Fast 90, where am I going wrong.

scott_c2911 · 06-30-15, 05:34 PM

I start from the top of the notepad and work down. Id is first, then range, then AOB. Without that data speed is hard to determine using the in game controls without using 3:15 method. I noticed that the gyro angle didnt change when clicking the tick once after timing the target and gaining speed data. I realised that I was just accepting the speed and not the solution. I clicked the tick again and the gyro angle was altered. This is a bit controversial but I consider the 3:15 method cheating but then Im being hypocritical as I play with map contacts on too, which is also cheating a bit. I can plot perfect intercepts exactly 90' to the targets track. At the end of the day its whatever you feel comfortable with and you enjoy. Theres no fun in sitting there for ages searching for contacts and finally missing it all together. The important thing is that the built in method for gathering speed data doesnt work unless you are practically stationary where the 3:15 method still works at flank speed. I can understand why its so popular but I have missed everytime I tried it.

Zosimus · 07-01-15, 02:52 PM

Quote:

Originally Posted by scott_c2911

I start from the top of the notepad and work down. Id is first, then range, then AOB. Without that data speed is hard to determine using the in game controls without using 3:15 method. I noticed that the gyro angle didnt change when clicking the tick once after timing the target and gaining speed data. I realised that I was just accepting the speed and not the solution. I clicked the tick again and the gyro angle was altered. This is a bit controversial but I consider the 3:15 method cheating but then Im being hypocritical as I play with map contacts on too, which is also cheating a bit. I can plot perfect intercepts exactly 90' to the targets track. At the end of the day its whatever you feel comfortable with and you enjoy. Theres no fun in sitting there for ages searching for contacts and finally missing it all together. The important thing is that the built in method for gathering speed data doesnt work unless you are practically stationary where the 3:15 method still works at flank speed. I can understand why its so popular but I have missed everytime I tried it.

I have no idea why you, or anyone else, would think that the 3:14.4 method is cheating. I also don't understand why people say it's 3:15. Doesn't 3:14.4 round down to 3:14? Not that it really matters.

You should easily be able to use the three-bearing method to get the target's exact course, and if you get a fourth bearing, you'll know his exact range, too. From there it's simple to plot his speed by measuring two points 6:29 apart. Multiply the distance in kilometers by 5 to get the speed. For example, if the ship has covered 1.4 km then you'll know his speed is 7 knots.

Personally I have found the two-bearing method to be good enough. Even from a hydrophone, the two-bearing method gives a course and range that's close enough for government work. Range, generally speaking, has a negligible effect on torpedo solutions. It's only important for setting the spread angle on salvos.

Pisces · 07-02-15, 01:26 AM

Quote:

Originally Posted by Zosimus

... I also don't understand why people say it's 3:15. Doesn't 3:14.4 round down to 3:14? Not that it really matters.

The 15 seconds is easy to see on the clock and add multiples in your head. It's easier to handle quarters of a minute than mentaly adding .23333 every time. That 1 second in 195 seconds total that it is off is insignificant.

Quote:

You should easily be able to use the three-bearing method to get the target's exact course, ....

And I don't understand why you say "exact" here. As the 3 bearing method is far from exact as a practical method. To get an exact course you need to know the precise bearings (at least 1 fractional decimal), otherwise it results in a range of courses tens of degrees wide. It tested this with my 3-bearing AOB slideruler, only using bearings rounded to the degree as the crew reports them. This depends much on how long the time intervals were. Longer time intervals results in more degrees between the bearings and makes the result more granular. Also the problem in is you are using intersections of lines that are almost parallel, and that can result in wildly varying course and range results. Doesn't matter if you use the formula, or do it graphically. If you rely on the map plotting the exact thin line bearing then this could be somewhat of a cheat, similarly to using the target icon markers when plotting, as it seems to be fairly precise. In reality hydrophone set could not give that level of precision.

Quote:

Personally I have found the two-bearing method to be good enough. Even from a hydrophone, the two-bearing method gives a course and range that's close enough for government work. Range, generally speaking, has a negligible effect on torpedo solutions. It's only important for setting the spread angle on salvos.

To my knowledge, there is no 2-bearing method that can give that level of information (course and range). Course needs at least 3 bearings. Otherwise you are assuming things that might not be true. Please explain how it works. Unless you mean 2 bearings with range measurements like the SH4 TDC does, or as on a maneuvering board is done. But that does not apply to SH3.

Zosimus · 07-02-15, 10:14 AM

First of all, I refer you to https://en.wikipedia.org/wiki/Sinkin...rt_proceedings wherein we read:

"Captain Turner gave evidence in England and now gave a more spirited defence of his actions. He argued that up until the time of the sinking he had no reason to think that zig-zagging in a fast ship would help. Indeed, that he had since commanded another ship which was sunk while zig-zagging. His position was supported by evidence from other captains, who said that prior to the sinking of the Lusitania no merchant ships zig-zagged. 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."

A two-bearing method is not as precise as a three- or four-bearing method. It is, however, good enough to get a u-boat into a solid firing position where last-minute updates and visual inspection can permit the final adjustments necessary to get the job done.

With nothing more than a hydrophone, a ship's approximate bearing and range can be known. This range is not that accurate, but I generally put a 200 meter circle around the ship's location to represent that the ship is "around there somewhere." This circle can show up differently on different zooms and will not be exactly on the ship depending on the zoom you use. Accordingly, it's necessary to use the right zoom and this is more an art than a science. Some practice will be required.

