Jump to content
Free downloads from TNA ×
The Great War (1914-1918) Forum

Remembered Today:

Aiming guns at sea


IanA

Recommended Posts

Charles - the mist is clearing. While I have no concept of the cogs and bits of string that make it go, I understand the communication and constant corrections from the gunnery officer to the turrets.

Borys - good site. I thought I had struck gold when I found fig 17A2 a simple trajectory. On reading further and examining the illustration, I understand the concept of 'line of sight' but fail to see how the gun can be locked on to this as the ship rolls. Exploring further to 'Surface Fire Control Problems' indicates to me that we are talking WW2 technology not available to our 1914 sea dog.

I confess that anything too technical may be beyond my little grey cells. Anyone got a copy of 'The Ladybird Book of Naval Gun Laying'? :unsure:

Thanks to everyone helping with this thread.

Ian

Link to comment
Share on other sites

  • 2 weeks later...

From my reading, the preferred method with centralized fire control was to calculate elevation for range relative to a 'level' deck and for the fire control officer in the sighting position to fire when the deck was indeed level. Trying to follow a roll with heavy-calibre guns was next to impossible.

On the other hand, there are instances of two battleships in the same action (Jutland) firing at opposite _extremes_ of their roll, when the motion was for an instant halted before swinging back the other way; one might be firing with gun barrels at a minimal elevation and letting the roll lift them to the correct elevation for range, while the other would be at max. elevation (and unable to increase range) and firing as the muzzles reached the downward extremity of the 'dip'.

While this makes sense, it requires the sea-state to be stable enough that you know how much dip to allow for (a few degrees could be followed through by the men in the turrets, but again, trying to follow through the whole swing Percy Scott-style with capital ship guns is almost impossible, and certainly not conducive to good shooting).

Link to comment
Share on other sites

Thanks for this response J.M. - it makes a lot of sense. Were the big guns able to elevate for maximum range or might this be increased if they did fire at the top of the roll?

Now for a whacky idea which I do not intend to dignify by giving it a thread of its own :)

I'm sure I have read of ships (in the days of sail) aiming low and skipping the ball across the waves in the manner of skipping a flat stone across a pool. I presume that this was to hit on the waterline. Am I making this up? When did it die out? Could it have any relevance at all in WW1?

Maybe I imagined it. :blink::D

Ian

Link to comment
Share on other sites

"I'm sure I have read of ships (in the days of sail) aiming low and skipping the ball across the waves in the manner of skipping a flat stone across a pool. I presume that this was to hit on the waterline. Am I making this up? When did it die out? Could it have any relevance at all in WW1?"

With the cannon ball?

Reasonable theory from Justin, but if the closing speed of the two ships was 50 knots did they ask the opposition to stop? Oh and ask the Captain's not to alter course.

Regards Charles

Link to comment
Share on other sites

You're not trying to tell me that you can't skip shells? :P:lol:

Ian

Link to comment
Share on other sites

I'm sure any gunnery officer would attempt to shoot every time at the same angle and phase of roll, but as the Hood site shows, the Director Layer is the bloke who's maintaining his telescope aim on the enemy, compensating for roll as he does so, and the elevation passed to the gunhouse pointers ultimately comes from his instrument. He also has the triggers.

There's some self-correction in the natural physics and geometry.

At the longer ranges, absolute elevation angle changes make progressively less difference to the fall of shot - from 40' to 45' would only make a few hundred yards difference, so small errors in timing the shoot - resulting in elevation angle errors at moment of firing - would have relatively small effect. The round is descending at perhaps 50', so an overshot still has a chance of connecting, especially with the upperworks.

The closer the action moves, although roll angle makes more difference to the flightpath in the flatter part of the trajectory, the vertical angle subtended by the target is also greater. Rounds that might splash thousands of yards long could still strike the compass platform...

Regards,

MikB

Link to comment
Share on other sites

I'm sure I have read of ships (in the days of sail) aiming low and skipping the ball across the waves in the manner of skipping a flat stone across a pool. I presume that this was to hit on the waterline. Am I making this up? When did it die out? Could it have any relevance at all in WW1?

