AHQ: U-boat sinking rate to achieve victory?


Source:
nhungdoicanh: CANT Z.511

Never underestimate your allies.

The summary of specifications is that its best cruise was 300 km/h and that it had a flyout of 13 hours one way, an effective patrol radius of 4.5 hours and a time on station of 3 hours with 30 minutes RTB reserve. Best altitude was about 3000-5000 meters. Crew was 6 men. Had it been militarized, as Benny the Moose desired, it would have delivered frogmen teams on powered torpedoes to attack port shipping.

More practically, it was a candidate for an Axis equivalent to a Sunderland flying boat. It was designed to set down and be refueled open ocean.

And then there is this candidate...



Source:

Summary on this aircraft... similar specifications to the CANT Z.511 overall with a 6 or 7 man crew, capable of 4.5 hours flyout, 2 hours on station and 2x the warload. She worked. I think the bomb bay was designed to carry 45 cm (17.7") Si 200/450 x 5.36 Silurificio torpedoes. (Coffin nails).

Maritime strike bird all ready to go in 1941.
Never heard of the CANT Z 511, seems like a promising aircraft as it could take off and land fully loaded in rough seas.

I've previously suggested that the German ditch their shitty He 177 and just build P.108s under license as their heavy bomber. AFAIK the Germans in OTL operate a couple P.108s as transport aircraft late in the war, after Italy fell to the Allies.
There was also a version of the P.108 with a 102mm anti-ship cannon, I think this one might be the marine patrol plane you're looking for.
 
Ah they're faster, I forgot that, yeah that makes thing much worse for your U-Boats in terms of the space taken up by fuel. Okay to address this we leave the realms of history and get into the subject of physics.

To get to a certain speed you need to inject a certain amount of energy into an object. Ignoring all factors like hydrodynamic drag the basic equation is:

Kinetic Energy = 1/2 mass x velocity2 (where 2 means squared). 1 knot is roughly 0.51m/s so lets do some comparisons assuming an object weighing 1kg for simplicity

Speed(Knots)KE(Joules) per kilo
1013.005
1218.727
1529.261
2052.02

Put it another way, whatever savings you might make in fuel capacity by reducing range are likely to be more than offset by the demands of increased speed. Oh and if you don't want to be surfacing even more frequently than OTL you are also going to have to have a much bigger battery pack. And remember those number are a theoretical minimum, engine efficiency and hydrodynamic drag make them much worse but even with 100% efficiency and zero drag they can never be less than that. This is a major reason why BTW subs only really got fast after nuclear power was available.
Yeah but then there's the Type IX-D.
23000 mile range which was 10000 miles better than the original Type IX-A, but also faster than the original Type IX-A at 19.2 knots max speed.
How do you explain that?
 
how much length is absorbed by fuel in the original G7 design
It is not fuel. It, the entire torpedo, is designed like a miniature submarine. So it has to be sausage sectioned along its cylinder length and its flotation has to be proportionally distributed so that as it moves under power, it flies through the water under "cylinder lift" in a stable fluid dynamics fashion similar to the way that pressure differential along the upper boundary of a missile's cylinder body "lifts" the missile and it is the fins that mainly provide nose "point" as the missile "flies". The same exact principle, and same need for sectional mass balancing and distribution is required. This is a quality of torpedo design that makes it hard to change the parameters of the torpedo as to mass distribution without a lot of tank runs to get the flotation and lift coefficient correct.

IOW, you cannot add explosive and decrease fuel without moving the CENTER OF GRAVITY and that means your fish either has to speed up or slow down and will either be nose light or heavy and you are back to the ___ ___ed ballast floats and collars again. The Wallies solved it by better dying through chemistry and/or engineering. They made sure to either pack more bang into the warhead by using a more unstable explosive (Torpex) at the same weight as the TNT it replaced, or if they increased the weight of the warhead by packing the cavity with more plastique, they found a way to add a float cell into the existent cavity to keep the nose module the same proportional sectioned flotation vs specific gravity of the fluid the torpedo "flew" through in that module.

The goal was to keep the torpedo, as a system, sausage-sectioned and proportionally massed so its "flying" and "pointing" characteristics did not change from its original solved parameters as much as possible.

Now you see the problem with "solid fueled torpedoes" and why sea water ballast intake over the run is used in "some" liquid fueled torpedoes and in the one or two solid fueled torpedoes that are apparently successful?