Some 5-10 minutes later a line can be drawn from the ship's old position (the center of the circle) through the ship's new position. Your sub can move during the procedure. The longer you permit between the two measurements, the more accurate the result will be. For example, you may find that the ship seems to be moving at 60º (ENE) or thereabouts. This is usually accurate give or take 2-3º either way.

When you are within 5000 meters of the ship, you can detect the ship using the periscope (weather permitting). Your TC will drop to 1 (depending on your settings). Pre-radar I just move forward at 2 knots with the scope up at TC 64 and I know the ship is 5,000 meters away when it gets spotted. From there I can draw the ship's course through its location (shown by map contacts) and go scope down for 6:29. In real life this probably would not have been necessary because I could have just ordered my hydrophone operator to count the propeller rotations and tell me the speed. I believe there's some sort of a mod that permits one to do so manually. Still, I have found 6:29 to be "good enough" as it gives me accuracy to within 0.5 knots. Ship's speeds will vary anyway depending on the weather – it's not uncommon to see ships vary between slow/medium depending on wave strength. That will tell you that it's 7.5 knots right off the bat.

After going scope up, if the ship seems to be on the line you drew, then the course is accurate. Alternatively, you can adjust it 1º either way and set up your firing solution. I generally fire a two-torpedo salvo and both hit about 70 percent of the time. Even if you're slightly off, one should still hit and that might be enough or you may have to follow up later with the deck gun. Even if both hit, sometimes one turns without exploding. These things happen.

TorpX · 07-02-15, 11:17 PM

Quote:

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 · 07-03-15, 08:39 AM

Quote:

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 · 07-03-15, 09:09 AM

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.

TorpX · 07-03-15, 10:11 PM

Quote:

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.

06-30-15, 05:34 PM	#1
scott_c2911 Engineer Join Date: Nov 2012 Location: West Midlands, Uk Posts: 203 Downloads: 71 Uploads: 0	I start from the top of the notepad and work down. Id is first, then range, then AOB. Without that data speed is hard to determine using the in game controls without using 3:15 method. I noticed that the gyro angle didnt change when clicking the tick once after timing the target and gaining speed data. I realised that I was just accepting the speed and not the solution. I clicked the tick again and the gyro angle was altered. This is a bit controversial but I consider the 3:15 method cheating but then Im being hypocritical as I play with map contacts on too, which is also cheating a bit. I can plot perfect intercepts exactly 90' to the targets track. At the end of the day its whatever you feel comfortable with and you enjoy. Theres no fun in sitting there for ages searching for contacts and finally missing it all together. The important thing is that the built in method for gathering speed data doesnt work unless you are practically stationary where the 3:15 method still works at flank speed. I can understand why its so popular but I have missed everytime I tried it. __________________ KLt S. Cooksey commanding U-2528 ... .. -. -.- / - .... . -- / .- .-.. .-..

07-02-15, 10:14 AM	#4
Zosimus XO Join Date: Jun 2014 Location: Chorrillos, Lima, Peru Posts: 401 Downloads: 3 Uploads: 0	First of all, I refer you to https://en.wikipedia.org/wiki/Sinkin...rt_proceedings wherein we read: "Captain Turner gave evidence in England and now gave a more spirited defence of his actions. He argued that up until the time of the sinking he had no reason to think that zig-zagging in a fast ship would help. Indeed, that he had since commanded another ship which was sunk while zig-zagging. His position was supported by evidence from other captains, who said that prior to the sinking of the Lusitania no merchant ships zig-zagged. 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." A two-bearing method is not as precise as a three- or four-bearing method. It is, however, good enough to get a u-boat into a solid firing position where last-minute updates and visual inspection can permit the final adjustments necessary to get the job done. With nothing more than a hydrophone, a ship's approximate bearing and range can be known. This range is not that accurate, but I generally put a 200 meter circle around the ship's location to represent that the ship is "around there somewhere." This circle can show up differently on different zooms and will not be exactly on the ship depending on the zoom you use. Accordingly, it's necessary to use the right zoom and this is more an art than a science. Some practice will be required. Some 5-10 minutes later a line can be drawn from the ship's old position (the center of the circle) through the ship's new position. Your sub can move during the procedure. The longer you permit between the two measurements, the more accurate the result will be. For example, you may find that the ship seems to be moving at 60º (ENE) or thereabouts. This is usually accurate give or take 2-3º either way. When you are within 5000 meters of the ship, you can detect the ship using the periscope (weather permitting). Your TC will drop to 1 (depending on your settings). Pre-radar I just move forward at 2 knots with the scope up at TC 64 and I know the ship is 5,000 meters away when it gets spotted. From there I can draw the ship's course through its location (shown by map contacts) and go scope down for 6:29. In real life this probably would not have been necessary because I could have just ordered my hydrophone operator to count the propeller rotations and tell me the speed. I believe there's some sort of a mod that permits one to do so manually. Still, I have found 6:29 to be "good enough" as it gives me accuracy to within 0.5 knots. Ship's speeds will vary anyway depending on the weather – it's not uncommon to see ships vary between slow/medium depending on wave strength. That will tell you that it's 7.5 knots right off the bat. After going scope up, if the ship seems to be on the line you drew, then the course is accurate. Alternatively, you can adjust it 1º either way and set up your firing solution. I generally fire a two-torpedo salvo and both hit about 70 percent of the time. Even if you're slightly off, one should still hit and that might be enough or you may have to follow up later with the deck gun. Even if both hit, sometimes one turns without exploding. These things happen.

07-03-15, 09:09 AM	#7
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,904 Downloads: 304 Uploads: 0	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.