Sopwith D1 Three-seater 80-hp Tractor Biplane

[Leif Ohlsson]

[2012 comment:] I came across the following notes going through unfinished projects on my harddrive. There are a lot of them. It is in fact quite vain - literally, in both senses of the word - to keep stuff there, just in order to be able to show off some completed project at a much later date. That date may well turn into never. Like with this material, which I actually had forgotten about. So here qoes. Old stuff (from 2010 or earlier), but good. Or so I found it to be when rediscovering it. I hope you enjoy it.

This post is here as a threadstarter and placeholder/bookmark. The plan is to develop five distinct but related topics over an indeterminate period of time, while I may do other paper modeling activities on the side:

1) A history of the Sopwith 80-hp SLTB D1 – Sopwith terminology for "Sopwith Landplane Tractor Biplane type D1". It is a less-known design which nevertheless laid down the design parameters not only for Sopwith aircraft to follow but many, many of the aircraft of an entire era. The large transparent sections of the cockpit sides make this a unique Sopwith aircraft, well suited to the modeler who wishes to display as much as possible of interior details.

2) In addition to the history of the aircraft, there is a vast amount of inspiring biographical material that deserves to be related; about persons like Thomas Sopwith himself, Harry Hawker, and other persons with some connection to the Three-seat Tractor.

3) Making accurate drawings of this aircraft in 1/16 scale.

4) Develop these drawings into a detailed paper model, utilizing mixed techniques in addition to traditional paper modeling techniques.

More specifically, I would much like to develop a model with a representation of a full internal wooden framework, plus internal rigging; cut-away covering parts to show selected portions of the inside such as the fuselage and one wing; spoked wheels; a true-to-scale rotary Gnome engine; and of course a propeller which looks like the original.

Many of these subunits, like the spoked wheels, rotary engine, and propeller already exist as paper model designs by others or, in one case (the propeller), myself. I intend to study these, augment them if so required, and draw my own versions of them for this particular model. One version of a suitable wing structure was tested in the 2009-2011build of the 1/16 scale Sopwith Pup.

5) Test-building this model. The challenge for me would be to learn how to construct a wooden framework with internal rigging; techniques for cut-away parts; plus making a pair of spoked wheels for the first time.

These are ambitious goals, and I may not be able to fulfill them more than partly. Even more important, then, to share the work as far as I will be able to carry it forward.

[2012 comment again:] Ambitious goals, I'll say… ! The arrogance one can display at times. Still, the work done is good, and the basic ideas too. So let's continue:

There is of course also a hidden agenda of sorts here: On the historical side, I would like to inspire more people to study the years immediately prior to WWI. These early aviation years are full of exiting designs, personal stories and aeral adventures. Today, there are readily available sources, like the searchable Flightglobal Archive, which together with several other good sources deserve thorough exploration.

On the modeling side I would like to inspire more people to try their hands on large-scale paper models. I know many already do so, but there still seems to be a fear of them as being more difficult. I am convinced they are easier, and regard myself as the living proof of it.

On the design & construction side, finally, I would like to try out some techniques which may bring papermodeling and ordinary scratch-building a few steps closer, without ever passing the limit of what the very ordinary builder would feel comfortable with if he or she should try them. Again, my own limitations would be the guarantee for that.

Again, all kinds of reservations go with this. It is what I would much like to do. What I can do is another matter. Meanwhile, look upon this as a placeholder, something which says "this place is taken" - and hopefully also exerts some gentle pressure on myself to fill it with content…

[Final 2012 comment:] The height of arrogance is to pretend that I hadn't already done a lot of this work. Among it, the drawing. So I uploaded the drawing, as it looks today, to the downloads section: "Sopwith D1 Three-seater 80-hp Tractor Biplane". You can download it and pore over its mass of details as soon as it clears the admin scrutiny (which ought to be sometime later today, Friday 1 June 2012). Here's what it looks like - and both the quality & size of the download (only 2MB) is eons better than this screenshot.

Leif

[rmks2000]

Most ambitious. I eagerly await updates.

