His Majesty's Airship No. 1 was designed and built by Vickers, Sons and Maxim at their works in Barrow-in-Furness, Lancashire, England, as an aerial scout airship for the Royal Navy. It was the first British rigid airship to be built, and was constructed in a direct attempt to compete with the German airship programme. Often referred to as "Mayfly", a nickname given to it by the lower deck (i.e. the non-commissioned component of a naval ship's crew), in public records it is designated 'HMA Hermione because the naval contingent at Barrow were attached to HMS Hermione, a cruiser moored locally preparing to act as its tender.
When it was moved from its shed in Cavendish Dock to conduct full trials on 24 September 1911 it broke in two before it could attempt its first flight as a result of being subject to strong winds . Although Mayfly never flew, its brief career provided valuable training and experimental data for British airship crews and designers.
Background
In July 1908 Captain Reginald Bacon, the Royal Navy's Director of Naval Ordnance, recommended that the Navy should acquire an airship that would compete with the success of the early German rigid airships built by Count Ferdinand von Zeppelin. The British Government agreed that a sum of £35,000 (£ million today) "should be allocated to the Admiralty for the building of a dirigible balloon", and in March 1909 the armament firm of Vickers, Sons and Maxim advised that they could construct the ship for £28,000 (£ million today), not including the goldbeater's skin gas bags and outer cover, for which the Admiralty was required to provide contractors, and that they would erect a constructional shed at their own expense in return for a 10-year monopoly on airship construction, similar to the submarine agreement they already had with the Crown. The contract was awarded to Vickers on 7 May 1909, with design responsibility divided between Lieutenant N. F. Usborne at the Admiralty and C. G. Robertson of Vickers; however, the 10-year monopoly clause was refused.
Design
Mayfly was intended to be an aerial scout, and was similar in design to contemporary Zeppelins, but with some major differences. At length and in diameter, it was longer than the contemporary LZ 6 and had a 50% larger volume, giving a correspondingly greater lift. His Majesty's Airship No. 1 was more commonly known as the "Mayfly", or simply referred to as "No. 1." In official records HMA No. 1 is often referred to by the name of the tender in which the crew was quartered, HMS Hermione, or the "Hermione Airship". The name Mayfly originated as a nickname originated by the sailors assigned to it. HMA No. 1 was essentially an experimental design and was therefore to be built as cheaply as possible.
Zeppelins of the time had a useful load of around 10,000 lb (4,500 kg) and were capable of flying at . The Vickers design was intended to be moorable on water, carry wireless equipment, be capable of for 24 hours, have a ceiling of , and carry a crew of 20 in comfort. The mooring was to be to a mooring mast, a practice that the British were the first to adopt as standard, and Mayfly was the first rigid airship to be fitted with the mooring equipment in the nose of the ship.
Before construction began an experimental section was constructed. This used a variety of construction techniques: one end used hollow timber spars, the centre frame used a combination of timber and aluminium, while the other end used aluminium only. Although wood proved the most satisfactory, the Admiralty preferred metal. In late 1909 duralumin became available, and it was decided to use this new alloy, which would allow a considerable weight saving while also forming a stronger structure. The use of Duralumin preceded its use by Zeppelin by four years. Development of HMA No. 1 involved essentially inventing the technology necessary and considerable experimentation in materials and manufacturing techniques was required before the final manufacturing processes were decided upon. The hull was made up of 40 twelve-sided transverse frames spaced apart: some of which were cross-braced by wires, dividing the structure into 17 bays of irregular length, varying from 12.5 ft to 37.5 ft (3.8 m to 11.4 m). The frames were connected by 12 longitudinal girders and a triangular section keel below the main structure. The hull shape was based on work by the American aerodynamicist Albert Zahm, and its head resistance was claimed to be 40% of that of contemporary Zeppelins. A fully streamlined shape had been proposed, but was rejected by the Admiralty as being too difficult to construct. It was not until 1918 that a truly streamlined airship, the R80, was designed.