WWII Stealth Coatings on German U-Boats

To reduce the German's WWII submarines visual and radar cross section, snorkel were retrofitted to the existing U-boats. The schnorchel allowed U-boats to remain submerged somewhat indefinitely. They also reduce the radar cross-section by about 1/3 of a surfaced U-boat. The German's also applied radar absorbing (Stealth) materials to the schnorkels to further reduce the radar returns by application of the stealth coatings. Unfortunately, these efforts came too late in the war to effect the battle of the Atlantic. This is a part 11 of a multipart video series addressing the contributions of the US bombers during the WWII Battle of the Atlantic.

[@nate6692]

I can't help but think that breaking enigma is the overriding factor here and possibly obscures the effectiveness the snorkel itself would've had without that setback.

[@giantidiot31]

I don't know much about Enigma itself. But I do know about the tactics and strategies used by the navy from the ~60s on. And even once you enter the era of the stealth combustion and early nuclear, a lot of the tactics stay the same. It's just the timescales and complexity that are different. During the Cold War, America would listen in on/intercept Soviet transmissions. For their sub command, they were harder to act on because their orders were much more broad and obviously harder to track. A surface fleet would get a pretty specific departure window, which made them easy to follow. Plus you would notice they'd left port anyway. Soviet subs were given broader departure windows and were almost impossible to follow once they leave port. But the orders still contained lat-longs or well charted AOs. And that was usually enough to keep tabs on at least a few of their subs

[@torarildhenriksen371]

By using the schnorkel german uboats became almost radio silent, and at the end of the war they introduced a highspeed radio that made it impossible to pick up german radio transmissions. Bletchy park got less material to work with at the end of the war

[@bertbert594]

@@torarildhenriksen371 > highspeed radio that made it impossible to pick up german radio transmissions can you elaborate on that?

[@roberthutchins1507]

I can personally attest that it was easier to see periscopes and snorkels than pick them up on radar, especially during low sea states. Mostly what was visible was the wake caused by whatever was sticking up out of the water. This never really changed until the introduction of the APS 137 radar on P-3's.

[@Whiteyy191]

You’re a WW2 veteran?

[@roberthutchins1507]

@@Whiteyy191 No, I retired from the Navy in 2000

[@gctzx]

Love this channel. Who else is always pressing Pause to read the reports?

[@hummingbird9149]

Should be noted that the ratio of U-boats to merchant vessels lost is a bit misleading as to the effect of the radar absorbing coatings. For example from June 1944 the Uboats were also starting to sink more of the now very numerous Allied AS warships out there hunting them (naturally as they bumped into more). In total however from Jan 1944 to May 1945 German Uboats hit 341 Allied vessels (the majority total losses), for the loss of 326 U-boats at sea, of which 31 were lost to mines. So they were still achieving a better than 1:1 ratio at sea, just not vs merchant shipping, which after all was what really mattered. Also worthy of note, after December 44 where the coatings became more prominent, losses to aircraft actually fell in ratio as compared to mines and warships.

[@mungo7136]

Well, trading 1 Uboat to 1 (or even 1.1) anything means, Uboats are on the loosing side. And when it comes to aircraft, it is not just about destroyed subs. Forcing them underwater to max. 6 knots means, that now they are roughly at merchant ship speed and cannot chase them and it is harder to get into good firing position. Also detecting ship through periscope is less effective than from coning tower with binoculars through the ayes of the several men at the same time.

[@hummingbird9149]

@@mungo7136 Not denying that they were losing, as I wrote sinking merchant vessels was the prime reason the subs were out there. I just wanted to add some context to the Uboat to merchant vessel loss rate. That said, the main factor behind them losing wasn't the AS warships and aircraft themselves, but the fact that the German naval communication code had been broken, allowing the aforementioned assets to be deployed at exactly the right areas at the right time for when the German uboats were going to be around there.

[@mungo7136]

@@hummingbird9149 to have to some extent knowledge of their area of operation increased efficiency once again to some extent - but as had been proven before - when you have not those assets in numbers, even that knowledge is not that useful. At the same time - it is quite clear that subs would operate on ships' routes and around convoys. Thus once the forces were available in numbers, those were protected. And it even allowed for free hunt outside those critical spots. While aircraft cover forced subs under the surface, slowed them down, made transition to trade routes much harder and riskier - and even less effective.

