WesWorld

Here are the two newest designs for my navy and export.

Comments are welcome.

This is small vessel to escort MTBs and MGBs using its rapid-fire 37mm against surface and aerial targets. Q mount can be dismounted and two fixed torpedo tubes added. Engines are two 800hp Spartan aero engines from Atlantis.

Project 610, Argentina Light Support Craft laid down 1932

Displacement:
84 t light; 87 t standard; 92 t normal; 96 t full load

Dimensions: Length overall / water x beam x draught
128.39 ft / 123.03 ft x 17.72 ft x 4.92 ft (normal load)
39.13 m / 37.50 m x 5.40 m x 1.50 m

Armament:
6 - 1.46" / 37.0 mm guns (3x2 guns), 1.55lbs / 0.70kg shells, 1932 Model
Anti-aircraft guns in deck mounts
on centreline, evenly spread, 1 raised mount
Aft Main mounts separated by engine room
4 - 0.31" / 7.9 mm guns (1x4 guns), 0.02lbs / 0.01kg shells, 1932 Model
Machine guns in deck mount
on centreline forward
Weight of broadside 9 lbs / 4 kg
Shells per gun, main battery: 200

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.39" / 10 mm - -

Machinery:
Petrol Internal combustion motors,
Direct drive, 2 shafts, 1,600 shp / 1,193 Kw = 22.45 kts
Range 1,000nm at 12.00 kts
Bunker at max displacement = 8 tons

Complement:
14 - 19

Cost:
£0.043 million / $0.171 million

Distribution of weights at normal displacement:
Armament: 1 tons, 1.3 %
Armour: 1 tons, 0.6 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 1 tons, 0.6 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.0 %
Machinery: 39 tons, 42.4 %
Hull, fittings & equipment: 34 tons, 36.8 %
Fuel, ammunition & stores: 7 tons, 8.1 %
Miscellaneous weights: 10 tons, 10.9 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
48 lbs / 22 Kg = 31.3 x 1.5 " / 37 mm shells or 0.1 torpedoes
Stability (Unstable if below 1.00): 1.20
Metacentric height 0.5 ft / 0.2 m
Roll period: 10.3 seconds
Steadiness - As gun platform (Average = 50 %): 50 %
- Recoil effect (Restricted arc if above 1.00): 0.08
Seaboat quality (Average = 1.00): 0.95

Hull form characteristics:
Hull has a flush deck
and transom stern
Block coefficient: 0.300
Length to Beam Ratio: 6.94 : 1
'Natural speed' for length: 13.57 kts
Power going to wave formation at top speed: 71 %
Trim (Max stability = 0, Max steadiness = 100): 53
Bow angle (Positive = bow angles forward): 25.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 11.48 ft / 3.50 m
- Forecastle (20 %): 8.20 ft / 2.50 m
- Mid (50 %): 7.22 ft / 2.20 m
- Quarterdeck (15 %): 7.22 ft / 2.20 m
- Stern: 6.56 ft / 2.00 m
- Average freeboard: 7.78 ft / 2.37 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 158.9 %
- Above water (accommodation/working, high = better): 147.4 %
Waterplane Area: 1,455 Square feet or 135 Square metres
Displacement factor (Displacement / loading): 80 %
Structure weight / hull surface area: 13 lbs/sq ft or 65 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.44
- Longitudinal: 4.59
- Overall: 0.56
Caution: Hull subject to strain in open-sea
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is excellent
Poor seaboat, wet and uncomfortable, reduced performance in heavy weather


This design is a larger patrol type for customs and the navy to check potential smugglers and offer support in wartime to smaller MTBs. The 75mm gun is the M31 L/50 based on the French 75mm 1898 but with new barrel and new AP shells. Diesels identical to the Chaco Class.

