Two Historical Firing Methods: Ausdampfverfahren and Auswanderungsverfahren

[derstosstrupp]

Hi All,
Introducing two firing/data acquisition methods which, after repeated tests using the torpedo tutorial in the academy, have proven to be successful and are 100% historically accurate, which ought to make other fellow “targeting realism” die-hards grin. I am using NYGM with Hitman’s GUI.
These methods are:

1. Ausdampfverfahren - (constant bearing to target)
a. Advantages/Requirements:
i. requires no estimate of target AOB or speed prior to firing
ii. requires only maintaining a constant bearing (collision course) and knowledge of own speed
iii. requires range estimate to correct for parallax prior to shot, but can be roughly estimated
iv. can use to derive target speed with solid knowledge of AOB
b. Disadvantages:
i. not optimal when target AOB is small when on collision course due to small target presented for the torpedo
ii. less accurate than plotting during the overhaul maneuver, and is thus best used when encountering the target forward of the beam (say at 45 deg AOB or so)
iii. should not be used for night surface attacks, as Hundekurve (dog’s course, keeping bow to target) should be followed to minimize sub silhouette.

2. Auswanderungsverfahren - (change in bearing of target over 1 minute)
a. Advantages/Requirements:
i. requires no estimate of target AOB or speed prior to firing
ii. requires one rough range estimate, own speed, and the bearing change of target over 1 minute
iii. requires final range estimate to correct for parallax prior to shot, but can be roughly estimated
iv. can be used at long distances during the overhaul maneuver to obtain rough speed with a rough idea of target AOB without slowing and thus losing time in overhauling
v. can be used to derive actual target speed with solid knowledge of AOB
vi. allows more freedom of maneuver than Ausdampfverfahren as no requirement to keep a constant target bearing, and thus can be used for night surface attacks
b. Disadvantages:
i. Less accurate than the Ausdampfverfahren and plotting during the overhaul maneuver, and is thus best used when encountering the target forward of the beam (say at 45 deg AOB or so)
ii. not optimal when target AOB is small due to small target presented for the torpedo and need for appreciable bearing change

Of course, the results of either method are only valid if the target maintains course and speed. For both methods, a scientific calculator with trig functions (otherwise known as your WO standing near you working the slide rules) is also necessary.

I will preface this by saying that by no means are these original ideas; these methods are historical and come from the Torpedo-Schießvorschrift (torpedo firing provisions) from 1930. I credit my knowledge of these methods to the gentleman who put together this site:

http://www.tvre.org/en/acquiring-torpedo-firing-data

This site outlines the ins and outs of the real-life Torpedo-Vorhaltrechner (German TDC) as well as other ancillary information and is a must-read for all who haven’t yet. The page linked above details the methods of acquiring firing data and includes the methods I will be demonstrating below. Thus, I am merely compiling these methods below in a thread for ease of reference and implementation into SH3.

I will discuss each method in a separate post to follow. :salute:

[derstosstrupp]

Step 1:
Gain position forward of enemy’s beam. Submerge once a position sufficiently forward of the target’s beam has been achieved. Otherwise, at larger AOBs, a constant bearing may not be possible due to the low underwater speed of the sub. Not too far forward, however, that the target presents too sharp of an AOB – your eels will then have little surface area of the target to impact.

Step 2:
Achieve a collision course to target by either adjusting own speed or turning to or away so that the target bearing does not change.

Step 3:
Ideally, maintain this constant bearing for a period of 10-15 minutes, preferably the 10-15 minutes up to firing. 10-15 minutes allows you be sure you are truly on a collision course, however in practice you could get by with much less, perhaps 3-4 minutes. Use this time to set up your eels for firing (depth, pistol, outer doors etc).

Step 4:
Set up TDC for the shot.
1. With scope pointed at the target (collision bearing you’ve been hopefully maintaining), set AOB in TDC to 90 starboard or port based on the direction of the target’s bow.
2. Compute speed for the TDC as follows:
a. Own speed x sin(target bearing) = target speed to input into TDC. Remember, this is degrees from the bow, so if she’s constant at bearing of 330, the target bearing for this formula is 30!
3. Immediately prior to firing, obtain a range estimate and input into the TDC. Now toggle TDC to auto. This is a must to correct for parallax, or the error caused by the fact that you are not shooting torpedoes out of the lens of your periscope, unless of course the gyro angle is within 10 degrees or so of your bow, in which case parallax error is moot. Use whatever your GUI offers. I use Hitman’s top-notch GUI and thus only estimate using the scope reticles. This is more than sufficient. Just know that errors due to inaccurate range will be more pronounced the closer you are and the larger the gyro angle. Alternatively, you could start a turn toward the target once you obtain the gyro angle for the shot and pull the trigger once your bow crosses the zero gyro angle bearing, thus eliminating the need for the torpedo to turn and the need for a range estimate, but I have found this a bit unwieldy in practice.

Step 5:
Once at a good firing range, fire!

