Torpedo failures - weather related.

[GJO]

I recently started a new career in SH3 with GWX and Hsie's V16b patch. On my first war patrol all but one of my 14 torpedoes failed to detonate -the 13 duds just sailed right under their targets despite my careful attention to depth setting. These were all G7a types fired from a range of between 450 and 500 metres.

Being somewhat disappointed, I decided to research the available facts and found that during the early war years, a 30% failure rate was experience but, nevertheless, the G7a was regarded as the more reliable torpedo choice. Having said that, I have been unable to find any evidence to suggest that the depth keeping ability of these torpedoes was affected adversely by the sea state since failure seemed to occur equally in relatively calm water - the early failure appears to have been blamed on excess pressure in the (depth keeping) balance chambers which caused the torpedoes to run too deep and defective firing pistols which resulted in either premature detonation or failure to detonate on impact. Both faults could have been partially compensated for by using impact pistols and setting the torpedo to run shallow as was ordered.

None of the above would have caused the 93% failure rate that I had in the game so I have concluded that my preference for attacking in adverse weather conditions conflicts with the torpedo failure model imposed by Hsie's V16b patch. I have therefore deselected the "Torpedo failure fix" and have re-run my first war patrol in which I suffered just three torpedo failures and one that missed its target completely and I think this is possibly a more realistic result? All comments and suggestions welcome . . .

[Aras]

Yes. It is related to H.sie patch. If you read the manuel, it is explained very well. If you want to have minimum risk of failure, you should launch your torpedoes at least 4*windspeed/10 m depth.

Example :
Wind speed is 6m/s, safe depth to fire the torpedoes is 4*6/10 = 2,4 meters
Wind speed is 15 m/s, safe depth to fire the torpedoes is 4*15/10 = 6 meters

Any torpedoes fired with depth set to less than windspeed/10 will %100 fail.

[banryu79]

Originally Posted by Aras

If you want to have minimum risk of failure, you should launch your torpedoes at least 4*windspeed/10 m depth.

Sorry to bother with this question but: what is this 'rule' simulating? (I have not tried H.sie patch yet).
The depth keeping problem caused by the excess pressure in the torpedo's balance chambers?

[BigWalleye]

Originally Posted by GJO

I recently started a new career in SH3 with GWX and Hsie's V16b patch. On my first war patrol all but one of my 14 torpedoes failed to detonate -the 13 duds just sailed right under their targets despite my careful attention to depth setting. These were all G7a types fired from a range of between 450 and 500 metres.

Being somewhat disappointed, I decided to research the available facts and found that during the early war years, a 30% failure rate was experience but, nevertheless, the G7a was regarded as the more reliable torpedo choice. Having said that, I have been unable to find any evidence to suggest that the depth keeping ability of these torpedoes was affected adversely by the sea state since failure seemed to occur equally in relatively calm water - the early failure appears to have been blamed on excess pressure in the (depth keeping) balance chambers which caused the torpedoes to run too deep and defective firing pistols which resulted in either premature detonation or failure to detonate on impact. Both faults could have been partially compensated for by using impact pistols and setting the torpedo to run shallow as was ordered.

None of the above would have caused the 93% failure rate that I had in the game so I have concluded that my preference for attacking in adverse weather conditions conflicts with the torpedo failure model imposed by Hsie's V16b patch. I have therefore deselected the "Torpedo failure fix" and have re-run my first war patrol in which I suffered just three torpedo failures and one that missed its target completely and I think this is possibly a more realistic result? All comments and suggestions welcome . . .

Herbert Werner, in his first-person account of commanding a U-boat in WW2 (Iron Coffins), mentions several times that attacks either failed or had to be abandoned due to heavy weather. So we can conclude that torpedoes were subject to failure in heavy weather and that U-boat skippers knew this and were reluctant to attack in bad weather.

The problem is not one of torpedo defects. It is due to the shallow-running, self-propelled torpedo being disrupted by wave action near the surface and possibly even broaching. A broaching torpedo, clearing the water at 40 knots and then smashing into the next wave, is liable either to detonate short of its target or be deflected. h.sie simulates these failure modes by setting a "failed" torpedo to maximum depth. That's an artifice, but the operational results are appropriate.

The problem was not unique to the G7a, or to German torpedoes. Dick O'Kane has some similar discussion in his books detailing his experience commanding an American sub.

You can not compare your 93% failure rate, achieved under conditions which R/L Kaleuns would avoid, with their 30% experience rate achieved mostly under better conditions. Your high failure rate is why such conditions were avoided.

If you want to attack under conditions which historically were avoided, that's up to you. If you do, I strongly recommend that you first read h.sie's excellent and thorough documentation of the "Torpedo Failure Fix." Here you will see the algorithm h.sie used to model the problem and infer the tactics you can use to minimize its effect. Setting the torpedo to run deep and relying on the magnetic exploder can be effective, until weather conditions argue against risking a torpedo at all.

But you shouldn't expect 70% torpedo performance in 15 m/sec winds.

[GJO]

I am currently reading 'Iron Coffins' but have not yet reached the point in the book where Werner took his own command. In research elsewhere, I haven't found any evidence to suggest that wind speed had any effect on a torpedo's performance and although it seems logical to expect high waves to cause problems, U Boat Commanders were instructed to attack (and instructed how to attack) in these circumstances whenever a suitable target presented itself.

I agree that Hsie's work and thorough documentation is quite splendid but for my own interest I just wonder what real life evidence there is to say that a torpedo fired at close range in a big Atlantic swell would be prone to failure. Surely, the weapon was designed to be used in the Atlantic where the sea is rarely calm and huge waves are normal.

[banryu79]

Originally Posted by GJO

Surely, the weapon was designed to be used in the Atlantic where the sea is rarely calm and huge waves are normal.