[Gil]

I'll say it again, Egads!...,

I can only opt for more...,

Best regards, +Gil

[wag]

Leif, there has been far too little attention paid to designs between the Wright's first flights in 1903 and the beginning of WWI and I'm very excited to see you take on a project from that era. I'll be waiting patiently for updates on this thread.
Wayne

[Leif Ohlsson]

Says my Webster dictionary app:

e•gad (also e•gads)
exclamation ARCHAIC
expressing surprise, anger, or affirmation
ORIGIN late 17th cent.: representing earlier A God

Thank you, Gil! You warm my heart, as always. And thanks Wayne for appreciating the 1910-1913 era accomplishments. I couldn't agree more. 1912, in particular, seems to have been a fantastic year - quite a lot of progress done, and still peace. Bob, good to have an occassion to meet again - but please, please add a line in your signature with your name - I suffer from goldfish memory…

Back to the Sopwith Three-seater:

On a beautiful Summer afternoon at Seaview, near Ventnor on the Isle of Wight



(Above) This photo, and the following three, are strangely evocative. It is a beautiful Summer afternoon at Seaview, a small village near Ventnor on the Isle of Wight. The year is 1913, and on a meadow outside the village an aeroplane unexpectedly has landed, literally out of the blue. A lot of people have gathered, among them a good photographer, Arthur Jellicoe, resident of the island.



(Above) On the back of these photos, Arthur Jellicoe has written that 'the driver' of the aeroplane was one Harry Hawker, with a Mr. Boger as passenger. Above, Harry Hawker is the rather cocky smaller man to the left, and Mr. Boger, flying with him as a passenger, is seen at the right. Less than a year earlier Hawker was a mere pupil at Brooklands, a motor racing circuit and aerodrome on the south-west outskirts of London, and the Sopwith Flying School there, while also being a newly employed mechanic at the Sopwith Aviation Company. On this day. however, Harry Hawker is already a seasoned flying veteran with several British flying records to his name. He has in fact become so good a pilot, that he is now occupying a position as chief pilot and flying teacher at the rapidly expanding Sopwith Aviation Company and Flying School, now established at nearby Kingston on Thames as well as Brooklands aerodrome. Mr. Boger is at this time probably what we would call an enthusiastic 'hang-around' at Brooklands.

For me, this marks the happy, uncomplicated high point of Harry Hawker's flying career. He has really come into his own; he is a celebrity but not completely overtaken by fame; he is often photographed in the newspapers, but still obviously content with where he has ended up. Sure, in just eight years time, he will be even more famous; he will have barely survived a failed attempt to cross the Atlantic; he will have married; and his name will be at the top of the letterhead of the newly reconstructed Hawker Aircraft company - although Thomas Sopwith will remain as the real owner behind Hawker's front. By then he will also, sadly, soon be destined to die after one of the many aircraft he testflew caught fire in mid-air and crashed.

The much less known Mr. Boger will eventually gain his flying permit later that same 1913 autumn. Sadly though, six months after this photo was taken he will crash in his own newly purchased Parson's biplane just a few days before Christmas, and be very seriously injured. Whether he survived those injuries, or what kind of life he had with them thereafter, is in fact unknown.



(Above) But for now, we are still on the Isle of Wight and the Summer sun of 1913 is shining upon all of those gathered. Who are all of these people, drawn to what must have been a most rare visitor in 1913, an aeroplane coming all the way from London? It is a Monday, yet people seem to wear their very Sunday best suits. On the other hand, so does the pilot, Harry Hawker. Mr. Boger is not quite that dapper, but still wearing the kind of attire one would hardly expect from two aviators flying in an open, oil-spitting aeroplane for a full hour. So, this may actually be the everyday attire of the spectators as well, in which case they would appear to belong to the middle classes and above. There does not seem to be any farmers among them, does there?



(Above) I believe I can still spot Harry Hawker, and the more reclusive Mr. Boger in this photo. Can you? In any case these three photos have been absolutely invaluable in studying the Sopwith 80hp Three-seater Tractor Biplane. You can watch them at the original source, where there is an additional photo of the photographer together with some biographical notes about his family.



(Above) I have tried to retrace the Hawker-Boger flight from Brooklands to Seaview on the map above. (In fact, zooming in very close in Google Maps, I sort of imagined I could identify the very meadow where Harry Hawker and Mr. Boger must have landed, including the trees shading the aircraft. All of it pure imagination of course, although comparatively young trees at the time could conceivably have survived the hundred year time-span…)

Flight (June 21, 1913, p.677) has the following note about the flight:

Brooklands Aerodrome. On Monday, last week, Mr. Harry Hawker made a fine flight to the Isle of Wight, carrying with him as passenger Mr. Boger, the journey being made in the good time of 55 mins. Mr. Hawker came back from Cowes in 50 mins., flying at an altitude of 5,000 ft. all the way.

