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Old 11-28-21, 10:55 PM   #1
Captain_AJ
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Default Torpedo Firing solution

Back into SH4 after a couple of years off

Looking for a Cheat sheet with AoB, Firing Bearing . Speed of the Ship . Range is not a big deal , except knowing speeds of tyge MK14 Torpedo. Slow is 31Kts,9500Yds. Range Fast is 47kts 5500 yards range, Iamn using solution solver to get different virables but SO lazy to log all different Aobs. Just wanted to know if thewre is a printable cheat sheet already made up based On SOlution Solver . Thanks Yall
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Old 12-05-21, 02:06 PM   #2
Joe S
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This might help you , but you need an accurate estimate of the target speed. It would help very much if you placed yourself in a firing position so that your own course is 90 degrees to the target's track.
1) on a piece of paper, plot the location of your boat, pointing north.
2) draw a line at 90 degrees to your own track representing the track of the target.
3) assume your torpedo will hit the target when the target is directly in front of your boat, which would be at the intersection of your course and the target's track.
4) Range is NOT important here, but you must calculate how far the target will travel along its track in the time required for the torpedo to hit. Using whatever scale you decide to use, mark the point on the target's track where the target will be at the time of firing the torpedo. For example, if the intersection of your course and the target's track is 1,500 yds from your boat,your torpedo has a speed of 1,553 yds per minute ( 46 knots)
It will take your torpedo ..9653 minutes to travel the 1,500 yds to point of impact. In that period of time, your target travelling at 6 knots will travel 195yds.
On your sheet of paper, mark the spot on the target's course where the target will be, working backwards, at point of firing the torpedo.
5) Draw a line from your boat to the target. Then calculate the angle formed by the line of sight to the target and the line formed by the torpedo track, in other words, when the target is at the precise point that you calculated along its track, how many degrees of lead to you have to put on your torpedo to get a hit? In this example I came up with an angle of 7 deg.
ONce you determine that angle, it works no matter what the range is. So if the range is 500 yds, 1,000 yds, 1,500 yds, or 2,500 yds, if you have an angle on the bow of approx. 90 degrees, and the target is travelling at six knots, and you lead the target by 7 degrees, you will get a hit.

Once you work this out for the various target speeds you are likely to encounter, all you need to do is get an accurate target speed calculation and get into a firing position at 90 degrees to the target's track. Range becomed irrelevant at that point.
I hope this helps!
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Old 12-05-21, 09:20 PM   #3
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Common misconception here, but what dictates whether or not range matters is not the approach angle, it is the fact that the torpedo doesn’t have to turn. You could approach the target at a 45° angle, a 20° angle, an 85° angle, a 60° angle, doesn’t matter, as long as the Gyro angle is zero, range still won’t matter. Why is this so? Well, consider the formula for lead angle. It has no stipulation for approach angle:

arcsin ( target speed / torpedo speed * sin ( AOB ) )

The thing to tell people is to just limit the Gyro angle in practice to within 20° of their bow and range won’t really matter. The reason I speak up when I see this misconception is because it severely limits people tactically to only think in terms of approaching at 90°, when that’s not a requirement by any means to disregard range.

It is easy to convince yourself of this by just playing with the TDC dials. Set the bearing so that the Gyro angle is zero, then play with the range dial across its entire range of motion, at various angles on bow - hardly any change in gyro angle. Now do the same thing by making the Gyro angle large on the TDC and then play with the range dial, big time changes then.
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Old 12-06-21, 05:47 PM   #4
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Agreed that the approach angle has nothing to do with range, but a 90Deg approach angle gives you more target to hit and less chance of a miss.

Range does matter when doing a manual plot because in order to accurately determine speed you need an accurate placement of the target on the map. But for purposes of the original question, if you can determine how much you have to lead the target in terms of degrees from line of sight, ( for each target speed) range does not matter.
I think we are all on the same page her, or at least I hope so!

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Old 12-06-21, 07:05 PM   #5
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Oh yes I agree, sorry I misunderstood your post as saying it is limited to a 90° approach, it’s surprising how often I see that.

Easiest in my opinion is to do vector analysis. Anywhere on the map, draw the target course as a line, and make it a length equal to its speed, can be an arbitrary number but must include that number. Say if the target is going 6 knots, you can make it 6 m, 600 m, 6000, whatever, you get the idea. Now draw a line from target back toward your “boat”, with the protractor so you make the angle equal to the AOB you intend to shoot at. Make it an indefinite length but sufficiently long. That is the bearing line. Important: The angle between that line and the target course line you must make the AOB intended at the shot.

In similar fashion to how you drew the target speed vector using an arbitrary unit, do the same for torpedo speed. So if you are using a 30 kn eel, and you used 600 m for the target speed vector, use 3000 m for your torpedo vector. From the end of the target vector, draw a line 3000 m long, and where the other end of that line rests on the bearing line to the target, that is the third leg of the triangle. Measure the angle between the bearing line and the line you just drew - that is the lead angle, and depending on target bow right/left, that angle will be the shoot bearing (subtract from 360 if bow right).

Drawing this simple triangle is very flexible, and you can play around with it if you would instead like to predetermine an impact angle instead of an AOB, etc., by manipulating those two angles.
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Old 12-06-21, 10:08 PM   #6
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Here is my "device" to solve zero gyro angle shots:



Simply put, it's two angles and a circle drawn on the map (somewhere off in an area where you won't be sailing through. I draw it on an intersection of lines to keep things straight.)
The circle starts off at 4600 yards (MK14 fast torpedo speed is 46 knots. The size of this initial circle is different depending on the speed of the torpedo you are firing). Use this to position the first angle, one leg pointing to the center of the circle (representing your course), one leg pointing off wherever.
The second angle is centered on the circle, with one leg pointing south towards the first angle, and the other leg off elsewhere.
The center of the circle represents the torpedo impact point, the radius is the target speed, and the angles are the target course (relative to yours) and the lead angle.


It is now ready to be set up for the targeting problem.


First Exercise:
Target is traveling at 7 knots, with a course intersecting yours at an angle of 65 degrees. What is the lead for a 0 gyro shot?

Setup:
Adjust the circle to 700 yards (representing the 7 knot speed of the target).

Adjust the second angle to represent the the target course relative to yours. In this case, 115 degrees. (180 - 65 = 115)
Now, bring the second leg so that it crosses the intersection of the first angle and the circle. This intersection is your aiming point, where the target needs to be when you fire.

Read the angle at the bottom of the device. This is your lead angle, 8 degrees. Note that this is to port, so the actual angle is 352 (360 - 8 = 352).
Aim your scope down this bearing, and when parts of the ship (bow, stern, stack, bridge, etc.) cross the wire, launch the fish.





Second Exercise:
Target is traveling at 15 knots, with a course intersecting yours at an angle of 135 degrees. What is the lead for a 0 gyro shot?

Setup:
Adjust the circle to 1500 yards (15 knots).

Adjust the second angle to represent the the target course relative to yours, 45 degrees. (180 - 135 = 45)

Read your lead angle of 17 degrees. The target is crossing from starboard, so your actual firing bearing is 17 degrees. Aim, wait, and launch.








(Actual lead angles are 8.4 and 16.7, but the figures derived from this device are good enough to ensure a hit if the range is not excessively long.)
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