Fast 90, where am I going wrong.

[TorpX]

Originally Posted by Zosimus

"... Turner had argued that maintaining a steady course for 30 minutes was necessary to take a four-point bearing and precisely confirm the ship's position, but on this point he received less support, with other captains arguing a two-point bearing could have been taken in five minutes and would have been sufficiently accurate."

I don't mean to argue for using or not using whatever hydrophone method, but you are taking the above statement out of context.

The ship's captain is interested in navigating. He knows his previous positions, speed and his present course; he really only needs limited supplementary info for safe navigation. Intercepting an unknown target on the basis of sound bearings alone is a much harder task, as you would not know it's course, speed, range, or really, if it is zigging or not.

[Zosimus]

Originally Posted by TorpX

I don't mean to argue for using or not using whatever hydrophone method, but you are taking the above statement out of context.

The ship's captain is interested in navigating. He knows his previous positions, speed and his present course; he really only needs limited supplementary info for safe navigation. Intercepting an unknown target on the basis of sound bearings alone is a much harder task, as you would not know it's course, speed, range, or really, if it is zigging or not.

The RMS Lusitania was was torpedoed and sunk by a German U-boat on 7 May 1915. This event caused the deaths of 1,198 passengers and crew. The quotation above was made by the captain to explain why he was not at fault for the sinking of his vessel.

So no, the captain is not only interested in navigating. He is interested in not getting torpedoed.

[Pisces]

Still, this does not sound like any proof or explanation of a solid method based on 2 bearings alone. Perhaps it is considered 'expert opinion' in that court case, but it doesn't show how it is done in practice. So that leaves nothing to verify it.

I guess you could do with just 2 bearings if you rely on the fading length of the line on the map, but that is nearing on cheating reality. With only a single ended line in a specific direction you cannot judge distance. So you can't plot 2 such indefinate lines and get a course from that. At best you can tell it has a course to either side if the bearing drifts to left or right.

[Zosimus]

Originally Posted by Pisces

Still, this does not sound like any proof or explanation of a solid method based on 2 bearings alone. Perhaps it is considered 'expert opinion' in that court case, but it doesn't show how it is done in practice. So that leaves nothing to verify it.

I guess you could do with just 2 bearings if you rely on the fading length of the line on the map, but that is nearing on cheating reality. With only a single ended line in a specific direction you cannot judge distance. So you can't plot 2 such indefinate lines and get a course from that. At best you can tell it has a course to either side if the bearing drifts to left or right.

First of all, I think that you are woefully ignorant of just how good the GHGs were. I think you should start by reading http://www.cdvandt.org/GHG1996.pdf to get some perspective. The distance between the GHG receivers was around 4.25x the distance between our ears, so as to take into account the different speed at which sound travels in water as opposed to in the air. Someone wearing these headphones could, therefore, point to the source of the sound as easily as you can point in the direction of a nearby barking dog.

Second, we know that GHGs came with a resistor that was used to decrease the level of sound. It came with hundreds of settings, but even assuming that it only came with 40, and assuming that a GHG can hear a lone vessel out to 20 km, that means that each setting shows 500 meters of range distance. Therefore the very idea that I should run around pretending that my GHG cannot tell me the approximate range of the boat is idiotic.

Furthermore, the very idea that using the capabilities that my u-boat comes with in the game, and most likely had in real life is "cheating" is insulting in the extreme. I do, therefore, request that you retract the statement.

[scott_c2911]

I feel I must reply to the last post due to the fact I believe I have also used the word "cheating" in this discussion. The reason I have used that phrase is due to the fact I have map contacts on and I found it a little too easy to determine speed by drawing a mark at t=0 and t=3:14.4 or to the layman 3:15. If you dont use map contacts then hats off to you with your 2, 3 and 4 bearing methods as I have no idea what your talking about. I have tried with no map contacts on and I hadnt got a clue. I freely admit ww2 sub drivers didnt have a super accurate spy satellite to help them but I am still learning how to do it with the aid of the map as it is. This post was about helping someone hit a target and I was trying to keep it as simple as possible for the op. I knew when I wrote that part of the post it might stir up a few anger issues however I felt it was outweighed by the fact I had called myself a hypocrit and went on to say that its not how you play but whether you enjoy playing that counts. I enjoy timing the target the stock way and I have had more success doing it so I tried to pass that advice on to the op. Im sorry if any offense has been caused.

