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What if the Germans used u-boats as a supply vessels in Sealion

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  • #16
    Originally posted by michammer View Post
    The U-boats could never have kept an invasion force supplied - they simply could not carry enough. The 100 tons figure per u-boat is ludicrous. They may have been able to carry the weight, but that amount of supplies could never have been fitted into a u-boat. The idea of strapping them externally is also ridiculous. You now have to waterproof all the supplies, and the vessel would have become less streamlined meaning it would be slower and make more noise. A blind man with a hearing impediment could have located them and caught them in his row boat!!
    Ok, one by one:
    1) 100 tons figure is half of what the boat can theoretically carry (so I'm being conservative)
    2)The idea of strapping in not ridiculous - as a matter of fact it was considered and even planned for in project " Prüfstand XII " and that's the atlantic ocean and not just the channel.
    3) The supplies don't need themselves to be waterproof - they can be placed in a speciall external waterproof container.Besides part of the supplies will be liquid - engine fuel for instance - and can be pumped in and out.
    4) The subs will float normally close to the surface. We all know that there is a dead zone for the sonars several meters below the surface.
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    • #17
      what would a division need as far as supplies? per day?
      "Freedom cannot exist without discipline, self-discipline, and rights cannot exist without duties. Those who do not observe their duties do not deserve their rights."--Oriana Fallaci

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      • #18
        Originally posted by leopold View Post
        Exactly, if they did the results of the wargame might have been different.
        The British were planning for all eventualities, but they didn't think of using submarines. Why might that be? Might it be for the same reason they didn't plan on the Germans building a bridge?

        The average crossing distance of the channel is ~120km, the VIIB's surface speed is ~30km/h, let's say it is slowed down by the cargo to 20km/h, lets say it needs to get submerged third of the way to avoid unpleasant destroyer siluets - that is still less than 10 hour trip one way. Add 2 hours to unload (mind you that the cargo may be towed as you offered) that's a one trip per 24 hours. And I have used only half of the submarine fleet.(28 boats)
        Being on the surface in the Channel is a far, far different proposition to being on the surface in the North Atlantic. You've forgotten about the four hours taken to recharge batteries as well.

        Yeah right, the RN was quite often unable to find u-boats in the immediate surroundings of the allied convoys at that point - to speak about sweeping clear tens of thousands of square kilometers at that point is ridiculous.
        What's ridiculous is you suggesting that the U-Boats are going to be as safe in a 75,000 square kilometer body of water that's at it's most 120km deep as they are in the Atlantic ocean. Especially considering that the presence of indicator loops means that the British will be able to detect the submarines as soon as they near the cost.

        The u-boats were vulnerable if confronting warships directly - in such case the Channel is definetly dangerous for them.
        In case of them evading confrontation it's relatively safe - as proven by many cases of u-boats patrolling the channel with enormous Allied superiority.
        Allied anti-submarine assets are split throughout the war between protecting Britain and shepherding convoys. In the case of the invasion of Britain, everything would have been pulled back to help with it. Furthermore there's 21 U-Boats at the bottom of the Channel that would dispute your judgement that it's "relatively safe" there.

        Many of the human inventions were done by using something designed for one purpose in another context by adapting it.
        If you cannot accept the facts it only shows some type of internal limitation inside your brain hardware.
        What facts? You have speculation, nothing more. The 88 proved to be an effective anti-tank gun because it fired big shells at a high velocity. This was an example of a successful cross-over. U-Boats have nothing that would make them more effective than merchant ships in carrying cargo to supply an invasion.

        I watched 'Das Boot', and I thought : "these u-boats were tough." I also thought " These sailors sure knew how to improvise"
        Did you not also think, "Maybe I should continue to allow these U-Boats to do the job they're actually good at?"

        I also watched a documentary movie about project "Prüfstand XII" - I suggest you faimiliarize youself with it and keep in mind that the target was to cross the Atlantic and I am talking only about the channel.
        I know about "Prüfstand XII"- it's the product of absolute desperation. The fact that it takes them six months to build one 500 ton container should also suggest that the situation simply isn't practical, even in 1940 when the resource situation is slightly less strained.

        Again, these problems were addressed in "Prüfstand XII" and found manageble in much tougher situation of the atlantic.
        Did the Germans actually ever test the containers in the Atlantic? Or was it, perhaps, some sort of desperate suicide mission on a par with the manned V1s?