Project 611, Argentina Light Patrol Craft laid down 1933

Displacement:
177 t light; 181 t standard; 192 t normal; 200 t full load

Dimensions: Length overall / water x beam x draught
149.13 ft / 144.36 ft x 21.33 ft x 5.74 ft (normal load)
45.46 m / 44.00 m x 6.50 m x 1.75 m

Armament:
1 - 2.95" / 75.0 mm guns in single mounts, 13.66lbs / 6.20kg shells, 1932 Model
Quick firing gun in deck mount
on centreline forward
2 - 1.46" / 37.0 mm guns (1x2 guns), 1.55lbs / 0.70kg shells, 1933 Model
Anti-aircraft guns in deck mount
on centreline aft
4 - 0.31" / 7.9 mm guns (2x2 guns), 0.02lbs / 0.01kg shells, 1933 Model
Machine guns in deck mounts
on side, all forward
Weight of broadside 17 lbs / 8 kg
Shells per gun, main battery: 80

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.59" / 15 mm 0.39" / 10 mm -
2nd: 0.39" / 10 mm - -

Machinery:
Diesel Internal combustion motors,
Direct drive, 2 shafts, 2,000 shp / 1,492 Kw = 21.18 kts
Range 1,500nm at 12.00 kts
Bunker at max displacement = 19 tons

Complement:
25 - 33

Cost:
£0.076 million / $0.303 million

Distribution of weights at normal displacement:
Armament: 2 tons, 1.0 %
Armour: 1 tons, 0.6 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 1 tons, 0.6 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.0 %
Machinery: 58 tons, 30.4 %
Hull, fittings & equipment: 104 tons, 54.4 %
Fuel, ammunition & stores: 15 tons, 7.9 %
Miscellaneous weights: 11 tons, 5.7 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
305 lbs / 138 Kg = 23.7 x 3.0 " / 75 mm shells or 0.3 torpedoes
Stability (Unstable if below 1.00): 1.14
Metacentric height 0.6 ft / 0.2 m
Roll period: 11.3 seconds
Steadiness - As gun platform (Average = 50 %): 50 %
- Recoil effect (Restricted arc if above 1.00): 0.08
Seaboat quality (Average = 1.00): 1.14

Hull form characteristics:
Hull has a flush deck
and transom stern
Block coefficient: 0.380
Length to Beam Ratio: 6.77 : 1
'Natural speed' for length: 14.47 kts
Power going to wave formation at top speed: 69 %
Trim (Max stability = 0, Max steadiness = 100): 43
Bow angle (Positive = bow angles forward): 20.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 13.12 ft / 4.00 m
- Forecastle (20 %): 10.50 ft / 3.20 m
- Mid (50 %): 9.35 ft / 2.85 m
- Quarterdeck (15 %): 9.35 ft / 2.85 m
- Stern: 8.20 ft / 2.50 m
- Average freeboard: 9.88 ft / 3.01 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 112.7 %
- Above water (accommodation/working, high = better): 142.7 %
Waterplane Area: 1,947 Square feet or 181 Square metres
Displacement factor (Displacement / loading): 133 %
Structure weight / hull surface area: 28 lbs/sq ft or 134 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.79
- Longitudinal: 8.28
- Overall: 1.00
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is excellent

Project 610, shes larger than a Farmile D so she should be able to take a third 800 HP engine to boost her speed up abit.

You might have to increase her beam slightly to get her CS strength back up but ships this size are a bugger to design in SS anyway. Maybe some CT armor as well could prove usefull.

Project 611, I like her, larger than my own Type 1 Motor launch and Type 3 subchasers, with a reasonable speed.

AP shells for 75mm guns?!

Quoted

AP shells for 75mm guns?!

Why not? There certainly were such things (if more often used by the armies than the navies of the world).

I thought AP shells don´t make much sense below a certain size - and 75mm shells are too small.

Gavin surely knows the detailes...

