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

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  • Originally posted by The Purist View Post
    Do you realize what even STD schedule pipe weighs per foot?. You do not just "smash" metal pipe together it has to be "tapered" and forged that way. The other end then need a flange welded to the end and a blind bolted to it about 1000 lbs in weight. The 65' of pipe will need to be welded together from three 20' pieces and then the whole thing needs to be hydro-tested to see if the welds leak at various pressures.

    Here is the specs for "STD" pipe, 38" diameter:
    wall thickness - 0.375"
    weight per foot - 150.69 lbs or 224.26 kg per metre.

    20 meters (65') of pipe would weigh:

    9800 lbs or just under 5 tons.
    4485.2 kg or about 4.5 metric tonnes.

    It's weight per volume far exceeds its diplacement capacity so this cylinder will simply,...sink.
    Neutral bouyancy with this design is not possible.
    First of all, thanks for the data.

    However either you have some basic misunderstanding of the Archimed's law
    or maybe I don't understand your calculations :

    38'' = 98 sm => 1mx20m pipe will have a 15.7 cubic meter displacement ~ 15.7 tons of water - therefore with 4.5 ton weigth it will have ~11 ton carrying capacity up to the neutral bouyancy.
    As to the smashing - I was just speaking figuratively, my point being that there isn't that much of a 'design'.
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    • Originally posted by robcraufurd View Post

      And rip out his bottom on any rocks that might be there: Type IIs, after all, don't have any watertight compartments. Of course, since it's so shallow, at least his crew might survive. You've also just restricted your timings even more: as soon as the British have word from the French Resistance that the Germans are using U-Boats as supply vessels, and the first reconnaissance plane notices Germans unloading cargo in this way, they'll be able to predict with startling accuracy when the U-Boats will be present.

      Completely undetectable? You're putting lights on both sides of the Channel, lights which will have to be distinguishable from ordinary lights through a periscope from some distance. May as well hoist a giant flag saying "Cargo being dropped here, please don't investigate."
      Ok, I admit I was tempted by the elegance of using the tide.
      There is another idea I am weighting for a while and it goes like this:
      After the u-boat approaches the english side it may send a torpedo (with no warhead) dragging an unwinding roll of rope to the shore.
      Considering the range and power of the G7a torpedo that would be well within it's ability.
      While such solution would be somewhat expensive (torpedoes aren't cheap), it could be very time saving if the british ASWs are patrolling closely.

      Originally posted by robcraufurd View Post

      The British estimate the position of the submarine and use depth-charges, hoping either to score a lucky hit or force the submarine into fleeing. If you're planning on stopping every time the British detect you, however, considering that the detection range of ASDIC is 2km, you're not going to go very far.



      Well, since the range of the Type II is about 70km submerged, and the speed drops to 4 knots, it means you're going to double the time of your trip and vastly increase the time spent refilling air tanks and recharging batteries. If you only submerge when you see something that could be an ASW vessel, you run the risk of being shelled- if not by the British, then by stray German artillery shots.
      While the ASDIC works up to 2km it's of no use when the sub is on the surface or at periscope level immediately under the surface. It also wouldn't be much use when the sub is very close to the bottom.
      So in order for the ASWs to use the asdic they'll have to ask politely from the u-boat commanders to hover at least several meter below the surface , but not too deep ...
      The only left detector will be the hydrophones. However using them, while shells explode around is like listening to Mozart in a room full of Hill Bilies raping squealing pigs. - The atlantic convoy ASWs didn't suffer from such distractions and even then they weren't very successful to begin with.

      Since the u-boats will run mostly during the night they'll have the whole day to reload their batteries.
      The risk of being shelled at night depends on the weather:
      a) Bigger waves - the u-boat's low profile is very difficult target to acquire since they constantly dissapear between waves and it's dark anyway.
      b) Calm flat sea - the u-boat can show only 2 meter of it's sail and still run on diesels - such object is very small and dificult to see at night
      Considering the difference in size the u-boat will always be the first to see and the last to be seen and that's even before they get to periscope level.

