Slide Rule Targeting for SHIII/SHIV

[Puster Bill]

Slide Rule Targeting

For Silent Hunter III / IV



Did you ever want to increase your game immersion, and your accuracy, without using modern technology? I certainly did when I got the GWX upgrade for SHIII. I had been using this wheel for targeting:



http://img164.imageshack.us/img164/113/image001zs5.jpg


It worked well enough, but it took me ‘out of the game’ because it looks like it was printed on an old dot matrix printer.

After trying to make a couple of slide rules (and succeeding, somewhat), I decide to just go ahead and buy one. I checked some local antique shops until I found this:

http://img78.imageshack.us/img78/3018/image002ku2.jpg

A Sterling “Precision” slide rule. I put the word precision in quotes because Sterling has just about the worst reputation for accuracy. However, that doesn’t really matter for the job we have to do, and I was able to get it for $5. A good condition, more accurate, and more authentic slide rule would have cost a lot more. No matter whether you buy one or make one, it has to have the C, D, and S scales on it. It would also help if it has the A and B scales (just about every rule does). Any rule that has the word ‘trig’ in the name will work fine.

Anyway, down to the business of sinking ships…

In order to get the information that you need, you will have to make two observations. Let us call them A and B. We need to know the distance to the target and the bearing for both observations, and the time between those observations.

Let us suppose that the distance for our first observation is 7000 (don’t worry about whether it is meters or yards yet), on a bearing of 65 degrees. Start the stopwatch, lower your scope, and go get a cup of coffee, take a leak, apologize to your wife, or whatever. Let’s just say you missed the opportunity to use the 3 Minute and 15 Second rule to get target speed, so your next observation, B, occurs at 4 minutes. When you take the B observation you get 4000 yards at a bearing of 45 degrees.

I write this stuff down on paper, and this is what it would look like:

O RNGE BRG AOB TIME (seconds)
A 7000 065 ??? 0
B 4000 045 ??? 240

You now have everything you need to determine AOB and speed of the target. We whip out our handy-dandy slipstick, and note that there are 20 degrees between 65 degrees and 45 degrees. I move the slide until there is 20 degrees difference on the S between the 4 and the 7 on the A scale. I have to use the A scale on this particular rule, as it has a ‘double length’ S scale that goes from about 45’ to 90 degrees. Most rules have a regular S scale that goes from a little under 6 degrees to 90 degrees, and an ST scale to handle the smaller numbers. If your slide rule has a 'regular' S scale, you have to use the D scale instead of the A scale.

You will note here that it works out that when 23 degrees on the S scale is under the 4 (for 4000) on the A scale;

http://img133.imageshack.us/img133/3743/image003zh8.jpg

That 43 degrees on the S scale falls directly underneath the 7 (for 7000) on the A scale:




http://img133.imageshack.us/img133/2359/image004sa8.jpg



We now have our two AOB observations. Strangely enough, the AOB for observation A is actually under the distance for observation B, and vice versa. We then fill the information in on our paper:

O RNGE BRG AOB TIME (seconds)
A 7000 065 023 0
B 4000 045 043 240

If you are pretty good at guessing the AOB, align your guess of the AOB from observation B on the S scale with the distance from observation A on the A (or D) scale. That should save you some time fiddling around, as you are close to where it should be.

Now that we have the range and AOB, we have to figure the target speed to input it into the Vorhaltrechner/TDC, as the case may be. As a side note, I usually pause the game right after the second observation so that I can make the calculations. On a real submarine, the captain wouldn’t be making the calculations, so I am in effect doing two jobs! You don’t have to, though. If you leave the periscope at the heading of the last observation, you will be able to enter all the information, then swing the ‘scope back on target, with the information all updated by the TDC.

To calculate the target speed in units per second, we need to find the distance the target has traveled between observation A and observation B. Without moving the slide, we move the cursor of the slide rule down the S scale until it is right above the difference in degrees between the bearings of observation A and observation B. For this example, that is 20 degrees. We read the speed off of the A scale (or D scale, if you have a ‘normal’ S scale). In our case, it reads 3.5, which we know will be 3500 units (either meters or yards):




http://img259.imageshack.us/img259/6743/image005zr5.jpg



We now have to find out how fast that is in units per second. On this particular rule, I have to flip the slide over the get the B and C scales:




http://img339.imageshack.us/img339/6380/image006xh8.jpg




The following section has been changed on edit from the original to correct an egregious error. Thanks to don1reed for pointing it out!


To find the target speed, we have to align the 2.4 (for 240 seconds) on the B or C scale with 3.5 (for 3500) on the A or D scale. It should look like this if you are using the C + D scales:

http://img250.imageshack.us/img250/4957/picture022mt4.jpg



We then read the speed in units per second on the D scale right underneath the index mark of the C scale, in this case 14.6 units per second:

http://img260.imageshack.us/img260/7128/picture023jz0.jpg




Now, to find the target speed in knots we have to know whether our distance unit is a yard or a meter. If the distance measurement is in yards, you have to align 5.6 on the C scale with the speed in yards per second, or 14.6, on the D scale:
http://img409.imageshack.us/img409/5182/picture024nc0.jpg

We then read the speed in knots on the D scale directly below the index on the C scale, in this case just about 26 knots:

http://img341.imageshack.us/img341/9196/picture025fh5.jpg



The calculation is the same if your base unit is meters, except that instead of using 5.6, you use 5.15. In our little exercise, that would give you a target speed of 28.2 knots.


You can now plug the distance, bearing, AOB, and speed into the TDC in manual mode. Don’t forget to switch it back to Auto!


Happy Hunting,

Puster Bill

[Platapus]

After trying to make a couple of slide rules (and succeeding, somewhat), I decide to just go ahead and buy one. I checked some local antique shops until I found this:

Sliderules in antique stores!!! <sad>

Might just as well bury me now or put me on an ice flow.

Anyway for us dinosaurs that STILL OWN a sliderule. Thanks very much for these instructions.

Antique stores indeed Haruumph!

[ronbrewer]

Thanks for the excellent instructions. I have a question about the two observations. Does the sub have to be at a stop or can you creep along at around 2-3 knots in between the two measurements? I'm just curious if I need to be on the surface or can remain at periscope depth (which would require some form of movement to maintain depth).

Thanks,
Ron

[greekfire]

interesting post. If I could pull myself off this freakin computer, I'd go out and look for one. meh....checking ebay.







btw...I luv your font size. it fits perfect on 48,0681 x 32,253 resolution. :)

[Puster Bill]

Thanks for the excellent instructions. I have a question about the two observations. Does the sub have to be at a stop or can you creep along at around 2-3 knots in between the two measurements? I'm just curious if I need to be on the surface or can remain at periscope depth (which would require some form of movement to maintain depth).

Thanks,
Ron

I find that if you are creeping at steerage, ie. 1 to 2 knots, it doesn't introduce enough error to matter as long as you aren't taking very long shots.

If you were going faster than that, it would introduce more error.

[Puster Bill]

interesting post. If I could pull myself off this freakin computer, I'd go out and look for one. meh....checking ebay.







btw...I luv your font size. it fits perfect on 48,0681 x 32,253 resolution. :)


Well, as for the font size, well, I wanted it to be easily readable.

