Torpedo Spread Angle Calculator

[Nisgeis]

I've done a quick replica of part of the gizmo that the USS Torsk has on its gryo angle solver bay that allows you to calculate the formula:

No. of degrees total spread = (Target length in feet / 1,000) * (2,000 / Torpedo Run yds) * Sin(Torpedo Track Angle)

It does this in a graphical way, that you can easily and quickly trace out to get the total spread angle for a target. It's much easier than trying to work it out!

Now, it's a prototype at the moment and I had to make a few adjustemnts because I can't see anywhere in the game that tells you what length the topedo run is (it was on the gyro angle solver RL). Would anyone who is interested, particularly in manual targetting like to test it? It works to calculate spreads for auto targeting as well, but it less important.

EDIT: Released here: http://files.filefront.com/TSAC+v21pdf/;12192603;/fileinfo.html. Get the torpedo run time from the attack map and follow the instructions.
EDIT2: Changed file to V2.1 as V2 had a slight error in it.

[kylania]

"I have awesome, but would anyone want it?" Silly question, of course we would! :)

[Rockin Robbins]

I volunteer! That is a great improvement to the by guess and by golly spread.

And it would get me out of my Dick O'Kane attack rut. It's about time I found some innovative wrinkles in conventional targeting.:up:

[Nisgeis]

"I have awesome, but would anyone want it?" Silly question, of course we would! :)

Do I get feedback this time? :D.

If there's one thing I've learned, it's that the more realistic your mod/guide, the less people are interested in it. Personally, I think that plotting a target from radar readings and getting a track is the best way to use your stopwatch with it's authentic world war two tick-tock sound, but what do I know.

[Hitman]

Count me in :up:

PM me or post here a link to what you want to test, I think I can be able to give it a try this weekend :ping:

[Matilda]

I would like to help test your gizmo. I use MoBo alot for intercepting but would love something to assist with spead angle.

[breadcatcher101]

It would be neat having devices (working models) that were used in the war such as you are referring to. They also had a thing-of-a-gig called a "was/is". Maybe it is the same item you are talking about or one that does something else, I can't remember.

[joegrundman]

It would be neat having devices (working models) that were used in the war such as you are referring to. They also had a thing-of-a-gig called a "was/is". Maybe it is the same item you are talking about or one that does something else, I can't remember.
what you are talking about is an is/was, and this is old news here at subsim - many of us have made our own and use them regularly :D

the original thread, including pdfs for making your own

http://www.subsim.com/radioroom/showthread.php?t=106923&highlight=iswas

original instructions for using it

http://www.hnsa.org/doc/attackfinder/index.htm

note, this tool is not the same as a spread angle calculator

[breadcatcher101]

An is/was it is/was then.:)

I had read about it's use in one of my books, forgot which one, maybe "Clear the Bridge", about the Tang. Anyway I checked out the link and I have a new project now in trying to make one.

I thank you for providing the link and for setting me straight on the correct name.

[Nisgeis]

Thanks to all the victims, er, I mean volunteers. I'll send you a PM with the download link in it on Monday. What I have atm is a replica of what is on the Torsk, but I can think of some improvements.

[Rockin Robbins]

Clearing a spot for it in my S-boat. Hope my TDC operator is up to it. He just missed four of four in a Dick O'Kane. Shooting torpedoes is harder in RFB and the sugar boat! No ice cream for him tonight though...:down:

[Matilda]

Looking forward to it. Just let me know.

[Nisgeis]

Testers should all now have a PM from me.

[Matilda]

I got your PM and DL'ed the file. Went over the examples and have a decent grasp of how it works. I'll let you know what kind of results I get in game.

[Nisgeis]

Looking forward to feedback. One really useful thing is the maximum torpedo run time. You can use this to see if your shots will actually reach the target. I was a bit surprised how low some of the run times were for maximum range. It'll cut down on some wastage I'm sure.

