, the hit component is damaged.
If the damage was twice as much as the damage threshold or greater, the component is destroyed.
If the component was already damage, it is destroyed instead.
If the component was already destroyed, the next undestroyed component in that hull section is hit instead (if component 6 is destroyed, hit an undestroyed [Core] component in that section, then loop back to 1)
Smaller and larger components
If a component slot holds undersized or half-sized components, all the components in that slot are damaged or destroyed.
An oversized component is not damaged or destroyed until half or more of the component slots it comprises of are damaged or destroyed.
Ship Integrity

Every time a component is destroyed, the ship must make a Constitution check. The DC depends on the number of destroyed components:
0—2: DC 5
3—5: DC 10
6—8: DC 15
9—11: DC 20
12—15: DC 25
On the first failed save, the ship has compromised integrity. It has disadvantage on maneuver checks and on weapon attacks.
On the second failed save, the ship is destroyed.
Damaged and Destroyed Components

A damaged or destroyed component does not function, with the following special cases.
Armor
Damaged. Damaged armor has 1 less AC.
Destroyed. Destroyed armor has 2 less AC: even destroyed armor provides enough structure to absorb or deflect blows.
If a hull section has more than one armor component, use the highest AC.
Cargo
Damaged. Half the cargo in it is destroyed.
Destroyed. All the cargo is destroyed.
Spelljammer Helm
Damaged. The ship does not benefit from the helm’s Ship Rating bonus.
Destroyed. The ship cannot maneuver (so is in an Uncontrolled Drift).
Berth
Damaged. Vehicles are unable to launch.
Destroyed. Vehicles in the berth are destroyed.
Volatile Components
Some components do not react well to being hit.
A weapon component that includes cannons
Vats of acid
When one of these components is damaged or destroyed, the vessel makes a DC 15 Constitution check. On a failed save, the component is damaged again (transferring to the next component if it is already destroyed as detailed above).
Fighting Monsters

The above rules can be used if a ship battles a monster. Monsters do not have hull sections, components or damage thresholds: weapon hits reduce the monster’s hit points as normal. Monsters do not have a facing, so its attacks are always considered to be facing the ship. Monsters native to the Flow can maneuver, and its statblock will note what its effective Ship Rating is, and what its attack ranges are.
Examples

A hammership is at Collision Course range from its target, a Gargantuan-sized Ship of the Line. Its bow is facing the target’s center hull, so only the mangonel can be fired (since the ballista is in the stern). The target’s center hull has wooden armor (AC 15). The mangonel’s rate of fire is 2, so there is no RoF bonus. The mangonel’s attack bonus is +5.
An attack roll of 9 or less will be a miss.
An attack roll of 10—11 means one shot hit.
An attack roll of 12 of greater means two shots hit (as it would beat the AC by at least 2 points)
A PC makes the attack roll and scores 19; two hits! 1d6 is rolled to determine which center-hull component is hit. The result is 6, the cargo hold.
The Ship of the Line’s damage threshold is 20. A mangonel shot deals 5d10 bludgeoning damage. The damage rolls are 18 and 27. The first shot has no effect, while the second disables the cargo hold (destroying half the cargo in that section).

Ship Combat - Take me out to the Black tell them I ain't coming back

The Crown of the Stars - A Spelljammer 5e Tale Frost815 Frost815