SUBSIM Radio Room Forums - View Single Post

karamazovnew · 05-05-09, 05:58 AM

Hi everybody.
After many patrols using this technique I'm confident enough about it to share it with others. I haven't seen this described in any thread but I've seen many threads (I haven't seen them all of course) talking about this technique, but it was always much too complicated, described in too much detail, involving charts and wiz wheels. This is just a variation of the Fast 90 method made for Mikhayl's OLC gui version, that involves almost nothing more than the use of your sub's TDC. It can be applied to single merchants, or, at it's best, to a convoy row wipeout. It's even suited for colums of ships but the initial torpedo blasts will alert the other. I hope most of this will be new info to you. Just in case someone else described this method, I appologise and request a delete of this thread.

If the torpedo is shot at a 000 gyroangle, range is no longer important. Since the target's AOB, it's speed and our torpedo speed are all known, range will only define equivalent triangles of speeds. The lead angle can be offset to any bearing, for a more perpendicular intercept angle, but then the torpedo straight run becomes a factor. The range we input will tell the TDC how to deal with that factor. This seems to get complicated so let's just stick to 000 angle shots for a 90 degree AOB.

So we have 2 problems:
1: how do we obtain that easy 90 degree angle from 5000m away and only one sighting of the target?
2: at which bearing should the target be so that the torpedo will hit it with a 000 gyroangle?

The answer? Use the TDC. I strongly recommend using Mikhayl version of OLC interface. Unlike OLC's original gui, this one always shows the TDC settings on the periscope, even when autoupdate is turned on. Actually it was using this interface that i noticed the needles moving and came up with the idea so thanks again Mikhayl

.

Step one, attain a perpendicular course:
Let's say you have just spotted a ship at bearing 325 at 8 km and you can plainly see it. Is it heading touwards you? Can you intercept it now, or do you need to overtake it? Eyeball the AOB, you don't need to be exact now. You'll get better and better at it in time, as you close in for the shot. If you nail it within 10 degrees, the ship is toast anyway. All the following green text is for this example only. I've done this example mentally, without any target in my sight. Let's say the AOB is around 30-40 degrees port(left side), so the taget is closing. Good. Can we intercept it now? let's see:

1: Turn TDC Autoupdate OFF. This will break the link between the periscope bearing and the AOB.
2: Move the periscope to the target, let's say 323 now.
3: Set the AOB to 30 port.
4: Turn TDC Autoupdate ON. Try moving the periscope and you'll see the AOB updating. Yes you already knew that but how does that help you with the 90 degree course calculation?
5: Move the periscope left (in this case) and watch the AOB update. When it hits 90 port stop the periscope and press the "=" key to set a course to that bearing. For this, case it's around the 268 bearing. What course from north? Who cares?! Congratulations, you're now on a 90 degree perpendicular course. As you get closer and see the target better u can update the AOB anytime with the steps above to nail that angle a bit better.
IMPORTANT
6: As the AOB is still linked to the old periscope bearing, not to the ship's new bearing, remember to point the periscope at 000 and set the AOB to the corresponding 90 degrees. You can do this while you're still turning to your new course.

Can you intercept the target? After u've settled on the new course check the bearing again. Let's say it's around bearing 60 now. The aim is to get as close as possible but considering that you're going underwater at 6-8 knots (or 2-3 in case of warships), the target bearing becomes very very important. 60 degrees at a long distance will surely not be enough, 70-80 degrees is a safer bet so it's better to overtake the target for a few more kilometers than close in. So where do we turn to go parallel with the target? First make sure you did the previous Step 6. Just turn the periscope (with autoupdate ON) untill the AOB becomes 180(for closing and moving away targets) and head in that direction. As long as u have that AOB dial there u can use it to close in at any angle you want, then imediatly turn perpendicular. No need to remember any angle, any course, just watch the dial while you move the periscope.

Ok, so now you're in position, the AOB is 90 degrees when the periscope is at 000. Let's say the target is at 70 degrees and at around 2500m. Great. What should his AoB be? With the target centered, look at the AOB dial. Is it still correct? It should be 20 degrees but it's more like 45 degrees now. No problem:
1: with the ship centered, turn autoupdate OFF, and update the AOB to 45 degrees.
2: turn autoupdate ON again and move the periscope untill the AOB dial shows the proper 90 degrees. In this case it should be 25 degrees. Turn to that bearing and u're set.

