Constant Bearing Method, with TDC

[Rocks'n'Shoals]

Hello fellow captains,

I have newly subscribed, but have been eavesdropping as stowaway for a while now. I am actually an old hand in playing Silent Hunter. I have enjoyed them all: SH1, SH2, SH3 and SH4... Stock game in SH4, no mods yet.

I want to share the most accurate method for shooting torpedoes in SH4, American submarine, which I have come across so far. It is a constant bearing method which employs the TDC. Whenever I use it, and do everything right, I get sure hits, even with long-distance shots up to 4000 meters. I have also found it to work well for convoy surprise attacks. Last time I encountered a convoy, I got all 3 front row ships with my 6 bow torpedoes, they all sank...

Ok, here we go... I have included screenshots for clarification.

First thing to do when acquiring a new ship contact: Determining course and speed. I won't go into details here on how to do it, there are many well-documented methods plus it's easy when map contact updates are set to "on", but it has to be done with a high degree of accuracy for the constant bearing method to work out well.
Draw the enemy course line on the navigation map.

Second step: Choose your firing spot, somewhere near the target course line, wherever you like best. Go there, and stop the sub completely. We will stay here until after firing.

Third step: Choose the line of bearing for your attack. This is the constant bearing line which we will aim along later. Draw the constant bearing line on the nav map using the ruler. You get the distance from your sub to the target when it will be at the aiming point. This is not a critical measurement.

http://astro.nightsky.at/Download/ConstantBearing_1.jpg

3000m - is he kidding....? (I am playing with metric units here.)

Fourth step: Use the protractor tool to get the exact AoB.

http://astro.nightsky.at/Download/ConstantBearing_2.jpg

64 degrees starboard.

Fifth step: Now we need the angle between our heading and the constant bearing line for setting the periscope. Easy when you have a 360° Bearing Plotter, just read the scale on the constant bearing line. In the stock game, I don't have it, so I measure the absolute angle of the constant bearing line with the protractor tool.

http://astro.nightsky.at/Download/ConstantBearing_3.jpg

113 degrees, add 180 for left (western) side -> 293 degrees.

OK, now let's input all the data into the TDC. The Position Keeper remains off, we set up for a static solution. Don't forget to confirm each step by pressing the red "Send to TDC" button with the white triangle on it:

Target speed...

http://astro.nightsky.at/Download/ConstantBearing_4.jpg

Angle on Bow... (not easy to input exactly!)

http://astro.nightsky.at/Download/ConstantBearing_5.jpg

Target range... Read it on the PK

http://astro.nightsky.at/Download/ConstantBearing_6.jpg

OK, now set the periscope to the preselected constant bearing. I repeatedly press the "set heading to view" button for that. We won't turn because we don't move, but the chief executive will read you the absolute bearing you are looking at currently. I repeatedly try until it matches the absolute value of my constant bearing line - 293° in my case. Press the red triangle button on the TDC again to confirm it.

http://astro.nightsky.at/Download/ConstantBearing_7.jpg

(Note that the PK will now display the data you did enter - for example the AoB.)

Don't touch the periscope after you have done this! Its vertical line is now our well-aimed firing reticle. We will wait until the juiciest parts of the enemy ship cross it, and fire exactly then!

For now, let's wait submerged at periscope depth, periscope lowered, well hidden and silent until the enemy is where we want him - no need to expose the periscope until just before firing... We are playing now a big, silent hole in the water, but a hole with a well-aimed high-precision gun...

Now is a good time to open the torpedo tubes, go to silent running (without moving), and ring the bell for battle stations.

The nav map with its sound bearing lines is a good indicator when to raise the scope for the firing procedure.

http://astro.nightsky.at/Download/ConstantBearing_8.jpg

Up scope! Let the target steam into the firing reticle. Fire at will. I usually shoot two torpedoes, one into the foreship, one aft. Three torpedoes will do nicely for larger targets.

http://astro.nightsky.at/Download/ConstantBearing_9.jpg

Oh, a small Engine-Aft - I didn't look earlier, set it all up using radar data only...

http://astro.nightsky.at/Download/ConstantBearing_11.jpg

Both running straight and true. I love those Mk23's...

http://astro.nightsky.at/Download/ConstantBearing_12.jpg

Really? At 3000 meters...? :yep:

Additional comment: For a convoy attack, I use the same procedure, and set up for an average distance. Using an AoB between 60° and 80° (depending on target speed), I can fire at two or three ships which are aligned in a row, furthest first, nearest last, to time the torpedo impacts near-simultaneous. Let them run into the firing reticle, one ship after another, they are all traveling at the same course and speed - unless previously alerted, which is when they go into wild zigs...

Happy shooting! ;)

[Soundman]

Pretty impressive first post there. Welcome to the forums. :up:

I just tried your method, works very well. Pretty nifty trick using the heading to view while stationary. It does raise a question. Did real periscopes have the ability to know what direction (heading) they were looking in? It would seem so, as it would not have required anything difficult, just a compass on the scope. Otherwise, some might say "that a cheat", just curious.

[peabody]

Pretty impressive first post there. Welcome to the forums. :up:

I just tried your method, works very well. Pretty nifty trick using the heading to view while stationary. It does raise a question. Did real periscopes have the ability to know what direction (heading) they were looking in? It would seem so, as it would not have required anything difficult, just a compass on the scope. Otherwise, some might say "that a cheat", just curious.

Well, you know your heading by looking at the compass. You know the angle you want 293 degrees, so if you look at the picture where the 293 is circled that is about 22 degrees, look at the compass, it is NW, add 293 degrees plus 22 degrees, and you get NW. Or take your heading of NW subtract 22 degrees and get the 293 you want. So, I don't see it as cheating since you can calculate where the periscope is pointing just by knowing the heading of your sub.
I haven't tryed it, but if it works, great!! The only drawback I can see is if there are any DDs in the area and they are pinging, you don't want to sit in one spot. So you would need a Plan B.;)

Peabody

[Sledgehammer427]

yup, when i was really little, and i was making play attacks on passing ships in Groton @ the nautilus museum, I could almost sense what bearing i was looking in, just by the instant i started looking thru the scope, what direction i was facing...my stepdad used to call out bearings when I called "bearing...mark!"
its too bad im almost too old for that :rotfl:

EDIT: beautiful work, Rocks'n'Shoals, I shall try that next time the Scorp puts out

[AVGWarhawk]

Pretty impressive first post there. Welcome to the forums. :up:

I just tried your method, works very well. Pretty nifty trick using the heading to view while stationary. It does raise a question. Did real periscopes have the ability to know what direction (heading) they were looking in? It would seem so, as it would not have required anything difficult, just a compass on the scope. Otherwise, some might say "that a cheat", just curious.

If I'm not mistaken, the TBT and scope had a button that could update the heading.

[AVGWarhawk]

How are you changing that value on the PK for range?

[Rockin Robbins]

One deal-killer for me in your technique is your very first step: stop the boat. In real life you couldn't do that. Even on the surface, stopping loses all directional control of the sub. Under water it is even worse, as all depth-keeping and directional control are lost. Your entire technique relies on defects in the game physics model. Other than that, it's bulletproof!:up:

You know, there is no reason you have to stop your sub. Just throttle down to about a knot or a half a knot to begin with. Turn on the PK as you enter your parameters and use the present AoB of the target for this part. Calculate the AoB in your way for your intended shoot bearing for later. This will actually allow you use the attack screen to check your inputs of speed and target course for accuracy as the target cruises down the line. When the target is 5 or 10 degrees before the shoot bearing, turn off the PK, enter the AoB for the shoot bearing, sight on that bearing, press send range/bearing and just wait a few seconds for the target to pass through the crosshairs, shooting as juicy parts are in the sights. Your resulting dozen yards or so of range error won't mean a thing (range cancels out of any constant bearing attack anyway and is only important for correcting parallax errors with increasing gyro angles on the torpedoes).

NOW you have a realistic shooting technique!

Nisgeis is now going to jump on the thread with his method of vector analysis to do the whole shebang in seconds and you could shoot at full throttle if you wanted to. THEN you can throw the whole TDC overboard, as all it is is ballast!