[@hummingbird9149]

@@mungo7136 The atlantic ocean is a very big place, thus there was never going to be enough forces to cover all merchants for the entire route, esp. as the number of merchants operating also significantly increased in the latter part of the war. Hence the importance of breaking the German naval code, it allowed the Allies to preemptively choose where to concentrate their AS assets in order to maximize their chances of finding the subs before they could even get to the merchants. Yes the much larger number of AS assets by the end of the war definitely made the chances of finding uboats larger by itself, that's a given, but it was the breaking of the enigma that truly turned the tide for good.

[@williamzk9083]

@@hummingbird9149 Even that could have ended. The Germans had UKW-D which was a rewindable reflector for enigma (I think first seen in 1942) for and a another devices which steped the reflector pseudo radomely. They both would have sent Blechely Park Blind. Fortunately the for the allies the Germans were so stressed for resources they didn't deploy them widely. -There was also the Kurrier-Engima system which sent a 54 character message in burst mode hard to direction find. It was hard to intercept but once intercepted was a little easier to decode due to the structured 54 character burst. In the 3F mode kurier transmited on a SSBSC (single side band suppressed carrier) with dots and dashes alternatively on different frequencies and of course no carrier for the space in between to Direction find. The gaps made it impossible to direction find or even to intercept since the frequencies were unknown and sub millisecond. -So yes, the Germans were on the verge of protecting their cypher and making Direction finding ineffective.

[@welshpete12]

Strange fact the snorkel although thought to be a much later invention . Was actually invented in Glasgow Scotland during the first world war ,but was not taken up .

[@donbrashsux]

This Chanel always has incredible information 👍

[@SoloRenegade]

Never knew about this. Battle of the Atlantic finally getting proper coverage.

[@Perfusionist01]

Very interesting. I had not heard of German developments in radar-absorbing materials. Somebody once wrote about being in a submerged sub running with a schnorkel; as the sea caused the ball valve to close, the diesels kept running, which led to major air pressure shifts inside the sub!

[@kc4cvh]

It may have been Peter Cremer, commander of U-333. In his book he described his experience with the snorkel, including ear injuries to his crew.

[@williamzk9083]

The snorkels became a little more refined as war went on as did depth keep gear. I think some used a pair of electrical electrodes to detect sea water and close and open the valve pneumatically much faster.

[@rfarevalo]

Read about the 2003 Chinese submarine that quickly killed 70 sailors when the diesel engines accidental were left on and consumed all the oxygen in under 2 minutes (due to a failed valve).

[@Baza1964]

They coated one new u boat at the end of war, made it sonar proof, it hunted in the English channel and the Allies knew it was there but couldn't lock onto it. They actually moved one of the shipping channels and mined the area to get it. The attacks stopped , after the war they dived on A wreck , it was a U boat coated in rubber.

[@marcusfranconium3392]

Correct they used rubber tiles with slits of different sizes to be used on a specific depth but it was not one of the more modern ones it was an ordinary type VII. Only a handfull would be outfitted with it due to lack of rubber or rubber substituted .

[@Baza1964]

@@marcusfranconium3392 yeah , it's been a while since I watched it. Absolutely fascinating how advanced they were.

[@marcusfranconium3392]

@@Baza1964 many of all german U-boats originated in the netherlands as there was a bit of clandistine sharing of information . The book IVS /Inkavos also known as A fox in sheeps clothing. has tons of insights on how germans got their submarines in the 30s . Also the discusion of the principles and ideas that would be incorperated in the Type XXIII submarines. As one of the dutch engineers escaped to england and designed a 3 cilinder submarine in late 1941 early 1942 presented it the britisch admiralty as cargo sub , it looked promising but would take to long to be of use in the relief of malta and crete . as thoe would be solved before the submarines would be operational . over the years the design was refined and one of those are now in a museum in den helder A 1942 sub design finaly build in the 50s Quite an interesting book . to read . also tech that came in to german hands . there should be an english verison some where as well . But this is what the book looks like has a dutch and german part in it of information nautiek.nl/new-maritime-books/naval-books/4646/een-vos-in-schaapskleren

[@williamzk9083]

The coating was called "Alberich" (named after the Wagnerian character who had a cloak of invisibility). Early versions from 1942 It took a while to get the details right such as glue but much was resolved by 1944. The speed of the Type XX1 and quietness was such that at below 6.2 knots with creeper drives in use the sub couldn't be tracked by hydrophones at even a few hundred meters. If the Sub used its full speed of about 15 knots the Allied hydrophones blinded by the turbulence. With a comprehensive set of radar detectors for 3cm and 9cm "Athos" such as, radar that could be used submerged (FuMo 391 Lansing) and infrared detectors etc it does seem that the Germans were close to reversing the allied advantage.

