Battle Tracks at Denmark Strait

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Bgile
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Re: Battle Tracks at Denmark Strait

Post by Bgile »

Vic,

Since you seem to have overlooked this post, I'm repeating it:
Bgile wrote:At what point on your chart does Bismarck interpose between PG and PoW, resulting in the order not to fire over the flagship?
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Re: Battle Tracks at Denmark Strait

Post by Vic Dale »

Bgile wrote:Vic,

Since you seem to have overlooked this post, I'm repeating it:
Bgile wrote:At what point on your chart does Bismarck interpose between PG and PoW, resulting in the order not to fire over the flagship?
Sorry about that - some nasty accusations flying about which distracted me.

I don't think Bismarck did impose herself across the range between PG and PoW during the actual battle (0550 to 0609) as shown on my chart, though she may well have done so later on.

The 1st Gunnery Officer Lt Jasper reported that PG made 3 avoidance maneuvres in response to torpedo warnings and that Bismarck came directly into the line of fire after the "third" maneuvre made at 0615 (see chart with translated annotation). He received the order to cease fire immediately thereafter though his guns fell silent at 0609.

His report reads thus;

"During the battle our own ship turned sharply three times. Firing continued during these turning maneuvres. The battery was twice temporarily and laterally displaced from the target during this evolution. Bismarck came directly into our line of fire after the third avoidance maneuvre. Accordingly I received the order form the ship's command; "Do not fire over Bismarck." And immediately thereafter "Cease fire." Firing ceased at 0609.
(PG's War Diary available on this site).

Jasper is explaining that although "Cease Fire" was officially given in PG at 0620 after the third turn away, his main battery actually ceased firing at 0609, probaly due to the target being onscured behind her smokescreen or drawing out of range.

Brinkmann's estimate of the separation between the two vessels at the beginning and end of the battle was about 3000 m. So although my chart shows a much greater separation at the time Lutjens ordered Bismarck to cease fire and resume her original course at 0609 this was not the battle's end as recorded in PG's war diary. At 0620 there was a further exchange of fire between Bismarck and PoW and prior to this at 0615 PG made a hard turn to starbaord away from a further torpedo alarm. The avoidance turns were made at 0604, 0607 and 0615.

I believe it is the time after the third turn at 0615 to which the signal refers and not to the battle proper (0550 to 0609) when PoW and Bismarck were still in action and after which Bismarck was clearly seen to turn away out of the battle by Captain Leach.

Below I have produced a most rudimentary presentation to illustrate how Bismarck may have come across the range at 0620 and from this it is possible to see separation reducing back to about 3000m. I have no way of verifying that this happened at present, but it does seem a likely explanation, or something fairly close.

I do not lay claim to have produced an accurate extension of Bismarck's track.

Hope this helps

Vic Dale
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Re: Battle Tracks at Denmark Strait

Post by Vic Dale »

To Karl

If we can keep the temperature down we may learn a little.

How PoW turned after Hood Blew up.
The following can be found in the Hood documents with particular regard to Wake-Walker's Gunnery and RDF report.

Observed from Norfolk by CS1; Action with "Hood" and "Prince of Wales"

"Both ships seemed to straddle early, but after Hood sank, Prince of Wales sustained the fire of both enemy ships with remarkably little damage but for the unlucky hit on the bridge. As the range came down to 15,000, this points to very poor shooting."

We need to consider how PoW managed to get down to 15,000 yards from a range of 17,000.

The rate of closure on the relative courses between PG and PoW and which would bring the range down from 17,000 to 15,000 yards would take about 3 minutes IF there was no turn away from Hood to avoid her smoke.

Even with the 20 degree turn (as shown on the ship's reconstructed chart) it would take 2.5 minutes, to close to 15,000 yards but at that time the ship would be heading 300 degrees and would require a turn of 140 degrees to reach a course of 160 degrees (necessary to acheive the break away and begin to make the smoke screen effective). Such a turn would take at least another minute to complete, but the progress to the west would not be sufficient to keep the ship clear of Hood's smoke which was carrying to the west on the 10 knot wind at 350 yards per minute.