Did'nt Nelson do this somewhere? Battle of the Nile? I remember reading how Barnes Wallis was impressed by this feat. Not really relevant to WW1 but it would be nice to know where / if Nelson used this trick.

Kevin

Link to comment
Share on other sites

I have heard of Ian's theory about skipping cannonballs in a film. I think the quote went "He was rumoured to have sunk the flagship with a yorker!"

Now what film was it from?!

Oh. I remember. Dambusters, of course!

Steve.

EDIT: Sorry Kevin. You beat me to it.

Link to comment
Share on other sites

  • 2 weeks later...

Guys

This is what the Pollen / Dreyer fight was about.

However Percy Scott developed a training apparatus that made his gunners the best (in spite of the problems with up & down, left & right - you know what I mean) in the Royal Navy before the intoduction of analogue 'computers' (what are 'directors' ??) let alone lasers and digital computers.

Carl Hoehler

Link to comment
Share on other sites

Carl,

There is a thread on the Pollen/Dreyer argument, which personally I dismiss after reading the court case in 1925 in which Pollen sued Dreyer for stealing his ideas and won.

The ‘Director’ is one of Percy Scott’s adaptations to achieve central control of the armament basically, a range finder, the fire control Officer aimed at the target and the guns followed. The Dotter was the predecessor of the ‘computers’ and helped determine range and deflection.

The initial down side to director firing from a central position was that refitted and new built ships had the fire control position aft of the funnels, which was not good for visuals.

Regards Charles

Link to comment
Share on other sites

Carl,

Intresting, seems the Americans made the initial moves into central fire control. The German navy had far better range finders than both the american and british simply because they where bigger, the width of the allied range finder was 4 foot 6 inches the germans was 9 foot wether that makes for twice the accuracy I don't know but they certainly used it well.

Regards Charles

Link to comment
Share on other sites

  • 2 years later...

Sorry to resurrect such an old thread, but this is the sort of stuff I love.

There is a thread on the Pollen/Dreyer argument, which personally I dismiss after reading the court case in 1925 in which Pollen sued Dreyer for stealing his ideas and won.

That is actually not a very fair assessment -- apart from the fact that Dreyer was not a party in the suit. The people adjudicating the matter were not well equipped to consider the technical issues at hand.

I think Pollen's greatest contribution was not in intellectual property, per se, but in inspiring others to think big. Indeed, the primary points of difference between the adopted methods of fire control (rate plotting) and his own ideas (true course plotting) were where the greatest advantages were obtained. Pollen's handling of the data either method might provide, however, demonstrated a precocious expertise and attention to detail which was not perfect, but set an inspiring standard.

The greatest lasting vestige of Pollen's was his display (two ships, basically arranged in the same relative manner as the battle scenario, except the range was fixed) and the veracity of his integration (if the enemy did not maneuver, his range and bearing were tracked perfectly if set perfectly at the outset). Dreyer's machinery did this well enough (as Brooks demonstrates in mathematical and forensic terms), but not perfectly well, if you catch the distinction.

tone

Link to comment
Share on other sites

The gunnery in the Great War was controlled by the Gunnery Officer who was in the director, this was an optical range sight (9ft) which when aimed at the target corrected the train and elevation angles to correct for own ship roll and pitch.

While the two navies differed in all details, neither had a rangefinder nor a gunnery officer in her directors in WW-1. While the RN often put him in the director by WW-2, the gunnery officer in the WW-1 RN stayed either in the spotting top or the gunnery control tower. The Vickers light aloft director had a layer (pointer, in American vernacular), trainer, sightsetter and phone man. There were generally fall-back directing positions, but the light aloft director tower, where fitted, was the preferred one though most vulnerable. I am not sure any suffered serious casualty in WW-1, however.

It is also worth pointing out that a few ships had no directors at all -- even the great, modern HMS Tiger was never so equipped.

re:

To cut a long story short the information was fed into a fire control computer system (Argo clock a mechanical analogue computer) and with the spotter entering the corrections on splashes a hit was made.

A few RN ships had Argo clocks, but the majority had slightly more ramshackle but very serviceable near-equivalents: Dreyer FCTs. Again, it is worth pointing out a very few major ships lacked these (some of the early BCs never got one).

re:

Each gun did have its own layer that had optical sights and the experience to fire over open sights. Standing by for flak.

