Stokes Bay

 

 

The Torpedo Attack on the Oberon at Stokes Bay

 

Oberon was an iron paddle sloop built in 1864. She was used as a gunnery target from 1870 In 1874 she took part in a series of trials during which 600lb of gun cotton was exploded near her. She survived the first six trials undamaged but during the seventh trial when the charge was exploded underneath her in May 1875 she was badly damaged internally and her back broken. The charge was fired electrically from the shore at Stokes Bay causing the vessel to be lifted out of the water. She was raised from the Hamilton Shoal at the mouth of Portsmouth Harbour off Haslar Hospital in November 1875 using an experimental Russian 'Popoff' airbag, a 22ft long bag made of a combination of cordage, canvas and vulcanized rubber with a displacement of 60tons. She was repaired to be used for further experiments and was sold in 1880.

 

 

The First Oberon Experiment

The first trial was reported in The Engineer Aug 14 1874 as 'The Oberon Experiments'.


At Stokes Bay on Thursday August 6th took place under the direction of the special committee of which Sir W. Jervois is president the first of a series of experiments whose importance as bearing on the question of the defence of our harbours and roadsteads can be hardly over-estimated. The Oberon, as most of our readers are aware, has been long in preparation for a course of attack by submarine mines, to be carried on until it terminates in her destruction, the object being to test the effect of such mines under various circumstances on the bottoms of our men-of-war as at present constructed, and so to learn exactly how to place our charges to the best advantage, as well as to ascertain what constitutes a bar which ships cannot cross without being destroyed.

 

To carry this out the Oberon has been provided with sides and bottom corresponding exactly to those of H.M.S. Hercules and also with a condenser taken form her Majesty’s ship Octavia. The system on which she is attacked we need hardly say, is to begin with comparatively distant charges and gradually to approach nearer to the vessel carefully investigating the effect in each case so as to obtain the maximum amount of information that can be afforded by so costly an experiment. It has been decided by the Torpedo and Obstruction Committee to adopt the charge of 500lb of compressed gun-cotton, as what we may call the normal one for the conditions most commonly occurring. It happens that the depth best suited to give full effect to this charge is about 8 fathoms of water and this is about the depth most commonly found in the passages to be defended. Five hundred pounds of gun-cotton, it is to be borne in mind, corresponds to two thousand pounds of powder.

 

The Oberon Experiment Fig 1

 

 

On 5th August this charge was with considerable difficulty, owing to the rough weather, placed at about 100ft. form the vessel’s side on the bottom at a depth of 8 fathoms of water, its place being marked by a buoy (fig2). The Oberons circumstances were as follows: The inlet and outlet valves of her condensers were left open the Kingston valve of her feed-pipe was closed. The water-line was 2in higher than the top of her condenser. the original weight of her hull before fitting her with special bottom was 590 tons as now fitted it is 920 tons. Her cables and condensers may be taken as about 30 tons. Her starboard side has forty-four crusher gauges (a-a-a Fig 2) fitted to it. Each crusher piston is 2/3 square inch in area, and behind it is a lead pellet hardened with antimony 1/2inch long and 1/12 inch in sectional area. Over each side of the vessel were suspended by 3inch ropes 12ft long six 18-ponder shot, each fitted with a crusher gauge (b-b in fig 2) having a piston of smaller weight than those of the Oberon crusher gauges, but in other respects similar.

 

The 500lb charge of gun-cotton in the mine was saturated with fresh water in a service water-tight iron case. Ignition was effected by means of two Abel detonating fuzes placed with two dry 9oz discs of cotton in a waterproof bag. We believe we are correct in saying thet the circuit used in previous experiments was employed in this case also; that is a circuit was provided for testing, being constantly open, passing through a copper-plate into the water. This circuit has a point of great resistance at the fuze and cannot act strongly enough on the electro-magnet to bring the powerful firing battery into action. this latter is brought into play, however, in a service mine, either by a circuit closer being tilted, which opens a circuit momentarily where there is very little resistance, and which, therefore, has strength enough to magnetise the electro-magnet or by the act of an operator on shore. It was the latter arrangement only that was applied on this occasion.

 

The firing took place from Fort Monckton, being directed by Captain Abney, R.E. who generally performed this duty so as to be able to arrange to take an instantaneous photograph of the column of water thrown up. on this occasion, we believe, two were got at successive instants with great success.

 

The Oberon Experiment Fig 2
The Oberon Experiment Fig 2

 


Fig 1 shows a view of the column of water thrown up by the explosion of the mine taken from a boat on the same side of the vessel, that is the starboard side, which was towards Fort Monckton. Except the fact that the charge is a formidable one, the test was not a severe one. The general form of the column of water is itself an indication of the way in which a submarine charge acts. Water is easily displaced but it is incompressible; hence any lateral explosion is rigidly resisted, and a column of water driven upwards with very great violence as shown in Fig1. thus it is easy to see that a vessel’s safety is more affected by the horizontal than the vertical distance form the charge. It is also obvious that the water above the charge requires to be a certain depth in order to develop the full explosive power: this depth being, as we have said, about 8 fathoms for 50lb of cotton.

 

Fig 2 shows the horizontal distance of the charge and the position of the vessel, as well as a string of half shells containing Noble’s crusher gauges c c c at 28ft distance horizontally on the side of the charge remote from the Oberon, these being used in continuation of a course of investigation of pressures commenced by the Toredo Committee in 1873. The general form of the iron plate bottom of the Oberon is also seen as well as the condenser - d in fig 2 with which we have to do presently.

