Adjusting the contrast for the Stadimeter

[Platapus]

It really should be written Angle of the Bow

So you telling me that my AoB is not just the reciprocal of my bearing?

<ducking and hiding>

I actually did that when I started in sub sims. I can't remember which one first introduced AoB but I quickly found out the error is my ways

[Munchausen]

Originally Posted by Platapus

So you telling me that my AoB is not just the reciprocal of my bearing?

Actually, it's not AoB you need to worry about ... exactly. It's target track. With the O'Kane method, you want the target to cross your bow with an AoB of 90 degrees. The easiest way to do that is to position you sub perpendicular to the target's track (course line).

If you "pull lead" to optimise your gyro angle, you need to take care that you don't, at the same time, skew the AoB (check target heading on the TDC to be sure) . Whether you align your crosshairs with your bow or adjust them to lead the target, the target still needs to be at 90 AoB when it crosses your bow. (With a proper lead, you will fire prior to the target crossing your bow such that the torpedo impacts the target exactly as it crosses.)

[Nisgeis]

Originally Posted by Munchausen

Remembering that AoB is relative to the bow of your submarine. Not to the gyro (lead) angle of your fish.

AoB is a bit of a tough one to get your head around. I struggled for a while with it, mainly due to all the examples having a ship sailing directly towards or away from you, so the AoB doesn't change. AoB is relative to the bow of your target. If you were standing on the target ship, looking dead ahead at the bow, then however many degrees you would have to turn left or right to see your submarine is the AoB.

The reciprocal of your own bearing is the bearing from the target to you.

If you were sat stationary, pointing north and your target were directly ahead of you on a relative bearing of 000 and sailing NE, then the AoB would be 135 degrees to starboard. If the ship were due west of you and was sailing south, the relative bearing would be 270 and the AoB would be 90 degrees to port.

If you have two of the three pieces of info, target true bearing, target AobB and target course then you can work out the missing one.

[Rockin Robbins]

Angle on the bow is easy. It's a point of view problem, that's all. Just step off your submarine! You're just on the wrong boat.....ship.....vessel.....whatever.

Angle on the bow is your bearing from the target! The only thing different is that it is counted from zero at the bow to 180 on the stern and then starboard or port is attached, depending on which side the bearing is on.

[Munchausen]

Originally Posted by Munchausen

Remembering that AoB is relative to the bow of your submarine. Not to the gyro (lead) angle of your fish.

What I meant to say was, using the O'Kane attack method, your 90-degree AoB is relative to the bow of your sub. If you make an input to the TDC with your crosshairs offset from the sub's bow, make sure you also adjust AoB to compensate ... otherwise your 90-degree AoB will be relative to your offset bearing. And your attack geometry will be skewed.

[Fincuan]

Originally Posted by Munchausen

What I meant to say was, using the O'Kane attack method, your 90-degree AoB is relative to the bow of your sub. If you make an input to the TDC with your crosshairs offset from the sub's bow, make sure you also adjust AoB to compensate ... otherwise your 90-degree AoB will be relative to your offset bearing. And your attack geometry will be skewed.

Actually it's just your periscope that must point to where the targets AOB will be 90 degrees, but to simplify things(allowing you to pretty much ignore range among other things) players usually point the whole submarine towards that point. Skippers who are familiar with the "Fast 90" attack method know exactly what I mean. This method of targeting works exactly as advertised on the SH4 U-boat TDC, and can easily be adapted to the US TDC(the already mentioned Dick O'Kane method).

Wazoo's great "Fast 90" tutorial:
http://www.paulwasserman.net/SHIII/

[Munchausen]

Originally Posted by Fincuan

Actually it's just your periscope that must point to where the targets AOB will be 90 degrees....

:hmm: Yeah, I suppose you could do it that way. But, if you did, you'd need to set up the TDC so that "90 degrees AoB" was relative* to the crosshairs (and not to your sub). Doing it that way, though, would make it harder to lead the target (assuming you're setting up for an optimum torpedo run).

