US WW2 Fleet Boats vs German Type IX - Range in Submarines Forum

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US WW2 Fleet Boats vs German Type IX - Range

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Kitsune		#21	[-]
Posts: 1393 Mar 20 12 5:58 PM Reply Quote More My Recent Posts	On the other side, France to the Gulf of Mexico is only about 4000 nm as well and they always seem to have refueled on route as well. Been a few cases where German U-Boats ran out of fuel as well Any cases where U-Submarines ran out of fuel on Pacific Patrols? “Wouldn't it be much worse if life were fair and all the terrible things that happen to us, come because we actually deserve them? So now I take comfort in the general hostility and unfairness of the Universe” Marcus Cole - Babylon 5 Last Edited By: Kitsune Mar 20 12 6:02 PM. Edited 1 times.
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sergeante		#22	[-]
Posts: 4252 Mar 20 12 6:06 PM Reply Quote More My Recent Posts	Kitsune wrote: On the other side, France to the Gulf of Mexico is only about 4000 nm as well and they always seem to have refueled on route as well. Been a few cases where German U-Boats ran out of fuel as well Any cases where U-Submarines ran out of fuel on Pacific Patrols? I don't know about US boats running out of fuel on the return trip, but it wouldn't surprise me if a few had to get a tow. Otherwise, the fact that the Germans refueled en route suggests that the endurance figure given was total distance that could be achieved under optimum conditions, not patrol radius.
Viper		#23	[-]
Posts: 4841 Mar 20 12 6:35 PM Supreme Dictator of the Universe Reply Quote More My Recent Posts	I don't recall any boats running out of fuel either. AFAIK it was uncommon for a boat not to refuel at Midway but sometimes boats didn't have time or whatnot based on orders or circumstances. I seem to recall some skippers lamenting that fact on occasion. Ask not the Elves for advice, for they will tell you both yes and no.
Kitsune		#24	[-]
Posts: 1393 Mar 20 12 6:40 PM Reply Quote More My Recent Posts	Many times, German U-Boats would refuel twice, once inbound and once outbound, from either a tanker submarine or another U-Boat with some spare fuel. Did US Submarines ever refuel each other? “Wouldn't it be much worse if life were fair and all the terrible things that happen to us, come because we actually deserve them? So now I take comfort in the general hostility and unfairness of the Universe” Marcus Cole - Babylon 5
Viper		#25	[-]
Posts: 4841 Mar 20 12 9:25 PM Supreme Dictator of the Universe Reply Quote More My Recent Posts	Kitsune wrote: Many times, German U-Boats would refuel twice, once inbound and once outbound, from either a tanker submarine or another U-Boat with some spare fuel. Did US Submarines ever refuel each other? Not that I recall. They traded spare parts and movies often though. Ask not the Elves for advice, for they will tell you both yes and no.
sergeante		#26	[-]
Posts: 4252 Mar 20 12 10:17 PM Reply Quote More My Recent Posts	US boats certainly didn't have an overboard fuel pump. The only way fuel could be expelled out of the tanks was by blowing it out with compressed air. But the boat would have to ship fuel transfer lines and connecting gear that fitted the fuel filling connections on deck. I doubt that was standard equipment. I'd also question whether that was standard equipment on German boats.
Viper		#27	[-]
Posts: 4841 Mar 21 12 1:25 AM Supreme Dictator of the Universe Reply Quote More My Recent Posts	sergeante wrote: US boats certainly didn't have an overboard fuel pump. The only way fuel could be expelled out of the tanks was by blowing it out with compressed air. But the boat would have to ship fuel transfer lines and connecting gear that fitted the fuel filling connections on deck. I doubt that was standard equipment. I'd also question whether that was standard equipment on German boats. Maybe on the Milk Cow boats but they were unique I think. Ask not the Elves for advice, for they will tell you both yes and no.