Nary was a mark or line or angle drawn on the map throughout this whole process. No information was needed from the rec manual either, although a rough knowledge of the target’s mast height is needed for a range estimate if at large gyro angles.

Below is a video demonstration of this method:
https://www.youtube.com/watch?v=Pc42omH5iio

[derstosstrupp]

A note to modders/tech-savvy folks: The tvre.org site I linked above in the first post has an example of the slide rule for this method (see part about Auswanderungsverfahren “B”, toward bottom of page). It is relatively self-explanatory how this slide rule is used once you understand the guts of the calculation. Makman had mentioned in a post I’d seen about the desire to implement this slide rule in-game. I second that!

Step 1:
Gain position forward of enemy’s beam. Submerge once a position sufficiently forward of the target’s beam has been achieved. Otherwise, at larger AOBs, approach may not be possible due to the low underwater speed of the sub. Not too far forward, however, that the target presents too sharp of an AOB – your eels will then have little surface area of the target to impact.

Step 2:
Once you’ve nearly closed to firing distance, jot down your own speed (Ve), estimate range to target (E) and note the target’s bearing (b1). Start stopwatch. Do not alter own speed! The rest of this method only takes a couple minutes before firing, and so keep that in mind with respect to “nearly closed to firing distance”.

Step 3:
Once exactly one minute has passed, stop the stopwatch and note the new target bearing (b2). Do not move scope from this bearing until you fire for the rest of the method!

Step 4:
With scope pointed at (b2), set AOB in TDC to 90 starboard or port based on the direction of the target’s bow.

You now have 4 pieces of information noted: own speed (Ve), first bearing (b1), range at first bearing (E) in hectometers (this is important – take your range and divide by 100 and use this figure in the calculations), and second bearing (b2). Remember, this is degrees from the bow, so if she’s at bearing of 330, (b2) for this formula is 30! The change in bearing (b2-b1) we will call (w). Time to crunch numbers (in other words, time for your trusty WO to start spinning those slide rules, and thus pause is fine until you become proficient). Items in parentheses above are used to denote items in the formulas below.

Step 5:
Compute speed for TDC.
1. (Ve) x sin(b2) = (Vk). This represents the speed to input to the TDC IF WE WERE ON A COLLISION COURSE. We are not – the bearing is changing and thus we need to apply a correction:
2. (E) x 3.2967 x sin(w) = (d). Remember to convert your range (E) to hectometers by dividing by 100! The 3.2967 factor is to correct from metric to nautical miles since the correction (d) is in knots.
3. (Vk) +/- (d) = speed to input into TDC. If sub and target bows going in the same direction and the bearing change showed the target pulling ahead, you will ADD correction (d) to (Vk). SUBTRACT if sub and target bows are going the opposite directions, or if you are gaining on target (bows in same direction).

Step 6:
Obtain a final range estimate and input into the TDC (easily estimable since you got (E) already, just use judgment as to what the firing range would now be a minute or so later). After inputting, you should still be on (b2). This is a must to correct for parallax, or the error caused by the fact that you are not shooting torpedoes out of the lens of your periscope, unless of course the gyro angle is within 10 degrees or so of your bow, in which case parallax error is moot. Use whatever your GUI offers. I use Hitman’s top-notch GUI and thus only estimate using the scope reticles. This is more than sufficient. Just know that errors due to inaccurate range will be more pronounced the closer you are and the larger the gyro angle. Alternatively, you could start a turn toward the target once you obtain the gyro angle for the shot and pull the trigger once your bow crosses the zero gyro angle bearing, thus eliminating the need for the torpedo to turn and the need for a range estimate, but I have found this a bit unwieldy in practice.

Step 7:
While still on (b2), toggle TDC to auto, reacquire target and fire! You’re already at a good firing range. That is a benefit of this method – it is very quick once you get the hang of the calcs, all done immediately prior to firing.

There are also other handy uses for the Auswanderungsverfahren method, such as at long distances during the overhaul maneuver to obtain rough speed with a rough idea of target AOB without slowing and thus losing time in overhauling. In time, and if interest is shown by the community, I will post.

Below is a video demonstration of this method:
https://www.youtube.com/watch?v=pylYxlBkgfk

Enjoy and gute Jagd!

[Aktungbby]

derstosstrupp!http://www.fernglasmuseum.at/gaestebuch/images/smileys/acllamer.gif:salute: After a two year silent run... Ausdampfverfahren und Auswanderungsverfahren! :salute: Jawohl!

[CybrSlydr]

Great post!!!

[sublynx]

I hail thee, Sir :salute:

I'll make a TGA or two about these methods, edit them into my SH3, and wait for the lucky day when the kids are old enough to hang around with their friends all the time - and then I'll have a blast learning these new - I mean old, but authentic - techniques :woot:

[scott_c2911]

Its a good post but I feel once the game is up and they start zig-zagging these methods will throw a few errors in. Educated guessing at that point is still a good method lol.

[danasan]

Tutorial of the year! Thanks a lot, mate.