      The risk of getting hit by astray friendly fire is too low to be significant.

      I'm trying to imagine how it all could have worked out ..night time ...there'll be a lots of british ships running like wild in circles throught the channel and depth charging the hell out of the bottom rocks, while having no idea where the subs actually are.
      Meanwhile the german naval guns from the french side (Calais area) would have a nice uninterrupted target practice. (getting some appreciated assistance from the German naval radar and some LW stukas)

      From time to time , RAF bombers appear over the channel looping around dropping flares ... still no luck - by the time the third flare starts glowing all subs are hidden below the surface. Meanwhile some 88 AA starts to experiment with the bomber shadows comming too close to the french side. As the bombers start heading back home the sound of a Me109 whirling above is heard - will it manage to catch them?
      If you believe, you receive.
      If you doubt, you go without.

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      • Originally posted by leopold View Post
        b) Calm flat sea - the u-boat can show only 2 meter of it's sail and still run on diesels - such object is very small and dificult to see at night
        Considering the difference in size the u-boat will always be the first to see and the last to be seen and that's even before they get to periscope level.
        U-boats Had Sails?????

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        • Originally posted by leopold View Post
          Ok, I admit I was tempted by the elegance of using the tide.
          There is another idea I am weighting for a while and it goes like this:
          After the u-boat approaches the english side it may send a torpedo (with no warhead) dragging an unwinding roll of rope to the shore.
          Considering the range and power of the G7a torpedo that would be well within it's ability.
          While such solution would be somewhat expensive (torpedoes aren't cheap), it could be very time saving if the british ASWs are patrolling closely.
          The trouble is that you're now going to force the PBI to scour the beach looking for said torpedo, which could run aground anywhere- including below the low tide mark. I hate endlessly recounting Spike Milligan stories, but if you've read Adolf Hitler: My Part in His Downfall you're undoubtedly recalling the one about the search for the 9.2 shell.

          While the ASDIC works up to 2km it's of no use when the sub is on the surface or at periscope level immediately under the surface. It also wouldn't be much use when the sub is very close to the bottom.
          If the sub's on the surface, it can be spotted from around 6 miles away by Coastal Command. If it's just under the surface, or very close to the bottom, it's using up air and battery supplies.

          Meanwhile the german naval guns from the french side (Calais area) would have a nice uninterrupted target practice. (getting some appreciated assistance from the German naval radar and some LW stukas)
          In 1940, the Luftwaffe Stukas are acting as close support for the army. They don't start to gain any sort of efficiency in anti-ship actions until 1941, in the Mediterranean. Moreover, the Luftwaffe don't actually have any armour-piercing bombs that would allow them to do real damage to capital ships. As for the naval guns, while they might enjoy target practice they'll have a hell of a job hitting a destroyer moving at 30 knots from 20 miles away.

          I'm trying to imagine how it all could have worked out
          Here, let me give you a hand. As night falls, a Type II U-Boat sets out from its base at Boulogne. It was to have been part of a three-vessel convoy, but an attack by British bombers crippled one boat, while the second had been unable to refuel because a vital consignment of diesel was sabotaged in transit. At first she makes good time, but a Coastal Command reconnaissance plane picks her up on radar and she is forced to lie on the bottom for an hour to enable a British destroyer patrol to pass. Finally, she nears the coast: however, the action of the tide on the cargo she carries has pushed her off course, and instead of arriving at Folkestone, where the men of the 10th Panzer division are awaiting a consignment of tank shells and spare parts, she in fact arrives at Dover, where the 29th Infantry division are waiting for shells for their 35mm PaKs and more rifle ammunition. She fires her torpedo, which buries itself in the sandy shore around a mile out to sea, then detaches her cargo and heads for home in the satisfaction of a job well done.