Had to fix the physics explanation on nose heavy fish. I screwed up. You can either make it go faster or you can add an air flask to float the nose up by float displacement as you densify the explosive charge.
 
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Yeah but then there's the Type IX-D.
23000 mile range which was 10000 miles better than the original Type IX-A, but also faster than the original Type IX-A at 19.2 knots max speed.
How do you explain that?
Already explained. (From Wiki)

Design[edit]
The German Type IX D 2 were considerably larger than the original Type IXs. U-852 had a displacement of 1,610 tonnes (1,580 long tons) when at the surface and 1,799 tonnes (1,771 long tons) while submerged.[3] The U-boat had a total length of 87.58 m (287 ft 4 in), a pressure hull length of 68.50 m (224 ft 9 in), a beam of 7.50 m (24 ft 7 in), a height of 10.20 m (33 ft 6 in), and a draught of 5.35 m (17 ft 7 in). The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines plus two MWM RS34.5S six-cylinder four-stroke diesel engines for cruising, producing a total of 9,000 metric horsepower (6,620 kW; 8,880 shp) for use while surfaced, and two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1,000 shaft horsepower (1,010 PS; 750 kW) for use while submerged. She had two shafts and two 1.85 m (6 ft) propellers. The boat was capable of operating at depths of up to 200 metres (660 ft).[3]

The submarine had a maximum surface speed of 20.8 knots (38.5 km/h; 23.9 mph) and a maximum submerged speed of 6.9 knots (12.8 km/h; 7.9 mph).[3] When submerged, the boat could operate for 121 nautical miles (224 km; 139 mi) at 2 knots (3.7 km/h; 2.3 mph); when surfaced, she could travel 12,750 nautical miles (23,610 km; 14,670 mi) at 10 knots (19 km/h; 12 mph). U-852 was fitted with six 53.3 cm (21 in) torpedo tubes (four fitted at the bow and two at the stern), 24 torpedoes, one 10.5 cm (4.13 in) SK C/32 naval gun, 150 rounds, and a 3.7 cm (1.5 in) SK C/30 with 2575 rounds as well as two 2 cm (0.79 in) C/30 anti-aircraft guns with 8100 rounds. The boat had a complement of fifty-five.[3]
Class overview from Wiki here.

The physics is as described previously.
 
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Yeah but then there's the Type IX-D.
23000 mile range which was 10000 miles better than the original Type IX-A, but also faster than the original Type IX-A at 19.2 knots max speed.
How do you explain that?
Well there's a big difference between max speed and normal cruising speed. Short bursts at high speed aren't going to drastically affect cruising range. Also as I pointed out that's the theoretical minimum amount of energy required. It doesn't allow for the innate inefficiency of real world engines (diesel can get to about 50% efficiency), hydrodynamic drag or of course taking measures to reduce the weight of the submarine, or you know just fitting bigger fuel tanks. So yeah you can improve real world machines, you just can't do better than the mathematical limit.

ETA: checked the wiki for the Type IX

Range:
  • 23,700 nmi (43,900 km; 27,300 mi) at 10 knots (19 km/h; 12 mph) surfaced
  • 115 nmi (213 km; 132 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged

And it looks like you've confused Knots with Km/h. Regardless that range only applied if it was averaging 10 knots
 
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Bigger sub needs a more powerful blow system for faster ballast intake/blow management and cycling. Americans had those pumps. Those kinds of pumps are noisy and kill you dead in a sub vs escort engagement. Big problem requiring a solution that has resisted efforts for decades. Maybe Archimedes screws could help, but it is one hello of an engineering problem.
 
Well there's a big difference between max speed and normal cruising speed. Short bursts at high speed aren't going to drastically affect cruising range. Also as I pointed out that's the theoretical minimum amount of energy required. It doesn't allow for the innate inefficiency of real world engines (diesel can get to about 50% efficiency), hydrodynamic drag or of course taking measures to reduce the weight of the submarine, or you know just fitting bigger fuel tanks. So yeah you can improve real world machines, you just can't do better than the mathematical limit.
You can cheat a little by making long skinny cylinders for speed efficiency under water, but you sacrifice sectional stability, risk "crash through" and lose your knife fighting turn ability underwater when you go long and skinny. Notice the difference between Russian and American boats?