[@Baza1964]

@@marcusfranconium3392 Thanks for the interesting information.

[@martinr3136]

I am impressed by this item's showing of the intelligence-gathering and then clear charting of the insights thereby gained. This is obvious evidence of a WWII-prompted advance / consolidation in data analysis and it's most-useful, meaningful, purposeful portrayal up the decision-making hierarchy. Very well-selected examples / exposition of all these themes here thanks.

[@danielstickney2400]

Concise and well researched. Good job.

[@JoeJ94611]

I remember reading if the UBoat using a snorkel was in rough seas, the snorkel would seal iself when covered by a wave. Because the running deisel engines kept sucking the air causing negative pressure, this resulted in crew discomfort.

[@alfaeco15]

Just seal the diesel compartment

[@roberthutchins1507]

That was still a problem into the 1990's when I was looking for subs. It's quite a noisy issue and made a very distinctive noise on passive sonar.

[@williamzk9083]

@@alfaeco15 Sounds like a very practical solution. You could even pressurize the compartment to say 2 atmospheres. The Germans still intended the H2)2 hydrogen peroxide submarines to be the main goal, the Type XXI were just a quick way of getting a big improvement. There was also a oxygen diesel program and even a nuclear sub program. The Germans shut down the atomic bomb project but kept working on reactors. I think a physicist called Martins was in Charge. Mentioned in "Virus House" which was the Kaiser Wilhelm Institutes nick name.

[@SgtMjr]

and the crews hated the schnorkel because of that. It was really bad when the air pressure changed so suddenly, horrible for the crew.

[@williamzk9083]

@@SgtMjr It was only a matter of good depth keeping to prevent submersion of the snorkel for an extended period.

[@MrDrunkblackstar]

Great material! Thank you. I think it's hard to precisely evaluate the effectiveness of any German equipment during the last period of war, since there were too many interfering factors and general degradation of German capabilities.

[@ant4812]

Cool video. One little thing I might add - the German code name for the anti-radar coating on the schnorkel was "Schornsteinfeger" - chimney sweep.

[@williamzk9083]

Schornsteinfeger was a type of radar absorber called a "Jaumann absorber". The one on u-boats was about 2.5cm thick and optimized against 9cm radar. It consisted of 7 sheets of cardboard that were laced with exponentially increasing amounts of carbon black that rendered them semiconducting. It was vacuum impregnated with PVC to make it water proof A radar wave rather then bouncing of the from the front would gently be adsorbed like on a pebble beech. What remained would hit metal at the base and reflect outwards where it would be absorbed on the way out. On the surface with out cancel out the incipient wave. Absorbed 96% at 9cm, 80% at 3cm and about 50% at 25cm. They had another absorber called Wesch which was ferrit based that absorbed about 30% but could be muldred into 3D. Combining Ferrties with the Jaumann absorber absorbed around 99%.

[@alexius23]

The snorkel was a Dutch invention. From what I read most U-Boat crews were not big fans of snorkels.

[@waynesimpson2074]

Yup, when the ball-valve snapped shut in high seas the diesel engine still demanded air; this caused a truly debilitating, momentary, pressure drop in the hull. This pressure pulse cycle , literally, knocked the snot out of the U-Boat crew.

[@martijnb5887]

That U-Boat detection device Dönitz is referring to is Enigma :) It is surprising that the Germans only started using the Snorkel in the last phase of the war. They got the technology in a nearly finished state in the spring of 1940 when they conquered The Netherlands.

[@WagesOfDestruction]

i wonder if it would be much use to them till 1944

[@brianswan3559]

Indeed Enigma dectripts coupled with airborne centimetric radar and HF/DF.

[@Keith80027]

Thanks for providing this information I didn't know.

