I come to realize

[wetwarev7]

Originally Posted by klh

When you're on a perpendicular attack course, you have formed a right triangle (from you to the target, from you to the intercept point on the target track, and from the target to the intercept point). The distances the target and the torpedo travel to the intercept point (where your torpedo goes boom) is related to their speeds. The ratio of the two (target speed / torpedo speed) is equal to the tangent of the lead angle (the bearing to the target at the time you fire). It is not necessary to know the range to the target, except to make sure your torpedo can travel that far).

It's just trigonometry!

See the Angriffsscheibe Handbuch, example # 16 for a more detailed explanation with pictures.

Wait a minute.....brain overload....rebooting....

So, the farther out I am from the ships course, the farther out the target is going to be from the intersection at the same angle? So no matter what distance you are at, the firing angle(say a bearing of 10 degrees) will allways ensure that you and the target are at the correct distance?

If so, why do I need to use a 20 degree bearing if I'm using a slower torpedo?

I don't know why this stuff confuses me. I aced trig in highschool, but maybe because it was so long ago, and I've never had a real world use for it till now....

[klh]

Originally Posted by wetwarev7

Wait a minute.....brain overload....rebooting....

Be sure to reboot to SAFE mode.

Originally Posted by wetwarev7

So, the farther out I am from the ships course, the farther out the target is going to be from the intersection at the same angle? So no matter what distance you are at, the firing angle(say a bearing of 10 degrees) will allways ensure that you and the target are at the correct distance?

Exactly!

Originally Posted by wetwarev7

If so, why do I need to use a 20 degree bearing if I'm using a slower torpedo?

Think of it this way. A slower torpedo will take longer to reach the intercept point (the target's track), so the target will travel further during that time. Therefore, you need to lead the target more.

And don't get hung up on the 10 or 20 degrees given in the example. You can calculate (or use tables like the real kaleuns did) the exact lead angle with the equation...

Lead Angle = Arctan (target speed/torpedo speed)

So if the target is making 12 knots, and you wish to fire a 30 knot T-III electric, then your lead angle is...

Lead Angle = Arctan (12/30) = 21.8 degrees

And as long as you're within 5000 metres of the target track, you should get a hit!

Originally Posted by wetwarev7

I don't know why this stuff confuses me. I aced trig in highschool, but maybe because it was so long ago, and I've never had a real world use for it till now....

I keep telling my kids that this stuff will come in handy. Now I can prove it!

[wetwarev7]

Originally Posted by klh

Lead Angle = Arctan (target speed/torpedo speed)

So if the target is making 12 knots, and you wish to fire a 30 knot T-III electric, then your lead angle is...

Lead Angle = Arctan (12/30) = 21.8 degrees

Ah! now it makes sense!

In school, they had only taught us about static geometric shapes, so there were intersections, but no interceptions. Thanks alot, Cobb County School System!

I was thinking of the angle always being static(10 or 20 degrees). In my head, that translated to.....well, nevermind, This all makes sense now. And I'm gonna tape that little formula to my monitor till I use it enough times to memorize it.


Thanks Klh!

[Quillan]

The reason the lead angle is larger with a slow torpedo is that you're trying to get the torp to impact at as close to a 90° angle as you can manage, for maximum chance of detonation. If you fire when the ship is at 0° to yours, the torpedo will wind up coming from the rear of the ship to some degree, so you fire before the ship reaches the 0° position to allow for this. It takes longer for the slow torpedo to reach the target than the fast one, thus the target ship will go farther in this interval of time, therefore you fire a little sooner.

[Rockin Robbins]

No trig tables! No formulae, please! The essense of a successful attack plan is simplicity. If you require that the captain recalculate the information the TDC already knows, he's just reinventing the wheel, introducing at least one chance for error for every unnecessary component calculation entailed. It's nice to understand the underlying math. It's stupid to actually use it to perform an attack.

Reliable systems have to eliminate every possible step. Each step increases the chance for fatal error to be introduced. Rules of thumb, such as leading by 20º for slow torpedoes and 10º for fast, are simple approximations that take the place of perilous and complicated calculations to eliminate the opportunity for fatal errors to enter the procedure.

With Fast-90 you can change your mind instantly and shoot from another angle with near-perfect accuracy anyway! You have to love a system that lets you do that!

[klh]

Originally Posted by Rockin Robbins

It's nice to understand the underlying math. It's stupid to actually use it to perform an attack.

Certainly the Fast-90 method is an excellent technique and is useful in many situations. With all due respect, however, real U-boat commanders would not have thought it stupid to use trigonometry to achieve a favorable attack position and generate a firing solution. In fact, they had tools to help with exactly that. The most obvious and advanced was, as you mentioned, the TDC or Torpedovorhaltrechner .