[TorpX]

Originally Posted by Zosimus

The RMS Lusitania was was torpedoed and sunk by a German U-boat on 7 May 1915. This event caused the deaths of 1,198 passengers and crew. The quotation above was made by the captain to explain why he was not at fault for the sinking of his vessel.

So no, the captain is not only interested in navigating. He is interested in not getting torpedoed.

You can zig till your heart's content without taking any bearings whatsoever. He needed the bearings for navigation purposes. The point being that the two situations are not remotely comparable. The skipper of the Lusitania has much more information before he takes the first bearing, than any U-boat skipper would have of a potential target.

[Zosimus]

Originally Posted by TorpX

You can zig till your heart's content without taking any bearings whatsoever. He needed the bearings for navigation purposes. The point being that the two situations are not remotely comparable. The skipper of the Lusitania has much more information before he takes the first bearing, than any U-boat skipper would have of a potential target.

So you're arguing with me by agreeing with me? This makes no sense.

Obviously I have skipped a few steps in the explanation. Steps that I thought were obvious. Apparently, however, you aren't up to speed. Let me try explaining again in a simpler way that may be more appropriate to your knowledge base.

You see, there exists this thing called an ocean. It's filled with water. Goods produced on one side of the ocean often need to be used on the other side of the ocean. The method of moving the goods from one side to the other normally involves things called ships.

Ships are big metal containers with motors. The ships float because they are airtight and water does not get into them. However, during wars, another type of ship, called a submarine, often tries to pierce these ships so that they no longer float. When the ships stop floating, it's called "sinking."

The method of sinking ships normally involves something called a torpedo. A torpedo is a narrow tube filled with explosives and a motor. When launched from a submarine, a torpedo will (hopefully) intersect with the ship and then explode. If successful, this torpedo will cause the ship to fill with water and sink.

Now from the point of view of the skipper of the submarine, the problem is getting the torpedo to intersect the ship – not where it is now, but where it will be in the future when the torpedo arrives. In order to do so, the skipper will need to gather some information about the ship's speed, direction, and how often these things change.

Now the ship in question, known as RMS Lusitania, was torpedoed and sunk. With that fact in mind, we must realize that Kapitänleutnant Walther Schwieger apparently managed to solve the complex geometrical problem that faced him well enough to intersect the Lusitania with a torpedo thus causing her to sink.

Now the Captain of the Lusitania, one Mr. William Thomas Turner, was asked to explain why he didn't do a better job of ensuring that his ship didn't get sunk. Captain Turner claimed that it taken 30 minutes or more for the u-boat to acquire the exact heading of the ship using the four-bearing method. Thus, according to the Captain, it wasn't his fault that his ship got sunk.

Other captains, however, disagreed and pointed out that there is a simple two-bearing method that would have worked well enough under the circumstances and that doesn't take 30 minutes. It only takes 5-10 minutes.

So you see, TorpX, the subject at hand is not how a captain can zigzag a ship. It is not about what bearings a captain needs or doesn't need to zigzag a ship. Nor is it about what bearings the captain of the Lusitania might want or need to make. We are concerned entirely about the problem from the point of view of U-20, the German-made submarine that torpedoed the Lusitania.

If you still don't understand, maybe you can sit with your mommy and she can explain any big words that you don't get.

[Pisces]

With that kind of response I have no intention to continue this discussion. Zosimus, why do you feel threatened so much? There is no need to take this so personal.

[TorpX]

Originally Posted by Zosimus

......
If you still don't understand, maybe you can sit with your mommy and she can explain any big words that you don't get.

Being snotty doesn't make you smarter, or even appear smarter. You might want to think a little more before you post.

[Zosimus]

Originally Posted by Pisces

With that kind of response I have no intention to continue this discussion. Zosimus, why do you feel threatened so much? There is no need to take this so personal.

Good! Because, other than calling me a cheater, you contributed nothing to the thread.

[Zosimus]

Originally Posted by TorpX

Being snotty doesn't make you smarter, or even appear smarter. You might want to think a little more before you post.

No, before YOU post, you might want to actually understand what the person you are responding to is trying to indicate. Otherwise you end up with threads like the above.

For example, if someone writes: "My dog died when he was 24. He was old, sick, blind, deaf, and could barely move around. We finally took him to the vet and had him put down." then an appropriate response doesn't start by saying that your vet lived to 86 years old.

Why not? Because the age of the vet has nothing to do with the subject at hand. Even if you could prove to everyone's satisfaction that no vet had ever died under the age of 24 in the history of the universe, it still wouldn't have anything to do with the topic at hand.

