Hello Jukka,

(Note* I didn't misspell your name this time...) The comparison between the Fleet boat Submarine (Balao Class) and the U-Boat (Type VIIC) comes out like this

Length 311 ft. 9 in. for the Balao
Length 220.1 ft in length for the VIIC

Beam 27ft 4 in. for the Balao
Beam 20.34 ft for the VIIC

Surface speed 20.5 Knots for the Balao --- a little faster
Surface speed 17.2 knots for the VIIC

Submerged speed 10 Knots for the Balao --- a little faster
Submerged speed 7.6 Knots for the VIIC

Range 11,000 miles at 10 Knots for the Balao --- greater range
Range 7,480 miles at 12 Knots for the VIIC

Maximum depth 200 to 400 ft for the Balao
Maximum depth 100 to 250M (820 ft) for the VIIC --- twice the depth

Crash dive time 60 seconds for the Balao
Crash dive time 30 - 35 seconds for the VIIC --- twice as fast

To me: it looks like the Type VIIC U-Boat was designed to be a fighting machine with the best possible performance at that time. It is very difficult to compare apples and oranges. However, in 1939, the Type VIIC would give the German crew a better chance for survival in the Atlantic U-Boat war. I really have my doubts if the machines were swapped that the Germans would have the degree of success that they enjoyed. They came very close to defeating the British on that front.

This is only my humble opinion...

Regards,
Don_

"A man's got to know his limitations..."
Harry Callahan, SFPD