[Rockin Robbins]

Working out some glitches that I can't explain. Did two cruises without seeing a single target. Rerolling pristeen SH4 and reapplying all mods. Love the device! Too bad SH4 doesn't lend itself to making an in-game pulldown like SH3 does. A slide rule with no moving parts that you can use without drawing on it. It's great!

[breadcatcher101]

I thank you as well. I'll see how good I am with it. Is this by chance what was sometimes called a banjo?

[Nisgeis]

I'm not sure what this is called, but it's not a banjo. A "Banjo" is the name given to the 'Torpedo Angle Solver Mk. VIII' and it is described, with drawings here:

http://hnsa.org/doc/banjo/index.htm

As you can see, it looks a bit like a banjo.

The Is/Was (Submarine attack course finder) is described here:

http://hnsa.org/doc/attackfinder/index.htm

[Pisces]

Looking forward to feedback. One really useful thing is the maximum torpedo run time. You can use this to see if your shots will actually reach the target. I was a bit surprised how low some of the run times were for maximum range. It'll cut down on some wastage I'm sure.If you want more feedback, why not make your beta test open so more people can download it. I don't have Sh4 on my pc but I'm allways a sucker for these kind of tools.

[Matilda]

So far I like the system. It is better than just throwing torpedos away (ones that never have a chance to hit). I am successful with it at shorter distances (no big suprise there). I have been trying it at extreme ranges, right out at max run, and wish the measuring gradient was more precise. Well I'm thinking that is more a problem of how the game is set up than the tool. I'll keep using it and see if I can come up with an idea, because even if the tool has a finer gradient how could I translate that into the game? Thanks for the oportunity to help. I'll be in touch.

[Nisgeis]

If you want more feedback, why not make your beta test open so more people can download it. I don't have Sh4 on my pc but I'm allways a sucker for these kind of tools.

It's open to anyone who wants to have a look. My working theory is if someone can't bring themselves to post 'I'll test this', then they are unlikely to post any feedback ;).

[Nisgeis]

So far I like the system. It is better than just throwing torpedos away (ones that never have a chance to hit). I am successful with it at shorter distances (no big suprise there). I have been trying it at extreme ranges, right out at max run, and wish the measuring gradient was more precise. Well I'm thinking that is more a problem of how the game is set up than the tool. I'll keep using it and see if I can come up with an idea, because even if the tool has a finer gradient how could I translate that into the game? Thanks for the oportunity to help. I'll be in touch.

Which measurement scale? I'm going to be making the 'Torpedo Track Angle' into 5 degree increments, instead of 10 degrees. Would that help?

I think the longest range shot that was successful was about 4,500 yards, any at longer range weren't succesful, the torpedo run is very long and any innacuracy is magnified. If you aren't sure of your data you should increase your spreads.

The spread calculator will give you the angular target length, so if you look at the value of 900 foot target length with a torpedo run of 3,000 yds, at a track angle of 90 degrees, it says the angular target length is 6 degrees. So if you did fire three torpedoes, a 100% coverage would be 3 degrees right, 0 degrees for MOT, 3 degrees right. But that would give you a situation where a slight error would make either of the 3 degree torpedoes miss. So, if you have a really good solution, go for a 75% spread to get hits along most of the length, with a bit of give. If you are less confident, use 100%, which will give you 2 out of 3 hits of your data is resonable. If your data is shaky, use more coverage, 150% or 200%.

Using a higher coverage, you'll get less hits for certain, but you are more likely to get some hits. I'm wondering if I should put in some sort of coverage calculator, so you don't have to work this stuff out.

I'm also considering removing the torpedo run lengths higher than 4,000 yds as it's probably not a good idea to be shooting at that range... Hmmm, I'll have a think about all this stuff. The feedback is great, as it makes me think.

Hitman gave me some good ideas as well.

