Go back to article: Engineering and the family in business: Blanche Coules Thornycroft, naval architecture and engineering design

Blanche Coules Thornycroft and the application of engineering knowledge

Blanche was born in Hammersmith, London on 21 December 1873. Her parents were Sir John Isaac Thornycroft and Blanche Ada Thornycroft (nee Coules). Blanche also had four sisters, Edith Alice (1871–1959), Mary Beatrix (1875–1965), Ada Francis (1877–1965), and Eldred Elizabeth (1879– 1939), as well as two brothers. One of the brothers (Sir) John Edward Thornycroft followed his father as the governing director and chairman of John I. Thornycroft and Co., Ltd. Another brother, Isaac Thomas (Tom) Thornycroft also worked in the firm until 1934.[4] Family activities intertwined with the family business – Tom Thornycroft won two gold medals in the 1908 summer Olympics driving Gyrinus II, which had been designed by his father. As far as it has been possible to discover, of the women in the Thornycroft family only Blanche seems to have been involved in the family firm, although there is no record of her being salaried nor of any other form of payment to her. Moreover, it is not clear where she picked up her knowledge of mathematics and engineering as there is no record of any formal education at university level. Learning by doing within the family and the works would have been a well-established method as it was the foundation of both the premium (by payment) and normal apprentice system. Toward the end of the twentieth century the all-graduate engineering profession has rather eclipsed the complex system of trade and technical education that existed from the nineteenth century to around the 1970s. Learning on the job was sometimes referred to as ‘sitting with Nellie’, a term implying that this was inferior and needed to be replaced with more formal, often university, education. The professional engineering bodies contributed to technical education through exams and later accreditation, but also acted as a network and clearing house of engineering knowledge through regular meetings and publications (Buchanan, 1989). It is a little curious that Blanche, having attained the position of an Associate within the Institution, did not appear to avail herself more of the meetings and events organised by the INA. However, it is important to note that the information in the archives does not contain a full set of company records, any personal diary or, aside from the one handwritten letter discussed below, any correspondence material from Blanche. Examination of the digitised journal of the Women’s Engineering Society suggests that Blanche was not active there. She appears to have shunned publication and wider involvement even though she was at the heart of cutting-edge developments in naval architecture.

After the movement of the manufacturing base to Woolston, Sir John I Thornycroft moved the family home to Bembridge on the Isle of Wight, and it was here that he developed facilities to explore the design of ships. The garden had a feature known as ‘The Lily Pond’, built to look like a garden pond. This was rebuilt to include sophisticated measuring equipment hidden behind a pump driven waterfall. Once the waterfall was turned off and the waves died down it became a testing tank (see Figure 2). This enabled the construction of scale models which were then tested by being towed in the water. The model boats were pulled at an even velocity across the pond via the ‘constant force’ towing arrangement, operated by a descending weight (Jeffries, 2011, 2.4).

Figure 2

Black and white photograph of a woman working alongside a boat testing tank

Blanche working at the Lily Pond Test Tank. She is standing in front of the building, which contained the measuring instruments. The model boat being tested and the wire which pulled it can be clearly seen

In Figure 3, Blanche is pictured holding one of the discs from the recording device, made by the Cambridge Scientific Instrument Company, which recorded the performance of the model boat in the ‘Lily Pond’ tank. As John Jeffries comments, the lily pond still exists (as of 2018) and ‘…astonishingly perhaps, models in reasonable condition have been recovered from the bottom in recent years’ (Jeffries, 2016, 2.4).

Figure 3

Black and white photograph of Blanche Thornycroft holding a disc used for recording test data

Blanche holding one of the discs from the recording device, made by the Cambridge Scientific Instrument Company, which recorded the performance of the model boat in the ‘Lily Pond’ tank

Two of the most notable pre-First World War boats, Mimi and Toutou, that appear in Blanche’s notebooks were built at Chiswick and supplied by Thornycroft to the Royal Navy for what the London Gazette called ‘The Tanganyika Naval Expedition’. The expedition was covered in 1922 within the pages of the National Geographic by one of the participants (Magee, 1922). Blanche worked on the testing of these boats with her father and may have attended the testing on the Thames. It is thought that the picture below (Figure 4) may show Blanche standing in the stern of Mimi. Toutou is tied up in the foreground and the picture was taken at Chiswick, during trials on the Thames. A further, if more indistinct image (see Figure 5) appears to show the same person aboard the boat at speed.