The Americans built for ambush. The Russians built for knife-fighting. Who was right? The Russians settled for second best because they knew they would be the ones surprised.
 
Bigger sub needs a more powerful blow system for faster ballast intake/blow management and cycling. Americans had those pumps. Those kinds of pumps are noisy and kill you dead in a sub vs escort engagement. Big problem requiring a solution that has resisted efforts for decades. Maybe Archimedes screws could help, but it is one hello of an engineering problem.
Trying to understand the systems you’re discussing here. The ballast tanks are not blown when diving. The vents on top are just opened. The air is vented out while diving. Once the tanks are full the vents are shut. WW2 boats used a “negative” tank that they would fill to help them dive faster. They would pump this tank almost empty around 40-50 feet down. While submerged they would use the trim tanks, or in some cases, people, to trim the boat. When surfacing a low pressure blower (current ones are screw type, WW2 I don’t know what type) is used to blow the ballast tanks under normal conditions. Emergency blow is pressurized air flasks.
 
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Yeah but then there's the Type IX-D.
23000 mile range which was 10000 miles better than the original Type IX-A, but also faster than the original Type IX-A at 19.2 knots max speed.
How do you explain that?
The top speed could be faster but the cruise speed(for best range) won't necessarily be faster.Just upgrading the engine power(same basic engine)would increase the speed.
 
Trying to understand the systems you’re discussing here. The ballast tanks are not blown when diving. The vents on top are just opened. The air is vented out while diving. Once the tanks are full the vents are shut. WW2 boats used a “negative” tank that they would fill to help them dive faster. They would pump this tank almost empty around 40-50 feet down. While submerged they would use the trim tanks, or in some cases, people, to trim the boat. When surfacing a low pressure blower (current ones are screw type, WW2 I don’t know what type) is used to blow the ballast tanks under normal conditions. Emergency blow is pressurized air flasks.
You could suction water in faster, but that requires a mechanical (a pump to force air out by forced flushing.). The trim tank did use a pressure system (Blow negative.) off an air bottle to empty.

Anyway, the pumps were/are there, so is the air blow and it is noisy.
 
And it turned out its cruising speed was still 10 knots to get that 23000nmi range.
Fuel consumption is determined more by how big of a bow wave you make than how powerful your engines are. The faster you go relative to the waterline length the bigger the wave so long vessels take less power to go the same speed for the same displacement....but the hull of long vessels take up a greater percentage of the vessels weight so the payload decreases.
Never heard of the CANT Z 511, seems like a promising aircraft as it could take off and land fully loaded in rough seas.

I've previously suggested that the German ditch their shitty He 177 and just build P.108s under license as their heavy bomber. AFAIK the Germans in OTL operate a couple P.108s as transport aircraft late in the war, after Italy fell to the Allies.
There was also a version of the P.108 with a 102mm anti-ship cannon, I think this one might be the marine patrol plane you're looking for.
have you ever been on the north atlantic in rough seas?you might not want to land any plane in that.
 
have you ever been on the north atlantic in rough seas?you might not want to land any plane in that.
"The Z.511 had its first test flights at Monfalcone, Venezia Giulia (north-eastern Italy) between October 1940 and March 1942. Between 28 February and 1 March 1942, test pilot Mario Stoppani succeeded in taking off and landing fully loaded in very rough seas, with 1.5 m (4.9 ft) waves and winds of 55–65 kilometres per hour (30–35 kn; 34–40 mph). The Z.511 prototype was then transported to Grado, Venezia (further away from the insecure Yugoslavian border) for further evaluations; the last test and operational flight occurred on 1 September 1943, two days before the Italian Armistice was signed."
 
It is not fuel. It, the entire torpedo, is designed like a miniature submarine. So it has to be sausage sectioned along its cylinder length and its flotation has to be proportionally distributed so that as it moves under power, it flies through the water under "cylinder lift" in a stable fluid dynamics fashion similar to the way that pressure differential along the upper boundary of a missile's cylinder body "lifts" the missile and it is the fins that mainly provide nose "point" as the missile "flies". The same exact principle, and same need for sectional mass balancing and distribution is required. This is a quality of torpedo design that makes it hard to change the parameters of the torpedo as to mass distribution without a lot of tank runs to get the flotation and lift coefficient correct.