If you can't find a slide rule locally or on Ebay, you could always make your own from the templates available here:

http://www.sphere.bc.ca/test/build.html

I built the Yokota Log-Log rule at that site, and it works well for this. Don't build the first one (unless you want to just for fun), because it lacks the S scale.

There are also some nifty Java slide rule simulation pages here:

http://www.antiquark.com/sliderule/sim/index.html

[jmr]

Slide rules and whiz wheels rule! Here's some I made from various posts on these forums.

Kin Ronoff's Range Calculator Mark 3B and Course Calculator Mark4B

http://img89.imageshack.us/img89/4351/krcourseandrangevg4.th.jpg (http://img89.imageshack.us/my.php?image=krcourseandrangevg4.jpg)

Target course calculator and nasmith director

http://img101.imageshack.us/img101/4752/targetcoursecalculatorahc6.th.jpg (http://img101.imageshack.us/my.php?image=targetcoursecalculatorahc6.jpg)

Banjo

http://img341.imageshack.us/img341/2856/banjofo0.th.jpg (http://img341.imageshack.us/my.php?image=banjofo0.jpg)

[Puster Bill]

Sliderules in antique stores!!! <sad>

Might just as well bury me now or put me on an ice flow.

Anyway for us dinosaurs that STILL OWN a sliderule. Thanks very much for these instructions.

Antique stores indeed Haruumph!

I remember playing around with one when I was a kid, right when electronic calculators became cheap enough to replace them. I ended up busting it. What did I know?

As soon as I can, I'm going to pick up a couple of Picketts. I want an N600T or N600-ES, and either an N500-(T or ES) or a N1010-(T or ES).

[sqk7744]

Great Post Puster Bill!

Cheers :arrgh!:

Here's my tutorial for the Banjo:
http://www.subsim.com/radioroom/showthread.php?t=108931&page=2

[Puster Bill]

Target course calculator and nasmith director

http://img101.imageshack.us/img101/4752/targetcoursecalculatorahc6.th.jpg (http://img101.imageshack.us/my.php?image=targetcoursecalculatorahc6.jpg)



I adapted the instructions for that wheel (first picture in my post) to a linear slide rule. I did find that he uses 5.70 for converting from Yards per Second to Knots, which is incorrect. It's actually about 5.64, which I round down to 5.6.

[greekfire]

Well, as for the font size, well, I wanted it to be easily readable.

If you can't find a slide rule locally or on Ebay, you could always make your own from the templates available here:

http://www.sphere.bc.ca/test/build.html

I built the Yokota Log-Log rule at that site, and it works well for this. Don't build the first one (unless you want to just for fun), because it lacks the S scale.

There are also some nifty Java slide rule simulation pages here:

http://www.antiquark.com/sliderule/sim/index.html

Hey, I appreciate you posting these links. I'm checking them out as soon as I get done typing this. Always excited about trying out alternative tools and methods for plotting. Too fun. Thanks again. lol about font. :)

EDIT: That sphere website sells them. I'm gonna buy one but I need you to tell me which kind is best. From your posts, I assume an A/B scale with S?

[jmr]

I adapted the instructions for that wheel (first picture in my post) to a linear slide rule. I did find that he uses 5.70 for converting from Yards per Second to Knots, which is incorrect. It's actually about 5.64, which I round down to 5.6.

Yeah the graduations are a bit sloppy as well which is why I hardly used that wheel. I'm going to have to shopping around my area antique stores for a slide rule. I made my own from this (http://www.sphere.bc.ca/test/build.html) page but I'd like to have the real deal and not a laminated card stock one ;)

[Puster Bill]

Hey, I appreciate you posting these links. I'm checking them out as soon as I get done typing this. Always excited about trying out alternative tools and methods for plotting. Too fun. Thanks again. lol about font. :)

EDIT: That sphere website sells them. I'm gonna buy one but I need you to tell me which kind is best. From your posts, I assume an A/B scale with S?

Actually, all you really need is the C+D scales, and the S scale, although just about every slide rule has an A+B scale (except for circular ones, they don't need it because the scales are 'wrapped around').

I checked out the sphere site, and they do indeed sell them, but you could probably pick one up cheaper on Ebay.

If you want to go even cheaper, call around to your local antique stores (sorry Platapus!). Or just ask some of the people who are older than 45 or 50. They might have one sitting around and will give it to you. My father has a circular one that he's currently trying to find for me, and a guy I work with was going to give me his, but he couldn't find it (he thinks he lost it in a move).

If you want to build one, try the circular rule at the sphere site. It has to be the first circular one, because that is the only one with an S scale. Print it out on cardstock and laminate it. Print out the cursor on an inkjet transparency (10 sheets for about $7 at Wal*Mart), then just pin them together.

[Puster Bill]

Yeah the graduations are a bit sloppy as well which is why I hardly used that wheel. I'm going to have to shopping around my area antique stores for a slide rule. I made my own from this (http://www.sphere.bc.ca/test/build.html) page but I'd like to have the real deal and not a laminated card stock one ;)

Yep. That's why I went looking for one.

Although, I think I am going to have my father build a wooden, brass, or acrylic base for that Yokota Log-Log rule. He's handier at that kind of stuff than I am.

I built one out of cardboard, and I love it, I just want a sturdier one.

Damn, this slide rule thing can be addictive!

[Jace11]

A slide rule in game map tool would be rather useful methinks...

[Puster Bill]

OK, I built the circular slide rule at the sphere site. Here is the whole thing:

http://img260.imageshack.us/img260/7805/picture017ds3.jpg

And here is a close-up:
http://img247.imageshack.us/img247/8894/picture019ft4.jpg

One piece of advice: If I were going to do it again, I would take a highlighter and highlight the S scale before I laminated it. As it is, it kind of gets lost in the other scales.

[don1reed]

Good job, Bill. It's good to see you youngsters keeping the math traditions alive. :up:

I built that circular sliderule from "Sphere" also. I highly recommend it, especially for those who get confused when obligated to move the slide on a 10" model due to answers appearing off scale--less cursor movement.

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

[Dustyboats]

If anyone would like a FLAT Slide Rule (As apposed to the circular one in the diagrams) I am quite happy to post it to you....free of any charges.Its still in its blue case!
Contact me via PM...first come first served....Dusty

[jmr]

Welp my trek to the local antique shops paid off. I managed to grab a Picket Model 14 US which is in great shape along with a a circular slide rule from a military antique store.

Now I have to figure out how to use them :}

http://img223.imageshack.us/img223/7541/cimg1226qz4.th.jpg (http://img223.imageshack.us/my.php?image=cimg1226qz4.jpg)

[don1reed]

Great find, jmr.

goto: http://www.sphere.bc.ca/test/build.html

they have tons of DL-able instructions.

[Puster Bill]

Great find, jmr.

goto: http://www.sphere.bc.ca/test/build.html

they have tons of DL-able instructions.

Yep. If you can't find it there, try the International Slide Rule museum at http://www.sliderulemuseum.com/.

They have a bunch of scans of the original manuals.

