Slide Rule Targeting for SHIII/SHIV

[jmr]

Is the C2 doing 4 knots? I enabled auto targeting just for testing purposes and it reported the C2's speed at 2 knts. I think the ships in the torpedo academy mission will pick up speed and start zig zagging if they spot you or your torpedoes wake. Maybe that's what happened?

[ronbrewer]

Thanks. This is definitely a procedure worthy of either a sticky in the forum or included in an FAQ for the game. Really good work putting it all together.

One other thing that I wasn't sure about was the reason the second observation was reported in yards (4000 yards) when the first observation was done without a units descriptor (7000). I'm going to use this with SH3 when the slide rule arrives that I got off of eBay. Can the yards reference on the second observation be ignored when using a U-boat or will that change things later on in the procedure?

Thanks,
Ron

[Puster Bill]

Originally Posted by jmr

Is the C2 doing 4 knots? I enabled auto targeting just for testing purposes and it reported the C2's speed at 2 knts. I think the ships in the torpedo academy mission will pick up speed and start zig zagging if they spot you or your torpedoes wake. Maybe that's what happened?

I think the problem might have been that I misjudged one or both of the ranges, and by a happy coincidence also miscalculated the speed. So a mistake cancelled out a mistake.

Story of my life...

[Puster Bill]

Originally Posted by ronbrewer

Thanks. This is definitely a procedure worthy of either a sticky in the forum or included in an FAQ for the game. Really good work putting it all together.

One other thing that I wasn't sure about was the reason the second observation was reported in yards (4000 yards) when the first observation was done without a units descriptor (7000). I'm going to use this with SH3 when the slide rule arrives that I got off of eBay. Can the yards reference on the second observation be ignored when using a U-boat or will that change things later on in the procedure?

Thanks,
Ron

Well, pretend it doesn't say yards.

The only place it makes a difference is when you go to calculate the speed. For yards you use 5.6, for meters 5.15.

[ronbrewer]

Thanks, will do!!

Ron

[Puster Bill]

Originally Posted by don1reed

A pic is worth 1000 words:

The center of the maneuvering board (mobo) is the sub/uboat. Let every ring = 200m so that the outter ring is 2000m from the sub.



Math:

1852m / 3600s = .51 (constant). 1/.51 = 1.96 (constant)

When the answer is in meter per second we can either multiply by 1.96 or divide by .51 to get knots.

therefore,

2.3 mps / .51 = 4.5 knots.

A line drawn from m2 (target) to the sub, subtending from DRM (direction of relative movement) = AoB 112°. 180° - 112° = 68° for sliderule use.

Mobo is handmade 1 cm rings total 10 rings.

Another way to test the speed of your known C2 is to clock the movement of the ship as it passes the center stationary reticule of the scope. End the timing when the stern passes.

Math: Known Length of ship in meters / time in seconds X 1.96 = ship speed in knots.

more math:

Imperial: 2026 yds. / 3600 s = .56 (constant). 1/.56 = 1.78 (constant). Either divide yds. per second by .56 or multiply by 1.78 to get speed in knots.

@Bill: Your initial instructions on p1 are in order.

OK, I went back to training again.

Here is what I got this time for that ship:

1693 meters, 350 degrees
1796 meters, 359 degrees, 150 seconds.

That gives me an AOB on the second observation of 115 degrees.

Distance target traveled is 293 meters, speed 1.9 m/s = 3.7 knots.

Plugged into TDC, resulted in a hit just a bit forward of the aiming point.

For the second shot, this is what happened:

1881 meters, 10 degrees
2043 meters, 12 degrees 195 seconds.
AOB on second observation is 157 degrees (180 - 23 degrees)
Distance traveled 350, target speed 3.5 knots per the 3:15 rule.

Missed with 2 torps.

But I am getting the hang of it now...

[micky1up]

the first one you showed is still used today its called a 1936 bearing rate calculator used in conjunction withthe RBROTSARC ive mentioned before to get to a hard solution sometime better than the muti million pound computers can do

[don1reed]

@Bill:



I've placed your observations onto a moboard.

