If a party is taking a training action for the week at a city with a shipyard, can each player that goes to the shipyard that week buy a ship upgrade? Or are they restricted to 1 ship upgrade per week. The rules seem to allow multiple upgrades, as long each player is in the shipyard for the week. Otherwise to buy 3 canons would take 3 weeks in the shipyard, and that doesn't seem right.
I know that the ship can be repaired as well.