The "K" Submarines

by Lieutenant H. M. Fardell, RN

This article is from The Naval Review, volume VII Number, 1919. Traditionally, the authors were anonymous, but the author was identified thanks to the list published by James Goldrick in Mahan is Not Enough- the Proceedings of a Conference on the Works of Sir Julian Corbett and Admiral Sir Hubert Richmond (edited by James Goldrick and John B. Hattendorf, Naval War College Press, 1993).

Almost 100 years on, one suspects that the author was perhaps overconfident in the damage that a flotilla of "K" boats could do in a fleet action, but as he stresses, that was their raison d'etre, and had such a battle taken place, they might well have proved effective. As classic patrol submarines, of course, they were somewhat less than successful.

Service in the "K" boats is usually avoided for the rather vague reason that "K" boats are no good; an entirely mistaken idea, as the writer attempts to show in this essay.

The "K" boats were designed when the need for submarines capable of working with the battle fleet was first realised, and were laid down early in 1916. The appreciations of the tactics at Jutland showed how imperative it was to have "fleet submarines."

The first and principal essential required for this work is sufficient speed to be able to keep the speed of the fleet in most weathers; and to get this quick-diving qualities had to be sacrificed in the same way that armour and guns were sacrificed in battle cruisers.

Remembering that speed is all important, it is seen that the "K" boat design is highly successful, a speed of 24 knots being obtained, which is sufficient to allow for 20 knots being kept up in moderate weather.

Critics who maintain that in bad weather the speed must be reduced to a crawl have scarcely studied the question from a large enough standpoint.

In a case of urgency a "K" boat can keep up a speed of 19 to 20 knots in weather that would force destroyers to reduce to 15 knots or break up; admittedly, damage to the bridge and superstructure must be expected, and the stokers in the boiler-room would suffer severe discomfort from water pouring down the air intakes and funnels, sometimes extinguishing the fires (which can very quickly be relighted), but the main point is that the -inch hull will not suffer from any amount of overdriving in bad weather like the thin plating of a destroyer; so unless the commander-in-chief was willing to leave his destroyers he would never have to outpace his "K" boats.

(Note. - It is quite usual for stokers to go on watch in the boiler-room wearing oilskins, sou'westers and sea boots.)

Having this speed makes it possible for "K" boats to get into an attacking position before the battleship duel begins - no other submarine could do this; those that left harbour at the same time as the fleet would not arrive till the action was over, and those already on patrol near enough to see the enemy would not have sufficient speed to place themselves in an attacking position unless by chance they were already there.

Given the necessary speed, the other essentials are as large a number of torpedo tubes as possible (which was fulfilled by building four bow and four beam), and a good tactician as captain (S) for the flotilla leader in a light cruiser. (During the war the battle fleet submarines flotilla was fortunate in having an exceptionally able tactician as captain (S).)

In the battle formation of the Grand Fleet, during the war, the "K" boats were stationed 10 miles ahead of the main battle squadrons with various light forces spread out ahead of them to a distance of about 25 miles.

On the screening forces sighting the enemy and reporting by W/T the captain (S) had to manoeuvre to place his flotilla ahead of the probable course of the enemy battle fleet, and, if possible, slightly on the side furthest from our own heavy ships.

When in position the boats were detached in pairs to act independently; generally, at least three pairs could be counted on as being present, the distance between them varying according to circumstances to ensure that two pairs got in their attack even if the enemy made a considerable alteration in course.

The boats of a pair then separated to about one mile, by previous arrangement, to avoid the chances of underwater collision, and prepared for diving. When the leading enemy ships were about four miles off the boats would dive, taking at most five minutes, as they would be already trimmed down; and it must be remembered that the conning tower, end-on, is very difficult to see even in calm weather at two miles, and in action the firing of our light forces would probably distract the attention of enemy look-outs sufficiently to ensure the "K" boats being unobserved.

After diving the range of action is very much restricted, and unless the captain (S) had slipped the boats in the correct positions the enemy would pass out of range of the boats, which can only proceed at seven knots when submerged.

Should the boats be in the correct position, the action radius of seven knots for about one hour would be more than sufficient, as the high speed would not be much required, and long before the hour had elapsed the action would have passed over the horizon.

Unless the enemy turned 16 points shortly after the "K" boats dived, they must pass close to them, or else turn away towards our own battle fleet, either procedure suiting the commander-in-chief whose tactics would be formed accordingly.

Taking the first case of proceeding on the same course or turning slightly away from our battle fleet; the "K" boats would find themselves in an ideal attacking position from which their experienced captains could not fail to obtain at least 60 per cent. of hits and probably would obtain 90 per cent.

Imagine 29 torpedoes hitting before the gun duel had even begun!

If the enemy turned towards our battle fleet, or turned 16 points when 4,000 yards away, the submarines could still fire "browning" salvoes of torpedoes set for 19 knots, of which, by the laws of chance, at least 25 per cent. would hit, and several ships would probably be damaged enough to be unable to keep in the line.

Even if the submarines were sighted during their attack only capital ships could ram them if at periscope depth, and in the unlikely event of destroyers carrying depth charges during a fleet action, it seems improbable that many boats would be sunk before they had time to fire their torpedoes.

The time taken to reload the tubes makes it unlikely that many "second shots" could be fired before the enemy had passed out of range; the boats would then, after attacking stragglers, concentrate on a pre-arranged line off the enemy coast to intercept returning ships.

* * *

Critics also deride the usefulness of "K" boats on patrol, forgetting that to be present in a fleet action is the primary cause of their existence - patrols were a secondary consideration introduced chiefly tor exercising the boats, which were found to suffer from numerous minor breakdowns after too long a period in harbour, and from this point of view patrols were most beneficial, the average number of effective boats being nearly doubled after a few weeks of patrols. The duty of a "K" boat on patrol is rather different to any other submarine on look-out duty.

Should an enemy vessel be sighted the "K" boat reports at once, and probably has finished her signal and "trimmed down" before she is seen herself; and can then get to periscope depth in four minutes, her external hull being underwater in less than two minutes; the chance of a shell damaging her inner hull when in this position is extremely remote, especially at short range when shells would burst, or ricochet, on the water or her outer hull. The superstructure might be shot to pieces without doing more than flooding the conning tower and lower funnels, which could easily be adjusted for in the trim.

The objections to the discomforts of living on the boat, and of being "one of a crowd," instead of having a little action alone, and consequently reaping all the credit, are both obvious and true; but the writer hopes this essay will save "K" boats from a little of the unmerited ridicule heaped on them by so many submarine officers who, in many cases, have never seen one, and have no conception of their duties and tactics in action.

To sum up in brief the use of "K" boats, it may be said that:- As surface ships, they can get to the scene of action and choose their attacking position, after which they have, except for a small difference of speed, the same chance of making a successful attack as any other submarine in the same position.

Last Updated: 4 November, 2001.

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