WesWorld

I have been told that small surface combattants do not sim that well in Springsharp. I have tried my hand at several, and the one appended below does not seem that bad. That said, it does have some shortcomings.

Anyone have suggestions for improvement or reducing/eliminating the reported shortcomings?

Thanks,

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Project 1941A, TBD Coastal AS Escort laid down 1941

Displacement: 201 t light; 209 t standard; 233 t normal; 253 t full load

Dimensions: Length overall / water x beam x draught
160.83 ft / 144.36 ft x 17.88 ft x 6.33 ft (normal load)
49.02 m / 44.00 m x 5.45 m x 1.93 m

Armament:

1 - 3.46" / 88.0 mm guns in single mounts, 20.79lbs / 9.43kg shells, 1936 Model Anti-aircraft gun in deck mount on centreline forward, 1 raised gun
3 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1928 Model Anti-aircraft guns in deck mounts on centreline, evenly spread, all raised mounts
Weight of broadside 22 lbs / 10 kg
Shells per gun, main battery: 200

Machinery:

Diesel Internal combustion motors,
Geared drive, 3 shafts, 3,584 shp / 2,674 Kw = 22.00 kts
Range 2,000nm at 14.00 kts
Bunker at max displacement = 45 tons

Complement: 29 - 38

Cost: £0.140 million / $0.558 million

Distribution of weights at normal displacement:

Armament: 3 tons, 1.2 %
Machinery: 95 tons, 40.6 %
Hull, fittings & equipment: 94 tons, 40.3 %
Fuel, ammunition & stores: 32 tons, 13.8 %
Miscellaneous weights: 10 tons, 4.3 %

Overall survivability and seakeeping ability:

Survivability (Non-critical penetrating hits needed to sink ship): 149 lbs / 68 Kg = 7.2 x 3.5 " / 88 mm shells or 0.2 torpedoes
Stability (Unstable if below 1.00): 1.05
Metacentric height 0.4 ft / 0.1 m
Roll period: 11.6 seconds
Steadiness - As gun platform (Average = 50 %): 63 %
- Recoil effect (Restricted arc if above 1.00): 0.24
Seaboat quality (Average = 1.00): 0.96

Hull form characteristics:

Hull has raised forecastle, rise forward of midbreak
Block coefficient: 0.500
Length to Beam Ratio: 8.07 : 1
'Natural speed' for length: 12.01 kts
Power going to wave formation at top speed: 73 %
Trim (Max stability = 0, Max steadiness = 100): 66
Bow angle (Positive = bow angles forward): 30.00 degrees
Stern overhang: 9.84 ft / 3.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 11.48 ft / 3.50 m
- Forecastle (20 %): 10.17 ft / 3.10 m (9.84 ft / 3.00 m aft of break)
- Mid (50 %): 9.19 ft / 2.80 m (8.86 ft / 2.70 m aft of break)
- Quarterdeck (15 %): 8.20 ft / 2.50 m
- Stern: 8.20 ft / 2.50 m
- Average freeboard: 9.21 ft / 2.81 m

Ship tends to be wet forward

Ship space, strength and comments:

Space - Hull below water (magazines/engines, low = better): 145.1 %
- Above water (accommodation/working, high = better): 101.5 %
Waterplane Area: 1,720 Square feet or 160 Square metres
Displacement factor (Displacement / loading): 106 %
Structure weight / hull surface area: 24 lbs/sq ft or 119 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.72
- Longitudinal: 6.87
- Overall: 0.91
Caution: Hull subject to strain in open-sea
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is adequate
Poor seaboat, wet and uncomfortable, reduced performance in heavy weather

10 miscellaneous weight reserved for A/S armament.

Generally, small surface combatants sim worse with fast vessels like MTBs, because SS uses a displacement hull format and not a planning hull format.....that having been said, it generally is easier to choose a historic design from the time period and slightly modify it, according to your wishes and needs.

The problem is small, fast ships. This being a modest 22kts design is ok. It looks pretty fair but the speed is low. Might be useful in the nooks and crannys of the Adriatic though.

Quoted

Originally posted by TexanCowboy
Generally, small surface combatants sim worse with fast vessels like MTBs, because SS uses a displacement hull format and not a planning hull format.....that having been said, it generally is easier to choose a historic design from the time period and slightly modify it, according to your wishes and needs.

