M.Goodall, A.Tagg British Aircraft before the Great War (Schiffer)
Deleted by request of (c)Schiffer Publishing
H.King Sopwith Aircraft 1912-1920 (Putnam)
Anzani Tractor Seaplane
This otherwise undistinguished aircraft is given one distinction, in nomenclature at least, by prefacing its name by the marque of engine installed - thus conforming strictly with historical accuracy, except that it must be admitted that the term 'seaplane' had not, at the time of its emergence (summer 1913) superseded 'hydro' or 'hydro-aeroplane', or even the grossly confusing 'hydroplane'. (This last expression was, in truth, applicable only to high-speed skimming craft, or very fast motor-boats, with which Tom Sopwith was familiar). More than this: by correctly introducing the type of Sopwith aeroplane now under scrutiny by the distinctive name of its engine one feels wholly vindicated in one's continuing emphasis on the significance of powerplants in its maker's history; for here we meet the first of the fixed, star-shaped air-cooled radials to come into general use - remembering, of course, that, using a three-cylinder fan-form 25 hp Anzani, Louis Bleriot had long since flown the English Channel (25 July, 1909). The particular type of engine in the seaplane now studied had ten cylinders, arranged in two rows; and it weighed 363 lb (165 kg).
But first to describe the brand-new Sopwith aeroplane itself for such it was considered, notwithstanding a resemblance to the 'Three-seater' landplane; and, indeed, as we shall see, there once existed a landplane version (or conversion) of the basic type now considered. Thus we must proceed with special care, though emboldened by Mr R. J. Ashfield's own description of the particular waterbird now in our sights as the '100 Anzani Tractor Seaplane.'
This actual mention of the engine's nominal output - 100 hp - can be directly linked with the fact that the new Sopwith aeroplane was sustained on the water, and hampered in the air, by three weighty and clumsy floats (two main, one tail, as was then usual). Even so, the description 'clumsy' is here applied only in a general, and not in a particular, sense; for with his motor-boat, balloon (and now fast-growing aeroplane) experience Tom Sopwith had a special concern with weight and drag. Thus the float landing gear and associated considerations are rightly our own first concern also - with the ensuing contemporary account meeting the case perfectly:
'Two main floats with spring suspension are fitted, in addition to a single tail-float. The 100-h.p. Anzani drives a propeller of approximately 9 ft. diameter, covered with thin copper to prevent splintering on the waves. The span of the top plane being approximately 56 ft. the floats are widely spaced, 10 ft. 3 ins. apart. There is, in consequence, no necessity for wing-tip floats. The main ones are mounted on inverted V-struts. As in all the other models [sic: meaning 'current Sopwith models'] balanced ailerons are fitted...’
The account now under quotation went on to make a point which the present writer has already advanced, by noting that 'the subject of floats' was 'an interesting one' which had 'obviously been studied by Messrs Sopwith with the greatest of attention'. These remarks were amplified - or, as will be seen, in some degree skirted - as follows:
'The finished product is of pleasing appearance externally, and, of far greater importance, the work and constructional design leave little to be desired. Of the hydrodynamic and aerodynamic qualities in the design we are not prepared to speak, for, by doing so, we should set ourselves up as authorities on a subject which is as little understood as was aerodynamics generally at the period when the Wright brothers first commenced their experiments...’
'Each float is covered with thin Holland blind union [sic], which is glued on and varnished, and through which the wood can clearly be seen. Three inspection covers are fitted, the interior edges of the interstices for which are padded in order to render them watertight. The hull [sic: obviously meaning the float-structure proper] is built up in two 1/8-in. thicknesses of cedar, the first skin being diagonally built up with 4-in. strips, while the outer is composed of similar strips running longitudinally. In addition to the outer layer of fabric, another one is placed between the two layers of wood. The interior is coated with black varnish a suitable combination of gas-tar and naphtha.
'The floats are fitted with laminated steel springs. Four of these springs are attached to each float, the extremities of the front one being rigidly fastened to clips screwed onto a 1 in. by 1 1/2 in. vertical strut within the hull. The rear spring, on the other hand, is free to move, this arrangement being the result of a problem which offers some serious consideration. The solution has been effected in this manner: the apex of the front spring is connected to that of the rear by means of a radius rod. There are, of course, two of these - one on each side of the float. The only result of the flattening-out of the front spring is to slide the rear one backwards, the enormous compression stresses which would otherwise arise on that portion of the float between them being, in consequence, avoided.
The bottoms of the floats are convex, with a camber of 1 1/3 in. An inspection of the interior shows the interesting manner in which the step is rendered sufficiently strong to withstand the by no means inconsiderable strains to which it is subjected. The bottom consists, in part, of a number of 'ribbons', or minor longitudinals. Those running along the bottom of the rear half of the float are continued past the step until they die off where they meet, and where they are attached to, the ribbons from the bow. These arc themselves continued to the upright portion of the step, on which they abut, the consequence being that a triangular girder is formed."
