Friday, 24 March 2017

Mitchell's First Schneider Racers – the Sea Lions II and III.

Mitchell's Sea Lions had a common ‘ancestry’ in the N.1B Baby design and the Sea Lion I had a limited input by Mitchell (see my Blog:"R. J. Mitchell's Early Modifications"), whereas the quiote different Sea Lion II was entirely his responsibility – as, of course, was the Sea Lion III which followed.

Sea Lion II
In 1922, the Air Ministry issued Specification N6/22 for a single-seat fighter capable of operations from aircraft carriers or as a floatplane. The winner of the contract was the Fairey Flycatcher – it had a slightly higher top speed than Mitchell's Sea King (133 compared with 125 mph), it was just as aerobatic, its short span allowed it to be struck down to the hangers without folding wing arrangements, and its extensive aileron-cum-flap arrangements produced very low minimum take-off and landing speeds.
     With hindsight, it might thus be seen that the days of a fighter flying-boat were numbered but Scott-Paine, the managing director of Supermarine, was still determined to continue with the type and decided to seek publicity for it by entering a version of the aircraft in the 1922 Schneider Trophy contest. Another, more patriotic, reason might have been to prevent the Italians from winning the Trophy outright with a third win in the forthcoming competition (after the inconclusive Bournemouth event of 1919, the Italians had had fly-overs in the following two years).
     Also, the rules had been changed in 1920 to encourage a more practical type of aircraft rather than an out-and-out racer: 300 kg. of ballast had had to be carried and, although this requirement was dropped the next year, it was replaced by a watertightness test in which the aircraft had to remain afloat fully loaded for six hours. These rules tended to suggest the flying-boat’s suitability for the Trophy contest and it must have been noted that the recent Italian designs to meet these requirements had, indeed, been flying-boats.
Despite the omens favouring flying-boats, the uncertain financial outlook of the Supermarine company at this time was such that its Managing Director did not feel able to incur the cost of designing and building an entirely new machine and so the fuselage of the previous Sea King II was utilized. He also obtained the loan of a Lion engine from the manufacturers, a high speed propeller, petrol and oil from other manufacturers, and a fifty percent reduction in insurance rates.
     Mitchell, no doubt remembering the sleek Savoia at Bournemouth, aimed for increased speed by making the entry of the fuselage, originally shaped to house a gun, somewhat smoother (see also "R.J. Mitchell's Early Modifications"). And as the Lion engine to be fitted developed 150 hp more than the original Hispano-Suiza engine, he was able to decrease the area of the wings by reducing their width. Another modification was necessitated by the test pilot's refusing to test fly it until the rear fuselage had been stiffened up. Again, in response to the extra power of the engine, an additional increase in fin area was called for. Mitchell achieved this with least expenditure of time and money by merely modifying the vertical surfaces above the tailplane; the leading edge of the fin was given a pronounced forward curvature which proved to be effective but certainly won no prizes for elegance.
     The finished machine was named "Sea Lion", thus drawing attention to the name of the loaned engine. It was also designated a Mark II, to distinguish it from Hargreaves’ earlier design but, as a result, misleadingly suggested that it was a direct development of it, contrary to the pedigree described above.
Supermarine Sea Lion II  (from a painting by the author)
As there have been many accounts of the Supermarine 1922 win, I will confine myself to the following relatively unknown contemporary Cozens extract:
. . . bad weather cut down Captain Biard’s chances of getting used to the Sea Lion, and this was further jeopardised by a forced landing which began with the engine cutting out over the Dock. However, when he had had a few more flights he was satisfied and the speed and handling proved very good, indeed it was faster than any flying boat or seaplane of that time. Then, with the limited time available, it was doubtful if they could get the Sea Lion to Naples in time but the General Steam Navigation Co. agreed to take it and it was hurriedly dismantled, put into a crate and on to a lighter, and one of Ray's tugs took it down to the Solent and the freighter Philomel lifted it on board and took it to Naples.
Pre-race spying and counter-spying on both sides was all part of the event. This atmosphere continued throughout the whole series and it was the policy of each competitor to arrive at the start of a competition with a machine that was ahead of its rivals by virtue of some secret and outstanding advantage which was not revealed until it was too late for anyone to copy. In the case of the Sea Lion this meant that the wing-span was cut down to an absolute minimum and as the trials at Woolston had been curtailed even Captain Biard was not too well practised as to the machine’s behaviour.
He kept is speed down in the practice flights but was quietly getting used to the course and conditions, and his engine fitter, Mr. Pickett tuned up the engine to the higher temperature of the Bay of Naples, so that when the race started Biard was reasonably prepared …
When Captain Biard and his victorious team came to the Floating Bridge with the great prize held above their heads no-one bothered whether it was a Cup or a Trophy – everyone called it a cup, certainly Scott-Paine. I had parked my bicycle outside the Woolston Picture House and I saw the Supermarine workers run down to meet them. They had taken the two swivel chairs from the office and fixed them to poles and they lifted Captain Biard and Scott-Paine in the chairs shoulder high and carried them round the works … Fireworks were let off and there was some horn blowing … [One suspects that Mitchell’s relatively recent arrival in the firm at the time as well as his temperamental self-effacingness account for there being no mention of him in the celebrations.]
Mitchell’s machine not only won the Schneider Trophy race for Britain at an average speed of 145.7 mph but also gaining the first F.A.I. World Records for seaplanes:
(i)        Duration – 1 hr 34 min 51.6 sec
(ii)       Distance flown – 230 miles
(iii)      Fastest time for 100 km closed circuit – 28 min 41.4 sec (130 mph)
(iv)      Fastest time for 200 km closed circuit – 57 min 37.4 sec (129.4 mph)