Pretty much correct. When a ship was firing in director firing, the layers and trainers (actually, in the RN, a "turret director trainer") for the guns would "follow the pointer" on data receivers indicating where they should maneuver their axis of control, and the director layer would fire on the roll. But, in the case of casualty or if the director lost sight of the target, the turrets and their guns would indeed fire under the familiar pattern of layers and trainers looking through sights whose angles were set by sightsetters.

--- this seems like as good a place as any to dispel one of the most common fables I hear:

Fable: The RN shot poorly at the Falklands because their Dreyer FCTs factored in the Coriolis effect backward, as if in the Northern Hemisphere.

Truth: all fables should be this flamboyantly wrong! No ship at the Falklands had a Dreyer table, and the Dreyer tables had no provision whatsoever for accounting for Coriolis effect (it's hardly worth handing in any fire control system, really -- certainly not in this era -- its effect will be removed with the first spotting correction and not seen again unless the bearing of the action changes dramatically).

tone

Link to comment
Share on other sites

Many, many years ago I read "The Great Gunnery Scandal" by Anthony Pollen (nephew? Gt Nephew??) and was absolutely astonished at the complexity of the issues to be addressed to approach accurate shooting at Dreadnought-era battle ranges.

Despite the controversy between the two, truly we are standing on the shoulders of giants.

Link to comment
Share on other sites

If the chaps in the turret were 'following the pointer', how was the pointer driven? Since the laying and training should really be within a few minutes of angle, implying at least vernier-level accuracy.

How was the data transmitted - electrical voltage? Mechanical linkage? Either method could potentially introduce enough error to produce a load of clean misses. Is this why only a bit more than 100 heavy calibre rounds connected out of 4000 or so fired at Jutland?

New can o' worms here? :D

Regards,

MikB

Link to comment
Share on other sites

Why has everyone so quickly overlooked or dismissed Borys's and DrB's post #2 and #5 respectively so quickly? I would have though DrB's post added the weight of apparent USN experience to Borys's explanation. Take the range and direction, lay the sight on target with all the correction included for maritime "circmstances" and then as the ship's roll falls off and the sight comes down onto the "centre of the seen mass", hit the tit.

Much the same principle applies to rifle shooting to compensate for the shooters breathing and the change in posture because of expanding and deflating lungs. Take up the sight picture and first pressure on the trigger, breath in, sight picture goes down below the target, and whilst slowly releasing the breath (roll) and the sight comes back down/rolls onto the target, shoot at the centre of the seen mass.

cheers,

Just another landlubber,

Hendo

Link to comment
Share on other sites

It is also worth pointing out that a few ships had no directors at all -- even the great, modern HMS Tiger was never so equipped.

The TIGER was completed with a director system installed. Her salvos at the Battle of the Dogger Bank were therefore easily identified. All of the BCs were director controlled by the time of Jutland.

All of the BCs were provided with FCTs, the earlier ships during refits in 1915-16.

Link to comment
Share on other sites

The TIGER was completed with a director system installed. Her salvos at the Battle of the Dogger Bank were therefore easily identified. All of the BCs were director controlled by the time of Jutland.

All of the BCs were provided with FCTs, the earlier ships during refits in 1915-16.

Sorry -- I misread my source. Tiger never had a director fitted for her 6-inch batteries. These larger secondaries were given a high priority for directors (a smaller type on a pedestal) as part of the follow-up program that offered such coverage to light cruisers.

tone

Link to comment
Share on other sites

If the chaps in the turret were 'following the pointer', how was the pointer driven? Since the laying and training should really be within a few minutes of angle, implying at least vernier-level accuracy.

How was the data transmitted - electrical voltage? Mechanical linkage? Either method could potentially introduce enough error to produce a load of clean misses. Is this why only a bit more than 100 heavy calibre rounds connected out of 4000 or so fired at Jutland?