[@sicksickman]

These are really great videos. Kudos

[@williamashbless7904]

Well, I think the Schnorkel did protect U-boats from detection, it rendered them incapable of attacking enemy shipping. So, it was a win(?) instead of a win-win. Your use of visuals is first rate and gives your audience a very clear picture of the info you are trying to convey.

[@tomsmith3045]

I always wondered why the allies never used the snorkel in ww2. Now I know! First, because we didn't need it, German and Japanese ASW wasn't anywhere near as good as ours, and second because it was a huge PITA to use and deploy, and limited the capabilities of the sub when deployed. This was fascinating.

[@mattheide2775]

Thank you for the video ❤

[@billyponsonby]

Fascinating

[@frankbodenschatz173]

Nice information, and great presentation.

[@paintnamer6403]

The word for today is Schnorchel.

[@williamstearns7490]

It’s insane that those subs could safely dive to 650ft. That’s 50ft deeper than the Space Needle in Seattle is tall!

[@nickdanger3802]

10.50 1st happy time 22 ships sunk per U boat sunk, 2nd HT 18 ships sunk per U boat sunk

[@dukecraig2402]

Overall losses of U-boats and crews, 75%.

[@johnmcmickle5685]

If they could only make 6 knots the threat was greatly reduced. At that speed if the ship did not sail into a position for them to fire a torpedo, they definitely could not run ahead to get into a firing position.

[@ToreDL87]

The ocean is huge, even Bismarck was tough to spot and it had the worlds largest navy looking for it. Very hard to look for a Uboat if you don't know it's there in the first place. Radio triangulation was worse than breaking Enigma, existence of Asdic, radar & hedgehog. Doenitz demanded pretty much daily radio reports, his Uboat commanders obliged, which was tantamount to self foreversleeping. He was the "be home by 10, I want accurate reports call me every 10 minutes" type, whereas everyone else were like "Ok go ballpark'ish here, see you later, have a fun time out".

[@CoachKen10]

This video is fantastic! I appreciate the hard work and hours that went into producing this content. I’m not going to lie…. I cracked up laughing every single time the word “shanorkel” was said….

[@dalehuff5740]

Thanks!

[@WWIIUSBombers]

Thanks for the kind channel donation. It is much appreciated.

[@gerard-nagle]

Question. Did they have to surface to deploy the snorkel, as the pictures at the start show a flanged connection between the snorkel mast and the submarine. Also, there seems to be only one flange, so I guess this one is for say exhaust gases and at the base, another connection for fresh air. A google search left me none the wiser I’m assuming modern snorkel equipped submarine can deploy it underwater and then rise to periscope depth to start engines.

[@MonkPetite]

The antenna for oa the enigma signals was an long wire . It was long wave radio. FH . The snorkel is a Dutch invention and not German. These where used in ww1 also. The exhaust was not included. This was relived underwater. Operation of the snorkel was not easy . Valves had to be timely opened and closed. Also diving in emg dive the engine stoping was not always times well. The engines sucked the air out of the hull and so crew endured massive pressure dips . The snorkel was not attach to the engine but to inside of the hull. A float on top prevented water ingestion. Again that made pressure dip true the hull of the boat. But this was solved by adding a blower to provide some over pressure. But still the pressure deferential remained.

[@mikebikekite1]

How much time was there between a U-boat detecting a radar signal and a plane detecting it's reflection? Was it enough time to submerge? Could U-boats equipped with a snorkle of just stopped moving which would stop the easy to spot wake pattern?

[@reginaldmcnab3265]

11:17 well the enemy had broken the enigma code and so there location were known! The was one U-boat captain who would often refuse to make radio contact with headquarters and with other U-boats and he had a high kill score.

[@annettaharris9269]

Germans did not believe that it was possible to not only develop but mount millimeter wave length radar on aircraft.

[@fantabuloussnuffaluffagus]

Really interesting. That is some serious research. Well done. This makes it sound like the Germans were solving the wrong problem. I have no idea what the right problem would have been. Visual detection of the periscope feather?

[@grizwoldphantasia5005]

Staying underwater longer and moving faster. I believe it was the final electroboats which solved this problem, although no real telling if they would have sunk more targets and survived longer, since they probably still had to surface to find targets, maybe even to aim at targets.

