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Captain M'Killop's flexible cofferdam

The Royal Navy  

In 1863 Captain Henry Frederick McKillop invented a "flexible cofferdam" to enable cleaning of the hull of iron ships in the water. The following extracts from the Naval Intelligence column of the Times newspaper refer to this invention.

Extracts from the Times newspaper
Fr 19 June 1863The iron frigate Recruit, 6, 150-horse power, has nearly completed her heavy repairs at Chatham dockyard, which have been in hand several months, and will be ready for floating out of dock during the ensuing spring tides. The starboard side of her hull has been coated with one of the numerous new anti-corrosive substance, for the prevention of fouling in the bottoms of our iron ships, which are constantly being brought under the notice of the Admiralty. The composition applied to the bottom of the Recruit is the invention of Mr. Crispin, but instead of being placed on the iron in its original state, the ship’s bottom was previously covered with red lead, which is stated to be detrimental to the efficacy of the new composition. It has long been matter of surprise that none of our eminent chymists have directed their attention to the preparation of a substance which will effectually prevent fouling, the compositions brought under the notice of the Admiralty up to the present time being more or less failures. Both fortune and fame are to be made in the discovery of an effecfual anti-fouling composition for iron ships’ bottoms.
Tu 6 October 1863By direction of the Admiralty the apparatus invented by Captain H.F. M'Killop for cleansing the bottom of iron ships from seaweed and other marine incrustations, is to be tried at Chatham dockyard. Their Lordships have directed the first trial to be made on the bottom of the iron paddlewheel steamer Recruit, which is to be placed at the disposal of Captain M'Killop. The chief merit of the invention lies in there being no necessity for placing iron ships in dock every time their bottoms require cleansing. If the trials ordered to be made should prove satisfactory the invention will prove of the greatest possible benefit, as the only drawback to the use of iron ships for lengthened voyages undoubtedly is to be found in the necessity which periodically exists for placing them in dock to undergo the cleansing process. An examination was yesterday made of the bottom of the iron steamer Recruit by some of the staff connected with the master shipwright's department, when it was found to be exceedingly foul, many of the weeds which thickly cover her bottom being from one to three feet in length, while the other marine incrustations were likewise found to be very thick. The bottom of the Recruit had been payed over with one of the anti-fouling compositions, none of which have proved better than the Admiralty mixture of coal-tar and naphtha. After the Recruit has been treated according to Captain M'Killop's method she will be placed in dock in order to ascertain the extent to which her bottom has been cleansed.
We 14 October 1863An official inspection was yesterday made by the authorities at Chatham dockyard, on the part of the Admiralty, of the iron paddlewheel steamer Recruit, 6, 150-horse power, which was placed in No. 3 dock on the previous afternoon to enable a survey to be made to ascertain the results of the trials with the invention by Capt. H.F. M'Killop for cleansing the bottoms of iron ships afloat, These, by direction of the Admiralty, were ordered to be tried on the Recruit, which was placed in the hands of the inventor for that purpose. During the time the Recruit was in dock at Chatham, fitting for commission, her port side was paid over with the anti-corrosive composition by Mr. Hay, the Admiralty chymist, and on her starboard side was applied a new auti-fouling mixture, which had been submitted to the Admiralty by the inventor, Mr. Crispin. Both compositions - as, indeed, has been the case, more or less, with every invention of the kind hitherto brought under the notice of the Admiralty - have turned out to be complete failures, as, on the water being pumped out of the dock in which the Recruit had been placed every square inch of the surface of her hull below the water-line was found thickly coated with weeds, sea grass, barnacles, and various kinds of animalcule. The appearances of the two sides of the vessel were, however, very different. On the starboard side, to which Mr. Crispin's invention had been applied, the entire surface was covered with grass, about a foot in length, with which were mixed thousands of sea worms and barnacles. A minute examination led to the discovery that every portion of the composition had been eaten away from the iron-plates, leaving nothing but the coating of red lead applied by the dockyard workmen. On the port side Mr. Hay's composition was found to be still adhering to the iron-plates, which were coated over the length of the vessel with a kind of fibrous seaweed, from one to two or three inches in length, and swarming with small shell fish. In some parts of this portion of the vessel's bottom the weeds were longer and more matted than on the starboard side, while the barnacles here were also very large, the composition being completely penetrated, and the iron-plating exposed. Altogether the bottom of the Recruit, which had only been 12 weeks out of dock, was more thickly covered with marine formations than many iron vessels which had been 12 months afloat. Only a portion of the vessel's hull was selected by Capt. M'Killop to be experimented upon, extending about 12ft. on the aft side of each of the sponsons. The plan adopted in removing the fouling from iron ships is to sink a kind of large tarpaulin, of about 20 feet in width, and of sufficient length to be passed completely under the vessel's keel, and brought up on the opposite side. The four sides or edges of the apparatus are made air-tight, and on being filled with air acquire a buoyancy which makes it cling to the vessel with great force. A mixture of creosote, lime, and some other substances being spread over the centre of the tarpaulin, the whole remains under water, and in the course of some three or four hours the mixture being