          Unfortunately, on her return, she runs into another destroyer patrol. She goes to ground on the sea-bed, whereupon the British drop depth-charges in the rough area where she was last spotted. A close explosion punctures her hull, and she is lost with all hands. The Luftwaffe, currently battling the RAF for control of the air, divert a flight of Stukas from a bombing raid on the 45th Division to attack the ships, but the RAF- who cracked Luftwaffe W/T codes in July 1940- dispatch a couple of fighters who catch and down the Germans over the Channel.

          Sound about right to anybody else?
          Fere libenter homines id quod volunt credunt

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          • Originally posted by Duke William View Post
            U-boats Had Sails?????
            Sail is called the tower-like structure found on the topside surface of submarines. Sometimes it's called 'fin'. I suppose like the fin of the fish.
            If you believe, you receive.
            If you doubt, you go without.

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            • Originally posted by robcraufurd View Post
              The trouble is that you're now going to force the PBI to scour the beach looking for said torpedo, which could run aground anywhere- including below the low tide mark.
              Since torpedo is without warhead it runs strictly on the surface, if sent during high tide it will be lying on a empty beach during low tide - easily detectable by the surface party - besides the surfice party will know where to look for it. Also such torpedo may have diver attached (like the italians did their sub sabotage actions)
              Still that was just an improvement idea - a 'nice to have' if you will.

              Originally posted by robcraufurd View Post
              If the sub's on the surface, it can be spotted from around 6 miles away by Coastal Command. If it's just under the surface, or very close to the bottom, it's using up air and battery supplies.
              As I previously stated the subs could be dived ~1/3 of the way - obviously closer to the english beaches is more suitable.
              However if by coastal command you mean coast based observed - I have to dissapoint you - they would be overrun by the invaders...

              Originally posted by robcraufurd View Post
              In 1940, the Luftwaffe Stukas are acting as close support for the army. They don't start to gain any sort of efficiency in anti-ship actions until 1941, in the Mediterranean. Moreover, the Luftwaffe don't actually have any armour-piercing bombs that would allow them to do real damage to capital ships. As for the naval guns, while they might enjoy target practice they'll have a hell of a job hitting a destroyer moving at 30 knots from 20 miles away.
              Hmmm,so who sunk 4 british and 1 french destroyers and damaged another 19
              + sunk 6 additional ships and 200 smaller craft in a week?

              As for the naval guns - if the destroyer's move at speed more than 15 knots their asdics would be usless (not that they would be much use otherwise) and if they are imediately close to english cost there's not much of a depth charging area they can cover.

              Originally posted by robcraufurd View Post
              Here, let me give you a hand. As night falls, a Type II U-Boat sets out from its base at Boulogne. It was to have been part of a three-vessel convoy, but an attack by British bombers crippled one boat, while the second had been unable to refuel because a vital consignment of diesel was sabotaged in transit. At first she makes good time, but a Coastal Command reconnaissance plane picks her up on radar and she is forced to lie on the bottom for an hour to enable a British destroyer patrol to pass. Finally, she nears the coast: however, the action of the tide on the cargo she carries has pushed her off course, and instead of arriving at Folkestone, where the men of the 10th Panzer division are awaiting a consignment of tank shells and spare parts, she in fact arrives at Dover, where the 29th Infantry division are waiting for shells for their 35mm PaKs and more rifle ammunition. She fires her torpedo, which buries itself in the sandy shore around a mile out to sea, then detaches her cargo and heads for home in the satisfaction of a job well done.

              Unfortunately, on her return, she runs into another destroyer patrol. She goes to ground on the sea-bed, whereupon the British drop depth-charges in the rough area where she was last spotted. A close explosion punctures her hull, and she is lost with all hands.
              Hehe Well now, this boat will really really have to make an effort to be detected by night by a english airborn radar when the first successful night radar detection of sub was at 21 December 1941 . Maybe the captain has some british relatives?
              Also a little advice - if the sub gets detected in the channel it simply can submerge to periscope level - immediately under the surface and start evasing maneuvers getting closer to the french shore artillery cover - the destroyer being constantly shelled will be unable to use it's hydrophones so to damage it it's only chance would be to ram it by chance - highly unlikely.
              I have a feeling that under constant radar assisted shelling + some air bombing the destroyer fleet will soon have 2 choices:
              1) Get out of the Dover straits
              2) Settle down under Dover straits
              If you believe, you receive.
              If you doubt, you go without.

