Hmm... the compass is a prerequisite for the third and fourth level shipyards, it is not needed for the ships themselves. At present it does not have effect as the ships that require the third level shipyard are high/late era only anyway. If we wanted to tie shipbuilding to the compass and gunpowder events only then we would have to remove the era restrictions currently in place and use the events to determine when ships become available. e.g:

Dhow: From Early (Muslim/GH)
Baggala: Compass (Muslim/GH)
Boom: Gunpowder (Muslim/GH)

Longboat: From early (Danes only)
Barque: From early (Catholic/Orthodox - excluding Danes, Byzantine, Italians and Sicilians)
Caravel: Compass (Catholic/Orthodox - excluding Byzantine, Italians and Sicilians)
Cog: Gunpowder (Catholic/Orthodox - excluding Byzantine, Italians and Sicilians)
Carrack: Gunpowder (Catholic/Orthodox - excluding Byzantine, Italians and Sicilians)

Dromon: From early (Byzantine, Italians and Sicilians)
Galley: From early (Byzantine, Italians and Sicilians)
Firegally: Compass (Byzantine, Italians and Sicilians)
Wargalley: Compass (Byzantine, Italians and Sicilians)
Gungalley: Gunpowder (Byzantine, Italians and Sicilians)