Sunday, 17 February 2013

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

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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.
Author’s painting of Sea Lion II (see Blog 17.3.12 re colour)
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)


The 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 (details below) 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:

Advance Notice:    R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire.
This is a much expanded, completely up-to-date, second edition of my earlier work with 50% more photos, and 25% more text – 380 pp. instead of 250. There are general arrangement drawings of Mitchell’s 21 main aircraft types which flew, as well as 40 other drawings. There are 24 photographs, featuring or including Mitchell, as befits the first fully detailed and, I hope,  definitive account of the man and his work at Supermarine.
To obtain a copy at pre-publication prices, please enquire via the contact form in the sidebar. 

Friday, 8 February 2013

R .J. Mitchell’s Early Modifications (1919 to 1921).

 


Whilst Mitchell was busy with his first medium-sized, slow-flying designs (the Commercial Amphibian and, later, the Seal/Seagull II development), his firm was still interested in the possibility of selling the concept of a small naval “scout” to the Navy and Mitchell was involved with the various modifications to this fast seaplane type.

    The company’s interest in the fast interceptor had begun with an Air Ministry requirement, N.1B, for a fast manœuvrable single-seat seaplane or flying-boat fighter with a speed of 95 kt at 10,000 ft and a ceiling of at least 20,000 feet. The resultant Baby had been designed by F. J. Hargreaves, who was in charge of the drawing and technical offices at Pemberton Billing and who continued for a little while after the company became “Supermarine”. Hargreaves’ close liaison with the Admiralty Air Department produced an aircraft with what appeared to be a dangerously small fin and rudder, typical of aircraft drawn up by this design team but the Baby was, in other respects, a more ‘in house’ response to the ambitious N.1B specification.
N.1B

However, this machine did not go into production because of the ending of World War I but, as Mitchell had joined the firm in 1916 and had then been involved at least with the Nighthawk (see my Blogpost: 'What was R.J. Mitchell's First Design?'), it is entirely likely that he had had some design input in the three N.IB airframes that were built: by the time of the Armistice, N59 (see photo above) had been completed and was being evaluated by the Navy and N60 was largely complete. The third, N61, was under construction and was most probably (in view of its extensive departures from the N59 design) the one bought back from the Air Ministry for entry in the 1919 Schneider Trophy competition, in the hope thereby to gain some very useful publicity.  The modifications were such that it was re-named the Sea Lion I.


Sea Lion I.

Sea Lion I

The particular configuration of this aircraft suggests that the modifications to the Baby design were largely Hargreaves’. The fin and rudder were enlarged in a shaping not followed later by Mitchell (see fin sketches below); likewise, the base of the latter was used as a water rudder, the interplane struts were splayed outwards, and the wings had balanced ailerons on the top wing only and had an inverse taper. Also, the hull was decked to keep down spray and so the front of the fuselage was far less sleek than Mitchell’s later Sea Lion II and Sea King II:
Sea King I (see later)                   Sea Lion I                                   Sea Lion II
                   

In appearance, the aircraft suggested that the man with overall responsibility for this aircraft seemed to have favoured rugged seaworthiness rather than speed through the air; as such, it was the Royal Aero Club’s choice over the slightly faster Avro 539A, for the third entry to the 1919 Schneider Cup competition – possibly hedging their bets because of the already proven sea-going qualities of Supermarine machines. But, by the time of the Schneider contest, Hargreaves had left the company and it was Mitchell who would have assumed last-minute responsibility for this aircraft.

However, the “non-event” of the 1919 Schneider Trophy contest was of no help to Supermarine’s hopes for this type but the company persisted with their fighter flying-boat concept with their next two fast flying-boats, the Sea Kings.


Sea King I.
As Mitchell’s design inputs began in 1916, it is more than likely that he had also been involved with the Sea King modifications to the original N.1B Baby design; however, little is known about his involvement in the N60 version, also bought back from the Air Ministry, and which, it seems likely, became the Sea King I.
This aircraft appeared, largely unmodified, at the 1920 Olympia Aero Show, after Mitchell’s  appointment as Chief Designer, but how long it had been in existence in this guise before this date is unknown; certainly the direct repetition of the earlier, apparently inadequate tail configuration looks backwards rather than to the future:
 N.1B Baby and Sea King I          Sea Lion I            Sea King II  (see below)
      

