I was struggling to get a destroyer over a composite strength of 0.57, that I didn't need to change

I entered my design for the Ger/DD/1915 destroyer into Springsharp, and had problems. When I entered the data exactly as I had specified it in the early 1970's, it worked just that was. This was a small destroyer with 2-4in guns and 4-21in TT, with 30 mines. The speed was just 32 knots. Springsharp says: "Design well balanced for a light fast combatant".

Ger/DD/1915, Germany Destroyer laid down 1915

Displacement:
	796 t light; 819 t standard; 850 t normal; 875 t full load

Dimensions: Length overall / water x beam x draught
	262.77 ft / 260.00 ft x 26.00 ft x 10.00 ft (normal load)
	80.09 m / 79.25 m x 7.92 m  x 3.05 m

Armament:
      2 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1915 Model
	  Quick firing guns in deck mounts 
	  on centreline ends, evenly spread, all raised mounts
	Weight of broadside 64 lbs / 29 kg
	Shells per gun, main battery: 150
	4 - 21.0" / 533.4 mm above water torpedoes

Machinery:
	Oil fired boilers, steam turbines, 
	Geared drive, 2 shafts, 26,816 shp / 20,004 Kw = 32.00 kts
	Range 1,200nm at 12.00 kts
	Bunker at max displacement = 57 tons

Complement:
	78 - 102

Cost:
	£0.147 million / $0.588 million

Distribution of weights at normal displacement:
	Armament: 8 tons, 0.9 %
	Machinery: 475 tons, 55.8 %
	Hull, fittings & equipment: 284 tons, 33.4 %
	Fuel, ammunition & stores: 54 tons, 6.3 %
	Miscellaneous weights: 30 tons, 3.5 %

Overall survivability and seakeeping ability:
	Survivability (Non-critical penetrating hits needed to sink ship):
	  217 lbs / 99 Kg = 6.8 x 4.0 " / 102 mm shells or 0.2 torpedoes
	Stability (Unstable if below 1.00): 1.21
	Metacentric height 0.9 ft / 0.3 m
	Roll period: 11.2 seconds
	Steadiness	- As gun platform (Average = 50 %): 57 %
			- Recoil effect (Restricted arc if above 1.00): 0.19
	Seaboat quality  (Average = 1.00): 1.15

Hull form characteristics:
	Hull has rise forward of midbreak
	Block coefficient: 0.440
	Length to Beam Ratio: 10.00 : 1
	'Natural speed' for length: 16.12 kts
	Power going to wave formation at top speed: 73 %
	Trim (Max stability = 0, Max steadiness = 100): 50
	Bow angle (Positive = bow angles forward): 2.00 degrees
	Stern overhang: 2.00 ft / 0.61 m
	Freeboard (% = measuring location as a percentage of overall length):
	   - Stem:		22.00 ft / 6.71 m
	   - Forecastle (21 %):	21.00 ft / 6.40 m
	   - Mid (30 %):		21.00 ft / 6.40 m (13.00 ft / 3.96 m aft of break)
	   - Quarterdeck (15 %):	12.00 ft / 3.66 m
	   - Stern:		12.00 ft / 3.66 m
	   - Average freeboard:	15.06 ft / 4.59 m

Ship space, strength and comments:
	Space	- Hull below water (magazines/engines, low = better): 191.2 %
		- Above water (accommodation/working, high = better): 84.7 %
	Waterplane Area: 4,278 Square feet or 397 Square metres
	Displacement factor (Displacement / loading): 40 %
	Structure weight / hull surface area: 25 lbs/sq ft or 123 Kg/sq metre
	Hull strength (Relative):
		- Cross-sectional: 0.44
		- Longitudinal: 5.43
		- Overall: 0.57
	Hull space for machinery, storage, compartmentation is cramped
	Room for accommodation and workspaces is cramped