[Rocks'n'Shoals]

One deal-killer for me in your technique is your very first step: stop the boat. In real life you couldn't do that. Even on the surface, stopping loses all directional control of the sub. Under water it is even worse, as all depth-keeping and directional control are lost.
True.
But there is an easy solution to that, if you want to play that realistic: A little time prior to shooting, ring up very slow speed for directional control. Correct your setup just before shooting. Target speed won't change, and range is not critical except when you are very close to your target. But you may have to to update the AoB and your periscope bearing. It helps if you move in the direction of the bearing line, then you probably won't have to update the AoB.

Other than that, it's bulletproof!:up:
Thanks, RR ;)

You know, there is no reason you have to stop your sub. Just throttle down to about a knot or a half a knot to begin with. Turn on the PK as you enter your parameters and use the present AoB of the target for this part. Calculate the AoB in your way for your intended shoot bearing for later. This will actually allow you use the attack screen to check your inputs of speed and target course for accuracy as the target cruises down the line. When the target is 5 or 10 degrees before the shoot bearing, turn off the PK, enter the AoB for the shoot bearing, sight on that bearing, press send range/bearing and just wait a few seconds for the target to pass through the crosshairs, shooting as juicy parts are in the sights. Your resulting dozen yards or so of range error won't mean a thing (range cancels out of any constant bearing attack anyway and is only important for correcting parallax errors with increasing gyro angles on the torpedoes).

I have tried that, and have not been satisfied with the accuracy I got, except if I actually stopped the time and entered an exact solution. But that would be unrealistic as well, wouldn't it?
But maybe I can work out a method along those lines which satisfies my ambition for long-distance killer shots ;)

Nisgeis is now going to jump on the thread with his method of vector analysis to do the whole shebang in seconds and you could shoot at full throttle if you wanted to. THEN you can throw the whole TDC overboard, as all it is is ballast!
Actually I find the TDC a very good and accurate tool, that is if you know what it does and how to use it correctly. Of course you could compute your solution with a separate calculator or plot a graphical solution on a sheet of paper, but why should I do so, if I have the calculator on board?

[Rocks'n'Shoals]

How are you changing that value on the PK for range?
It is updated by pressing the red triangle button on the stadimeter input of the TDC. If you are not satisfied with the value shown, correct the stadimeter, and press the button again.

[Rockin Robbins]

That last advice is right on. I manually correct ranges all the time. Just make sure the target is in the crosshairs when you press the button because range and bearing are updated together!

Rocks'n'Shoals, this thing goes in the [REL] Video Tutorals: TDC + PK advanced (http://www.subsim.com/radioroom/forumdisplay.php?f=202) thread, with your permission of course. Your instructions are very precise, you don't leave out any steps and you communicate very clearly. It deserves to be in a sticky thread, not buried for all time in the anonymous archives.:up:

[Rocks'n'Shoals]

Rocks'n'Shoals, this thing goes in the [REL] Video Tutorals: TDC + PK advanced (http://www.subsim.com/radioroom/forumdisplay.php?f=202) thread, with your permission of course. Your instructions are very precise, you don't leave out any steps and you communicate very clearly. It deserves to be in a sticky thread, not buried for all time in the anonymous archives.:up: Thanks RR, I am of course happy to give that permission.

[Fincuan]

Here's some food for thought: Provided your observations on the target's course and speed are correct and you're firing with a gyro angle of zero using the constant bearing method, range doesn't matter. That naturally means that it doesn't matter if your boat is stopped or moving either.

It doesn't matter how fast the target is going, what its course is or at what bearing it is, a zero gyro-angle constant bearing shot will always hit regardless of the range, provided that it is actually possible to hit the target at all. Here's short illustration:

Here we have a torpedo track angle of 45 degrees, just as in one of RR's tutorials. Our Mk18 torpedo has just exited the tube, going straight forwards at 29 knots as a good Mk18 with a gyro angle of zero should. The target we're aiming at is the middle one, and the two others are to show you the effect of miscalculating the range, badly. Distance to the "firing bearing"-node is written there, ~4400 meters. The red circle with "x" in the middle is the intercept point for a 29-knot torpedo for those targets.

http://staufa.sytes.net/files/sh4/pics/45degrees.jpg

Same situation, torpedo track angle is 90 degrees.
http://staufa.sytes.net/files/sh4/pics/90degrees.jpg

Yet again, with a torpedo track angle of 120 degrees.
http://staufa.sytes.net/files/sh4/pics/120degrees.jpg

As you can see all the targets sit on the same bearing line when the torpedo is fired, and regardless of the target they sit on the same bearing line when the torpedo hits. Naturally the firing bearing varies depending on the situation, but if you are able to calcuate it accurately for each target you can forget about range. :up:

[Rocks'n'Shoals]

With the constant bearing method, you don't have to use the 'scope to shoot. You can also shoot on the map only, using sound bearing lines and/or radar positions (if you are at radar depth). Just wait until the ship passes your constant bearing line on the nav map. Bear in mind that sound bearings originate from the screws, which are located at the stern of the ships...

A sea story to go with that: Recently I encountered a small task force consisting of three destroyers, running 12 knots. Heavy rain, visibility about 600 meters. I set up for constant bearing, for a range just over 1000 meters, and stayed at radar depth to detect them steaming to the firing spot - both with sound and radar. Got the first one amidships (I think, never actually saw him). It sank immediately, one torpedo is enough to crack up those small tin cans...

Too bad his colleagues were of the elite kind. Can't imagine what they had against me... :doh:

I fired at the second one when it crossed the constant bearing line, but it turned on me, so the torpedo couldn't hit. I immediately went deep, below a thermocline, and crept silently along at just over 1 knot to get away, changing course now and then to confuse them... No chance. They seemed to know exactly where I was, circling above me, and dropping DCs right on top of me. After hours, and after sustaining an increasing amount of damage, they backed off a little. I tried to go to periscope depth for a possible shot... BAD mistake, they where back right on top of me in no time, and bombarded me again, this time for critical damage. Good tactics on their part. :o

Getting desperate, I surfaced and tried to run for it, flank speed. But they are expert gunners, you know... I got one with the deck gun, but the other sank me. Ouch! :damn:

So, learn the lesson, and avoid task forces consisting of destroyers only... It might be their "task" to sink unsuspecting subs like you. They are just waiting for you to shoot at them - you will be lucky if you escape alive, certainly not undamaged. Great addition to the stock game, keeps the tension up...

[Rocks'n'Shoals]

Here's some food for thought: Provided your observations on the target's course and speed are correct and you're firing with a gyro angle of zero using the constant bearing method, range doesn't matter.
Well, that is a good approximation for far-away targets, but not exactly true, because there is a thing called "torpedo ballistics". Torpedoes do not instantly accelerate to full speed. Instead, they start with a slower ejection speed, and reach full speed only after a few seconds in their run. So you actually have to calculate with a corrected torpedo speed, which is dependent on distance: Lower for nearby target, higher for far-away targets. The TDC does that for you, if you enter the range correctly.

A zero-gyro shot aimed correctly for a far-away target will miss a bit astern, if the target is suddenly very close and moving fast.

[AVGWarhawk]

How are you changing that value on the PK for range?
It is updated by pressing the red triangle button on the stadimeter input of the TDC. If you are not satisfied with the value shown, correct the statimeter, and press the button again.

I figured that out after reading your instructions again. I have to say, it worked just great. However, and no fault of your own.....to friggin duds:down: Darn BuOrd...fix the torpedoes!!!! Anyway, RR is correct, the sub will either sink or submerge when propulsion is not present. I do not remember. GWX was able to implement that for SH3. Cool feature. Might be a good idea to drum up a mod to do this in SH4:hmm: This will then overcome the only critical point RR presented. So, at the very least, your sub would have to maintan 1 kt and that should not screw up your shot at that speed.

[Rocks'n'Shoals]

Anyway, RR is correct, the sub will either sink or submerge when propulsion is not present. I do not remember. GWX was able to implement that for SH3. Cool feature. Might be a good idea to drum up a mod to do this in SH4:hmm: This will then overcome the only critical point RR presented. So, at the very least, your sub would have to maintan 1 kt and that should not screw up your shot at that speed.
Another way around this problem, if you play that realistic: Set up your solution for the position where you plan to be at the time of firing. No matter where you currently are, no matter what you do in the meantime, just make sure to be there at the predetermined spot when the target crosses your constant bearing line. If you change your heading in the meantime, correct the periscope pointing to match your predetermined absolute constant bearing, and confirm the new relative bearing for the TDC. Again, it helps when you are moving exactly in the direction of your constant bearing line, small position errors in the direction of movement will be negligible that way.