Add that extra minute for the turn and PoW would become enveloped by the smoke. Not only that, if PoW was heading 300 degrees at 0602:30 (2.5 minutes after Hood blew up) the strike on the compass platform would come in at the wrong angle - 38 degrees instead of the correct 48 degrees.

Heavy warships must follow fair curves when they turn and they can only do so gradually. If they apply full-rudder they will lose loose considerable speed as the force of the screw-rudder reaction forces the stern sideways and slews the ship into her turn. A ship will pivot in hard turns somewhere about one third of her length from the bow, so it can be readily appreciated that forcing two thirds of the hull sideways to make a new heading will shed speed very quickly. If Captain leach had made that sort of turn away at 0602, he would not have cleared Hood's smoke. He would not have cleared if he turned at hard at 0603 or 0604 either.

In my opinion, Leach turned hard out to starboard and then corrected back with less rudder as the ship cleared the smoke to the west, he brought his ship back to a workable battle course to resume the fight, just in time to take the hit on the compass platform. This hit will have disrupted the ship's command for at least 2 minutes. This includes time for Leach to recover from the shock of the hit itself and on finding it impossible to con the vessel from the compass platform move the ship's command down to the armoured upper command position one deck below. Now he has to establish communications and get the ship back under control. Not before 0604 (just one and a half minutes 90 seconds) would it be possible to regain control and he would then need time to assess the situation and receive battle reports before making his decision to break away and make smoke.

PoW's turret mounted range finders.
Evidence as to the state of PoW's gunnery optics can be found in Mc Mullen's Letter to Ludovic Kennedy from which we have this extract;

"Y Turret was "wooded" as "A " arcs were not open. A rough sea and strong wind on the starboard bow together with our high speed resulted in a continuos stream of spray and water over A and B Turrets, and inspite of their window washing gear neither obtained any ranges before opening fire."

This is why PoW was forced to rely on the smaller duplex instruments located on the fore and after DCTs. Mc Mullen could not get adequate ranges before opening fire and was forced to use the far from accurate horizon cards, gauging the range by the relationship between Bismarck's hull and the horizon, though in conjunction with a range form the 15 duplex range finder. He fired on 26,500 yards and then corrected down until he got the straddle at salvo 6 and from there, using the elevation figures, he was able to work back later to disciver the true range oif 25,000 yards. Rate of closure and rate of target bearing change in conjunction with target inclination, plus "own ship's speed" and heading would provide the necessary refinements to present a very accurate account of Bismarck's course and speed for further gunnery solutions and for later construction of the enemy's battle track.

The combination of "shorts" and "overs" plus the "straddles", makes for a very definite course for Bismarck between 0554 and 0600. There is not much choice about where to placed her at any given time according to the salvo plot and we must bear in mind that she is a vessel which again must follow fair curves. Not only that, in battle she would employ very sparing rudder so as not to advertise each course change to the enemy gunners.

The salvo spreads were in the order of 300 to 350 yards, though when PoW was making her turns to avoid Hood the spreads went wild opening out to 2000 yards, though all shot fell good for line. On my chart I have scaled the salvo spreads for 350 yards, though this does not take account of elongation due to range. They give a fair idea and it should be known that I have not predicted to be any closer than 300 yards for accuracy in the chart

It really does make me laugh that some people are ever ready to believe "PoW's" track from the salvo-plot and completely disregard "Bismarck's" plotted course. The fact is the Admiralty Gunnery Table produces "target tracking" and does not under any circumstances produce "own ship's" track. Own-ship's "heading" and "speed" are fed into the computer in order to compenstate for movement between salvoes and table turning produces the time element - where she will be firing from by the time the bridges are fired in the gun-chambers. These figures will be recorded for future reference, but if the table is stopped for any reason such as a hard turn or a vessel going onto a reciprocal course, the figures won't make much sense, because the time element will be missing.

What could possibly be the point of the table producing own ship's track when that is already plotted in the ship's chart house?

Below is a typical range plot printout produced by a gunnery table.