With the bow as a 90-degree reference point, you can use the crosshairs to adjust for lead. With the crosshairs as a reference point ... how do you lead the target?

Admittedly, I can see where your method would come in handy. For instance, a running surface attack on numerous targets. As soon as you judge yourself to be broadside of your current target, you take a bearing and shoot. As long as you've already set the AoB meter for 90 degrees (starboard or port, as required), any bearing sent to the TDC should give the torpedo a correct gyro angle.

* Again, not meaning to imply that AoB is, itself, relative to the sub.

[Platapus]

Rockin Robbins,

I have been using the 90 AoB targeting system that you described.

I still don't understand it
I still think it is magic
I still think that you are probably BSing me

But I AM putting holes in the floaty things without having to ID the ship or take a single range reading.

I don't know why it works and I probably don't have a need to know why it works

But it works, the floaty things have holes in them and I am having fun

This old dog at least learned to fake a new trick anyway

Thanks

[Rockin Robbins]

Originally Posted by Platapus

Rockin Robbins,

I have been using the 90 AoB targeting system that you described.

I still don't understand it
I still think it is magic
I still think that you are probably BSing me

But I AM putting holes in the floaty things without having to ID the ship or take a single range reading.

I don't know why it works and I probably don't have a need to know why it works

But it works, the floaty things have holes in them and I am having fun

This old dog at least learned to fake a new trick anyway

Thanks

:rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl: :rotfl:

[jazman]

Here are a couple of images that document the math needed to understand. Part I shows the geometry, part II steps through the math. I can't help you if you don't understand Trigonometry, that requires a course.





You don't need the range X. It doesn't matter, if you have the speed of the ship correct and you really are at AoB of 90 degrees. And if your torpedo goes at the rated speed.

(In reality range does matter, because there is a curve in the torpedo's path, unless you have the sub pointed down the torpedo track.)

[Platapus]

Originally Posted by jazman

Here are a couple of images that document the math needed to understand. Part I shows the geometry, part II steps through the math. I can't help you if you don't understand Trigonometry, that requires a course.

AAAiiieee! It burns the eyes... I can't see. The pain..... the horrible pain!!!!! Make it stop AAAHhhhhhhhhh

[bos]

This can be improved for a perfect zero gyro and 90 degree impact shot with the following method.

#1) Get the targets speed. With map updates on, the 3 minute method works fine.
#2) Plot the target's course and position your boat exactly 90 degrees to that course.
#3) Input whatever you want for the range via the stadimeter. Max range works fine.

#4) Input the AoB as Arctan(torpedo speed / target speed). For instance, it is about 76.5 degrees for a 46 kt torpedo against an 11 kt target. Depending on the level of authenticity you desire, you can use a trig slide-rule, scientific calculator, or a google search for arctan(46/11) in degrees or whatever. It should be somewhere in the ballpark of 65 to 85 degrees. You could even draw a right triangle of 460 yards by 110 yards or whatever and measure the angle with the protractor tool.

#5) Try various periscope positions until you get one where the torpedo gyro angle reads exactly 0 degrees. Or do the opposite arctan (e.g. arctan(11/46)) to find how many degrees off your bow is the perfect shot.
#6) Wait
#7) Wait some more.
#8) As the target approaches your periscope centerline, open the tubes. Double-check that the torpedo gyro still reads 0, adjust periscope as needed.
#9) Fire as the target crosses the periscope line. The line is where on the target the torpedo will hit.

Alternatively, if you don't care about hitting specific points on the target, you can just lock it and fire when the gyro hits zero.

[Platapus]

Rockin Robbins,

I have one more question on your instructions in your thread.
http://www.subsim.com/radioroom/show...6&postcount=67

Step 4 1/2 Set your AoB. It will be 90 degrees minus our shooting angle from zero, which is 10 degrees in this case.

where did the 10 Degrees come from? Is this a constant or was I supposed to have calculated this from some observation?

