John P. Cromwell attack technique on order

[Nisgeis]

Originally Posted by Joe S

Back in the days of Sub Battle Simulator, I used a manual plot and the following forumula for a firing solution: Range to track, at point of torpedo hit, divided by torpedo speed, equals torpedo run time to target. Run time to target X Target speed = distance travelled by target during torp run. plot the distance travelled by target back along its track from the point of impact and when the target gets to that spot you fire the torpedo It really doesnt matter what the aob is . It seems like this Cromwell method is based on the same idea. Based on my experience with Sub Battle Simulator (we're talking hundreds of hours) , I know it is a good method.My question is, what is the importance of the 45 AOB? I really dont think it makes any difference, except that the smaller the angle the smaller the profile of the target at the point of impact. The video and written instructions are great, good job! Joe S

Hi Joe S,

45 degrees is just a point at which the target's lengt is about 75% of what it would be broadside, but you also get the added advantage that 70% of the target's speed gets added to the closing speed of your torpedo, which is a big help. The 45 degrees works even better if you use a spread from aft to bow, as all the torpedoes arrive at the same time.

You can use this method though to attack any angle you want, even from behind.

Thanks for saying about that method you use and yes, it's essentially the same procedure you used to use on Sub Battle Simulator (sounds great :-). The only slight difference is, this is slightly simplified. All we need to find is the ratio between the two closing distances. For that, where you are using distance target travelled, versus distance torpedo travelled, we are taking that equation and simplifying it just a bit.

We are trying to find the angle formed by the two distances travelled, prior to collision for an unspecified unit of time. Your method of using distance travelled by target and distance travelled by the torpedo is great and will give you the correct answer. We can simplify that a bit though, as speed = distance * time for both target distance travelled and torpedo distance travelled, then we can say that the time component of each equation is the same. So, we can substitute it for a value of one. Thus the ratio between distances travelled becomes the ratio between speeds. That simplifies things a bit, as we don't have to work out how far things have travelled, only how fast .

Do you still use this method? If so, does it still serve you well?

[Nisgeis]

[quote=Munchausen]After thinking about it awhile, I realized this method can be done at any angle, without using the TDC at all ... but (I think) I did it bass-ackwards. Here's what I did, using RR's single mission scenario.

<SNIP Excellent Tutorial>

So, was that bass-ackwards or what?[/quote

Munchausen, that was a brilliant example. You even measured the angles to the ends for extra accuracy . That's exactly how it's meant to be.

For those that have asked why use the TDC, the answer is you don't have to at all, but if you do put AoB and the bearing into the TDC and ask it what it thinks, it should say zero gyro angle, if it doesn't then you've done something wrong - probably either drawn with the wrong torpedo speed, or you haven't selected the right torpedo speed in the torpedo panel. It may be useful as a double checking aid. It's a bit trickier to work out the AoB in your head, but it's just 180 - target and torpedo intersection angle - the bearing your drawing gives you. That's based on a bit of maths that says all angles in a triangle add up to 180 degrees, so if you know the intersection angle (angle 1) and the bearing you shoot at (angle 2) then the AoB (angle 3) must be (180 - angle 1) - angle 2.

There's only one thing I can add to that Munchausen and that's you could try using the plot navigation course tool to plot your course beyond the target's track. That way you will be able to measure from that, instead of having to draw it.

You can use this method for any attack angle and drawing the speeds over the setup the way you have done really does simplify things, with the use of the course plotting tool, excellent addition! Thanks for taking the time to post that Munchausen! Every bit of discussion helps to generate new ideas. Fantsatic.

[Nisgeis]

OK, I promise to stop spamming now.

[peabody]

One question, should the time be 3 minutes 15 seconds for Imperial? I am getting the wrong speeds. I peeked in mission editor after missing several times. It works but the tanker in the posted single mission keeps turning and the fish go right by him.

Peabody

[doulos05]

Originally Posted by peabody

One question, should the time be 3 minutes 15 seconds for Imperial? I am getting the wrong speeds. I peeked in mission editor after missing several times. It works but the tanker in the posted single mission keeps turning and the fish go right by him.

Peabody

3 Minutes for Imperial, 3m15s for Metric. It works because...

If you wanted to count the herd by counting the legs and dividing by 4, you could measure 3 minutes (we'll call that d), multipy that by 20 (to get yards/hour) and divide that by 2000(to get knots).
Knots = (d*20)/2000.
Of course, if you're a good mathematician, you say "Wait, we can simplify that!" It simplifies to Knots = d/100.

I'm not familiar with the metric knot, so I can't show you exactly why 3m15s works. But it's the same principle at work.

[Rockin Robbins]

Originally Posted by peabody

One question, should the time be 3 minutes 15 seconds for Imperial? I am getting the wrong speeds. I peeked in mission editor after missing several times. It works but the tanker in the posted single mission keeps turning and the fish go right by him.

Peabody

You think it's an accident that the demo movie is in a driving rain?

With a longitudinal spread, turning into the attack is a very simple way to avoid because the topedoes all take the same track to the target. Later, when we crank up the PK and shoot the stern, MOT, bow divergent spread, the torpedoes run side by side to the target and life isn't so easy for Mr Tanker.

A weakness of the John P Cromwell attack is that he's only 45º from the bearing of the torpedo. He's already halfway into the turn to avoid. Electric torpedoes or night/bad weather shots are good here.

[Rockin Robbins]

Originally Posted by doulos05

3 Minutes for Imperial, 3m15s for Metric. It works because...

If you wanted to count the herd by counting the legs and dividing by 4, you could measure 3 minutes (we'll call that d), multipy that by 20 (to get yards/hour) and divide that by 2000(to get knots).
Knots = (d*20)/2000.
Of course, if you're a good mathematician, you say "Wait, we can simplify that!" It simplifies to Knots = d/100.