Vic Dale
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Bgile
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Re: Battle Tracks at Denmark Strait

Post by Bgile »

Vic Dale wrote:
What could possibly be the point of the table producing own ship's track when that is already plotted in the ship's chart house?

Vic Dale
When I served in submarines it was customary for the duty QM to keep a nav plot showing own ship's course and speed. If we were in a "combat" situation we would have a fire control tracking party keeping a plot showing own ship's track but additionally showing target tracks. There is value in doing that for tactical purposes, but you don't want it messing up the QM's nav plot. So yes, there is value in a separate plot.

Why in the world would Bismarck help Holland by turning toward him? Do we have any source documenting this initial turn by Bismarck?
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Re: Battle Tracks at Denmark Strait

Post by Olaf »

Vic Dale wrote:Below I have produced a most rudimentary presentation to illustrate how Bismarck may have come across the range at 0620 and from this it is possible to see separation reducing back to about 3000m. I have no way of verifying that this happened at present, but it does seem a likely explanation, or something fairly close.Vic Dale
Hi Vic ~ I'm not quite sure if it is helpful for this discussion but there are a few things on your chart that need some clarification. There is something wrong with the English translations of the German wording.

I'm not taking either your or Antonio's postion, if so, then it is unintentional... :whistle:

To start with the upper right comment:

laufendes Gefecht an Bb
==> I don't know if 'running battle' exists in the English language, in German, it basically means exchanging broadsides with the enemy who is - or is about to - travel in roughly the same direction (or in other words, who is not traveling into the opposite direction which maybe would only allow for a few quickly exchanged broadsides)
==> 'Bb' is the abbreviation for 'Backbord' ==> larboard

Von Flotte: Auf den Gegner am weitesten links
==> This is correctly translated.

Auf rechten Gegner
==> At right enemy - NOT: 'FROM' right enemy. The vertical line leads roughly to the 0557-mark. I assume, PG fired at Hood…. Because…

Wechsel auf linken Gegner
==> Change fire to enemy at left.

The next few translations are correct. The bottom one:

King George feuert um 0620h – Aufschläge kurz[b/]
==> KGV fires at 0620h – falling short. (They simply refer to PoW’s shell splashes…)

Then, on the far right, the comment which you couldn’t read:
Gegner fliegt in die Luft
==> Enemy is blown up

If there are any other question, please let me know…

Best ~ Olaf!
Why the Navy? Well,.... I was young and short on money...
http://linerpara.de
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Re: Battle Tracks at Denmark Strait

Post by Vic Dale »

To Olaf.

I didn't actually prepare the annotated chart, I simply used an old one from a discussion long ago which had the correct direction of PoW at 0620. It was the KGV identification which was important.

Many thanks for clarifying those other points though

Vic Dale
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Re: Battle Tracks at Denmark Strait

Post by Vic Dale »

Bgile wrote:
Vic Dale wrote:
What could possibly be the point of the table producing own ship's track when that is already plotted in the ship's chart house?

Vic Dale
When I served in submarines it was customary for the duty QM to keep a nav plot showing own ship's course and speed. If we were in a "combat" situation we would have a fire control tracking party keeping a plot showing own ship's track but additionally showing target tracks. There is value in doing that for tactical purposes, but you don't want it messing up the QM's nav plot. So yes, there is value in a separate plot.

Why in the world would Bismarck help Holland by turning toward him? Do we have any source documenting this initial turn by Bismarck?
There is no source for the turn toward other than the obvious indication on the Salvo Plot. Bismarck could not have steered any other course. This is presented by the manner in which target bearing became fixed at 330 deg. in PoW after the first straddle. The fact that all shot fell correct for line accurately marks Bismarck's position by the minute along the course of 192 degrees, having regard for time of flight and lastly she makes the 1st and 2nd straddles on that line.

The range came down from 21,150 yards to 18,250 yards in just 2 minutes, so the angle of convergence between PoW and Bismarck had to be very sharp. PoW could not close at that rate herself without Bismarck adding her share to the rate of closure. Each ship was moving at 950 yards per minute and the distance to cover, in oder to close to the shorter range is 2900 yards PoW is 1000 yards short, so Bismarck must have turned toward to make up the difference.