Kitsune		#28	[-]
Posts: 1393 Mar 21 12 1:49 AM Reply Quote More My Recent Posts	According to Clay Blair, normal U-Boats (non tankers) would also refuel other U-Boats “Wouldn't it be much worse if life were fair and all the terrible things that happen to us, come because we actually deserve them? So now I take comfort in the general hostility and unfairness of the Universe” Marcus Cole - Babylon 5
DCJ		#29	[-]
Posts: 232 Mar 21 12 6:30 AM Reply Quote More My Recent Posts	Kitsune wrote: Trying to do some calculations here A US Gato appears to have about 420 tons of fuel (using gallons and converting to weight as diesel fuel) at wartime load? A German Type IXC/40 seems to have 214 tons of fuel It looks like they require similar power for similar speeds - 21 knots at 5400 HP (Gato) and 19 knots at 4,400 HP (Type XI) Both are listed at around 11,000 nm at 10 knots Unless the US engines are very inefficient, it would appear as if something does not fit here Opinions? I've been turning this over in my head, because it does seem anomalous. Using some terribly crude estimates from Springsharp, it appears that, at 10 knots, a Gato class hull would require about 20 percent more power. That comes just from hull size, since the Gato was 60 feet longer and 5 feet wider in beam than a Type IX. So that's at least part of the explanation. As for the rest, my guess is that US engines were not so much inefficient, but rather that the MAN diesels used by the Type IX were very efficient. This description is taken the US postwar evaluation of the Type IXC: "The diesel engine selected for the IXC has several interesting compromises in design. In order to obtain the high power desired in each of the two engines for the limited direct drive RPM it was necessary to highly supercharge the engine. This was accomplished effectively by the exhaust turbine supercharger. However, in so doing, design limitations in engine size required the acceptance of high exhaust temperatures for a submarine installation. The resultant mean effective pressure and power for each cylinder are high, and the fuel rate over a wide range of operation is low." So, perhaps the Germans achieved very high fuel efficiency by supercharging the bejeesus out of their MAN diesels. Furthermore, it seems possible to me that the diesel-electric arrangement on the Gato class allowed it to develop power at higher RPMs than would be permissible in a direct-drive arrangement. That in turn would make it more practical for the Gatos accomodate less efficient engines that simply ran faster to produce the necessary power. As best I can tell, the MAN M9V operated at about half the RPM of a Fairbanks Morse 38. Last Edited By: DCJ Mar 21 12 6:59 AM. Edited 4 times.
Kitsune		#30	[-]
Posts: 1393 Mar 21 12 6:48 AM Reply Quote More My Recent Posts	Biggest problem I still have with that is that US Submarines, even those with the same engines but far more fuel. are still listed as 11,000 nm at 10 knots Now, the father in law of my sister was on WW2 submarines. He is very old though. Might be worth asking about it however. “Wouldn't it be much worse if life were fair and all the terrible things that happen to us, come because we actually deserve them? So now I take comfort in the general hostility and unfairness of the Universe” Marcus Cole - Babylon 5
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DCJ		#31	[-]
Posts: 232 Mar 21 12 6:56 AM Reply Quote More My Recent Posts	I'm not sure what you mean by "same engines." What I'm saying is that the German engines were more efficient, and thus needed less fuel to travel the same distance. Last Edited By: DCJ Mar 21 12 7:01 AM. Edited 1 times.
Kitsune		#32	[-]
Posts: 1393 Mar 21 12 7:28 AM Reply Quote More My Recent Posts	What I am arguing is that the Gato and Baleo are listed as having the same range while the Baleo has significantly more fuel. Besides, being that a Gato has something like 80% more fuel than a Type IX/40, doesn't 60% more fuel efficient sound like a bit much? Would we even get that comparing modern diesels vs 1940s diesels? I am kind of doing "back of the envelope" calculations and something seems wonky? “Wouldn't it be much worse if life were fair and all the terrible things that happen to us, come because we actually deserve them? So now I take comfort in the general hostility and unfairness of the Universe” Marcus Cole - Babylon 5
DCJ		#33	[-]
Posts: 232 Mar 21 12 8:11 AM Reply Quote More My Recent Posts	I didn't bring up the Gato/Balao issue and I don't have any interest in it. Last Edited By: DCJ Mar 21 12 5:11 PM. Edited 1 times.
Kitsune		#34	[-]
Posts: 1393 Mar 21 12 8:26 AM Reply Quote More My Recent Posts	DCJ wrote: I didn't bring up the Gato/Balao issue and I don't have any interest in it. I agree that it's an issue of "poorly vetted sources and slipshod editing." What is sad is that I got Friedman's book today and the 11,000 nm at 10 knots is repeated on both vessels (although very well could be "design") Wish we had fuel consumption as we do with US surface ships for WW2 Edit: The average fleet type submarine is capable of a speed of about 21 knots when operating on the surface and approximately 10 knots when submerged. This submarine has a cruising range in excess of 12,000 miles. From here http://www.maritime.org/fleetsub/chap1.htm#1D seems to indicate the numbers are more of a fudge factor number “Wouldn't it be much worse if life were fair and all the terrible things that happen to us, come because we actually deserve them? So now I take comfort in the general hostility and unfairness of the Universe” Marcus Cole - Babylon 5 Last Edited By: Kitsune Mar 21 12 9:29 AM. Edited 1 times.