[derstosstrupp]

Its a good post but I feel once the game is up and they start zig-zagging these methods will throw a few errors in. Educated guessing at that point is still a good method lol.

Absolutely valid point, Scott. For the Ausdampfverfahren in particular, as that requires a steady target course and speed over time to establish a collision course. These methods are really best suited against loner merchants that infrequently zig while you are undetected, however Auswanderungsverfahren could be suitable for convoys as the procedure is done immediately prior to firing. That said, hopefully one would already have convoy speed from the overhaul maneuver or contact reports!

[Aktungbby]

Educated guessing at that point is still a good method lol.AuswanderungsverfeuernaufdemFlügel :o :Kaleun_Periskop:

[Magic1111]

@ derstosstrupp

Is it possible that you post all three posts in german words too? You are a german speaker, or? :hmmm:

For me it's too much English text to understand....:oops:

[derstosstrupp]

@ derstosstrupp

Is it possible that you post all three posts in german words too? You are a german speaker, or? :hmmm:

For me it's too much English text to understand....:oops:

Gruß Magic,

Kann ich! Deutsch ist für mich Zweitsprache, habe ich als Kind gelernt. Das sollte mich aber nicht daran hindern, das alles zu übersetzen. Wird flott gehen, wenn ich mal Zeit habe. Das kann ich auf jeden Fall diese Woche machen.

Gute Idee! Würde doch ein Verbrechen sein, diese Methoden deutschen Gehirnen geheim zu halten, da sie schließlich auf deutsche Gehirne zurückzuführen sind!

[Magic1111]

...
Gute Idee! Würde doch ein Verbrechen sein, diese Methoden deutschen Gehirnen geheim zu halten, da sie schließlich auf deutsche Gehirne zurückzuführen sind!

Vielen Dank, freue mich sehr! :yeah:

:salute:

[Magic1111]

Again @ derstosstrupp

Maybe you can post the german words manual here in the german subforum:

http://www.subsim.com/radioroom/forumdisplay.php?f=252

:salute:

[derstosstrupp]

Auf Deutsch stehen die obigen Verfahren jetzt auch zur Verfügung!

http://www.subsim.com/radioroom/showthread.php?t=222400

[Pisces]

I tried to suggest this method (Ausdampfverfahren) in the 80-10 rule thread that went sour years ago, or atleast something like it:

http://www.subsim.com/radioroom/showpost.php?p=1464472&postcount=5

I'm glad to know the Germans actually had this as a valid tactic and had a name for it.

:yeah:

[Magic1111]

Auf Deutsch stehen die obigen Verfahren jetzt auch zur Verfügung!

http://www.subsim.com/radioroom/showthread.php?t=222400

Wonderful, many thx!!! :yeah:

:salute:

[derstosstrupp]

I tried to suggest this method (Ausdampfverfahren) in the 80-10 rule thread that went sour years ago, or atleast something like it:

http://www.subsim.com/radioroom/showpost.php?p=1464472&postcount=5

I'm glad to know the Germans actually had this as a valid tactic and had a name for it.

:yeah:

I remember that thread. It was.......epic. Everything that could go wrong did go wrong.

[Fahnenbohn]

Would it be possible to make a video for each method, please ?

[LGN1]

Hi,

the English version says 'Now toggle TDC to auto.'The German version says 'Vorhaltrechner ausschalten'.

I think this is a contradiction or what do you mean with 'TDC to auto'?

Regards, LGN1

[derstosstrupp]

Would it be possible to make a video for each method, please ?

Hi Fahnenbohn,

I will certainly try my best. I'm not the savviest, but I think these methods deserve a video or two.

[derstosstrupp]

Hi,

the English version says 'Now toggle TDC to auto.'The German version says 'Vorhaltrechner ausschalten'.

I think this is a contradiction or what do you mean with 'TDC to auto'?

Regards, LGN1

LGN1,

By that I mean switch the TDC like you would normally do after inputting data prior to the shot (so that the gyro angle, AOB etc updates upon moving the scope).

[Hitman]

Fantastic tutorial :up:

A video would be the icing on the cake for new skippers, but what you did already warrants a Ritterkreuz. Salute!!! :salute:

[Fahnenbohn]

Hi Fahnenbohn,

I will certainly try my best. I'm not the savviest, but I think these methods deserve a video or two.

That would be so cool, mate ! :yeah:

[LGN1]

LGN1,

By that I mean switch the TDC like you would normally do after inputting data prior to the shot (so that the gyro angle, AOB etc updates upon moving the scope).

Thanks for the clarification, derstosstrupp.

In this case I think you should correct the German version to something like 'Vorhaltrechner einschalten' or 'Vorhaltrechner aktivieren'.

Regards, LGN1

[derstosstrupp]

Thanks for the clarification, derstosstrupp.

In this case I think you should correct the German version to something like 'Vorhaltrechner einschalten' or 'Vorhaltrechner aktivieren'.

Regards, LGN1

Thanks for the feedback LGN1, done.