Might require some calculation, or just steaming back and forth around the spot until the time arrives...

[tale]

Am I mistaken here or you just reinvented the Dick O'kane method as explained by Rocking Robins?

The only difference I see is that you don't ask for a 90º angle between the course of the target and your submarine, but that is not really necessary because the TDC will take care of the calculations.

[AVGWarhawk]

Anyway, RR is correct, the sub will either sink or submerge when propulsion is not present. I do not remember. GWX was able to implement that for SH3. Cool feature. Might be a good idea to drum up a mod to do this in SH4:hmm: This will then overcome the only critical point RR presented. So, at the very least, your sub would have to maintan 1 kt and that should not screw up your shot at that speed.
Another way around this problem, if you play that realistic: Set up your solution for the position where you will be at the time of firing. No matter where you currently are, no matter what you do in the meantime, just make sure to be there at the predetermined spot when the target crosses your constant bearing line. If you change your heading in the meantime, correct the periscope pointing to match your predetermined absolute constant bearing, and confirm the new relative bearing for the TDC. Again, it helps when you are moving exactly in the direction of your constant bearing line, small position errors in the direction of movement will be negligible that way.

Might require some calculation, or just steaming back and forth around the spot until the time arrives...

Yes, one could do that. I asked the RFB gents to look into creating a mod for the RFB mod that would simulate the subs reaction while submerged at a dead stop. :up:

[AVGWarhawk]

Am I mistaken here or you just reinvented the Dick O'kane method as explained by Rocking Robins?

The only difference I see is that you don't ask for a 90º angle between the course of the target and your submarine, but that is not really necessary because the TDC will take care of the calculations.

Similar, yes! Both good tutorials. What I see from this one and RR's O'Kane is a completely new TDC interface were locking is not necessary thus bringing the simulation closer to real in feel. Just need to find the guy who can come up with one:hmm:

[Rockin Robbins]

Same with John P Cromwell. The periscope is not locked for that one either.

[Rocks'n'Shoals]

Am I mistaken here or you just reinvented the Dick O'kane method as explained by Rocking Robins?

Actually it can be seen as a generalized version of the Dick O'Kane method as described by RR. Neither a 90º angle between the course of the target and your submarine heading nor a 0° gyro angle is required, and the TDC does all the calculations for you.

[Soundman]

Am I mistaken here or you just reinvented the Dick O'kane method as explained by Rocking Robins?

The only difference I see is that you don't ask for a 90º angle between the course of the target and your submarine, but that is not really necessary because the TDC will take care of the calculations.

Similar, yes! Both good tutorials. What I see from this one and RR's O'Kane is a completely new TDC interface were locking is not necessary thus bringing the simulation closer to real in feel. Just need to find the guy who can come up with one:hmm:

This has been one of my pet peaves since day one. There should be a manual way to enter range or at least the capabilty to use the stadmeter without locking onto a boat. I know this has been said, but,,,:damn:

[Soundman]

Am I mistaken here or you just reinvented the Dick O'kane method as explained by Rocking Robins?

The only difference I see is that you don't ask for a 90º angle between the course of the target and your submarine, but that is not really necessary because the TDC will take care of the calculations.

Similar, yes! Both good tutorials. What I see from this one and RR's O'Kane is a completely new TDC interface were locking is not necessary thus bringing the simulation closer to real in feel. Just need to find the guy who can come up with one:hmm:

This has been one of my pet peaves since day one. There should be a manual way to enter range or at least the capabilty to use the stadmeter without locking onto a boat. I know this has been said, but,,,:damn:


Well....after that last post and thinkning about it, I remembered a thread some time back that explained how to edit a file allowing manual input of range....It took some time, but I found it, tried it, and man, am I a happy dude :lol: ... It's very easy and quick. I would suggest a backup of the file first, because I screwed up the first time, but it wasn't hard to put back (luckily). Also, after getting the first one worked out, I wasn't really happy with the result and read some more of the thread. Bottom line, scroll down and read "Munchausens" post and follow his lead. It works absolutely fabulous. I can now input any range I desire. I highly recommend it. :rock: BTW, yes it works with 1.5. Here's the link to the thread http://www.subsim.com/radioroom/showthread.php?t=111371

[Munchausen]

Btw, the stadimeter does work without locking the target. I use it that way all the time (manually inputting range only when the target is too far away to get an accurate stadimeter reading).

The trick is that you still need to have some part of your target in the crosshairs. Normally, I'll take a final range and bearing, using the stadimeter, just as the target's bow is crossing the lubber line (PK off) then fire torps as the juicy parts sail across.

[Rockin Robbins]

A brilliant point, munchausen. Take a bow! If everyone did that just before they shot they'd be twice as accurate.

[Munchausen]

;) Thanks, RR.

:hmm: I suppose you could also input manual range for when you use the O'Kane method ... else your stopwatch won't give you an accurate torpedo travel time. Normally, though, I'm within 500 yards of the target and, consequently, seldom have time to even look at the stopwatch.

[Soundman]

Btw, the stadimeter does work without locking the target. I use it that way all the time (manually inputting range only when the target is too far away to get an accurate stadimeter reading).

The trick is that you still need to have some part of your target in the crosshairs. Normally, I'll take a final range and bearing, using the stadimeter, just as the target's bow is crossing the lubber line (PK off) then fire torps as the juicy parts sail across.

Yes, I was aware you did not have to actually lock, but it's still a bit of a gripe of mine that you even have to point the crosshairs anywhere to use the Stadmeter. In real life, the stadmeter had no way of knowing if there was a boat in the crosshairs or not. Here's what used to pee me off..As an example, the weather is so bad you can't even see the boat. You know it is there because of the radar, you know the range because the radar tells you, but you can't enter it!:damn:

Of course, I don't have that problem now, thanks to you Munchausen. Thanks again. AAHHRRR MATE!:arrgh!:

[Munchausen]

;) No problem. Now if only the mod in Nisgeis' following thread could be displayed in yards:

http://www.subsim.com/radioroom/showthread.php?t=142884

[Soundman]

;) No problem. Now if only the mod in Nisgeis' following thread could be displayed in yards:

http://www.subsim.com/radioroom/showthread.php?t=142884

Oh Yea, that would be sweet ! Until then we'll just have to measure the old fashioned way.

[I'm goin' down]

Please refer to the first post.

I have a conceptual problem. I usderstand entry of speed, AoB, and distance. I assume that the 293 degrees in the tutorial is the intended true course of the torpedoes. Is that courrect? Is that where you poitnt the periscope? I am not sure how that fits into the scheme of the constant bearing meithod. I need an explanation to help me figure this out.

[gutted]

When im doing constant bearing attacks with 0 gyro angles.. i never use the TDC dials.

I have a precomputed table i made with lead angles.

If it's a 90AOB shot, just look up the target speed and match it to the torpedo speed, move the scope from your nose towards the ship the number of specified degrees and shoot as he crosses.

If it's not 90AOB you need to get his relative speed across your nose as if it WERE a 90AOB shot. Easily done with a quick vector calculation with the drawing tools. I keep saying im going to precompute these for all AOB's as well, but haven't had the time lately. Too busy playing.

most of the time if your within +-30 degress and the range isn't that far, you can just assume a 90AOB shot.

i dunno, playing witht he dials if you dont intend to move just seems pointless to me. All you really need to know is how fast he's moving across your nose and lead it. Probably because im a duck hunter in real life :P

lately though, i've been using the PK alot for manuevering in and keeping tabs on where he is without needing to actually put the scope up and look at him, and then just turning it off just prior to shooting and using a constant bearing attack. Basically i track him with the PK to a good firing point, and when im about ready to fire i take that last range reading, shut of the PK, move the scope to the ships nose, and put in the new bearing with the same range (shouldn't change much to matter), and fire as the ship crosses the line.

i do this because i hate having to manually adjust the spread angle wheel for each torpedo.