[Hitman]

I have figured out how the rear side of the 1943 wiz-wheel for submarines whose pics posted Kaptain Krunch long ago (http://www.subsim.com/radioroom/showthread.php?t=106923) does work:D and I have started to creating it with Paint Shop Pro :D If I get a decent finish, I will upload it so everyone can print and put in the rear side of their banjo. It is a superb tool and completely thought for the use that is of interest to all of us: Sinking vessels!

Wiz rulers rule:rock:

[Puster Bill]

I have figured out how the rear side of the 1943 wiz-wheel for submarines whose pics posted Kaptain Krunch long ago (http://www.subsim.com/radioroom/showthread.php?t=106923) does work:D and I have started to creating it with Paint Shop Pro :D If I get a decent finish, I will upload it so everyone can print and put in the rear side of their banjo. It is a superb tool and completely thought for the use that is of interest to all of us: Sinking vessels!

Wiz rulers rule:rock:

That would be *MUCH* appreciated. I'm going to make a banjo/is-was soon. I don't have SHIV yet (I started this thread in SHIV because there are more 'eyes' here then in the SHIII forum, but I put a link to this thread in there).

I guess I'll just have to assume that my American cousin, who happens to be a submarine commander in the US Navy, sent me one to use before December 11th, 1941 :D

[froschman]

For a veteran as me, it was very interesting to see how to use a slide rule in this game. I have at least two slide rules from my eary days at a technical university, lying around unused. I will study your method.

For those who want to test it, before trying to buy one, there is a java applet simulating a decent slide rule at:

http://www.taswegian.com/TwoHeaded/UniVirtual/UniVirtual.html

Good hunting!

[Puster Bill]

For a veteran as me, it was very interesting to see how to use a slide rule in this game. I have at least two slide rules from my eary days at a technical university, lying around unused. I will study your method.

For those who want to test it, before trying to buy one, there is a java applet simulating a decent slide rule at:

http://www.taswegian.com/TwoHeaded/UniVirtual/UniVirtual.html

Good hunting!

Cool. Here is a site with 7 different virtual slide rules (various Pickett models):

http://www.antiquark.com/sliderule/sim/

They are a decent option to use in the game if you don't have a real slide rule.

Seriously, it would be cool if someone would make a virtual one for use in either the map screen, or especially the TDC screen.

[Hitman]

Seriously, it would be cool if someone would make a virtual one for use in either the map screen, or especially the TDC screen.

Redwine already did ot in SH2:D But was unable or had no longer time to do it for SH3:-? . Anyway, a real one in your hands is sooooooooo cool!!!:rock:

That would be *MUCH* appreciated

Don't worry, I will try my best. I'm the first one interested in having it:yep:

[Puster Bill]

Anyway, a real one in your hands is sooooooooo cool!!!

True dat.:up:

[sluissa]

either I'm doing something wrong or my slide rule is wrong or something, but near the end when you're calculating speed, no matter how I work it, when I put 1 with 3.5,
2.4 =/= 6.85 it's about 8.43 on mine.

everything else seems to work out pretty well with an error or less than 1(usually less than .1), but on that particular problem, I can't seem to get it to work

[Puster Bill]

either I'm doing something wrong or my slide rule is wrong or something, but near the end when you're calculating speed, no matter how I work it, when I put 1 with 3.5,
2.4 =/= 6.85 it's about 8.43 on mine.

everything else seems to work out pretty well with an error or less than 1(usually less than .1), but on that particular problem, I can't seem to get it to work

I think I know what is going on.

If you are working with the C + D scales, you have to move the slide (which has the C scale on it) so that the right-most index mark (the '1' on the right) on the C scale is over 3.5 on the D scale. Then move the cursor to the 2.4 mark on the D scale, and read the speed (6.85 units per second) on the C scale.

If you are using the A + B scales (which I prefer for this), put the 3.5 on the B scale underneath the middle index mark (the '1') on the A scale. slide the cursor to 2.4 on the B scale, and read the speed on the A scale.

I suspect you put the 3.5 on the B scale under the middle index of the A scale, then slid the cursor to 2.4 on the A scale, which will read 8.4 on the B scale.

[Puster Bill]

OK, I re-made my circular slide rule from the sphere site, and put the 'banjo/is-was' on the back of it. I also highlighted the S scale on the circular rule so that it is instantly recognizeable (it's the yellow band below):

http://img107.imageshack.us/img107/9923/picture020yq9.jpg


And this is the Attack Course Finder side:

http://img454.imageshack.us/img454/5909/picture021ds0.jpg

I trimmed it to fit on the backside of the slide rule.

By the way, excuse the crappy pictures. Regular camera is broken, so I have to use the webcam to take them. :damn:

An interesting experiment would be to mount them both on a board next to each other. Since I have to tote this thing with my laptop, I don't really have that luxury

[jmr]

Wow very nice! Is that card stock you're using there? Your cut circles look damn near perfect to me! Did you use regular old scissors?

As an aside, having never used a slide rule before and not being the most mathematically adept person out there, I was up until 2am scoping out the web for a user friendly guide on slide rule operations. I came across this (http://www-cse.ucsd.edu/%7Epasquale/Classes/SlideRule/) site at UC San Diego where a professor holds a seminar on slide rule operations. How about that! He has a 13 MB .pdf file of his PowerPoint presentation here (http://www-cse.ucsd.edu/users/pasquale/SlideRuleTalk-MIT.pdf) Good stuff for beginners.

[Vandecker]

What is meant by 20 degrees between the 4 and the 7??

I have a proper engineering slide rule infront of me (my fathers from years back), and no matter how I move it so that the slide moves 20 degrees acording to the S table I get results that are at least a degree if not more different to yours. i.e 22 degrees at 7000 metres and 41 degrees at 4000 metres.

How do you calculate that 20 degrees onto the slide rule??

[jmr]

My brain is fried. Maybe it's because I don't remember my trig from YEARS ago or that I just suck at math but I'm getting inconsistent results with my rule. I need an idiot's guide to these things.

[Puster Bill]

Wow very nice! Is that card stock you're using there? Your cut circles look damn near perfect to me! Did you use regular old scissors?

As an aside, having never used a slide rule before and not being the most mathematically adept person out there, I was up until 2am scoping out the web for a user friendly guide on slide rule operations. I came across this (http://www-cse.ucsd.edu/%7Epasquale/Classes/SlideRule/) site at UC San Diego where a professor holds a seminar on slide rule operations. How about that! He has a 13 MB .pdf file of his PowerPoint presentation here (http://www-cse.ucsd.edu/users/pasquale/SlideRuleTalk-MIT.pdf) Good stuff for beginners.

Yep, it's cardstock. I use it for making my own QSL cards. Every layer is laminated, including the transparencies. That makes it more rigid, and it protects the print.

As for the cuts, yes, I use regular old scissors. I just cut right along the lines, and I take my time. For the actual circular slide rule, I got my compass from high school and drew a circle on the back of the cardstock that had the slide rule printed on it, centered on the pivot, that I pre-punched. Then I just cut along the line...

I did it while my 3 year old son was in for a nap. Took about 45 minutes total, being careful, but I already had the cursors from a previous incarnation of the slide rule, so that saved me some time.

I'll have to check those links out, sounds cool. :up:

[Puster Bill]

What is meant by 20 degrees between the 4 and the 7??

