Siebengebirge class Crane Ship
A mercantile conversion based upon the hull of
Sagaland class cargo vessels
Siebengebirge, German Crane Ship laid down 1947
Displacement: 7,195 t light; 7,485 t standard; 14,493 t normal; 20,099 t full load
Dimensions: Length overall / water x beam x draught
482.11 ft / 473.10 ft x 62.50 ft x 28.22 ft (normal load) [146.95 m / 144.20 m x 19.05 m x 8.60 m]
Armament:
4 - 1.46" / 37.0 mm guns (2x2 guns), 1.55lbs / 0.70kg shells, 1947 Model Anti-aircraft guns in deck mounts on centreline ends, evenly spread, all raised mounts
4 - 0.79" / 20.0 mm guns (2x2 guns), 0.24lbs / 0.11kg shells, 1947 Model Anti-aircraft guns in deck mounts on side, all aft, all raised mounts - superfiring
Weight of broadside 7 lbs / 3 kg
Shells per gun, main battery: 500
Machinery:
Diesel Internal combustion motors, Geared drive, 1 shaft, 6,777 shp / 5,056 Kw = 15.00 kts
Range 90,000nm at 12.00 kts
Bunker at max displacement = 12,614 tons
Complement: 659 - 858
Cost: £2.007 million / $8.029 million
Distribution of weights at normal displacement:
Armament: 1 tons, 0.0 %
Machinery: 167 tons, 1.2 %
Hull, fittings & equipment: 5,826 tons, 40.2 %
Fuel, ammunition & stores: 7,298 tons, 50.4 %
Miscellaneous weights: 1,200 tons, 8.3 %
Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship): 97,826 lbs / 44,373 Kg = 63,296.3 x 1.5 " / 37 mm shells or 17.1 torpedoes
Stability (Unstable if below 1.00): 1.35
Metacentric height 4.2 ft / 1.3 m
Roll period: 12.8 seconds
Steadiness - As gun platform (Average = 50 %): 90 %
- Recoil effect (Restricted arc if above 1.00): 0.00
Seaboat quality (Average = 1.00): 1.80
Hull form characteristics:
Hull has raised forecastle
Block coefficient: 0.608
Length to Beam Ratio: 7.57: 1
'Natural speed' for length: 21.75 kts
Power going to wave formation at top speed: 31 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 22.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 22.31 ft / 6.80 m
- Forecastle (10 %): 19.69 ft / 6.00 m (18.04 ft / 5.50 m aft of break)
- Mid (30 %): 16.40 ft / 5.00 m
- Quarterdeck (50 %): 16.40 ft / 5.00 m
- Stern: 16.40 ft / 5.00 m
- Average freeboard: 17.00 ft / 5.18 m
Ship tends to be wet forward
Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 14.7 %
- Above water (accommodation/working, high = better): 103.7 %
Waterplane Area: 21,340 Square feet or 1,983 Square metres
Displacement factor (Displacement / loading): 940 %
Structure weight / hull surface area: 167 lbs/sq ft or 816 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 1.88
- Longitudinal: 3.12
- Overall: 1.98
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is adequate
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather
True bunkers 2,212 tons for a radius of 15,000 nm. Additional bunkers simmed as low-stowed cargo, 10,000 tons.
Residual composite strength represents strengthened deck coamings and structure for carriage of heavy cargos.
Breakdown of miscellaneous weight:
Cargo handling gear - 500 tons
Anticipated deck cargo - 600 tons
Radar and other navigational equipment - 100 tons
Cost of conversion (15%) - 1,080 tons
Time for conversion (15%) - 73 days