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              • "....getting closer to the french shore artillery cover - the destroyer being constantly shelled will be unable to use it's hydrophones so to damage it it's only chance would be to ram it by chance - highly unlikely.
                I have a feeling that under constant radar assisted shelling... "

                Once again we have a grossly exagerated expectation of what artillery might do...

                Anyone have a refrence for the ability of radar to assist artillery in 1940? Specificly in German hands? After that we can calculate how many batterys it would take to line the coast and how many radar sets for this task.

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                • Any games that model Sea Lion in a remotely valid way? Have been picking thru the site refered to above for the Sanhurst game & am curious about how any other game designers have treated it.

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                  • Originally posted by leopold View Post
                    First of all, thanks for the data.

                    However either you have some basic misunderstanding of the Archimed's law
                    or maybe I don't understand your calculations :

                    38'' = 98 sm => 1mx20m pipe will have a 15.7 cubic meter displacement ~ 15.7 tons of water - therefore with 4.5 ton weigth it will have ~11 ton carrying capacity up to the neutral bouyancy.
                    I understand the principle but can definitely tell you such a pipe, sealed and filled with only air will sink like a stone. I've seen it more than once in the oil industry when running pipe into the Gulf of Mexico or the North Sea. It would require significant floatation devices to keep it near the surface and any cargo would only require more floats.
                    The Purist

                    Words ought to be a little wild, for they are the assault of thoughts on the unthinking - John Maynard Keynes.

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                    • Originally posted by The Purist View Post
                      I understand the principle but can definitely tell you such a pipe, sealed and filled with only air will sink like a stone. I've seen it more than once in the oil industry when running pipe into the Gulf of Mexico or the North Sea. It would require significant floatation devices to keep it near the surface and any cargo would only require more floats.
                      Oh, come on!
                      We have to respect at least the most basic laws of physics in our virtual 'what ifs' - otherwise it becomes like 'Alice in wonderland'.
                      As to the oil industry, I presume you refer to the pipes that lie on the bottom of the sea for oil transportation - those pipes are constructed to withstand tens of atmospheres of pressure therefore their thicknes is several centimeters ...
                      You on the other hand were talking about less than 1 atmosphere and respectively ~ 0.7 sm...
                      If you believe, you receive.
                      If you doubt, you go without.

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                      • Originally posted by The Purist View Post
                        I understand the principle but can definitely tell you such a pipe, sealed and filled with only air will sink like a stone. I've seen it more than once in the oil industry when running pipe into the Gulf of Mexico or the North Sea. It would require significant floatation devices to keep it near the surface and any cargo would only require more floats.
                        ....continued ... Those oil pipes also appear to have a heavy coating, to protect them from years of aggresive sea water erosion on the seabed. The coating alone would be enough to sink them.
                        If you believe, you receive.
                        If you doubt, you go without.

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                        • Additional though I had - how difficult would be for the RN and RAF to catch S-Boat crossing the channel at night?
                          How many lightly armed troops would be realistic for S-Boat to carry.
                          I was thinking around ~50. Any suggestions?
                          If you believe, you receive.
                          If you doubt, you go without.

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                          • The US used the oversized Nautalus & its sisters for commando raids. They were hard pressed to accomodate sixty men & weapons. The monster Sucrof was able to carry a fair number more.

                            "Additional though I had - how difficult would be for the RN and RAF to catch S-Boat crossing the channel at night? "

                            In the 1939-40 period they caught them at dawn trying to get themselves off the shoals where they ran aground.
                            Last edited by Carl Schwamberg; 01 Dec 06, 07:08.