[Rockin Robbins]

lately though, i've been using the PK alot for manuevering in and keeping tabs on where he is without needing to actually put the scope up and look at him, and then just turning it off just prior to shooting and using a constant bearing attack. Basically i track him with the PK to a good firing point, and when im about ready to fire i take that last range reading, shut of the PK, move the scope to the ships nose, and put in the new bearing with the same range (shouldn't change much to matter), and fire as the ship crosses the line.

Arrrrr!:arrgh!: Exactly the same technique the real Dick O'Kane used to refine his target parameters before unleashing HIS constant bearing attacks.

[I'm goin' down]

See post #30 please. I need some help. Where do you input 293 degrees or how do you use it?

[gutted]

i dont really subscribe to any pre-difned methods. Just like aerial combat.. if you go in with your mind made up, your SOL when the situation changes.

every situation has its own solution.

i dont always do it with a constant bearing either. for a really long target or very slower mover i wont sit there and wait for him to travel all the way through. in that case when i shut it off the PK, i'll aim at the rear.. mark it fire.. aim at the center.. mark.. fire.. aim at the front.. mark.. fire.\

i go back to front in this case, becaue when i unlock the target and shut off the Pk, the sight is usually already at the rear.

i only use my lookup table for when i dont have the time for a more accurate shot. just put yourself on a rough 90 degree course and fire at the specified lead angle. though if you take the time to setup for a perfect 90AOB shot, its impossible to miss. lately though, i've grown tired of doing that much plotting and figuring, and instead plot just enough to get me in visual range, and just work it with the PK till the fire point. i rarely look at the map anymore after i get visual.

i also dont play with map contacts enabled.. because it makes the perfect 90AOB zero gryo shot just way too easy.

[gutted]

...,

[I'm goin' down]

Captain, I assume you were addressing my post in this thread. I respond. Your disertation may be welcome and appreciated by others, as you are obviously an enlightened captain. My question was specific. You did not address it.

Maybe you assumed that I did not know how to use manual targeting (per Hitman's tutorial), the Dick O'Kane or Cromwell methods, Tale's techniques on attacking mutiple ships in convoys on the same or parallel courses, using sonar only, or was unaware of how to apply the Easy AoB mod (which I was instrumental in having promoted to a sticky thread)?

Mine was a simple straightforward post. I did not understand one aspect of the tutorial on the point and shoot method. Period.:salute:

[gutted]

i was going to reply to you, but having not read through the entire first post in detail (i skimmed over it, saw someone moving dials for a constant bearing attack and decided to post), and just assumed that 293 was for one thing, but after a closer look i decided to delete my post because i could have been wrong and didn't want to give you any wrong info.

[gutted]

ok i read the intial post alittle more carefully this time.

293 is the "TRUE BEARING" equivalent of the relative bearing he needs to be looking at when he fires.

since he's using the stock bearing lines (top of his scope) that don't have any intermidiate marks.. he has a really hard time telling exactly where 293 is.

so he keeps issusing the "set course to where im looking" command until the crew says "set course bearing 293". since he's not moving he wont actually turn the ship.

atleast thats the gist of what i got from it. his explination is alittle convoluted.

[I'm goin' down]

I finally hit the target in a practice mission. My problems are these. Once I get the true bearing of my boat, how to I get the radar man to announce its true course. I play TMO and there is no button to match heading to view. Since I am not moving, nothing happens when I hit the only button that appears relevant, which is the command to return to course. It is not operating because my ship is not moving, as I am in position to fire. Without a command to match heading to view, I have know way of knowing if my boat's heading matches the course (in the tutorial, it is the 293 degree angle). I think I have the rest pretty well in hand, but I have spent a lot of time to narrow it down to this question.

Also, I click the TDC button to send speed, range, and distance. Do I click that button when I set the periscope at the firing angle?

Once I have this thing down, it will be easier for me to conceptualize it.

I agree, the tutorial is not a model of clarity on a few points, but the concept is very interesting. Thanks for weighing in on this. It took me a while to be able to articulate these issues, as I haven't hit the target in multiple attempts until a few minutes ago. It appears you can either hit is with fast or slow torpedoes but not both fired in a single salvo. Whew, I am exhausted.

[I'm goin' down]

the key command for heading to view is the "=" sign.

[Rockin Robbins]

Please refer to the first post.

I have a conceptual problem. I usderstand entry of speed, AoB, and distance. I assume that the 293 degrees in the tutorial is the intended true course of the torpedoes. Is that courrect? Is that where you poitnt the periscope? I am not sure how that fits into the scheme of the constant bearing meithod. I need an explanation to help me figure this out.

OK let me try this one. In the first post, Rocks'n'Shoals is kinda doing an inside out vector analysis without the analysis. He's using the TDC to calculate where the torpedoes go. The true course of 293 is the direction his periscope is aiming, not the direction the torpedoes go.

Using the lead angle line allows him to use the protractor to figure out exactly what the AoB at time of firing will be. The range along the sighting line is also the correct range for the TDC.

Rocks'n'Shoals has no idea, and doesn't really need to care what his gyro angle is. He really doesn't know the course the torpedoes will take toward the target because he's letting the TDC figure that out for him. He knows by inspection that the gyro angle is under 30º, and all shots under a 30º gyro angle are considered straight fire according to the Submarine Torpedo Fire Control Manual.

One thing he could do to simplify his method of setting the periscope bearing is to order the boat's course with the course setting tool instead of the compass. This would leave a line on the nav map showing the boat's heading. He could then use the protractor, clicking on the own heading line, clicking on the middle of the sub and then again somewhere up the sight bearing.

Let's suppose that angle is 22º. In this case you would take 360º (same as a zero bearing) and subtract the 22º measured angle to set the periscope at 338º for your shoot bearing. That way you don't have to use the set heading to view key to trick the computer into telling you the true bearing of the periscope sight line. It's quite a bit quicker than Rocks'n'Shoal's trial and terror method too!:D

Of course the absolute best solution would be to load up the 3000 yard/meter bearing tool (http://www.subsim.com/radioroom/downloads.php?do=file&id=174) and just read the relative bearing off the tool!

[I'm goin' down]

OK let me try this one. In the first post, Rocks'n'Shoals is kinda doing an inside out vector analysis without the analysis. He's using the TDC to calculate where the torpedoes go. The true course of 293 is the direction his periscope is aiming, not the direction the torpedoes go.

Using the lead angle line allows him to use the protractor to figure out exactly what the AoB at time of firing will be. The range along the sighting line is also the correct range for the TDC.

Rocks'n'Shoals has no idea, and doesn't really need to care what his gyro angle is. He really doesn't know the course the torpedoes will take toward the target because he's letting the TDC figure that out for him. He knows by inspection that the gyro angle is under 30º, and all shots under a 30º gyro angle are considered straight fire according to the Submarine Torpedo Fire Control Manual.

One thing he could do to simplify his method of setting the periscope bearing is to order the boat's course with the course setting tool instead of the compass. This would leave a line on the nav map showing the boat's heading. He could then use the protractor, clicking on the own heading line, clicking on the middle of the sub and then again somewhere up the sight bearing.

Let's suppose that angle is 22º. In this case you would take 360º (same as a zero bearing) and subtract the 22º measured angle to set the periscope at 338º for your shoot bearing. That way you don't have to use the set heading to view key to trick the computer into telling you the true bearing of the periscope sight line. It's quite a bit quicker than Rocks'n'Shoal's trial and terror method too!:D

Of course the absolute best solution would be to load up the 3000 yard/meter bearing tool (http://www.subsim.com/radioroom/downloads.php?do=file&id=174) and just read the relative bearing off the tool!

Well, that certainly fixed the problem. I followed your suggestion. I eliminated heading to view and used my boat's heading to set up the shot. The AoB was 102 degrees. I set the periscope at 338 degrees and fired as the target crossed the wire. 4 fast and 2 slow topredos at 2100 yds. I used the Dick O'Kane practice mission, where the target is doing 12 kts. I followed the torpedoes' progress with the free camera. And, viola,
torpedo 1 = impact;
torpedo 2 = impact;
torpedo 3 = impact;
torpedo 4 = "it's a dud, Sir" (it hit the target, as I witnessed the impact)
impact.);
torpedo 5 = impact; and, finally
torpedo 6 = impact!

I think I got it now. Rockn' shoals tutorial still confuses me, but your solution eliminates a step and seems (:haha:) to work. Thanks.

