Guides and Training

[Hitman]

I haven't found any actual wartime references to taking prop counts and I have a fair collection of WWII related submarine books

That's interesting, I though I had readed something about it in one of O'Kane's book, must be wrong. What I can confirm is that Erich Topp's sonarman certainly did estimates of speed based on propeller counts. NOt only have I readed it in a book, but there is also video footage in which he appears doing that during Operation Drumbeat.

[Distortion]

Originally Posted by magic452

Distortion The values for the lines are 100 yards for each knot of torpedo and target speed. Ex. Mk 14 high speed is 46 knots, your course line would therefore be 4,600 yards long. Target speed of 5 kn. = 500 yard speed line.

You can shoot anywhere along the course line more than 500 yards (arming distance) but not beyond it, the torp won't travel more than 4,600 yards on high speed.

Spectator explains it much better than I can in post #55 in this thread.
He uses an approach angle of 90° but it works at any angle, I always use something like 60°.
Vector analysis is a firing solution method so you must be in range of the torpedos for it to work,


Magic

Cheers magic, I feel kinda stupid But now it all makes sense.
What I did was a run to the end of the 1hour speed line/course of the target, but sometimes I didnt have the time to do plotting.
Thanks m8

[Rockin Robbins]

Yes, it's really easy to forget that all we're doing is drawing a scale model of the firing solution and start to confuse 4400 yards on the graphic solution with an actual 4600 yards distance required to make the shot.

Keep practicing and it all becomes automatic. But when you're first learning it's easy to become confused about all the details. Keep up the good work!

Hitman, the fact that the Germans did it could have lent a halo effect to the assumption in American sub movies that Americans did it too. The Germans had some important advantages. First the Atlantic was crawling with hundreds of pretty identical cookie-cutter Liberty boats. Once you learned the RPM/speed curve for one you had the keys to the city. Also the open nature of American and British societies, where information valuable to enemy combatants easily enters public knowledge, made information on our merchant shipping much more accessible than the relatively closed society of Japan.

[Hitman]

First the Atlantic was crawling with hundreds of pretty identical cookie-cutter Liberty boats. Once you learned the RPM/speed curve for one you had the keys to the city. Also the open nature of American and British societies, where information valuable to enemy combatants easily enters public knowledge, made information on our merchant shipping much more accessible than the relatively closed society of Japan.

Cheers, good observation

As far as I have seen, boy have you guys been able to capitalize on any new idea that someone has pointed out! The cold war american sonars were simply the best, despite germans having lead the way to that rpm count, and I always like to remember the memorable sentence from Jules Verne in his novel "A Journey to the Moon", where he said "What an american can imagine, another one can do it"

In any case, I wanted also to pay another tribute to the John P. Cromwell attack method (45º AOB shots) with something I recently readed:

The very same U-Boot Commander's Handbook says:

95.) When attacking ships with low and medium speeds, at close range, it ballistically advantageous to fire at an angle of the target of 90, as errors estimating the position will in this case have the least effect, besides which the speed of the enemy can be most accurately gauged in this position. If the range is longer (over 1,000 m), and the target is traveling at a high rate of speed, an attempt should be made to launch the torpedo at a smaller angle, say, 60.

Since the angle the book is referring to is the opposite to the track angle, it is in fact recommending a 40º attack , i.e. the John P. Cromwell one!

Amazing

[Rockin Robbins]

Amazing find! Yes, the John P Cromwell is a finicky beast too! If you're firing torpedoes in the daytime, you'd better be using electric eels. Especially if you're launching them with a longitudinal spread, all in the same line, all the target has to do is turn into the line of fire and watch them all miss.

But with electric torpedoes, the game changes entirely in your favor. The effective speed of the torpedo is greater because the closing speed with the target gets a healthy assist from 70% the target's own speed plus the speed of the torpedo. With a 31 knot Mark 18 and a 20 knot target, that's a healthy 45 knot closing speed! With no wake! This is calculated from the standard 45º attack.

Also those nasty warships have a habit of detecting you just before you unleash the Dick O'Kane shot. Then the whole plan goes to worms, you try to get a quick down the throat shot, which just puts you at death's door when you miss... It can be very bad for your disposition.

Yes you hit on a great point. The John P Cromwell is for warships! And we're not doing anything new. Those WWII sailors were pretty sharp!

[Hitman]

And we're not doing anything new. Those WWII sailors were pretty sharp!

Ah, you touched now a sensible point in me! I am a great enthusiast of the classics (I mean roman and greeks!), and did you know? The romans had a saiy that goes like this: "Nihil novum sub solem" which means in latin "Nothing new under the sun", i.e. we are continuously reinventing the wheel , but those before us knew that already!

