I first came across this strange and exotic beast while watching Those Magnificent Men in their Flying Machines. Count Ponticelli, the Italian entrant in the air race from London to Paris which forms the backdrop of the film, was constantly trying out new machines. They were all designed by a character played in the film by Tony Hancock, a popular British comedian at the time, noted for his gloomy demeanour and eccentric opinions. In the film, he designs one aircraft which unintentionally flies backwards, which was based on a real aircraft of the time, the Dixon Nipper.  He is last seen flying it backwards in the wrong direction, towards Scotland rather than Paris, and that Nipper, in a fetching red scheme, looks like a good candidate for a scratch build at some time in the future.

The Edwards Rhomboidal had annular biplane wings, of an immense 38 foot span,  arranged in rhomboidal or diamond pattern, with similar upper and lower surfaces. The rear wings were three times the width or chord of the forward wings. This strange arrangement came about after successful experiments with a rubber powered model, presumably like the rubber band driven flying models that aeromodellers still make.

In fact there is no reason why this layout shouldn't work well. German scientists at the end of WWII were working on forward swept wings, which solve the problem of achieving high speed flight with good low speed handling. The main problems they encountered were the extreme torsional forces on the wing spar. Since the Edwards Rhomboidal had a top speed measured in miles per day, rather than MPH, I do not think it would have mattered very much that the main wings were swept forward.  And while it is a very large beast by contemporary standards, it would be immensely strong with all that cross bracing.

The large structure of the aircraft was formed by a pair of triangular section wire-braced trusses, rather like the box section girders that bridge builders use.  They would have made for a strong structure, being 48 feet long, albeit with quite a weight penalty.  These were vertically connected by thick round struts.

Each girder bore a pair of  flexibly mounted struts extending outwards, the wings being tensioned between the ends of the longitudinal girders and the outer ends of the struts by means of cables which formed the wing leading edges. The trailing edges were under less tension, the intention being that the wings would deform in flight and spread the wing load.

In the film, a replica was made which was not airworthy, and so the brief sequence showing it flying must have been created by suspending the replica from wires. The wings are seen flapping around like flags in a high wind, and it doesn't look remotely airworthy. In fact the linen of each wing was braced internally by chord-wise struts sewn into pockets inside the linen, and so it seems unlikely that quite so much slack was allowed to the wing surfaces on the original.

A rectangular elevator was mounted on the rearmost connecting struts, and a small rudder, above the upper wing. There were no ailerons or wing warping devices, and so lateral control would have been difficult, and any turns would have been flat rather than banked.  A Humber water-cooled engine drove two propellers between the wings by chains. The pilot sat well to the rear behind the engine, presumably to counterbalance the weight of the engine and radiator.  

The undercarriage was a pair of skids each bearing a pair of spoked wheels, with a castoring nose wheel. It was tested at Brooklands aerodrome in 1911, but whether it actually flew is unknown.

Scale plans can be found on one of the websites below, although they are sketchy and it is wise to print out as many photos as you can, and refer to them constantly.

I began with the structure, which one can hardly call a fuselage. The two main trusses were made out of plastic rod, which I pinned to a sheet of balsa wood for handling. The construction is simple though time consuming, and should be familiar to anyone who ever made a balsa flying aircraft kit. The two wing support girders can be made at the same time, though note that they are bow-shaped and meet at each end. A few cross bracing struts were added here and there, and rigged as in the pictures.  

The main trusses were joined with thick rod, and then the wing supports can be glued to the main trusses. The whole was given a coat of wood paint, for which I used Lifecolour Mid Stone from the UK range.  

The wings were then cut to plan from 5 thou plastic card, and ribs were scored underneath using a steel rule and black biro. Leading edge struts were added from rod, but the trailing edges left unsupported. The scoring automatically left the wings curved and I left them like that to simulate the wind getting underneath them. The original had bracing wires under the trailing edges, but not under great tension to allow free movement in the wind.  

The most complicated part was the engine and propeller module, which I made from lengths of rod surrounding an old inline four engine I had in the Bag of Engines in  spares box. A prop shaft was added behind the engine, (prop shaft as in car, not as in aircraft) with two discs of plastic to represent cogs. Propellers are wide and fan shaped, and were cut down from an old Corsair prop I had in the spares box. Each blade was mounted on some plastic tube and threaded on a rod which fitted into the structure. Together with two discs to represent the prop cogs. Thin rod represents the drive chains.

An old car radiator was cut down from something which had long since gone to the junkyard in the sky. I suspect it might have been an old Airfix 1911 Rolls Royce since it has that classic Gothic shape. You could as easily scratch one from scored card. A seat was fashioned out of two slabs of card with a little putty for cushions. The tailplanes were thin card, scored for the ribs.

Finally the undercarriage was made from strut and rod and two axles mounted at the rear of each skid, with two pairs of Eduard etched WWI spoked wheels. The tires were made first from solder wrapped around a thick pencil. The front end was simply more rod.

 And as so often happens when you think you have finished, the model was placed on the shelf and promptly reared up and dropped onto its tail. Yes, it is the very first instance of a tail sitter, dating from 1911.  

Simple, I thought, we will simply remove the nose cone and pack it with lead shot.  Alas, a moment's scrutiny revealed it has no nose cone. In fact the whole aircraft is so devoid of skinning it is transparent. So the radiator came off, and the rear surface was lined with small slabs of lead sheet. That did the trick, though don't overdo it or the whole vast beast with become knock kneed, and sink onto its belly, like a dying dinosaur.

This should be well within the bounds of anyone who has done a little scratch building and it might even make a good starting kit. Construction was time consuming rather than complicated. And there are no compound curves to worry about. I suspect the original was put together by a blacksmith and a cabinet maker, and wouldn't have presented either with any great challenges. If you take it down to a club meeting, it will baffle all those experts who want to crawl all over it with scale rules and declare that you are a millimetre out in span. Let's spread a little confusion to the enemy.

http://www.impdb.org/index.php?title=File:ThoseMagnifient74.jpg 

http://flyingmachines.ru/Site2/Crafts/Craft28410.htm 

http://celticowboy.com/Round%20Aircraft%20Designs.htm 

http://www.j2mcl-planeurs.net/dbj2mcl/planeurs-machines/planeur-fiche_0int.php?code=2394 

http://www.picssr.com/photos/27862259@N02/page719 

Chris Peachment

August 2014