IOW, you cannot add explosive and decrease fuel without moving the CENTER OF GRAVITY and that means your fish either has to speed up or slow down and will either be nose light or heavy and you are back to the ___ ___ed ballast floats and collars again. The Wallies solved it by better dying through chemistry and/or engineering. They made sure to either pack more bang into the warhead by using a more unstable explosive (Torpex) at the same weight as the TNT it replaced, or if they increased the weight of the warhead by packing the cavity with more plastique, they found a way to add a float cell into the existent cavity to keep the nose module the same proportional sectioned flotation vs specific gravity of the fluid the torpedo "flew" through in that module.
Thanks for the lesson in torpedo design. :) :cool: :cool: I obviously don't know enough.
whatever savings you might make in fuel capacity by reducing range
I was actually not trying to reduce fuel capacity. I was accepting there would be a range reduction consequent to increased fuel burn to produce a higher cruising speed. (More power requires more fuel.) I hoped to mitigate it somewhat with better hydrodynamic qualities (greater fineness). Was that estimated reduction too low?

It's possible the Germans figure out creative ways to carry more fuel, just as the U.S. did, like turning over ballast tanks to bunkerage. (The exact mechanism of that, IDK.)
Again more successful U-boats begets the reward of a stronger Allied response earlier.
Very probably. The obvious one, IMO, is Newfoundland, given Halifax (not to mention Boston & NYC). That doesn't bode well for U-boat successes against HX convoys... :'(
You can cheat a little by making long skinny cylinders
That works if you can optimize for dived performance. WW2 boats can't afford that. About the best you can ask for is the blunt "GUPPY bow".
lose your knife fighting turn ability underwater
The Germans might (just) have added a dorsal rudder, like the U.S. did postwar, & get better turning performance. (IDK how much better offhand, but it was considered a lot better, from what I've read.)

Correction: I need to retcon that notional Type IX design; I managed to misread the armament as 6 bow tubes, instead of 4...:oops::oops::oops::oops: (I'd consider adding two more aft, but I'm unconvinced it matters.) I'd also seriously consider reducing the torpedo loadout from 22 to 18 (two reloads/tube, plus one in the tube) or 16 (one reload/tube aft).

In ref the pumps: I've already suggested the trim pumps needed to be quieted (by how much, IDK; I do know U.S. pumps were damn noisy, & BuShips seemed not to give a damn...:mad::rolleyes: ). Improving the ballast tank venting to improve flooding for dives would be a good idea. More limber holes might help, too. (At the time, I doubt self-noise from them was a Thing.)

To get higher cruise speed (which I've presumed), can the screws be optimized? Or does that sacrifice fuel burn at lower speed, when you'll spend (on average) more time not at cruise? (Of course, with better training, just turning the damn diesels off when you've got a full charge & nowhere in particular to go, as O'Kane did, might be a prewar lesson learned...) And, in case nobody noticed, I absolutely rejected anything like 23000nm range long since, so the IX-D being bigger is moot.
 
"The Z.511 had its first test flights at Monfalcone, Venezia Giulia (north-eastern Italy) between October 1940 and March 1942. Between 28 February and 1 March 1942, test pilot Mario Stoppani succeeded in taking off and landing fully loaded in very rough seas, with 1.5 m (4.9 ft) waves and winds of 55–65 kilometres per hour (30–35 kn; 34–40 mph). The Z.511 prototype was then transported to Grado, Venezia (further away from the insecure Yugoslavian border) for further evaluations; the last test and operational flight occurred on 1 September 1943, two days before the Italian Armistice was signed."
thats a calm day on the north atlantic
 
Fuel consumption is determined more by how big of a bow wave you make than how powerful your engines are. The faster you go relative to the waterline length the bigger the wave so long vessels take less power to go the same speed for the same displacement....but the hull of long vessels take up a greater percentage of the vessels weight so the payload decreases.
You can apply a cylinder break at the bow plane foot to break up that wave height and surface drag a little bit.

have you ever been on the north atlantic in rough seas?you might not want to land any plane in that.
Yes. Hurricane. Not pleasant.
 
Not really. My father told me that the weather in the Atlantic isn't always that bad, at least from his experiences in the Royal Canadian Navy.
Definitely worse than the Pacific though.
I used to watch the DDE/h's alternate between having the sonar dome then the props out of the water as they came alongside for resupply.
 
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