Using the snorkel safely without being bombed

[Cal Dega]

I'm using the GWX mod and started a campaign in April of 1944. I'm trying to figure out a way to use the snorkeling device safely without being bombed by aircraft.

I don't have the anti radar coating yet so it's reasonable to guess they are discovering it through that means.

My idea is to use the batteries to the maximum extent until nightfall the use the snorkel for only recharging the batteries. Is there a better way than this? It seems like it would take forever to get anywhere at this rate. Essentially I would be submerged the whole patrol.

[Marcello]

Actual orders were as follows:

Originally Posted by Marcello

Employment
Late war procedures for employment of u-boats can be found at http://www.uboatarchive.net. I post the sections relevant to the game.

Current Order No: 1. Issued Nov. 1944.


(Procedure when underway and in operational areas).



I. The Schnorchel has to a considerable extent, escaped enemy air attack and with the simultaneous decrease in U-boat losses, has enabled them to operate again, in areas strongly defended by aircraft.

Principles for Proceeding. The task of the Commander is to take the boat to and from the area of operations without any great diversions, to avoid skirmishes with the enemy defence, to utilize however, every opportunity for attack.

Principles for the operational zone. In order to make full use of the possibilities offered by the Schnorkel, approach close to the enemy shipping near the coast. Only there, are successes to be obtained.

II. Procedure of boats when underway and when in the operational zone depends on the strength put up by the enemy air force. Commander U-boats differentiates between areas with a strong, medium and weak defence. If a Commander establishes another aircraft position in an area, as described under A - C, he can intensify or modify his tactics according to the change.

A. Strongly defended areas. Squares AN, AF, AE, AM, BF, CG, DJ, AL, BE of the eastern third, further a strip of nearly 100-200 nautical miles off North and South America, including the Caribbean.

Procedure: on principle proceed submerged when underway and when on operations, recharge when Schnorkelling (total submerged warfare). Recharge only above surface, only when Schnorkelling is not possible for technical reason.

Execution.

1. On setting out and returning when Schnorkelling.

a). For more detailed instruction concerning schnorkelling times, boat routine, making best of weather conditions, see Current Order No. 20.

b). Normal cruising depth above 50 meters (162.5 feet) - At routine times and when taking hydrophone effects at periscope depth. Good hydrophone conditions in no way exclude periscope observations while proceeding.

2. When setting out and returning while submerged with charging above surface. Only in cases of a faulty Schnorkel or when other reasons (e.g. a too strong current) make it necessary.

a). Charging to be carried out, in conditions unfavorable for air attack, that is, in general, by night. Favorable - moonless, very dark, haze, fog, storm.

b). If at night especially great air and radar activity are observed, charging can be carried out in the daytime, in fog, or in clear weather with good visibility and good Ack Ack conditions. In case of doubt the proceeding by night is more favorable, since, in the event of an attack, better opportunity is afforded for submerging and for shaking off the contact, moreover, a simultaneous attack from several aircraft is difficult.


c). During charging, complete Ack Ack readiness. Commander on the bridge. Keenest lookout. All armament ready and unmasked, so far as weather conditions allow. Gunner in layer position with shoulder-piece in position. In weather conditions which enable accurate surprise attacks, if necessary man only the twin barrelled gun, in order to be able to submerge more quickly when located.

d). Set up the available FUMB. If there is FUMO on board, warm up well before surfacing, and use as follows:- Immediately after surfacing a circular sweep with the FUMO, then only Radar observation with "Wanze" and/or "Borkum and Tunis". If airborne locator has been observed, in general, submerge. If charging is urgent, when detecting a locator, D/F with FUMB, search by FUMO, and continue to observe the enemy. Until picked up by FUMO, a longer period (up to 30 mins.) can elapse. If no enemy is detected, do not return too soon to FUMB. If the "Hohentwiel" set is in perfect order and the servicing crew well-experienced, the apparatus, in continuous search alone may be used, when underway as an air-raid siren.

e). Do not remain on the surface longer than the time required for charging, as this endangers the boat unnecessarily. Exceptions: In especially unfavorable flying conditions and if the FUMO is functioning perfectly.

III. Procedure in the operational zone.

A. Submerged on principle and only while schnorkelling. On breakdown of the Schnorkel, in general, return to base. In this case carry out charging as under 11.