There is also evidence that they had available and used trigonometry tables to calculate precise lead angles for intercepting and firing on targets. For example, the instruction manual for the Angriffsscheibe 2 mit Kompaßscheibe (attack disc) mentions that the lead angle is taken from a table ("Vorhalt ... Tabelle") which is undoubtedly a trignometry table relating to the law of sines. While they would not need to use these tools for every attack, they would be well-trained and ready to do so (such as in the case of a damaged TDC, see U.Kdt.Hdb. Part 145).

While rules of thumb are useful (especially for desperation shots), a good U-boat commander would be prepared to use a variety of techniques to generate precise and accurate firing solutions so as not to waste a single precious torpedo (see U.Kdt.Hdb. Parts 91, 105).

[Rockin Robbins]

As you said, they did not haul out the trig tables and a notebook and work out the calculations. They used the calculators built into the TDC and Angriffsscheibe to perform these calculations exactly as I have described. Therefore they DID agree that it would be stupid to actually work out the trig equations while doing an attack.

When you disagree, it is usually considered essential to contradict the point with which you disagree.

What a great find in the tactics manual, well worth repeating!

a good U-boat commander would be prepared to use a variety of techniques to generate precise and accurate firing solutions so as not to waste a single precious torpedo (see U.Kdt.Hdb. Parts 91, 105).

See a fundamental difference between American (most American captains) and German tactics. Where American doctrine was to shoot a spread, usually of four torpedoes, some of which were expected to miss, the Germans, partially forced by their lesser torpedo capacity in Type VII boats, but mostly by their inherent love of precision and efficiency, stressed wasting no shots! Every torpedo was intended to detonate against the side of an enemy ship. I love that thought! Do I EVER look forward to OLC GUI in SH4 and executing exactly this plan! I'm a rebel in the American Navy, never fire spreads and believe in Eugene Fluckey's "one torpedo, one ship" doctrine. He also believed every torpedo should hit the target.

Do you have English translations of the Handbook you linked to, and do you have the U.Kdt.Hdb as well? I'm foaming at the mouth in anticipation here.

Their table mentioned was similar to a table that gutted made for SH3, showing columns for torpedo speeds, rows for target speed and an array of lead angles. I reproduce an adaptation for American steam torpedoes:



Of course all captains, American and German were trained in the actual trigonometic equations used during an attack. If they were absolutely forced to, they might even have had to use them. I haven't seen a single instance of that happening in the American boats.





Run for your life! That's just a small part of the section on derivation of the trig behind the working of the Position Keeper. Obviously, there is no intent for a captain to actually work these formulae. He only learned them to understand and appreciate all the PK did.

[dcb]

I just noticed something that puts the whole uboat targeting into a new light. I think the German TDC/stadimeter calculations are completely off-course. The distance to target found using the TDC's stadimeter is largely different from the one measured on map.
I made an ideal-scenario mission, with 5 various ships, the uboat at P-depth at 2500 meters from them and used the stadimeter, while at the same time I measured the distances on map, with map contacts on. The differences between stadimeter and map go as far as 1000 meters, at a distance of 2500 meters, which gives a 30% error!!!!!
I think this is why so many torps are missing.
Can someone confirm my findings, or did I go wrong somewhere?

[klh]

Originally Posted by Rockin Robbins

I'm a rebel in the American Navy, never fire spreads and believe in Eugene Fluckey's "one torpedo, one ship" doctrine. He also believed every torpedo should hit the target.

Kriegsmarine doctrine also included firing multiple torpedoes at a target based on the motto "better to destroy little than to damage much." But as you said, the expectation is that every eel hits (at least for short range shots).

U.Kdt.Hdb.
171.) As far as the supply of torpedoes allows, several shots, in the form of multiple discharges (double or three-fold discharges) should be directed against worthwhile targets, even at short range, and when the data (calculations) are not in doubt. In this case, all the torpedoes should hit the mark, in order to ensure the annihilation of the enemy. This means that the torpedoes should be fired at different parts of the target.

Originally Posted by Rockin Robbins

Do you have English translations of the Handbook you linked to, and do you have the U.Kdt.Hdb as well? I'm foaming at the mouth in anticipation here.

The English translation of the 1943 U.Kdt.Hdb. is available here...

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

[Rockin Robbins]

Originally Posted by klh

The English translation of the 1943 U.Kdt.Hdb. is available here...

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

Thank you klh! Now I REALLY feel like a kid waiting for Christmas!

Isn't it interesting that I find the German and American torpedoes about equally effective so far as explosive power goes. I always begin the attack by firing one fish a quarter length back of the bow, then a quarter of the way forward of the stern. Technically this is a spread, but I expect two hits on individually aimed parts of my target.

