Isherwood and the longitudinal framing system

An important but not that well-known figure in the history of naval architecture, Sir Joseph William Isherwood, patented a practical means of implementing longitudinal framing in ship construction in 1906.

Born in Hartlepool on 23 June 1870, the son of a grocer was educated locally and at the age of 15 he entered the drawing office of the Hartlepool shipbuilders Edward Withy & Co. He served in several departments in that firm before becoming  a ship surveyor with Lloyd's Register of Shipping in 1896. It was here that he conceived the so-called Isherwood System. After a brief spell as a director of the Middlesborough shipyard R Craggs and Sons, he set up his own practice as a naval architect in London. 

The first ship to be built using the Isherwood system, the tanker Paul Paix of 1908 (Credit: teesbuiltships.co.uk) 

Earlier forms of alternate framing  

Longitudinal framing had, of course been used occasionally in the past. For example, Brunel’s Great Eastern, designed by naval architect John Scott Russell, incorporated this arrangement. She was built with longitudinal girders spaced 12cm apart from the keel to the lower turn of bilge and then to the lowest deck at about 25cm spacing. The girders were covered by an inner layer of plating and the framing system was supported by numerous transverse watertight bulkheads. 

Even earlier, when ships were being constructed in wood, Sir Robert Seppings (1767-1840) who served as the Royal Navy’s Surveyor of the Navy (the navy’s naval architect) between 1813 and 1835, introduced a system of iron diagonals to strengthen the transverse framing and enable longer vessels to be constructed. 

Isherwood’s idea

What Isherwood did was to develop a practical ship construction system in which large, widely spaced transverse frames, or webs, would be used in conjunction with light, closely spaced longitudinal members. This method gave a ship much greater longitudinal strength than in vessels built in the traditional method where a series of closely spaced transverse frames are fitted from the keel to the sheer strake with corresponding deck beams.  

This resulted in less iron and more steel being used in a vessel’s construction, reducing structural weight and making for a stronger hull. This more efficient design offered an increased payload within the same parameters. 

Isherwood’s ideas were particularly applicable to tankers where traditionally designs had focused on maintaining transverse strength at the expense of longitudinal strength and caused cargo leakage in bad weather. As tanker sizes grew, this problem became increasingly severe, and builders and owners progressively switched to Isherwood’s answer. 

Typical hull structure for a tanker featuring longitudinal framing (Credit: Merchant Ship Construction, IMarEST) 

From concept to construction 

The first vessel to be constructed using this system was the tanker, Paul Paix. Built by R Craggs and Sons of Middlesborough in 1908 for Lennard's Carrying Co Ltd, she had a cargo deadweight of 6,600 tons and was 107.6m long. Construction featured two transverse webs between consecutive bulkheads and a series of longitudinal girders. Paul Paix proved highly successful in service and was only broken up in 1935 in Pula. Subsequently, many countries around the world adopted Isherwood’s patent.  

A later vessel built to the Isherwood System was the 1910-built 10,650-ton deadweight coal and iron ore carrier, Storstad, owned by Norway’s A F Klaveness and Co. At the time she was the largest vessel yet built with the system. In April 1914 she was in collision with the liner Empress of Ireland which subsequently sank with the loss of 1,012 lives. Storstad remained afloat, it was said, because of her construction arrangement vindicating Isherwood’s ideas. By 1937 when he passed away, some 2,500 vessels had been constructed around the world using the system. 

Continued contribution

In later years Isherwood made a number of further contributions to naval architecture, including the design of torpedo-proof cargo vessels during World War I, and the Arcform hull design, which he introduced in 1933. The latter was designed to improve fuel consumption and 50 ships were built to the concept between 1933 and 1954. He was also a valued member of Lloyd’s Technical Committee for many years.  

In June 1921 Isherwood was made Baronet Isherwood of Raggleswood (the name of his house in Chislehurst, Kent) by King George V for his invention. He died of pneumonia on 24 October 1937 at his London home and was buried in West Acklam, Middlesborough. 

John Barnes is a journalist and author and former editor of Marine Engineers Review.