It's the same thing here. The bearings taken by a ship's captain (regardless whether he is zigzagging) have nothing, zero, zip, zilch, nada, rien, to do with the problem of a u-boat captain hitting an enemy vessel with a torpedo and nothing to do with whether this problem can be solved by using a two-bearing, three-bearing, or four-bearing method.

In case that's not clear, let me restate it. I don't care ... not even in the smallest, part of my mind ... how many bearings a captain needs or doesn't need to zigzag effectively. I am concerned with the problem of the u-boat effectively calculating an intercept solution that's close enough for a two-torpedo salvo to hit with at least one fish.

[Sailor Steve]

Let me make something clear as well. Discussions are great. Disagreements are fine. Arguments are valuable. Dismissive language and insults are not.

Please keep it civil.

[Pisces]

Originally Posted by Zosimus

Good! Because, other than calling me a cheater, you contributed nothing to the thread.

I never personally called you a cheater. I did however say that the way the game displays the hydrophone bearings on the map, both in direction and length is cheating reality. This is of course not in anyway "bad" because SH3 is a game, and by definition it does that. SH3 is not a real simulator. And even simulators cut corners sometimes. So there is no need to feel threatened or consider your self attack as being a "cheater". If you want to play with the tools that the game gives you then that is OK and fine. I'm just saying in reality is wasn't so easy and reliable. Which I will explain next why I think that, based on the document you linked to. I have read it! In fact, I think I was the first one* that introduced it the SH3 forum to it by linking to this writer's site:

http://www.subsim.com/radioroom/showthread.php?t=130404

*: Ok, I forgot it was linked in the GWX 1.03 manual.

Why is the precise direction of the plotted bearing line 'cheating' reality?

Well if you read that document then you'll find that the bearing preciscion was very dependant on the frequency of the sound. Only with the higher frequencies (above 3 khz) could you get bearing precision narrower than 1 degree. Lower frequencies (in the order of 500Hz) give a much 'fuzzier' bearing, making the actual bearing somewhere in a range of up to 8 degrees. Which would make it a lot harder to find the center of the sound, just like listening to the sound manually at the station. And as higher frequencies decay in strength much sooner than lower frequencies these bearings would not have been as accurate at long range as the game portrays. Page 15 of the document you linked:

The British carefully investigated the capabilities of the GHG (Elac) apparatus in the captured U-570, in May 1942.
On successive selections of the high pass filters it was found that on the 6 kHz high pass-filter (utilizing the sonic spectrum between 6 kHz - 7 kHz), the bearing proved to have an accuracy of # 1°, for 3 kHz (utilizing the spectrum between 3 kHz - 7 kHz) the accuracy was . 1.5°, and for
1 kHz (utilizing the spectrum between 1 kHz - 7 kHz) the accuracy was . 4°, at 500 Hz, thus bypassing the high pass filters, the accuracy was decreased to. 8°.
Average merchant ships, cruising at 12-13 knots, produced a maximum sonic spectrum at 100 Hz and only 10% at 4 kHz. For destroyers cruising at 15 knots, the maximum sonic spectrum was at . 200 Hz, but still supplying 30% of its harmonic spectrum between, 4 kHz and 8 kHz.
Thus the proportion of sonic signal level left at the higher harmonics, had to be compensated for by increasing the amplification gain.

The question remains then how much this amplifier could enhance the higher frequencies without distorting the signal or flood it in self generated noise making it useless at longer ranges. This is hard to verify so long after the war, without first hand experience of the operators written down. (one of the conclusions of the writer)

Range determination based on hydrophone

The other place where I used the word cheating was in relation to the length of the hydrophone bearing line on the map in the game. Which as we know has the faint end of the line exactly ending at the source of the noise detected. Your eyesight, screen settings and antialias settings of your videocard determine if you get the right pixel spot on.
You state that the GHG or hydrophone had a resistor with which the signal strength could be reduced to determine the range of the source. You suggest that this variable resistor could be adjusted to get an absolute value on the range. Or at least get steps of 500m if it had 40 intermediate steps covering an expected max range of 20 km. However, I read that section about the resistor differently:
Page 3 of the PDF document:

All systems were subject to interference by the noise generated by electrical generators and other rotating devices, inside the submarine. The first step taken by the Germans to reduce this noise used a variable resistor parallel to the earphone circuit, a crude but quite common method used, in those days, to quantify the strength of a wireless signal. A special potentiometer was fitted with a 270 degree scale and was calibrated in ohms. The parallel resistance had to be reduced until the sound, in the headphone(s), had vanished. The signal strength was, for instance, considered as being 150 ohms. The value of the parallel resistance could indicate the increase or decrease of the sonic signal strength and allowed an approximate distance estimation, as well.
To reduce the man made noise picked up by the hydrophones, 1050 Hz band pass filters were inserted between the microphones and the earphones circuits.
The next step was to increase the system sensitivity, by adapting the valve amplifier used for the wireless station. Ships could now be observed up to 20 - 25 nautical miles, but greater attention had to be given to the reduction of man-made noise, from inside the submarine so as not to negate the improvements.