I have a proper engineering slide rule infront of me (my fathers from years back), and no matter how I move it so that the slide moves 20 degrees acording to the S table I get results that are at least a degree if not more different to yours. i.e 22 degrees at 7000 metres and 41 degrees at 4000 metres.

How do you calculate that 20 degrees onto the slide rule??
I'd have to see it to know for sure, but I have three rules, two I made and one that was manufactured, and they are all in agreement (within a certain amount).

When I align 23 degrees on the S scale to the second 4 on my A scale, then 43 degrees on the S scale lies directly below the 7 on the A scale.

You might have to use the D (or C) scale with the S scale on your rule, as I noted in my instructions the rule I was using has an S scale that is "double", ie., it goes from just under 40 minutes all the way up to 90 degrees, so I *HAVE* to use the A scale.

If you have a normal S scale that goes from just under 6 degrees up to 80 or 90 degrees, you can't match it against the A or B scale, you have to match it against the C or D scale.

Hope that helps.

EDIT: If you have a normal S scale and the target is coming close to right at you or moving almost directly away, you might have to use the ST scale, which would go from less than one degree up to about 5.5 degrees, give or take, against the C or D scale.

[Puster Bill]

My brain is fried. Maybe it's because I don't remember my trig from YEARS ago or that I just suck at math but I'm getting inconsistent results with my rule. I need an idiot's guide to these things.

It just takes some practice. I fooled around with it for at least a week before I posted those instructions.

Trust me, I'm wearing a silly medic hat!

[Puster Bill]

Here is another nifty cardstock / lamination project:

Do a GIS for 'maneuvering board'. Print it out on cardstock, then laminate it.

You can then use a fine point erasable whiteboard marker to keep track of contacts, and to erase it just use a paper towel or toilet paper.

(I feel like Kapitanleutnent Martha Effin' Stewart today)

[Vandecker]

I still can't get it:dead:, my biggest problem is i still don't understand what you mean by 'twenty' degrees. Do you meant I have to move the slide rule two little ticks in one direction? none of which add up to twenty in value, or that I have to move the slide rule to a certain 'value' of twenty indicated by the slide.

This step is also not very well illustrated by your photo as from what I can see you have not moved the slide by 'twenty' by either the ticks or value:doh:.

I attempted to use this method trying both the value and the tick method but both gave me angles of bearing that were clearly too low i.e: 025 when the target was clearly well above an AOB of 045.

Thanks for Writing this article by the way, I've been hunting round trying to find such an article for a while now since I knew dad still had his old slide rule hanging around.:up:

[Puster Bill]

I still can't get it:dead:, my biggest problem is i still don't understand what you mean by 'twenty' degrees. Do you meant I have to move the slide rule two little ticks in one direction? none of which add up to twenty in value, or that I have to move the slide rule to a certain 'value' of twenty indicated by the slide.

This step is also not very well illustrated by your photo as from what I can see you have not moved the slide by 'twenty' by either the ticks or value:doh:.

I attempted to use this method trying both the value and the tick method but both gave me angles of bearing that were clearly too low i.e: 025 when the target was clearly well above an AOB of 045.

Thanks for Writing this article by the way, I've been hunting round trying to find such an article for a while now since I knew dad still had his old slide rule hanging around.:up:
OK, the difference between our first bearing of 65 degrees and our second bearing of 45 degrees is 20 degrees, right?

Now, at the beginning we don't know the target AOB with any certainty, but we have a 'guesstimate' from looking at the ship. So lets say that we 'guesstimated' that the AOB was 50 degrees when the target was at observation B (Distance 4000, relative bearing 45 degrees).

You would slide the S scale so that the 50 is underneath the distance of observation A, or in our example aligned with the 7 on the A or D scale as appropriate.

We then slide the cursor down 20 degrees on the S scale (which would put us on 30 degrees on the S scale). On the A or D scale, it reads 4.56, which isn't right. It should land on the distance to observation B, which is 4000 (4 on the slide rule).

That means our AOB estimate was off. So, we try an AOB of 45 degrees. Aligning that with the 7 (distance for OBS A), we find that 20 degrees less than 45, or 25, lands at right about 4.2, which is close to our expected 4.0 value.

So, we fiddle with the slide until we figure out that when 23 degrees is under the 4, 43 degrees is under the 7. That is our 20 degree difference.

Interestingly, the AOB for observation B, which we originally estimated to be 50 degrees, but it turned out to be 43 degrees, lies underneath the distance for observation A.

Also, note that the AOB changes from observation A to observation B by the same amount the bearing changes: 20 degrees.

Anyway, to get the distance the target traveled, we then slide the cursor down to the 20 degree mark on the S scale, and away you go from there.

Hopefully, that helps. Let me know if you need more.

[XanderF]

This thread makes me want this (http://cgi.ebay.com/So-Rare-Vintage-TESA-SA-MAXIMATIC-Slide-Rule-circular_W0QQitemZ130100480281QQihZ003QQcategoryZ3 61QQssPageNameZWDVWQQrdZ1QQcmdZViewItem).

Hmmm....now, how to convince the wife that a $100 slide rule is a needed component...

[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.

[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

:)

[Puster Bill]

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.

:up:

[Puster Bill]

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 (http://www.subsim.com/radioroom/showthread.php?t=111621) 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.

[Puster Bill]

Well I'm feeling a bit more comfortable practicing your example in this thread but over in this thread (http://www.subsim.com/radioroom/showthread.php?t=111621) 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.

I'll have to revisit it when I get a bit more time, perhaps tomorrow.

Although, I notice that I referenced using the A scale against the S scale, but if you have a 'normal' S scale it should go against the C or D scale.

Plus, that was kind of an off-the-cuff first stab at explaining it, so I could have some errors in there.

I'll take a look at it again in the next couple of days (real life unfortunately intrudes!).

By the way, I have been getting more accurate results from the circular rule at the sphere site doing some paper exercises that simulate what you would see in the game, vice using either of my linear rules. Plus, I put the banjo doohickey on the reverse. I still have to figure out how to use it. I don't know that it is necessary, though, because my method gives you an accurate AOB, and you can figure the base course of the target if necessary using the same principles.


Oh, and the *EXACT* conversion from meters per second to knots is 5.144, so 5.15 should be close enough.

The *EXACT* conversion from yards per second to knots is 5.6267, so 5.60 should be close enough.

[jmr]

I have that circular one printed out as well but how do you adjust the S scale since it's fixed on that wheel? Like how would you "fit" 20 degrees between 4 and 7 on A scale?

EDIT: *DOH* I just noticed you don't have to move anything on the S scale as it already gives you the correct value if you use the D scale for your 4 and 7 values (the range at the two bearing points. Is that right?

[starbird]

Yeah, C and D are the same scale. So using C and D you can multiply, using D and S (in your case) gives you the sine. There is no rule for where a scale is located. Some have S on the slide, some on the body. A few have it (and ST) on both the slide and body, so you can do trig and other arithmetic without having to reset your slide.

I picked up a Pickett 500 ES a few months ago, and its a blast to use.

[Puster Bill]

I'm just having trouble replicating those steps above to match up 7 degrees between the two bearing marks.
OK, I checked it on my Sterling, and on the circular, and they are in agreement. The angle under the 7300 mark (7.3) should be 38 degrees on the S scale, and the angle under the 6100 range should be 31 degrees.