The foregoing account of the floats etc. is quoted at length in the knowledge that some readers will not only be instructed thereby, but amused into the bargain ("gas-tar", indeed...). Yet this same account gives eloquent support for the concern expressed in June 1912 by George Holt Thomas: it has always seemed to me that too little attention has been paid to the flying part of the hydro-aeroplane machine, i.e., to the planes of the waterplane. What I mean is this; no matter how good the floats may be, an efficient waterplane can only be evolved by using an efficient aeroplane. The floats should be regarded as a landing chassis and a landing chassis only...' Holt Thomas was speaking in the context of the 'lifting' floats developed by Henri Fabre; so let us now see what the gentleman of the gas-tar etc. had to say concerning 'the planes of the waterplane' as built by Sopwith in 1913. Thus:
'Balanced ailerons now take the place of the warping action on the wings. This is highly to be commended, for it is really strange that the warp on biplanes has been tolerated for as long as it has been. The twisting strain on the spars is by no means pleasing to the eye of the engineer, and it seems that the righting couple produced by the pilot is infinitely more nearly instantaneous with the use of ailerons than is the ease with warp. The reduction of speed, if any, is infinitesimal, so it is difficult to see where the point in the use of warping wings on biplanes comes in. Each wing-section [sic: presumably meaning wing-panel] can, in consequence of the use of ailerons, be built considerably stronger not only this, but another addition is employed to increase the strength of the wings. This is in the shape of a number of rectangular struts between the front and rear spars at each point where the interplane struts are attached. They might well be called distance-pieces, for their only use is to relieve of compression strains the various ribs, which, being of curved shape, have not the power of opposing these stresses to as great an extent as does a member subjected to direct compression. The four tips of the main planes, and the outer extremities of each member of the tail planes, consist of circular-section steel tubing. Attachment of the fabric is effected by sewing, the "bag" thus formed being slipped on afterwards.'
Following such an intimate insight into 1913-style aircraft construction and terminology (wherein - whatever the non-attributable authorship - the mind of Fred Sigrist in particular may be perceived) it remains to add the following points: that the attachment of the floats (each of which had five watertight compartments) to the bottom wings, and not to the fuselage, was a point that commended itself to adoption for the torpedo-dropping Type C; that the three-bay wings had a 'clear-view' centre section and extensions to the upper mainplanes (the term 'extensions' was applicable whether this feature was premeditated or an afterthought); that the ailerons - of which the quoted observer rightly made much were fitted on all four wings (hence his emphasis on "biplanes'); that the ten-cylinder two-row Anzani radial engine was installed very neatly indeed, complete with exhaust-collector ring in front; and that the petrol tanks were pressurised by an air-driven pump.
Having named Fred Sigrist in connection with the aircraft generally, if one person in particular can be associated with the design of the floats it was, apparently, Sidney Burgoine, an experienced boat-builder.
Three Sopwith Anzani Tractor seaplanes (numbers 58. 59 and 60) were delivered to the Admiralty, the first being formally accepted at Calshot in June 1913. No.59 went to Cromarty and No.60 to Great Yarmouth. At least one of these machines had a 'wireless' installation, the current for which was provided by a dynamo, chain-driven from the engine-starter shaft at 3,400 rpm. A cone-clutch was fitted to 'disengage the magneto when necessary".
That one of these Anzani-powered biplanes (apparently No.58) saw service in the early weeks of war. when the 'Eastchurch Squadron' went to France, seems fairly certain. Two, indeed, may well have survived. A photograph herewith shows just such an aeroplane (No.58 ?) in appropriate company, fitted with a wheel-cum-skid landing gear instead of floats, though without the little auxiliary wheels at the front of the skids as on the original 'Three-seater'. Side windows, such as were characteristic of the last-named type, were, however, a feature.
Anzani Tractor Seaplane (100 hp Anzani)
Span (approximately) 56 ft (17 m). Other data lacking.
P.Lewis British Aircraft 1809-1914 (Putnam)
Sopwith Tractor Seaplane
During July, 1913, three two-seat tractor seaplanes, Nos. 58, 59 and 60, powered by 100 h.p. Anzani engines, were supplied to the Naval Wing of the R.F.C., and one was flown at the Naval Manoeuvres of the same year.
O.Thetford British Naval Aircraft since 1912 (Putnam)
SOPWITH H.T. SEAPLANE
Three seaplanes of this type were delivered to the Naval Wing of the RFC, beginning with No.58 in July 1913. The others were numbered 59 and 60. They were used at Cromarty and Great Yarmouth seaplane stations and one participated in the Naval Manoeuvres of 1913. The engine was a 100 hp Anzani radial.