[sublynx]

http://i.imgur.com/jDb2UF7.jpg

Is it ok to release this as a TGA so that players who want to edit this into their SH3 mod soups can have the instructions inside their games? I would also like to edit this into my CAWS 1.6 mod, (if and when I get the time and energy to finish a new version of it), if that's ok to you?

[Aktungbby]

^ that looks GOOD!:up:

[derstosstrupp]

http://i.imgur.com/jDb2UF7.jpg

Is it ok to release this as a TGA so that players who want to edit this into their SH3 mod soups can have the instructions inside their games? I would also like to edit this into my CAWS 1.6 mod, (if and when I get the time and energy to finish a new version of it), if that's ok to you?

Yes! That looks amazing - by all means!

[sublynx]

Cool!

I'm glad you two like it :)

The TGA can be found here:

http://www.mediafire.com/download/kv348auu6vme4zl/auswanderungsverfahren.tga

[sublynx]

http://i.imgur.com/orEgwfR.jpg

And here's the link to the TGA with the Ausdampfverfahren method:

http://www.mediafire.com/download/sp9evaz8qzsp1ms/ausdampfverfahren.tga

[derstosstrupp]

All,

I have posted video demonstrations of the Ausdampfverfahren and Auswanderungsverfahren, see links at bottom of second and third posts.

[Tycho]

How to calculate Ausdampfverfahren with my DR Slide Rule mod!

Place your speed under 90°, read target speed for the TDC opposite to target bearing.

First example from derstosstrupp video:
3.5 x sin(69.5°) = 3.2783
http://oi65.tinypic.com/mu7ion.jpg

Second example from derstosstrupp video:
4.2 x sin(54°) = 3.3978
http://oi68.tinypic.com/2vjwobr.jpg

[sublynx]

Thanks Tycho, I wouldn't have figured that out by myself, I would have just wasted time picking up a calculator, when all I really need is one click to slide out your slide rule, and one sliding movement to match my speed with 90 degrees. Then I just look what the result is.

Doing this with a calculator would have required me to push a calculator button 10 times AND getting my eyes off the game. The slide rule way is 5 times less the work and unhindered concentration on the game :D

[derstosstrupp]

How to calculate Ausdampfverfahren with my DR Slide Rule mod!

Place your speed under 90°, read target speed for the TDC opposite to target bearing.

First example from derstosstrupp video:
3.5 x sin(69.5°) = 3.2783
http://oi65.tinypic.com/mu7ion.jpg

Second example from derstosstrupp video:
4.2 x sin(54°) = 3.3978
http://oi68.tinypic.com/2vjwobr.jpg

Tycho,

This is outstanding. I've added this to my game. "Target speed" for both Ausdampfverfahren and Auswanderungsverfahren can be computed using this, and, as sublynx said, no need to get eyes off game.

Well done!

[ThaineFurrows]

Great post,

One question though. I try to figure out the maths behind it. Why do you use a AOB of 90? Wouldn't you require the actual AOB?

[Aktungbby]

ThaineFurrows!:Kaleun_Salute:

[Jimbuna]

Welcome to SubSim Thaine :sunny:

[Von Due]

Just tried my 2nd attempt at the Auswanderungsverfahren method and whoah, I think this is one method to keep. First attempt I botched up but the 2nd hit home. Took a bit of studying the video and I wrote down on paper my own version of the steps for quick reference.

Two things I wonder about:
Is this method dependent on fast setting for the torpedo or will it work equally well on any speed setting?

Where does the number 1820 come from? I understand it's there to convert from metric to nautical units but 1820 is not a number that rings any bell. I was expecting 1852 but for some reason, 1820 seems to work splendidly.

[derstosstrupp]

Been away for a while, but since returned. I have since fleshed out the Auswanderungsverfahren In a comprehensive guide which I have linked to my signature. Hopefully this is helpful in guiding folks through an engagement from A-to-Z, in a manner that seems to be historical based on what I’ve read.

A 90° AOB is used in the Ausdampfverfahren Due to the convenience of the sine of 90 being 1 - Makes the calculation more straightforward. Also, the method can be used with any speed setting, as you are still reliant on the TDC To set the shot up.

[rainiere]

Been away for a while, but since returned. I have since fleshed out the Auswanderungsverfahren In a comprehensive guide which I have linked to my signature. Hopefully this is helpful in guiding folks through an engagement from A-to-Z, in a manner that seems to be historical based on what I’ve read.

A 90° AOB is used in the Ausdampfverfahren Due to the convenience of the sine of 90 being 1 - Makes the calculation more straightforward. Also, the method can be used with any speed setting, as you are still reliant on the TDC To set the shot up.

Good stuff, thanks!

[John Pancoast]

(old thread reborn). Good method, but only for submerged attacks due to exposing your side profile to the target resulting in a high chance of being spotted in a surface attack.

[derstosstrupp]

(old thread reborn). Good method, but only for submerged attacks due to exposing your side profile to the target resulting in a high chance of being spotted in a surface attack.