Does that help?

I re-did the whole problem, and got a speed of 9.4 knots, which is close to my original result of 9.35 knots.

[jmr]

Wow I'm sucking at this.

Ok with the circular slide rule I set the first cursor on 6100 on D scale, then set the second movable cursor on 7300 also on D scale.

Following the cursor down from 6100 it intersects the S scale at 37.6 or we can just say 38. Following the other cursor down from 7300 it intersects the S scale at 47 degrees.

What am I doing wrong?

EDIT: Are you saying you should first have a guestimate of the target's AOB when trying to squeeze in the difference between the two bearing points? The scale is long and just taking a stab at finding X number of degrees between bearing points could take a long time. So by having a guess of the AOB that can give you a ballpark figure for narrowing down the S scale to get your required number of degrees?

[don1reed]

For those of you contemplating the $$$ purchase of an expensive relic...here's the best virtual slide-rule out there. Oh, I have a good collection of the real things; but this is for those who would like the feel of what the WWII skippers had to endure, without spending the big bucks/euros.

http://www.sliderule.demon.co.uk/

May I suggest D/L the newer version 2.1...version 2.0 is good too, btw.

I play SH3/4 in the Windows mode so I keep my virtual sliderule minimized along the bottom of my screen until needed.

...also, the virtual sliderule comes with complete instructions.

cheers,

[Puster Bill]

Wow I'm sucking at this.

Ok with the circular slide rule I set the first cursor on 6100 on D scale, then set the second movable cursor on 7300 also on D scale.

Following the cursor down from 6100 it intersects the S scale at 37.6 or we can just say 38. Following the other cursor down from 7300 it intersects the S scale at 47 degrees.

What am I doing wrong?

EDIT: Are you saying you should first have a guestimate of the target's AOB when trying to squeeze in the difference between the two bearing points? The scale is long and just taking a stab at finding X number of degrees between bearing points could take a long time. So by having a guess of the AOB that can give you a ballpark figure for narrowing down the S scale to get your required number of degrees?


Yes, a guesstimate of the AOB will get you there quicker.

One thing you have to remember: With the circular slide rule, ignore the cursor that is fixed to the transparent slide. You want to move the C scale so that the 7.3 (for 7300 yards is over the 38 degree mark on the S scale.

What I do is I put the moveable cursor (not the one fixed to the C, B, and K scales) over my estimate for the AOB at observation B, then move the C scale until the range for observation B is under the moveable cursor. Then I can move the moveable cursor (not the fixed one!) down 7 degrees on the S scale, and see where it lands. It should land very close to the 6.1 (for 6100) if you guesstimated an AOB of 38 degrees for observation B, then moved the cursor down to 31 degrees on the S scale.

One important rule for the circular rule, at least for this part: Ignore the fixed cursor!

If you are still having problems, I can post pictures of it this afternoon (when my 3 year old is in for a nap).

[Puster Bill]

By the way, here is another slide rule that has assembly instructions on the back of it:

http://www.sciam.com/media/pdf/Slide_rule.pdf

[jmr]

I think one more worked example would be nice. I'm the special student that needs extra help :lol::lol:

My next question is what do you do about an AOB larger than 90 degrees?

For example, I was messing around with the Torpedoes mission in the SHIII naval academy with the C2 freighter (which starts with an AOB of 110 starboard):

Bearing 1: 345 Range 1700m
Bearing 2: 000 Range 1770m

With a bearing difference of 15 degrees, how do you "fit" 15 degrees between 1700 - 1770?

[Puster Bill]

I think one more worked example would be nice. I'm the special student that needs extra help :lol::lol:

My next question is what do you do about an AOB larger than 90 degrees?

For example, I was messing around with the Torpedoes mission in the SHIII naval academy with the C2 freighter (which starts with an AOB of 110 starboard):

Bearing 1: 345 Range 1700m
Bearing 2: 000 Range 1770m

With a bearing difference of 15 degrees, how do you "fit" 15 degrees between 1700 - 1770?
Hey, we all need that extra bit of help sometimes.

In the case you cited, it isn't the bearings themselves that are important, but the difference between them.

We have to use our noggin here, and realize that we are describing a triangle. For the purposes of this computation, it doesn't really matter what direction the target is moving, so let us assume it is moving towards us instead of moving away from us.

Between 1.7 and 1.77 on the C scale of the circular, I can fit 15 degrees on the S scale from 73 degrees up to 88 degrees. We can't tell *EXACTLY* where it will fall on the rule because the S scale is all bunched up there, but we know it has to be about 15 degrees from 73.

We get the AOB's by then subtracting those numbers from 180 degrees to account for the fact that he is moving away from us. So, the AOB for OBS 1 would be 180 - 88 = 92 degrees and the AOB for OBS 2 would be 180 - 73 = 117 degrees.

we then slide the cursor to 15 degrees on the S scale, and read the distance off on the C scale, about 4.615. We know he didn't travel 4,615 meters, so it has to be 461.5 meters.

You didn't specify a time between OBS 1 and OBS 2, so I'll assume it was for 2 minutes, or 120 seconds. That gives us a speed of roughly 3.875 meters per second, which equals about 7.5 knots.

I did this on the circular, then checked it on the Sterling. The Sterling gives a slightly closer-to-calculator result, but the difference isn't enough to cause you to miss.

Honestly, I had to draw it out first on paper using a protractor and a ruler so that I understood the problem.:oops: That AOB you cited of 110 is off somewhere, it doesn't appear anywhere when I draw the triangle. Unless the ship was zig-zagging, in which case you have to take the BASE course, not the actual AOB. If the ship isn't moving in a straight line, the AOB information generated by this method won't be accurate.

In my defense, It's been a LOOOONNNNNNGGGGG time since I took trig, and this whole slide rule thing is almost as new to me as it is to you.

And truthfully, the proper answer is "Haul ahead of the bastard to you can get a good 90 degree shot at him" :arrgh!:

[jmr]

With regards to the problem I gave above, I had auto targeting on so I could verify my results and the 110stb AOB was what the auto TDC was telling me at the of that bearing. It's the torpedo academy mission where you begin facing north and if you move your scope left about 20 degrees you'll see the C2 freighter on a northeasterly heading at 2 knts.


Hey I appreciate you taking the time to help me with this! It's kind of wierd how this all turned out - a thread here and there on whiz wheels and suddenly I find myself with 5 homemade wheels plus 2 wheels purchased from an antique store. It's all deeply fascinating to me being someone who grew up with digital calculators and computers.

[Puster Bill]

With regards to the problem I gave above, I had auto targeting on so I could verify my results and the 110stb AOB was what the auto TDC was telling me at the of that bearing. It's the torpedo academy mission where you begin facing north and if you move your scope left about 20 degrees you'll see the C2 freighter on a northeasterly heading at 2 knts.


Hey I appreciate you taking the time to help me with this! It's kind of wierd how this all turned out - a thread here and there on whiz wheels and suddenly I find myself with 5 homemade wheels plus 2 wheels purchased from an antique store. It's all deeply fascinating to me being someone who grew up with digital calculators and computers.

Strange, isn't it? I almost don't care about SHIII anymore, I'm having too much fun with the wheels/slipsticks.

