Guides and Training

[Frederf]

You know I've been looking at the graph I posted and even half-arse using it in SH4 for a while now but I've always put off applying some greygoo power to it until you splattered against it first.

When I saw deflection angle on the plate I remembered it was back in that previous diagram in the same document about the angle between the periscope and pseudo-winkler-bajoob or something and never bothered to look it up. It turns out the deflection angle is more or less what we've been used to thinking of as the "shoot lead angle" or the angle between the direction to the target visually at the moment of firing and the direction of torpedo travel.

Oddly enough I've been using the concept of "optimal track angle" for ages in Silent Hunter but in a totally different context. I never thought of it as the most error-tolerant or the least rate of change of deflection angle but simply the best chance to hit another ship in a convoy row if I missed the first target.

If you try to hit a convoy target squarely and miss astern there's no chance to hit his neighbor traveling abreast of him. So instead of perfectly abreast of a convoy row I'll skew the shot (or spread) several degrees beyond 90° impact then a miss of the first can hit the second or even third. The improvement in hit percentages is very noticeable! For example if the convoy is going 10 kts I would shoot at a torpedo track angle of ( ArcTan (10/46 ) = 12.3°) 90 + 12.3 = 112.3°.

I had the suspicion but never a firm understanding that when firing in this way not only was I increasing my chances of hitting a 2nd or 3rd target I was actually increasing my chances of hitting the 1st or single target.

Let's check this method vs. the plate and see if they agree.

D'OH WRONG: TORPEDO TRAVELS ALONG THE HYPOTENUSE

ArcTan(8/46)+90° = 99.9°
ArcTan(12/46)+90° = 104.6°
ArcTan(16/46)+90° = 109.2°
ArcTan(20/46)+90° = 113.5°
ArcTan(24/46)+90° = 117.6°

What's with me and Tangent vs Sine lately?

BETTER

ArcSin(8/46)+90° = 100.0°
ArcSin(12/46)+90° = 105.1°
ArcSin(16/46)+90° = 110.4°
ArcSin(20/46)+90° = 115.8°
ArcSin(24/46)+90° = 121.4°

Plate
8kts: 102
12kts: 108
16kts: 111
20kts: 118
24kts: 122

Hmm I was hoping those would come out closer. It's probably just a coincidence that these values are close.

I think of it this way: If you know the enemy's course very, very exactly and know the enemy's speed very, very poorly my best shot is against the target's bow or stern to rule out errors in speed. However if you know the speed very well and the course not so well it's better to shoot into his sides as his ( angular speed ) x ( target angular width) is not so strongly tied to his AoB the closer you get to 90°/270° AoB. Somewhere between these two extremes must be a balance for an equal uncertainty both with speed and course.


This of course all goes out the window because with these darn faulty impact pistols I am habitually shooting from 50-60° torpedo track angle or 120-130° to avoid the square-shot pistol jam dud-amabobber!

[magic452]

@ distortion

To shoot a true vector analysis solution you will have a 0° gyro angle, speed = 0 and AoB = 0 and bearing = 0. The only time you hit the send button is to set these values. A 0 gyro angle will send the torpedo right down your course line. If you move the scope to any bearing other than 0° and hit the send button you will change the gyro angle and therefore the torpedo track.

Once you have your shooting bearings just point the scope to that bearing but don't hit the send button. Fire when the part of the target you want to hit is in the cross hairs. Wait till the second target gets to it's shooting bearing and do the same. The two targets must be very close to each other for this to work, that is why I shot at ships in two different columns at a 60° approach.

I tried to get a single column type of shot off today but no way it would work, too much distance between the targets. By the time I was able to shoot the second ship it had already reacted to the first being hit and changed course and speed.

What I had was a large troop transport (9494 tons) followed by about 200 yards by a DD (2700 tons) and that followed by a very large transport (18765 tons) by some 1,400 yards.

I shot the first ship with a 31 knot vector shot and then just adjusted a few degrees and shot the DD, both sank. For the other transport I just used a position keeper shot as he was slowing and turning, got him also.

Not a bad days work, almost 31,000 tons with only 6 torpedos and not a single DC dropped any were near me, shot from 2800 yards.

As far as sending a different gyro angle to shoot a second ship I don't know how you could plot that out. But it may be worth a look and see if it
can be done. Darn it now you got me thinking and it hurts.

You might be able to do something like that with the O"Kane method but I don't use that so I don't know.