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                            • Originally posted by leopold View Post
                              Since torpedo is without warhead it runs strictly on the surface, if sent during high tide it will be lying on a empty beach during low tide - easily detectable by the surface party - besides the surfice party will know where to look for it. Also such torpedo may have diver attached (like the italians did their sub sabotage actions)
                              Still that was just an improvement idea - a 'nice to have' if you will.
                              It might be nice to have, were there a way of attaching a cable to the torpedo. You can only attach it before the torpedo's fired, so you have two choices: take the cable up through the sub to fix it to the cargo, in which case you've just neatly tied the sub into the chain, or have someone crawl out through the torpedo tube and clamber across the sub's hull. In either case, the torpedo will probably just float off the beach as the tide goes out, and the Germans will be left searching for nothing. As for manned torpedoes, I suspect they may well be slightly different to the torpedoes U-Boats were made to fire.

                              As I previously stated the subs could be dived ~1/3 of the way - obviously closer to the english beaches is more suitable.
                              However if by coastal command you mean coast based observed - I have to dissapoint you - they would be overrun by the invaders...
                              Like I said, Coastal Command.

                              Hmmm,so who sunk 4 british and 1 french destroyers and damaged another 19
                              + sunk 6 additional ships and 200 smaller craft in a week?
                              Wow, that's a real achievement. Oh, wait. How many of those ships sunk are close to the shore, without room to manoeuvre? In fact, aren't all these ships busy supporting an evacuation?

                              Hehe Well now, this boat will really really have to make an effort to be detected by night by a english airborn radar when the first successful night radar detection of sub was at 21 December 1941 . Maybe the captain has some british relatives?
                              No, the first successful night ATTACK is on the 21st. Detecting them's not a problem, but since the radar doesn't work within a few miles of the target, spotting them once you're close in is much harder. Of course, when you've got destroyer patrols within such close proximity, Coastal Command can just pass the information they gather on to the Royal Navy.

                              Also a little advice - if the sub gets detected in the channel it simply can submerge to periscope level - immediately under the surface and start evasing maneuvers getting closer to the french shore artillery cover - the destroyer being constantly shelled will be unable to use it's hydrophones so to damage it it's only chance would be to ram it by chance - highly unlikely.
                              This sub is presumably within visual range, since you think ASDIC is useless. Do you think visual range for spotting the sub is greater than the margin of error for the naval guns or German artillery? If the sub's heading for the French coast, you better hope that the coastal artillery doesn't under-shoot, since an 1800lb projectile could really ruin a U-boat's day.

                              I have a feeling that under constant radar assisted shelling + some air bombing the destroyer fleet will soon have 2 choices:
                              1) Get out of the Dover straits
                              2) Settle down under Dover straits
                              What air bombing? Seriously, where are all these spare planes coming from? Are the Italians supplying them, as well as all their submarines? By the way, precisely how effective is the British coastal artillery against the Scharnhorst and Gneisenau- much larger targets, travelling at similar speeds?
                              Fere libenter homines id quod volunt credunt

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                              • Originally posted by Carl Schwamberg View Post
                                Any games that model Sea Lion in a remotely valid way? Have been picking thru the site refered to above for the Sanhurst game & am curious about how any other game designers have treated it.
                                Indirectly. Try navigating the Straits of Dover in a U-Boat playing Silent Hunter III. It's quite nail biting. As for hovering just below the surface, a Destroyer/PT Boat combination is quite effective at forcing a sub below the surface, where ASIC will pick it up. It's a tough situation, engage the PT boat (traveling 30+ knots)on the surface or take you chances with the Destroyer submerged. Given that the Straights are around 25-30 meter deep it doesn't give you a whole lot of room to play with and everytime you check your depth below keel it's like sounding a siren.
                                Last edited by Freightshaker; 01 Dec 06, 17:33.
                                If you can't set a good example, be a glaring warning.

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