        So far, there were several hundred reads of my 2 threads, so the issue may be interesting to someone else even if you disagree.
        I have a feeling that people read these threads for the same reason they watch Plan Nine From Outer Space.
        Fere libenter homines id quod volunt credunt

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        • #19
          Originally posted by leopold View Post

          2) In addition to that it carries ~100 tons of fuel for 16000km range. but since it needs only less than 1000km for the cross channel trip that gives another ~90tons to spare.
          Oh come on. You can't use the fuel tanks to store anything other than diesel fuel. As far as I know the Heer doesn't have diesel powered vehicles in 1940. So the fuel tank idea is a complete and total wash.

          You could send all the boats back to port for a complete refit into supply vessels. However that will take months you don't have.

          You miss a significant point. Its not just mass but also volume that limits the amount of supplies a uboat will carry. The German army used a great deal of horses for its logistical effort (4000 horses were scheduled to be landed in the first wave of sealion). Horses eat hay. Hay is bulky. Fodder for the horses is a required German military supply. Artillery shells are shipped in bulky wooden crates. Food is bulky as well.

          Externally attached supplies is a very bad idea. By the time you waterproof the external containers for the depths required to escape the RN you have suffered a great expense for very little cargo space.

          Loading and unloading of supplies is still going to be your biggest problem. You won't have functioning ports and thus you can expect to spend a full day or more unloading.

          Furthermore, the Germans were planning to use the submarines to interdict the RN. Using the submarines as you suggest will just make the Royal Navy's job of utterly destroying the invasion easier.

          Basically the idea of using the submarine fleet for supply is an ineffiecient one.

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          • #20
            Originally posted by piero1971 View Post
            what would a division need as far as supplies? per day?
            According to Manstein the 22 divisions containing 250 000 troops of 6th army needed at least 550 tons of various supplies per day in order to operate in defence position.
            That is ~25 tons per day per division.

            So I assume that around 300 tons per division per day(ten times more) must suffice in offence operations
            that is 3000 tons per day for the assault force of ~80 000 (that was planned to be the invasion force of Sealion)
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            • #21
              Originally posted by robcraufurd View Post
              The British were planning for all eventualities, but they didn't think of using submarines. Why might that be? Might it be for the same reason they didn't plan on the Germans building a bridge?
              Are you asking me?!? Ask the British. You are there anyway...

              Originally posted by robcraufurd View Post
              Being on the surface in the Channel is a far, far different proposition to being on the surface in the North Atlantic. You've forgotten about the four hours taken to recharge batteries as well.
              And you have forgotten that while returning to France the submarines will not be carrying cargo. That compensates.

              Originally posted by robcraufurd View Post
              What's ridiculous is you suggesting that the U-Boats are going to be as safe in a 75,000 square kilometer body of water that's at it's most 120km deep as they are in the Atlantic ocean. Especially considering that the presence of indicator loops means that the British will be able to detect the submarines as soon as they near the cost.
              a) Submarines would be actually safer since they would not try to attack convoys or warships as they did in the atlantic.
              b) 120 m depth is sufficient for submerging and evading ,there were cases of submarines evading even in 30m deep sea.

              c) You don't seem to have a very clear idea of the indicator loops - those were placed as protection in port front entrances and the submarine was to try entering ENEMY port (not captured) in order to be detected by it.

              Originally posted by robcraufurd View Post
              Allied anti-submarine assets are split throughout the war between protecting Britain and shepherding convoys. In the case of the invasion of Britain, everything would have been pulled back to help with it. Furthermore there's 21 U-Boats at the bottom of the Channel that would dispute your judgement that it's "relatively safe" there.
              Most of those were sunk using radar technology that was not available at the point I of time I'm talking about.
              And yet there were successful u-boat patrols in the channel even in the 1944 when the allies had enormous advantages.

              Originally posted by robcraufurd View Post
              I know about "Prüfstand XII"- it's the product of absolute desperation. The fact that it takes them six months to build one 500 ton container should also suggest that the situation simply isn't practical, even in 1940 when the resource situation is slightly less strained.
              Ohh,so your logic goes like this:
              They took 4months 29 days to build the hull of the container and then made the manned starting platform inside it for V2 starting in the last day.
              Have you even looked at the picture of that container??? It had an operator room inside! I'm talking about the hull (and then only for 100 ton improvised version of it) Use your cognitive faculties for a change!


