From YPPedia

When one ship (in sea battle) attempts to move into the square that another ship is occupying, the other ship is rammed and both ships suffer damage. If a ship hits a rock, it takes a small amount of damage. The edges of the board also act as rocks, except for the far edge (opposite the safe zone) of a flotilla, blockade or the entrance zone of an Atlantis board, which acts like a series of wind pieces facing inward.

There are four size classes of ship, as indicated in the Ram damage table below. If the ramming ship is in a larger size class than the ship being rammed, the smaller ship is usually "pushed" out of the square it was in, although collision mechanics can often be more complicated than this.

When a ship hits another ship, it inflicts damage upon the other ship based on its size. For example, if a sloop rams a merchant brig, the sloop receives the equivalent of 0.667 medium cannon balls worth of damage, and the merchant brig receives the equivalent of 0.5 small cannonballs worth of damage.

Ram damage

Ship Name Equivalent no. of hits by shot size Size class
Small Medium Large
Sloop 0.5 0.333 0.25 Small
Cutter 0.5 0.333 0.25 Small
Dhow 0.5 0.333 0.25 Small
Fanchuan 0.5 0.333 0.25 Small
Longship 0.5 0.333 0.25 Medium
Baghlah 1 0.667 0.5 Medium
Merchant brig 1 0.667 0.5 Medium
Junk 1.5 1 0.75 Medium
War brig 2 1.333 1 Medium
Merchant galleon 2.5 1.667 1.25 Large
Xebec 2.5 1.667 1.25 Large
War frigate 3 2 1.5 Large
Grand frigate 4 2.667 2 Grand

Note that, if two ships are facing each other and both move, the results will be different depending on the size classes of the ships. If the ships are in the same size class, they will move into each other simultaneously, and deal a single collision's worth of damage to each ship. However, if they are in different size classes, two collisions worth of damage are dealt to each ship. A way to explain this is that the larger class sizes move "before" smaller class sizes within a single phase of ship movement. For further details, and more complex collisions, and those involving winds and whirlpools, see the article on Collision mechanics.

When a ship hits the edge of the map or rocks, it takes the amount of damage shown in the table below. For example, if a grand frigate hits rocks it receives the equivalent of 1.5 large cannonballs worth of damage. The numbers correspond to exactly 3 swordfighting ("SF") blocks worth of damage to the ship, or one twelfth full SF damage.

Rock damage

Ship Name Equivalent no. of hits by shot size
Small Medium Large
Sloop 0.5 0.333 0.25
Cutter 0.625 0.417 0.3125
Dhow 0.625 0.417 0.3125
Fanchuan 0.65625 0.4375 0.328125
Longship 0.75 0.5 0.375
Baghlah 1 0.667 0.5
Merchant brig 1 0.667 0.5
Junk 1.25 0.833 0.625
War brig 1.25 0.833 0.625
Merchant galleon 1.5 1 0.75
Xebec 1.75 1.167 0.875
War frigate 2.5 1.667 1.25
Grand frigate 3 2 1.5

Historical notes

Prior to release 2004-04-28, the edges of the board acted like winds that pushed ships back onto the board.

See also