B. Keep close to traffic focal points and to coast routes, for it is only there that interception of traffic can be guaranteed. Lying on the bottom and taking advantage of the density of water which renders it more difficult for the U-boats to be intercepted by hydrophone and radar, facilitate, according to the latest experiments, a successful U-boat operation even at a depth of well under 100 metres (325 feet).

C. Initiate all measures for daylight attack, since this is most favorable. Submerged night attack promises success only at full moon.

D. Go frequently to periscope depth, do not rely upon the hydrophone. By night and when there is traffic, go down to the bottom, to save batteries.

IV. General Rules for "total submerged warfare".

A. Avoid surfacing by astronomical reckoning as far as possible. According to experiments so far to hand, extremely exact determination of position is made possible by very accurate dead reckoning, by taking the current into consideration and by making full use of the sounding device, electrosone and radio-beacons. When close to our own, or to enemy coast, make full use of every means of determining a position by land.

B. [...]

C. Even when proceeding without incident under water and when on operations, it is necessary to reduce the consumption of air and current to the minimum, in order to shorten the charging time and to have sufficient battery capacity for the attack when contacting the enemy, and further, in case of pursuit, to be able to run on it long enough without being forced to Schnorkel and/or surface.

D. Especially when the Schnorkel is out of order the boat must continue to run submerged in order to evade the shadowing aircraft and to be as faras possible beyond the range of location of the point of submerging, when it surfaces. Therefore when below water, not more than slow speed ahead, both engines. Use only the most necessary consuming plant, economize on light and air, the E-condenser consumes much current. Trimming and pumping with the auxiliary bilge pump. Carry out night routine according to Current Order No. 2.

B. Areas with medium air defence.

Areas not specified under A). Atlantic - North of 15 degrees South, coastal strips 100-200 nautical miles off the African coast, fringes of the Indian Ocean, including islands.

Procedure: Submerged by day, above surface by night.

a). In the open Atlantic between 30 degrees North and 15 degrees South, in clear, cloudless weather, with good Ack Ack conditions and with the FUMO switched on, proceed on the surface; without the FUMO, on principle, submerged. FUMB locating has been intercepted, dive and remain for a while submerged. If the enemy holds you on his Radar beam, he later sends out carrier planes, operating from sight.

b). Above water keep Ack Ack gun ready for firing and by day at least six look-outs on the bridge.

C. Areas with weak air-defence.

Atlantic - South of 15 degrees South, open spaces of the Indian Ocean.

Procedure: On principle, on the surface, FUMB continually switched on.



Current Order No. 2


Procedure when Schnorkelling. Issued Nov. 1944.



Many undertakings of 40-60 days duration were carried out without surfacing. The Schnorkel proved very effective and through it operations were again possible in areas heavily patrolled from the air

a). In General.

? Principle: Under all circumstances attempt to recharge battery completely every day. On account of enemy positions the Schnorkel is not to be shifted. Continued reduction of the battery capacity can finally cause the boat to be in especially dangerous situation.

(1). Chose favorable conditions for Schnorkelling, i.e., in general at night, in a swell, poor visibility. By day only in clear weather with good visibility, the emotion of the sea from force 2 and is the Schnorkel does not smoke. Best at night, once 2-3 hours at the beginning and end of the night.

(2) The Schnorkel is not undetectable by radar. If the Schnorkel is correctly manipulated, that is to say, with the exhaust under water, it can be scarcely or only inaccurately intercepted. The motion of the sea reduces the possibility of being located. If the Schnorkel is fully raised, it can be located and attacked, therefore it is wrong to let the Schnorkel protrude too far when there is phosphorescence, so as to avoid a trail of foam. Then interception through location by radar is possible at a much greater distance and therefore more often than by a trail of foam. The range of location of the camouflaged Schnorkel is about 10% of the boat when on the surface. In practice it is scarcely interceptable.

3). Air attacks on dark nights are generally only possible with the use of artificial light. If a searchlight is detected shining directly on the boat or a flare above it, sound the Schnorkel alarm, and dive to at least 80 metres (260 feet). If searchlights and/or flares are detected searching a long way off, or their location is above the Schnorkel dipole, only sound the "quiet-Schnorkel-alarm", that is to say, dive to 20-30 metres (65-95 ft. approx).