Something has to be wrong with your numbers then. Like I said, I drew it on paper.
Either the first range has to be 1430, or the second has to be about 2300 meters.

[Vandecker]

Ah I get it now thank you very much:lol:, Nice work figuring this all out.

Now off to hunting:D.... once I escape this damn patrol craft :damn:

[Capt. S. A. Wood]

New here I guess. I have been reading the forums for a good month or more about DW and SHIV, but never had much to post about, was learning mostly. Have played 688(I) and the two aforementioned games so far.

I am baking here in this dorm room at 5:45 a.m. due to the lack of AC, so I can not really go to sleep. I produced a detailed step-by-step checklist of what Puster Bill put forth in the OP, because even though I suck at mathematics in the purest definition of sucking, I am intrigued by these slide rules. So before I go try out the methods in the game I figured I would just write a little checklist. Hope it is up to par and acceptable.

-----

Silent Hunter 4 - Wolves of the Pacific Slide Rule Targetting Checklist Using Model Pickett N909-ES

http://www.antiquark.com/sliderule/sim/n909es/virtual-n909-es.html

Checklist is for two-reading intervals. Intervals can be chained together for more accuracy.
Examples given by OP are in [square brackets], important things are underlined, variables are in bold, and scales are in italics.
Scales used are S, C, and D.

-----

1.a. Obtain range to target and divide by 1000 with precision of 3 as Initial_Range --- [7.000]
1.b. Obtain bearing of target from own ship bow as Initial_Bearing --- [65]
1.c. Start chronograph and wait for 195+ seconds --- [0]

2.a. Stop chronograph and obtain elapsed time divided by 100 with precision of 2 as Time --- [2.40]
2.b. Obtain range and divide by 1000 with precision of 3 again as Final_Range --- [4.000]
2.c. Obtain bearing from own ship bow again as Final_Bearing --- [45]

3. Pause if desired --- [Nap Time]

4.a. Obtain bearing difference of Initial_Bearing and Final_Bearing as Delta_Bearing --- [20 = 65 - 45]
4.b. Align S (Delta_Bearing) with D (Final_Range) --- [S_20 | D_4.000]

5.a. Obtain new S value aligned with D (Initial_Range) and minus Delta_Bearing as Temp_Bearing --- [17 = (S_37 | D_7000) - S_20]
5.b. Obtain bearing difference of Delta_Bearing and Temp_Bearing as Offset_Bearing --- [3 = 20 - 17]
5.c. Adjust S by Offset_Bearing --- [3]

6.a. Obtain new S value aligned with D (Final_Range) as Final_AOB --- [23 = S_23 | D_4.000]
6.b. Obtain new S value aligned with D (Initial_Range) as Initial_AOB --- [43 = S_43 | D_7.000]

7. Obtain new D value aligned with S (Delta_Bearing) as Delta_Range --- [3.500 = D_3.500 | S_20]

8.a. Align C (Time) with D (Delta_Range) --- [C_2.40 | D_3.500]
8.b. Obtain new D value aligned with C (1) as Speed --- [14.6 = D_14.6 | C_1]

9.m. METRIC: Align C (5.144) with D (Speed) --- [C_5.144 | D_14.6]
9.i. IMPERIAL: Align C (5.626) with D (Speed) --- [C_5.626 | D_14.6]

10. Obtain new D value aligned with C (1) as Knots --- [28.2 or 26 = D_28.2 or D_26 | C_1]

-----

Input relevant values into TDC and have a nice day

-----

+ Full credit goes to Puster Bill of course

- Wood

Edit: Changed variable name WTF_IsThis to Delta_Range thanks to clarification from don1reed
Edit: Various changes made to match OP's changes, which should match up now

[don1reed]

Nice job, Woody, and welcome aboard.

...one minor correction... see para 8.c., I believe should be: [6.85 = C_3.5|D_2.40]

@ Bill: Check your PM.

[Capt. S. A. Wood]

Edit: Post deleted since I was incorrect and don1reed was right, and we do not need confusion around here :)

[don1reed]

gotcha :up:

WTF 3.5 = distance the target travelled between the two sightings, which is really 3500 yds. if using imperial.

[Capt. S. A. Wood]

gotcha :up:

WTF 3.5 = distance the target travelled between the two sightings, which is really 3500 yds. if using imperial.

Ahh, okay. I thought it was the distance traveled, but when I tried to work it out with the time and speed I got weird numbers, but I was doing it metric wise is why. Hey, it was 5 a.m. :)

[jmr]

I am baking here in this dorm room at 5:45 a.m. due to the lack of AC, so I can not really go to sleep. I produced a detailed step-by-step checklist of what Puster Bill put forth in the OP, because even though I suck at mathematics in the purest definition of sucking, I am intrigued by these slide rules. So before I go try out the methods in the game I figured I would just write a little checklist. Hope it is up to par and acceptable.
Heh well I can state as a matter of fact you don't suck at math as much as I do :}

Your instructions really cleared up a lot of what I wasn't getting in the first place but now I have a bit more confidence with my slide rule.

[Puster Bill]

OK, everyone who has been using my instructions for targeting, little did you know that I am a double agent working for both the British and Japanese navies! If you followed the instructions I gave you, you were sure to miss!

Actually, I made a stupid mistake :damn:

But, I'm man enough to admit it when I do.

Thanks to don1reed for pointing out an egregious mistake I made. Go ahead and run through the instructions again. This time, I'm almost positive that they might be correct.

[jmr]

Aww no worries. Hell if it wasn't for this thread you started I wouldn't be the proud owner of two real slide rules :rock:

[Vandecker]

^^ I'm with jmr, this is the only thread I've been able to find where someone even suggests a method to calculate AOB with a standard slide rule.

Even if you did make a small mistake at least you gave the rest of us an idea of how to do it, and for that I am indebted to you:yep:

[Puster Bill]

I think one more worked example would be nice. I'm the special student that needs extra help :lol::lol:

My next question is what do you do about an AOB larger than 90 degrees?

For example, I was messing around with the Torpedoes mission in the SHIII naval academy with the C2 freighter (which starts with an AOB of 110 starboard):

Bearing 1: 345 Range 1700m
Bearing 2: 000 Range 1770m

With a bearing difference of 15 degrees, how do you "fit" 15 degrees between 1700 - 1770?

Ok, I went back and did this problem myself with my corrected instructions.

Here is what I got:


OBS A: 1700 345 ??? 0
OBS B: 1800 357 ??? 165

fiddling, I find that there are twelve degrees that fit between 1700 and 1800 starting at 68 degrees and ending on 80 degrees. Subtracting both from 180 (because target is moving *AWAY* from us) gives AOB's of 122 and 100, respectively:

OBS A: 1700 345 100 0
OBS B: 1800 357 122 165

This gives us a distance traveled of 380 meters, which gives a target speed of 2.3 meters per second, or 2.24 knots.


I actually plugged those numbers for OBS B into the TDC, and got a hit on the stern of that C2 in the training mission. That might be because I rounded my distance numbers to the nearest hundreds.

EDIT: I don't remember if I opened the tube before I fired! That could explain the hit that far astern.

