Length 323.8 ft. Breadth 34.8 ft Depth 26.2 ft. Gross tonnage 2078
Purchased in 1896 for cable work, refitted and subsequently renamed. Based at Le Havre and used for North Atlantic repairs.
THE FRENCH CABLE STEAMER "PORTENA."
Messrs. Johnson and Phillips have just completed a cable steamer equipment to the order of the Compagnie Française des Cables Télégraphiques, making the third carried out by this firm within twelve months.
The work consisted of transforming a merchant vessel into a cable-laying and repairing steamer; and, although the vessel was not a new one, it adapted itself fairly well to the purpose, especially as regards the cable tanks, though it had high forecastle bridge and poop decks, and a comparatively small beam—viz., 33ft.—while it was 320ft. long.
The picking-up and paying-out machine was built very much on the lines of that for the steamer "Tutanekai," lately fitted by this firm for the New Zealand Government, but was much more powerful, being equal in strength to that recently fitted on the s.s. "Okinawa Maru" for the Japanese Government. Owing to the vessel having a high forecastle and bridge deck, it was necessary to erect this machine on the upper deck, and therefore it had to be self-supporting. For this reason, the frames of the machine, which were constructed of steel plates and angles, were tied fore and aft by strong wrought-iron diagonal stays, whilst additional stays were fitted in the nature of flat and angle bars; and various fixed shafts were also utilised for this purpose.
The method of securing the machine in the vessel was a very rigid one. Channel-bars 12in. wide were bedded on to the steel deck, so as to present a perfectly level surface, and the machine was levelled up on this by means of cast-iron wedge chocks, large pitch-pine baulks being fitted between and below the beams under the deck. The deck itself was stiffened by two plate girders 2ft. deep at centre, fixed underneath, right across the vessel, and attached to the shell plating; and these girders, and the deck beams under the gear, were stayed by stanchions right down to the keel and floor of the vessel. This made a splendid job, as even with the gear running at full speed, not the slightest vibration could be felt at the trial.
The gear is driven by a pair of horizontal engines, having cylinders 15in. diameter by 15in. stroke, which, running at 220 revolutions per minute, are capable of developing 210 B.H.P., with steam at 70lbs. initial pressure. The engines are fixed at the after end of the machine, and over them is erected a platform, from which the attendant can work and regulate the whole of the machine, the stop valve, hand wheel, reversing lever, drain cocks, main brakes, draw gear, brakes, and water service, all being within easy reach.
View of the Cable-Laying Gear on the s.s. ”Portena”
The dirty state of the ship, as shown in the engraving, is eloquent of the condition following the stowing of cable into the tanks in bad weather; the whitewash off the cable playing sad havoc with the appearance of the deck and gear.
As in other gears now made by this firm, the parts are constructed mostly of steel, to ensure lightness and strength. The total weight of this machine is 23 tons. The main drums are internally geared, and a rim is cast on the brake, so that the drums can revolve under the control of the brake independently of any other gear. The geared pinions are made to draw out of gear when not required for working, so as to avoid rattling. The “hauling-off” gear is driven by special silent pitch chain when picking up, but when being used as “holding-back” gear for paying out, the sheave (which also has a brake rim cast on), is arranged to run loose on a sleeve, being controlled by its own brake. A small Worthington pump is provided on the platform to work the water service, which is fitted to all the brakes.
A special feature of the main brakes, which are actuated by screws, is that they are worked through worm-wheels and worms so as to give finer adjustment for paying-out, as well as great power for holding. It will be readily seen that with the intervention of the worm-wheel and worm, a very fine movement of the brake screw can be obtained with very little power exerted at the hand-wheel on the worm-spindle; and when it is necessary to release or apply the brakes quickly, it is only necessary to spin the hand-wheels round two or three turns, which is readily done, as they work so easily.
The bow gear consists of three steel sheaves, running loose on a steel shaft, which is carried in dead bearings attached to steel girders, which are very rigidly built into the head of the vessel, considerable alterations having to be done to this part to make it suitable for the bow gear. The plating of the ship is made up to the girders, and “whisker guards” give it a very neat appearance. The stern gear consists of one steel sheave running loose on a shaft and carried on a pair of steel girders secured to the poop deck.