Now the target is at 50 degrees. Time to calculate the speed. Ship Length, chronometer and the U-Jagd tool will deal with that in less than a minute, no prop counting or map charting for us. Let's say the speed is 8.5 knots. Enter that in the TDC for now. And now, the best trick. I remember struggling to understand the Wizz wheel lead angle calculation using target speed and torpedo speed. I remember having to use only fast torpedoes because all the charts were made for a 45 knot torpedo, those where the days... bleah. Try this....

So, ship AOB = 90 port when periscope is at 000, target speed 8.5 knots. Now just make sure the autoupdate is ON. The following is just a simple example of range cancelation.

1: move the periscope to 000. the gyroangle is 343 for me.
2: turn autoupdate OFF (and don't move the periscope anymore) and play with the range dial. The gyroangle will show values of 340-343. A bit too imprecise. just turn the autoupdate ON again.
3: move periscope until gyro is 000, should be at bearing 017.
4: autoupdate OFF again and play with the range. Does it change the gyroangle? Nope. It's rock solid at 000.
What does that mean? You know it: for THAT target speed, and for THAT torpedo speed, if you fire the torpedo when the enemy captain's hat appears at 17 degrees, the torpedo will hit (or, worst case scenario, go under the captain and hit his ship instead).

A word of advice: if u're using OLC's or Mikhayl's interfaces, never ever move the periscope with the mouse when autoupdate is OFF. When u release the periscope it will change the torpedo depth (OLC) or the AOB (Mikhayl). Just stay there and wait for the target to come in sight. If u have time, you can make another speed estimate. And of course, I guess you already know that shooting gas/steam torpedoes from long ranges will lead to misses and depth charges on your sorry stern.

This combines with the mother of all hits... convoy Front Row Central.
Convoys are equally spaced and follow a specific route. The front row might not be perfectly aligned, but the ships are almost always equally spaced. Let's say we have a 4 column convoy with ships at 1 km from eachother. That means the entire width of the convoy is 3 km. put yourself at 1 km away from the closest ship (1+3=4 well within the torpedo max range of 5 Km). All stop, periscope 1 cm above the water. You're perpendicular and the convoy is moving at 8.5 knots. u;ve done all calculations and the periscope is already at the proper bearing for a 000 gyroangle. Wait for the furthest ship to cross the line.. LOS; X seconds later the second furthest ship passes it... LOS; X seconds later another one... LOS, and X second later the closest ship passes the line LOS and get the hell out of there (i always go forward to the center of the convoy, not away from it). You'll only have about one minute before the torpedoes hit (slow electrics with impact detonators ofc). All 4 torpedoes should hit at the exact same time

.

What about for a column of ships. Well, it's a bit more tricky. Play around with the range dial for different gyroangles and you'll see that if the gyro is between 350-010, even for large variations of range, there's barely a degree difference. That might or might not be ok. I did hit 4 ships in a column but it was from 3000m away and the gyroangles were at 345/355/005/015. Just to be sure i did input the medium range (3000). Later I realised that the actual range was more like 3500m but who cares. The order or firing was: 1/4/3/2 so that they all get him at roughly the same time, barely 20 seconds between the first hit and the last. They were spaced like this:
1_____
____3_
_2__ 4

Last tip: Very very quick range estimate.

If you're using OLC's gui variants, there's a very fast way to estimate range. Changes in range are inverse proportional to height in degrees. All ships are between 40-60 m high. One degree equals 8000 meters. In other words:

1 degree=8000m
2 degrees=4000m (or 1 mark on Mikhayl's periscope)
4 degrees=2000m (or 2 marks on Mikhayl's periscope)
6 degrees=1500m (or 3 marks on Mikhayl's periscope)
8 degrees=1000m (or 4 marks on Mikhayl's periscope)
10 degrees=900m (copy paste...)
15 degrees="u're almost too close"

Thanks for reading, and, if you feel that this is new info to you but you find my explanation a bit too plain text, i might add some pictures later :P

EDIT: edited and renamed.

