RTB speeds.

rudewarrior · 04-13-10, 10:35 PM

Hi.

Read quite a few books on the Atlantic War, but I didn't see anything on this particular subject. I'm curious about the speeds at which they returned to their bases. I assume that they would return at top speeds in order to get the weapons platform reoutfitted as quickly as possible, and back to fighting. However, would this cause engine issues?

I never found any references to it in the books I have read so far. They only talk about having enough fuel "to get home." Yeah buddy, I know. But how fast?

Thanx.

timmy41 · 04-13-10, 11:20 PM

considering the ranges at which they operated, I seriously doubt they could RTB at anything beyond cruising speed without having a bit to spare for bad weather and detours. Plus, all machines fail, especially ones that are used almost 24/7, and were built by rushed industry that may not have had all the proper tools available at times. There are not always spare parts available, so one does not want to risk any frivolous damage from running a machine too hard too long that may not allow them to get home at all. on top of all that and more, this is the 40s, and lots of these things were designed in the early 30s.

brett25 · 04-14-10, 01:31 AM

i just finished reading Iron Coffins by Herbert Werner, you can read here that many of the u boat casualties later in the war were the U boats returning to their bases in the Bay of Biscay. The allies were waiting for them and the uboat's last leg home often became a turkey shoot for the allied aircraft. So depending on how you opted-either you returned slowly under water, undetected, or all out full throttle running the gauntlet. Either way your chances were not good, as, on average, only one out of every four boats would make it back.

HW3 · 04-14-10, 02:49 AM

I doubt they would have had enough fuel left, after patrolling for several weeks, to return to base at anything other than regular cruising speed.

Weisia · 04-14-10, 04:55 AM

If I remember correctly the engine would overheat in SHII if you use flank speed to long. Seems quite logical to me that if you use a diesel in high RPM for a long period of time that the possibility of a break down increases.

Jimbuna · 04-14-10, 06:41 AM

Quote:

Originally Posted by HW3

I doubt they would have had enough fuel left, after patrolling for several weeks, to return to base at anything other than regular cruising speed.

Agreed....flank speed was only used for convoy interceptions and for as short a period as possible because of the wear and tear/maintenance issues it created.

sharkbit · 04-14-10, 07:44 AM

Quote:

Originally Posted by jimbuna

Agreed....flank speed was only used for convoy interceptions and for as short a period as possible because of the wear and tear/maintenance issues it created.

It sounds like those diesels could be maintenance nightmares.
I'm reading Clay Blair's "Hitler's U-Boat War:The Hunters" and it is filled with instances of boats aborting patrols due to engine problems.

rudewarrior · 04-14-10, 09:52 AM

Thanx for the responses. I've read some of the books mentioned here, specifically Iron Coffins (excellent book). Yeah, trucking across the Bay of Biscay later in the war was a real bitch, and I seem to remember reading somewhere that they would try to make it through the bay as quickly as possible. I remember reading that they would try to dive and surface at top speeds due to the "speed is life" idea. This minimizes the chances of them not being able to react to a situation that arises after the act of surfacing/diving. Since they are trying to react to aircraft buzzing around all over, I could see them trucking across the bay at top speeds as SOP. That would certainly minimize their dive time.

I know not to "cruise" at flank speed. Any mechanical engineer will tell you that is not what it is designed for. Flank speeds mean operating outside a normal range, and it would obviously only be done for a recommended period of time, which I can assure means no longer than a day, let alone the two weeks I need to get back.

I do recognize the engine breakdown argument. It's an obvious one, and it bears consideration, but I'd like to see some specifics about their return cited somewhere. The engines may break down, etc., but at the same time, from my own understanding of how militaries function, I also think there would be some impetus to return quickly. It is incredibly militarily inefficient to have a boat "taking its time" to get back. After all, that time is the period when the boat is most ineffective. It has no ordinance, with the exception of the deck and flak guns (for whatever that is worth). So essentially it is not a fighting capable unit, and it won't be UNTIL IT GETS HOME. Then it can be reoutfitted, and returned to sea to sink more shipping.

Having been in the military, I can't see taking a boat like that out, expending all of my ordinance, and then cruising back. It would seem that my superior would be screaming at me, "Get your ass back here, NOW!"

Again, the breakdown argument isn't necessarily wrong, it's just that the nature of these two arguments conflict enough such that I would really like to see some evidence supporting one or the other.

Maybe neither. Was fuel conservation an issue for the Kriegsmarine any time during the war? Just another issue to consider.

Capt. Morgan · 04-14-10, 10:11 AM

Quote:

Originally Posted by sharkbit

It sounds like those diesels could be maintenance nightmares.
I'm reading Clay Blair's "Hitler's U-Boat War:The Hunters" and it is filled with instances of boats aborting patrols due to engine problems.

Reminds me of that part in Robert McNamara's Fog of War where he talks about instituting the 50 mission limit for U.S.A.A.F. bomber crews in WWII.

The number of mission aborts due to engine failure dropped dramatically once the crews believed they had a chance of surviving the war (though statistically, their odds were no better than before).

Similarly, I'm sure that by late '42, many U-Boat commanders would use any opportunity, or excuse, to RTB early (and possibly at not so high speed).

sergei · 04-14-10, 10:52 AM

Quote:

Originally Posted by Capt. Morgan

Robert McNamara's Fog of War

I got that on DVD a few months back.
It's a very interesting film.

rudewarrior · 04-14-10, 04:16 PM

Quote:

Originally Posted by Capt. Morgan

Similarly, I'm sure that by late '42, many U-Boat commanders would use any opportunity, or excuse, to RTB early (and possibly at not so high speed).

