Fast 90, where am I going wrong.

[knight76]

I seem to be having trouble getting the fast 90 attack to work out. I used to attack with the Dick O'Kane 90 degree attack setting AOB to 75 and shooting along periscope bearing - or + 15 degrees from 0 or 180. This was in silent hunter IV.

This worked out well but meant you were fixed alot of the time on attacking along a set bearing, the fast 90 attack, in the U-boat gives you the option to look around and fire at will, grab a range and shoot.

I'm not sure where I am going wrong though, I am missing from ranges as close as 500m which is practically point blank.

Here is a run down of my attack procedure.

1) I get the sonar contact and run a course to jump well in front of them then setup on the 90 degree angle, this is done from their rough plotting of the sound contact at first.

2) Next up, I sit on the surface awaiting visual contact at which point I mark his position on my map. Then depending, I either measure his speed at that point, followed by a dive to periscope depth, or I go immediately to periscope depth and get the speed when he is a bit closer.

3) Method for getting speed is to measure time interval for 3 minutes plotting positions on map. 3 minutes due to the game being in metric.

4) As I have now plotted his course more accurately I re-plot his track and re-align to the new 90 degree angle.

5) I await his arrival at bearing 15 or 345 and shoot.

Now, here is some pictures of my attack setup which will show you my dials, map screen etc.

Pic 1: Shows my map picture of my step, im on the 90, just waiting now. I have set his speed, and re-plotted his track etc.


Pic 2: Target has arrived in my strike zone and is a bit wider than my plotted track, this would throw out my 90 degree setup maybe 1 degree I think. Also, I have moved in to improve my odds and am now sitting about 600m from the targets plotted course line.


Pic 3: These are all my settings, I am not looking directly at 0 degrees in my periscope here, but when I am, the gyro thingy is pointed at 0, and the AOB is at 90 degree to the direction the target is traveling, in this example, target is traveling right to left in front of me. You can also see my torpedo settings, these are just to set the torps to run shallow with impact detonators and that is it. It is early war. Speed was measured at 8 knots. Torp tubes have been opened also so this is not contributing to the situation. Toprs launch immediately.


Now, even though I am sitting at 600m from the targets track where it intersects my perpendicular track, in this case I set range to 700 as I found previously when I had set it to exactly as measured by the ruler, I had missed and thought the range may have been off. I manually took the range with the statimeter thing (ID target, measure mast height in periscope) once and it measured longer than the ruler. That shot missed aft so I thought my range via ruler may have been too short.

So that pretty much sums up my fast 90 technique, but I tend to miss most shots with it and I have no idea why. On my current patrol I have sunk 6 ships, all but 1 of them were via deck guns which I can get away with early war. But I would really enjoy hitting with a few more torps.

In the example above, I did hit with one but it was a dud, the second missed just barely aft.

I'd appreciate some corrective advice if I am doing something wrong or can improve my setup technique.

[scott_c2911]

Torpedo solution SOP.
Close to within 2000m of plotted target track and position yourself 90' to the track.
Identify ship accurately as soon as possible.
Slow to 0-1kts.
At target bearing 45' or 315' relative (AOB should be 45' port or starboard also) do an initial range measurement. Forget ruler on the map.
Use the stock method for gaining speed data. (Lock target and time the target for 30s using notepad stopwatch icon)
THIS ONLY GIVES AN ACCURATE SPEED READING IF YOU ARE AT 1KT OR LESS.
Forget 3.15 method although some folks have success with it.
Click on the tick on the notepad twice. One to accept the data and again to plug in solution. Remain locked on to target.
Set up torpedo depth using ship id book. The draft data is important here. If using magnetic pistols set it 1m below keel. If using impact pistols set up at mid draft.
At 10' or 350' relative open outer doors. When the sound has stopped fire your torpedo. To aim at particular points I unlock just before firing and aim directly at a given spot.

I have just started using manual targetting and I have had a 90% success rate so far using above procedure. Good luck.

PS Use T1 torpedoes and forget the T2s. They are shocking. If theres a warship around, dive deep and change course immediately after firing.

[Zosimus]

The problem might be with the 3 minute measure. The right time is 3:14.4 so if you have enough time, you should watch the vessel for 6:28.8 and multiply by 5 to get the speed.