I think the way to consider this is to think the way Admiral Holland thought. He turned his ships so as to close the range rapidly and bring them into their safety zones. Bismarck too had a safety zone within which she would take shot on her belt rather than her decks and turret tops. As long as the belt was inclined toward or away, the ship would be relatively safe. So Lutjens (or rather Lindemann) in fighting the ship this way was not doing Holland a favour, but was aiding his own gunners by removing a factor from the "gunnery solution" - that of target bearing change.

If the first phase can be got out of the way quickly - the approach to the most effective range - rate of fire, tightness of spread and accuracy of prediction would come into play and favour the most modern ship, with the high velocity weapons in the slugging match which would surely have developed had Hood lasted longer.

Lindemann clearly had tactical command of his vessel and his actions were agrressive. At 0609 Lutjens had to order him to cease fire and turn back to the original course, to stop him going after PoW.

PoW would have kept her track accurately plotted in the charthouse. All that would be in the gunnery table would be the changes of heading at given times, the TS log would record the headings as they were fed to the table. If the table was stopped it would cease to record accurately, because the element of time would be lost. There would be no logic in trying to keep up with a series of sharp and continuous turns. The table would be stopped for a while until a clear and steady heading had been reached, so any changes extracted from the table during that time would tell very little about what had just happened.

This I believe accounts for the difference between the ship's own course, as shown in the Salvo Plot and that shown on the reconstructed charts.

In the charthouse the fast turns could be plotted by degrees of rudder against time in increments of ten seconds. The tactical radius of the ship would then be used to calculate each turn accurately. I doubt this would be done anywhere else, unless there was a chart table on the compass platform. Considering that so much was made of the main chart and battle narrative being lost, I doubt that a second chart was being kept. The only other record which would come anywhere near would be in the wheelhouse where the turns and degrees of wheel ordered would be logged. A similar log would be kept in the ship's command position. The turns at 0600 to 0603 were quite different to the battle turns which would be made at half a degree per second or less.

Vic Dale
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Re: Battle Tracks at Denmark Strait

Post by dunmunro »

Vic Dale wrote: ?

Below is a typical range plot printout produced by a gunnery table.

Vic Dale
This appears to be a range plot from a Dreyer table. You still haven't address the issue of PoW's Gunnery Aspects Report stating that the forward DCT was wooded after salvo 18.
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Re: Sample Range Plot

Post by Bill Jurens »

Mr. Dale:

Other issues aside, the least you could do would be to acknowledge the actual source of the "Sample Range Plot" which you appended to this thread earlier, and ask for permission to reproduce (as did the Hood site where you probably found it.) In fact, it's "copyright (c) W. Jurens/International Naval Research Organization 2001." The illustration is actually taken from an article by the late William Schliehauf, "The Dumaresque and the Dreyer", which I edited and helped to illustrate. It's good -- though by no means required -- reading, provided material isn't taken out of context. Mr. Schleihauf really knew his stuff, and I am currently in the process of helping to prepare his last paper, also on gunnery, for posthumous publication.

Bill Jurens
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Re: Sample Range Plot

Post by Vic Dale »

Bill Jurens wrote:Mr. Dale:

Other issues aside, the least you could do would be to acknowledge the actual source of the "Sample Range Plot" which you appended to this thread earlier, and ask for permission to reproduce (as did the Hood site where you probably found it.) In fact, it's "copyright (c) W. Jurens/International Naval Research Organization 2001." The illustration is actually taken from an article by the late William Schliehauf, "The Dumaresque and the Dreyer", which I edited and helped to illustrate. It's good -- though by no means required -- reading, provided material isn't taken out of context. Mr. Schleihauf really knew his stuff, and I am currently in the process of helping to prepare his last paper, also on gunnery, for posthumous publication.

Bill Jurens
My sincere apologies for that. The image I had was an isolated picture mixed with recovered material from an old failed hard disk and there was no indication of it's source, so I had no idea who produced it or where it came from.

I will gladly ask for it to be withdrawn if you or the HMS Hood site think I should and simply insert the url for the site as would be the correct thing to do.