Very true! Check out my comprehensive Tutorial, that has recommendations for night attacks as well as incorporating these methods.

[John Pancoast]

Very true! Check out my comprehensive Tutorial, that has recommendations for night attacks as well as incorporating these methods.

Yes, been following your links. Outstanding, thanks for the work !

[John Pancoast]

Hi again;
Been reading your "Comprehensive......" work. Question: On the overhaul, you state get to the point where the target indicates 0 aob.
My understanding of 0 degrees aob would mean the target's bow would be pointing directly at either my bow or my stern; either is 0 aob.
Is this your interpretation also ?

[derstosstrupp]

Hi again;
Been reading your "Comprehensive......" work. Question: On the overhaul, you state get to the point where the target indicates 0 aob.
My understanding of 0 degrees aob would mean the target's bow would be pointing directly at either my bow or my stern; either is 0 aob.
Is this your interpretation also ?

Hi John,

Thanks for taking the time to read through the tutorial. 0 AOB is the moment the target is pointing directly at you, i.e. the moment you cross his track. If he is pointing directly away from you he is at a 180 deg AOB. In other words, AOB is the the bearing to your boat if you were standing on the deck of the target.

[John Pancoast]

Hi John,

Thanks for taking the time to read through the tutorial. 0 AOB is the moment the target is pointing directly at you, i.e. the moment you cross his track. If he is pointing directly away from you he is at a 180 deg AOB. In other words, AOB is the the bearing to your boat if you were standing on the deck of the target.

Great, thanks again.

[makman94]

hello Derstosstrupp,
I was looking at these two presentations and i want to ask you something


at this point of first presentation, i think that i am missing it.

......
Step 4:
Set up TDC for the shot.
1. With scope pointed at the target (collision bearing you’ve been hopefully maintaining), set AOB in TDC to 90 starboard or port based on the direction of the target’s bow.
How do you know that, at this bearing (collision bearing you’ve been maintaining), the AoB is always 90° ?

Look at the following pic (the spoken AoB at this bearing can be anything else):

http://i68.tinypic.com/wlrsz5.jpg

how can be ignored the above and consider the AoB to be always at 90° at this bearing? what am i missing here ?



ps: Therefore, for calculate target speed:

target speed = [Own speed / sin(AoB)] x sin(target bearing)



.....
Step 4:
With scope pointed at (b2), set AOB in TDC to 90 starboard or port based on the direction of the target’s bow.
....
Same question for the second presentation

[derstosstrupp]

Hi Makman,

This post is back when I was using these methods as shooting methods, that is, to derive a gyro angle. I now use these methods to derive target speed (see my stuff in my sig as well as this that I made for Wolfpack https://drive.google.com/file/d/1isfQl8qNPl0wlHG8HsS661YIG2PyyFFq/view?usp=drivesdk. That is a more evolved way of using the methods and is more in line with historical procedures.

To your question, the setting of 90 is simply for simplicity’s sake. Setting 90 allows you to set the target speed = own speed in the TDC, that’s all. Since the formula is

own speed x sine(brg) / sine(AOB) = target speed,

Then setting TDC speed to equal own speed yields the same result since the sine of 90 is 1.

Again, antiquated method and superseded by my subsequent stuff.

[makman94]

.....

To your question, the setting of 90 is simply for simplicity’s sake. Setting 90 allows you to set the target speed = own speed in the TDC, that’s all. Since the formula is

own speed x sine(brg) / sine(AOB) = target speed,

Then setting TDC speed to equal own speed yields the same result since the sine of 90 is 1.

Again, antiquated method and superseded by my subsequent stuff.


i see , thank you for the reply Derstosstrupp :Kaleun_Salute:

[derstosstrupp]

i see , thank you for the reply Derstosstrupp :Kaleun_Salute:

No problem Makman, thank you for all your great work all these years!:Kaleun_Salute:

[Pisces]

In so far as it isn't clear yet (to other readers), I think this image may clarify why you set AOB to 90 degrees when looking to the target, and use ownspeed*sin(constant_bearing) as target speed.

http://ricojansen.nl/image/intercept_angles2.JPG

As far as the TDC is concerned when the bearing is fixed to the target, to know the torpedo lead-angle it only needs to know what that sideways speed is perpendicular to the target bearing. Hence why you set the AOB to 90, and target speed to ownspeed*sin(constant_bearing). The TDC will calculate the lead angle for the torpedo by taking a right-angled triangle with that sideways-speed as opposing side, and the torpedo speed as the hypotenusa. So torpedo lead-angle will then be:
arcsin( ownspeed * sin(constant_bearing) / torpedospeed )
And then further corrections for gyro-angle parallax based on (rough) range.