The figures given here translate into an average speed of 94 km/h out, and 103 km/h back, hinting at a south-westerly or westerly wind, which is reasonable enough. The stated flight altitude of 1,500 meters would speak for two quite cold airmen by the time they landed back at Brooklands, summer or no summer…

These four photos from Seaview were taken just about one week after Harry Hawker had set a new British altitude record of 11,450 ft on this very machine. When he got back, he would set a new British altitude record for flying with two passengers aboard on it, and even augment that record a few days later to 8,580 ft. The Sopwith Tractor clearly had a superior performance for its day in many respects.

Leif

[Leif Ohlsson]

I'll continue publishing my collected notes about the Sopwith 80-hp three-seater, in the hope that someone might benefit, and enjoy them:

First apperance of the Sopwith Tractor Biplane

The Sopwith Three-seater Tractor Biplane first appears in the columns of Flight magazine in its issue for February 8, 1913 where it merits just a few lines:

Originally Posted by Flight February 8, 1913

…a tractor biplane … fitted with an 80-h.p. Gnome. It is a three-seater, two observers being accommodated side by side, well forward on the body, where they have a good view. The pilot sits behind them. Control … is operated by a warp wheel, mounted on a vertical elevator column. Steering is done by a foot-bar.

A proper review does not appear until the next week, February 15, 1913. More or less the whole of this issue is dedicated to a very detailed coverage of the aeroplane exhibition at the Olympia, London, which had just opened that week, and I strongly recommend reading or at least browsing it in full since it gives a time-capsule glimpse into the state of the art of aircraft manufacturing at this time (there will be some links to this issue below).

If you do that, take a moment to reflect upon the fact that this number of pages arrived promptly in the subscribers' mailboxes every Saturday. Volunteer correspondents from the various clubs and flying grounds around the country made sure that virtually every practice round was recorded and preserved as a record for us to read a hundred years later, including the name of each hopeful prospective pilot.



Note that the photo above, from this issue of Flight, depicts the tractor prototype. This particular machine would very soon be delivered to the Admiralty, which had commissioned an improved version of an earlier Sopwith biplane. The prototype is very beautiful, but that's not the aircraft which flew to the Isle of Wight to get immortalized by the photos published previously, and it is not the aircraft on which Harry Hawker set his many records.

The next three aircraft built of this type, one of which was kept by Sopwith for demonstration purposes and is the one I aim to introduce and model here, had a different, slightly ungainly fin, protruding also below the fuselage center line, plus slightly less beautifully shaped cockpit top metal covering parts. The landing gear and center of gravity would also be changed for all later versions, so that the empty aircraft would rest on its tail, instead as here on the front auxiliary wheels. Admittedly, not at all as pretty as the prototype, but with a more interesting provenance, as it were…

Flights' reporter starts his coverage of the two Sopwith contributions to the Olympia exhibition at the very bottom of page 186:

Originally Posted by Flight 1913

Two biplanes, one a hydro-biplane and the other constructed for land work, represent the Sopwith Co. on Stand 22. Both were designed by, and the construction carried out under the supervision of, Mr. T. O. M. Sopwith and his works manager, Mr. F. Segrits, at the Company's works at Kingston-on-Thames. They are no freak machines, these two biplanes of Sopwith's, a rough glance over them will soon convey to the observer that they are designed by practical men.

Note here the misspelling of the name of Fred Sigrist, newly appointed chief engineer of the Sopwith works. It would soon come a time where no reporter covering aeroplane manufacturing would ever make that mistake!

The entire next page, 187, is dedicated to the Sopwith Flying boat also on exhibition at the Olympia, and which the reporter regards as the more interesting aircraft. We shall have to turn the leaf to page 188, where we still have no text about the "80-h.p. Gnome-Sopwith tractor biplane", but a lot of very interesting and valuable sketches of construction details for precisely that aircraft. Combined with the text and even more skteches on page 189 these represent a goldmine.

Note however that the machine referred to in the first paragraph below is not the prototype - which of course was the one shown at the Olympita but a precurson, the 'Hybrid' largely built upon the Sopwith-Wright conversion; bought by the Admiralty, as a result of which they ordered an improved version from Tom Sopwith, which in turn led to him setting up his aeroplane manufacturing facility in an old ice-ring at Kingston on Thames, in addition to the Sopwith flying school and assembly plant at nearby Brooklands aerodrome & motor racing circuit. All of which means that we are in fact talking about the first official Sopwith-manufactured aircraft of them all!