[Rockin Robbins]

The crew of that tanker you mercilessly incinerated do NOT thank you.:nope:

[gutted]

You could also just set yourself up at any abritrary angle to the target and not even use the TDC dials.

What you do is draw a straght line from your nose to where it crosses the targets path (you're trrue bearing). this is the impact point. then draw a line from the impact point down the targets course towards the target equal to his speed (5kts, draw a 500m.) note: could be yards doesn't matter.

adjust your "course" line (the first one you drews) so that it's length is equal to your torpedo speed (46kts fast fish, 4600m). then measure the angle between those two end points. .ie click at the impact point, then click at the end of your torpedo line, then the end of the ships speed line. note the angle, then turn your periscope that many degrees from 0 towards the target and wait for him to cross it.

doing this is quicker, and uses a zero gyro angle. which means you can hit any ship that crosses that line extremely accurately regardless of it's range.

i hosed a target like this from over 7000m the other day. so there you go.

you as captain should have a large bag of tricks. just try not to hemm yourself into 1 way of doing things. Using the PK to track a taret is still important IMO.. because if the target changes course at the last minute, you can fall back on it. Happened to me last night. Was approaching from the front parallel to his course... and had him squarely tracked with the PK. after i turned in for the shot when the range was short, the target made a course change.. turning towards my inside. crap! so i kept my turn going and selected the stern tubes. readjusted his AOB to what it looked like and grabbed a quick stadimter and fired. BOOM!

[DigitalAura]

In the tutorial pics, the sub seems to be actually pointing a few degrees to the port side of the 'lead angle' line.
Won't this throw off the TDC calculations and won't his AoB be incorrect?

here's the pic for reference...
http://astro.nightsky.at/Download/ConstantBearing_3.jpg

EDIT: Oh, nevermind...that black line is the sonar reading, I was thinking that was his line to shoot...obviously his line to shoot is the red one, in which case the zero degree line is not drawn in (the path the torpedos will travel).

[I'm goin' down]

that explanation was too confusing for me to follow. Rockin Robbins provided a simple explanation. see posts 41 & 42.


I reread your post. I am guessing that what you attempted to descrbe is exactly what Rockin Robbins stated. If it isn't, I have no clue. By way of example, which direction is the nose facing. I think you are saying that the "nose" is facing the direction of the boat's true course? This is technical stuff, so please try to be precise.

[Rockin Robbins]

you as captain should have a large bag of tricks. just try not to hemm yourself into 1 way of doing things.

A man after my own heart!!!! Gutted started my quest for collecting my "bag of tricks." His encouragement when I was a rather confused fleet boat skipper wondering if there were any tricks I could learn from the U-Boat people started the whole Bag of Tricks thread (http://www.subsim.com/radioroom/showthread.php?t=146795) and is directly responsible for the Dick O'Kane technique and indirectly responsible for all the other constant bearing techniques and wrinkles I have developed.

Gutted sent me a very simple animated gif that began all the madness, along with his lead angle chart he's talked about.
http://i196.photobucket.com/albums/aa293/RockinRobbins13/Silent%20Hunter%204/Manual%20TDC%20Range/OKanemethodanimation.gif

http://i196.photobucket.com/albums/aa293/RockinRobbins13/Silent%20Hunter%204/OKane90_FiringAngles.png

And there you see the genesis of the Dick O'Kane technique, posted (http://www.subsim.com/radioroom/showpost.php?p=625379&postcount=66) and sent to me 8/19/2007 by gutted. At the time he was strictly a U-Boat jockey who had spent limited time in a fleet boat. He jumped into a thread where an upstart called Cali03boss was stinkin' it up and with one post started a revolution in Silent Hunter 4. (In the formula above, it should say arctangent instead of inverse_tangent, but there's the key to the universe, right there!:up:)

[Rip]

A man after my own heart!!!! Gutted started my quest for collecting my "bag of tricks." His encouragement when I was a rather confused fleet boat skipper wondering if there were any tricks I could learn from the U-Boat people started the whole Bag of Tricks thread (http://www.subsim.com/radioroom/showthread.php?t=146795) and is directly responsible for the Dick O'Kane technique and indirectly responsible for all the other constant bearing techniques and wrinkles I have developed.

Gutted sent me a very simple animated gif that began all the madness, along with his lead angle chart he's talked about.


http://i196.photobucket.com/albums/aa293/RockinRobbins13/Silent%20Hunter%204/OKane90_FiringAngles.png

And there you see the genesis of the Dick O'Kane technique, posted (http://www.subsim.com/radioroom/showpost.php?p=625379&postcount=66) and sent to me 8/19/2007 by gutted. At the time he was strictly a U-Boat jockey who had spent limited time in a fleet boat. He jumped into a thread where an upstart called Cali03boss was stinkin' it up and with one post started a revolution in Silent Hunter 4. (In the formula above, it should say arctangent instead of inverse_tangent, but there's the key to the universe, right there!:up:)

This discussion and the fact I am currently reading Wahoo written by the Rear Admiral has me pondering this. At least when O'kane is XO he and Mush normally were shooting 120 AOB shots. Should I be? You would need a different chart for that I would expect? IIRC he wrote that made it harder to maneuver away from the shot.

Now I also wonder if he kept doing that after getting his own command or did he start going for 90 shots?

[Rockin Robbins]

I dunno. I think he took the shots as the situation dictated and wrested the odds as best he could. It's not like you look at an unfavorable position and say, "Nope. I don't like that angle."

Statistical analysis shows that a torpedo track angle of roughly 110º (varies with speed) is the most tolerant with regard to errors in calculating target speed. Reverse analysis of their mumbo-jumbo showed that firing at AoB 90 or slightly afterward was best for that.

As far as maneuvering out of the way of the torpedo, a torpedo track angle of 90º would be the best because the target has to turn just as far in both directions to avoid.

Let's reason this out. You're firing a John P Cromwell attack from 45º ahead. That ends up giving you an AoB of about 35º starboard or port depending on which direction he's coming from. The sharpest he has to turn to get his bow toward the torpedo and then be able to turn left or right to avoid is.....45º, right?

OK, let's take the O'Kane situation. The torpedo approaches from 30º or more aft of the target beam (torpedo track angle of 120º or slightly more). We'll assume the target is moving left to right. Since the torpedo is approaching from aft, the speed of the target makes the approach speed of the torpedo slower, giving the target more time to react. Then the target needs only to turn 60º to port, hit the throttle and maneuver left or right to let the torpedo, now on a parallel course, pass starboard or port.

I don't understand O'Kane's reasoning there. I'd rather be firing from ahead of the target if I can't pick the 90º attack, so that I have lots of wiggle room in my calculations and can absorb maximum error. Failing that I want the target to have minimum time to react if he sees the torpedo.

[Frederf]

I wonder if there's some factors that we're leaving out. There are a lot of assumptions about a target maneuvering to get out of the way of a torpedo.

1. Target spots the torpedo equally well in all directions.
2. Target is able to ascertain torpedo motion well enough to make a fully reasoned maneuver.
3. Target decides what maneuver to make on a case-by-case basis instead of some rapid and wrote drills.
4. Likelihood of torpedo hit overrides all other tactical considerations like defensive posture.

If all Japanese merchants were known to be trained to turn left when under a torpedo attack then that certainly changes your tactics. One might also regard that a target passing through AOB 90 gives the best chance to take good speed, course, etc data for an accurate shot which leaves the submarine aft of beam since the torpedo launch comes after the data taking.

@RR: I'd like to see the same animated .gif with 1 torpedo passing through all 4 targets as if they had a hole in the middle of the ship. That picture is one way I like to attack convoys as several targets' solutions converge.

I have found the AOB150 shots to be more error prone but then again I'm behind a desk and not in a leaky iron warboat 2000mi from home.

As for Cromwell v OKane... they both give about the same leniency to the target to turn a short angle to negate the solution, apart from the time-to-impact difference. I think TTa 90 gives the most difficult evasion scenario for the target but I'm not 100% sure.

Also ArcTan, Inverse Tangent, or Tan^-1 are all perfectly acceptable synonyms. I prefer the Tan^-1 notation when I can actually write the superscript proper unlike in forum posts. I kinda consider the "arc" prefix to be rather anachronistic and to be dropped from high school textbooks steadily.