The data circuits were of electro-mechanical type, as in an early pinball scoreboard. Ranges were transmitted in 25 yard increments, deflections in "knots" left or right (actually, this was an angular measure -- "pips" would be a more accurate term, but knots was the one used for historical purposes). When in director firing, elevation and training angles were transmitted by similar means: 1.5 minutes per pulse for elevation and 4 minutes per pulse for training. A fast training mode (slewing) was supported in 2 degree steps so that guns could be quickly swung onto the target without losing sync between transmitters and receivers.

So -- the data circuits were asynchronous, meaning a spark or burp could cause the transmitters and receivers to disagree. This often took a moment to realize, and the remedy was to "line up pointers" by quickly running the transmitter from one extreme to the other, which rectified any issues. They'd then trot the angles back to one of several "zeroing" angles, e.g., guns trained 90 green. The Americans and WW-2 Brits relied more commonly on synchronous data circuits not subject to this sort of issue. Asynchronous circuits were appealing as they were simple and used fewer wires than the early, ham-handed synchronous types which quickly were outmoded.

The British system was pretty darned sexy. Three gaping flaws, however, were

1. Bearings being plotted on the dreyer tables were transmitted in the appallingly coarse quanta of 15 minutes, and rectified to compass bearings by gyroscopes with drunken wander cycles (at least with the early Anschutz gyros). This took a great idea of fire control and made it borderline a joke in practice, as one was hard pressed to see a bearing rate in the plot that was so distorted by the context of its creation. This sort of "soft" discovery was one of the great benefits to simulating these things on a computer, as I did in 2004-2005 over at http://dreadnoughtproject.org/tech

This was later made less critical by replacing this coarse data line with one that worked in 4 minute steps, but this happened well after Jutland

2. There was not a thorough and high precision means to communicate bearing angles to all that needed these data to make sure they were observing the same target in a distant line of ships. There were a few Evershed bearing indicators, but these worked in 2 degree increments, and there were not enough receivers at first. Therefore, your spotting team might easily be mistakenly observing the fall of shot another ship was directing against the ship AHEAD of their own actual target. By end of war, very nice devices called "spotting aids" were installed, which gave each spotter a set of binoculars which automatically tracked the target being signalled by a designator. Additionally, special timers that were set to the time-of-flight at the present gun range would ring a bell when one's own salvo was arriving to further minimize confusion over whose shells were whose. These would even help in a concentration of fire scenario -- one simply had to avoid firing his guns very near in time to his consort's discharge.

3. The Dreyer tables had an immature bearing plot until after Jutland, about which less is known (the handbooks describe a "standard bearing plot" used after Jutland, which seems pretty nice indeed, but was disliked, possibly because of the coarse bearing quantization it relied upon). The earlier plot certainly had less automation and invited more error. Even the "standard bearing plot" was soon replaced by "gyro director training", which inaugurated a better use of the plotting paper by plotting not bearings versus time, but differences in computed and director indicated bearings versus time. This practice made even low bearing rates easy to see on the paper.

tone

Link to comment
Share on other sites

The rolling (from side to side) is countered by firing at a certain moment of the roll. You aim at such-and-such degree at such-and-such moment of the roll (simplest when it is zero), and only fire then. As the rate of fire of the heaviest guns is BOOM every 30-45 seconds, you do not lose much shots to syncronization with the roll.

The pitch (front to back) is IIRC simply ignored.

The inaccuracy of the aiming etc. was countered by firing salvos - the more guns the better - and hoping that "dispersion" of the projectiles will put some in the right spot at the right time

The RN's hydraulic guns of the era were not nimble enough to use continuous aim in either local or director-fired mode, and so the solution was as you indicate, of firing at a specific part of the roll where the crosshairs were dragged across the target. This was even harder to achieve in practice than it sounds, as the delay between a trigger press and the firing itself was around 4/10ths of a second! So the layer had to anticipate the moment when the hairs would indicate the proper moment to fire. By happy chance, however, the range a shell reaches is fairly indifferent to small changes in elevation at the limits of the gun's range. But firing at the wrong moment could make a bigger difference at short and medium ranges -- though a greater danger zone helped in that event. Oh the intricacies.

As you may know, most geared guns (6-in and downward -- though I'm not sure all 6-in mounts were so workable) were continuously aimed by the practiced exertions of the gun layers.