Not a long time ago, I was developing a method of determining AOB based on "aspect ratio", and once I had finished, you know what happened? I discovered that by 1912 the periscope manufacturers Zeiss (German) and Barrs& Stround (Britain) had long ago developed such a method! And me, here, thinking I had found the keys to the holy grail

So, when I read books like those from O'Kane, Kretschmer and similar aces, I just can think: "Respect, man!" Those guys knew the same you just have found out, but decades, or even centuries before

[Distortion]

Yeeeaaah, on my 1st patrol, using the vector analysing, I`v got myself a nice Kongo class ship, and sink it with 3 torpedo`s. It was a convoy of about 2 Kongo`s in the middle, defend by some destroyers, and cruisers. My first plan was to use slow and fast torpedo`s, and put both kongo`s out of action. That didnt worked well. For the first kongo I used slow torpedos, with a speed of 31 knots. For the second I used fast torpedos with a speed of 46 knots. The speeds of the targets was 14.5 knots. I draw 2 line for the torpedo speed, one 3100 yards, the other 4600 yards, and calculated the lead angles. Strange thing it the slower ones didnt hit the target, the fast ones did. What gives? Do I need another tactic with this one?

thanks guys

Robert

[Rockin Robbins]

Error tolerance, man! When you're out there bobbing around in the big green ocean, there are errors in every measurement you make, especially in target speed. Warships love to speed up and slow down, zig back and forth and generally screw up our magnificent vector triangles. And they are moving fast. A small error can make us miss, not just hit an unplanned part of our target.

So everything we do in putting together an attack plan should have one goal in mind: mitigating the effects of inevitable error. The absolute BEST factor in that is torpedo speed. The faster the torpedo speed, the more error tolerant your solution.

Three rules for maximum error tolerance:

GET CLOSE a shot from 700 yards gives the enemy almost no time to avoid and is twice as error tolerant as a shot from 1400 yards.

WATCH YOUR TORPEDO TRACK ANGLE that's the angle at which the torpedo strikes the target. The closer to 90º the torpedo is, the more error tolerant your solution. As mentioned above in another post, there are reasons to toss this one out the window with warships.

USE THE SMALLEST POSSIBLE GYRO ANGLE preferrably zero, with the vector analysis attack. This eliminates range from the solution and is possibly the most important factor in mitigating error if you have no radar.

USE FAST TORPEDOES discussed above. The faster you can get the boom to the target the less time there is for something to go wrong. And the difference in impact point along the target length for a given error is larger or smaller in proportion to the torpedo speed, with the faster torpedo having the least variable impact point.

One, two three.........more than three. See? There is error in my targeting solution. And a final thought: you're going to have some misses. I have lots of them. If all you shoot is the sure things, your score isn't going to be very good. Take your misses with a smile and learn from them. No guts, no glory.

[Distortion]

I`l guess you are right, I trust to much on my calculations, and the fact that the enemy screw things up. Thanks for your tips, really appreciate it.

[Frederf]

Originally Posted by Rockin Robbins

WATCH YOUR TORPEDO TRACK ANGLE that's the angle at which the torpedo strikes the target. The closer to 90º the torpedo is, the more error tolerant your solution.

How do you explain this diagram?

[Don_D_Dwain]

Hello Guys,
I did not see this in the thread, but I just skimmed over it , so if it is there, please disregard this comment. As you probably already know, the Germans developed the first homing torpedo. One of them, the G7es (Falke), was used but reports that it was too slow to be useful (20 kts), and the target vessel needed to be going at least 12 kts (I think), for it to home in on. When I go out for a patrol, I have one of these fish in my rear tube (lol, ok no pun intended), just sounds funny. If you should happen to come across a Pesky escort that will not leave alone, or if you absolutely have to get rid of him, then try this. WARNING: it is a VERY RISKY tactic. At a distance that you determine is safe enough for his GUNS not to hit very accurately, at you stern, you SURFACE, to let him see you. Make sure your stern tube with the FALKE is open. When he gives chase, SUBMERGE to Periscope Depth, and turn till he is about 180 Bearing. Remember, this is RISKY. Take a set of Range, Bearing and Speed, all does not need to be very accurate, as long as he is close to 180 from you. Now, the same as when a cop is running radar, he will see you, and the chase is ON. Let him come a bit closer, launch your FALKE, and shut your engines off and DIVE. The rest is HIS LUCKY DAY. Thanks.

[Rockin Robbins]

Originally Posted by Frederf

How do you explain this diagram?

OK, I've gotta hit the books. I want to be right and easily understood on a graph that's darned difficult to read! Stand by......

Beginning to understand...... Processing.....

[magic452]

@ Distortion Good work on the vector shots, to get two different ships at once takes a little practice.

You can shoot both a 31 Kn and 46 Kn vector solutions at the same time.

What I do is approach the target course line at about 60° AoB.