One speculates that, at this time, the profitable modifications to the A. D. Boats had so pre-occupied Supermarine that a relatively unmodified N60 Baby was sent to the Olympia Aero Show essentially as a marker for the company’s continuing interest in the naval fighter scout concept. There is no record of the aircraft having flown, thus adding to the speculation surrounding the Sea King I. The following publicity for this aircraft, apparently re-engined, would seem to imply that control might not be quite adequate; it also reveals that the company was hoping to sell to the many private flyers that World War I had produced, if military orders could not be achieved:
The ‘Sea King’ is a small fast single-seater which for general purposes follows the structural methods of the ‘Channel Type’ boat. With its 160 h.p. Beardmore engine it puts up a speed of 96 knots, so that it is either a thoroughly sporting little vehicle for the single or unhappily married man, or is a useful small fast patrol machine for Naval work along troublesome coasts. Its chief difference in design from the ‘Channel Type’ lies in the fact that it only has a monoplane tail of the depressing kind and so takes rather more flying on the part of the pilot than does the bigger machine.
Had there been any sales, perhaps Mitchell might have wished to modify the tail surfaces but, unfortunately, neither the military nor the ‘single or unhappily married man’ came along to buy one and it had to await the Mark II development by Mitchell two years later. 

The Sea King II.
In response to the continued Air Ministry interest in a fighter design for shipboard use, Mitchell now produced an amphibian modification of the Baby/Sea King I machine: ‘designed as a high performance fighting scout, specially adapted for getting off gun-turret platforms of capital ships, or getting off and landing on the decks of aircraft carriers. The strength and design of the hull are such that it can operate on and from the water under any weather conditions in which it would be possible to operate any other sea craft [boat] of equal size’ (Supermarine publicity). It was produced in 1921 and so its modifications can be attributed entirely to Mitchell and, indeed, it bore distinct evidence of his taking over the design department at Supermarine.
The most obvious revision of the earlier design was the more generous fin and rudder area (see sketches above) – and it would appear from the Supermarine publicity quoted below that this had a noticeably beneficial effect). As with his Seal (see my Blogpost: 'Precursors of R.J. Mitchell’s Walrus'), the tailplane was now placed almost midway on the fin and the retracting gear of the Seal was again utilized. At the same time, Mitchell also devised a very simple method for the removal of the undercarriage system and a Seal type combined tailskid and sea rudder was also employed.
   The wing-tip floats were the same full depth type as employed on the Baby, Sea Lion I and Sea King I and the tailplane outline was similar to that of the Sea Lion I or the Seal II but with the lower position of the latter – whose reversed camber (“of the depressing kind” continued the Baby tradition.  The aerodynamically balanced ailerons and rudder of the Sea King I were again abandoned in favour of the Baby configuration; the more streamlined Baby/Sea King I hull was retained.

The Supermarine description of this version of the single-seat flying boat fighter type also draws attention to its flying qualities as well as to the many practical features now incorporated by the designer (a theme that would become familiar in the Mitchell story):
The manœuvrability of the ‘Sea King’ Mark II is one of its most important features. It can be looped, rolled, spun, and stunted in every possible way. Longitudinally, the machine is neutral, and flying at any speed throughout its entire range either with engine on, gliding, or climbing, no load is felt on the control stick. This balance has been obtained entirely on the stabilising surfaces, and no mechanical adjustment by the pilot is required. . .The engine, a 300 h.p. Hispano Suiza, is mounted in a streamlined nacelle, which contains oil tank, radiator and shutters, piping, controls, etc. The whole unit is very accessible and the engine can be replaced very easily.Interchangeability and ease of upkeep and repair have been carefully studied. The complete wing structure, including power unit, can be removed from the hull by withdrawing eight bolts. The wing structure consists of top and bottom centre sections, and top and bottom planes of equal span. One set of struts are [is] carried on either side of the centre section. The top planes have a dihedral angle of 1° and the bottom planes one of 3°. The engine unit is carried on two sets of inwardly inclined N struts, and can be removed and replaced without interfering with any wing structure member . . .The amphibian undercarriage, which can be removed by the undoing of ten bolts in all, folds up under the wings, and when folded is well clear of the water. It is raised and lowered by a worm and bevel gear.

The Sea King II was designed and built in six months and made its first flight at the end of 1921 but, once more, no orders were received; however, there was some further development in 1922 and 1923 – see my Blogpost concerning Sea Lions II and III.


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

More information, photographs, and a three-view drawing of the Sea King II 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:
Advance Notice – 
R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire.
This is a much expanded, completely up-to-date, second edition of my earlier work with 50% more photos, and 25% more text – 380 pp. instead of 250. There are general arrangement drawings of Mitchell’s 21 main aircraft types which flew, as well as 40 other drawings. There are 24 photographs, featuring or including Mitchell, as befits the first fully detailed and, I hope,  definitive account of the man and his work at Supermarine.
To obtain a copy at pre-publication prices, please enquire via the contact form in the sidebar.