Vic Dale
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Re: Battle Tracks at Denmark Strait

Post by Vic Dale »

dunmunro wrote:
Vic Dale wrote: ?

Below is a typical range plot printout produced by a gunnery table.

Vic Dale
This appears to be a range plot from a Dreyer table. You still haven't address the issue of PoW's Gunnery Aspects Report stating that the forward DCT was wooded after salvo 18.

Well the statement also begs the question "When after salvo 18?"

Captain Leach is giving details of events in chronological order about gunnery and is not giving a blow by blow account of the battle. Centrally directed fire produced it's last salvo at 0601:50 and subsequent to that a major turn away wooded the Fwd DCT. Control was switched to the after DCT which by this time had become blinded by the smoke screen. The officer of "Y"turret could see the target and was able to fire three salvoes.

If this were the battle narrative there would be one heck of a lot missing from the story. It is simply an attempt to explain a succession of certain events in the gunnery department alone.

Salvo 18 was fired at 0601:50, so if the Fwd DCT was wooded immediately after the salvo, it would have to mean that PoW was steering 210 degrees or thereabouts when the salvo was sent off. And this would mean PoW was heading directly into Hood's smoke. Which would be an odd thing to do. There would be no need to lay her own smokescreen for a start.

We know PoW did not enter Hood's smoke, so the expression "wooded after salvo 18" has to mean some time after salvo 18 and that could mean any time.

We might consider Hood's sinking; the after magazine blows up and the foretop falls backwards, after which the bow lifts to 45 degrees and then continues rising until it is almost vertical before slipping backwards into the sea. This take seconds to read, but covers a period of at least 3 minutes. We know it would be ridiculous to dismisss Hood in a few seconds, there is drama, the ship is a huge and ponderous thing and everything about her destruction took time.

So too the events subsequent to Hood's sinking in PoW. The ship was struck on the compass platform at 0602:30 and the shot came in at angle of 48 degrees from the starboard bow (green 48) so her course at that time has to be roughly equivalent to that on which Hood blew up. Now factor in a turn of 70 degrees which will take some 30 seconds to acheive and PoW will go diving into Hood's smoke which apparently Captain Leach was keen to avoid. Hood's smoke has expanded out 500 yards in all directions, but is also blown 350 yards per minute along her original track. PoW cannot make a clear exit from the scene until 0605, at which time she still needed her own smoke screen and was avoiding that produced by Hood.

PoW's Gunnery Aspects Report is a valuable document, but it remains very far from the full picture of what happened that morning. It must be taken in conjunction with other material in order to prepare any clear idea of what happened.

Vic Dale
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Re: Battle Tracks at Denmark Strait

Post by Bgile »

Vic,

I'm confused. Are you saying "sometime after salvo 18" could actually mean "sometime after salvo 19"? Or "sometime after salvo 20"?
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Re: Battle Tracks at Denmark Strait

Post by Vic Dale »

To Bgile.

Salvo 19 was fired from "Y" turret in local control, so that would rule it out of the total of salvoes counted as centrally directed fire - salvoes 1 to 18.

The turn away under smoke had already begun by the time salvo 19 was fired, so no, I am not saying that the turn occurred after salvo 19. By this time PoW already had her stern turned towards the enemy because the smoke screen was now blocking the after DCT's view of the target.

To clarify; PoW turned out around Hood after she blew up and fired salvoes 15 and 16, before the initial hard starboard helm was answered. The turn took her head towards the enemy and at this time PG would have been steaming across her bow (possibly shown in NH69725). Having cleared Hood's smoke and left the wreck astern (heading towards the enemy) she turned back to port and the next two salvoes were fired at 0601:40 and 0601:50.

The ship was now turning back to port to resume her original closing course to continue the battle. At 0602:30 the hit came in on the compass platform, at "green 048" killing most there. The ship's command was eventually moved to the armoured "upper command position" one deck down and the battle continued. Subsequent hits convinced Leach that his untried ship might be lost if he remained under this saturating fire and he took the decision to turn away under smoke at 0605. Two and a half minutes separate the hit and the turn away.

