SUBSIM: The Web's #1 BBS for all submarine and naval simulations since 1997 
06192019, 06:57 AM  #1 
Officer
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Slide Rule Targeting Series
Always wanted to make a detailed series of videos on the use of the attack disk and speed side, so here we go!
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06192019, 07:01 AM  #2 
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Part I: Intro to Attack Disk and Speed Disk
Part II: Calculations at Distance Part III: Target Speed Calculations Part IV.I: Correction to Aspect Ratio Calc Part IV.II: Calculations to Position for Shot
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Comprehensive Tutorial (For Wolfpack): https://docs.google.com/document/d/1...it?usp=sharing Excel File for Tutorial: https://docs.google.com/spreadsheets...it?usp=sharing Speed Tables: https://drive.google.com/file/d/1sQq...ew?usp=sharing Last edited by derstosstrupp; 06192019 at 11:50 PM. 
06192019, 09:44 AM  #3 
Silent Hunter

Sorry Matt, but you are not getting of the hook that easily with the aspect ratio AOB video. You got your observed sizes wrong. If you find that the resulting angle is supposed to be right of 90 degrees on the angle disk then you need to reasses them. The nominator (observed aspectratio) must be smaller than the denominator (real aspect ratio). Fudging by flipping the numbers may have worked here to get close but does not solve the problem.
Real aspect ratio: 150(.0)m over 28m (using 280 seconds or 4m40s on the time disk) points to 5.357ish on the distance scale. Observed aspect ratio: you took 14.6 length vs 2.7 height. You shifted the disks a bit too far resulting in 5.44. Proper placement of the marks would be 1460 distance against 4m30s time, pointing to just over 5400 on the index. 5.407 according to a calculator. Your nominator being larger than the denominator does not allow to compute the inverse sine. The division of observed over true aspect ratio must be below 1. I don't blame you though. I am sure it is hard to keep a good focus while making videos and providing commentary on what you are doing. Mistakes are easily made. Personally I eyeball the observed length at 10m33 to be 14.3, and height at 10:59 to be 2.8. Resulting in a aspect ratio of 5.1(07) (using 1430 against 4m40s on the time disk) Making my inverse sine calculate to 72ish degrees. But one has to keep in mind that the same inverse sine result applies to angles equally distant to 90 degrees. The sine of 80 degrees is the same value as the sine of 100 degrees. So the AOB based on my measurements could also be 108 degrees. Now, me being able to compute a result does not mean that I am right in my measurements. From the view to the target when you can see that is showing the backside of the forward bridge structure. Indicating AOB is larger than 90 degrees, so close to 108. But infact a little time later the map shows the AOB to be 99. Which goes to show this method is not really appropriate to AOB angles close to 90 degrees. You will only get a ballpark result. Onbow or onaft AOBs work out more precisely. But then beamwidth also comes into play. Yeah, science is messy. And if people have not noticed yet. It really helps to know your tables of 6(0 seconds) to come up with the equivalent mark on the timedisk representing desired numbers. Like 28 not having a mark on the time disk. But considering a full lap on the disk is a multiplication by 10, it is the same mark as 280. Knowing that 280 = 240+40 = 4*60 +40, it is then located at 4 minutes and 40 seconds.
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06192019, 09:57 AM  #4 
Officer
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Good deal Pisces what you say makes perfect sense in hindsight. I will correct in my next couple videos using a smaller AOB. Thanks for pointing that out!
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06192019, 10:08 AM  #5 
Silent Hunter

My trick for calculating range with the attackdisk backside:
1: lookup mastheight in meters in the recognition manual 2: measure centiradians in the periscope view. Try to gauge it down to a 6th centiradian. Remember which zoom level you use. 3: locate the mark on the inside scale of the (light yellow) distance disk which best represents the mastheight (28m, so 2800 in your example) 4: Locate the centiradian value as a minutemark on the timedisk. The centiradian fraction is then equivalent to a multiple of the 10 second intermediate marks. 2.7 is just over 2+4/6, so also just over 2m40s. 5a: For low zoom, look over at the distance value against 10 minutes (this is equivalent to 1 minute): 28m/(2.666 centiradians)= 10.5 (hundred meters) 5b: For high zoom, look over at the distance value against 4 minutes (4 times the 1 minute mark): 28m / 2.666 *4 = 42 hundred meters. By using centiradians as minutes on the time disk you get to see the distances for both zoom levels all at once. Much quicker than guesstimating and approximating with the ingame distance table. [EDIT]: And for centiradians below 2 you look to the beige/tan disk showing down into the minute and seconds. All second marks line up with the multiples of 10 seconds on the white minute scale.
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06192019, 10:22 AM  #6 
Officer
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That’s also very helpful! I’ll add rangefinding to the videos as well using this. I hadn’t thought of converting denominator values to the minutes scale on the time scale but makes perfect sense for more precision!
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06192019, 12:19 PM  #7 
Silent Hunter