The dynamometers (of which three are supplied) are of extra heavy pattern, having two cylinders each, which act as dashpots, an adjustable byepass being provided between each cylinder by means of pipes and cocks, so as to steady the movement of the dynamometer sheave.
Owing to the vessel having wells between the forecastle and bridge deck, and bridge deck and poop, it is necessary to provide special leads for the cable, and these consist of strong cast-iron bases secured to the upper deck, and having a wrought-iron tube vertically in their centres which are adjusted in height; and the usual deck lead, consisting of base-plate with rollers and guards for cable, were carried on top of these. Where the leads can be fixed close to the deck the usual pattern of lead is supplied.
Tho cable coming from the after tank to the cable gear is arranged to pass through the alley-way, under the bridge deck, and for this purpose about 80ft. of troughing was supplied, fitted with bell mouth leads at intervals. The tanks were fitted with the usual arrangement of bell mouths and crinolines.
A “Lucas” steam sounding machine was fitted on the after end of the poop for taking deep soundings.
The outfit of grapnels includes Mr. Claude Johnson’s mud and rock grapnels, which we have before described, the former having flat steel prongs, which offer very little resistance to the mud, and the latter having prongs held in position by spiral springs, which allow them to recede under the protection of an annular conical shield when they come against any immovable obstruction; but owing to the special arrangement of the fulcrum of the prongs, only a very slight movement is necessary to ensure this, so that if the cable has already been hooked there is no risk of losing it.
The vessel is fitted throughout with electric light, the generating plant being in duplicate, and each set capable of maintaining 150 16 c.p. lamps continuously. There is also a large Admiralty pattern projector, 20in. diameter, with mirror, and an arc light for the rigging, as well as mast and side lights and deck clusters for the deck when working the cable. The dynamos are of Johnson and Phillips’ two-pole inverted pattern, compound wound, having an output of 140 amperes at 60 volts when running at a speed of 300 revolutions per minute, and they are direct coupled to Robey engines.
The contract of the whole of the work was placed with Messrs. Johnson and Phillips, including the alterations to the vessel, which were most extensive; but this part of the work was executed by Messrs. Dunlop and Co., of Port Glasgow, under contract. The fore and aft holds had to be entirely cleared out in order to allow for water ballast tanks and the cable tanks being fitted. The work of building in the ballast tanks was very difficult, owing to the construction of the hull, and it involved a great deal of work, especially aft, where it was necessary to renew the whole of the tunnel, which necessitated the lifting of the propellor shaft and the after mast. The cable tanks were built directly on top of the ballast tanks, the forward tanks being 30ft. diameter, 18ft. deep, and the after tanks 29ft. diameter, 14ft. 0in. deep respectively. The tanks were firmly secured at the side to the hull of the vessel by vertical gusset plates, and to the deck by means of strong steel stringer plates. A large Worthing pump is fitted in the engine-room to work the ballast and cable tanks, and this also has connections to the main condenser, so that can be used as an auxiliary circulating pump, for use when the main engines are stopped, or moving slowly, and the cable gear engine is exhausting into the condenser.
A large saloon was fitted up under the poop, the total length being 54ft., and it contains 12 cabins of various dimensions for captain, officers, electricians, and engineers. The main saloon is 54ft. long by 11ft. wide. New accommodation for the crew and cable hands (50 in all) was also fitted up. A portion of the bridge deck had to be cut away, to allow for a hatch over one of the cable tanks, and some existing cabins had to be dismantled and formed into a testing room.
Part of the forward hold under the cable gear was fitted with platforms and cones, on which to coil the grapnel and buoy ropes. There are four of these platforms, two on port side and two on the starboard side, one of each being on the floor of the vessel, and the others on the level of the lower deck and immediately over the lower ones. The cones of the upper ones are fitted with bell mouths in the centre, so that the ropes can be taken right through them to the lower platforms, and there are similar bellmouths in the upper deck, immediately under the holding back sheave of the cable gear, so that the rope cm be led directly on to them. The necessary ladders are provided for access to these platforms. A new capstan windlass was supplied and fitted in the forecastle, and a new steam winch forward.