Project 610

Aero Petrol engines are a no-no on such a ship. With those engines you have 3 speed settings; off, fast, and very fast. Which is why MTBs tend to have auxilary electric motors for making 5knts or so. However thats not really enough in a seaway. You'd be better with a single 1000hp diesel or so instead. I'm not keen on the direct drive either - try spinning a propellor at 2000rpm, probably won't end up going anywhere. Really I wouldn't use SS at all. Just find a similar craft and slightly modify it. The HMLs seem like a good bet, but this is overarmed.

I'm not sure what you intend to escort your MTBs against, but they'll be cruising at 30-35knts. Speed and surprise are the key.

Such a small AP round makes little sense given the threat. a 75mm AP round is essentially solid shot - which will travel through a boat's hull and out of the other side. In a tank it is more contained. Far better to use HE instead, 1 round will destroy just about any light craft.

AP rounds were made down as small as .50" or even smaller. Now, the smaller ones might be solid, or have only a very small percentage of their weight as either explosive or incendiary fill, but they were certainly produced and used. For example, the US produced the Mk 29 AP round for the 3"/50, and the Mk 81A2 AP round for the 40mm Bofors. The Russians produced AP rounds for various of their guns, including the 45mm/46 21-K, the 76.2mm/55 Pattern 1935, and the Germans had AP rounds for their 88mm and the automatic 37mms.

Gavin, can you elaborate on the speed setting issue with Aero engines? Seems odd considering many tanks adopted Aero engines as well with a wide range of results.

Probably "reduction gear" is the key word here.

I've based my own designs primarily on British and American designs and using petrol powered engines, similar to the Packard 4M2500.

The actual 4M2500 was developed as a result of the need to obtain an indiginous design so as to not rely on foreign designs. Before the 4M2500 engine was developed however the 500hp Napier Lion, an Aero engine, was a popular marine powerplant durring the 1920's.

The only downside to this engine I can find in my sources is the power rating which was considered by Hubert Scott-Paine of the British Powerboat company to be insufficient.

Paine's experience with the Napier Lion proved usefull when he obtained permission to utilise the Merlin engines and helped Derby design engineers design suitable ahead and astern gears for the engine.

The Packard engines were obtained in 1939 as a result of Scott-Paines concern about an unnamed British diesel engine, then being designed, actually emerging as a successfull engine.

The tank aero engines (or the meteor at least) used 67oct, produced less than 1/2 the power and weighed considerably more than the aircraft versions. I haven't heard to problems with them, but then i don't know much about tanks.

The Isotta-Fraschini engines used in MAS and other small craft (for about 80years! of continual refinement) definitely had the issue. Max power was 1150hp at about 2500rpm iirc. The engine is optimised for 1500-2000rpm, where it is by far the most efficient. At 10knts or so you'll only be needed 100hp or less, i.e. c 500rpm which the engine really doesn't like. Thats why you adopt small electric motors for small scale cruising. Also, the engines are deafening, which is why Italian MAS crew had headphones integrated into their helmets. I'll have to look into the gearing.

The Packard 4M2500 doesn't exist in 1932, so I can't really see how you base Atlantis' engines on it. Most engines in use are 500hp-1000hp and unreliable, with few exceptions.

The unnamed British diesel engine would be the Napier Deltic, which was pretty succesful in trains.

With these sorts of engines, Italy is currently developing;

Isotta-Fraschini Asso 1000 - 57L petrol 1000hp, uprated to 1150hp by mid-30s
Fiat CRM (diesel version of Asso), eventually produces 1840hp.
Fiat- Guidoni Diesel: Much larger 80-100L 90degree V16 producing 2500hp currently. Eventually expected 4000-5000hp.

I did state similar to the Packard 4M2500 not identical. The ship designs themselves are based on British/U.S. designs, not the engines.

But there are no similar engines nor British/American MTBs from the early 30s. Actually the only countries building MTBs were Italy and Russian, and in limited numbers.

Go for a double Lion instead combining the two to make a engine of about 50L with 1000hp. Might have some problems combining the W-shape so adopt a double-VV instead.

