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Old 06-01-2019, 07:11 AM   #16
gumbeauregard
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Default No Gyro Angle shots from any AOB

A few years ago when Hurricane Harvey was dumping millions of gallons of water on my roof I spent the inside time doing a couple of videos explaining how the basic firing angle is a simple trigonometry problem revolving around the ratio of the target speed to the torpedo speed.

The TDC in SH4 was not the easiest thing to get to work correctly so I rarely used it and developed this method (actually stole it directly from the guys who did all this for real). A "discussion" with another member who disagreed with this method prompted the videos

I have only fired three torpedoes in Wolfpack but I can see the theory behind this and learning the rules of thumb and having the prepared tables or calculator ready will make an excellent backup method for a quick shot or to confirm TDC setup.

Of course, one has to know torpedo speed as well as target speed or none of this works.

http://www.subsim.com/radioroom/showthread.php?t=233175

The original thread where I got my motivation to develop the two videos.

http://www.subsim.com/radioroom/showthread.php?t=232987

I am very excited about Wolfpack because I love the math behind plotting and executing an attack.

Last edited by gumbeauregard; 06-01-2019 at 07:46 AM.
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Old 07-20-2019, 08:37 PM   #17
kaptnkrunch
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Exclamation Question on fast 90 setup

"Turn your scope to bearing and that is your lead angle"

Well.. I am not sure I am reading the bearing correctly after setting up for fast 90.

There are 2 bearing dials - top one goes from 0-9 , bottom is 0-359

so.. which one am I adjusting the scope to?

Or maybe it's both.. both don't know how to read it properly?

Cheers!
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Old 07-20-2019, 09:18 PM   #18
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Default welcome aboard!

kaptnkrunch!
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Old 07-20-2019, 11:33 PM   #19
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Quote:
Originally Posted by kaptnkrunch View Post
There are 2 bearing dials - top one goes from 0-9 , bottom is 0-359

so.. which one am I adjusting the scope to?
Both dials display the same bearing, you combine them to read the exact bearings.
Lower dial e.g. show "20 plus a little bit", top dial shows "2.4", then the bearing is 22.4

Basically the top dial is just for the last digit plus the first position after decimal point, which would be impossible to read from the lower dial alone.

Just look at the scope bearing, which allows you to see the last digit (but not the exact first position after decimal point) and compare to what you see on the TDC, so you should get a grasp of it quickly.

The first position after decimal point is somewhat irrelevant for setting the AOB (just round it), but can be useful for calculations for e.g. "Auswanderungsverfahren" (whatever that's called in English, don't know).
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Old 07-21-2019, 09:07 AM   #20
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Danke PeterS!
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Old 07-21-2019, 09:24 AM   #21
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Auswanderungsverfahren = bearing change method!
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Old 07-22-2019, 12:38 AM   #22
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No need to guess the firing bearing. If you know the target speed, the firing angle does not change. All you need to decide is periscope left or right of 0. Look it up on the chart and set the periscope accordingly to generate Zero Gyro Angle,

Example: The target is doing 12 knots with 90 Starboard Angle on the Bow.

Firing Angle is 22 degrees. Note that firing angle and firing bearing are the same for Port AOB shots.

For Starboard AOB, subtract firing angle (22 in this case) from 360 to get the firing bearing of 338.

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Old 09-08-2019, 05:07 PM   #23
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Default Fast 90

Quote:
Originally Posted by gutted View Post
Approach from 90 degrees. Set scope to 0, set 90 AOB (port or starboard), input speed, ignore range. Swivel scope until the gyro reads 0 and thats your shoot point. It's not hard.

The only difference with this game is that you can't actually see the gyro while in the scope. So you have to disable the TDC from the scope then move the heading dial on the TDC (which should really be labeled bearing) until you find the bearing that zero gyro is on, then re-slave it to the scope and put the scope on that bearing. Or just have the man on the TDC tell you when the you are on the zero gyro.
Thank you. Did not realize someone replied to my comment.
I have the Fast 90/O'kane method well in hand now for Wolfpack.
Very easy. It also has the added benefit of making it easier to gauge the convoy speed by using only one of the escorts. In my opinion, it is MUCH easier to identify an escort for my speed determination than it is to identify a merchant. Sometimes the merchants can be tricky when they are massed together and the masts and kingposts get jumbled together.
I've been sinking ships at will while surfaced by myself quite successfully with this method.
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Old 04-10-2020, 01:37 PM   #24
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Default Thanks mate

This is just really cool. Having allot of fun with this. This procedure makes targeting very predicable.

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Old 04-10-2020, 04:32 PM   #25
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Aktungbby, I fail to see what your post has to do with Fast90/O'Kane method, other than confuse new captains.


Please elaborate...


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Old 04-10-2020, 11:57 PM   #26
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Quote:
Originally Posted by Jonny-Dog View Post
Aktungbby, I fail to see what your post has to do with Fast90/O'Kane method, other than confuse new captains.


Please elaborate...


Jonny-Dog
Sorry about any potential confusion. The diagram is from wiki's tdc site and has been used extensively by me and other old kaleuns. fixed.
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Old 04-26-2020, 07:00 AM   #27
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I made a video about this a while ago, also going into a little bit of detail (a very small bit) why this works (mathematically).
I can't say I agree that this works for different angles of approach as well (such as 75, 110, whatever) as those are not right triangles anymore. The further from 90 you are, the less accurate it will be in that case by quite some margin. It's still very much possible to figure out the lead angle then, but you need a bit different math (law of cosines, for example) for that.
I also feel that just setting the gyro to 0 on the Tvre and manually calculating the lead angle (or reading it off a a chart) is a bit easier and less prone to accidents than manipulating the Tvre to get there. That's just a matter of taste though, both are perfectly fine of course.

At any rate, here's the video.

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Old 04-26-2020, 07:10 AM   #28
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That’s a great video Jammo. Range ceases to matter at any impact angle, not just 90, so yes it will work at others as well and was the preferred method to use. Remember, all we care is the “lateral speed across the line of sight”, then we still have a right triangle. That’s by factoring in the sine of the AOB.

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

And since it was ballistically advantageous to have an impact angle of slightly less than 90, often times they will wait until the 90° AOB to even shoot. Then that’s simple as well, simply take the arcsine of target speed over torpedo speed, and then lead the course by that lead angle, such that when you pull the trigger the target it will be AOB 90 when gyro is 0. That way they also then had the added benefit of being able to recognize easily an AOB of 90 right at the shot as confirmation.

So for example, target course is 0, I put myself on course 270. I want to compute the lead angle at 90° AOB, target speed 8.5 and torp speed 30. I do the division, take the arcsine, 16.5°. I then turn to course (270 + 17) 287, and wait for the target to cross the wire.
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Last edited by derstosstrupp; 04-26-2020 at 07:31 AM.
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Old 05-26-2020, 11:56 PM   #29
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nice vid Jammo! Now can you do one with map tools and as little actual math as possible? (non 90°)

(like this: https://www.subsim.com/radioroom/sho...d.php?t=233175)

Last edited by II WO; 05-27-2020 at 12:05 AM.
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Old 05-27-2020, 08:45 AM   #30
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Thanks.


I'm not quite sure what you mean by that though... You mean, just shooting torps using map tools without calculating anything? Could be doable indeed... I was actually working on a tutorial on how to shoot based on matching speed and course (an idea I completely stole of Stosstrup, but he knows.).

At any rate, if there's something you'd like me to do a video on, let me know.
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