I'm not familiar with the metric knot, so I can't show you exactly why 3m15s works. But it's the same principle at work.

There is no metric knot. Those crazy Europeans, knowing the imperial system is so superior, cannot resist using the knot, because like all imperial measurements it actually relates to something useful (in this case, the circumference of the earth and the number of nautical miles (another more useful imperial unit!) in of one degree of latitude). Kilometers per hour, on the other hand, is so unusually useless, even for a metric unit(!), that they have discarded it in favor of something that actually works for navigation. Imagine that! Using the knot is their one consession to sanity.:rotfl:

3:15 works for metric because the yard is 36" long, the meter is 39.37". It is longer, so you need a longer time to measure it. 3:00/36 =3:15/39.37.

[peabody]

I'll double check, I may have had it set to metric because of the JP campaign, but I was getting incorrect speeds on the tanker. So it is probably my fault. I just remember on another thread one was 3min one was 3min15sec, I just didn't remember which and I did get the correct speed using 3min15sec.

Thanks for the answer.

Peabody

[Pisces]

Originally Posted by Rockin Robbins

(other quotes snipped)


There is no metric knot. Those crazy Europeans, knowing the imperial system is so superior, cannot resist using the knot, because like all imperial measurements it actually relates to something useful (in this case, the circumference of the earth and the number of nautical miles (another more useful imperial unit!)in of one degree of latitude). Kilometers per hour, on the other hand, is so unusually useless, even for a metric unit(!), that they have discarded it in favor of something that actually works for navigation. Imagine that! Using the knot is their one consession to sanity.:rotfl:

3:15 works for metric because the yard is 36" long, the meter is 39.37". It is longer, so you need a longer time to measure it. 3:00/36 =3:15/39.37.

Actualy the 'naut and (kilo)meter is based on the exact same baseline( 1 quarter of the the pole-equator circumference), just each a different division. Naut's follow the degree-minute division. A kilometer is defined to be one 10,000th of that quarter circle. Or more correctly a meter is one 10 millionth of the quarter-'circle'. Apples and oranges... are both spherical.

3 minutes 15 seconds works because 3600 seconds (1 hour) divided by 18.52 (# of times 100 meters go into a nautical mile) is 194.38 seconds. Rounded to an easy measure that is 3min 15sec.

[doulos05]

[quote=Pisces]

Originally Posted by Rockin Robbins

(other quotes snipped)
3 minutes 15 seconds works because 3600 seconds (1 hour) divided by 18.52 (# of times 100 meters go into a nautical mile) is 194.38 seconds. Rounded to an easy measure that is 3min 15sec.

Right, I knew there was some sort of mathy ratio behind it, I just couldn't recall what it was. Thanks guys!

[Rockin Robbins]

Originally Posted by Pisces

Actualy the 'naut and (kilo)meter is based on the exact same baseline( 1 quarter of the the pole-equator circumference), just each a different division. Naut's follow the degree-minute division. A kilometer is defined to be one 10,000th of that quarter circle. Or more correctly a meter is one 10 millionth of the quarter-'circle'. Apples and oranges... are both spherical.

3 minutes 15 seconds works because 3600 seconds (1 hour) divided by 18.52 (# of times 100 meters go into a nautical mile) is 194.38 seconds. Rounded to an easy measure that is 3min 15sec.

And that's all fine and good but the Frenchies screwed the pooch (technical term there) and got their measurement way off. The meter ended up having no relationship to the size of the earth at all and now is just a bunch of bars of metal of varying lengths themselves, sitting in various places. They spent lots of time deciding (that means fighting about) which one was the "authentic" meter (who cares? They got it WRONG to begin with:rotfl::rotfl and then redefined the meter as a number of wavelengths of a certain frequency of light. THAT'll fix 'em!

So the entire metric system is based on a surveying mistake! Somehow that is very appropriate. Perhaps it's relationship to human error is the most appropriate measurement of all!

[Munchausen]

Originally Posted by Nisgeis

There's only one thing I can add to that Munchausen and that's you could try using the plot navigation course tool to plot your course beyond the target's track. That way you will be able to measure from that, instead of having to draw it.

I did that yesterday when demonstrating the technique to my daughter's boyfriend. Using the "plot course" tool, the trick is to let your sub turn until rudder is centered ... then you can draw your "hypothetical" triangle and get the offset (lead) angle without even measuring your own course ('cause the tool's line is your sub's course line). You can even continue to close on the target's track ... just so long as you don't change course.

This is certainly the way to go if your TDC is broken ... or you're the skipper of a WWI U-Boat.

[blackbob]

Hi all i have just started with manual targeting with the excellent Dick O Kane method and i've had some fair success so far and i am keen to try this new one but one thing i've a problem with is getting accurate speed estimates my nav map dividers measure in tenths of nautical miles rather than yards and this throws me a bit is this a setting or a mod that i need to get yards ?

[Nisgeis]

Hi BlackBob, welcome aboard! The only reason I can think of for having measurements in tenths of a nautical mile, is if the distance is over 10,000 yards (or 5 nautical miles). Up until that distance, the measurements are in 100s of yards, up to 10,000 yards, over 10,000 yards, the measurments are in tenths of nautical miles.

[blackbob]

Thanks Nisgeis but even if i zoom in the units remain the same i can measure down to 0.1nm i've just realised that i am only patched to 1.3 could that have any bearing (sorry terrible pun)