Figure 4

Black and white photograph of Blanche Thornycroft standing in the prow of a pre first world war boat

It is thought that Blanche attended tests; this may be her waiting to disembark from Mimi, one of the boats built for the Tanganyika Naval Expedition.

Figure 5

This may be Blanche in the stern of Mimi one of the boats built for the Tanganyika Naval Expedition and tested on the Thames.

These boats were forty-foot Thorneycroft twin engine motor boats, originally ordered as seaplane tenders for the Greek Air Force. However, the needs of the Admiralty came first as the London Gazette reported:

In April 1915, a scheme was approved by the Admiralty for depriving the Germans of the command which they had hitherto held, by means of three small armed vessels, on Lake Tanganyika. The plan was to send out from England to Cape Town, and thence by rail, road and river to the Lake, two motor-boats of a speed and armament which would outclass those of the German vessels. The two boats, with a small Expeditionary Force under the command of Commander G. Spicer Simson, R.N., arrived at Cape Town towards the end of June. By December 23rd the ‘Mimi’ and the ‘Toutou,’ as the boats were named, had been successfully launched on the Lake, and three days later the first action was fought (London Gazette Supplement, 1917, p 7070).

Although the use of the lily pond was successful as a way of collecting data for design, it was dependent on the vicissitudes of the weather which could mar the results. The need for more accurate data led the firm to investigate building a new test tank. The tank was constructed in another part of the family garden at The Old Battery in Bembridge to a design by the engineering company I.G. Mouchel[5] (see Figure 6). The first test was recorded by Blanche as taking place on 3-4 November 1911 (see Figure 7).

Figure 6

Black and white photograph of a test tank facility at Bembridge

The Test Tank built by Sir John I Thornycroft at the family home in Bembridge, Isle of Wight, seen here circa 1911

Figure 7

Colour photograph of the interior of a model boat testing water tank facility

The interior of the Bembridge Test Tank photographed in February 2017. The dimensions were carefully calculated, especially the depth of 13 feet 9 inches, so that any motion caused by the passage of the model in the water would not affect the test results

Beneath the working areas at each end of the tank and contained within the lower floor of the building were two workshops; one was for the carpenter who made and adapted the models whilst the other was used by a metal worker.

Kenneth Barnaby describes the operation of the tank in some detail (Barnaby, 1964). Historic England give the dimensions as 67 feet 6 inches long, 30 feet wide and 13 feet 9 inches deep. The tank operated using the ‘falling-weight principle’, with deep wells at each end, with a towing mechanism comprising a winding drum attached by a line to the model under test. The speed of the model was then measured by using a tuning fork to inscribe a sine wave trace on a carbon (smoke)-blackened disc attached to the winding drum. Barnaby noted that:

‘This simple equipment may sound a little out of date, but a tuning fork maintains its frequency, whereas more complicated electronic devices do, at times, give trouble. The strong acceleration also has an advantage, as it seems to break down laminar flow without the need for special turbulence stimulators’ (Barnaby, 1964, p 92).

The line ran from each weight to a pulley at the top of two towers at either end of the tank. Addition of mass to either of the weights controlled the speed of the pull. The towers, pulleys and pits are still extant, but the line is not. It seems that the model may have been attached to a bar slung on the line.

This method and the possibility that there were different bars for higher and lower speeds is alluded to in a letter from Blanche to John E Thornycroft written on 16 January 1931. With some models the centre of gravity, the height of the towing beam and the heavy pull required corrections to be made to achieve to the necessary settings.[6]

One of Blanche’s tasks was to try and improve the speed of the pull. Thornycroft were using the Cambridge Scientific Instrument Company to develop additional bars for the measurement process.[7] An undated photograph (see Figure 8) shows a model under test and is annotated in what appears to be Blanche’s handwriting – ‘90 mph EI 3 lbs measured 9 inches from the transom’. The speed referred to would have been arrived at by calculation from the scale speed and it is this type of work that was carried out by Blanche.

Figure 8

Black and white photograph of a model boat travelling at speed in a water tank testing facility

A model on test in the tank. According to the inscription it is moving at a scale 90 miles per hour

During the First World War (note Historic England) ‘...Sir John, assisted by his daughter Blanche, an Associate of the Institution of Naval Architects, did a considerable amount of work with his experimental tank and, among other things, established the resistance of the mooring-ropes of mines when inclined at different angles to the current.’[8] This work would also turn out to have a peacetime application.