As you can see, I've labeled your sightings M1 thru M4, and in the legend are listed ranges & bearings. Just using a moboard, a pair of dividers, and a mm scale, I've plotted the distances travelled between the sightings; between m1 & m2 = 293m; betw m2 & m3 = 380m; and, betw m3 & m4 160m. What makes using the moboard very easy with this solution is because the sub/Uboat is stationary.

Clearly, it is seen that the distance travelled between m3 & m4 is greatly reduced due to the hit it suffered during your first attack. It is slowing down.

What I'm not sure about, is when you began to time the target for the second attack (?)

If you began timing when the ship was at M3 and finished at M4, it computes to 160m made good in 195 seconds = 1.6 knots. Let me know...at any rate the ship's skipper has changed course and presented a very narrow target for you to hit.

[Puster Bill]

Originally Posted by don1reed

@Bill:



I've placed your observations onto a moboard.

As you can see, I've labeled your sightings M1 thru M4, and in the legend are listed ranges & bearings. Just using a moboard, a pair of dividers, and a mm scale, I've plotted the distances travelled between the sightings; between m1 & m2 = 293m; betw m2 & m3 = 380m; and, betw m3 & m4 160m. What makes using the moboard very easy with this solution is because the sub/Uboat is stationary.

Clearly, it is seen that the distance travelled between m3 & m4 is greatly reduced due to the hit it suffered during your first attack. It is slowing down.

What I'm not sure about, is when you began to time the target for the second attack (?)

If you began timing when the ship was at M3 and finished at M4, it computes to 160m made good in 195 seconds = 1.6 knots. Let me know...at any rate the ship's skipper has changed course and presented a very narrow target for you to hit.

OK this is the point where the musician blames his instrument. In all honesty though, I did find that when I printed out my circular rule on cardstock it comes out slightly distorted when compared to regular paper, which means the cursor doesn't always match up correctly. 6 times 2 isn't supposed to equal 12.04! I'm going to glue the paper to cardstock for my next incarnation. Failing that, I do have a Pickett N200-ES on the way.

I actually do have a MoBo printed out and laminated so I can use wet or dry erase whiteboard markers. It just isn't always convenient for me to plot things out on it, if you get my drift...

[geosub1978]

Try the following

a. http://www.globalsecurity.org/milita...14308_ch10.pdf

b. http://hnsa.org/doc/attack/

You will find everything you need concerning the approach and attach fase, the Bearing Rate Computer (BRC) and the Is-Was wheel.

I have also a table of the fire bearing, according to firing coarse - target speed for 45 and 30 knots torpedoes for everyone interested in!

I would strongly recommend the stri-plot procedure as a SH3-4 mode. Unfortunatelly I am not able to do it...

[Puster Bill]

OK, I re-did the original problem using my corrected circular slide rule, the Sterling slide rule, and the flip-side of the "SUBMARINE ATTACK COURSE FINDER MK.1 MOD.3", AKA the infamous 'IS-WAS' (graciously provided by Hitman. See this thread:
http://www.subsim.com/radioroom/show...=106923&page=4 )

All are in agreement to within a certain margin of error. I got 26.1 knots on the circular, 25.8 knots on the Sterling, and 26.5 knots on the 'IS-WAS'.

I do have to say that using the 'IS-WAS' makes the job faster and more intuitive than either the circular or the Sterling.

Great job Hitman!

[Spin Doctor]

Lots of good hard to find information here. Should probably be a sticky, hmm?

[Puster Bill]

Originally Posted by Spin Doctor

Lots of good hard to find information here. Should probably be a sticky, hmm?

Fine with me, as long as I have enough time to edit the stuff I got wrong

[Puster Bill]

OK, I got a new slide rule with a standard 'S' scale (a Pickett N200-ES). I'm thinking about re-doing the whole set of instructions, with better pictures and to make it more of a 'step by step' instruction set. I'm also thinking about adding instructions for accounting for the motion of your own boat.

Any interest?

[jmr]

Heck yeah go for it!

I'm still learning the ins and outs of my new rule from various manuals I downloaded and I'm simply stunned at what this thing can do.