For a convoy pick a target in the first column for the 31 Kn shot and a target in the second column for the 46 Kn. shot. With a 60° AoB the two ships will almost overlap at the time you shoot. The slow speed will hit first so you must adjust your targeting towards the stern of the second to allow for it slowing down. Did this just yesterday for a total of 18,000 tons, two very large freighters. You want to shoot from about 1,700 yards so the high speed torps have a chance to catch up with the slow ones.
With a little experimenting with the range you should be able to get almost simultaneous hits on both ships.

What Rockin Robbins says is very true, You must get very good speed and course data and be able to adjust for conditions and errors.
With a 60° approach you must get everything right, there is little room for error. When trying to shoot both high and low speed the range is critical so you get near simultaneous hits and it takes somewhat longer ranges to do this.

As with any firing solution, conditions play a big part, very good visibility may allow the target to see the torpedo wakes and start to slow and turn.
If possible I will tail the convoy and try to set up a night attack.

Haven't tried this against warships yet, they are a different can of worms.
They see the torpedos sooner and react faster than merchants.

I may have a shot at it tomorrow. Setting up on 5 ships running line astern. Don't know what they are yet but looks like warships. I have an early save so I can try different set ups. This will be a night attack so I think I can pull it off.

Good luck and good hunting. Stick with the vector shots I think you will like them.

Magic

[Distortion]

@ Magic

Thanks for your reply. But if you know the distance between the two vessels, and if they running the same speed, I thought it is possible to just arrange the heading of the periscope, hit the send button again, and fire the other two fast torpedos? Problem is, how do I plot that on the map?

[Rockin Robbins]

OK, here's the deal on Frederf's chart above. If you think about it, your lead angle changes, depending on the angle on the bow of the target. To take an extreme example, when the AoB is zero he's headed straight toward you. There is no lead angle at all! You just set speed to zero or AoB to zero and if your bow is pointed at the target, out comes a zero gyro angle shot.

However, when you are at AoB 90, the target has the highest apparent motion from left to right or right to left and you must make a maximum lead angle ahead of the target bearing to achieve the boom.

So you can see that as the target approaches, the lead angle is constantly changing. However, the graph doesn't graph target bearing. It graphs torpedo track angle. You may swear now. Oh, they're not tracking real torpedo track angle, but pseudo torpedo track angle! @#$@#$%@#$ I'm going to have to pull out a chart here.....



Now your sub is on the right end of the sub's course line. Yeah, I know that's not obvious. Why didn't they just SAY SO???. Point P is the periscope. The middle line between M and P is the bow of the submarine. Point M is the end of the torpedo's straight run, where it turns to its set gyro angle along the curved course to the torpedo track toward the target. Kapeesh?

Actually that's not going to matter much, because in the special case these graphs show, the deflection angle is exactly equal to the periscope lead angle. They don't explain that in the Submarine Torpedo Fire Control Manual, they just claim that "From a study of the curves it is evident that..." NO, IT"S NOT EVIDENT!!! THAT"S WHY WE"RE LEFT WITH THESE FREAKIN' QUESTIONS!!! Thank you, I feel much better now.

To further muddy the waters, the manual doesn't say what the optimum periscope bearing to fire is, it relates everything to the resulting angle the torpedo takes when striking the target, measured from zero at the bow to 180 at the stern. So to make any sense out of what they say you have to reverse engineer all the gobbledygook.

I've done that. You're going to laugh. All the charts can be used to start campfires or something. Let's take the chart you used above.



Let's take the bottom curve, for 8 knots. The deflection angle is the exact same as our lead angle because they're all zero gyro shots. It says if the track angle is zero (you are shooting directly at the bow), the deflection (lead) angle is zero, you don't have to lead the target at all.

But as the angle on the bow, which is a bit less than the deflection angle, increases and the target bears more and more boadside the lead angle increases until you get to the optimum track angle, where the curve levels off and starts to fall again.

In the shaded area, between a 90º track angle and the next radial line over, where the lead angle is again the same as a 90º track angle, the lead angle changes least for each degree of target bearing. So shooting a torpedo track angle in that range will give you the most error tolerance possible. Gee, I think I've talked about building error tolerance into our attack plans before!

Well, all thse graphs are very fine and great for impressing girlfriends over dinner if you've run out of things to talk about, but what in sam hill do they mean? You're gonna die...

Shoot from a course at right angles to the target track, ala Dick O'Kane and fire when the target bears 0º. The torpedo will automatically (if your TDC is set for AoB 90º and correct target speed) take the optimum track angle toward the target. If you care about the resulting 10º to 20º gyro angle (you shouldn't worry about gyro angles of less than 30º) you can alter your course to about 110º from the target track instead of 90º. This will reduce your gyro angles in all reasonable circumstances to less than 5º. I'm not going to worry about it myself.

Now you can go make paper airplanes from those pretty graphs and use them to entertain children. Yup, there's the right way, the wrong way and the military way. Welcome to the military way to make the simple into brain surgery...