[@williamzk9083]

@@grizwoldphantasia5005 The Type XXI had the GHG passive array sonar that could pick up a convoy at over 100km asnd in some cases 160km. They had a microwave radar in use and it was being adapted for submerged use. The new Active Sonar allowed them to target under water without being detected. If a sub reported a convoy on its hydrophones it could be triangulated A patrol aircraft would be sent out either a Dornier 335 or Dornier 635 if possible to report on the convoy or a Ju 290 which would keep its distance.

[@paulbryner6251]

I think another problem with schnorchel deployed U-boats is in detecting targets. If you are always sailing submerged and only have periscope for observation it would be hard to find anything. Sound gear is not going to help with your diesels running.

[@williamzk9083]

The Germans had developed a phased array hydrophones called GHG array that could detect a convoy at over 100km and I think individual ships at 60km. No one else had them. Bearing accuracy was about 2 degrees but I think got to 0.5 degrees on the Type XXI. Normal hydrophones were available for looking straight ahead. The little company called GEMA that made sound recording equipment for training sonar opperators became the giant company that made the famous Seetakt radar. -As you can imagine when the u-boat could communicate freely they could triangulate a convoy. -The Luftwaffe supported the u-boat effort very poorly due to a lack of appropriate aircraft.

[@SeattlePioneer]

Similarly, I would expect that a Schnorkel deployed Uboat would be especially vulnerable to attacking aircraft. When aircraft did spot a Schnorkel with radar, I presume they would attack. The U boat would likely find it very difficult to be searching for targets and looking for attacking aircraft through the limited viewing of a periscope.

[@williamzk9083]

@@SeattlePioneer The procedure was to rise to near periscope depth and use the hydrophones to listen for the sound of aircraft engines. If non were heard the search periscope or “episcopate” would be used to search for threats. Obviously when the diesels were started the u-boats hydrophones were deaf and the episcope only of some use in daylight rather than night. The intention was to have the entire masthead coveted in a radar absorbing material. The code name was schornsteinfehger (chimney sweep) and it was a jaumann absorber that reduced the radar cross section 20:1 so that the S/N ratio would tend to merge with sea clutter. On top of that there were to be radar warning devices to cover the 3cm, (called Athos) 9cm and meter wave band. There was also an infrared warning device that reacted to engine heat if the radar warning devices failed. All of these devices entered service but not all uboat received any or all of them. They were devices from late 1944 but mostly early 1945. There was also the planed FuMO 391 Lansing radar that gave of a single 125kw omnidirectional pulse and detected any aircraft up to 100km away. It was a derivative of seetakt. A single pulse is almost impossible to detect in the day and impossible to direction find. A derivative of the Berlin PPI radar was also being adapted for under water use. Ballspiel was to be a raft for directing guns.

[@mongolike513]

Dear Mr.ww2usb by any chance did you do an educational series of vids on ‘cafe racers’? In which case I have lost your tshirt merch. Respect. Have you covered FIDO yet? Hmmmn?

[@WWIIUSBombers]

The channels next release will be usage of Sonobuoys. I'll cover FIDO in the video after Sonobuoys.

[@mbj__]

But how much was due to Enigma codes being intercepted in relation to radar absorbtion and snorkel? If the Allies knew where the subs were anyway through code breaking...

[@elykeom1]

“Going for a ride on the snorkel” xD

[@ethanmckinney203]

Didn't the operating area change completely during periods VI and VII? With many of the U-boats operating in the narrow and shallow English Channel, and in the Dogger Bank/North Sea area, pretty short-ranged ASW aircraft could reach them and long-ranged aircraft didn't have lengthy transits to and from operational areas, allowing them to patrol longer. Similarly, the Allies could swarm smaller areas with ASW corvettes, destroyer escorts, and destroyers. Even if the U-boats could evade them easily, the U-boats still had to drop below schnorkel depth to avoid visual detection and shut down their diesel engines to avoid using up all of their oxygen and to avoid simply being detected by hydrophone.

[@Crabby303]

How much of the increase in U-boat losses was down to successful code-breaking at Bletchely Park I wonder?

