Sub upgrades?

[OmegaMan]

Hello all. Sorry for my english, it's too bad (I'm from Spain)
I have a question: how to upgrade the sub turret? I'm in May '42 and have the same pre-war turret design. Any chance to change this?
Thanks in advance.

[elanaiba]

A new conning tower will be assigned to you at some point, during a refit in base.

[OmegaMan]

Very very thanks for your fast answard. Great.