[Hitman]

One thing I forgot to mention in the PM (Now that I see this is being discussed in public): The vertical scale goes up to 1200 feet, but I don't think that any WW2 ships was that big. In my opinion you could limit it vertically to 800 feet, that's enough to get a good salvo at the Yamato. By doing that and also eliminating the lines for extreme ranges you could expand the table to a bigger size and allow for better precision and extra lines without cluttering it :up:

What format are you working with? tga, BMP? :hmm: I think I could put it in the game if you can provide a graphic in one of those formats.

[Nisgeis]

One thing I forgot to mention in the PM (Now that I see this is being discussed in public): The vertical scale goes up to 1200 feet, but I don't think that any WW2 ships was that big. In my opinion you could limit it vertically to 800 feet, that's enough to get a good salvo at the Yamato. By doing that and also eliminating the lines for extreme ranges you could expand the table to a bigger size and allow for better precision and extra lines without cluttering it :up:

Yes, I wondered about that myself, however the first version is a replica of what the Torsk has - and that goes up to 1,200 feet. You'd save a small amount of space by taking it down, but you'd still need the first part for the higher angle shots or shorter craft. Thinking about this made me spot a mistake and I need to check something :hmm:.

What format are you working with? tga, BMP? :hmm: I think I could put it in the game if you can provide a graphic in one of those formats.

Corel Draw, as i can use it and it's vector graphics, so it can be easily scaled without messing it all up. It also produces very small PDF files :D

[Matilda]

Yes I think 5 degree gradient would be better. The problem I was talking about the game having was that the gradient there is 1 degree. You can adjust in between those gradients, however it only takes like an hour, and it isn't consistent. At 4000 yd even a 1 degree spread gets pretty large. I like it so far. I would say it has given me a 15% improvement outside 1500 yd, and about a 20 to 25 % improvement inside that range. I don't think I've improved alot outside 3000 yd but I'll keep trying.

[Hitman]

I lack the necessary skills in maths to tell for sure, but I somehow think that the scales are not all completely correct :hmm:

The separation between some of the torpedo runs doesn't seem proportional (Even if it becomes shorter the longer the run).

Have you verified it mathematically, or is just a direct copy of Torsk's instrument? :-?

[Hitman]

Nisgeis,

I can confirm that is is indeed possible to put this scale as a graphic in the in-game Attack Map :D

I did a quick test with positive results, but will need to tweak the position a bit.:rock:

[Hitman]

I have it working as a fixed image, I suppose it could be done as draggable image, but I would need to learn how to do it :hmm:

Here is a sample:

http://img357.imageshack.us/img357/4461/testcd0.th.jpg (http://img357.imageshack.us/my.php?image=testcd0.jpg)http://img357.imageshack.us/images/thpix.gif (http://g.imageshack.us/thpix.php)

[Nisgeis]

I lack the necessary skills in maths to tell for sure, but I somehow think that the scales are not all completely correct :hmm:

The separation between some of the torpedo runs doesn't seem proportional (Even if it becomes shorter the longer the run).

Have you verified it mathematically, or is just a direct copy of Torsk's instrument? :-?

Yes, I did verify it, however... I made a very small error, the degrees along the top go 8, 9, 10, 12. Either I didn't put it in, or I accidentally deleted it. Funny how I never noticed. The 2,000 yds anmd below lines consequently a small amount out. I'll correct that.

[Nisgeis]

I have it working as a fixed image, I suppose it could be done as draggable image, but I would need to learn how to do it :hmm:

Here is a sample:

http://img357.imageshack.us/img357/4461/testcd0.th.jpg (http://img357.imageshack.us/my.php?image=testcd0.jpg)http://img357.imageshack.us/images/thpix.gif (http://g.imageshack.us/thpix.php)

That looks quite readable. I think though it would be better if it was larger and a pull out version. i don't know how to do it either :D .

[Rockin Robbins]

Personally all I care about is the angular size of the target. Beyond that I can extrapolate and interpolate in my head to get "close enough" answers. We can get all hung up on that 4th significant figure and forget that our measurements are only accurate to 2 significant figures and our "accuracy" is absolutely meaningless.

