I searched the forums but could not find an "official" answer to this question: Can multiple ship upgrades be purchased in one game week, one per hero training in the shipyard?

Page 31 of the rulebook under, "The Shipyard" heading in the second column states:

" A hero who visits a shipyard while his party is training in a city may purchase one Ship Upgrade or cannon."

Okay, what about a week in which one member of the party trains and the three remaining members purchase ship upgrades. Can they each purchase an upgrade?

Is there a consensus on this question?

Yes. Multiple heroes in the same location can each use that location (though in the case of the Shop and the Alchemist there's no reason to).

i am not sure that it is possible to upgrade multiple times even with multiple heros due to the fact that every hero pays the xp cost of each upgrade and that makes it a party action, much like upgrading tamalir in RTL.

The only things upgrading the ship and upgrading Tamalir have in common are the things the rules specify. Tamalir specifies a limit and even has different timing rules for the upgrades. SoB != RtL.

just re-read the rules on it, and you are right, i can not find anything that implies only one upgrade per week for the party, just one per hero. i see no reason why the entire party can not purchase an upgrade each as long as they have the XP for all of them.