That 0555 turn....

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paulcadogan
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Re: That 0555 turn....

Postby paulcadogan » Wed Jan 18, 2017 2:35 pm

Alberto Virtuani wrote:However, why did Rowell draw the turn exactly at 5:55 as a sharp turn instead of showing a "soft" course change from 5:57 till 5:58, as he certainly did at 6:00 with the emergency avoiding maneuver ? Is this just a simplification from Rowell (as for the turn at 5:50, the one at 6:10 etc.)? If yes, then it would be still at a wrong time, no doubt about it. Drawing a map I would show a turn at its execution time, not at its ordered time......


Alberto I think you answered your question in your question - and a very good answer at that! :clap:. The other turns are shown as turn on a dime "track chart" turns. For these, we don't know when they were ordered vs executed either! He had no choice but to draw the turn around Hood as a gradual curve, as in the melee on board there was probably not much of a precise record - "Hard a starboard!" "Hard a port!" "Wheel amidships!" "Hard a port!". "Steer 160!" "Make smoke!".
Qui invidet minor est - He who envies is the lesser man

Cag
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Re: That 0555 turn....

Postby Cag » Wed Jan 18, 2017 3:32 pm

Hi All

Hi Paul Hi Alberto, that is a possibility too, the execution may well mean the signal execution and not the execution of the turn. I just thought that with it being linked to the A arcs thus becoming open it meant it's completion.

The only thing is if the turn was begun at 05.57 would it not show a greater degree of range loss in salvos 3 through to 6 due to the rapid rate of closing distance?

I'll have a go at drawing that out again but I'm afraid I'm running out of paper!

Best wishes
Cag.

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Alberto Virtuani
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Re: That 0555 turn....

Postby Alberto Virtuani » Wed Jan 18, 2017 3:52 pm

Paul Cadogan wrote: "Alberto I think you answered your question in your question - and a very good answer at that! :clap:"

Hi Paul,
thanks for your appreciation, however, the second part of my question is still there......

Being the navigating officer, and having to draw a map (even simplified), knowing exactly (in case of the "5:55" 20° turn to port) when it was ordered (5:55) and when it was executed (between 5:57 and 5:58), I would have drawn the map with a sharp turn at 5:57:30 (the mid point of the turn) NOT at 5:55 (or 5:54:30 as per salvo plot)..... :think:

Still more questions than answers, I'm afraid......


Bye, Alberto
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)

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paulcadogan
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Re: That 0555 turn....

Postby paulcadogan » Wed Jan 18, 2017 7:07 pm

Alberto Virtuani wrote:Being the navigating officer, and having to draw a map (even simplified), knowing exactly (in case of the "5:55" 20° turn to port) when it was ordered (5:55) and when it was executed (between 5:57 and 5:58), I would have drawn the map with a sharp turn at 5:57:30 (the mid point of the turn) NOT at 5:55 (or 5:54:30 as per salvo plot).....



I absolutely agree! The fact is, he did not and it leaves us hanging with no definitive explanation - just speculation. :(

Cag wrote:The only thing is if the turn was begun at 05.57 would it not show a greater degree of range loss in salvos 3 through to 6 due to the rapid rate of closing distance?


Unfortunately Cag, the only salvo ranges we can rely fairly well on are the ones that straddled (0556, 0558, 0600). The others, the actual distance over or short is pretty much an estimate. So we cannot calculate a reliable rate of change of true range from 0553 - 0555 and from 0555-0557 for comparison. But it is true that there would be an adjustment to the location of each fall of shot at the ranges fired at by continuing on 300 deg until 0557.

Paul
Qui invidet minor est - He who envies is the lesser man

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wadinga
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Re: That 0555 turn....

Postby wadinga » Wed Jan 18, 2017 7:28 pm

All,

There is a danger of placing too much reliance on Rowell's maps. He never claimed they were precise. They never needed to be precise for the purposes of the Hood Enquiries.

Yesterday I was on the bridge of HMS Belfast looking at the Admiralty Research Laboratory plotter made by Laurence Scott Electromotors of Norwich. This was the main automatic plotting device recording the ship's track with an electrical mobile unit driven by gyro and speed input underneath a pane of glass. A pin point of light shone up onto the chart on top of the sheet of glass and the navigator would mark off points on the track. Presumably different scales could be set up to suit the scale of the charts.

There is also a later electronic navigation aid which could provide input, Decca mainchain but this is late war/post war development. In 1941 there was just revs/speed log and gyro heading and navigator's estimates. Out beyond the Denmark Straits navigational precision was not possible or required since there was nothing to collide with. Suffolk was 20 plus miles away from where she said she was and the Germans 90 plus out.

Presumably the plot destroyed by blood from the Compass Platform in PoW was being generated with a similar machine. I believe the originals of the Suffolk and Norfolk strategical plots were made on such a machine. The "noisy" nature of the tracks (ie not ruler straight lines) suggests such input.

Subsequently maps were created in PoW, but I am still checking what the output from the Admiralty Fire Control table was, but I do not believe the paper plots were geographical at all, but merely graphs showing changes in various factors. Rowell does not guarantee times at all despite what he could glean from Gunnery plots.

All the best

wadinga
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Cag
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Re: That 0555 turn....

Postby Cag » Wed Jan 18, 2017 8:20 pm

Hi All

Hi Wadinga, funnily enough I thought I read that somewhere and had been looking through notes of some IWM interviews.

Mr Graham Phillip Allen interview tells the same story. He was a midshipman and says that the compass platform had a box in it that covered a glass floor panel that looked down on to the plotting device you describe. It had cogs and wheels to effect scale and a light that moved to show the ships position on the chart.

These were plotted by putting a pencil dot where the light shone on the chart and they joined the dots! Rowell up above could see the plot and enemy movements were plotted using different coloured pencils. The Schoolmaster Lieutenant also kept the log which the Navigator dictated.

He remembers the hit and that the lights went out and the emergency battery lights lasted only a few seconds. He describes how the plot became covered in blood and how they tried to save the plot by use of cocoa tins.

He also describes the funeral at sea of those killed and that due to the effect of the compass platform shell that his fellow Midshipmens bodies were wrapped in canvas but unfortunately they were no more than a small parcel.

As with all these kind of things very sad
Best wishes
Cag.


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