More precisely, it uses a power prediction methodology that is only valid at quite low Froude numbers (speed/length ratios). I'm not sure exactly which one, but most of them actually aren't strictly valid for cruisers, never mind MTBs. If SpringSharp 3 ever gets to that point, it'll use the Holtrop-Mennen algorithm which is fiendishly complicated to do without a computer (there are about twenty complex formulae using obscure bits of information, which can fortunately be approximated using other complex formulae) but can handle almost any sane displacement hull. I wrote a really good powering spreadsheet using it last summer, but wasn't able to get a copy when I left that job, more's the pity.

Planing hulls are actually relatively simple to calculate resistance for, at least in comparison to displacement hulls. They only have about three parameters to vary, whereas displacement hulls are amongst the most complex curvilinear shapes found outside a mathematics classroom. I may have the formulae for that somewhere.

My real-world model for this craft was the Soviet Project 122a subchaser of circa 1940. The OTL vessels had a speed of 24 knots.

With some suggestions from Brock I've overcome the strength issue and come up with a somewhat better balanced design. I could see this working in a littoral environment - the Aegean or the Baltic comes to mind.

********
Project 1941B, TBD Coastal AS Escort laid down 1941

Displacement: 189 t light; 197 t standard; 233 t normal; 263 t full load

Dimensions: Length overall / water x beam x draught
160.83 ft / 144.36 ft x 17.88 ft x 6.33 ft (normal load)
49.02 m / 44.00 m x 5.45 m x 1.93 m

Armament:

1 - 3.46" / 88.0 mm guns in single mounts, 20.79lbs / 9.43kg shells, 1936 Model Anti-aircraft gun in deck mount on centreline forward, 1 raised gun
3 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1928 Model Anti-aircraft guns in deck mounts on centreline, evenly spread, all raised mounts
Weight of broadside 22 lbs / 10 kg
Shells per gun, main battery: 200

Machinery:

Diesel Internal combustion motors,
Geared drive, 3 shafts, 2,364 shp / 1,764 Kw = 20.00 kts
Range 3,000nm at 14.00 kts
Bunker at max displacement = 66 tons

Complement: 29 - 38

Cost: £0.109 million / $0.436 million

Distribution of weights at normal displacement:

Armament: 3 tons, 1.2 %
Machinery: 62 tons, 26.8 %
Hull, fittings & equipment: 114 tons, 49.0 %
Fuel, ammunition & stores: 44 tons, 18.8 %
Miscellaneous weights: 10 tons, 4.3 %

Overall survivability and seakeeping ability:

Survivability (Non-critical penetrating hits needed to sink ship): 331 lbs / 150 Kg = 15.9 x 3.5 " / 88 mm shells or 0.3 torpedoes
Stability (Unstable if below 1.00): 1.00
Metacentric height 0.4 ft / 0.1 m
Roll period: 12.2 seconds
Steadiness
- As gun platform (Average = 50 %): 75 %
- Recoil effect (Restricted arc if above 1.00): 0.27
Seaboat quality (Average = 1.00): 1.24

Hull form characteristics:

Hull has raised forecastle, rise forward of midbreak
Block coefficient: 0.500
Length to Beam Ratio: 8.07 : 1
'Natural speed' for length: 12.01 kts
Power going to wave formation at top speed: 69 %
Trim (Max stability = 0, Max steadiness = 100): 61
Bow angle (Positive = bow angles forward): 30.00 degrees
Stern overhang: 9.84 ft / 3.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 11.48 ft / 3.50 m
- Forecastle (20 %): 10.17 ft / 3.10 m (9.84 ft / 3.00 m aft of break)
- Mid (50 %): 9.19 ft / 2.80 m (8.86 ft / 2.70 m aft of break)
- Quarterdeck (15 %): 8.20 ft / 2.50 m
- Stern: 8.20 ft / 2.50 m
- Average freeboard: 9.21 ft / 2.81 m

Ship tends to be wet forward

Ship space, strength and comments:

Space - Hull below water (magazines/engines, low = better): 101.1 %
- Above water (accommodation/working, high = better): 101.5 %
Waterplane Area: 1,720 Square feet or 160 Square metres
Displacement factor (Displacement / loading): 149 %
Structure weight / hull surface area: 30 lbs/sq ft or 144 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.92
- Longitudinal: 8.39
- Overall: 1.15
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is adequate
Ship has slow, easy roll, a good, steady gun platform
Good seaboat, rides out heavy weather easily

10 tons of miscellaneous weight reserved for A/S outfit – depth charges, K-guns etc.