Coast-Defense Battleship Helgoland – A Forgotten Experiment of the Interwar German Navy

After Germany signed the Treaty of Versailles in 1919, the future of its navy became a matter of constant internal dispute. With the Reichsmarine restricted to building only 10,000-ton replacements for its ageing pre-dreadnoughts, admirals and naval architects debated the shape of Germany’s postwar fleet:
Should it be a cruiser-based force for colonial policing? A flotilla of small coast-defence ships? Or compact but heavily armed “pocket battleships”?

The ultimately chosen solution became the famous Panzerschiffe—but before the Deutschland-class emerged, the Reichsmarine quietly approved a little-known technological testbed meant to verify whether its ambitious new ideas could even work.

Designing an Experimental Warship

In 1925, the navy authorized the construction of a compact coast-defence vessel using every innovation envisioned for the future Panzerschiffe:
• a fully welded hull,
• diesel propulsion,
• and a main battery of 28-cm guns, unprecedented for a ship of such modest displacement.

Internally designated Projekt K-25, the ship later received the name Helgoland.
Work progressed slowly—both because welding such a large hull was still experimental, and because manufacturing lightweight diesel engines of sufficient power posed major engineering challenges.

When the ship finally commissioned in 1929, it emerged as a strange hybrid: heavy cruiser armament, the freeboard of a monitor, and the speed of a training ship. But as an experimental design, this was accepted.

Early Service and Troubles

Trials demonstrated that the new technology worked, but the concept itself was deeply flawed.
Helgoland’s low freeboard made her extremely wet in the rough North Sea. Heavy seas washed over the bow, making long transits exhausting for crews. As a result, by the early 1930s, the ship had effectively become a floating technology demonstrator and training platform.

Still, the lessons she provided directly shaped the more successful Deutschland-class:
• improved welding techniques,
• refined diesel mountings,
• and more efficient internal layouts.

Though not glamorous, the Helgoland was an essential stepping stone.

Wartime Employment

When World War II broke out in 1939, the Helgoland was already outdated. She served on coastal patrol duty around Wilhelmshaven, where her heavy guns proved surprisingly useful. During several raids by British bombers in 1940, she shot down two attackers and sustained only light damage.

During Operation Weserübung, the invasion of Norway, Helgoland was too slow for the initial assaults but was dispatched later that year to reinforce German coastal forces. She rotated through several fjord bases—Bergen, Åndalsnes, Molde, Trondheim, Ålesund, and Stavanger—where her heavy guns provided coastal defense and artillery support.

Her low speed and limited seaworthiness kept her patrolling fjords rather than open waters, but in this environment she proved serviceable.

Final Years and Fate

In late 1942, the ship returned to the Baltic Sea to resume her peacetime role as a training ship. However, as the Eastern Front collapsed in 1944, even Helgoland’s old guns were pressed back into combat. She provided fire support to German forces trapped in the Kurland Pocket, firing thousands of shells until the worn-out barrels became unsafe to use.

In early 1945, she participated in the desperate evacuation of refugees and military personnel from East Prussia and Latvia to Denmark. During these hazardous voyages she survived two Soviet submarine attacks—more by luck than design.

With Germany collapsing, the ageing experimental ship had no further value. Helgoland was scuttled in the Heikendorf Bight in May 1945, later salvaged and finally scrapped in 1950.

The model shows the "Helgoland" in the Baltic Sea in June 1944.

Technical Data (created with SpringSharp)

Helgoland, Germany Coast Defence Ship laid down 1925

Displacement:
    4.723 t light; 5.243 t standard; 6.009 t normal; 6.622 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
    (357,61 ft / 347,77 ft) x 59,06 ft x (16,08 / 17,46 ft)
    (109,00 m / 106,00 m) x 18,00 m  x (4,90 / 5,32 m)

Armament:
    6 - 11,02" / 280 mm 52,0 cal guns - 715,22lbs / 324,42kg shells, 150 per gun
      Breech loading guns in turret on barbette mounts, 1925 Model
      2 x Triple mounts on centreline ends, evenly spread
    4 - 5,91" / 150 mm 55,0 cal guns - 111,15lbs / 50,42kg shells, 150 per gun
      Breech loading guns in deck and hoist mounts, 1925 Model
      4 x Single mounts on side ends, evenly spread
        4 raised mounts
    4 - 1,46" / 37,0 mm 83,0 cal guns - 1,77lbs / 0,80kg shells, 800 per gun
      Anti-air guns in deck mounts, 1925 Model
      4 x Single mounts on sides amidships
        4 raised mounts
    10 - 0,79" / 20,0 mm 65,0 cal guns - 0,27lbs / 0,12kg shells, 1.500 per gun
      Machine guns in deck mounts, 1925 Model
      10 x Single mounts on centreline, evenly spread
        10 raised mounts
      Weight of broadside 4.746 lbs / 2.153 kg