So all I care about is to know that the target is between 3º and 4º wide. I can't shoot accurate to a half degree anyway!

[Pisces]

If you want more feedback, why not make your beta test open so more people can download it. I don't have Sh4 on my pc but I'm allways a sucker for these kind of tools.

It's open to anyone who wants to have a look. My working theory is if someone can't bring themselves to post 'I'll test this', then they are unlikely to post any feedback ;).Fair enough. Hitman's screendump made me even more curious on how to use this thing. Let me have a look at it please.

As for the math, the formula in your 1st message works if 2 torpedo's should hit at 1/3rds of the targets angular length on bow and stern side. I really need a description on how to use that table/graph to compare this with it. It makes little sense to me right now. Also, just to make sure we have the same terminology: trackangle= complement of AOB (=180-AOB) at hit-time?

[Matilda]

That is the point I was trying to make, Rockin Robbins said it much better than I. The tool as it is set up is fine. It is the game that makes it that 1 degree is the smallest gradient that can be used.

[Hitman]

I think though it would be better if it was larger and a pull out version

Yes, and another good reason for it is that SH4 does not auto-scale everything when changing resolutions. Thus, this graphic that looks relatively small at my 1400x1050 screen will cover nearly all the screen when running at 1024x768 :damn:

[joegrundman]

I've always used the formula from the submarine torpedo fire control manual 1953

It's basically the same as this, but it's very easy to do mentally once you've understood the components of the equation

Torpedo run (yards)/2000 x target length (feet)/100 x sine tta x %coverage/100

It's simple if you think about it

let's say you fire at 2000 yards, then the first part of the equation is 1

let's say you fire at 1000 yards, then the first part is 2

and that takes care of 90% of your firing situations

target length - if you don't know, say it's 500feet, which is a medium. 500/100=5, but wahtever it is you only have to round to the nearest 100 - you don't need hyperaccuracy.

if you don't know what sine 90 is, you should be back on automatic targetting, and let's face it, most shots are at about 90 degrees

coverage is simply how much of the target length do you want to consider - for example if the target is far away and zigging maybe you want a 200% or even 300% coverage, in which case guess what? multiply the end result by 2 or 3. Otherwise if you want a normal spread to simply cover the full length of thetarget, then 100%/100=1!

So for the most typical of all situations, aiming to 100% cover the target on a roughly 90 degree shot at a normal range of 2000 yards, at an average sized merchant, the solution is:

2000/2000 x 500/100 x 1 x 1
= 1x 5 x 1 x 1
=5 degrees

The graphical table above gives the value of 4.5 for this situation, which is, as you see, close enough. if you needed accuracy, you wouldn't be using spreads, would ya?

Now even if maths turns you off it's important to note the following - the result for both the calculation above AND the spread angle obtained by using this graphical device is the TOTAL spread angle - if your result is 5 degrees, and you want a stern, mot, bow spread, then the first torp will need a deflection of 2.5 degrees one way, the second 0 deflection, the third a 2.5 degree defelction the other way. - That is if you are using fleet boats.

The U-boat TDC will sort out spreads for you if you just input the total spread.

[Rockin Robbins]

Hitman, can you make the white transparent so the black lines are actually on the attack map? That way the underlying part of the attack map would still be useful. Looks great and very readable!

Nisgeis, I like tha chart as is. I see no reason for more precision/confusion to be built into a chart that is designed to be read quickly without marking on it. In other words, it has to be usable strictly by inspection.

[Wilcke]

Nisgeis,

Been following this, looks good and nice addition. I think you have it where you want it for 99.9% of the customers.

[Hitman]

Hitman, can you make the white transparent so the black lines are actually on the attack map? That way the underlying part of the attack map would still be useful. Looks great and very readable!


Making it transparent is just a matter of adding an alpha channel to the TGA, but for it to look the best possible I need the original image in two layers format.