I understand that later in step 5 we will "lead" the scope 10 degrees for a fast speed torpedo but I think the 10 degrees you mention in step 4 1/2 is talking about a different "10 degrees"

[Munchausen]

Originally Posted by Platapus

I think the 10 degrees you mention in step 4 1/2 is talking about a different "10 degrees"

Robbins can (and will, I suspect) correct me if I'm wrong, but the "10 degrees" should be the same. It assumes a setup where your sub is perpendicular to the target's track (heading/course line). Step 4 1/2 was added because, otherwise, the TDC would assume the target reaches an AoB of 90 degrees at the shooting (lead) angle instead of at the point where it crosses the bow of your sub.

You can check the geometry yourself. With crosshairs centered on the bow of your sub and max range set into the stadimeter, set the AoB for a false "target" to 90 degrees. Then send AoB and range to the TDC. Target and sub should be perpendicular to one another. Then send a target speed to the TDC and watch how the torpedo gyro angle (arrow on the bottom wheel) changes. Now adjust the crosshairs by 10 degrees and, without changing AoB, send another bearing to the TDC.

Notice how the geometry has changed ... the target is no longer on the correct heading. If you activate PK and go to the attack map, you can watch your "target" as it sails past your sub. It no longer crosses the sub's bow with a 90 degree AoB.

Now do the setup again. This time, though, add in the AoB correction of step 4 1/2. The TDC should now show a correct heading for your target. And, with PK running, the target should cross the sub's bow at 90 degrees.

[Rockin Robbins]

Originally Posted by Platapus

Rockin Robbins,

I have one more question on your instructions in your thread.
http://www.subsim.com/radioroom/show...6&postcount=67

Step 4 1/2 Set your AoB. It will be 90 degrees minus our shooting angle from zero, which is 10 degrees in this case.

where did the 10 Degrees come from? Is this a constant or was I supposed to have calculated this from some observation?

I understand that later in step 5 we will "lead" the scope 10 degrees for a fast speed torpedo but I think the 10 degrees you mention in step 4 1/2 is talking about a different "10 degrees"

Nope, it's the same 10º lead angle I'm talking about. I'm nowhere near fussy enough to pull out my scientific calculator and figure out the exact lead angle to get a perfect 90º impact. If it's even 10º off, that's a perfect shot!

Actually you can figure the perfect lead angle out using the high precision angle computer built into the boat--your TDC. Set your speed in the TDC for the speed of the target. Set AoB to 90º port or starboard, take your pick based on your real target. Hope you have your 360º bearing plotter mod loaded! Now point the periscope at zero and press the send range/bearing button.

Now switch to the attack screen. See the torpedo track doesn't go out at zero degrees! It is off one side or another at your perfect lead angle for a 90º impact! I'm not going to do it because, like I said, it really isn't worth the trouble. But let's pretend it is pointed at 7½º. That means the target is coming from left to right. Our lead angle will be 7½º, so set the periscope at 360-7½ = 352½º. We will set our AoB based on our shoot angle: 90 - 7½ = 82½º starboard. Point the scope at 352½º and shoot as nice parts of the ship pass the crosshairs. No fancy trig necessary.

Now, was that all worth it? No. I just shoot with a lead angle of 10º for fast torpedoes and 20º for slow torpedoes with a medium speed target. Add 10º to the lead angle for a target going 17 knots or above. If you forget, not big deal. A 90º boom sounds pretty much like a 345º or a 15º boom anyway. (is 60º of allowable slop enough to make you comfortable?) In the seminar part of the Dick O'Kane tutorial I got excited and shot over 10º before I should have with resulting AoB error and still hit right where I aimed. There are huge allowances for error in every parameter but target speed in the Dick O'Kane technique and that is why it works so well. And that is why the Germans had such a great hit percentage in spite of not having as fancy a TDC as Americans.

It's amazing how you can learn that playing "silly games" and not understand it after reading dozens of history books. Who says simulation has no value! They teach insights not possible with any other medium.

Remember: keep the blasted PK off! And take a sledge hammer to your stadimeter!(Hate that thing:rotfl