[toryu]

I started out J.Steiner's career in 1st Flotilla 1939. My mounts:

U3 - Type IIa. 5 torpedoes, 1 20mm AA gun. I'd average 7kts surfaced, and 2kts submerged during the day.

First chance I got, I upgraded U3 to a type IID. Still with 5 torpedoes & 1 20mm AA gun, but with nearly twice the range, and I could run at the skin-stretching speed of 3kts submerged during the day and still have some battery power left.

I then upgraded to a new sub - U49, a type VIIB. 14 torpedoes, still with a 20mm AA gun, but I could get her up to 15kts and more, depending on the sea. The range is vastly increased also. And I could run at about 4kts submerged during the day, and still have some battery power left. Depending on the length of the day, of course. Up North, you don't get much darkness in summer. A few hours only, just enough to charge the batteries.

Now, I'm sailing in U49, but it's a type VIIC. Cost me 3500 renown. Still with 14 torpedoes, but I upgraded the flak gun to a Zwilling (twin barrels), for a cost of zero renown. How can you not love that? I'm currently on my 9th patrol, and it's summer 1940. I have a feeling I'm going to need the heavier AA guns before long, which is part of the reason I bought the VIIC.

So YES - Upgrade as you go along. Apart from the survivability, it's a blast comparing the different types of Uboats. It gives you a great feeling of progress as you go through your career. Take screenshots of your boats. Print them out. Frame them. They will give you happy memories when you're in 1945 with a Type XXI and no future.