[@dougerrohmer]

I think Bletchley Park is a strategic thing, so the Admiralty knows how many U-boats are going to be where and heading in which direction. They can then reroute the convoys, and if nothing else is done the U-boats will live for ever and so will the convoy. But then at tactical level comes radar, sonar, and countermeasures. The attackers would know that in this 20 mile area there are 6 U-Boats and set out to find them and ventilate them. The countermeasures might make it difficult, but at the same time the attackers could concentrate forces and keep looking until they find them.

[@zhoufang996]

Why did the snorkle fail? Did it at least reduce air attack losses? If not, why not?

[@gort8203]

Good question. I would also like to know. There seems to be a trend on KZbin where an innovate aircraft, weapon, or device is labelled as "ineffective" because it didn't change the course of the war or a battle. It's not fair to expect an overall miracle from any one innovation. Many innovations were useful advances in military technology that lived on elsewhere even though the Third Reich did not.

[@ulfenburg7539]

@@gort8203 exactly. So many people think it is so black and white when it is not.

[@grizwoldphantasia5005]

Uboats were still slow underwater. The snorkel only lengthened how long they could stay under. It also shut off momentarily when waves covered its intake, forcing the engines to suck air from the crew compartment, making life miserable. And Uboats still had to surface to find targets. A submerged Uboat is a generally harmless Uboat.

[@ethanmckinney203]

​@@grizwoldphantasia5005The periscope stuck up in front of the schnorkle. It was still possible to find targets. Operational U-boats stayed submerged for the whole cruise, if possible.

[@allangibson8494]

Snorkel equipped submarines still left a visible wake - and were easy targets for magnetic anomaly detection equipped and sonobuoy equipped aircraft because they were blind to aircraft above them. They were however harder to find on radar.

[@louisavondart9178]

If you make your Uboots give away their location every day by radio, nothing is going to protect them.

[@torarildhenriksen371]

They became radio silent whent they stayed submerged and Bletcly park got less material to work on

[@Allan_aka_RocKITEman]

I do not think I even knew the Nazis had radar-absorbent coatings on their U-boats.

[@frankbodenschatz173]

Pretty cool for mid 40's tech?

[@RemusKingOfRome]

In the "Wizards War" of WW2, the dark warlocks couldn't keep up with the Wizards of light.

[@Tiagomottadmello]

👍🏻👍🏻👍🏻👍🏻

[@Coinbro]

Besides Britain breaking its peace treaty with Germany and starting ww2 it doesnt seem like Germany had planned on uboats building the super battleships I would think snorkel would have been running day one or by 1940 when germany started battle of Britain

[@harpomarx7777]

You refer to the "conning tower" @ 3:40 and that is incorrect. A conning tower is a waterpressure-tight structure INSIDE the familiar structure known as the TOWER in U-Boats ("Turm" in German). The tower contained the conning tower inside as well as the periscopes, ventilation ducting, ready-use magazines, defensive weapons, "cigarette deck", and the familiar chariot bridge. It is all you can see rising from the deck. You cannot see the conning tower in any submarine because they are internal structures. In the US Navy of WWII, we refer to the visible structure above the deck as the "sail" and the British refer to it as the "fin". The only modern submarine I know of which actually had a conning tower is the Russian Typhoon and the last one is slated for scrapping. So please ... stop referring to the German TOWER as the CONNING TOWER. This is a common error, so be one of the few "in the know" and use the correct terms.

[@randomnickify]

Irrelevant semantics.

[@lukycharms9970]

Listening to the word “schnorcle” makes a this entire video worth it even beyond the educational value

[@Whiteyy191]

Schnorkel

[@roelkomduur8073]

The snorkel ( snorkel is the correct way to write) was actually a Dutch pre- war invention.... Dutch submarines O 19 and O 20 were given the "snuiver mast") snorkel" in 1939.... So No German invention, but stolen from the Dutch Navy.

[@agrxdrowflow958]

Too little too late.

[@burroaks7]

very cool

[@marcusfranconium3392]

First of all , the germans where not verry advanced in submarine building . actualy their U bouts Tybe IIA IIB and prototype Type VII . all came from the Netherlands . the snockles included the dutch where using them already in the 1930s . Many items on a german sub came from dutch shipyards .

[@johnmcmickle5685]

If they could only make 6 knots the threat was greatly reduced. At that speed if the ship did not sail into a position for them to fire a torpedo, they definitely could not run ahead to get into a firing position.