Upgrades, what is realistic.

[Lzs von swe]

Hi all.
If you start a campaign, start year and flotilla of your choice, then you chose your boat and fit it with the available upgrades you can afford, what is most realistic.
Keep the boat `as is´ and only fit things like radar etc. but not new engines or batteries, then after say two years upgrade to a new boat with all available new technology you can afford and repeat the above. Or always upgrade everything as son as its possible.
How was this done during the war? How much of the new tech was fitted to the old boats. A turbo or compressor, did they bolt that to old engines? New batteries, did they change batteries or was the boat written of when they where worn out?
Sonar coating, I guess they had to fit that to all boats, conning towers, how common was it to rebuild the boats with new ones? Etc.:hmm:

Many of you guys seem to have a lot of knowledge about these boats so I´m sure you can enlight me, and others, on this.