If it is a draggable item I don't think a transparent background is of big relevance, if it stays fixed then of course I will try to add it :yep:

[Hitman]

Never mind the above, transparency done:

http://img151.imageshack.us/img151/3117/31447539lh8.th.jpg (http://img151.imageshack.us/my.php?image=31447539lh8.jpg)http://img151.imageshack.us/images/thpix.gif (http://g.imageshack.us/thpix.php)

[joegrundman]

That looks really great!

I don't think that making it draggable is possible with SH4, unless you attach it to the radio, gramaphone or stopwatch

[Rockin Robbins]

Hitman! Nisgeis! You have created a thing of beauty! Time to release it! Time to bring it to the RFB crew for inclusion too! And putting it on the attack map is a work of genius! Time to publish the mod and infiltrate Real Fleet Boat. This is as big as the nomograph, maybe bigger. Great, great work!:up::up::up::up::up::up::up:

This is an exciting time to play SH4!

[Hitman]

Many thanks for your comments and encouragement RR :up:

I will wait until Nisgeis does what he considers his final version and then I will try to put it in the game in the way he sees best. It's his work after all, and I just add it in-game, so I will follow his preferences.

That looks really great!

I don't think that making it draggable is possible with SH4, unless you attach it to the radio, gramaphone or stopwatch

Yes, i was starting to suspect that after seeing a bit how draggable items have been added in the past :damn:

Maybe a slide-out, like the bigger compass could work? :hmm:

[joegrundman]

Many thanks for your comments and encouragement RR :up:

I will wait until Nisgeis does what he considers his final version and then I will try to put it in the game in the way he sees best. It's his work after all, and I just add it in-game, so I will follow his preferences.

That looks really great!

I don't think that making it draggable is possible with SH4, unless you attach it to the radio, gramaphone or stopwatch
Yes, i was starting to suspect that after seeing a bit how draggable items have been added in the past :damn:

Maybe a slide-out, like the bigger compass could work? :hmm:

which slideout bigger compass?

[longam]

Back to the ol menu_ini file to have a pull down version.

Capt Cox Pull Down Map
http://www.subsim.com/radioroom/showthread.php?t=112750

Zamboni's menu_ini tut.
http://www.subsim.com/radioroom/showthread.php?t=111832

[joegrundman]

Back to the ol menu_ini file to have a pull down version.

Capt Cox Pull Down Map
http://www.subsim.com/radioroom/showthread.php?t=112750

Zamboni's menu_ini tut.
http://www.subsim.com/radioroom/showthread.php?t=111832

that's what i said, longam, when i said you can attach it to the radio or gramaphone

personally i think the fixed graph on the attack map is the better solution

[Hitman]

Hummmm forget it Joe, I just found out that it is ALSO linked to the draggable radio :damn:

http://www.subsim.com/radioroom/showthread.php?t=127076

[joegrundman]

Quite some time ago now i attempted to make an in-game Submarine Attack Course Finder/Is-was, like the Angriffscheibe, for SH4. I spent a long time making some nice images but just couldn't get it to work satisfactorily. I found out quite a bit about the menu limitations on SH4:-?

[Nisgeis]

Time to bring it to the RFB crew for inclusion too!

I have no evidence that this was actually used during WWII. I don't know what they used as 'spread cards'. All I do know is if you look at a picture of a Mk 4. TDC, there is a diagram that looks similar(ish) attached to the top of the angle solver unit. What I have here may be an interpretation of that chart, as it is on the bottom below the gyro angle solver dials.

[Nisgeis]

The first thing I ever looked at when I started modding was the menu_1024.ini file. I noticed that the screens with pull out options had child windows set up, but it seemd to be hard coded which IDs were pullouts.

I only started this as a printable chart (with instructions for use), but if people want it on the attack map, it suits me if Hitman can do that. Final version should be ready on Monday for testing.