Before automatic stabilization of guns could be achieved, around 1917 an interim solution was found for director firing (only) where a Henderson gyroscopic stabilizer would be used in the director firing circuit. This would stabilize the layer's telescopic view, and when he was satisfied with his aim point and with the number of guns indicated as ready, he'd press and hold his trigger. It would not immediately complete the circuit, however, as the gyroscope had a switch in series with it and that would only complete when the roll swept the ship past the proper angle. This angle could be biased to produce the correct (estimated) anticipated moment of closing the firing circuit. Not a perfect solution, but an automated one that would render more systematic results.

The Americans excelled at their precocious attainments in creating automatically stabilized guns, eventually in all axes of motion. I am not sure the British ever got to where the Americans did in this regard before the end of WW-II, but it is outside my readings.

When you talk about there being no solution for pitch (which is the same as saying no solution for roll when firing on bearings well ahead or abaft the beam), you are correct. This lack of treatment mattered relatively little in beam firings, but was massively problematic in a running fight, as at the Falklands, as the large roll of the ship became a large roll of the trunnions, and this became a larger periodic error in deflection. So, the need for gauging the roll in beam firing is one of controlling the range, and in end-on firing, it converts to one of controlling the deflection. This is one of the reasons why the gunnery hit rates were so low at the Falklands battle, but one must never discount the difficulties a desperate enemy's zigzagging imposes at extended ranges.

Soon after WW-I, the British made sure to incorporate cross-leveling into their directors and similar equipment. Similar to the layer, a cross-roll operator would look through a laterally-oriented scope and work a handwheel to keep his crosshairs on the horizon. Gyroscopes could also do this work, depending on the equipment. When a director was properly stabilized in this way, the natural job of the layer and trainer within it would intrinsically require them to counterbalance the gyrations the crossleveling imposed, and all would be worked out. And, similar to gun stabilization, when this was available, the cross-levelling influences would be part of the pitch and yaw sent to the mountings.

The very last thing you mention, the spread of a salvo in range and deflection -- this was a requirement to hitting anything unless your target had a deathwish. While patterns might be too large, if they were too small, all a distant enemy had to do to avoid any danger whatsoever was

1) wish that you had PERFECT FIRE CONTROL

2) change heading abruptly when he sees you fire

Perfect fire control is the worst to have when your target maneuvers in such a way that he can dodge your entire salvo pattern within the space of one time-of-flight. You'll hit him exactly 0% of the time if you aim perfectly and with such precision that your shells will all fly through a peachbasket in the water. But, if you aim perfectly about his projected position one time of flight in the future and your pattern is large enough that he must statistically remain within it no matter what he does with his rudder, you've imposed the greatest possible actuarial risk upon him. You won't hit with all your shots, but the maximum expected result will be realized, to his disappointment.

bottom line:

The problems of extended range gunnery present the starkest reasons why one would like to develop a guided missile.

tone

Link to comment
Share on other sites

Excellent informed reply and link to superb explanatory website - thanks. I can see that I've a few hours interesting viewing there to get a proper grip on this subject - there's a lot to learn!

Regards,

MikB

Link to comment
Share on other sites

Tony,

Thank you for a most informative series of posts,

Cheers,

Hendo

Link to comment
Share on other sites

This is a fascinating thread, and just the sort of thing that the Forum is rightly famous for.

I would never have thought about half of the problems and solutions.

On the bit about bouncing cannon balls, strictly speaking, if a ship was hit by a yorker, then it didn't bounce (cricket...something I know a little about!)

Thanks for filling about half an hour of mind-blowing information!

Link to comment
Share on other sites

Thank you all. I invite any and all of you to come visit my website, which tends toward the technical aspects of the period: fire control, communications, etc.

Of particular unique value on my site are some technical essays and videos of simulated fire control mechanisms which, I hope, make their ingenious design and function clear to a wider audience than did the manuals, handbooks and disparate expert counsels that informed my work.

A BBS, like this one, would certainly enjoy your questions. I get much less traffic, but the readers and posters do tend to the special focus on technical aspects of the naval period.

And, for the visually inclined amongst you, the collection of over 150 naval ship plans (at 100 DPI) are without equal anywhere on the web. Here is a sample:

plan_sample_image.jpg

tone

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...