There are two reasons for shooting the bow first. First, the motion of the ship will tend to make it take on more water. Secondly, once the target is hit there, it will tend to slow down. That will only affect the next torpedo by making it hit further forward than aimed. If the shots were reversed, the tendency would be for the second shot to miss ahead.

Originally Posted by dcb

I think the German TDC/stadimeter calculations are completely off-course. The distance to target found using the TDC's stadimeter is largely different from the one measured on map.

Bang! Zoom! Stadimeters are for use when you cannot use any other method. Then you must learn how to use them to know when you are using them wrongly to get a bad range. The American stadimeter is the same. Let me just say the stadimeter works perfectly, the captain somewhat less so. That includes myself. I will use a stadimeter and I am not bad at it. If I have an alternative, I will choose not to use it. Please read:

Originally Posted by klh

a good U-boat commander would be prepared to use a variety of techniques to generate precise and accurate firing solutions so as not to waste a single precious torpedo (see U.Kdt.Hdb. Parts 91, 105).

Then go find my seminar and instruction set for the Dick O'Kane targeting method. You'll see that klh and I are in agreement. The bigger and more varied your bag of tricks the more successful you will be. No tactic is supreme. Each fits a certain set of circumstances well and should be used then.

Learn Fast-90, Dick O'Kane, down the throat, up the poop chute, conventional 4 parameter targeting (has to be a name for that) and anything else you can come across. I don't know if Cutie on a Leash can be adapted to U-Boats or not, but that's my next project. AFTER I read those great German tactics manuals!

[Ducimus]

RE Salvos.

Since duds were virtually non existant in SH3, i typically fired 2 shot salvos. If it didnt sink the target, it slowed it down enough where i could catch it, and look to employ the deck gun. (that and you only had a 4 tubes forward to begin with, and even numbers are nice)


In Sh4, i fire in 3 shot salvos, for the same reason, but also because duds are much more likely.

If its a target where i dont think ill be able to catch up with it again - for whatever reason), ill shoot a 4 shot salvo. (troop transport for example).

Obviously, a choice warship target gets all 6 from the bow.

Point being, if i shot just 1 fish per target, i dont think ill be sinking much. The 1 fish will most likely be a dud or deep runner.

[klh]

Originally Posted by Ducimus

Point being, if i shot just 1 fish per target, i dont think ill be sinking much. The 1 fish will most likely be a dud or deep runner.

I second Ducimus' point. In SH3 and SH4 we are spoiled in that there are plenty of targets. In reality, when skippers found a good target, correct doctrine was to be sure of hitting and destroying it.

[Rockin Robbins]

I third Ducimus' point. Put 'em down. Millions of homeless fishies are looking for places to live. I certainly don't want to go on record being understood that I said put two torpedoes in 'em and let 'em go.

They do bad things to Captains who do that.

Just inserted the lead angle table for American steam torpedoes in my above post. It's worth a look.

[Ducimus]

I read somewhere, a typical salvo from Tang was 4 fish. I guess O'kane wanted to be dead certain.

[Rockin Robbins]

Originally Posted by dcb

I just noticed something that puts the whole uboat targeting into a new light. I think the German TDC/stadimeter calculations are completely off-course. The distance to target found using the TDC's stadimeter is largely different from the one measured on map.
I made an ideal-scenario mission, with 5 various ships, the uboat at P-depth at 2500 meters from them and used the stadimeter, while at the same time I measured the distances on map, with map contacts on. The differences between stadimeter and map go as far as 1000 meters, at a distance of 2500 meters, which gives a 30% error!!!!!
I think this is why so many torps are missing.
Can someone confirm my findings, or did I go wrong somewhere?

Also, dcb, the stadimeter method of measuring range assumes that you know the real height of that mast! Guess what? Much of the time the information was not correct. Why?

1. Inaccurate information could be "supplied" by the target's owner. That would make your stadimeter tell you the wrong range even if you were perfectly using it!

2. Masts were altered to have a different height than that published with the same result--a clean miss!

3. Masts were painted in such a way that their height could not be determined. Another miss!

Capn Scurvy has determined that many mast heights are wrong in the SH4 database, resulting in inaccurate ranges. This is a reflection of real life, even if they are caused by error. Game error simulating real life error would be strangely appropriate!:rotfl:

There is a reason why I use the stadimeter when I am forced to. There are other attack methods that do not depend on precise range being known. When they are appropriate to the circumstances, they are much more accurate. Use the Dick O'Kane (with U-Boat or fleet boat) method or Fast-90 (with U-Boat only) and see torpedoes hit your target within 5 meters of where you aim each individual torpedo. They are awesome methods!

I go with klh on that one, Duci. Two fish and they stop or slow down. Check it out and see if they want more. With big warships they get the whole front six from the fleet boat and the anemic four from the U-Boat.