Slide Rule Targeting for SHIII/SHIV

[Puster Bill]

Originally Posted by sluissa

ah, that's exactly what I was doing wrong, thank you, I've got it figured out now... now to use my new found skills on some enemy subs

Glad to hear it!

It isn't really an intuitive process until you learn the why's and wherefore's of slide rules, but once you understand how they work you can do it pretty quickly.

[Puster Bill]

Originally Posted by stuntcow

Thanks for the info. I have gone insearch of one that I had. It used to be my grand fathers' and would be great to be able to use it. Thanks.

Glad to help.

[jmr]

Well I'm feeling a bit more comfortable practicing your example in this thread but over in this thread you gave a different example where the difference in bearing checks was only 7 degrees. I'm having a bit of trouble duplicating your results for that problem.

For example, in the problem listed in this thread where the bearing difference is 20 degrees, I start by moving the hairline to 4 on D scale, slide the 20 mark on S until it's on top of 4 on D, count how many degrees I have between 4 and 7 on D scale which comes out to 17 degrees on the S scale - I'm off by 3 degrees. So move the hairline back to 4 on D and move the S scale 3 degrees which gives me 23 degrees on 4 and 43 degrees on 7. I now have 20 degrees between 4 and 7 and like you indicated I now have the AOB for those two bearing marks.

I'm just having trouble replicating those steps above to match up 7 degrees between the two bearing marks.

[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...

[XLjedi]

Originally Posted by don1reed

One of these days, I'm hoping, one of these computer whiz-kids emulates a Bearing Rate Computer (whiz-wheel), that would really be nice.

Cheers

Being 37, I don't qualify as a "whiz-kid" but I know how to program tools that emulate whiz-wheels. What did you have in mind?

What exactly is a bearing rate computer?

[don1reed]

Howdy Arron.

Check this out: See Geosub1978's post above :

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

The whole chapter is about Bearing Rate Slide Rule (BRSR) see page 25 of the document.

It's basically a more modern version of the "Submarine Attack Course Finder/Is-Was" sliderule. (Do a search for thread).

These sliderules have a hole in the center through which a cord was passed and looped and the user wore around his neck, i.e., control room/ target acquisition.

btw: waiting patiently for your Moboard...best of luck.

Don

[XLjedi]

Originally Posted by don1reed

Howdy Arron.

Check this out: See Geosub1978's post above :

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

The whole chapter is about Bearing Rate Slide Rule (BRSR) see page 25 of the document.

It's basically a more modern version of the "Submarine Attack Course Finder/Is-Was" sliderule. (Do a search for thread).

These sliderules have a hole in the center through which a cord was passed and looped and the user wore around his neck, i.e., control room/ target acquisition.

btw: waiting patiently for your Moboard...best of luck.

Don

Ahhh... I see... so it's used in TMA to assist with speed and heading. :hmm:

Interesting, I'll have to read up a bit to figure out how it works. Or do you have like a 5 second example of what you're s'posed to do with it?

The time bearing curve was also an interesting plot... I'm gonna have to printout that doc and read it all the way thru. Thanks.

[don1reed]

I found the thread I was looking for...

See Post #60 by Hitman

http://www.subsim.com/radioroom/show...=106923&page=3

Thats what a "Submarine Attack Course Finder" (back side of the "IS-WAS") looks like. The Bearing Rate Computer, I believe, is a refinded version. Both were used extensively during WWII and into the Cold War years.