Note also, that the cowling of the machine exhibited at the Olympia may have looked slightly different from when it reappears at Brooklands in the photos published here. Flight's illustrator has drawn a side of the cowling with some strange cutouts, or else on of the side covers were removed at the exhibition to display the Gnome rotary engine - which would have been worthy of exhibiting on its own, since this must have been a kind of premiere for the 80 hp Gnome Lambda version of the already famous 50 hp original Omega version; more about this at a later date.

Originally Posted by Flight 1913

The 8o-h.p. Sopwith Tractor Biplane —a similar machine to the one recently supplied to the Admiralty, excepting that the machine has staggered planes, and is fitted with an 80-h.p. Gnome motor.

Its fuselage is of the ordinary lattice girder type, built up with ash longitudinals, and cross and vertical struts of spruce, all of which are spindled down to to an I section wherever possible for lightness sake. The sockets, by which they are assembled, are cut from mild steel, and shaped so that they wrap the longitudinal members, a method by which drilling of the spars and consequently weakening them, is avoided.

The motor, a 80-h.p. Gnome, is mounted in front by bearers on either side of the crank-case. It is direct coupled to a Levasseur propeller, 8 ft. 6 ins. in diameter. A metal cowl covers the top half of the engine, so preventing any oil or exhaust fumes reaching the people on board.




The planes [that would be wing panels in modern terms; my remark, LO] are almost identical with those of the hydro-biplane we have just described, excepting that in the tractor biplane the top plane is staggered 1 ft. in advance of the lower one. Similar built-up spars and struts are used in both machines. For facility of transport the planes can quickly be dismantled in two sections. The end section of the rear span on either side of the machine is hinged to the rigid central section so that the warping may be operated without any internal strain occurring in the wing construction.



The landing chassis is of the combined wheel and skid type. The body of the machine is supported from two long hickory skids by six spruce struts. The two pairs of rear struts are assembled to the skid by a welded steel fitting which is also slotted to take the axle of the two landing wheels. The latter are strapped with rubber cord to the skids.





Miniature skid-tip wheels are fitted. They are 13 ins. in diameter, and are each supported by a pair of beaten steel fittings. The main skids, the sides of which are hollowed out for lightness, are continued back 3 ft. or so behind the rear chassis struts, in such a manner that there is no necessity to provide a rear tail skid. These continuations of the rear skid have the advantage that they act as most efficient land brakes when it is required to pull the machine up quickly on landing.

The tail is semi-circular in shape and has a radius of 5 ft. As in the hydro-biplane, the skeletons of all the tail organs are constructed from steel tubing. The machine is arranged to seat three, two observers side by-side at the centre of gravity of the machine, and the pilot some little distance behind them. The bottom plane is staggered back, the observers are able to obtain a good view of all that is happening below them. The pilot can get a good view below him, too, for the trailing edges of the planes on either side of him are cut away for that purpose.



The Sopwith works have a very neat method of forming an eye with stranded steel cable. It is not an entirely original method, as the writer has noticed it on a number of other machines, especially in France. However, since it has not yet been described in these pages, it may be as well to mention it now. The cable is well cleanded, and on it is threaded a flattened tube of very soft copper. The the cable is turned back, forming a loop, and in the loop is placed an eye. The copper tube is then slipped up, over the loose cvable end until it tight against the eye. It is then twisted several times, and finally the whole job is sweated up together.

Petrol is carried on this machine, in a tank under the passenger's seat. From there it is fed under pressure to a service tank arranged below the motor cowl. Weighing 1,100 lbs. light, this Sopwith biplane, has been designed to carry a useful load of 450 lbs. at a speed of from 65 to 70 miles per hour.

So far what Flights' reporter at the Olympia Air show, London, February 1913, has to say about the Sopwith Three-seater Tractor Biplane. Let's finish this introduction with another photo where the plane is actually carrying its full load of two passengers plus the pilot:



(Above): This photo provides a rather unique view of what it looked like when the Sopwith Tractor actually carried three people - which might not in fact have been that often.

However unlikely it may seem, those caps were apparently, judging from the amount of similar photos from the era, considered standard apparel for flying in an open-cockpit aeroplane without windshields in those days - albeit turned around 180 degrees for the actual flying of course…

The aircraft in this photo is still the prototype machine; the 'comma-tail' fin more than anything giving it away. Also, the main wheel fittings are identical to what is shown in the sketces above, of the prototype. Later photos of the model I aim to model show a different kind of fitting, separate from the struts, and the rear landing gear leg slightly more to the aft.

