WesWorld

Quoted

Patrolboat:

Dagu - Class

Data:
Displacement: 65 t
Length: 27,73 m
Wide 7,16 m
Draught 1,05 m
Engine 2 Huang Po Diesel-Engines M 50 F3
Power 3.530 KW
Speed: 34,3 kn


Armament
1x4 25 mm Machinegun
1x2 12,7 mm Machinegun
Waterbombs

Seems a wee bit ahead of the current designs from other country's. Is this a historical design?

Seems to be soviet on account of the duple 57mm gun aft.

Acctually I'm more curious as to the engine outfit as thats where the real gem of these designs is at.

Quoted

Engine 2 Huang Po Diesel-Engines M 50 F3
Power 3.530 KW
Speed: 34,3 kn

I'm afraid I'm not familiar with the convertion table for KW to HP. Is it a total KW of 3,530 or per engine?

My Magic Calculator tells me:
1 HP = 0.7457 kW
1 kW = 1.341 HP

... so that would be 4733.73 HP.
And I would assume that that is the combined output of the two engines.

I knew that I recognised the drawing style from somewhere.

3530kW is 4700hp combined, so 2350hp engines, which don't exist.

I'd expect China to have help from a country that already operates such types; Atlantis, Great Britain, Germany, Italy...

Thats quite abit of power for 2 engines, even diesels. A 1957 design wouldn't likely be the best choice of designs to copy for 1931/2. The most modern Atlantean designs use three 1,200 hp Roth-Packard liquid cooled engines to reach 41 knots.

Thats a total of 3,600 hp and its effectively on the edge of realism considering 1000 hp engines are starting to make their way into aircraft now.

If you split the hp between 4 engines it would seem more realistic. Likely four 900/1000 hp engines would be utilized.

The list of country's already building these types of boats makes it super easy for China to aquire some outside designs or assistance in designing one.

Its the engines that are the problem. Those Packard engines don't exist yet. We're limited to about 20hp/litre at the moment so 1200hp requires 60litre engine instead of the 41litre Packard V12. Sure a larger engine could be built, but it will weigh considerably more, which means less weight for torpedoes and guns. Nothing against introducing alternate engines, but more powerful ones will be heavier. In the case above with the Packard, its neccessary to ditch the torpedoes because of the excess engine weight. Or maybe just reduce the gun armament to 2-3 mgs.

The initial batch of boats are armed with 18" torpedo's so yeah they have ditched weight for the motor's. They are about 5 years ahead of their time, but certainly not 20 years.

The Dagu class could likely use 3x1000 HP motors to achieve the same specified speed of 34.3 knots.

Here are some various engines and their BHP/weight

Napier Sea Lion - 500- 1652lb
Isotta-Fraschini -1100- 2699lb
Rolls-Royce merlin-1100- 2240lb
Packard 4M-2500 -1500- 3017lb

IIRC these are 1939 figures so I'm guessing that a 1000HP motor in 1932 would weigh about the same as the 1939 Packard engine (3000 lb's).

Using three 1000 HP engines would give you about 4.5 tons of weight devoted to engines.

The twin 50 cal would weigh about 1200-1500 lb's depending on the number of rounds carried (1300 to ?).

The two twin 25mm mounts would likely be 3,000 lb's per twin mount depending on the number of rounds carried. A powered mounting would likely weigh more, maybe 2 tons?

That would be a total of 7.25 tons for main armament and engines.

How many DC would the Dagu carry?

I'd think 6 DC's would seem reasonable for a patrol boat, basically hit and run to temperarily deter a sub.

Going with 60 tons , 2x2 25 mm Machinegun,1x2 12,7 mm Machinegun, 6xDC thrower and DC rail I'd say shes similar in size to the Atlantean motor launchs.

Its reasonable compared to Stefano Turr. Similar size, power and speed. Just trading torpedoes for 25mm guns. Having torpedoes gives more options, more likely for China to encounter larger ships than to be fighting MTBs. The Fiat diesels used were unreliable and underpowered compared to the petrol engines used in other MAS. Also, only 1000 more hp for a boat 3 times larger so speed suffered.

Mas Stefano Turr

Characteristics:

Displacement 58t standard, 61.6t normal, 68.5t full load
Dimensions 32.0m x 5.95m x 1.32m (just 0.95m according to Conway's)
Engines 4x Fiat V1616 Diesels, 4x 750hp
Speed 34kts project, 30-32kts real
Range 750nm/25kts - 1,582nm/16.6kts
Fuel 10t normal, 16t full load
Crew 16
Armament 4x 450mm torpedoes, 2-3x 13.2mm MG, 1x 6.5mm MG, 12x ASW bombs

http://forum.axishistory.com/files/turr_180.jpeg

Seems reasonable.

You could likely add another twin 12.7mm mount to give you one 25mm mount forward, one aft and two twin 12.7mm mounts on either side of the wheelhouse.