After the torpedo hit, I had the weapons officer do a solution:

Range: 1869
AOB: 123
Speed: 0 (because I blew the prop off of him!)

Not too bad.

[don1reed]

I hate to say this...Bill, you did it again. I think your shot hit aft because the C2 was doing 4 knots.

380m / 165s = 2.3 m/ps

2.3 / .51 = 4.5 knots

edit: If you're using the A & B scale on your sliderule...be aware those scales are mainly used for the squares & square root of the C & D scales. The left side for odd numbers of digits, i.e., 1, 123, 12345...and the right side for even numbers of digits 22, 4444....

All the simple math problems should be kept on the C & D...it's like mixing apples and pc's. (oranges). But, if you have a rule with a folded scale, i.e., CF, DF, CIF, then, those scales will integrate with the C, D, & CI scales.

[Puster Bill]

I hate to say this...Bill, you did it again. I think your shot hit aft because the C2 was doing 4 knots.

380m / 165s = 2.3 m/ps

2.3 / .51 = 4.5 knots

edit: If you're using the A & B scale on you sliderule...be aware those scales are mainly used for the squares & square root of the C & D scales. All the simple math problems should be kept on the C & D...it's like mixing apples and pc's. (oranges). But, if you have a rule with a folded scale, i.e., CF, DF, CIF, then, those scales will integrate with the C, D, & CI scales.

I just re-did the problem from the beginning, and I got 3.1 knots, which actually squares pretty well: I was moving at about 1 knot towards the target.

By the way, that target has a known speed of 2 knots.

I have to use the A scale against my S scale, because my S scale goes from about 38 minutes to 90 degrees, instead of the standard S scale that goes from just under 6 degrees (the center index of my A scale falls right at 5 degrees, 45 minutes when the ends are aligned).

I used the C and D scales for everything else.

By the way, are my instructions at the beginning of this thread correct now?

[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.

http://img68.imageshack.us/img68/5664/amobocu1.th.jpg (http://img68.imageshack.us/my.php?image=amobocu1.jpg)

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.

[ronbrewer]

Just curious, is there a chance that the statement:

"I move the slide until there is 20 degrees difference on the S between the 4 and the 7 on the S scale."

Should read:

"I move the slide until there is 20 degrees difference on the S between the 4 and the 7 on the A scale."

The reference to the 4 and 7 seem to be on the A scale in the picture, but I could be misunderstanding the procedure.

Thanks,
Ron

[don1reed]

That statement is correct for the "type" of sliderule used by the author, which is, I believe, a Sterling, pocket, 6" sliderule. The std for the times was a 10" with different configurations and more scales. Although the major manufacturers of the times did build some elaborate 6" models; but, each had their own instructions.

[Puster Bill]

Just curious, is there a chance that the statement:

"I move the slide until there is 20 degrees difference on the S between the 4 and the 7 on the S scale."

Should read:

"I move the slide until there is 20 degrees difference on the S between the 4 and the 7 on the A scale."

The reference to the 4 and 7 seem to be on the A scale in the picture, but I could be misunderstanding the procedure.

Thanks,
Ron
You are correct. Fixed that in the original post.

[Puster Bill]

That statement is correct for the "type" of sliderule used by the author, which is, I believe, a Sterling, pocket, 6" sliderule. The std for the times was a 10" with different configurations and more scales. Although the major manufacturers of the times did build some elaborate 6" models; but, each had their own instructions.

Actually, it's a 10" Sterling 'Precision'.

This takes you to a decent picture of one:
http://www.sliderulemuseum.com/Sterling/S150_Sterling_589_Senior_red_txt_slider.jpg

[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]

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]

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]

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.

http://img68.imageshack.us/img68/5664/amobocu1.th.jpg (http://img68.imageshack.us/my.php?image=amobocu1.jpg)

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... :up:

[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:

http://img147.imageshack.us/img147/734/amobo1fn8.th.jpg (http://img147.imageshack.us/my.php?image=amobo1fn8.jpg)

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]

@Bill:

http://img147.imageshack.us/img147/734/amobo1fn8.th.jpg (http://img147.imageshack.us/my.php?image=amobo1fn8.jpg)

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/military/library/policy/navy/nrtc/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/showthread.php?t=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!:up:

[Spin Doctor]

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

[Puster Bill]

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 :oops::lol:

[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.

[don1reed]

A lotta years ago, I got a 1st class FCC Radio/Telephone commercial license (back in the days when you could still get one of those) and took the exam using a sliderule...gotta laugh, the FCC engineer winked and said, "You should do allright on the test, son, you've got all the answers in the palm of you hand." :) Passed all the elements that day...he was right.

All the best,

[Puster Bill]

A lotta years ago, I got a 1st class FCC Radio/Telephone commercial license (back in the days when you could still get one of those) and took the exam using a sliderule...gotta laugh, the FCC engineer winked and said, "You should do allright on the test, son, you've got all the answers in the palm of you hand." :) Passed all the elements that day...he was right.

All the best,

You know, I was thinking about getting one myself almost 20 years ago, but I couldn't for the life of me figure out why I should. I stuck with just the ham radio license. I figure that if I started doing radio stuff for work, it would cease to be fun anymore.

It's still fun.

Last week was Submarines on the Air, but due to family obligations I wasn't able to work any of them. I've already got QSL cards from the USS Torsk, USS Silversides, USS Batfish, USS Growler, U-505, USS Ling, USS Requin, USS Cod, USS Cobia, USS Becuna, and USS Clamagore.

[Puster Bill]

Bump for the benefit of newbies.

[MudMarine]

Ye Gad's I can remember my Dad's attempt at teachin me ta use a slideruler. I did not listen, like the young fool I was. :damn:
Ya for me it was like hittin a breakwall. Heck I would think when would I use this junk. My dear ole Dad was not so dumb after all.

Math my worst subject, well I guess if I want the tonage, I need to relearn and learn the sliderule.

[Puster Bill]

Ye Gad's I can remember my Dad's attempt at teachin me ta use a slideruler. I did not listen, like the young fool I was. :damn:
Ya for me it was like hittin a breakwall. Heck I would think when would I use this junk. My dear ole Dad was not so dumb after all.

Math my worst subject, well I guess if I want the tonage, I need to relearn and learn the sliderule.

Don't feel bad: Slide rules were already on the way out when I was learning math. I remember fooling around with one when I was young, but never learned how to use it.

Now that I own a couple, I realize that they have to be about the coolest implements ever devised, outside of the flintlock, of course.

[MudMarine]

Puster Bill,
I see Ya made the Circular Slide Rule. I downloaded it and I have a question about its make:

1. Is the curser sheet One Circular curser with two straight cursers or five; two straight cursers,with three sperate scales; C, B, and K?

Note: Office Max and Office Depot can laser print transparent sheets for trans parent cursers. I recommend, WilsonJones, presentation Style, clear binding cover-gloss finish, 8 1/2 by 11 in. Letter size. Dedending on location each transparency will cost Ya about a buck each.

[MudMarine]

Skippers,
I know we are looking for exact range but is it realistic? I made a copy of Submarine Torpedo Manual, Dated May 1950. Thank you geosub1978, for posting the link to this manual.