4). When the Schnorkel is in use, periscope manned by the commander and officers of the watch in watches of roughly 1-2 hours. In boats of type VII C, turn the main periscope continually by hand. In boat type IXC in general, only the periscope for air observation. The raising of both periscopes results in oscillations, and moreover increases the danger of being located by radar. Do not proceed at too high a speed (i.e., with both Diesels on screw (aufSchraube)) this endangers the periscopes. They swing, bend and become leaky and cloudy; slight oscillations are frequently corrected by very small alterations of periscope height.

5). Noise caused by Schnorkelling is about the same as when the boat is running on both E-engines at a rate of 200 revolutions per minute. In areas where there is hydrophone activity do not refrain from using the Schnorkel because of the fear of being heard. According to experiments, boats have proceeded unperturbed with the Schnorkel in use, with hydrophone bearings of weak signal strength and with "circular saw noises" of medium signal strength. "Circular saws" on shadowing vessels cut out other noises.

6). Circular acoustic sweeps for enemy positions every 15-45 mins. - (unreadable) - dive to a depth of 20 metres. It is possible that

the shadowing craft makes towards a U-boat which it has intercepted by hydrophone and in order to remain undetected, will stop when the boat stops her Diesels in order to make a hydrophone sweep. Therefore measures have to be taken to be ready for a circular acoustic sweep as soon as Diesel engines are stopped.

Execution.

a). Order to engine room, central control and listening room: "Ready for circular acoustic sweep".

b). Switch off charging, charging diesel engine, electric fan and condenser.

c). Lighten the boat in order to avoid further pumping, once the Diesel engine has been switched off. [...]
d). Engine room telegraph to "Dive". Cruising Diesel is to be turned off and the E-engine run, utmost silence in the boat, and keep a listening watch.
e). [...]
f). [...].

Methods of Proceeding.

a). Schnorkel in sea up to force 6-7 (according to type of boat) steer broadside on, 1-5 degrees, with the ballast forward, with as little flooding as possible, otherwise current and air unnecessarily consumed when pumping prior to the circular acoustic sweep. Choice of cruising speed depends on the motion of the sea, and the oscillations and angle of the periscope.

b). Whenever possible ventilate the boat at least once during the day, for 15 mins. with the Schnorkel; this saves potash cartridges....

[Marcello]

I don't have the anti radar coating yet so it's reasonable to guess they are discovering it through that means.

The anti-radar coating is only partially useful, though this may well be realistic. Much better are the snorkel mounted RWRs.
Absent the above you can only minimize head exposure above water by ordering snorkel depth or adjusting it manually.
Generally speaking a Type VII forced to operate like a true submarine will be slow so the focus was put on attacking shipping in british home waters. A XXI can cruise a 5-6 knots all day so you have more reach but crossing the Atlantic will be a very tedious affair.

Eventually in real life an electrically controlled T-valve snorkel with much smaller profile would have been issued but only some Type IID had them installed before the end of the war.

[HW3]

I seem to recall reading that SH3's radar sensors treat the snorkel head as if it is a surfaced u-boat so, if the snorkel is up, it is like your whole u-boat is surfaced to the enemy radar. I believe someone made a mod to fix it but, I do not know for sure about that.

[Marcello]

Originally Posted by HW3

I seem to recall reading that SH3's radar sensors treat the snorkel head as if it is a surfaced u-boat so, if the snorkel is up, it is like your whole u-boat is surfaced to the enemy radar. I believe someone made a mod to fix it but, I do not know for sure about that.

I would have to check but I recall GWX fixed this.

[maillemaker]

If you don't have a RWR on your snorkle head, traveling by snorkle is dangerous. I almost prefer to travel on the surface where I have a watch crew that can spot for aircraft. Or use the snorkle at night.

Steve

[Marcello]

Originally Posted by maillemaker

Or use the snorkle at night.

Steve

That was in fact SOP.