Be more agressive.
-BdU

HW3 · 04-14-10, 07:25 PM

Many U-boats missions were ones where no targets were found or maybe just one. Their mission length was decided by the amount of food and fuel left. That is why u-tankers were used mainly for the resupply of food and fuel, and not so much for torpedoes.

04-13-10, 10:35 PM	#1
rudewarrior Sonar Guy Join Date: Apr 2005 Location: Middlebury, VT, USA Posts: 378 Downloads: 165 Uploads: 2	RTB speeds. Hi. Read quite a few books on the Atlantic War, but I didn't see anything on this particular subject. I'm curious about the speeds at which they returned to their bases. I assume that they would return at top speeds in order to get the weapons platform reoutfitted as quickly as possible, and back to fighting. However, would this cause engine issues? I never found any references to it in the books I have read so far. They only talk about having enough fuel "to get home." Yeah buddy, I know. But how fast? Thanx.

04-14-10, 01:31 AM	#3
brett25 Seasoned Skipper Join Date: Mar 2008 Location: Oakland CA, USA Posts: 737 Downloads: 570 Uploads: 0	i just finished reading Iron Coffins by Herbert Werner, you can read here that many of the u boat casualties later in the war were the U boats returning to their bases in the Bay of Biscay. The allies were waiting for them and the uboat's last leg home often became a turkey shoot for the allied aircraft. So depending on how you opted-either you returned slowly under water, undetected, or all out full throttle running the gauntlet. Either way your chances were not good, as, on average, only one out of every four boats would make it back. __________________ http://shmf.larsbundgaard.dk/index.p...1tn5&board=7.0 Last edited by brett25; 04-14-10 at 02:39 AM.

04-14-10, 02:49 AM	#4
HW3 Navy Seal Join Date: Apr 2005 Location: Gresham Oregon Posts: 6,574 Downloads: 458 Uploads: 0	I doubt they would have had enough fuel left, after patrolling for several weeks, to return to base at anything other than regular cruising speed. __________________ "Some ships are designed to sink...others require our assistance." Nathan Zelk

04-14-10, 07:25 PM	#12
HW3 Navy Seal Join Date: Apr 2005 Location: Gresham Oregon Posts: 6,574 Downloads: 458 Uploads: 0	Many U-boats missions were ones where no targets were found or maybe just one. Their mission length was decided by the amount of food and fuel left. That is why u-tankers were used mainly for the resupply of food and fuel, and not so much for torpedoes. __________________ "Some ships are designed to sink...others require our assistance." Nathan Zelk

04-13-10, 11:20 PM	#2
timmy41 Weps Join Date: Mar 2010 Posts: 367 Downloads: 9 Uploads: 0	considering the ranges at which they operated, I seriously doubt they could RTB at anything beyond cruising speed without having a bit to spare for bad weather and detours. Plus, all machines fail, especially ones that are used almost 24/7, and were built by rushed industry that may not have had all the proper tools available at times. There are not always spare parts available, so one does not want to risk any frivolous damage from running a machine too hard too long that may not allow them to get home at all. on top of all that and more, this is the 40s, and lots of these things were designed in the early 30s.

04-14-10, 04:55 AM	#5
Weisia A-ganger Join Date: Jan 2009 Posts: 71 Downloads: 65 Uploads: 0	If I remember correctly the engine would overheat in SHII if you use flank speed to long. Seems quite logical to me that if you use a diesel in high RPM for a long period of time that the possibility of a break down increases.

04-14-10, 09:52 AM	#8
rudewarrior Sonar Guy Join Date: Apr 2005 Location: Middlebury, VT, USA Posts: 378 Downloads: 165 Uploads: 2	Thanx for the responses. I've read some of the books mentioned here, specifically Iron Coffins (excellent book). Yeah, trucking across the Bay of Biscay later in the war was a real bitch, and I seem to remember reading somewhere that they would try to make it through the bay as quickly as possible. I remember reading that they would try to dive and surface at top speeds due to the "speed is life" idea. This minimizes the chances of them not being able to react to a situation that arises after the act of surfacing/diving. Since they are trying to react to aircraft buzzing around all over, I could see them trucking across the bay at top speeds as SOP. That would certainly minimize their dive time. I know not to "cruise" at flank speed. Any mechanical engineer will tell you that is not what it is designed for. Flank speeds mean operating outside a normal range, and it would obviously only be done for a recommended period of time, which I can assure means no longer than a day, let alone the two weeks I need to get back. I do recognize the engine breakdown argument. It's an obvious one, and it bears consideration, but I'd like to see some specifics about their return cited somewhere. The engines may break down, etc., but at the same time, from my own understanding of how militaries function, I also think there would be some impetus to return quickly. It is incredibly militarily inefficient to have a boat "taking its time" to get back. After all, that time is the period when the boat is most ineffective. It has no ordinance, with the exception of the deck and flak guns (for whatever that is worth). So essentially it is not a fighting capable unit, and it won't be UNTIL IT GETS HOME. Then it can be reoutfitted, and returned to sea to sink more shipping. Having been in the military, I can't see taking a boat like that out, expending all of my ordinance, and then cruising back. It would seem that my superior would be screaming at me, "Get your ass back here, NOW!" Again, the breakdown argument isn't necessarily wrong, it's just that the nature of these two arguments conflict enough such that I would really like to see some evidence supporting one or the other. Maybe neither. Was fuel conservation an issue for the Kriegsmarine any time during the war? Just another issue to consider.