The real target speed and actual AOB isn't so important to get the torpedo on the target as it will only provide additional information on the speed components along the line of bearing. This will only tell the closure rate of the torpedo to the target, Read: correct time to impact. The time to impact calculated by the TDC cannot be relied upon in this Ausdampfverfahren setup. Without knowing the actual AOB and speed, the torpedo would be lead onto the target anyway. (assuming measurements are exact without error) The idea behind the Ausdamphverfahren is to fire as soon as this constant bearing is established and the calculation of the sideways speed is done. Or whenever you got up to a sufficiently close range.

If you want to fire on a different bearing to another target (than the one on the established constant bearing) at a later point. Then you need to have the scope on the established constant bearing, correct target speed to the real target speed based on the observed AOB (targetspeed = 'sideways speed' / sin(observed_AOB) ) and set the observed AOB in the TDC. Now the TDC is calibrated to aim wherever with proper torpedo lead. (As long as range is entered appropriate to the target) This was explained in derStosstrupp's documents too iirc.

[Drakken]

Probably a stupid question, but what is the overhaul maneuver? :oops:

[John Pancoast]

Probably a stupid question, but what is the overhaul maneuver? :oops:

When you're getting in front of, or "overhauling" a convoy/ship.

[Drakken]

When you're getting in front of, or "overhauling" a convoy/ship.

Got it now, thanks!

For the first method, how do you usually proceed with acquiring a collision course? Do you go by first adjusting your boat's course port or starboard, until the bearing remains constant, then trim slightly as you proceed or is there a formula that can be used which assigns a probable bearing difference between the two ships' bow, for a given target speed?

What do you do if the bearing suddenly changes by 1-2 degrees after more than 15 minutes? For example, in situations in which you are intercepting a target by hydrophones over long range.

[John Pancoast]

Got it now, thanks!

For the first method, how do you usually proceed with acquiring a collision course? Do you go by first adjusting your boat's course port or starboard, until the bearing remains constant, then trim slightly as you proceed or is there a formula that can be used which assigns a probable bearing difference between the two ships' bow, for a given target speed?

What do you do if the bearing suddenly changes by 1-2 degrees after more than 15 minutes? For example, in situations in which you are intercepting a target by hydrophones over long range.

I keep it simple. No math, no formulas, etc. Just keep a visual on them, and when the ship/masts are barely in view, that's where I want them.
So I adjust my course accordingly to keep it that way.

I don't intercept via hydrophones, sorry. Maybe someone else can help there.

[Pisces]

The bearing accuracy is not good enough to do this by hydrophone. Visual sighting by periscope or UZO line is required.

I'm at work now replying on my phone. It is hard to describe the method I have in mind. Will do later today.

Derstosstrup did make videos with wolfpack showing the procedure some months ago.

[derstosstrupp]

Got it now, thanks!

For the first method, how do you usually proceed with acquiring a collision course? Do you go by first adjusting your boat's course port or starboard, until the bearing remains constant, then trim slightly as you proceed or is there a formula that can be used which assigns a probable bearing difference between the two ships' bow, for a given target speed?

What do you do if the bearing suddenly changes by 1-2 degrees after more than 15 minutes? For example, in situations in which you are intercepting a target by hydrophones over long range.

This is simply trial and error. I found it best to first adjust your speed until the bearing just barely changes and then fine-tune it with course changes. It really only needs to be held constant over the course of a few minutes. Also, just be aware of that the closer you are to a 90° angle on bow, The more accurate the results, since the formula divides by the sine of the angle on bow, and the further away you are from 90° the more effect small AOB estimation errors will have.

I use these methods primarily for finding target speed, whereas when I first made this post it was a way to calculate a Gyro angle for purposes of shooting, but using it to compute speed is much more useful.

[Pisces]

The method I had in mind this afternoon was by recording own movement while on a constant course, but with changing speed faster then slower. One has to record one's own position on the map, point the scope to a fixed point on the target hull, be at an overtaking speed making the target creep backwards, and at some time slow down letting the target catch up to the line. Then the distance own ship moved over the time until it catches up gives you your average speed. With own ship and the bearing of the scope being constant, the target returning to the line as it catches up is effectively a constant bearing at two moments in time. And since the scope bearing and own course is kept constant you can easily calculate your speed component across the line of sight by multiplying it by the sine of the bearing. As shown in my image above, this is the same as the 'speed across' of the target. Then the real target speed results from dividing it by the sine of the AOB.

For the Wolfpack game this should work out nicely (barring the current time-dilation bug), since you can easily record your own movement by the difference in the odometer value at both times down to the meter. But I forgot that in SH3 you can't measure distance as precisely. You are limited to the 100m units that is displayed by line length or circle radius. The latter would require longer time periods to get any meaningful precision in the average speed. Trial and error as derstosstrup advocated is then easier and better done in reasonable time.

I can't remember. Does SH3 have an odometer? If so, probably a crude scale though.

[Drakken]

Another question : is there a "maximum bearing" in the Ausdampfverfahren method?

For example, in one of my attack due to the target both "moving away" from me on his course and both our difference in speed my bearing was remaining constant at 40-42 degrees. But, from what I understand the wider the gyro angle, the higher the risk of the torpedo missing its target. Am I wrong in thinking that?