05-05-09, 05:58 AM	#1
karamazovnew The Old Man Join Date: Mar 2009 Location: Bucharest, Romania Posts: 1,403 Downloads: 151 Uploads: 0	Full visual TDC Technique (for Mikhayl's ACM mod) Hi everybody. After many patrols using this technique I'm confident enough about it to share it with others. I haven't seen this described in any thread but I've seen many threads (I haven't seen them all of course) talking about this technique, but it was always much too complicated, described in too much detail, involving charts and wiz wheels. This is just a variation of the Fast 90 method made for Mikhayl's OLC gui version, that involves almost nothing more than the use of your sub's TDC. It can be applied to single merchants, or, at it's best, to a convoy row wipeout. It's even suited for colums of ships but the initial torpedo blasts will alert the other. I hope most of this will be new info to you. Just in case someone else described this method, I appologise and request a delete of this thread. If the torpedo is shot at a 000 gyroangle, range is no longer important. Since the target's AOB, it's speed and our torpedo speed are all known, range will only define equivalent triangles of speeds. The lead angle can be offset to any bearing, for a more perpendicular intercept angle, but then the torpedo straight run becomes a factor. The range we input will tell the TDC how to deal with that factor. This seems to get complicated so let's just stick to 000 angle shots for a 90 degree AOB. So we have 2 problems: 1: how do we obtain that easy 90 degree angle from 5000m away and only one sighting of the target? 2: at which bearing should the target be so that the torpedo will hit it with a 000 gyroangle? The answer? Use the TDC. I strongly recommend using Mikhayl version of OLC interface. Unlike OLC's original gui, this one always shows the TDC settings on the periscope, even when autoupdate is turned on. Actually it was using this interface that i noticed the needles moving and came up with the idea so thanks again Mikhayl . Step one, attain a perpendicular course: Let's say you have just spotted a ship at bearing 325 at 8 km and you can plainly see it. Is it heading touwards you? Can you intercept it now, or do you need to overtake it? Eyeball the AOB, you don't need to be exact now. You'll get better and better at it in time, as you close in for the shot. If you nail it within 10 degrees, the ship is toast anyway. All the following green text is for this example only. I've done this example mentally, without any target in my sight. Let's say the AOB is around 30-40 degrees port(left side), so the taget is closing. Good. Can we intercept it now? let's see: 1: Turn TDC Autoupdate OFF. This will break the link between the periscope bearing and the AOB. 2: Move the periscope to the target, let's say 323 now. 3: Set the AOB to 30 port. 4: Turn TDC Autoupdate ON. Try moving the periscope and you'll see the AOB updating. Yes you already knew that but how does that help you with the 90 degree course calculation? 5: Move the periscope left (in this case) and watch the AOB update. When it hits 90 port stop the periscope and press the "=" key to set a course to that bearing. For this, case it's around the 268 bearing. What course from north? Who cares?! Congratulations, you're now on a 90 degree perpendicular course. As you get closer and see the target better u can update the AOB anytime with the steps above to nail that angle a bit better. IMPORTANT 6: As the AOB is still linked to the old periscope bearing, not to the ship's new bearing, remember to point the periscope at 000 and set the AOB to the corresponding 90 degrees. You can do this while you're still turning to your new course. Can you intercept the target? After u've settled on the new course check the bearing again. Let's say it's around bearing 60 now. The aim is to get as close as possible but considering that you're going underwater at 6-8 knots (or 2-3 in case of warships), the target bearing becomes very very important. 60 degrees at a long distance will surely not be enough, 70-80 degrees is a safer bet so it's better to overtake the target for a few more kilometers than close in. So where do we turn to go parallel with the target? First make sure you did the previous Step 6. Just turn the periscope (with autoupdate ON) untill the AOB becomes 180(for closing and moving away targets) and head in that direction. As long as u have that AOB dial there u can use it to close in at any angle you want, then imediatly turn perpendicular. No need to remember any angle, any course, just watch the dial while you move the periscope. Ok, so now you're in position, the AOB is 90 degrees when the periscope is at 000. Let's say the target is at 70 degrees and at around 2500m. Great. What should his AoB be? With the target centered, look at the AOB dial. Is it still correct? It should be 20 degrees but it's more like 45 degrees now. No problem: 1: with the ship centered, turn autoupdate OFF, and update the AOB to 45 degrees. 