acted upon by the water destroys every portion of the growth on the ship's bottom. Although Capt. M'Killop's invention had succeeded in removing a considerable part of the incrustations on the sides of the Recruit, yet the cleansing process was only partial, the keel, especially, showing a vast accumulation of seaweed and barnacles altogether untouched. The opinion pronounced by the dock-yard officials was unfavourable to the invention, but provided the apparatus can be easily applied there appears to be no reason why it should not, in a measure, answer in the case of iron ships taking a long sea voyage, and, therefore, unable to be docked, excepting at distant intervals. On the other hand, it would be necessary to ascertain whether the powerful composition of creosote and lime has any, and, if so, what effect upon the plates of iron ships. It should be stated that Captain M'Killop considers his invention to be more successful in realizing the object sought when tried at sea than in harbour, as the passage of the vessel through water would more effectually wash off the accumulations removed than can be effected in the case of a ship moored in a river or harbour.
Ma 19 October 1863An official report has been made to the Lords of the Admiralty of the result of the recent experiments made at Chatham by Captain M'Killop, R.N., with his canvas machine for cleansing ship's bottoms afloat. The results quite justifies the recommendations. The simplicity and portability of the machine, as well as the moderate cost, are further recommendations in its favour.
We 4 November 1863The iron screw troopship Adventure, 1,794 tons, 400-horse power, Commander T.B. Lethbridge, will on her arrival in Chatham harbour, be placed in the hands of Capt. H.F. M'Killop, by direction of the Admiralty, for the purpose of enabling Capt. M'Killop to institute some experiments with the flexible coffer dam, or portable dock, cleaning machine, submitted by him to the Admiralty, and with which the inventor undertakes to demonstrate the practicability of employing men in removing the marine and other formations on the bottoms of iron ships without any necessity for their being placed in dock for that purpose. The Adventure has been ordered to be operated upon at Chatham, because iron ships are found to foul more rapidly in that harbour than at any of the other naval ports.
Tu 8 March 1864The iron paddlewheel steamer Lizard, employed in harbour duty between Chatham and Sheerness, has been selected by the Admiralty to be experimented upon with Capt. M'Killop's coffer-dam, or portable dock, in order to test the merit of that invention. The Lizard having been placed on the gridiron to ascertain the state of her bottom will be floated into the steam basin to-day, should the gale at all moderate, and will be placed in the dock to-morrow in order to save the spring tides.
Fr 9 November 1866A portable cofferdam, intended for use on the bottoms of ships, to examine a valve or injury below the water line, and avoid, where possible, the necessity for placing the vessel in dock, the invention of Capt. H. F. M'Killop, R.N., is being practically tested at Portsmouth dockyard, under the superintendence of the officials there, by order of the Admiralty, and yesterday met with its first decided success on the bottom of the paddle steamship Terrible, Capt. Commerell V.C., now refitting in the ship-basin of the yard. The upper Kingston valve required examination, and the portable cofferdam was lowered into position over it yesterday morning in order to thoroughly test its efficiency. In the forenoon the attempt was not successful, owing to some error in fixing the pontoon, which prevented a clearance of the water from the interior of the pontoon. A second attempt in the afterpart of the day, however, proved completely successful, the pontoon being pumped out clear, and a perfectly dry dock formed on the ship's bottom in which the workmen could examine and repair, if found necessary, the Kingston valve. Although a great success has been thus attained with Capt. M'Killop's very useful invention in the experimental trial of its capabilities made yesterday afternoon, the whole apparatus is undoubtedly capable of being greatly improved upon in many of the details of its fittings. It is obvious also that if the invention becomes an established success in its application to the bottoms of ships, it also becomes at once applicable for the examination and repair of the submerged walls of docks or basins without emptying them of their water or removing their shipping. Capt. M'Killop's cofferdam resembles in size and appearance one of the paddlebox boats carried by the Terrible, but with one end cut off. It is formed of semi-circular iron ribs, at fixed distances apart, covered with waterproof canvas and fitted on a flexible iron frame. This iron frame is covered with an air collar or cushion, and this latter is also covered, as a protection, with thrum matting. The cofferdam is lowered into the water with, if we still consider it as a boat by way of illustration, the cut-off end of the boat uppermost, and as it descends the water, of course, presses the frame with its air cushion and thrum-mat facing against the ship's side. When lowered to a sufficient depth, the hose from the ship's deck-pump is passed into the dam through its open end projecting above the level of the water, and then, if the dam has been properly fixed and other conditions are favourable, the water is pumped out from the inside of the dam, increased pressure comes upon its exterior, jamming the framing or edge of the boat's gunwale closer upon the ship's side with its air cushion, &c., and a water-tight joint completes a dry dock in the water and round that part of the ship's bottom requiring examination or repair. The apparatus tried yesterday weighs, when dry, about 20cwt., and, having a jointed frame, it can readily be taken, to pieces and stored away in a very small space. It has been constructed of dimensions suitable for its use on a ship drawing 17t. of water. The length of one of these portable cofferdams taken to sea by any ship must, of course, depend upon the ship's depth or draught of water.


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