[knight76]

See I thought the 3:15s timing was for imperial measurement and metric was 3 minute even?

scott_c2911 - Having read the forum I have seen comments stating the stopwatch gives inacurate speed measurements and the 3 minute style timer is more accurate.

I'll give the stopwatch a go, when clicking the tick twice, does this just enter speed data, or range and AOB data also?

If I was meant to be timing for 3:15s that may give the target another knot, so may explain why my torps tend to hit later than aimed, or just miss aft.

[Zosimus]

1 knot = 0.514444 meters per second.

Therefore in 3 minutes (180 seconds) @ 1 knot, a ship will have covered approximately 92.6 meters. In 190 seconds @1 knot, a ship will have covered 97.74 meters. At 195 seconds, a ship will have covered 100.3 meters.

Therefore, the rule of 3:15 (more precisely 3.14.4) is the amount of time that a ship traveling at 1 knot will need to cover 100 meters.

If you are timing for only 3 minutes, then you are getting 92.6 percent of the ship's speed. Therefore a ship traveling at, let's say, 7 knots, will show up as closer to 6.5 in your reckoning.

[Kip336]

It's been a while since I did manual solutions, but the fast 90 is a good way to learn! Soon once you get more comfortable with the process you'll start attacking with other AOBs.

I agree with Zosimus, use the 3,15 timer for better speed estimates.
another thing that helped me was to make a 90degree turn and to keep taking measurements, while also manually drawing bearing lines on the map.

The 90 degree Turn causes the bearing lines to shift, BUT, as the target keeps the same speed and course, there will be one line where the bearing lines are all equidistant from each other.
If this isn't the case, you know your calculations are off.

If I don't forget, I'll post a picture this afternoon after work

[knight76]

Thanks for the tips guys. I am very meticulous in my setups so I can't imagine there would be an issue with the 90 degree setup etc.

I think the problem is going to be the 3 minute timing. I even setup a spreadsheet to enter the data to try to convert distance traveled in 3 minutes to knots, but the game does not give increments only increasing distance in 100m lots. So it's not as accurate.

Can ships in game go 7.5 knots etc or are they always 7 or 8 knots?

I'll give the 3:15 timer a go tonight and see how that works out.

[Kip336]

Only on long distances (1000m + ) should half a knot start to matter.

3:15 is quite easy.
Take a location fix, 3;15 later another one. The distance between both fixes divided by 100 is speed in knots.

1200m travelled in 3:15, speed 12 knots
700m travelled speed 7 knots etc.

If the ship travels 650m, you can set the torpedo to 6,5knots with the dial.

[Pisces]

Just to make sure, did you mix T1 and T2 torpedoes in those tubes? If so then it may be due to a game bug. It doesn't update the torpedo speed calculation when you switch between T1 and T2 tubes. So the torpedo goes to the wrong gyro angle. If you do have both T1 and T2 in the tubes make sure you reset the right speed and re-aim before you shoot.

Other than that it might have been made worse by the 3m vs 3m15s confussion. If you want better resolution in the speed then take multiples of 3m15s: 6m30 and divide by 2, 9m45s and divide by 3, 13m and divide by 4. The latter gets you down to a quarter knot preciscion, which is what the user interface allows you to set visually anyway. You can't see it much more precise.

Target speed isn't always constant though. If it is wrestling with the waves then it temporarily slows down, which might just make it dodge the bullet. Remember that the 3m15s rule is an average speed.

Ships can go at any fractional speed that the campaign designer desires to enter in the editor. (the ship's max speed permitting ofcourse) So it's just a question how lazy he was. Don't count on whole numbered knots if you want to shoot accurate. Nature and physics doesn't count that way either in the real world.

[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.

[knight76]

No not mixing torpedoes just using the standard loadout.

I've been on my next patrol now just arrived on station, on the way had good weather so the 4 merchants I attacked were with deck guns. Still early war so they aren't armed yet.

At the moment I am lying in wait ahead of a convoy with a destroyer way out front and one way in the rear but none flanking the convoy. This will be a longer distance shot so I guess we will see if I score any hits

[Kip336]

Take out the rear DD, hide and take out the front. You'll have ample time to set up torpedo attacks and use a deck gun on the convoy from a few hundred meter :p

[Zosimus]

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]

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.

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.

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]

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.