[Pisces]

There is a maximum bearing in the sense that larger and lower than 90/270 bearing produce less of a speed component across the line of sight. With the target on your beam (90 degrees to your bow) the speed component across the line of sight is the largest. So if your speed is not sufficient to match the 'speed across' of the target while it is on that bearing then you'll never get a constant bearing. It's going to outflank you and the bearing to the target will slowly drift to your bow.

The target speed across the line of sight are equal for AOBs that are equally far from 90. So a target closing with AOB 60 will provide the same speed across the line of sight as it would with 120 degrees moving away. AOB 30 would be equally fast as AOB 150 moving away. The difference with less than 90 degrees AOB, as opposed to larger than 90 AOB, is that the 'lesser' will have the bearing drift rate increase due to closing distance. Whereas the 'larger' will have this drift rate slowing down, due to increasing distance. So if you cannot match the speed of the target across the line of sight when it is on 90 then you should find other ways to speed up or forego this method. Then the Auswanderungsverfahren will work better, as it relies on the bearing drift to get a result.

As far as gyro angle goes, I do not immediately see your point with the later part of your example. A wide gyro angle does require a roughly accurate range setting. But only at the closest of ranges will this torpedo turn parallax will it have the largest effect. At close range the target appears the largest in size, so it wil somewhat mitigate theses chances for a hit. But I would not fire without some roughly accurate value for range to correct for the torpedo turn offset curve.

P.S. A bearing on 40-42 is not constant. I doubt you had a constant bearing solution for this method to work. Also a moving away AOB is a clear indication you are firing from a disadvantageous position. You better re-position yourself for attack.

[derstosstrupp]

Another question : is there a "maximum bearing" in the Ausdampfverfahren method?

For example, in one of my attack due to the target both "moving away" from me on his course and both our difference in speed my bearing was remaining constant at 40-42 degrees. But, from what I understand the wider the gyro angle, the higher the risk of the torpedo missing its target. Am I wrong in thinking that?

If you are shooting with a gyro angle appreciably away from 0, say outside 20 degrees or so, an input for range becomes necessary to correct for parallax (the effect of the distance the torpedo travels before turning and the overall turn radius, in other words for the fact you aren’t shooting out your periscope). To do this Ausdampfverfahren As a shooting method, therefore you need to turn until the Gyro angle is close to zero.

The more practical application of this method though is simply using it to compute target speed. So instead of setting AOB to 90 and TDC speed to your speed, you simply establish the constant bearing, then multiply own speed by the sine of that constant bearing divided by the sine of the angle on bow and you’ve got target speed. Albeit that requires an AOB estimate.

The disadvantage of using this purely as a shooting method to derive a gyro angle to turn to is the fact that it’s only valid at that AOB. As soon as the target’s angle on bow starts growing the solution becomes invalid, so you need to turn quickly to that zero gyro and shoot in order for this to work.

[derstosstrupp]

Pisces I now see you’d already posted. Great explanation!:Kaleun_Cheers:

[La vache]

If you are shooting with a gyro angle appreciably away from 0, say outside 20 degrees or so, an input for range becomes necessary to correct for parallax (the effect of the distance the torpedo travels before turning and the overall turn radius, in other words for the fact you aren’t shooting out your periscope). To do this Ausdampfverfahren As a shooting method, therefore you need to turn until the Gyro angle is close to zero.


There is no reason to forego a gyro angle greater than zero degrees.
If you do not calculate the distance to the target for parallax correction with TDC, the parallax is compensated with the hit point at the target. There were tables with indication of shooting angle and target direction for parallax correction.
You can find it in my video:
Torpedo shot without fire control system.


https://www.youtube.com/watch?v=H2lxmdZvqHI

[derstosstrupp]

There is no reason to forego a gyro angle greater than zero degrees.
If you do not calculate the distance to the target for parallax correction with TDC, the parallax is compensated with the hit point at the target. There were tables with indication of shooting angle and target direction for parallax correction.
You can find it in my video:
Torpedo shot without fire control system.


https://www.youtube.com/watch?v=H2lxmdZvqHI

You are certainly correct. U-boat commanders handbook gives a value for an aimoff correction of 50m for a 45 degree angled shot. Woukd be greater for a 90 degree angled shot of course. Thanks for pointing that out!

[Drakken]

The bearing accuracy is not good enough to do this by hydrophone. Visual sighting by periscope or UZO line is required.


Shoot... I am currently on a bad weather stretch right now, so most of my interception are through hydrophones until I reach a visual of < 1000 meters.

[Pisces]

Shoot... I am currently on a bad weather stretch right now, so most of my interception are through hydrophones until I reach a visual of < 1000 meters.Well, you can do a makeshift intercept with the ausdampfverfahren just to get in range. Since you cannot see the target you cannot measure the AOB. So you cannot figure out it's actual speed and course. But if you try to manoeuvre your boat to get the target on a constant true bearing (heading) you have made your intercept. So at each hydrophone check look up the bearing on the white ring of the station, or add relative bearing to current course. Chase the target bearing drift until it is constant. If the bearing drifts away from course, turn towards it a bit. If it draws to your course, turn away a bit.

