WesWorld

After news of the RSAN's attack on the Brazillian navy at Rio de Janerio reached Germany, plans were put in place to try to make a similar attack on German harbors more difficult. This vessel is one of the counter-tactics: a floating AA battery to be deployed on the seaward approaches to the harbor. From there it could attempt to detect and engage any approaching threat aircraft, using it's radar and searchlights to spot the threat. Additionally, it can serve a similar purpose against any small torpedo craft, making use of it's shallow-draft design to limit the threat such craft pose to it.

FB-1, German Floating AA battery laid down 1935

Displacement:
473 t light; 525 t standard; 530 t normal; 533 t full load

Dimensions: Length overall / water x beam x draught
169.96 ft / 164.04 ft x 32.81 ft x 5.74 ft (normal load)
51.80 m / 50.00 m x 10.00 m x 1.75 m

Armament:
4 - 4.13" / 105 mm guns (2x2 guns), 35.32lbs / 16.02kg shells, 1928 Model
Dual purpose guns in deck mounts
on centreline ends, evenly spread
4 - 1.46" / 37.0 mm guns (2x2 guns), 1.55lbs / 0.70kg shells, 1929 Model
Anti-aircraft guns in deck mounts
on centreline ends, evenly spread, all raised mounts - superfiring
24 - 0.79" / 20.0 mm guns (6x4 guns), 0.24lbs / 0.11kg shells, 1935 Model
Machine guns in deck mounts
on side, evenly spread, 4 raised mounts
Weight of broadside 153 lbs / 70 kg
Shells per gun, main battery: 450

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 1.97" / 50 mm 164.04 ft / 50.00 m 7.51 ft / 2.29 m
Ends: Unarmoured
Main Belt covers 154 % of normal length

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 1.18" / 30 mm 0.79" / 20 mm -
2nd: 0.79" / 20 mm 0.39" / 10 mm -
3rd: 0.39" / 10 mm - -

- Armour deck: 1.18" / 30 mm, Conning tower: 1.97" / 50 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 543 shp / 405 Kw = 12.00 kts
Range 1,000nm at 5.00 kts
Bunker at max displacement = 8 tons

Complement:
54 - 71

Cost:
£0.177 million / $0.709 million

Distribution of weights at normal displacement:
Armament: 19 tons, 3.6 %
Armour: 191 tons, 36.0 %
- Belts: 90 tons, 16.9 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 12 tons, 2.3 %
- Armour Deck: 86 tons, 16.2 %
- Conning Tower: 3 tons, 0.5 %
Machinery: 15 tons, 2.9 %
Hull, fittings & equipment: 208 tons, 39.3 %
Fuel, ammunition & stores: 56 tons, 10.6 %
Miscellaneous weights: 40 tons, 7.6 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,725 lbs / 782 Kg = 48.8 x 4.1 " / 105 mm shells or 1.2 torpedoes
Stability (Unstable if below 1.00): 1.37
Metacentric height 1.6 ft / 0.5 m
Roll period: 10.8 seconds
Steadiness - As gun platform (Average = 50 %): 94 %
- Recoil effect (Restricted arc if above 1.00): 0.16
Seaboat quality (Average = 1.00): 1.88

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.600
Length to Beam Ratio: 5.00 : 1
'Natural speed' for length: 12.81 kts
Power going to wave formation at top speed: 45 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 15.00 degrees
Stern overhang: 3.28 ft / 1.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 9.84 ft / 3.00 m
- Forecastle (20 %): 9.02 ft / 2.75 m
- Mid (50 %): 9.02 ft / 2.75 m
- Quarterdeck (15 %): 9.02 ft / 2.75 m
- Stern: 9.02 ft / 2.75 m
- Average freeboard: 9.09 ft / 2.77 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 52.4 %
- Above water (accommodation/working, high = better): 125.3 %
Waterplane Area: 3,936 Square feet or 366 Square metres
Displacement factor (Displacement / loading): 128 %
Structure weight / hull surface area: 40 lbs/sq ft or 194 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.92
- Longitudinal: 2.72
- Overall: 1.03
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is excellent
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

40 tons for radar

5 tons for additional searchlights

That's actually not a bad idea. I should build some of those too...