[LukeFF]

I have no evidence that this was actually used during WWII. I don't know what they used as 'spread cards'. All I do know is if you look at a picture of a Mk 4. TDC, there is a diagram that looks similar(ish) attached to the top of the angle solver unit. What I have here may be an interpretation of that chart, as it is on the bottom below the gyro angle solver dials.

You should ask AVGWarhawk about this, since he is a volunteer helping to restore the Torsk.

[peewee]

I thank you as well. I'll see how good I am with it. Is this by chance what was sometimes called a banjo?


Nah, a banjo is a British Army sandwich...e.g.

squaddie......."give us two bacon banjos and a cuppa please luv"

NAAFI girl..........." 'ere ya go, that'll be a quid"

squaddie........"Fanks"

:D :D :D :D :D :D :D

[Nisgeis]

Second and hopefully final version has gone out to those who requested it. This one should be good.

[Hitman]

All right, the tool works as expected and I really can't add much to what I said before. The new scales help much with the shorter/medium shooting distances, which are the most used ones and everything else is OK. If anything, more subdivisions in the torpedo run time to run length would be nice, but there really isn't much more space for it :hmm:

Anyway, I suspect that a slide ruler would be the perfect tool here. If you can think about something along those lines, I *think* that I can provide a dirty but effective method of bringing it in-game, using a fixed background image and then a draggable one you can move along the first.

If you are happy with this as final version, just tell me and I will do an in-game version ASAP.

Cheers :up:

[Nisgeis]

If you are happy with this as final version, just tell me and I will do an in-game version ASAP.

Cheers :up:

I am and no one else has complained about it. :D

[SteamWake]

Where can I get ahold of the 'printable' version ? :hmm:

[Nisgeis]

Where can I get ahold of the 'printable' version ? :hmm:

The plan would be to release a JSGME mod that has also the PDF in it, so if you don't want it as an in game mod, you don't have to.

[SteamWake]

Where can I get ahold of the 'printable' version ? :hmm:

The plan would be to release a JSGME mod that has also the PDF in it, so if you don't want it as an in game mod, you don't have to.

Just seems like that map is gonna start to get crowded with the nomograph and all.

[Nisgeis]

Just seems like that map is gonna start to get crowded with the nomograph and all.

I agree, I won't be using it that way, but other people seem to like it that way, so just offering some choice.

[Rockin Robbins]

Where can I get ahold of the 'printable' version ? :hmm:
The plan would be to release a JSGME mod that has also the PDF in it, so if you don't want it as an in game mod, you don't have to.
Just seems like that map is gonna start to get crowded with the nomograph and all.

But the implementation I saw was that the TSAC went on the attack map: a great solution! The nomograph is on the nav map. No conflict there at all. But the real solution is to make the mod with the PDF for those who choose not to install the mod but still want to use the chart.

Me? I'll install it. I like to keep my tools in the game. Can't spill coffee on 'em that way.:up:

[old_tex]

I found this link while searching for information. http://www.hnsa.org/doc/attack/
Old_tex
:up:

[Rockin Robbins]

I found this link while searching for information. http://www.hnsa.org/doc/attack/
Old_tex
:up:

Ah, the gold standard for terminology when talking about submarine attack targeting. If you wonder where the words we use come from, look no further than there. When we talk about a constant bearing attack, don't assume what it is, look it up there. That is why I refer to the Dick O'Kane attack method having a longitudinal spread. Authentic language ensures communication is taking place. This site is a must see!

[Nisgeis]

As no one has come back with anything that needs changing, the PDF can now be downloaded from:

http://files.filefront.com/TSAC+v21pdf/;12192603;/fileinfo.html

Get your torpedo run time from the attack map (it's at the end of the greeny black torpedo run line). I've no idea where people are getting the target lengths from. All other instructions are included in the PDF, with three examples, showing how to use it.

Edit: V2.1 added instead of V2, as there was a slight error.