              Originally posted by robcraufurd View Post
              Did the Germans actually ever test the containers in the Atlantic? Or was it, perhaps, some sort of desperate suicide mission on a par with the manned V1s?
              No they didn't. The Russians however captured the plans and did the test successfully. But that's way off the point. I used it to prove to you that if the concept of sub towing 1500 tons submerged to the USA was viable option then towing 100 tons partially submerged through the channel is 100% possible.
              If you believe, you receive.
              If you doubt, you go without.

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              • #22
                Originally posted by AdrianE View Post
                Oh come on. You can't use the fuel tanks to store anything other than diesel fuel. As far as I know the Heer doesn't have diesel powered vehicles in 1940. So the fuel tank idea is a complete and total wash.
                .
                Actually the VIIB u-boat had 33 tons of external saddle tanks for extra fuel
                ,which could be easily isolated from the main tanks (by shutting some valve)and used for transporting fuel.
                However since the main way of transporting would have been by using a towed containers this would have been optional.

                Originally posted by AdrianE View Post
                You could send all the boats back to port for a complete refit into supply vessels. However that will take months you don't have.
                .
                They wouldn't need any serious refitting the amount of work will be no more than the usual servicing with some improvisations. The ~100 containers
                could be easily produced in the 2-3 months that germans had to prepare the invasion. Those would be a simple waterproof objects with no steering and no engine -just hulk and some big hatches for loading.

                Originally posted by AdrianE View Post
                You miss a significant point. Its not just mass but also volume that limits the amount of supplies a uboat will carry. The German army used a great deal of horses for its logistical effort (4000 horses were scheduled to be landed in the first wave of sealion). Horses eat hay. Hay is bulky. Fodder for the horses is a required German military supply. Artillery shells are shipped in bulky wooden crates. Food is bulky as well.
                As long as it can be placed in man movable boxes it can be transported in the above container.

                Originally posted by AdrianE View Post
                Externally attached supplies is a very bad idea. By the time you waterproof the external containers for the depths required to escape the RN you have suffered a great expense for very little cargo space.
                The whole idea is that if some destroyer starts to hunt the u-boat ,it releases the cargo and runs to safe depths.

                Originally posted by AdrianE View Post
                Loading and unloading of supplies is still going to be your biggest problem. You won't have functioning ports and thus you can expect to spend a full day or more unloading.
                The u-boat will bring the container to the port, detach from it and attach to an empty one. No long staying in the port. The unloading may proceed after the sub starts swimming back.

                Originally posted by AdrianE View Post
                Furthermore, the Germans were planning to use the submarines to interdict the RN. Using the submarines as you suggest will just make the Royal Navy's job of utterly destroying the invasion easier.
                Are you suggesting the RN bombarding the landed forces? Such bombardment cannot 'utterly destroy' the invasion. Besides - the idea of the invasion is to quickly advance inland and there the RN cannot bombard.
                Originally posted by AdrianE View Post
                Basically the idea of using the submarine fleet for supply is an ineffiecient one
                Compared to what? Sinked merchant ships?
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                If you doubt, you go without.

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                • #23
                  Originally posted by leopold View Post
                  What if after the first wave of German landings of Sealion, which according to war game experiments could have succeeded were followed by the Germans taking some ports and then using part of their U-boat fleet to provide supplies for the troops?
                  It would have been a complete and total waste of an important weapons system. The same thing was tried during the Japanese siege of Bataan and Corregidor in 1942 and it was found to be an abysmaal failure.

                  You would be better off using the U-Boats as floating ponts for a pontoon bridge across the channel.
                  "Profanity is but a linguistic crutch for illiterate motherbleepers"

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                  • #24
                    Originally posted by leopold View Post
                    Ok, one by one:
                    1) 100 tons figure is half of what the boat can theoretically carry (so I'm being conservative)
                    I am not disputing the 100 tons figure, I am saying you would not get 100 tons of supplies INSIDE the u-boat.


                    2)The idea of strapping in not ridiculous - as a matter of fact it was considered and even planned for in project " Prüfstand XII " and that's the atlantic ocean and not just the channel.
                    Being considered and planned for are totally different to actually being carried out.

                    3) The supplies don't need themselves to be waterproof - they can be placed in a speciall external waterproof container.Besides part of the supplies will be liquid - engine fuel for instance - and can be pumped in and out.
                    You still have to build the waterproof containers. And if you are going to drop them off and then return - you are going to need a lot.