Magic

[TwinStackPete379]

I just did my first O'Kane fast 90 after reading RR's tutorial. out the stern tubes at 2600 yds. that was way cool! both fish hit EXACTLY where i aimed for. that was FUN, I wanna do it again!

[Rockin Robbins]

And there are lots of other factors to be concerned with than just how tolerant of target course errors our solution is. For instance against warships, I believe you want the John P Comwell shot from ahead of the target, because every second you wait to shoot is a second during which they might detect you. When they do, all that beautiful data you've collected is in the garbage and you don't care HOW accurate it was...

Also there's the error mitigating fact that the faster the torpedo's approach speed to the target, the smaller the error radius of the impact point. Using the roughly 110º torpedo track angle, the torpedo is approaching the target from 20º aft of the beam. So from your 46 knot torpedo speed you must subtract some of the speed of the target to get the torpedo approach speed.

Similar to the way speed is added to torpedo speed by the target's approach in the John P Cromwell technique, the approach speed of the torpedo must be reduced by the speed the target is receeding from you at point of impact. Well that is calculated by the cosine of the 110º torpedo track angle, .34 in round figures. So the 31 knot approach speed of the torpedo must be reduced by 34% of a 20 knot target's speed! That leaves the already anemic electric with an approach speed reduced by 6.8 knots! And with a target approached at only 24.2 knots, there is all kinds of time to ruin all your beautiful numbers.

The graph shows a very incomplete view of all the decisions you must make during an attack. I question their usefulness as a practical matter.

[Distortion]

Yesterday I`v been working the hole day with the numbers. the first target is not a problem, can hit it at 1k-2k-3k yards, slow or fast torpedos with the vector analysis attack. I tought it can`t be that hard to hit the second target, witch course and speed it the same than the first one. But it is very complicated, without turning your own sub. Afcourse, when I turn the periscope away from the 0 dergree point and send the new calculation, its not an vector analysis attack anymore, but who cares. If I know course and speed, it can be that hard? How much degree need I for the second target, what is the lead angle, etc.

I have some calculations, and I think I was very close yesterday. Tonight I will try another round, with new ideas (yes, when in bed new ideas came up) based on those calculations, and see what happens.

I do have a problem with the 3000 yards bearing plotter i use, its not for 1680 X 1050, so its off by 1 degree. And this can be a problem at high distances. Anyone here can help me with that? I`v asked this question also here http://www.subsim.com/radioroom/showthread.php?t=132000.

We will continue..., thanks for all the input guys

Robert

[Hitman]

Fantastic explanation RR

On this piece I wanted to add a small comment:

you can alter your course to about 110º from the target track instead of 90º. This will reduce your gyro angles in all reasonable circumstances to less than 5º. I'm not going to worry about it myself.

The manual for the Attack Course finder uses an example to illustrate how it works and do you know what track angle is chosen? Bingo .... 110º

I quote the manual:

5. EXAMPLE: Heading by compass 230 degrees. Enemy relative bearing by periscope 315 degrees. Angle on the enemy's port bow 25 degrees. Estimated range 5000 yards. Desired track angle 110°.

Good proof of how right you got it

[Rockin Robbins]

It was the use of the technical scientific term "gobbledy gook" that did it!

[Frederf]

I think it's rash to discredit any of the graphs or math for not taking in all possible tactical factors. The base assumption in pretty much all of these targeting tools is a contact that will continue to travel in a straight line throughout the attack. O'Kane or Cromwell methods are similarly lacking in their encompassing of all factors.

Another big one is these all assume our ordinance works perfectly which, don't mention this to the Admiral Lockwood, but I'm beginning to have my doubts. All methods are limited by their driving factors. This is the only thing that makes the problems tractable. It is up to the commander to utilize the various methods with the brainglue to bridge all of them together.

I'd like to throw a red flag at this notion that "fastest speed-made-good to target" is somehow the best. A meeting of greater than right angles means a slower effective torpedo speed...boohoo. If torpedo approach speed was such a boon, we'd all be shooting straight down the bow's of targets. I could even argue that the slower torpedo approach speed places the torpedo in close vicinity of the target for longer which should increase the odds of impact. Obviously shortest physical run and endurance are nice things but the balance point between that and other aiming factors likely skews the best combined track angle away from 90.

Practically, my track angle depends on a lot. Due to the problems with the MK14's impact detonator, my TTa windows are currently 50-60 and 120-130. I hear that shallower tracks are better for magnetic detonation too. It's really nice to know what the best TTa's are for perfectly functioning hardware for when I get some more reliable fish. Against convoys I'll most certainly be using a convoy speed-directed TTa as the chance of picking up secondary impacts outweighs first target accuracy.