You wouldn't want to do this submerged for the hole run. Your batteries would be dead before you make visual contact. (aside from that it would take ages and may never even happen) Surfaced with own speed at 18 kts you only need to lead your course by 30 degrees max for the faster targets/convoys (9kts). Proportionally less for slower targets if you expect that to be the case. Doing hydrophone checks will slow down your average speed of course. So you may need to adjust for that. lead_angle= inverse_sine( expected_target_speed/average_own_speed) But with the distances in Wolfpack (edit: whoops, I forgot this is in the SH3 section) involved you may not need to do many hydrophone checks.

Still, shooting torpedoes based on that is out of the question. The range is too far and you can't see what you are aiming at. Besides, you don't know yet if it is moving away or towards you.

[Jojojung]

In the video to the "Ausdampfverfahren" below there are no calculation with sin. The own speed represents the target speed. Here its juts the own bearing from bow = AOB.

So with the formula it would be: Vt = 4 kt x sin(52°) / sin (52°)
So simplyfied its own speed = target speed when you are on a collision course

Why does this simplyfication work? And why should you use the formula instead?






https://www.youtube.com/watch?v=jLTkxym1y9s

[derstosstrupp]

Two ways to go about it:
1. You can set the angle on bow to 90 right or left, the consequence of this being of course that you need to multiply your own speed by the sine of the bearing, setting that as the speed.

2. Do as in the video here, which is probably easier to be honest, and that is to set your own speed as target speed, and set the angle on bow to the bearing.

In number 2, you are letting the TDC do the trig for you.

Target speed = own speed x sine (bearing) / sine (AOB)

So you can see by that formula, since the sine of 90 = 1, why you would need to do the math for number 1. In number 2 what you are doing is setting AOB equal to the bearing, therefore eliminating that side of the equation ( sin(brg) / sin(AOB) then = 1) so you are left simply with own speed = target speed.

But let’s take a step back. This method is good and it can be used in a pinch, but it’s not perfect since you need to be at a relatively small angle on bow in order to achieve the constant bearing if approaching underwater.

A much better use for the above formula is actually on the surface after you first sight the target. Turn to what you think is parallel, and adjust own course and speed at long range until the bearing doesn’t change over a few minutes, estimate the angle on bow, then apply the formula. Then once you get a better appreciation for the course, refigure what the AOB would’ve been, go back and drop that AOB into the original formula and voila - target speed by Ausdampfen, just like in the KTBs!

Edit: Forgive me because I see you realized the same thing about that side of the equation falling off. Use method 2, it’s easier if you’re going to use this method for shooting.

[Jojojung]

Two ways to go about it:
1. You can set the angle on bow to 90 right or left, the consequence of this being of course that you need to multiply your own speed by the sine of the bearing, setting that as the speed.

2. Do as in the video here, which is probably easier to be honest, and that is to set your own speed as target speed, and set the angle on bow to the bearing.

In number 2, you are letting the TDC do the trig for you.

Target speed = own speed x sine (bearing) / sine (AOB)

So you can see by that formula, since the sine of 90 = 1, why you would need to do the math for number 1. In number 2 what you are doing is setting AOB equal to the bearing, therefore eliminating that side of the equation ( sin(brg) / sin(AOB) then = 1) so you are left simply with own speed = target speed.

But let’s take a step back. This method is good and it can be used in a pinch, but it’s not perfect since you need to be at a relatively small angle on bow in order to achieve the constant bearing if approaching underwater.

A much better use for the above formula is actually on the surface after you first sight the target. Turn to what you think is parallel, and adjust own course and speed at long range until the bearing doesn’t change over a few minutes, estimate the angle on bow, then apply the formula. Then once you get a better appreciation for the course, refigure what the AOB would’ve been, go back and drop that AOB into the original formula and voila - target speed by Ausdampfen, just like in the KTBs!

Edit: Forgive me because I see you realized the same thing about that side of the equation falling off. Use method 2, it’s easier if you’re going to use this method for shooting.




Thanks a lot!



Grüße aus Deutschland (Ich habe gesehen, dass du auch ganz gut deutsch kannst ;-)

[derstosstrupp]

Danke sehr! Fette Beute!:Kaleun_Cheers:

[olegst90]

Please could anybody explain how to do the math with attack disc? I can multiply the speed by sine of the angle, but not sure how to do the trick with 3.2967 thing in the second method.

[stellaferoxx]

I think there is an error in the formula which computes d.

It is stated as d = E (in hm) x 3.29 (6000/1820) x sin(w)

But E can be given in meters. The 6000 is really 60, one hour x this change of angle and 1820 should be 1852, which is one nautical mile, to get from meters to knots.

Therefore the formula should be (IMHO)

d = E (in meters) x 60/1852 x sin(w). The differences are very tiny though...