Here are several designs for German S-Boote that never materialized but interesting none the less. All this info including pictures is taken from http://www.german-navy.de/kriegsmarine
Kleinstschnellboot Projekt
Dimensions
Length (Total): 14,2 m
Beam: 3,0 m
Draft: 1,2 m
Weapons
2 cm MG: 5
1,3 cm Machine Guns: 1
86 mm Rocket Launcher: 4
45 cm Torpedo tubes: 2
Depth Charges 10
Engines
Shafts: 3
Engines: 3
Type: Piston engines
Performance
Total Performance: 2100 hp
Speed: 47 kn (loaded); 50 kn (unloaded)
Tragflügelboot Projekt
Length (Total): 15 m
Beam: 3,0 m
Height: 3,1 m
Draft: 0,9 m
Weapons
2 cm MG: 4
1,3 cm Machine Guns: 1
86 mm Rocket Launcher: 5
45 cm Torpedo tubes: 2
Depth Charges 10
Engines
Shafts: 3
Engines: 3
Type: Piston engines
Performance
Total Performance: 2200 hp
Speed: 55 kn
Turbojet Tragflügelboot Projekt
Dimensions
Length (Total): 15 m
Beam: 3,0 m
Height: 3,1 m
Draft: 0,9 m
Weapons
2 cm MG: 4
1,3 cm Machine Guns: 1
86 mm Rocket Launcher: 5
45 cm Torpedo tubes: 2
Depth Charges 10