WesWorld

Taking Swamphen's comment about the Orcas' role as auxiliary seaplane tenders, I tried my hand at a rough-and-ready Springsharp for such an exercise. The result is appended. They look impressive but I am in no way convinced that they would be good money for value to the Philippine Navy.

Thoughts? Comments? Offers?

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Orca, Philippine Auxiliary Seaplane Tender laid down 1929, Refitted 1944

Displacement: 20,557 t light; 21,050 t standard; 22,346 t normal; 23,383 t full load

Dimensions: Length overall / water x beam x draught

535.01 ft / 535.01 ft x 75.00 ft x 29.99 ft (normal load) [163.07 m / 163.07 m x 22.86 m x 9.14 m]

Armament:

4 - 4.53" / 115 mm guns (2x2 guns), 46.40lbs / 21.05kg shells, 1944 Model Dual purpose guns in deck mounts on centreline ends, evenly spread
8 - 1.38" / 35.0 mm guns (4x2 guns), 1.31lbs / 0.59kg shells, 1944 Model Anti-aircraft guns in deck mounts on side, all amidships
Weight of broadside 196 lbs / 89 kg
Shells per gun, main battery: 400

Armour:

Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.98" / 25 mm 0.98" / 25 mm -
2nd: 0.59" / 15 mm 0.59" / 15 mm -

Conning tower: 3.15" / 80 mm

Machinery:

Oil fired boilers, steam turbines, Geared drive, 2 shafts, 26,890 shp / 20,060 Kw = 20.43 kts
Range 15,000nm at 10.00 kts
Bunker at max displacement = 2,333 tons

Complement: 913 - 1,187

Cost: £3.423 million / $13.691 million

Distribution of weights at normal displacement:

Armament: 25 tons, 0.1 %
Armour: 69 tons, 0.3 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 16 tons, 0.1 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 54 tons, 0.2 %
Machinery: 826 tons, 3.7 %
Hull, fittings & equipment: 13,938 tons, 62.4 %
Fuel, ammunition & stores: 1,789 tons, 8.0 %
Miscellaneous weights: 5,700 tons, 25.5 %

Overall survivability and seakeeping ability:

Survivability (Non-critical penetrating hits needed to sink ship): 47,609 lbs / 21,595 Kg = 1,026.0 x 4.5 " / 115 mm shells or 5.6 torpedoes
Stability (Unstable if below 1.00): 1.10
Metacentric height 3.9 ft / 1.2 m
Roll period: 16.0 seconds
Steadiness - As gun platform (Average = 50 %): 41 %
- Recoil effect (Restricted arc if above 1.00): 0.01
Seaboat quality (Average = 1.00): 1.48

Hull form characteristics:

Hull has raised forecastle, raised quarterdeck
Block coefficient: 0.650
Length to Beam Ratio: 7.13: 1
'Natural speed' for length: 23.13 kts
Power going to wave formation at top speed: 45 %
Trim (Max stability = 0, Max steadiness = 100): 23
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 31.99 ft / 9.75 m
- Forecastle (20 %): 25.98 ft / 7.92 m (18.01 ft / 5.49 m aft of break)
- Mid (50 %): 18.01 ft / 5.49 m
- Quarterdeck (15 %): 25.98 ft / 7.92 m (18.01 ft / 5.49 m before break)
- Stern: 25.98 ft / 7.92 m
- Average freeboard: 21.28 ft / 6.49 m

Ship space, strength and comments:

Space - Hull below water (magazines/engines, low = better): 42.0 %
- Above water (accommodation/working, high = better): 115.5 %
Waterplane Area: 30,738 Square feet or 2,856 Square metres
Displacement factor (Displacement / loading): 293 %
Structure weight / hull surface area: 292 lbs/sq ft or 1,426 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 2.87
- Longitudinal: 4.87
- Overall: 3.03
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is adequate
Good seaboat, rides out heavy weather easily

Breakdown of Miscellaneous Weight

Two 56-foot catapults aft, port and starboard - 400 tons
Aircraft handling cranes - aft - 200 tons
Twelve float reconnaissance aircraft @25 per - 300 tons
Provision for hangarage above deck - 300 tons
Provision for aviation workshops below deck - 500 tons
Provision for accommodation for flight and maintenance personnel - 500 @2 per - 1,000 tons
Provision for munitions and dry store stowage - 1,000 tons
Provision for aviation fuel storage - 2,000 tons

Cost of conversion - 5,140 tons
Time to convert - 218 days

I don't think its cost effective if the Philippines has no real need. It's interesting these ships are bigger than the AV ships Hoo proposes to convert into CVEs. These ships could be rebuilt into carriers but as you've pointed out before these ships are getting long in the tooth.

12 aircraft doesn't seem much on a hull this size and I don't feel the results are worth it. The masses of excess hull strength is worrying, your not using the ship to capacity but the airgroup is probably maxed out and there's little point adding more stuff just to fill this ship. It's too big and slow. I'd be interested to see a comparison with that airgroup and armament on a new hull. Even as destroyer or submarine tenders these ships would be problematic and would need much work but might be more useful in the longer term.

Precisely.

I think that the concept behind them was flawed from the outset. I could tweek the design but then the Philippines has no need for such vessels, and I believe that any other buyer would find them poor value for money; but I could be wrong.