Mmm... seems a logical deduction, but from experience of RL design failures (in other fields) I will not bet on it

[BigWalleye]

Originally Posted by GJO

Surely, the weapon was designed to be used in the Atlantic where the sea is rarely calm and huge waves are normal.

Based on the sorry history of poor torpedo design and development in both the German and US navies, I'm not sure that is a safe assumption.

[Lokisaga]

With these torpedoes it's important to remember that we're talking about something with the same mass as a 4-door sedan slamming into waves at 75-80 kph (45-50 mph). It stands to reason that something could be damaged and cause the torpedo to run deep, run off course, or prematurely detonate. Given how little attention the designers paid to critical components (the impact and magnetic triggers, the depth keeping machinery), I don't think strengthening the torpedo casing even occurred to them. H.sie's mood simulates a number of different mechanical failures by simply overriding the depth setting on the TDC. The torpedo runs at 25 meters and fails to detonate. It achieves the desired end result, a torpedo failure, without the need to program completely new torpedo behaviors for each possible malfunction.

[Warren Peace]

For further reading regarding the failures of German torpedoes, I would suggest this little gem:

http://digitalcommons.georgiasouther...99&context=etd

I haven't gotten through all of it yet, but thus far it has proven to be a well researched and well written thesis on the German torpedo crisis that occurred early in the war.

Given what I have read thus far regarding the depth keeping springs, heavy waves would definitely have an adverse effect on torpedo reliability. The depth keeping springs were not thoroughly tested, or reliable, to begin with; combined with the constantly changing water pressures that come with 2-3m swells, I can easily imagine some failures being the direct result of heavy waves. To bring wind speed into the equation, winds above 15kt can easily cause swells of 3m or higher.

[GJO]

Although many of us think of the breaking waves that we may see at the sea shore or in shallow water, the long rollers of the North Atlantic are quite different. Here the length of the trough between wave crests may be more than sufficient to enable a torpedo to keep to a constant depth below the surface whilst following the shape of the wave - this would be especially true if the advice provided at Torpedo School was followed regarding positioning to enable the weapon to be fired at approximately 90 degrees to the wave direction.

ETA: In heavy seas, merchant ships (especially in the days of sail or steam) would choose to head into or away from waves rather than take them broadside on. Therefore, a torpedo fired at 90 AOB would be fired along the waves rather than against them.

[BigWalleye]

Originally Posted by GJO

Although many of us think of the breaking waves that we may see at the sea shore or in shallow water, the long rollers of the North Atlantic are quite different. Here the length of the trough between wave crests may be more than sufficient to enable a torpedo to keep to a constant depth below the surface whilst following the shape of the wave - this would be especially true if the advice provided at Torpedo School was followed regarding positioning to enable the weapon to be fired at approximately 90 degrees to the wave direction.

ETA: In heavy seas, merchant ships (especially in the days of sail or steam) would choose to head into or away from waves rather than take them broadside on. Therefore, a torpedo fired at 90 AOB would be fired along the waves rather than against them.

"...along the waves..." doesn't mean that they would be tucked safely in the belly of the wave. A torpedo is not a bullet. It takes 30-120 seconds to reach its target. During that time, the torpedo is going to be passed over by several swells and troughs. Amd, at 15 m/s wind speed, those are not going to be long, gentle rollers. There are going to be perturbing forces on the torpedo which are going to push it in different directions over time. Think of trying to hold a boat on course in beam winds and seas. Granted that the torpedo is below the surface, but the water within a wave height of the surface is moving in a churning circular flow pattern. And the torpedo is steered by a mechanical feedback loop that is prone to upset by impulsive inputs.

Again, it is your game and you are free to play it in any way that you enjoy. So turn off h.sie's Torpedo Failure Fix and go out and sink 'em in a howling gale. We all adjust the game to make it play the way we want. Personally, I object to the lack of crew assistance and am willing to accept some totally unrealistic compromises to avoid having to do things no R/L sub skipper ever had to do. YMMV

BTW, how do you line up a shot? Do you turn off No Stabilized View? Either on the surface or at periscope depth in 15 m/s met conditions, the sub is liable to be moving around pretty well, maybe even broaching, and the peri or UZO under water much of the time. I can't even line up a shot under those conditions. What's your technique?

[GJO]

My technique is to get in real close (between 250 and 450 metres) on a parallel course matching the targets speed then drop back very slightly and fire with a 90 degree giro angle. The torpedo usually explodes amidships on the target which is often enough to break it's back or at least put it's engine room out of action. My only problem is that I sometime get port and starboard mixed up and have been known to send one off in entirely the wrong direction!

[BigWalleye]

Originally Posted by GJO

My technique is to get in real close (between 250 and 450 metres) on a parallel course matching the targets speed then drop back very slightly and fire with a 90 degree giro angle. The torpedo usually explodes amidships on the target which is often enough to break it's back or at least put it's engine room out of action. My only problem is that I sometime get port and starboard mixed up and have been known to send one off in entirely the wrong direction!

!

[Warren Peace]

Originally Posted by GJO

My technique is to get in real close (between 250 and 450 metres) on a parallel course matching the targets speed then drop back very slightly and fire with a 90 degree giro angle.

Originally Posted by BigWalleye

!

Quoted Walleye for emphasis/truth, I tried to actually respond in some fashion, but he summed it up perfectly.

[banryu79]

Originally Posted by Warren Peace

Quoted Walleye for emphasis/truth, I tried to actually respond in some fashion, but he summed it up perfectly.

Me too! I wanted to say something but was too much flabbergasted
Btw, Warren Peace, thak you very much for the extremely intresting link you posted, I'm having great fun (and enlightenment) in reading it!