That chart has an error of either language or trig function. If you want to fire such that the torpedo tracks squarely into the target's side then that isn't a 90 AoB shot but a 90 TTa shot in which case ArcTan is correct. If you want to fire when the target is at 90 AoB (TTa > 90) then ArcSin is correct.

[gutted]

I called it 90AOB on my table due to the fact that in the U-baot (re: SH3) the periscope and aob dials were linked. so to take this kind of shot all one had to do was put the scope at 0 degrees.. set 90AOB (or any AOB for that matter), then train the scope left or right until the gyro read 0. thus taking a 90AOB shot. though techincally, it was less than 90AOB at the aim point becaues the AOB would change autommically with the scope in SH3.

this table was my attempt to simplify this for SHIV, since the two dials were not linked as in SH3.

As for arctan, invtan.. im no mathemetician, but aren't they are the same thing. i put inverse tangent because the windows calulator doesn't have an arc tangent function. to get the same effect you do inverse tangent. .ie 1 / tan(x). to be honest, i dont remember why i have the "90 -" part of the formula there. This was done some years ago. Basically what i did was worked it out using the windows calculator.. then whipped up a quick C++ program to spit out the numbers, then dropped it into an XML file to print it.

in windows calculator you'd do this for fast mk.14 vs 9 kt ship:
46 / 9
hit the = button
hit the Tan button
hit the 1/X

again i cant remember what the "90 - " was for.

anyway, i need to update that table one of these days. First off the table assumes Mk.14 torpedos (31kt slow, 46kt fast). and secondly i need to extend it off to the right for Impact AOB's other than 90, as i dont really try to set up for perfect 90AOB shots anymore now that i've grown found of the american TDC and find myself actually using it. .ie i dont line up perfectly at 90AOB and wait like a duck.. i'm always on the move manuevering now. though every now and then i find myself in a situation where i fall back on the table for hip shots. gives me a rough idea of how much i need to lead for a given target speed.

[gutted]

... is directly responsible for the Dick O'Kane technique and indirectly responsible for all the other constant bearing techniques and wrinkles I have developed.



you can call it whatever you want.. but im still calling it fast 90. :DL

*runs away screaming*

[gutted]

that explanation was too confusing for me to follow. Rockin Robbins provided a simple explanation. see posts 41 & 42..

maybe a picture will tell it better.
http://i857.photobucket.com/albums/ab138/gorey666/geometry.png

my way:
draw two lines, and measure one angle. set your scope that many degrees from 0.

robbin's way:
Draw a line, measure the AOB & Range for that line.. and play with the Dials to match it.

either way works. i just dont like playing with the dials for this type of shot. :P

edit:
now that i think about it.. i guess i should have put arrows on the lines. the target in these examples are move left to right.. and ownship is moving bottom to top.

[Rip]

I dunno. I think he took the shots as the situation dictated and wrested the odds as best he could. It's not like you look at an unfavorable position and say, "Nope. I don't like that angle."

Statistical analysis shows that a torpedo track angle of roughly 110º (varies with speed) is the most tolerant with regard to errors in calculating target speed. Reverse analysis of their mumbo-jumbo showed that firing at AoB 90 or slightly afterward was best for that.

As far as maneuvering out of the way of the torpedo, a torpedo track angle of 90º would be the best because the target has to turn just as far in both directions to avoid.

Let's reason this out. You're firing a John P Cromwell attack from 45º ahead. That ends up giving you an AoB of about 35º starboard or port depending on which direction he's coming from. The sharpest he has to turn to get his bow toward the torpedo and then be able to turn left or right to avoid is.....45º, right?

OK, let's take the O'Kane situation. The torpedo approaches from 30º or more aft of the target beam (torpedo track angle of 120º or slightly more). We'll assume the target is moving left to right. Since the torpedo is approaching from aft, the speed of the target makes the approach speed of the torpedo slower, giving the target more time to react. Then the target needs only to turn 60º to port, hit the throttle and maneuver left or right to let the torpedo, now on a parallel course, pass starboard or port.

I don't understand O'Kane's reasoning there. I'd rather be firing from ahead of the target if I can't pick the 90º attack, so that I have lots of wiggle room in my calculations and can absorb maximum error. Failing that I want the target to have minimum time to react if he sees the torpedo.

Well I went back and found the spot. Page 202 reads:

At 0455 it was light enough to see through the scope, and finally two blasts took us down, pausing while a final radar range and periscope bearing fixed her position. Both Chan and Richie agreed on an enemy speed of 9 knots instead of ten. Captain Morton had readied two tubes forward and aft, and now ordered the forward doors opened; it would be a bow shot. Her port angle was opening as it should. I heard Richie advise, "750 yards from the track, as I called 90 port.

The captain waited for an approximate 120track, the aspect that would allow maximum enemy maneuvers and still insure that our torpedoes would hit, and then said, "Any time, Dick. Fire just one torpedo."

I remembered it because it was opposite of what I would have thought as well. I am a submariner but we would just steer them with the wire or chnge acoustic modes. :D

[Frederf]

though techincally, it was less than 90AOB

I figured that's what it was, a 90° torpedo track angle shot which means 10-20° visual lead.

As for arctan, invtan.. im no mathemetician, but aren't they are the same thing.

Yeah, same thing.

[I'm goin' down]

If you are firing at zero bearing, all you have to do is make sure that your lead angle is at least large enough that is equals or exceed the distance (i.e. yards/meters) the target can travel over a 3 minute interval? For example, if the target is travel 10 kts, covering 1,000 yds. over 3 minutes, and you want to have impact at a zero degree bearing, the firing point is as follows:

For a target approaching from your port side, the firing point is that point

1. on the target's course where the angle, created by running down the course line 1,000 yds. from the point where the imaginary line extending from the zero bearing crosses the target courses,
2. intersects with the firing point?

[gutted]

If you are firing at zero bearing, all you have to do is make sure that your lead angle is at least large enough that is equals or exceed the distance (i.e. yards/meters) the target can travel over a 3 minute interval? For example, if the target is travel 10 kts, covering 1,000 yds. over 3 minutes, and you want to have impact at a zero degree bearing, the firing point is as follows:

For a target approaching from your port side, the firing point is that point

1. on the target's course where the angle, created by running down the course line 1,000 yds. from the point where the imaginary line extending from the zero bearing crosses the target courses,
2. intersects with the firing point?

im not following you.

it's the angle created by the ratio of your torpedo's speed to the ships speed as in the picture i posted earlier. note: the start of the 46 line does not originate from the center of your ship... your ship could be anywhere on the line. you will most likely be closer than 4600m (If using 100m scale)


another way would be be to measure the distance to the impact point from your nose. figuring out how long it would take your torpedo to reach it. Then figuring out how far the enemy will travel in that time period And measure the angle from impact point, your ship, and imginary target ship.

that way takes too much effort.

[Rockin Robbins]

Frederf: you're really onto something there with your assumptions, and there is something that the game would differ markedly from real life. An example I am familiar with is that Japanese destroyer captains were trained that Americans were right handed and that underwater evasion maneuvers were always to the right. (source: Japanese Destroyer Captain, Capt Tameichi Hara). Eugene Fluckey knew this and routinely turned left.

Concentrating on maneuvering conventions alone (for no particular reason, just picking one of the four), suppose the merchants were trained to turn to port to avoid. We'll talk about targets traveling from left to right here.

That being the case, if you shot before AoB 90, from ahead of the target, the target would see the approaching torpedo, turn left and diminish his cross-sectional area from the torpedo's point of view. This would greatly diminish the chance of a hit, and my experience with John P Cromwell shows that if they turn into the path you get almost no hits.

Gutted has talked about what us astronomers call "proper motion," that is the component of apparent motion from left to right (or right to left) from the point of view of the observer, who has no idea of the angle between the target's path and your path. Well, if you do the math on a 45º shot, our proper motion is 70% of the actual speed of the target. However if he succeeds into turning into the direction of the torpedo (straight at us!) his proper motion is exactly zero! He's stopped. The torpedo passes harmlessly to his right because it is programmed for the apparent speed, the proper motion, of his original course.

Now lets take the situation where you shoot after AoB 90 and the torpedo is approaching from astern of the beam. Here, if the target turns left, he turns broadside to the torpedo, presenting a much larger target to hit, thank you very much, he has suddenly made his situation much worse and BOOM!

