Italian Schnorkel circa 1925

[Black Hornet]

The Italian SNORKEL



The invention of the snorkel is usually ascribed to the Germans, who first used it in wartime, in 1943. Most informed people attribute its origin to the Dutch, who installed it on the “O”-class boats in the late thirties.

Of course, undoubtedly Germans have the “historical” paternity of it, as well as the discovery of America is properly ascribed to Columbus and not to the Vikings, even though they preceded him.

But, really, at least chronologically the snorkel is an Italian invention. It was, in fact, the Major (Naval Engineer Corp) Pericle FERRETTI who carried out first studies and experiments, in the early twenties, at the Navy Yard in Taranto, where he was Head of the Submarines Department.

At the beginning, his idea was aimed just to make faster the submarine immersion: if the boat, running in surface on diesels, is already ballasted and trimmed for dive, but kept in “forced surfacing” – as he called this status of partial submersion – by the hydroplanes, the diving operations will be reduced only to “secure engines” and “planes to dive”.

For running in such a way, engines air supply would be caught through the existing battery ventilation intakes and exhaust gases would be discharged underwater, boosted by hydraulic ejectors. The initial experiments were encouraging.

The gas discharge system, real serious problem, was subject of an accurate study, published in 1922 on the Navy’s “NOTE DI INGEGNERIA NAVALE” (Naval Engineering Notes) and illustrated later, in 1927, in some lectures given (and, then, published too) by FERRETTI at the “Istituto di Guerra Marittima” (Maritime War Institute). This plant, anyway, was never carried out.

In fact, in the years between ’21 and ’25, FERRETTI proceeded in projecting and building a real snorkel plant, with an apposite intake tube to be placed on the conning tower. Air intake and gas exhaust were equipped with ingenious “dynamic valves”, rotating when open, able to avoid water flooding by centrifugal action.

This prototype, built at Taranto Yard, was installed on the submarine “H3” (a “Holland” boat purchased in Canada during the 1st WW) in Naples by the local Navy Yard, where FERRETTI in the meantime had been transferred.

On November 1925 the plant was tested, during apposite sea trials, by a special board which reported the results had been “more than satisfactory”. Only drawback: the increased visibility of the boat, due to the wave caused by the intake mast and the white trail produced by the exhaust gases. Anyway, the same inconvenience will be reported, some years later, by Dutch and, partly, it persists still now.

For his invention, on January 20, 1926, FERRETTI got the “BREVETTO INDUSTRIALE” (Design Patent) n. 244375 and some Navy’s awards.

Later, on April 13, 1926, during naval manoeuvres in the waters of Tripoli (Libya), the plant was shown to Mussolini.




(1926 - Benito Mussolini on board of "H3" Submarine, in Tripoli)



In the early thirties, in view of new submarine constructions, FERRETTI - who, in the meantime, had left the Navy and become teacher at Naples University – was asked to update his snorkel project, which assumed a new configuration and was renamed “Apparecchio ML” (Device ML). Mark “ML” has no technical meaning: those are just the initials of Maria Luisa, the name of Mrs. Ferretti, whom he wanted to pay homage.

So, in 1934 the Navy decided to install the “Apparecchio ML” on the submarine of new “SIRENA” class, some of them under construction at C.R.D.A. shipyard, in Monfalcone (north Adriatic Sea). C.R.D.A. built and tested ashore some of the devices and started to fit them up on board. But, in 1937, the SUBMARINE COMMAND withdrew the order and even the plants already installed were removed.

Even though such a sudden change looks rather odd, the decision was not totally unreasonable: after all, according the tactical doctrine of submarine warfare in that time, the boats didn’t need strictly a snorkel plant, which, on the other hand, was a dangerous complication. Even the Admiralty removed the snorkel from the Dutch boats repaired to England; and Germans too, from the captured boats. Only the radar advent will impose the snorkel.




( "H" Class Submarine)



This is, in short, the Italian snorkel story.

There are no proofs of contacts between Italians and Dutch during the snorkel achievement process. Very likely, they operated independently, not knowing each other.

Instead, it seems that Germans had some knowledge about the Italian carrying out, since they searched for FERRETTI after the Armistice (September 8, 1943), but he was able to escape their hunt.

[corpcasselbury]

Well, the German schnorkel wasn't the war winning device that the Kriegsmarine had hoped it would be. There were many problems with the device, including the frequent buildup of carbon monoxide gas within the U-boat's hull. Volume 2 of Clay Blair's "Hitler's U-boat War" goes into much detail on this subject, including what specifically happened aboard those subs that had something go wrong with their schnorkels.

[Black Hornet]

True, but these problems were mostly worked out by 45, & would have been worked out much earlier had it been worked on consistently from 1925.




There were at least 3 snorkel head designs starting with the original ring valve type which was replaced by the ball valve and finally the best one, the T-valve. The T-valve, used on the Type XXIII, was virtually invisible even to 3 cm radar

A large deployment of the XXI would have completely upset Allied ASW and led to high shipping losses. The days of just flying up and down the ocean with the radar on and sinkinging unsuspecting U-boats were over. Radar would have been virtually useless so just finding the XXI would have been rather difficult. It would have turned into a sonar war in which finding and sinking an XXI would have been a major production. A scared up XXI could go down below the layer at 200 meters, stay there for up to a week and then stick its snorkel up as far as 350 miles away.








The new boats did evade detection however.
The T-valve, used on the Type XXIII, was virtually invisible even to 3 cm radar.
http://www.uboat.net/forums/read.php...9845#msg-59845



They exceeded our expectations in one respect, by remaining at sea for 4-5 weeks instead of two or three as was estimated. U.2321's patrol lasted for 33 days.
Some sources say that type XXIII captains reported that none of their boats was counter attacked or detected and attacked during the XXIIIs short operational career. This above all else showed their abilities to operate against strong ASW forces and survive.

[corpcasselbury]

Clay Blair's book also deals with the Type XXI and other "wonder" U-boats.

[canambridge]

Clay Blair's book also deals with the Type XXI and other "wonder" U-boats.

So what did he think about the wonder U-boats?

[corpcasselbury]

Clay Blair's book also deals with the Type XXI and other "wonder" U-boats.

So what did he think about the wonder U-boats?

Not much. As I recall, performance was not what the Kriegsmarine had hoped for, the hydrogen peroxide engine system was too complex and dangerous and worst of all, many of the boats were poorly constructed. BTW, Blair actually served aboard one of these boats as a member of its American evaluation crew after the war. I highly recommend both volumes of "Hitler's U-boat War"; they give credit where credit is due, while at the same time setting the record straight on many of the myths of the Battle of the Atlantic.