Libra, Netherlands patrol boat laid down 1938, launched 1939, completed
1939 (engine 1938)
Displacement:
548 t light; 580 t
standard; 838 t normal; 1 045 t full load
Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(219,22 ft / 214,24 ft)
x 31,50 ft x (9,35 / 10,95 ft)
(66,82 m / 65,30 m) x
9,60 m x (2,85 / 3,34 m)
Armament:
2 - 4,13" / 105 mm 46,0
cal guns - 35,27lbs / 16,00kg shells, 250 per gun
Dual purpose guns in deck mounts, 1931 Model
2 x Single mounts on centreline ends, evenly
spread
2 - 1,57" / 40,0 mm
60,0 cal guns - 2,05lbs / 0,93kg shells, 2 000 per gun
Anti-air guns in deck mounts, 1932 Model
1 x Twin mounts on sides, aft deck
centre
1 raised
mounts
4 - 0,52" / 13,2 mm
78,0 cal guns - 0,11lbs / 0,05kg shells, 4 000 per gun
Machine guns in deck mounts, 1919 Model
2 x Single mounts on sides, aft deck forward
2 raised
mounts
2 x Single mounts on sides, forward deck
centre
2 double
raised mounts
Weight of broadside 75 lbs /
34 kg
Main DC/AS Mortars
2 - 396,83 lbs / 180,00 kg
Depth Charges + 60 reloads - 10,984 t total
in Stern depth charge
racks
Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist
(max)
Main: 0,51" / 13 mm -
-
Machinery:
Diesel Internal
combustion motors,
Geared drive, 2 shafts,
5 400 shp / 4 028 Kw = 21,45 kts
Range 13 000nm at
12,00 kts
Bunker normal = 258
tons, at max displacement = 465 tons
Complement:
77 - 101
Cost:
£0,247 million / $0,988
million
Distribution of weights at normal displacement:
Armament: 29 tons, 3,5%
- Guns: 16 tons, 1,9%
- Weapons: 14 tons, 1,6%
Armour: 2 tons, 0,3%
- Armament: 2 tons, 0,3%
Machinery: 148 tons,
17,6%
Hull, fittings &
equipment: 318 tons, 37,9%
Fuel, ammunition &
stores: 290 tons, 34,6%
Miscellaneous weights:
50 tons, 6,0%
- Hull below water: 36 tons
- Hull above water: 14 tons
Overall survivability and seakeeping ability:
Survivability
(Non-critical penetrating hits needed to sink ship):
495 lbs / 231 Kg = 14,0 x 4,1 " / 105
mm shells or 0,7 torpedoes
Stability (Unstable if
below 1.00): 1,50
Metacentric height 1,8
ft / 0,5 m
Roll period: 10,0
seconds
Steadiness - As gun platform (Average = 50 %): 70 %
-
Recoil effect (Restricted arc if above 1.00): 0,08
Seaboat quality (Average = 1.00): 1,39
Hull form characteristics:
Hull has rise forward
of midbreak,
a normal bow and large transom stern
Block coefficient
(normal/deep): 0,465 / 0,495
Length to Beam Ratio: 6,80
: 1
'Natural speed' for
length: 17,35 kts
Power going to wave
formation at top speed: 64 %
Trim (Max stability =
0, Max steadiness = 100): 50
Bow angle (Positive =
bow angles forward): 12,50 degrees
Stern overhang: 0,98 ft
/ 0,30 m
Freeboard (% = length
of deck as a percentage of waterline length):
Fore
end, Aft end
- Forecastle: 16,00%, 18,04 ft /
5,50 m, 17,06 ft / 5,20 m
- Forward deck: 28,00%, 17,06 ft / 5,20
m, 17,06 ft / 5,20 m
- Aft deck: ` 36,00%, 8,86 ft / 2,70 m, 8,86 ft / 2,70 m
- Quarter deck: 20,00%, 8,86 ft / 2,70
m, 8,86 ft / 2,70 m
- Average freeboard: 12,53 ft / 3,82 m
Ship space, strength and comments:
Space - Hull below water (magazines/engines, low =
better): 70,6%
- Above
water (accommodation/working, high = better): 139,4%
Waterplane Area:
4 529 Square feet or 421 Square metres
Displacement factor
(Displacement / loading): 217%
Structure weight / hull
surface area: 42 lbs/sq ft or 206 Kg/sq metre
Hull strength
(Relative):
-
Cross-sectional: 0,87
-
Longitudinal: 4,29
- Overall:
1,02
Excellent machinery,
storage, compartmentation space
Excellent accommodation
and workspace room
Ship has slow, easy
roll, a good, steady gun platform
Good seaboat, rides out
heavy weather easily
Libra (1939)
Lyra (1939)
Cygnus (1939)
Cetus (1939)