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Old 06-20-2020, 04:57 AM   #1
Krellian
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Default Calculating Transfer and Advance 90 degree turn

I'm following the Wreck 'em with no rec manual tutorial


Got a decent grasp of everything but, in video 4 I'm hoping to get a better handle on how he changes his 3500 meter calculation from the disc to a 2500 meter estimate after executing the 90 degree to port turn, when going into a perpendicular course with the target convoy.


Hamacher is kind of using the mast height at this stage to judge the 2500 meter mark as said in the video but, I'm trying to do it without mast height in this step.


Edit: I suppose I can figure that using the attack disc, I know Hamacher travels about 185m @3 knots during the 90 degree turn. I can multiply that by 4 and figure the radius of that circle and that probably equals both the Transfer and the Advance, so probably 117 meters for both during the 2 minutes and 345 meters for the cargo ships. Not a neat equation to do while sailing though. Will edit more with any updates as I work this out.



I think the answer is to calculate Transfer and Advance during the turn. It looks like it takes Hamacher 2 minutes to execute the turn. Over which time the target freighters would travel some x meters. If I could work out Transfer and Advance of the sub @ 3 knots during those 2 minutes I'd know the distance without using mast height.


http://shipofficer.com/so/wp-content...ng-Circles.pdf


I found this article interesting but, does anyone know a way to do transfer and advance calculations off the attack disc, or something like it?

Last edited by Krellian; 06-20-2020 at 10:00 PM.
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Old 06-20-2020, 06:38 AM   #2
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Hi, I am the creator, I could certainly help. When I’m close I generally eyeball ranges like that, but yes, you can certainly take the turn into account. I usually use a standard mast of about 35 m.

In reading through your posts I think you are definitely on the right track. I will say though that that kind of precision is not necessarily needed. When I’m doing a side attack like this, I try to get the gyro as close to zero as possible so that range does not matter to the solution. Range becomes more for situational awareness at that time.

Some of the attack planning steps in here, including that one where you’re trying to determine what speed to put yourself at the correct distance for the track, they are interesting, but I don’t use them in practice. They are instructional, but over time you just develop a feel for it without having to calculate it.
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Old 06-20-2020, 07:01 AM   #3
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Quote:
Originally Posted by Krellian View Post

Edit: I suppose I can figure that using the attack disc, I know Hamacher travels about 185m @3 knots during the 90 degree turn. I can multiply that by 4 and figure the radius of that circle and that probably equals both the Transfer and the Advance, so probably 54 meters for both during the 2 minutes and 345 meters for the cargo ships.
When you multiply the distance traveled during a 90 degree turn by 4, you get the circumferenc not the radius. Divide the circumference by 2*pi to get the radius.
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Old 06-20-2020, 08:14 AM   #4
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Default Thanks!

Thanks for the videos derstosstrupp! Taking notes and learning a ton.
Definitely understand using a default 35m mast it makes things quick and easy. Just refining a bit and trying to beat the disc a bit and make it do some more tricks haha. Actually helps just learning to use it better as per the video so it's been a fun exercise if nothing else.
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Old 06-20-2020, 08:17 AM   #5
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@neistridlar 185m to complete a quadrant * 4 = circumference of 740 with radius of 117.7 no? Thus: Transfer & Advance probably 117ish?
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Old 06-20-2020, 05:13 PM   #6
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Yes, that sounds about right. Reading your OP back now, I think I may have misinterpreted what you meant. Combined with possibly a misspelling of 117m, turned 177m, reinforcing my interpretation.
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Old 06-20-2020, 05:23 PM   #7
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Quote:
Originally Posted by Krellian View Post
Thanks for the videos derstosstrupp! Taking notes and learning a ton.
Definitely understand using a default 35m mast it makes things quick and easy. Just refining a bit and trying to beat the disc a bit and make it do some more tricks haha. Actually helps just learning to use it better as per the video so it's been a fun exercise if nothing else.
Very happy to hear that people are getting something out of them!
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Old 06-20-2020, 09:41 PM   #8
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Default Think I got the calculation...

Ok, so in the video where the 37 degree bearing and 3500 meter distance is calculated I think I know what to do, assuming we don't want to use a 35m mast default.


Steps


1. Immediately initiate the 90 degree turn to port after the 3500 meter distance is marked
2. We know from the current disc reading, that our distance to intercept was a little over 2100 (2106 to be precise)





3. We know (from a slide rule that I'm still looking for) that a 185 meter course turning 90 degrees at 3 knots gives us a 185 meter quadrant which, gives us a radius of 117 for that quadrant. (Would be nice to be able to calculate this using just knots and the rudder)



4. Subtract 117 from 2104 and let's just say it's 1990. (Note: we are only using the 117 Transfer. We don't need to worry about 117 advance, or the target ship's advance towards us in this time because we will do a bearing check instead and that will take care of it for us.)


5. While in the turn, set the needle at 1990.


6. Right when the turn is finished and we are on our new course, mark the bearing of the vessel used to calculate the original 3500 range. It should be about 50 degrees. The flip side of that is 40 degrees. Line up 1900 with 40 degrees. Then use the other needle to mark 50 degrees.


7. The 50 degree mark is how far that ship is from the intersection point. About 2340ish. From this we can recalculate how far that ship is from us but, we shouldn't need to now. We can just adjust speed to get 500-1000 meters from the intersect point and if we need to, calculate how fast the target will get there




Last edited by Krellian; 06-20-2020 at 09:55 PM.
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Old 06-20-2020, 10:00 PM   #9
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Quote:
Originally Posted by neistridlar View Post
Yes, that sounds about right. Reading your OP back now, I think I may have misinterpreted what you meant. Combined with possibly a misspelling of 117m, turned 177m, reinforcing my interpretation.

Oh lol sorry, I will edit that. Was drunk and typing on a half broken keyboard at 1am.
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Old 06-22-2020, 12:01 AM   #10
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Quote:
Originally Posted by Krellian View Post
...
3. We know (from a slide rule that I'm still looking for) that a 185 meter course turning 90 degrees at 3 knots gives us a 185 meter quadrant which, gives us a radius of 117 for that quadrant. (Would be nice to be able to calculate this using just knots and the rudder)

...
I believe I have left a procedure in here somewhere to calculate the turning radius with attackdisk/sub-buddy app. No need for speed or rudder deflection, just odometer movement in the turn and the angle of the turn. And a magical mark on the time-disk representing 'degrees per radian': 57.3 seconds (on the beige scale) or 573s/ 9m33s on the white scale.

Found it: https://www.subsim.com/radioroom/sho...81&postcount=7

Last edited by Pisces; 06-22-2020 at 12:10 AM.
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Old 06-22-2020, 05:15 AM   #11
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That's the one! Holy cow right there. Thanks


I have the 185 marked there at the top (1850, treated as 185) with 90 degrees or (1-30) and the 9:33 minute mark points to 117 bingo.



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