Trans RINA, Vol 152, Part A2, Intl J Maritime Eng, Apr-Jun 2010


widely adopted with a higher steam pressure of around 60 lb/sq in (4 bar) and more reliable boilers. SFC was reduced to around 2 lb coal/hp-h, which translated into more cargo for the same fuel, or less fuel with the same cargo, or longer voyages, as well as reduced fuel cost and fewer bunkering calls. A lot of bunkering coal exported from Britain was carried in sailing ships to areas where there was none or the local coal was of poor quality. The high freight costs of 20-40 shillings per ton (£1.00-2.00) resulted in the price of coal in say Indian Ocean ports being three or four times the UK price of under 10 shillings (50p) per ton. The plethora of previous boiler designs, box, haystack, locomotive etc, gave way to the cylindrical ‘fire-tube’ boiler, often called a Scotch boiler. New stronger designs of furnace in which the coal was burned reduced the risk of collapse and scalding of the stokers.


The compound engine soon gave way to the more efficient triple expansion engine in bigger ships from about 1880. With higher pressures of about 150 lb/sq in (10 bar) expanding through a high, intermediate and a low pressure cylinder, SFCs were reduced to about 1.5 lb coal/hp-h (13% efficiency). Such


higher pressures


required very thick iron plates in large boilers, so boilers began to be built in steel from that same date, requiring plates about 20% thinner. Siemens-Martin open hearth steel of consistent quality became available from about 1878, with production rapidly expanding. The transition from iron to steel hulls took only ten years. Small quantities of cast steel had been available from the late 1850s but its high price of around £20 per ton compared with £9 for wrought iron limited its use to lightweight vessels like river steamers and blockade runners for the American Civil War, although it had been used to build masts and spars


of lighter topweight. But bulk


manufacture in Scotland and north-east England soon reduced the price of steel to about £6 per ton, even below that of iron. Its greater strength reduced steelweights by around


15% and its greater ductility improved


survivability in the event of grounding or collision, while the larger size of plates possible (up to 8ft wide in place of 4ft) reduced riveted joint length and construction cost.


Figure 6. The steam trawler was introduced in the late 1870s, enabling large quantities of fish to be landed and transported in ice by rail


early tankers: 4000dwt Minister Maybach was built by them in 1887.


The 1880s also saw the birth of two specialist ship types, a trend which continues to this day – the tanker and the refrigerated ship.


Previously oil had been carried in


wooden barrels or metal cases, prone to leakage and slow to load and discharge. The 3200ton deadweight 8knot Gluckauf built on Tyneside


in 1886 was the first


successful bulk oil carrier, stowing cargo within the hull itself, with longitudinal and transverse bulkheads, and with machinery aft, and its own pumping and piping system, a concept that endures to this day, although the ships are one hundred times larger and double the speed. Although there had been a few experimental refrigerated installations in sailing ships (surely not the ideal carrier), the first steam propelled fully refrigerated ships based on CO2 arrived in the early 1880s. These permitted the export of cheap frozen meat from countries like New Zealand and Australia, to feed the increasing urban populations of Europe as industrialization gathered pace. By the turn of the century, the steam trawler and ore carrier had been added, the latter especially on the Great Lakes.


to the growing urban


populations. By 1900 the UK was building about 200 such vessels a year. Smiths Dock then on the Tyne specialised in building fishing vessels – their Hawk of 1897 has bridge aft of the funnel.


Although the basic concepts of buoyancy and initial stability were well known in 1860, the calculation of large angle stability was onerous, yet capsizes of ships such as the ironclad Captain in 1870 had shown the need to do so. Fortunately Amsler came up


with his


mechanical integrator in 1878, a concept later extended to the integraph, which allowed bending moments and shear forces to be calculated for demanding vessels like large passenger vessels


or warships. Previously


Figure 5. The first oil tanker to have all the features that would become standard – cargo contained in the main hull by longitudinal and transverse bulkheads and engine aft - was built on the Tyne in 1886. Armstrong, Mitchell (later Armstrong, Whitworth) was the major builder of


©2010: The Royal Institution of Naval Architects


calculations of midship section modulus had been based on approximations like Max bending moment = k x Displacement x Length,


scantlings were based purely on tables related to tonnage or main dimensions in Classification Society rules.


A - 53


although for most ships, It


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