[magic452]

@ distortion

Good luck with this, it could be very helpful.
I'm working on it as well but from a different track.
I got a couple of ideas I'll try tomorrow.

Magic

[Rockin Robbins]

Originally Posted by Frederf

I'd like to throw a red flag at this notion that "fastest speed-made-good to target" is somehow the best. A meeting of greater than right angles means a slower effective torpedo speed...boohoo.

Perhaps in real life you would be correct, but this is a game in which a target can accelerate from 15 to 30 knots in about five seconds. Shortest time to impact is very important in Silent Hunter 4 compared to real life.

[CaptainJack]

I tried to search this thread, but did not see this question. Sorry if I missed it. I am playing SH4 1.5 with RFB 1.52 and the Easy AOB.

Can we talk range here for a minute when using O'Kane? I've been using this method fairly successfully - I say fairly, because it seems mostly accurate, but I also experience occasions where the torp will run mysteriously just ahead or astern. I get hits, but lots of time not in location where the ship trips the wire when I fire. Sometimes, I will set-up being careful to double-click on AOB and bearing, yet I can tell by arrows on the TDC that that shots will go terribly awry - and they do - mystery

After watching Rockin Robbins tutorial for the 4th time today, I finally noticed something. When he drags his range triangle as far counter-clockwise as possible, his range on TDC goes to about 1240 (IIRC); when I do same, my range on TDC goes to 241 - 1000 yards less, that is not a typo!

OK - so I go back to save game and try something: My range to target is 750 so I drag range triangle until range on TDC is 800 before clicking range and bearing having previously set target speed at 12 and AOB at 75 (target bearing is set at 345). I've tried this shot with mixed results before and the only change now is range setting. Fire four torps - bow crane, 1st funnel, 2nd funnel, stern crane - guess what: four precise hits. Go external and check damage on ship - four precisely spaced holes exactly where I aimed.

Conclusion: perhaps range does matter, and I can't simply drag my range triangle as far counter clock-wise as possible. In fact, playing with range meter, I seem to be able to drag around a max range of 12030 down to 241 - so where that range registers when you drag the triangle to the right seems to be a function of where it started - results will vary wildly. And since the arrows on the TDC will move as range is adusted, it seems to matter. With O'Kane, I am now going to be setting range at least higher than my actual - or maybe just 1000 is the magic number - just not sure. Please tell me what I am missing! Thanks

[Rockin Robbins]

Yup, you're right. You're experiencing an Easy AoB hiccup, where it acts differently from the stock dials I'm using in the tutorial. However you have to do it, entering a range of 1200 yards or so should make the technique deadly accurate for gyro angles of under 30º.

If, for some reason you're shooting at great range or outside the 30º gyro angle it's important to set your range to somewhere in the rough neighborhood of the target range. Several hundred yards plus or minus shouldn't matter much. All the guys who love precision are just cringing right now!

[CaptainJack]

Originally Posted by Rockin Robbins

Yup, you're right. You're experiencing an Easy AoB hiccup, where it acts differently from the stock dials I'm using in the tutorial. However you have to do it, entering a range of 1200 yards or so should make the technique deadly accurate for gyro angles of under 30º.

If, for some reason you're shooting at great range or outside the 30º gyro angle it's important to set your range to somewhere in the rough neighborhood of the target range. Several hundred yards plus or minus shouldn't matter much. All the guys who love precision are just cringing right now!

Thanks - makes sense that it was a mod thing. Thanks too for the advice - I will put it to use. And glad I watched your video again. I wonder how many ships that video has sunk?! Looking forward to better shooting!

[OrangeYoshi]

Rockin Robbins,

Thank you for the videos you make. They are very informational, easy to understand, and possibly most of all, you are fun to listen to! I haven't watched all the other videos I've downloaded yet, but I wanted to stop in and be just one more person to try to tell you how good you are at this stuff, and thank you for all your work.

[Rockin Robbins]

Yeah, when I get the facts all wrong I can always fall back on the entertainment value!

Actually, with the requirements I put on my videos, real time with no time compression, one cut production so you can learn the pacing of the actual attack, complete with dead space and boredom sometimes, "live" production values with no editing afterwards, I'm always worried that they will be too boring and that people will stop watching before they can learn what I'm trying to teach.

I'm glad to learn that isn't always the case.