"could indicate the increase or decrease of the sonic signal strength"
- I read that as it could indicate a relative change in signal strength, and hopefully by relationship, distance.
What this means is that this resistor control could indicate if the sound source got stronger or weaker than to what it was calibrated. It does not say to which range it was calibrated. Which would require a known distance under the same conditions, which is something you don't have when you haven't located the target yet. In fact the writer mentions it is calibrated to a ohms value, not actual distance. And indicates that this can work upto 20-25 nautical miles, depending on the conditions. So, with background noises changing daily, or maybe even hourly due to the weather and internal conditions, this cannot be considered an indication of absolute range. It's only relative, and at best an indication of how much percentage wise the distance closed or opened up. That's why I feel the line length of the hydrophone bearing is not supposed to indicate the exact position. There is not enough variability in it to match the real world.

So, if you want to play the game as it is given then you should not feel offended by me using the word cheating. Especially as I wasn't personally addressing you. I'm just saying it lacks quite a bit in terms of realism, which understandably the game does not provide on all accounts.

Play as you like.

[Pisces]

Anyway, I still don't know how that 2-bearing method works.

[knight76]

Nup, I've read my first post a few times and just can't for the life of me find where I asked about realism in the game!

My issue was that using the Fast 90 attack that something was going awry and causing my tubes filled with explosives to not make the rendezvous with the intented water tight hull.

Anyway, on with the show.

I ended up having a great time attacking that convoy. I lay in wait sitting at 90 degrees with the lead destroyer already well past my position. Unfortunately whilst at Silent Running I hit a wrong button and made a little too much noise for short moment but this was enough to attract the attention of the lead destroyer.

With it running directly at me firing at my periscope, I sent a torpedo down it's throat and managed to sink it. Immediately set depth for 180m and crawled out of there. But did not escape the attention of the rear destroyer which proceeded to repeatedly depth charge me, though none were close enough to do any damage.

Eventually as the convoy sailed away, the DD decided he should probably catch back up to the convoy since he is the only DD on guard duty now. I decided to pop up and try to entice the DD back, even surfacing and firing my deck gun in his vicinity, but I could not goad him back to allow my to fire another torpedo down his throat like the first one.

Each time I would have him turned around and on his way back, he would return to the convoy just as fast.

I gave up and overtook the convoy to lay in wait again.This time sinking the rear DD as it maintained it's rear position. I did notice however, a distinct warship shape section in the middle of the convoy, but could not get a good look at it as it was obscured by other merchant ships.

Again, I overtook the convoy though laying ahead of their course no ships arrived. I was lucky enough to find them again 100km to the east of their previous track. They must have decided to take a lone evasive maneuver to avoid me as when I found them, they were headed back towards their original track. with the convoy now with no DD escort I lay in wait a third time. This time, I positioned myself ahead of the convoy in it's direct path and targeted a southampton class cruiser, I'm not sure why the cruiser didn't get in on the depth charge fun after I sunk the first DD but I'm thankful it didn't. It went to the bottom with 1 torpedo under the screws.

Whilst laying in wait for the convoy this third time, I noticed two red warship lines on my attack map, instead of just the one I was expecting. This second red line turned out to be an S type sub.

This set off a series of engagements with the sub both from long distance shelling and short range flak gun fire. You see I got a little annoyed that after sending 20 shells from my deck gun in to it's sides, it refused to sink, though it's shots hitting me cause all sorts of drama and flooding.

I sank to periscope depth and moved to a position just behind it, surfaced and engage the sub at close quarters with the aim of blowing it's deck gun out of commission. Which when given a good angle on it, I did just that. For the cost of two of my sailors lives who were manning the deck gun with me.

After this I left the S type alone and stayed out of range of it's flak gun which seemed able to cause flooding by itself.

From there it was a turkey shoot with a good number of merchant ships finding the ocean floor either through torpedo or deck gun attack.