sergeante		#35	[-]
Posts: 4252 Mar 21 12 5:45 PM Reply Quote More My Recent Posts	DCJ wrote: I've been turning this over in my head, because it does seem anomalous. Using some terribly crude estimates from Springsharp, it appears that, at 10 knots, a Gato class hull would require about 20 percent more power. That comes just from hull size, since the Gato was 60 feet longer and 5 feet wider in beam than a Type IX. So that's at least part of the explanation. As for the rest, my guess is that US engines were not so much inefficient, but rather that the MAN diesels used by the Type IX were very efficient. This description is taken the US postwar evaluation of the Type IXC: "The diesel engine selected for the IXC has several interesting compromises in design. In order to obtain the high power desired in each of the two engines for the limited direct drive RPM it was necessary to highly supercharge the engine. This was accomplished effectively by the exhaust turbine supercharger. However, in so doing, design limitations in engine size required the acceptance of high exhaust temperatures for a submarine installation. The resultant mean effective pressure and power for each cylinder are high, and the fuel rate over a wide range of operation is low." So, perhaps the Germans achieved very high fuel efficiency by supercharging the bejeesus out of their MAN diesels. Furthermore, it seems possible to me that the diesel-electric arrangement on the Gato class allowed it to develop power at higher RPMs than would be permissible in a direct-drive arrangement. That in turn would make it more practical for the Gatos accomodate less efficient engines that simply ran faster to produce the necessary power. As best I can tell, the MAN M9V operated at about half the RPM of a Fairbanks Morse 38. Supercharging probably did make the German engines somewhat more fuel efficient in some operational situations. But it's a self-limiting technology. You can only run the engines so hot before they break. And running engines any hotter leads to a higher parasitic load for running cooling water pumps. Also, blowers are themselves a parasitic load, whether run directly by mechanical power takeoff from the engine or through exhaust turbines (exhaust-driven blowers create higher exhaust pressures, which in turn creates more resistance on the exhaust stroke). In any case, they weren't 40-60% more efficient. Diesel was a fairly mature technology, even back then. WRT the engine efficiency of US boats, remember that one of the advantages of decoupling the egnines from the propulsion motors was that the engines could be run at optimum fuel efficiency most of the time. Only during speed runs or fast battery charging would they be operated at lower efficiency. Being able to run 1 to 4 motors independent of speed aided this.
DCJ		#36	[-]
Posts: 232 Mar 22 12 6:03 AM Reply Quote More My Recent Posts	sergeante wrote: Supercharging probably did make the German engines somewhat more fuel efficient in some operational situations. But it's a self-limiting technology. You can only run the engines so hot before they break. And running engines any hotter leads to a higher parasitic load for running cooling water pumps. Also, blowers are themselves a parasitic load, whether run directly by mechanical power takeoff from the engine or through exhaust turbines (exhaust-driven blowers create higher exhaust pressures, which in turn creates more resistance on the exhaust stroke). In any case, they weren't 40-60% more efficient. Diesel was a fairly mature technology, even back then. WRT the engine efficiency of US boats, remember that one of the advantages of decoupling the egnines from the propulsion motors was that the engines could be run at optimum fuel efficiency most of the time. Only during speed runs or fast battery charging would they be operated at lower efficiency. Being able to run 1 to 4 motors independent of speed aided this. Yes, I understand those things. Feel free to tell me your idea for how the Type IX went the same distance on half the fuel. Obviously my idea was too stupid to be the answer.
sergeante		#37	[-]
Posts: 4252 Mar 22 12 6:58 AM Reply Quote More My Recent Posts	DCJ wrote: Yes, I understand those things. Feel free to tell me your idea for how the Type IX went the same distance on half the fuel. Obviously my idea was too stupid to be the answer. Cool your jets, hotshot. Given the supercharging, the German engines probably were more efficient. It's just not possible that they could be all that efficient as to explain the difference. It's just one piece of the explanation. Another piece is that US boats were bigger and thus had higher propulsion power demands. Another piece is that US boats had proportionately higher ship's service and lighting power demands, over and above their absolute size. I've no objection to all of these things being parts of the answer. I just don't believe in magic bullets.
Kitsune		#38	[-]
Posts: 1393 Mar 22 12 6:59 AM Reply Quote More My Recent Posts	I would argue that there is a problem with the ranges with one, the other, or both. “Wouldn't it be much worse if life were fair and all the terrible things that happen to us, come because we actually deserve them? So now I take comfort in the general hostility and unfairness of the Universe” Marcus Cole - Babylon 5
sergeante		#39	[-]
Posts: 4252 Mar 22 12 7:21 AM Reply Quote More My Recent Posts	Kitsune wrote: I would argue that there is a problem with the ranges with one, the other, or both. Differing definitions may be another factor, but I've never seen different definitions of this or that metric lead to performace figures off by a factor of 2. I think all the possibilities discussed are contributing factors. Once again, no magic bullets wanted or accepted.
Kitsune		#40	[-]
Posts: 1393 Mar 22 12 7:37 AM Reply Quote More My Recent Posts	One other problem is that we lack any good really solid sources so we also don't know how "Off the Cuff" the numbers are Even Friedman does not seem to be much help Edit: If the power curves are anything close to the cube law, 80% power on a single engine (which if I am understanding is the efficient setting), it looks like they will usually cruise at greater than 10 knots. “Wouldn't it be much worse if life were fair and all the terrible things that happen to us, come because we actually deserve them? So now I take comfort in the general hostility and unfairness of the Universe” Marcus Cole - Babylon 5 Last Edited By: Kitsune Mar 22 12 7:42 AM. Edited 1 times.
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US WW2 Fleet Boats vs German Type IX - Range