Two minutes and thirty seconds is not a great deal of time to assess the condition of the ship and make the momentous decision to withdraw.

The ship turned away at 0605 and made smoke. The forward DCT became wooded as her head came to 210 degrees and the after DCT was tasked to take over control. That DCT could not now see the target due to the smoke which was coming across the range, helped by the 10-knot wind. The Officer in "Y" Turret could still see the target under the smoke and given the sighting difficulties in the two Main DCTs took the turret into local control and fired his 3 salvoes.

An important point to consider is the rate of train of the 14 inch turrets at just 2 degrees per second. Very likely the hard turns were made at a rate faster than the turrets could train, but in order for salvoes 17 and 18 to be fired the turn had to decelerate or fire would not be effective. It seems that fire went somewhat wild with spreads opening to 2000 yards and shot falling out of line ahead of the target. This indicates that the turn back was a hard turn also. Captain leach excuses his gunners lack of control over "spread" and "line" as being due to the ship turning under full helm.

Turns made under full helm will greatly reduce speed and they are notroiously hard to control, due to momentum. It takes at least 20 seconds to get a ship the size of PoW to answer her helm when making high speed on a straight course, so very likely the turn out resulted in oversteer due to the sheer weight of the ship.

Try spining a coin on the table and it will be seen that a heavy coin will spin for longer than a lighter one due to the effects of momentum.

A turn made under full helm would take more than 20 seconds to correct, so the shallow 20 degree turn shown on the chart produced in Pow, would not be possible using full helm which is documented. Captain Leach describes the ship shuddering and pointer needles sticking due to heavy vibration and the ship heeling. PoW would make at least 40 degrees to starboard before opposite wheel could begin to correct and first the swing to starboard would have to be slowed and stopped in order to begin to bring her head round once again.

We have two hard turns, first to starboard and then to port and this second turn brought the head round so that the strike on the compass platform came in at "green 048" at 0602:30. There is a hard and uncorruptable logic to the way a ship must turn and will turn, so in drawing up the chart it is necessary to consider what must happen between 0600 and 0602:30 to position the ship to take a hit from "green 048" which includes 2 turns under full helm. That is what I believe I have been able to show on my chart for PoW's movements.

Vic Dale
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Re: Battle Tracks at Denmark Strait

Post by dunmunro »

Vic Dale wrote:

Well the statement also begs the question "When after salvo 18?"
Vic, you have PoW running roughly parallel to Bismarck for ~3 minutes after salvo 18, and despite the fact that PoW has 3 functioning main battery turrets, and 2 functioning DCTs, she doesn't fire at shot! C'mon, this is a complete departure from reality. If this had really occurred then there would have been some very pointed questions asked and probably a few court martials. PoW was turning hard, and after salvo 18 this wooded the director and the forward turrets, any other explanation implies that Leach falsified his report.
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Re: Battle Tracks at Denmark Strait

Post by Bgile »

Vic, are you saying that there is a 20 second delay from the time that the rudder begins moving to the ship responding to the rudder? That sounds really strange to me. I would think that at high speed in particular, the ship would begin to respond instantly. It might turn slowly at first, but wouldn't you see some change in heading the instant the rudder started to move? Of course, the ship would take some time to actually move in a new direction (inertia), but I would think the stern would start swinging out immediately, slowly at first and then faster and faster until the turn rate limit was reached.

A good helmsman will not overshoot a turn, but will apply opposite rudder as he approaches the ordered course so as to stop the turn on exactly that course. You can expect the leading helmsman to be on the helm at battle stations.

In US practice, which is all I have personal knowledge of, you first get the order "Left fifteen degrees rudder". Then when the OOD figures out what he wants for a new course he will say "Steady course 160 degrees." At that point the helmsman is expected to maintain 15 degrees rudder until he has to meet the new course, and he will use his own experience to decide what rudder to use to stop the turn on exactly 160 degrees. That often requires at least some reverse rudder near the ordered course to keep from overshooting the turn. You can tell a rooky by the zigzag wake behind the ship.
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