HMS Benbow - Dreadnought Class Battleship
 

Any idea the purpose of the compass points around the top of the turret? Certainly does not appear to be very useful.

The markings are inclination markings, used in conjunction with range clocks to indicate to other ships in the battle line what direction and range the ship is firing, without using radio - if visibility is poor, and some ships are unable to see the enemy, this was useful. Developed by the Royal Navy in the Great War, it was copied by other navies. For a USN take, see https://www.youtube.com/watch?app=desktop&v=ZwT0nMrcPGQ - about 3.20 talks about these markings.

They are angle markings for use when the aircraft take off ramp is in use.
On Benbow, and others, a pair of rails was clamped to the barrels of either B or P turrets. Other ships and US ships used a similar apparatus to suit the aircraft and the turret.
The aircraft was hoisted in place and the turret turned to the angle measured for wind direction using the markings shown.
The aircraft was then launched into the wind.
The system was first used from HMS Repulse in October 1917.

Many thanks to "Our Ned" and "Malcolm G" for the explanation, not sure I totally understand how it works but get the general idea. Thanks again

In the linked video posted by Our Ned regarding what the RN would call Concentration Dials, the speaker made reference to the markings on the turret, stating that they were intended to communicate bearings to other ships.
There are 'problems' with his assertion:
The markings are not on all the turrets, they are only on the super-firing turret used for a flying off ramp.
The numbers and marks, while quite conspicuous, are too small to be seen and read from another ship.
The is no obvious datum marker visible, just numbers.

The marks are, as I said, used to enable the flying off platform to be brought into the wind. The wind across the deck is best measured from higher up and the information passed to the gun crew to traverse the turret. The markings would be visible to the officer taking the wind direction to ensure that it lined up with his orders.


I have trawled the web and found some pix
1. HMS Benbow with framework for ramp in place.
2 and 3 - USS Texas.

This thread is the first time I have seen the explanation given by Malcolm G. Most references (eg Norman Friedman Naval Firepower (Barnsley: Seaforth Publishing, 2008)) explain the markings as I have described in this thread. Is there a reference to the relationship with flying-off activity?


There are various photos showing the markings on turrets with no flying-off platform - eg "A" and "Y" turrets on HMS Centurion in 1918 (https://www.iwm.org.uk/collections/i...ject/205196616). Markings would not need to be on every turret - just one at each end of the ship, visible from the next astern (or ahead) in the battle line - which is where such concentration firing tactics were intended to be used. The datum would be the ship's fore-and-aft line, and ideally the ships would be in line ahead - or at least would know the inclination of the ship whose turret bearing was being read - with good optics from a position in close line of battle.


Incidentally, I've not seen a photo of Benbow with markings on "Q" turret (not "P" - only ships with two midships turrets usually referred to one of them as "P").

Sorry, I cannot give references for my information. I think it may have been a library book and the last time I used a library was over 30 years ago.
Anyway, it was ‘explained’ to me some time ago and made abundant sense at the time, it still does.
It, like much other pre-internet info, remained to the back of my mind until triggered by the OP question.
It seems that my information source may have got that wrong - I had better delete that ‘brain file’.
The picture of HMS Centurion seems to put the lie to that idea, unless anyone else wants to join in.

Yes I typed P, should have been Q. - same part of ship, different ends of the keyboard. Oops.

Just a further thought before I shut up -
Maybe the pre-existing concentration bearing marks were adopted for use when flying off platforms were introduced. That might fit.

Thanks to all for their insights.