A request in 1935 from The Western Union Telegraph Company to Sir John E Thornycroft illuminates further Blanche’s work during the First World War. They enquired whether he could furnish them with the results of the tests on the resistance of wire hawsers at different angles to the current. Apparently, though copies had been sent to both the Admiralty and the National Physical Laboratory, these had been lost. Sir John wrote to Blanche on 9 May 1935 asking if she could find her original notes. Blanche had replied supplying the data by the 21st of the same month enabling Sir John to write to Western Union enclosing it, stating:

‘I now send you two curves which have been plotted from the results of experiments carried out by my father, the late Sir John I. Thornycroft, in 1917. Miss Thornycroft, who acted as his assistant during the war period, has turned up the original notes of the experiments corresponding with the curves which were produced from them. The results were used by the Admiralty Department concerned at the time for mooring wires for mines etc. and were accepted as accurate.

‘The method of carrying out the trial was to suspend the wire below a ship model of known resistance at the different speeds, which was towed in the ordinary way. […] I trust that the information I am sending will be useful to you and am very glad to think that the time which was taken, (actually several months [sic] hard work during the war period) may prove useful in connection with peaceful operations.’[9]

Blanche’s note book containing the tests results on wire hawsers shows that the experiments actually took place from May 1916 until January 1917, hence Sir John somewhat understates the amount of time and effort involved.[10] This reveals that Blanche was closely involved in the work of the tank at Bembridge.

Perhaps the most important work by Thornycroft’s during the war was in developing a peacetime design into a vessel that could be used for war. From the early forays into Olympic speed boats, John I. Thornycroft and Company were ideally placed to supply lightweight fast 40- and 55-foot torpedo boats, thus giving the Navy of the time the advantage of lightning raids that in the twenty-first century would be carried out by aircraft or missiles. A history of their development published by the company in 1918 states:

‘The very extensive use of mines made it extremely difficult for submarines and boats of considerable draught to approach the enemy bases, with the result that the smallest possible vessel with a great speed was again the obvious means of carrying the Whitehead torpedo to attack the enemy’ (Thornycroft, 1918, p 1).

In order to keep the boats light and of minimum draft, they were built of wood, the earliest of them having only one torpedo as their armament, launched backwards from the stern of the boat. The method of attack was that the Coastal Motor Boats or CMBs would be carried to a point out of sight of, but close to, their target by a larger warship. The first 40-footers were capable of being slung in lifeboat davits on the mother ship. Having been launched by the larger warship, the CMBs raced into harbours and headed straight for their target ship, only firing their torpedo at what might be described as point-blank range. The CMB needed to get out of the way of the torpedo, hence a 180-degree turn was executed at high speed and a hasty return to the mother ship effected. The boats, whilst extremely fast, with speeds in excess of thirty knots, needed to be highly manoeuvrable and it was here that the careful testing, recording and calculation by Blanche Thornycroft prior to the first build in 1915 was vital. Their speed depended on the hull shape causing the boat to ‘plane’ meaning that the stern, being pushed deeper in the water as the speed increased, so that the bow rose, and over half the total length of the CMB lifted out of the water. This reduced the friction on the hull and made these boats extremely fast. However, the boat also had to be stable, a factor which could be compromised as the bow rose and it was here that the testing of the hull shape in model form was so important.

Figure 9

Black and white photograph of a coastal motor boat travelling at speed

A Coastal Motor Boat being tested on the Thames at Chiswick. The crew, apart from the helmsman, are sitting in the torpedo space, presumably to simulate the weight of the weapon and thus allow the boat to plane correctly. See also Figure 10

Figure 10

Black and white photograph of a coastal motor boat with a loaded torpedo

A Coastal Motor Boat with its torpedo loaded. The torpedo was fired backwards and as soon as it hit the water the boat had to execute a high speed turn to avoid it

The CMBs were developed throughout the war. Blanche was recording tests on the later 55-foot boats in September 1917. These boats were used in raids on Zeebrugge and Ostend in 1918, and perhaps most famously in the attack on Kronstadt harbour against Bolshevik ships in 1919. Lt Cdr Agar commanding CMB4 was awarded the Victoria Cross for his role in the attack.[11]

Figure 11

Colour photograph of an original wooden scale model of a coastal motor boat

This is the original model CMB that Blanche tested which is now in the care of the Classic Boat Museum, East Cowes, Isle of Wight

The original model CMB that Blanche tested is now in the care of the Classic Boat Museum, East Cowes. It measures nearly six feet long and it has been three-dimensionally scanned to enable a reconstruction of CMB4 to be undertaken at the National Shipbuilding College at Portsmouth. In this regard alone, the work Blanche did in the original testing of these craft is worthy of note. 

Component DOI: http://dx.doi.org/10.15180/1851009/004