If such an assumption were built into the game, and I haven't seen any evidence that it is, it would also be very important to set up assymetrical spreads to compensate for expected reactions. For instance, if firing from ahead and expecting him to turn into the direction from which the torpedoes are being fired, it would be important to fire a trailing shot that would miss a target which stays on course but would tag the target which turns in the anticipated direction.

Real skippers did that a lot, which explains a lot of their misses. Those weren't misses due to poor shooting, those were cover shots, ensuring a hit in those "what if" situations. Wasting topedoes to save your life ain't a bad proposition!

I could cover the other possible assumptions, but I think the general idea is here. Too bad I don't see any evidence of that behavior in the game. It was vital information in real life.

[Pacific_Ace]

RR sez:
"Now lets take the situation where you shoot after AoB 90 and the torpedo is approaching from astern of the beam. Here, if the target turns left, he turns broadside to the torpedo, presenting a much larger target to hit, thank you very much, he has suddenly made his situation much worse and BOOM!"

I sez: I'm thinking this through in my head and coming up with 'thats only valid if he's turning into the direction the shot came from'. If he turns away, he is showing you his stern and reducing cross-section.

[Rockin Robbins]

RR sez:
"Now lets take the situation where you shoot after AoB 90 and the torpedo is approaching from astern of the beam. Here, if the target turns left, he turns broadside to the torpedo, presenting a much larger target to hit, thank you very much, he has suddenly made his situation much worse and BOOM!"

I sez: I'm thinking this through in my head and coming up with 'thats only valid if he's turning into the direction the shot came from'. If he turns away, he is showing you his stern and reducing cross-section.
That's true, but in this situation he would have to turn right to do that. I've already positied a rule that Japanese merchie captains turn left when they see a torpedo.

It seems to me that if there were a merchie rule, I'd make it that if the torpdeo approaches from aft of the beam you turn away, if from forward of the beam, you turn toward. However, I was working from the theoretical rule that frederf put into his post, just to illustrate that just like in real life we could anticpate habits of the enemy and turn them into sinkings.

Unfortunately, I have seen very few habits other than the dragster behavior when torpedoes are sighted.

[Frederf]

I'm pretty sure Japanese merchants of the time were taught "turn into a bow torpedo, turn away from a real torpedo" just like US sub captains were. There are examples of "turn this way training" like the ASW thing you mentioned and I believe some fighter pilots. I guess it would come down to a deck hand maybe having the presence of mind to scream "Torpedo attack, aft!" instead of "Torpedo attack!" in Japanese or just freezing up in disbelief.

Also I think the game makes the lookouts a little too vigilant with regards to spotting torpedo tracks and too quick to react both the crew and the ship itself physically. I was just simply trying to list plenty of "what-ifs" of factors that were present in real life that may not be modeled factors in the game or our gamer behavior.

Now for a 135 TTa shot yes turning one way or the other improves or worsens the target angular size but honestly both spoil the actual solution. If the target turns parallel to the torpedo track his angular motion goes from 0.707 to 0 or if he turns broadside his angular motion goes from 0.707 to 1. Either way he's not going to be where the torpedo expects him to be, the only difference is if it misses astern or passes alongside. Simply turning broadside is hardly the kiss of death.

I suppose that 0.707 and 0 are farther apart than 0.707 and 1 so turning broadside doesn't change the angular motion by as much as turning parallel. Also you figure that a spread of torpedoes are gunna cover a wide range so getting out of the way is not practical, you have to "turn slim." For a 150 degree shot the difference between turning 180 or 90 does the same thing.

I don't know of any real life torpedo shots that were purposefully aimed with the idea that "if the target turns left this'll get him." They simply fired spreads. Stuff like "angular target width 3 degrees, coverage 150%, maximum gap 67% = 3 torpedo spread 0,+2.25,-2.25."

[I'm goin' down]

If the 4600 yd line, the one that intersects the course line, does not start at my boat, where does it start? Where does it end? At the course line? And I assume my boat is on the 4600 yd. line. Do we need a different line if we use a different torpedoe speed?

Depending on where the course line interesects the 4600 yd. line, it will affect the distance. I understand using the target's speed to run up/down the target line to the firing point. I understand setting up the angle.

I assume we are not entering AoB in the TDC? Are we entering target speed into the TDC? Are we entering distance in the TDC?

I need this information so I can start at step 1 in this exercise. the math is beyond me.

[I'm goin' down]

maybe a picture will tell it better.
http://i857.photobucket.com/albums/ab138/gorey666/geometry.png

my way:
draw two lines, and measure one angle. set your scope that many degrees from 0.

robbin's way:
Draw a line, measure the AOB & Range for that line.. and play with the Dials to match it.

either way works. i just dont like playing with the dials for this type of shot. :P

edit:
now that i think about it.. i guess i should have put arrows on the lines. the target in these examples are move left to right.. and ownship is moving bottom to top.

I am still confused. Here are some simple questions. Some are difinition oriented. I consider other basic, so I can be sure we are not miscommunicating. I have situated the questions in the pararaphs relevant to the questions posed. I will not add my assumptions for what I think I should do, as they are likely erroneous. I do not want to make this more confusing to either you or me, or anyone else who might be unlucky enough to read this. I refer you to the examples in the post copied above. Assume I am using the Nav Map to draw my lines, courses and angles for purposes of these questions.

1. Assuming a 46 kt. speed for torpedoes, I draw a 4600 yd. bearing line that intersects the target's course line? If so, where does the bearing line begin and where does it end? Is my boat's location on that bearing line? If not, then where is it? Is my boats heading (true course) on that bearing line? If not, where is it heading? (Back to port? Just kidding.)

2. After figuring out the answers to questions posed in #1, I measure 500 yds. (i.e., the target's speed), and draw a line down the target's course line because the target is moving left to right?

3. I make an angle. An angle has two sides.

(a) The first side of the angle runs from the 4600 yd. bearing line? Must it run from my boat? Or from any point on the 4600 yd. bearing line? This side of the angle runs to its intersection of the target's course line. Can it run beyond the point of intersection?

(b) The second side of the angle runs from the same place as the first side of the angle. (Is that my boat? or any anywhere on the 4600 yds bearing line? or somewhere else?) and intersects the 500 yd. mark on the target's course line (described in #2 above). This intersection completes the angle and identifies the firing point of the torpodoes? The angle created is called the lead angle?

3. Assuming this angle is set up before the target crosses the intesection of the second side of the angle and the target's course line, I am now in position to adjust my periscope (assuming it is set to zero degrees) the number of degrees that corresponds (i.e. matches) to the number of degrees of the angle drawn on the Nav. Map. That is my firing point?

4. Do I need to measure measure distance? If so, is it distance to the point of impact or distance to the firing point?

5. Do I need to input AoB?

6. Do I need to input Speed?

7. I do not turn on the TDC by pushing the button to activate it?

Whew. If a response does not set me straight, I request reassignment for the good of the Silent Service.

[magic452]

I'm goin down.

The 4600 yard line(your course line) will start at the intersection of it and the target course line. EX. the intersection of the two red lines in the illustration.
It will extend 4600 yards from that point, passing through you boat at 0° and 180° if you are say 2000 yards from the target course line.

From the intersection of the two red lines go 500 yards (5kn.) towards the target Ex. the second red line where it meets the green line.

The green line (your lead angle line) is from the 4600 yard mark on your course line to the end of the second red line.

Measure the angle of the intersection of the red line and the green line at the 4600 yard mark. This angle will be your lead angle.

As the target approaches turn the periscope to that lead angle and shoot as the target crosses the wire.

Your boat can be any were on it's course line that is more than 500 yards(arming distance) and 4500 yard ( the range of the torpedo)

Target speed must = 0
AoB = 0
bearing = 0 and range does not matter. (For stern shots set the periscope to 180° and send bearing. Select a stern tube first.)
If they are not, set each to 0 and click send. You must have these at 0 no matter which method you use.

Do Not turn on the PK.

What you have pictured is O'Kane 90° and Cromwell 45° What I and Gutted are describing is actually vector analysis. You can be at any angle with V. A.