[Hitman]

I hope I will have this weekend the in-game version done, and will send it to Nisgeis for approvement :up:

[Rockin Robbins]

Thank you both. This is a large void in our abilities that you have cured, plus the chart is useful for other things too, as we found out while formulating the John P Cromwell technique. I think I'll use it more than I do the nomograph and I know I'll do a lot more conventional targeting now that I can do divergent spreads with confidence.

Nisgeis, Hitman, great job!

[Eddy Lawson]

Ops... sorry i wanted to reply to another thread! too many open windows!

[Rockin Robbins]

No you don't! You really want to download this thing and put it to use. It is really great!

[I'm goin' down]

I just studied the Torpedo Spread Angle Calculator thread. Nisgeis, congratulations on a masterpiece. My son has not seen it yet and will be beside himself when he reads it.

Has it been put into a mod? Can it be pasted on the attack map? If so, are there easy to following structions?

Many of the posts in the thread are from individuals on the cutting edge of this game's technology, and it is one of the most interesting running commentaries I have come accross. I am wondering how the calculator will work when I used manual targeting. RFB has a mission called the Dick O'Kane, where it is a perfect place to practice it. I can save the mission right before I set the torpedo spread angle, so I can replay it quickly and efficiently to test it.

I have one question about the pdf. What is the torpedo track angle? Is it the angle that the arrow points to on the image representing my boat on the TBT? I think it is, but I am not sure.

[I'm goin' down]

The torpedo track angle is found by pointing the cursor at the arrow on the target on the TBT, not the by pointing the cursor at the arrow at your own boat.

If the torpedo spread angle calculator has been modded into the game please advise by leaving a reply.

[joegrundman]

it's already in rfb i think

[Rockin Robbins]

Has it been put into a mod? Can it be pasted on the attack map? If so, are there easy to following structions?
Hitman was working on that and it appears to have been dropped. He was going to put it on the attack map and we must bug him about that because I'd love to see it in operation.

I have one question about the pdf. What is the torpedo track angle? Is it the angle that the arrow points to on the image representing my boat on the TBT? I think it is, but I am not sure.
Nope. The torpedo track angle is the angle the torpedo makes with the target, with zero at the bow and 180 at the stern of the target. It's called the track angle because it is the angle the torpedo track makes with the target track. Here's an illustration from the Submarine Torpedo Fire Control Manual (http://hnsa.org/doc/attack/index.htm):

http://hnsa.org/doc/attack/img/pg01-12a.jpg

I guess that's about all the information I can supply based on the diagram, except that if you draw a line from the periscope to the target impact point, notice that it will be a different angle than the gyro angle. That is the parallax we've been talking about, due to the length of the sub and the torpedo reach before it begins its turn toward the target. Also notice the Angle on the Bow. The torpedo track angle is just the angle on the bow of the torpedo itself at the moment of impact!

[I'm goin' down]

RR, thanks for the information about the track angle. Here is a follow-up to our conversation yesterday.

How do you compensate for inherent TDC problems?

If the target's speed input into the stadimeter is 7.5 kts., the TDC interprets its speed as either 7 kts or 8 kts, as it rounds the target speed to the nearest knot. This results in a speed differential of 1/2 kt. Assume range, aspect ratio and AoB are correct. Because of the 1/2 kt. speed differential, the gyro angle for the torpedoes estblished by the TDC is incorrect.