And while I'm at it:
Calculating turn radius for (submerged) deadreckoning: 1: Line up the Odometer distance moved during the turn on the distance scale (light yellow disk inside scale), with turn degrees in seconds on the time disk. (360 degrees is 6 minutes) 2: Locate the 'Magic value' 180/pi on timedisk at 9m33s. 3: Read turn radius on the distance disk across the 'magic value' (180/pi) at 9m33s. Example: Odometer distance: 250m Turn angle: 43 degrees Align 250(.0)meters to 43s (or 7m10s). Read radius as 333(.1) meters against magic value 9m33s  Calculate chord distance (to locate end of turn with shortcut line) (Or in laymen's terms: The straight line across pizzaslice crust corners) Note: This calculation assumes a inside turn, i.e. the shortest corner. If taking an outside turn (the turn is larger than 180 degrees) then use the complement of it instead: 360  turn angle. Example: turn =215 degrees; use 145 as turn angle and 72.5 degrees as halve of the turn in step 2. 1: Align calculated turn radius to 90 degrees (index on the dark brown disk). 2: Locate the halve turn angle on the brown disk angle scale 3: Read the semichord length opposite to the halve turn angle. 4: Turn the semichord length mark to 30 degrees (that is a 'magic number' for 0.5) on the brown sineangle disk. 5: Read the actual chordlength opposite to 90 degrees. [EDIT] Example: Turn radius 333(.1) meter against 90 degrees Halve turn angle is 21.5 degrees Semichord length is opposite to 21.5 degrees at 122(.1) meter . Turn 122(.1) meter to 30 degrees Full chord length is 244(.2) meters opposite to 90 degrees. P.S. I don't see why people actually bother with calculating this chordlength. But it's is provided anyway to complete the toolset. I think it is much easier to draw a line perpendicular to own course at the start of the turn towards the center of the turn. Make it's length the turn radius. Then draw another line (or circle) from there to the angle of the end of the turn (length as radius). And start the new owncourse track from that endpoint.
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06192019, 12:58 PM  #8 
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Pisces you are on a roll! Great stuff  I’ll need to practice this last part before putting it in a video as I only just learned how to plot underwater myself.
You can rest assured that I will give you full credit in there for correction/additions! One question on the alternative method at the end to using a chord line. When you plot the second line at the end of the first perpendicular line, is that second line drawn using the newly established course? And is the length the same as the first, I.e. also equal to turn radius?
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06192019, 01:09 PM  #9 
The Old Man
Join Date: Apr 2005
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Why are the buttons on the bottom bar of your solution solver program off kilter?
My only guess is a DPI scaling issue. Do you use DPI scaling for your desktop? If so try right clicking the program, going to compatibility, and then clicking "Change High DPI settings" and turning it off for the solution solver program. Also, why would you not report that? 
06192019, 01:35 PM  #10  
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Quote:
Great tool by the way.
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06192019, 01:50 PM  #11  
Silent Hunter

Quote:
Old course track. Point of start of turn. Perpendicular line as radius of turn circle to the turn center. From turn center a line outwards to the end of the turn, rotated relative from the start of the turn by the turn angle. From end of turn radius a line perpendicular to it as the new course. This turn circle plot leaves a bit room for error with nonconstant rudder deflections and turn rates, or speed changes in the turn. But should work well enough for government work. Though I must say, still not done this in a multiplayer session with other crew. I perish the thought of a captain that cannot make up his/her mind as to what course to hold.
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06192019, 02:06 PM  #12  
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Quote:
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06192019, 11:51 PM  #13 
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Post 2 edited to add Part IV videos!
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