If you are at 2000 yards or less and have a big target you can approach at 65° +/- 1 or 2° AoB and your lead angle will equal the target speed, no need to draw any lines other than the target course line. Get a good speed reading and that speed = shooting bearing (lead angle).

This is very good for sonar only attacks, only be sure not to sink an Essex carrier. You may join another subsimmer on the rock pile. :rotfl2:
I won't mention any names but he has posted in this thread.

Magic

[I'm goin' down]

What a coincidence. Rockin Robbins just asked me if I know the name of the Captain whose boat sunk the Essex.:har:

[Pacific_Ace]

If you want to use something like this for a sonar shot, when its dark and stormy and you cant even see your own bow (and you KNOW theres not an Essex out there :har: ) at what part of the bearing spread do you shoot at?

[I'm goin' down]

Thanks Majic and gutted. That explanation, along with gutted pic, helps. I have been overthinking the method. I am off to try it out.

[magic452]

If you want to use something like this for a sonar shot, when its dark and stormy and you cant even see your own bow (and you KNOW there's not an Essex out there :har: ) at what part of the bearing spread do you shoot at?


It's really a timing thing and takes some practice. For single ships you can have the sonar lock on the target and fallow it to the lead angle shooting point. Try it a few times and you will get a feel for what spread and timing you need. Slow moving ships you can wait longer between shots.
Fast moving targets, such as an Essex, require faster shooting.

For convoys and task forces you can't lock on a single target so you must fallow the particular ship you want to hit and plot it's course to the firing point. It's a skill that requires practice but is a doable thing. Sonar sweeps take about 20 seconds for each update, so you must estimate the movement of the target for each sweep, again it's a timing skill you need to practice. Not as accurate as sight shot but still pretty good.

It's a handy tool if you have an escort that may detect you in good weather, I was at PD and id'ed a kongo BB but a DD was close so I went to 90 feet and shot from there. About 2800 yards in good weather and I hit 3 out of 4, and she went down. I shot right under the DD. THAT was fun. :yeah:

Magic

[I'm goin' down]

Let's say the target is moving left to right at 5 kts. You draw a 500 yd. line on the target course to calculate the lead angle using the constant bearing method. Let's say the lead angle is 5 degrees.

If the target is not on that course, but closer of further away, running parallel, won't that change the lead angle?

[Frederf]

@I'm goin' down: I've read post number 1 about a dozen times and can tell you there's absolutely nothing magical going on in this method. He's just setting up a "future" solution in the TDC and firing when the ships cross the wire. The heading to target (at moment of firing), heading of the boat, and course of the torpedo are 3 different directions which is why setting range is important.

293° bearing is just his "shoot course" or the absolute bearing to target when he launches torpedoes. This is why he has us keep pressing the "heading to view key" so we can place our periscope in the 293° true direction when our periscope has a 000-is-where-the-sub-is-pointing scale instead of the needed 000-is-where-the-north-pole-is scale. What's silly is that once you get a TDC solution you can simply mouseover the TDC window and read off the relative bearing to target for you solution eliminating the whole need to use that silly trick.

Honestly I find the concept of picking your shoot bearing out of a hat and then determining the gyro angle from that to be a bit backward. However if you must draw an arbitrary line from self to target track and then figure out gyro angle from that I could think of a slightly easier procedure.

1. Draw target track.
2. Draw shoot line from ownship to track. Length = range.
3. Measure angle from track to shoot line. Angle = AoB.
4. Measure angle clockwise from ownship heading to shoot line. Angle = shoot bearing.
5. Turn periscope to shoot bearing, drag range, drag AoB, drag speed.
6. Press Send Data to TDC.
7. Check result gyro angle is reasonable (000 +/- 30°).

It's pretty easy to see that this is just "What are the TDC data values when the target is at position X?" Oh, when the target is at position X its speed, range, bearing, AoB, will be this... enter. Sit and wait at 0 kt at periscope depth (realistic? :hmmm:) until target blunders perfectly into position X. Fire. Boom.

[I'm goin' down]

good explanation of setting up for the shot described in gutted's original post.

[Rocks'n'Shoals]

Hi fellow commanders!
I just came back from a long absence at subsim.com, and found an ongoing discussion about my little sharp-shooting tutorial which I wrote last year... Thanks to Rockin Robbins for answering many questions in the meantime.

293° bearing is just his "shoot course" or the absolute bearing to target when he launches torpedoes. This is why he has us keep pressing the "heading to view key" so we can place our periscope in the 293° true direction when our periscope has a 000-is-where-the-sub-is-pointing scale instead of the needed 000-is-where-the-north-pole-is scale. What's silly is that once you get a TDC solution you can simply mouseover the TDC window and read off the relative bearing to target for you solution eliminating the whole need to use that silly trick.Frederf is right here. I found out about that a bit time after writing my tutorial: You can read the relative bearing (where you have to point the periscope to) off the PK once you entered your solution, if you position your mouse exactly at the correct spot. Thus, no more need for the "heading to view" key which seems to draw so much discussion.

As I wrote in post #1, you can also easily read the relative bearing off the 360° bearing plotter on the nav map (just read the scale at the constant bearing line), if you have that mod installed.

Honestly I find the concept of picking your shoot bearing out of a hat and then determining the gyro angle from that to be a bit backward.Well, I liked the freedom it gives me, I can choose my constant bearing line however I like it beforehand. Of course, it simplifies matters and eliminates some possible errors if you set the line exactly at your sub's heading. Do that and you don't have to "wait at 0 kt at periscope depth", but you can actually move slowly forward (without turning), which is more realistic.

It's pretty easy to see that this is just "What are the TDC data values when the target is at position X?" Oh, when the target is at position X its speed, range, bearing, AoB, will be this...Correct, that's all it is about. Do it with some precision, and you get sure hits. This method gives you the time you need to do so.

[vgautham_91]

A splendid method. Thanks for posting it:rock:

[taukarrie]

"113 degrees, add 180 for left (western) side -> 293 degrees."


add 180 for left side.. what would if the target was on the right side?

[jazman]

It doesn't matter how fast the target is going...

Did you really mean this? I am not grasping it. Every torpedo shot needs to lead the target, because it's moving. The amount of lead is a function of the speed of the target. Help me here.

[magic452]

What Fincuan is saying is with a zero gyro angle firing solution the ship can be traveling at any speed, when you compute the lead angle you use the target speed to get the correct angle. The higher the speed the bigger the lead angle.

Magic

[jazman]

What Fincuan is saying is with a zero gyro angle firing solution the ship can be traveling at any speed, when you compute the lead angle you use the target speed to get the correct angle. The higher the speed the bigger the lead angle.

Magic

OK. For some reason with all these aiming things, I have to work it out on paper to understand fully, I can't intuit them, and even just reading about them is hard. I understand the O'Kane method fully, having done all the math.

[Frederf]

I appreciate your confusion. He's saying that once you compute the lead angle for a given target, that's all you need to know. Of course it seems a bit silly to say "it doesn't matter the speed" since the lead angle only applies to the result of target motion which is a direct function of its speed.

The speed does matter, but that's what the lead angle computation is for. Assuming your lead angle is still valid you don't have to mess with any TDC dials, including speed, because you've basically done the old TDC-less WWI method instead.

[I'm goin' down]

Playing with the Easy Aob mod, I forgot how simple it is to use the constant bearing attack. I sunk a warship at 3,000 yds, a freighter at 2,000 yds and four torpdoes missed a freighter at 4,000 only because it was the beginning of the war and they ran under its keel, even though I has set them to run at minimum depth. (After they missed, I checked the Attack Map and there were the four torpedoes, dead in the water, floating next the side the freighter they were aimed at.) For those of you about ready to tackle manual targeting, this is a good intermediate step to use with the O'Kane and Cromwell methods. It is extremely accurate, and in one of his above posts, gutted notes he has hit a target at 7,000 yds!

For TMO fans like myself, it is a technique that give your boat a decent chance of avoiding the dds, the scourge of TMO, that have the ability to lock on and track Allied subs at long distances.

Supplement: Just fired 4 shots at a cruiser at 7800 yds using constant bearing technique. I followed them all the way (it took ten minutes for them to run.) They missed by less than half a boat length! The cruiser was veering away from the torpedeos, and must have seen them as it increased its angle of veer as the torpedoes closed. The techique is pretty amazing.