John P. Cromwell attack technique on order

[Munchausen]

Originally Posted by I'm goin' down

I do not think the fish passed under the keel because they were set 5 feet above its draft.

Prior to the official fix, rule of thumb decreed that a torpedo generally ran ten to eleven feet deeper than its setting.

Besides depth, you need to set a torpedo's speed. What setting did you use (fast?) ... and what speed did you use (46 knots?) for calculating your attack geometry?

[I'm goin' down]

Is the lead angle of 11 degrees in RR's tutorial dependent on the speed of the approaching target? Is the same if the target is doing 10 kts. versus 12 kts? If so, I guess you vector it like RR did in his tutorial? Manhausen, I am not sure what geometry you are talking about, plus I am no math wizard.

I am not sure what geometry you are talking about

Have you read all 3 pages of this thread? Especially nisgeis and munchausen

Urge

[I'm goin' down]

I have read them all. But I must be confused on the concept. Plus, it is an exhausting read. If you have the answer to my post, rather than trying to give me an assignment, please answer the question if you know it. No one has answered it yet.

I think that if a target is doing 9 kts., for example, the lead angle is the angle generated by a track of 900 yds. ending at the 45 degree bearing (i.e. the "0" bearing where I will aim torpedoes.) If it doing 12 kts. then the lead angle is the angle generated by a track of 1200 yds. ending at the 45 degree bearing. And so on.... The faster the target is moving, the larger the lead angle. And vice-versa.

The next issue is how does the speed of the torpedo affect the lead angle. I have seen posts regarding that, and I will review them.

Where is this track? It is on the target's projected course.

If this is correct I need confirmation so I can rest in peace. Once I have the procedure down, I can use it and try to understand the theory while I see it working.

[Nisgeis]

Originally Posted by I'm goin' down

I think that if a target is doing 9 kts., for example, the lead angle is the angle generated by a track of 900 yds. ending at the 45 degree bearing (i.e. the "0" bearing where I will aim torpedoes.) If it doing 12 kts. then the lead angle is the angle generated by a track of 1200 yds. ending at the 45 degree bearing. And so on.... The faster the target is moving, the larger the lead angle. And vice-versa.

Absolutely right.

Originally Posted by I'm goin' down

The next issue is how does the speed of the torpedo affect the lead angle. I have seen posts regarding that, and I will review them.

The speed of the torpedo affects the drawing the same way the target speed does, so when you draw your two lines, one lines is the target's course, where you draw 1200 for 12 kts as you say. The other line represents the torpedo and the length of that is the torpedo speed * 100, so if the topedo runs at 32 kts, then the line is 3200 feet. Another example, for a target of 20 knots and a torpedo of 44 knots, the target line is 2000 feet long and the torpedo line is 4400 feet long. The relationship is that when the target has travelled 2000 feet, the topedo has run 4400 feet, so drawing it out is a way to see where ther start points were.

Originally Posted by I'm goin' down

Where is this track? It is on the target's projected course.

Yes that's right.

Originally Posted by I'm goin' down

If this is correct I need confirmation so I can rest in peace. Once I have the procedure down, I can use it and try to understand the theory while I see it working.

You have it exactly right. The drawing is only to see where the 'start' point is for when the torpedo and target will collide, so, imagine the point where the lines cross being the point where the torpedo has hit the target and then 'rewind' time. Rewind it to a point where a 20 kt target was 2000 feet ahead of the impact point and the other line you have drawn for the 4400 feet for the 44kt torpedo is the point at which the torpedo would need to be fired from in order for the torpedo and ship to collide. You just need to draw the torpedo's line back along the course it was on.

[Munchausen]

Originally Posted by I'm goin' down

The next issue is how does the speed of the torpedo affect the lead angle.

Where is this track? It is on the target's projected course.

If you mean the track of the torpedo, then no. It's actually along your sub's projected course ... making up one side of the triangle.


A second side of the triangle corresponds to target speed ... it's along the target's course line. The two sides intersect at the point where target track and submarine track meet.


The third side of the triangle is a line drawn between the ends of the non-intersecting sides. The angle between the third side and sub's course line is the angle (bearing) you use when setting up your crosshairs.


The angle between the third side and target's course line is your AOB.

[I'm goin' down]

I am almost there. Nisgeis and Manchusen (I should have anticipated that Manchusen would drop a screen shot display to answer my question [How can the Japanese possibly compete with likes of these guys?]. They are off in "billiant" land again.

Two questions left. I understand how the Cromwell attack works if my boat is not moving.

(1) What if it is moving? Then the distance the torpedeos travel along the lead angle shortens as my boat my boat approaches the target's course.

And, a related question (actually, a subpart of the first question.)
(2) Does this movement have to be accounted for in the Cromwell attack? (I do not think the lead angle is changing, and it remains constant, although I might be wrong about that assumption.)

A special thanks to Nisgeis and Manchusen (again!). I find the screen shots used in Manchusen's step by step examples extremely helpful, and NIgeis, my hat is off to your concise, articulate explanations which are superior to the analyses and writings of many lawyers whose work I have reviewed. (Do you guys love me or what?)

"Pass another of those Rockin Robbins' Mai Tai's over here." My crew promised me that I could have three of them before lunch, and I am just about finished with my second one.)

Mai Tai in hand, I glance at Rockin Robbin's tutorial as supplemented by Manchusen's and Nigeis' posts, and turn on the ship's intercom:

"OKAY BOYS, LET'S HUNT SOME MEAT."

[Nisgeis]

Originally Posted by I'm goin' down

(1) What if it is moving? Then the distance the torpedeos travel along the lead angle shortens as my boat my boat approaches the target's course.

It doesn't matter if you are moving. As long as both your target's course and your course intersect at some point. The drawing you are using is to work out the relationship between two lengths. In your example of 1200 feet, that represents 12 kts and a torpedo at 44kt with a length of 4400 feet, then this will give you an angle. That's the relationship between the two speeds. If you double the range or halve it, you will still get the same angle - try it and see.

Why is this relevant? Well, because the run length of the torpedo doesn't matter, it doesn't matter how fast you go, or how far you travel towards the target's track, as the ratio is fixed. As long as you have got the course correct, range doesn't matter. Of course it does matter a bit at very long ranges, from the point of view of you can't set fractions of angle on the periscope.

The angle is basically the place you look at that, where it intersects the target's course, is the point at which if you were to fire, anything at that point where you are looking at that moment in time would reach the intersection point of the projected course and the torpedo, at the same time as the torepedo is there. Your aiming point is continuously moving down the target's course and when the target reaches the point along its course where you are looking, then any torpedo fired will impact. Sop, both your aiming point and the target move down the track. It would be very complicated to work out when the aiming point and the target will be the same point, but lucky we don't have to. All we have to do is to wait for it happen.

It's like a continuously calculated firing point, except all the calculations are done. Your range to the target's track is reducing and his range to your track is reducing. It's all been taken care of, as it doesn't matter at what range you fire, you'll know when it's the right time when the target crosses the wire.

Originally Posted by I'm goin' down

And, a related question (actually, a subpart of the first question.)
(2) Does this movement have to be accounted for in the Cromwell attack? (I do not think the lead angle is changing, and it remains constant, although I might be wrong about that assumption.)

You can go any speed you like. It's good for submerged creeping and full speed ahead 21 kts on the surface.