From Page 31 of Manual, section 5-7
(h) The following points should be kept in mind in height determinations:
(1) Masthead heights may be purposely altered by enemy to cause inaccuracies in periscope range.
(2) Tops of the mast may be camouflaged in such manner as to be invisible under average visibility conditions at any except short range.
(3) Funnel height is normally sufficient to insure thats smoke which is blown in direction of the bridge by a tail wind will pass well over the bridge.
(4) Coal burners require taller funnels to insure adequate draft.
(5) Funnels of modern vessels having forced draft do not require as tall a funnel as older vessels without forced draft.
(6) Diesel propelled ships require no draft. Funnels are normally short, are not required, and generally have such dimenstions as to provide a good appearance on the ship.
Regardless of the methods employed by individual Approach Officer, skill in estimating masthead heights, and the ability of to obtain accurate ranges can be acquired and maintained onlyby constant practice. Even when radar ranges are available during an approach the Approach Officer should also obtain telemeter ranges as a means of improving and maintaining his skill.

From reading this I find that those sub skippers in WWII had a problem with range determination also. It was only with the advent of good radar and the telemeter that accurate ranges could be determined in 1950. So fine tuning things that accuracy for this simulation realy making it 100% reallistic.

[XLjedi]

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/military/library/policy/navy/nrtc/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]

Howdy Arron.

Check this out: See Geosub1978's post above :

http://www.globalsecurity.org/military/library/policy/navy/nrtc/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/showthread.php?t=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.

[Puster Bill]

Puster Bill,
I see Ya made the Circular Slide Rule. I downloaded it and I have a question about its make:

1. Is the curser sheet One Circular curser with two straight cursers or five; two straight cursers,with three sperate scales; C, B, and K?

Note: Office Max and Office Depot can laser print transparent sheets for trans parent cursers. I recommend, WilsonJones, presentation Style, clear binding cover-gloss finish, 8 1/2 by 11 in. Letter size. Dedending on location each transparency will cost Ya about a buck each.

The cursor sheet is one circular cursor that includes the C, B, and K scales, and the two separate 'free' cursors.

[MudMarine]

Puster Bill,
I see Ya made the Circular Slide Rule. I downloaded it and I have a question about its make:

1. Is the curser sheet One Circular curser with two straight cursers or five; two straight cursers,with three sperate scales; C, B, and K?

Note: Office Max and Office Depot can laser print transparent sheets for trans parent cursers. I recommend, WilsonJones, presentation Style, clear binding cover-gloss finish, 8 1/2 by 11 in. Letter size. Dedending on location each transparency will cost Ya about a buck each.

The cursor sheet is one circular cursor that includes the C, B, and K scales, and the two separate 'free' cursors.

If that is the case the one I made is correct. Just need to practice using it.

I also got this one from www.griffenfly.com (http://www.griffenfly.com)
a virtual one for the computer.

[MudMarine]

Puster Bill,

Please get this thread posted to "Guides and Trainings: TDC, Radar, Sonar and More.... " This is a definate help for skippers of realism.

[Puster Bill]

Puster Bill,

Please get this thread posted to "Guides and Trainings: TDC, Radar, Sonar and More.... " This is a definate help for skippers of realism.

Done.

[MrSargyano]

What is the 3 minute 15 second rule?

Also, I did a dry run with 280° @ 4000 yards (A) and 283.5° @ 3200 yards 195 seconds later. I have 1.5 SHIV w/RFB -TMO so contacts are present, so I had 'general' ranges. Stadimeter and me do not seem get along even with SCAF that is integrated into RFB. Definately not at these ranges.

According to my calculations, observation A has an AoB of 13.5° and observation B has an AoB of 17°. Correct me if I am wrong on any of this please.


With a difference of only 3.5° I could not go down far enough on the standard S scale (<6-90). I got stuck. Now I presumed that I could use ST and read from the D. This gave me the number 8.35. I figured I needed to move the decimal over once more to the left. I wind up with 835 units/yards. Measuring on my map between my two marks gave 850 aproximately. While this seems close, there are a heckuva' lotta' numbers on this thing! confirmation would be greatly apreciated.

At this stage I'm sorta' lost in decimal transitions. I then slid 1.95 (seconds) on the C scale to .835 (units/yards) on the D scale (the very left of it). The right hand index mark of the C scale pointed to 9.4 (units per second) on the D scale.

So, now for the 'prestige'. I slide 5.6 on the C scale to 9.4 on the very, very left of the D scale and get my right hand C index at 9.4 (knots).

So now that I have typed all of this, I get the feeling that the '3 minute 15 second rule' means i do not have to translate 'units' to 'knots'. Needless to say I could still use some clearification on the moving of the decimals if nothing else.

Thanks in advance,
Mr Sargyano

PS I am currently useing the slide at http://www.antiquark.com/sliderule/sim/n3t/virtual-n3-t.html

[MrSargyano]

Pretty nice. Now if it would only help me shoot straighter ;).

My new Pickett N-500-ES slide rule (http://www.auctiva.com/hostedimages/showimage.aspx?gid=636041&image=144664218&images=144663899,144664051,144664218&formats=0,0,0&format=0)

[don1reed]

Howdy, MrSargyano.

The 3:15 min rule is to metric measure as the 3:00 min rule is to imperial measure.

Mariners use these rules to determine the speed of another vessel under their observation.

E.g. If it is determined that an observed vessel travels 0.8 km in 3:15 min., then,

the observed vessel's speed = 8 kn. If 1.5 km, then 15 kn. etc.

Imperial: Distance (yds) in 3:00 / 100 = speed in knots.

-...-

btw, nice Pickett :up: sweet.

[steinbeck]

My brain is fried. Maybe it's because I don't remember my trig from YEARS ago or that I just suck at math but I'm getting inconsistent results with my rule. I need an idiot's guide to these things.



Go here.......http://oughtred.org/flyers/OS-ISRM_SlideRuleSeminar.pdf for a PDF
D/L


steinbeck..........:yep:

[MrSargyano]

Good rules to know Don1reed! The more ways I know to find a solution, the more options I have when I need to calculate one. Not to mention give myself a sanity check if necessary.

Steinbeck, I will make a point to go over the one you have suggested to Jmr before I finish reading the two I have chosen. I have at this point found alot of sites on the slide rules and downloaded a select few PDFs after having perused many. Ought to be fun if I could just stop reading these forums and playing the game long enough to read them :know:. Fortunately, my in-game targeting has become sufficient enough that when I start practicing with the slide rule again, I will have a good point of reference.

Soon I will get rid of the box on the map (RFB w/o TMO) that marks the target locations. Wihtout that, things will get difficult once again. I use them to calculate AoB, speed, and verify solutions. All three of these things are easy as long as they are present. Even distance isn't terrible to calculate with them.

Measuring distance with the stadimeter (minutes of angle w/SCAF mod) will become critical at that point. SONAR will be my only available sanity check (that I know of) and it will not allways be available (surfaced) or sometimes even an option (DD's) let alone entirely accurate :rotfl:.

The challenge awaits.

Thanks ya'll,
Mr. Sargyano

PS I can tell allready this is going to be a great doc for me Steinbeck.

[Gangrene]

Or, unless you had one of these little bad boys!!!
http://www.youtube.com/watch?v=HYsOi6L_Pw4