Armour:
   - Belts:        Width (max)    Length (avg)        Height (avg)
    Main:    3,15" / 80 mm    196,85 ft / 60,00 m    13,12 ft / 4,00 m
    Ends:    1,57" / 40 mm    131,23 ft / 40,00 m    6,56 ft / 2,00 m
      19,69 ft / 6,00 m Unarmoured ends
      Main Belt covers 87% of normal length
      Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
        1,77" / 45 mm    196,85 ft / 60,00 m    13,12 ft / 4,00 m

   - Hull Bulges:
        0,39" / 10 mm    196,85 ft / 60,00 m    13,12 ft / 4,00 m

   - Gun armour:    Face (max)    Other gunhouse (avg)    Barbette/hoist (max)
    Main:    5,51" / 140 mm    3,15" / 80 mm        3,15" / 80 mm
    2nd:    0,79" / 20 mm    0,39" / 10 mm              -

   - Armoured deck - single deck: 1,18" / 30 mm For and Aft decks
    Forecastle: 0,71" / 18 mm  Quarter deck: 0,71" / 18 mm

   - Conning towers: Forward 5,91" / 150 mm,  Aft 0,00" / 0 mm

Machinery:
    Diesel Internal combustion motors,
    Direct drive, 2 shafts, 6.987 shp / 5.212 Kw = 17,00 kts
    Range 8.500nm at 14,00 kts
    Bunker at max displacement = 1.379 tons

Complement:
    340 - 443

Cost:
    £2,333 million / $9,334 million

Distribution of weights at normal displacement:
    Armament: 1.050 tons, 17,5%
    Armour: 1.260 tons, 21,0%
       - Belts: 424 tons, 7,1%
       - Torpedo bulkhead: 169 tons, 2,8%
       - Bulges: 38 tons, 0,6%
       - Armament: 270 tons, 4,5%
       - Armour Deck: 317 tons, 5,3%
       - Conning Tower: 42 tons, 0,7%
    Machinery: 227 tons, 3,8%
    Hull, fittings & equipment: 2.185 tons, 36,4%
    Fuel, ammunition & stores: 1.286 tons, 21,4%
    Miscellaneous weights: 0 tons, 0,0%

Overall survivability and seakeeping ability:
    Survivability (Non-critical penetrating hits needed to sink ship):
      7.018 lbs / 3.183 Kg = 10,5 x 11,0 " / 280 mm shells or 1,6 torpedoes
    Stability (Unstable if below 1.00): 1,36
    Metacentric height 3,9 ft / 1,2 m
    Roll period: 12,6 seconds
    Steadiness    - As gun platform (Average = 50 %): 48 %
            - Recoil effect (Restricted arc if above 1.00): 0,96
    Seaboat quality  (Average = 1.00): 1,51

Hull form characteristics:
    Hull has a flush deck,
      a ram bow and a round stern
    Block coefficient (normal/deep): 0,637 / 0,646
    Length to Beam Ratio: 5,89 : 1
    'Natural speed' for length: 18,65 kts
    Power going to wave formation at top speed: 47 %
    Trim (Max stability = 0, Max steadiness = 100): 30
    Bow angle (Positive = bow angles forward): 0,00 degrees
    Stern overhang: 0,00 ft / 0,00 m
    Freeboard (% = length of deck as a percentage of waterline length):
                Fore end,     Aft end
       - Forecastle:    20,00%,  15,75 ft / 4,80 m,  15,75 ft / 4,80 m
       - Forward deck:    40,00%,  15,75 ft / 4,80 m,  15,75 ft / 4,80 m
       - Aft deck:    25,00%,  15,75 ft / 4,80 m,  15,75 ft / 4,80 m
       - Quarter deck:    15,00%,  15,75 ft / 4,80 m,  15,75 ft / 4,80 m
       - Average freeboard:        15,75 ft / 4,80 m
    Ship tends to be wet forward

Ship space, strength and comments:
    Space    - Hull below water (magazines/engines, low = better): 137,4%
        - Above water (accommodation/working, high = better): 137,2%
    Waterplane Area: 15.546 Square feet or 1.444 Square metres
    Displacement factor (Displacement / loading): 91%
    Structure weight / hull surface area: 120 lbs/sq ft or 584 Kg/sq metre
    Hull strength (Relative):
        - Cross-sectional: 0,76
        - Longitudinal: 2,11
        - Overall: 0,84
    Caution: Hull subject to strain in open-sea
    Hull space for machinery, storage, compartmentation is cramped
    Room for accommodation and workspaces is excellent
    Excellent seaboat, comfortable, can fire her guns in the heaviest weather

The model was scratch project with leftover parts of my spare part box. Build in scale 1/400, it stared with the underwater ship of the USS Arizona (scale 1/700). The hull and deck on top were build from plastic sheets while the superstructure, guns, etc are leftovers of an old Heller 1/400 scale Lützow kit, my father had build in 1978. The original ship itself was destroyed many years ago, but some parts did survive which I could reuse now.
The model is airbrushed with Revell Aqua Color and I used additional PE arts plus EZ-Line for the antennas.