upgrading my boat.

[papegojan]

I am wondering if there is anything I am doing wrong. I am now in sept 1941 and my boat is a VIIC. Nice vessel which has provided sterling service, but according to the list of upgrades possible in th game list, the more updated conning towers should be available by the timeframe I am in. can anyone advise me if I need to sink a certain amount of tonnage, or get a certain amount of renown before these refits are available? Also according to the list the type IX should be aailable now, but it ain't. Is ythis dependent on the flotilla to which you are attached? Before anyone says, I have read the manual, but didn't see anything. Maybe I'm just thick.......