If the TDC interprets the target's speed as 8 kts., it will set the gyro angle for torpedoes based on the target proceeding at that speed. But the target is not proceeding at that speed! Its actual speed is 7.5 kts., 1/2 kt. slower than the TDC's calculated speed. For example, if a target is proceeding from left to right, the torpedoes will run ahead of its bow (i.e. to the right), because the TDC assumes and calculates the torpedoes' gyro angle (and target's position at the point of contact) based upon a target's assumed speed of 8 kts. The TDC sets the gyro angle of the torpedoes to intercept the target based upon that speed. The torpedoes run ahead of the target's bow because the target is running at 7.5 kts, which is 1/2 kt. slower than the TDC's calculated speed of 8 kts. In reality (if that description is proper for a game played on a computer) the target's actual positon at projected point of torpedo intercept is behind the position calculated by the TDC because it is moving at a slower speed than the TDC data utilizes. This is not caused by an error on the part of the captain, who input the correct speed of 7.5 kts. into the stadimeter. It is the result of the TDC rounding the input speed of 7.5 kts to 8 kts. In my two tests, a total of eight torpedoes that were fired in salvos in two separate attacks in RFB ran ahead of the target's bow, missing their targets by a short distance.

Conversely, if the TDC interprets the target's speed of 7.5 kts. as 7 kts., just the opposite occurs. The TDC sets the gyro angle based upon a speed of 7 kts. But the target is actually going 1/2 kt. faster (7.5 kts) than the TDC's calculated speed (7 kts.). For example, if a target is proceeding from left to right, the torpedoes will run behind its stern (i.e. to the left), because the TDC assumes and calculates the torpedoes' gyro angle based upon a target speed of 7 kts. (1/2 kt. slower than its actual speed) and sets the gyro angle of the torpedoes to intercept the target based upon that speed. The torpedoes run to the left because the target's speed is 7.5 kts., which is faster than the TDC calculated speed of 7 kts. In contrast to the example in the preceding paragraph, the target's actual positon at point of impact is ahead of where where the TDC calculates its position because it is moving at a faster speed than the TDC data assumes. This is exactly what occurred with four torpedoes that were fired in a salvo in a campaign mission. One of the four torpedoes made contact near the target's stern for reasons explained below.

How to adjust or compensate for the TDC data error?

It seems to me the solution lies with setting the spread angle on the torpedoes, or by leading the target when firing. As to the former solution, presumably setting the spread angle for the torpedoes is a technique that can be used to adjust for the speed differential caused by data input errors inherent in the TDC. However, the onboard ship manual does not list the lengths of ships, which is an element of the torpedo tracking angle calculation used for setting torpedo spread angles. Also, even if the torpedo tracking angle is accurately set to ensure a proper spread angle for the torpedoes, the torpedo tracking angle calculation does not assist in overcoming the distance differential resulting from the discrepancy between a target's actual speed and the speed recorded in the TDC, which, as noted, can be up to 1/2 kt since the TDC rounds speed to the nearet knot. If the speed differential results in the torpedoes running ahead or behind the middle of the target or the area of the target where the TDC projects impact, it can (and in my examples, did) result in shots missing the targets.

If you try decrease or increase the lead angle when firing, I am not sure how to do it, and secondly, whether it is possible with manual targeting.

In each of the three attacks described above, I tried adjusting the torpedo spread angle. Since each target was heading from left to right, I set the torpedo spread angle to the right to increase the odds of hitting the target. Here is what happened.

1. The first two attacks occurred when the targets' speeds were 7.5 kts. and the TDC calculated their speeds at 8 kts. The targets' speeds were each 1/2 kt. slower than the TDC calculated. The torpedo spread angle should have been set to the left to compensate for the slower speed of of the target. Setting the spread angle to the right was a mistake and increased the liklihood the shots would miss to the right, which they did.

2. The third attack occurred where the target's speed was 7.5 kts. and the TDC calculated target speed at 7.0 kts. The target's speed was 1/2 kt. faster than the speed used in the TDC calculation. The torpedo spread angle was to the right. One torpedo made contact near the target's stern, and the other three missed to the left. The torpedo spread angle was insufficient to overcome the 1/2 kt. discrepancy between the actual and calculated speed for three of the four torpedoes, but I was guessing at the spread angle.

Is there any solution to this TDC generated problem short of guessing at the appropriate spread angle for the torpedoes?

If this post is hard to understand, note that I had a hell of a time writing it. (Note: The problem generated by the TDC was pointed out to me by Rockin Robbins.)