[UKönig]

The air mast, or schnorchel, as Dönitz called it, using a dialect word for 'nose', had already been fitted to some Dutch boats before the war, but these had been used solely for ventilation purposes. The air mast fitted to the German boats of type VII and IX was intended as well to supply fresh air to the diesels, making it possible for them to recharge their batteries while underwater, instead of only on the surface.
The snorkel consisted of two tubes, the first for air induction, the second and slightly thinner one was for carrying away the exhaust gasses from the engines. The tubes were raised and lowered together by means of hydraulic pressure.
Before the introduction of the snorkel, U-boats had to spend most of their time on the surface, and only diving to carry out or avoid an attack. With one, they were able to stay underwater for weeks at a time. The record was 66 days, the second place record was 59 days. But these were exceptional feats of endurance for it was soon apparent that snorting made heavy demands on the crew, and afforded by no means, complete protection from attack.
While snorting, a U-boat crew had to maintain a careful watch at the periscope to ward off surprise air attack, for although the top of the snort mast showed only as a pinpoint on the enemy radar screen, it was liable to detection from the air by the exhaust trail or wave wake it left behind.
In all other regards, the crew had to be continually alert. In no more than light waves, the air inlet on the induction mast would repeatedly flood, and if the diesels were not stopped in time, they would pull their air in from the only other source, inside the hull, until, with the reduced air pressure, the mens' eyes would bulge from their sockets, or eardrums could burst. But some loss of pressure was unavoidable, and after a time, the continual changes of pressure would start to affect the health of every man aboard.
In the early days of the snort, a further difficulty appeared. When a U-boat plunged deeply into a swell, the exhaust would be unable to escape against the weight of the water, and would blow back down inside the hull. If the diesels were not stopped in time, the engineers would collapse with carbon monoxide poisoning.
A further and perhaps more serious disadvantage was the effect that prolonged snorting had on morale. At periscope depth, the U-boats were reduced to walking or at best, cycling speed. They lacked an adequate field of view. In daytime, the area seen through the scope was tiny, compared to the vastness of sea that the enemy surface vessels could cover. At night, the U-boats were completely blind, and now the snorkel made them completely deaf as well.
When U-boats had recharged on the surface, at least there were lookouts on the bridge with binoculars, but now, recharging at periscope depth, the only means of keeping touch with the outside world were the hydrophones, now rendered useless by the roar of the diesel engines.

[Marcello]

Originally Posted by maillemaker

If you don't have a RWR on your snorkle head, traveling by snorkle is dangerous.

Thing is, in real life traveling on the surface became suicidal. I am not sure how well game mechanics reflect this.

[maillemaker]

Thing is, in real life traveling on the surface became suicidal. I am not sure how well game mechanics reflect this.

I find air attacks to be pretty underwhelming in terms of damage inflicted, but they will damage your sub enough (any damage is enough, really) so that you can't continue your patrol.

By late war, you need 100% hull integrity so you can dive to maximum depths to have a chance at escaping escorts.

And in game, you will find TONS of air cover waiting to nail you using GWX in the late war years.

But if you run on snorkle during the day you risk getting nailed without ever seeing them coming unless you leave your periscope up and possibly have map contacts turned on. I can't remember anymore if aircraft automatically appear on map if your scope is up or not; I ran no contacts for a long time now.

[Zosimus]

I agree. Planes are not a serious threat. However, when you're hiding from destroyers at 240 m under and you remember that a plane put a few bullet holes in you awhile back and you're scared to go deeper, even though you know you need to... it just sucks.

As for planes, I find that I can hear them above me... even under water. That won't help you if you're running snorkel at 64x TC but it works fine for TC: 1.

Anyway, I've never found it suicidal to travel on the surface. You get the radar detection notification and you order the dive a few seconds before the plane shows up. What's the problem? It's actually rather convenient.

[Marcello]

Originally Posted by Zosimus

Anyway, I've never found it suicidal to travel on the surface. You get the radar detection notification and you order the dive a few seconds before the plane shows up. What's the problem? It's actually rather convenient.

In the game yes, in real life there were for example very long delays between the introduction of newer generations allied radars and the development of detectors that could alert the u-boat to them. U-boat were found and sunk by planes using decimeter wavelength radars and the germans could not figure for a long time why their meter wavelength RWR gave no warning. The snorkel was a much more straightforward mechanical solution.

[Zosimus]

The snorkel suffered from technical problems. It was not widely available until mid-1944. Additionally, radar could still pick up the snorkel when extended and planes often showed up to investigate.