 

HMS Oberon Torpedo Experiments 1874 Raising the Oberon The Graphic Dec 4th 1875
HMS Oberon Torpedo Experiments 1874 Raising the Oberon 1875

 

The Oberon Toredo Experiments : The Graphic December 19th 1874
These experiments, which have been made off Fon Monckton at Portsmouth, on several occasions, have beem carried out for he purpose of determining how over an ironclad of the Hercules class can pass over an exploding torpedo without injury, and for this purpose the Oberon has been fitted up to represent a ship of the Hercules class. On one of the days appointed for the experiments there was a large assemblage of boats, steam launches, in as near a circle as was allowed. The explosive used was 500 lb. of damped gun-cotton confined in an iron case, and fired by two of Abel's submarine fuzes. When the torpedo was exploded, the Oberon was seen to upheave, and to heel over perceptibly, but she did not sink, and was presently towed into Portsmouth harbour to be docked and officially examined. She is one of the old obsolete paddle-wheels, and has her bottom encased with 15 inches of iron plating, coinciding with that of the Devestation Beyond the displacement of hatchways, coverings, water tanks, &c., and the starting of bull's eyes and deck planks, there was no serious damage done. The crew, which consisted of two sheep (saturated with red ochre to show, should they be jerked off their legs, the distance they were thrown) and six rabbits, were in no way hurt. They were placed below, to test the effect on animal life. After the explosion, the sea was literally swarming with fish, some dead and others stunned. The sight afforded no small amusement to people in boats. The first experiment took place on August 7th, when the torpedo was fixed 100 ft. hontontally from the ship's starboard beam. At each successive trial the distance was gradually decreased, 30 ft. being the nearest, as shown in the sketch marked " 5th Experiment. In the "6th Experiment," the Oberon was moored nearer the shore, so that the torpedo rested on the mud in about eleven fathoms of water. The difference between gun-cotton and gunpowder is, that where the latter forces its way upwards and slightly outwards, the former radiates from the centre with equal force in every direction, forming a circle, the upper segment of which is shown by the flattened dome of water which is seen in the first burst, and the force of the lower portion of the circle meeting with the resistance of the mud rebounds, forcing a huge column of water to a height of 250 ft., and followed by a torrent of earth. The Oberon was lashed from stem to stern with stout cables in order that she might be easily grappled in case she sank.

 

 

In 1875 more experiments on submarine mines were carried out at Stokes Bay, near to Fort Gilkicker as reported in The Times on June 9th.

 

The following is a detailed account of the interesting torpedo experiments which were made at about midnight on Thursday, at Portsmouth The object was to ascertain whether submarine mines could be rendered useless by having the electrical cable connecting them with the shore grappled by boats and cut by a diver A submarine mine was laid out off Gilkicker Point. It consisted of a 5001b buoyant charge with circuit closer and mushroom sinker It was moored in about 11 fathoms of water, the charge eight fathoms below surface, and the circuit closer so as to be concealed at all times of tide The mine was connected to Fort Monckton by a multiple cable and a branch cable from a junction boat at the mine. This part of the work was performed in the usual manner by the Royal Engineers The navy undertook the offensive part of the operation, the removal or destruction of the submarine defence, the exact position of the mine and cable being known to them. The time of the attack was kept secret, as were also the arrangements for the defence. Intelligence having been received at about 9 p m that the attack was about to be made, the garrisons of Fort Monckton and Gilkicker were on the alert A guard boat in charge of Captain Collings, R E, with a party of Royal Engineers, was despatched to the neighbourhood of the mine to give notice of the enemy's approach The Royal Artillery, under command of Major Ford, R A. were drawn up at Gilkicker to man the guns prepared for the defence. The detachment of Royal Engineers were served out with 10 rounds of ammunition and placed in readiness on the beach to repel the enemy's attack The alarm was given by the guard boat opening fire on the enemy boats, which were both soon heard. Parachute lights were then fired by the Royal Artillery, and the enemy's boats were clearly discerned. The guns and small arms then opened a deadly fire, and the parachute lights were continued to be fired at the enemys boats who did not Succeed in doing any harm to the submarine mine. Signal parties were placed m Fort Monckton and Gilkicker battery in such a way as not to be discerned by the attacking party, and messages were received from time to time as to the condition of the mine The signal apparatus used was the very convenient little home light apparatus lately introduced into the service and invented by Quartermaster Sergeant Walker, R E. The defence was under the direction of Major Stockley R E, the Superintending Officer of Royal Engineer Experiments at Stokes Bay, who has charge of the numerous and important experimental submarine defences, including the Oberon, which are daily being carried on under the direction of the War department, who are now fully aware of the growing importance of a properly organised force for the defence of the United Kingdom. The whole of the 35th Company Submarine Mines under command of Captain G M. Collings RE., with Lieutenants Chermside, Bennet and Knight are now quartered in Fort Monckton and employed exclusively on these important experiments. The result of Thursdays experiment is greatly in favour of submarine mines as a defensive weapon, and although the attack was led in the most approved way, and had the advantage of being under the direction of the most experienced officers of our navy in matters connected with torpedoes, Captain Singer, R.N, the president of the Admiralty Torpedo Committee, assisted by officers specially trained under Captain Fisher, R.N, they were not successful at destroying the submarine defences, although the means used for illuminating the Channel were very feeble in comparison with the electric light which would be made use of for this purpose in actual warfare.

 

 

 

 

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