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Dogger Bank -- and\or Gunnery Mechanics
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jwduquette1



Joined: 20 Dec 2005
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PostPosted: Thu Mar 27, 2008 11:36 am    Post subject: Inclination Vectors? Reply with quote

It sounds like you know exactly what you’re looking at with the plot. So I’ll try another tack. How bout’ I jabber on about what I think I am looking at and maybe you can help me by telling me what I am actually looking at.

It looks to me like a stern chase by Tiger of Renown. Sort of like a Dogger Bank scenario. What I think I am looking at with the inclinations\deflection vectors are angles relative to the bow of Tiger – arrow of vector pointing at Renown. At the bottom of the first plot (frame-19) there is something saying “Mean Inclination Used”. Is this the actual inclination\deflection employed for the specific shoot? Moreover, the actual turret inclination estimate was not used?

Thanks
Jeff
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PostPosted: Thu Mar 27, 2008 1:23 pm    Post subject: Reply with quote

JD ... I haven't looked at the plot yet. I may try to suture together the several images (perspective may make this difficult) before doing so.

I'm not sure I know what you mean by "turret inclination". "Inclination" in a document like this refers to the angle formed between a target and your line of bearing to the target. e.g., an inclination of 0 means he is heading away from you, 90 to the right means you are looking directly over his starboard gunwale, and 180 means he is pointing his bow directly at you.

... as I did this, I have stitched together the big chart into one image, and can post a 3 page PDF of this baby. Can you offer me a complete index designation for it for my records? e.g. ADM 52/18 from TNA ?

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jwduquette1



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PostPosted: Thu Mar 27, 2008 3:50 pm    Post subject: Reply with quote

Understood regarding the intent of the inclination reading and it being an indication of the gun-target-line orientation.

However, I wanna' make sure I understand the frame of reference of the plot for the inclination vectors\arrows. Most of the arrows in the plot look to be pointing upward -- pointing somewhat in the same direction as the course of Tiger. I took this to mean the Renown was well ahead of and slightly to the starboard of Tiger. I was therefore thinking the frame of reference was that a 90-degree inclination estimate equals same heading as Tiger – Renown’s Stern is in line with Tigers Bow. But you seem to be saying that a 90-degree gun-target-line inclination would imply the gun-target line is at a right angle relative to the heading of Tiger. Broadside to broadside – Tiger’s Starboard about parallel with Renowns Port (with allowance for 1000-yard layoff behind Renown for safety). Which is confusing to me as the inclination arrows are (mostly) pointing approximately upward.

I am probably not forming my question very well. Maybe I should try to sketch it out -- or do you get the gist of my question?
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PostPosted: Thu Mar 27, 2008 10:12 pm    Post subject: Reply with quote

I was puzzled by the arrows myself, as they seemed to be at angles not wholly representative of the value written over them. e.g., most appeared to show approx 90 degrees to the left, but some show around 45 to the left even though the number is not so.

I think it is possible by having all the arrows being "up", it merely means to show that the inclination is to the left side.

I may augment the document as written with a Dreyer-style range plot showing the timed ranges as noted in this chart.

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jwduquette1



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PostPosted: Fri Mar 28, 2008 7:21 am    Post subject: Reply with quote

Thanks. I suppose I need to brood a bit more on this problem.

It looked like the true location of Renown relative to Tiger is displaced downward because of the amount of information being conveyed on the plot relative to how much paper can be stuffed into the report. The various gun inclination estimates, CCT inclination etc. are than a true indicator of where the Renown is relative to Tiger.

But I’m not wed to my casual interpretation\misinterpretation. It would seem to make more sense from a safety perspective to be doing some sort of broadside-to-broadside excercise vs. a bow-to-stern excercise. To that end I (as I am sure others as well) would very much enjoy seeing your Dreyer-style range plot.

I sent you an email via the forum email option thingy. It contained some additional info you were asking after.
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jwduquette1



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PostPosted: Fri Mar 28, 2008 8:44 am    Post subject: Reply with quote

Perhaps the Arrows represent the frame of reference for each location conducting the inclination reading? Than the number adjacent to the arrow represents the inclination relative to each specific frame of reference -- measured clockwise from the direction of the arrow. Plus the 1000-yard layoff which I suppose would explain why the inclination vectors all seem to fall behind the course plot for the Renown.

But that would imply a huge amount of error between the various locations conducting the inclination measurements. But perhaps the 1000-yard stern layoff for safety is tough to judge particularly when the true range is not known nor the true rate of closure between Tiger and Renown.


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Last edited by jwduquette1 on Tue Apr 08, 2008 11:35 am; edited 1 time in total
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PostPosted: Fri Mar 28, 2008 1:22 pm    Post subject: Reply with quote

I can't believe that is true. The lines of sight implied (as you showed them) differ in some cases by minutes and minutes of the Tiger's travel and would also imply that the target remained still.

These were all taken at nearly the same moment or there'd be no use at all of averaging them.

I'm a little mystified.


Also -- what is CCT, I wonder? Conning/Command Tower?
I think it is actually GCT "Gunnery Control Tower"

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PostPosted: Fri Mar 28, 2008 1:32 pm    Post subject: Reply with quote

Actually, it is not as weird as I thought. The one that I thought was labelled "125" must be "12.5", as this makes it roughly agree with angle shown (which is almost along the line of bearing).

However, I can't understand why they seem to be along the line of bearing to the line of fire (at the target towed behind the Renown), and not to the line of bearing to the Renown.

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jwduquette1



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PostPosted: Sat Mar 29, 2008 9:25 am    Post subject: Reply with quote

I was going back through the Tiger Gunnery training report text yesterday (the first two pages of the materials I posted), and I thought it said something to the effect that inclination errors of up to 40-degrees(!!) were incurred during the exercise.

Regarding CCT -- yes, I think you're right, I think the text of the report says GCT. The plot looks like it says CCT. But maybe the hook of the G disappeared as a result of the image quality.

Unfortunately this particular form of gunnery exercise was the only example in the Jan 1918 training report. I couldn't find any other ship gunnery training reports in which this same type of exercise was conducted.
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jwduquette1



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PostPosted: Sat Mar 29, 2008 9:29 am    Post subject: Reply with quote

I wasn't sure there was a towed target in this excercise. All the other guunery reports provide some details about the towed target. But I don't think this one did. I thought the intent was to just layoff of the stern of the Renown by 1000-yards.
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PostPosted: Sat Mar 29, 2008 12:01 pm    Post subject: Reply with quote

You may be right. I think the arrows are not drawn very carefully as to their angle relative to the line of sight, but the data is what we should trust. I did not receive your email with index data on this.

Should I bother trying to make a Dreyer range plot?

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jwduquette1



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PostPosted: Sat Mar 29, 2008 12:14 pm    Post subject: Reply with quote

I'll try you through the forum PM on Monday. The report is on my desk at work.

As to the Dreyer Plot, I'm sure there are a number of folks including myself that would be interested in seeing the like. It might jar loose some ideas about what it is we are seeing with the arrows on the Tiger training plot.
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