And Germany, in very limited numbers, using gasoline (1931 boats) or diesel (1933 and later boats) engines. See here for details. That's why WW Germany is building them in limited numbers right now: I'm following the historical pattern of build some, fix bugs, build a few more, fix bugs, etc.

An alternative to the British engine would be the DB BFz engine used on the Schnelleboote 1931's, that would give you 1000 hp without having to link two smaller engines together.

Quoted

Originally posted by Red Admiral
But there are no similar engines nor British/American MTBs from the early 30s. Actually the only countries building MTBs were Italy and Russian, and in limited numbers.

Go for a double Lion instead combining the two to make a engine of about 50L with 1000hp. Might have some problems combining the W-shape so adopt a double-VV instead.

I think your interpritation of "similar" is different to mine, granted an engine "similar to" the Packard 4M2500 would imply that it closely resembles that engine.
IIRC however Canis has an alternate history for these engines, designing "similar" engines several years earlier.

Your also using historical Italian and Russian programs to justify Atlantean ones, yet the alt history Italy to my knowledge isn't following the historical building program nor is Russia.

I'm not sold on the idea that a 1000 hp Aero engine in a MTB isn't possible considering the UK developed an 800 HP engine in 1920, the Rolls-Royce Buzzard. With 6 years of developement whats to stop it from being used as a marine engine for racing boats?

http://en.wikipedia.org/wiki/Rolls-Royce_Merlin

Quoted

Your also using historical Italian and Russian programs to justify Atlantean ones, yet the alt history Italy to my knowledge isn't following the historical building program nor is Russia.

I adapted it considerably when everyone else started building 40s-era MTBs. Prior to MAS500 series everything else is historical design and time.

The engines used in these boats are not standard aero engines. They are considerably heavier and produce less power because of using lower octance fuel [more readily available] and mostly non-supercharged. At this period you are limited to about 20hp/L and 0.4lb/hp for a marine engine. You don't want it to break. Reliability was the key to these engines, which is why the Isotta-Fraschini was used by the RN and is still in use today.

There isn't a great deal to limit engine development. Find a 50L aero engine from the early 30s and use that as the basis. Or develop your own engine using the benchmarks above. What about a U16 to allow easier access to the cylinders [at the expense of rpms]

Engine definitions set aside....

I still have problems simming an at least decent MTB with SpringSharp. :o/ No way to get a 34+kn boat working on ~70ts or something similar.

Has anybody heard of Ian lately? What´s the status of his latest SS improvement project?

Don't try MTBs with SS. It is manifestly unsuited for these. Its generally unsuitable for ships under 1000tons


Beta release of new SS soon. I asked Ian about a month ago if he needed help checking through the code, got a yes answer but haven't heard much from him since.

Quoted

Originally posted by Red Admiral

Quoted

Your also using historical Italian and Russian programs to justify Atlantean ones, yet the alt history Italy to my knowledge isn't following the historical building program nor is Russia.

I adapted it considerably when everyone else started building 40s-era MTBs. Prior to MAS500 series everything else is historical design and time.

Not sure which 40's designs your refering to, the MTB-1 type is based on the UK MTB 102 design, itself a 1937 design and the CMB design also based on a UK design, the the CMB type 3, a late WW1 design.

If we are to use history as a strict guidline then yes the designs would be more advanced, historically interest in MTB's waned after the war only to be renewed in the early thirty's.

Atlantis, not having much in the way of MTB's durring the war would have every reason to pursue the technology when others have lost interest.

I'd assume that the Atlantean 1200 hp engines would simply be two 600 hp engines linked togeather as with other engines. I can't speak for American engines but I am certainly looking at any info on Packard engines that I can find.

I agree on SS and MTB's being a horrible combination.

With all these engine issues, It's nice to know I am sitting on the world leaders in diesel marine engines in Denmark....Burrmeister & Wain!!