2: turn autoupdate ON again and move the periscope untill the AOB dial shows the proper 90 degrees. In this case it should be 25 degrees. Turn to that bearing and u're set. Now the target is at 50 degrees. Time to calculate the speed. Ship Length, chronometer and the U-Jagd tool will deal with that in less than a minute, no prop counting or map charting for us. Let's say the speed is 8.5 knots. Enter that in the TDC for now. And now, the best trick. I remember struggling to understand the Wizz wheel lead angle calculation using target speed and torpedo speed. I remember having to use only fast torpedoes because all the charts were made for a 45 knot torpedo, those where the days... bleah. Try this.... So, ship AOB = 90 port when periscope is at 000, target speed 8.5 knots. Now just make sure the autoupdate is ON. The following is just a simple example of range cancelation. 1: move the periscope to 000. the gyroangle is 343 for me. 2: turn autoupdate OFF (and don't move the periscope anymore) and play with the range dial. The gyroangle will show values of 340-343. A bit too imprecise. just turn the autoupdate ON again. 3: move periscope until gyro is 000, should be at bearing 017. 4: autoupdate OFF again and play with the range. Does it change the gyroangle? Nope. It's rock solid at 000. What does that mean? You know it: for THAT target speed, and for THAT torpedo speed, if you fire the torpedo when the enemy captain's hat appears at 17 degrees, the torpedo will hit (or, worst case scenario, go under the captain and hit his ship instead). A word of advice: if u're using OLC's or Mikhayl's interfaces, never ever move the periscope with the mouse when autoupdate is OFF. When u release the periscope it will change the torpedo depth (OLC) or the AOB (Mikhayl). Just stay there and wait for the target to come in sight. If u have time, you can make another speed estimate. And of course, I guess you already know that shooting gas/steam torpedoes from long ranges will lead to misses and depth charges on your sorry stern. This combines with the mother of all hits... convoy Front Row Central. Convoys are equally spaced and follow a specific route. The front row might not be perfectly aligned, but the ships are almost always equally spaced. Let's say we have a 4 column convoy with ships at 1 km from eachother. That means the entire width of the convoy is 3 km. put yourself at 1 km away from the closest ship (1+3=4 well within the torpedo max range of 5 Km). All stop, periscope 1 cm above the water. You're perpendicular and the convoy is moving at 8.5 knots. u;ve done all calculations and the periscope is already at the proper bearing for a 000 gyroangle. Wait for the furthest ship to cross the line.. LOS; X seconds later the second furthest ship passes it... LOS; X seconds later another one... LOS, and X second later the closest ship passes the line LOS and get the hell out of there (i always go forward to the center of the convoy, not away from it). You'll only have about one minute before the torpedoes hit (slow electrics with impact detonators ofc). All 4 torpedoes should hit at the exact same time . What about for a column of ships. Well, it's a bit more tricky. Play around with the range dial for different gyroangles and you'll see that if the gyro is between 350-010, even for large variations of range, there's barely a degree difference. That might or might not be ok. I did hit 4 ships in a column but it was from 3000m away and the gyroangles were at 345/355/005/015. Just to be sure i did input the medium range (3000). Later I realised that the actual range was more like 3500m but who cares. The order or firing was: 1/4/3/2 so that they all get him at roughly the same time, barely 20 seconds between the first hit and the last. They were spaced like this: 1_____ ____3_ _2__ 4 Last tip: Very very quick range estimate. If you're using OLC's gui variants, there's a very fast way to estimate range. Changes in range are inverse proportional to height in degrees. All ships are between 40-60 m high. One degree equals 8000 meters. In other words: 1 degree=8000m 2 degrees=4000m (or 1 mark on Mikhayl's periscope) 4 degrees=2000m (or 2 marks on Mikhayl's periscope) 6 degrees=1500m (or 3 marks on Mikhayl's periscope) 8 degrees=1000m (or 4 marks on Mikhayl's periscope) 10 degrees=900m (copy paste...) 15 degrees="u're almost too close" Thanks for reading, and, if you feel that this is new info to you but you find my explanation a bit too plain text, i might add some pictures later :P EDIT: edited and renamed. Last edited by karamazovnew; 07-28-09 at 05:12 AM.