                    What would the fuel be pumped in and out of? You are not going to pump gasoline into tanks that are normally used for diesel. Also, how are you going to pump it out at the other end? Would that not mean the u-boat would have to sit around at the British coastline while it was pumped out? So much for dropping off and running back to France.


                    4) The subs will float normally close to the surface. We all know that there is a dead zone for the sonars several meters below the surface.
                    So they will be visible then.

                    If a division needs 300 tons per day, and the invasion force 3000 tons per day, you will need more than u-boats to supply them. Relying on just u-boats will see your army starving in a few days.

                    It would be a more efficient use of resources to use the u-boats to screen the entrances to the channel and use freighters to move the supplies across the channel.

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                    • #25
                      Originally posted by johnbryan View Post
                      It would have been a complete and total waste of an important weapons system. The same thing was tried during the Japanese siege of Bataan and Corregidor in 1942 and it was found to be an abysmaal failure.
                      .
                      U.S. submarines delivered 331 people, evacuated 472, and delivered some 1,325 tons of supplies to the Philippines
                      - where exactly is the 'abysmall' failure in that?!
                      Also the distances, over which those were delivered were incomparably higher than those of the channel

                      Originally posted by johnbryan View Post
                      You would be better off using the U-Boats as floating ponts for a pontoon bridge across the channel.
                      If you are full of such great ideas, why don't you start your own thread?
                      If you believe, you receive.
                      If you doubt, you go without.

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                      • #26
                        Originally posted by michammer View Post
                        I am not disputing the 100 tons figure, I am saying you would not get 100 tons of supplies INSIDE the u-boat.

                        .
                        Placing supplies inside will be optional. In addition to the container.

                        Originally posted by michammer View Post
                        Being considered and planned for are totally different to actually being carried out.
                        .
                        Ok,it WAS carried out. They didn't actually fire the rocket from that container ,but that's irrelevant and the russians successfully tested it afterwards anyway.

                        Originally posted by michammer View Post
                        You still have to build the waterproof containers. And if you are going to drop them off and then return - you are going to need a lot.
                        .
                        True, but nothing the germany engineers couldn't handle in 2-3 months.

                        Originally posted by michammer View Post
                        What would the fuel be pumped in and out of? You are not going to pump gasoline into tanks that are normally used for diesel. Also, how are you going to pump it out at the other end? Would that not mean the u-boat would have to sit around at the British coastline while it was pumped out? So much for dropping off and running back to France.
                        I said it's optional -as an addition to the usual load.

                        Originally posted by michammer View Post
                        So they will be visible then.
                        No they wouldn't . They'll be still under water. Visible from a plain passing directly above low enough doesn't count.

                        Originally posted by michammer View Post
                        If a division needs 300 tons per day, and the invasion force 3000 tons per day, you will need more than u-boats to supply them. Relying on just u-boats will see your army starving in a few days.
                        Look at my calculations above.

                        Originally posted by michammer View Post
                        It would be a more efficient use of resources to use the u-boats to screen the entrances to the channel and use freighters to move the supplies across the channel.
                        Not according to the wargames RMA did.
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                        If you doubt, you go without.

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                        • #27
                          Checking the actual weight of cargo carried by US and Japanese submarines in the Pacific would be usefull. In many of those cases there was preperation of the submarine for carrying the cargo, so seperation of the unperpared emergency missions from well prepared missions would be usefull for accurate comparrison. Equally important would be the time requirements for unloading, with & without proper docks. The number given for the US submarine deliverys are not much use without knowing the number & type of submarine, and related details.

                          The real vulnerability of the submarines would be unloading on the far shore, and to a leser extent on the near shore when loading. By loading here I am including the surfaced approach and departure from the harbors. On the far or British shore the landing areas would be horribly vulnerable to air attacks. The Wehrmacht landing force cant afford to trade off offensive weapons/fire power for anti air weapons, which leaves the burden on the Luftwaffe. weakening the German air defense is the lack of any practical air attack warning system. Typically there would be just a few minutes of warning, and often none.

                          There are also some questions about navigating submarines through the roadsteads & channels approaching the harbors. I'd guess most are too narrow & shallow for submerged navigation. Particularly for the high speed supply runs postulared for this thread. The complexities of keeping the dozens of small transports sorted approaching landfall is easy to underestimate. Having submarines diving & surfacing amoungst this would certainly make it more interesting.
                          Last edited by Carl Schwamberg; 18 Nov 06, 09:04.

