Armor (also called 'hulls') and weapons are currently the only equipment in game. Equipment can be gained from voyages, crafting or defeating high level pirates and can be placed on any of your ships in their equipment slots.
(see picture -->).
Since iOS Version 4.2, all ships have three equipment slots. This has not yet been implemented on Android where the number of slots still varies from ship to ship.
Strategies for using Equipment
We all know that PG has the game set to charge a full repair cost for any damage received while in battle.
Obviously, you are going to try and "one-shot" any pirate. In order to do that, as far as I can tell to date, if you have around a 4.5:1 ratio between your cannon and the pirates hull+armour AND you get in a great shot, you will kill the pirate with a single shot.
So, the corollary to this is to power up your best ship with the best cannon you can find, win or manufacture.
And, if you are wanting to "one-shot" your opponent, what then is the use of Armour (Hulls)?
Its actually the complete reverse of the above!
If you can't "one-shot" your opponent, then equip lower level ships with the best armour you have and send them out to chip away at the pirate!