It seemed a useful concept, and the threat of fast attack craft has been on the Admiralstab's collective mind for years (it's a major reason behind the VP-11 class gunboats). It's radar can give early warning of a threat even if the threat stays out of reach of it's guns, too.

Yanno, that can also work as a coastal monitor, too.

Well, yeah, it can. 4 105mm FLaK guns doesn't make it particularly powerful in that role, but it could serve if necessary.

I was thinking in the same vein as an Artilleriefahrprom.

A very useful concept, indeed...

Any chance of them being available for export?

Yep, along those lines. Layout's somewhat different, with the 10.5s closer to the bow and stern, overlooked by the twin 3.7s, and the quad 2cm mounts to the sides, but similar.

Quoted

Originally posted by Swamphen
A very useful concept, indeed...

Any chance of them being available for export?

The only issue preventing their export would be the radar sets. Everything else is easily exported, either by direct sale or license production.

The concept might be interesting but your solution could proof a failure because the hull is way too small. To be successful in its role you need a stable gun platform - otherwise you´ll never get a chance to hit any aircraft. Inside a protected water way or harbor where wave breakers are installed it might not be an issue but in a harbor entrance or if moored outside a mole you will be in trouble - even in the Baltic.

So - nice idea for a lesson learned but in detail your design is lacking, me thinks.

Why a 1935er design?

So how large do you think it should be, since we're not concerning ourselves here with the SS results? Keep in mind that what I'm looking for is, essentially, a slow radar picket ship, so it has to be smaller than the DDs the US used for the role late in WWII (because it doesn't need the speed or the range of those vessels). Now, as Brock has already noted, it's currently a bit bigger than the historical Artilleriefahrprom, but I'm not averse to growing it a bit more.

I'm afraid I'm also a bit confused here. When it comes to SAE river monitors, we are only concerned about what's possible in Springsharp; when it comes to German AA barges... the design is lacking? Sure, in a Force 10 gale it'll be wallowing about the ocean like a cow drunk on paint fumes, but is an 8,000-ton cruiser going to be any more stable?

Looks good but do you really want to spend the tonnage on these now? Might be better to wait until wartime.
I'm too concerned with seaworthiness, they won't stray that far and in a storm any small boat will be "wallowing about the ocean like a cow drunk on paint fumes" to use Brock's rather apt if wierd statement.

The British AA conversions of merchant ships proved too expensive and this is a better way but an even cheaper way is get some old barges and put 20mm and 37mm in them. Sibel Ferries were good for this sort of thing too.

Quoted

Originally posted by Hood
Looks good but do you really want to spend the tonnage on these now? Might be better to wait until wartime.
I'm too concerned with seaworthiness, they won't stray that far and in a storm any small boat will be "wallowing about the ocean like a cow drunk on paint fumes" to use Brock's rather apt if wierd statement.

The British AA conversions of merchant ships proved too expensive and this is a better way but an even cheaper way is get some old barges and put 20mm and 37mm in them. Sibel Ferries were good for this sort of thing too.

Pretty soon Germany is going to have plenty of funds to buy things like this, even with expanding the cruiser and destroyer forces and adding a couple more carriers. So the funds don't worry me too much. The idea is to get radar coverage out further away from the coasts so some smart person doesn't try to sneak torpedo bombers or such like things in under the radar, I don't know that an old barge will work well for that and being able to engage from a bit further away than the 37mm is capable of is also no bad thing (particularly against MTBs, another possible threat).

Perhaps build that radar set on a trawler-style hull instead of a barge hull?

For AA defence why not do like the British and build some coastal sea forts?

That's a possibility as well, the Maunsell Army Forts are a possible base design to be take from.

I'm curious who Germany think is going to be attacking them from out to sea considering she's allied with everyone that way.

I don't really see the point in this ship either. Its very small with very limited capability to do anything at all. The radar is going to have to be fairly low mounted and will be moving massively on such a small ship.

It would be much better to put a bunch of radars on the Friesian islands, Helgoland and other coastal islands. It'll be much cheaper, give better results and be less vulnerable to weather. The AA capability of the vessel is negligible so realistically you're looking at increasing the amount of warning by a few minutes. The correct response to such a problem is to build a better radar (like CHL).

CHL... Canadian Hockey League?!?

Quoted

Originally posted by Rooijen10
CHL... Canadian Hockey League?!?

Proper hockey is played on grass, or actually astroturf nowadays.