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                          • #28
                            Originally posted by leopold
                            Ok,it WAS carried out. They didn't actually fire the rocket from that container ,but that's irrelevant and the russians successfully tested it afterwards anyway.
                            Originally posted by leopold
                            No they didn't. The Russians however captured the plans and did the test successfully. But that's way off the point. I used it to prove to you that if the concept of sub towing 1500 tons submerged to the USA was viable option then towing 100 tons partially submerged through the channel is 100% possible.
                            Ok, so was it carried out or not? Just because an option is viable on paper does not mean it is viable in actuality.

                            Originally posted by leopold
                            No they wouldn't . They'll be still under water. Visible from a plain passing directly above low enough doesn't count.
                            Yes it does. If they can be seen, they can be seen.


                            Look at my calculations above.
                            I did. You still have not convinced me that the u-boats would be able to provide enough.



                            Not according to the wargames RMA did.
                            So the RMA carried out wargames using u-boats to supply the landing did they? Source?

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                            • #29
                              Originally posted by michammer View Post
                              Ok, so was it carried out or not? Just because an option is viable on paper does not mean it is viable in actuality.
                              They did create 1 towed container for the V2 launching, but didn't actually fire the rocket from it becouse there were higher priorities at that point.
                              Russians captured the plans and successfully did the whole test including the rocket launch.

                              Originally posted by michammer View Post
                              Yes it does. If they can be seen, they can be seen.
                              No it doesn't. Finding a submerged submarine from a plane in an open sea is literally like finding a needle in a haystack. That is so becouse of the reflection properties of the water.


                              Originally posted by michammer View Post
                              I did. You still have not convinced me that the u-boats would be able to provide enough.
                              Tell me what part of the calculation you disagree with so I can address it..



                              Originally posted by michammer View Post
                              So the RMA carried out wargames using u-boats to supply the landing did they? Source?
                              RMA didn't use u-boats, but only merchant ships in the wargame and concluded that this would have led to defeat and surrnder for the german invasion force.
                              If you believe, you receive.
                              If you doubt, you go without.

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                              • #30
                                Originally posted by Carl Schwamberg View Post
                                Checking the actual weight of cargo carried by US and Japanese submarines in the Pacific would be usefull. In many of those cases there was preperation of the submarine for carrying the cargo, so seperation of the unperpared emergency missions from well prepared missions would be usefull for accurate comparrison. Equally important would be the time requirements for unloading, with & without proper docks. The number given for the US submarine deliverys are not much use without knowing the number & type of submarine, and related details.

                                The real vulnerability of the submarines would be unloading on the far shore, and to a leser extent on the near shore when loading. By loading here I am including the surfaced approach and departure from the harbors. On the far or British shore the landing areas would be horribly vulnerable to air attacks. The Wehrmacht landing force cant afford to trade off offensive weapons/fire power for anti air weapons, which leaves the burden on the Luftwaffe. weakening the German air defense is the lack of any practical air attack warning system. Typically there would be just a few minutes of warning, and often none.

                                There are also some questions about navigating submarines through the roadsteads & channels approaching the harbors. I'd guess most are too narrow & shallow for submerged navigation. Particularly for the high speed supply runs postulared for this thread. The complexities of keeping the dozens of small transports sorted approaching landfall is easy to underestimate. Having submarines diving & surfacing amoungst this would certainly make it more interesting.
                                You raise a lot of detailed questions. I will try to answer them but that will need some research. However here are some points that address the unloading issue. -
                                a) Since the subs are invisible until they get close to the destination the RAF bombers will also have some limitation on the alert time - assuming that british intelligence immediately detects any sub bringing cargo ,which by itseld is not necessarily a fact. Since the bombers's bases may be pushed north by the LW those factors can bring breathing space to the unloading.

                                b) Since in my proposal the subs use towed containers they need not stay in port and wait for the actual unload to finish. They would leave full container and take back an empty one if there is such.

                                c) The subs can bring cargo containers directly to shores in predetermined random points. From there the cargo containers can be unloaded by small boats under the cover of smoke further complicating the RAF attacks.

                                d) From the reaction of people on this forum one can conclude that the british would not consider u-boat transports a serious threat. This coupled with a concurent effort to pass supplies in the usual way (through merchant ships) would have focused all the RN effort against the conventional supply targets while the u-boats quietly do their work.
                                If you believe, you receive.
                                If you doubt, you go without.

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