 Sea Lion III
As the next Schneider Trophy contest was to be held in England, it was to be expected that Supermarine would be only too happy to capitalise on their 1922 publicity by competing, successfully it was hoped, without the cost of overseas travel and accommodation. Indeed, the new venue decided on was to be Cowes, less than 20 miles from the Supermarine works at Woolston. But only with the large-scale production of the Southampton, which began in 1925, might Supermarine have felt justified in the cost of designing and building a one-off specialist racer and, as the top speed of the Sea Lion II was significantly less than that of the record breaking Savoia S.51, he did not immediately respond to the challenge.
    When Scott-Paine was persuaded to submit an entry, he confined himself to asking his Chief Designer to do his best with the 1922 airframe, to which Mitchell fitted an uprated Napier Lion III engine and radiator into a more streamlined nacelle. The more powerful engine also allowed for a reduction in the wing span by four feet and he also had fairings made behind the two hull steps:

Sea Lion III

In addition, he designed new wing-tip floats offering less frontal area, mounted them on streamlined struts, and added fairings around the main strut attachment points. Because an extra 75 hp was available from the new Lion engine, the rudder and fin were increased in area, the resultant combination looking less improvised than that of the Sea Lion II.
Mitchell’s changes could hardly prevent the Supermarine entry from showing its, by now, venerable pedigree and one feels that the rather whimsical sea lion head depicted on the nose and floats of the Supermarine entry was almost a self-deprecating gesture in face of the expected serious opposition from America: their Curtiss racers were fitted with of one of the great aero engines in aviation history, the Curtiss D-12, whose frontal area was about 50% less than the rival Napier Lion and their winning of the 1922 Pulitzer race was also due to the incorporation of radiators flush-mounted on the wings and to the use of metal propellers (as tip speeds were now approaching the speed of sound.) 
Sea Lion III at the competition base.

Of the three machines which finished the competition, these Curtiss CR-3 floatplanes came first, with an average speed of 177.3 mph, and second, with an average of 173.46 mph. Despite 75 more horsepower, Biard could only manage an average of 157.17, a poor third.
     Clearly, the usual European flying-boat formula with an engine mounted above the hull was no longer likely to be the best approach – apart from the formidable in-line engine and the flush fitted radiators, the Curtiss CR-3 configuration also limited the number of other drag inducing items to 16 struts, with 20 wires, despite the extra penalty of floats, whereas the Sea King/Sea Lion I tradition Mitchell had inherited had required 33 struts and 42 wires as well as a boat-like hull. Afterwards, Scott-Paine praised the Napier engine ‘that would have gone on for ever’ but said that he needed ‘to apologise to Capt. Biard because we did not give him a good enough machine’.

The Sea Lion, which had retained its Mark II registration G-EBAH, was returned as N170 to the Marine Aircraft Experimental Establishment at Felixstowe with its undercarriage and sea rudder/skid now restored but its career was short lived, owing to its extremely lively take-off performance. As Biard had said, ‘It was an interesting sensation; you switched on the engine, and before you could count 1, 2, 3, 4 fast – she was flying.’ Unfortunately, when Flg Off. E. E. Paull-Smith, took over the Sea Lion, he apparently did not take sufficient notice of the warning that the machine tended to lift off before flying speed had been reached. As a result, he took off, dropped back onto the water, rose to about forty feet, stalled again, and dived in. Paul-Smith was killed and the machine was too extensively damaged to be considered worth repairing.
     This incident, on 25 June, 1924, marked the end of Supermarine’s attempts to interest the Air Ministry in the seaplane scout concept and also the beginning of Mitchell’s search for a worthy and dedicated Schneider Trophy competitor (see my Blog: R.J. Mitchell's Annus Mirabilis, 1925: Part II).


* * * * *



For reference sources, see my Blog: “Source Material and References. " An extended bibliography is included in my R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire (see sidebar) which also provides material for wider reading, grouped according to specific areas of interest. 

More information, photographs and three-view drawings of the Sea Lions, details of the 1922 and 1923 Schneider Trophy contests, as well as a full account of all Mitchell's completed designs and of the man behind them, will be available in a few weeks' time:

1 comment:

  1. This comment has been removed by a blog administrator.

    ReplyDelete