It is of course impossible to recognize any facial features, but curiously it seems to me that Harry Hawker might be the one closest to the camera in the front (passenger) seat. Which begs the question who is actually the pilot in the rear seat on this occassion. Some sources mention a photo with Tom Sopwith himself, in which case the other person in the passenger seat would be chief engineer Fred Sigrist; but all of this is speculation.

There is a kind of cottage in the background, and some kind of ordinary road. The location is Brooklands, which is born out by another photo taken on the same occasion, where the race track is clearly visible in the background. The three photos of the Sopwith Three-seater published here must all of them have been taken at this same occasion, judging from the angle and background.

[sparrowhawk]

Leif,
this will be a real charmer from the innocent infancy of flight which was to end way to soon in the carnage of WW I.
Once again more than just a building report.

Regards, Martin

[Don Boose]

Just dropped into the Forum after a week's absence and found this treasure. Real Vintage Leif! Wonderful images and narrative and a splendid project to capture another piece of aviation history.

Don

[Leif Ohlsson]

Martin, it is so good to hear from you. Long time..., right? Unfortunately, I am not able to comment on your blue photo recon Spitfire, but I enjoy watching you getting down to this long-time project. Very rewarding to hear that you got the same take on the Sopwith Three-seater which inspired me to dig ever deeper into this aircraft.

Don, I knew you were otherwise engaged. Very good to have you back again! Glad you appreciate the vintage - although only a handful of them were ever built, I regard the 80 hp Three-seater as the "original", archetypical Sopwith aircraft.

I'll finish up the description of the aircraft with some notes on the sources:

Sources - specs, photos, drawings

The outstanding source both for studying the Sopwith Tractor aircraft, and the people involved in building and flying it, is of course the Flightglobal.com searchable archive. You can search for e.g. Sopwith 80-h.p. Tractor, Thomas Sopwith, Harry Hawker, Boger, etc.

Be sure to always limit your search to one year at a time, e.g. 1912-1912, 1913-1913, etc. You get so many hits, that you may miss out on some good stuff otherwise. Can I offer you a tip - search for a series of articles called 'Constructional details'. It started innocently enough with a page of (very good!) sketches in 1915, but soon swelled to a series of 18 installments running all through 1917, all of them with great illustrations. I'll just give you the first one from September 10, 1915 as an example:



However, for our immediate interest in the Sopwith 80-hp three-seater tractor, there's an article from February 7, 1914, and continuing the next week, February 14, 1914 issue. It is called 'An aeroplane in the making' (how's that for an appetizer!), and actually is a detailed report on the techniques used by the Sopwith Aviation Company! (Flight 1914, pp. 148, 149 and 168, 169). Here are three typical sketches, and if you download the actual pages from Flight, you will find the accompanying detailed description in the running text just as detailed and interesting:







Please note that the Flight source is unique in positively encouraging people to copy, reprint, and in all manners possible use what's published on their site.

The second important, more standard source, is of course Wikipedia. Their entry for the Sopwith Tractor Biplane is good for basic data, history & specs. In addition to aircraft, Wikipedia is also a reliable source for biographies.

Now for a more elusive site, the Aviation Pioneers: An Anthology, (part of the Hargrave site, saved at Australia's National Library in Canberra. It, too, is excellent for biographies, and I have spent many hours here.

More recently, I have discovered the Russian site 'Their Flying Machines'. In their entry for the Sopwith Three-Seater you will find all available photos (except the Seaview ones republished earlier in this thread!) collected in one place, plus data & excerpts from several printed standard works. A goldmine for amateur researchers without access to these works.

Finally, but not least important among these sources, the Arizonamodels.com section for reference drawings, propellers, rib profiles, and misc. other details. From this source I got the most valuable period drawings (the best one was in fact German) of the three-seater:





Note that these drawings represent the later version of the three-seater, built with ailerons instead of wing warping. All three-seaters, irrespective of when they were built, eventually got converted to this standard. All of them were also eventually impressed. In military service they were generally flown as two-seaters.

All of the above have been my main sources. They are all goldmines in their own way, and they are good for a multitude of other antique aircraft.

[cardist]

As always Leif, I follow all of your threads with great interest and this is no exception. Part of the hobby for me is researching the period, people involved and the context that the prototype being modelled exists in. What you have provided here goes beyond this. This is living history, the culmination of which should be a true to scale prototype of the original. The sum of what you have produced here is a tribute to the people and the machines involved in this sadly neglected period.
Thank you for opening this window into the past and for sharing all of it with everyone here.
Bernie