Scaled down, but still full of fun – the Isaacs Fury


John Owens Isaacs was an aeronautical engineer with Supermarine Aviation. After obtaining his private pilot’s licence, he was contracted by the Hampshire Aero Club to build a Currie Wot biplane. The success of this project inspired Isaacs to design and build a 7/10th scale replica of that classic fighter biplane of the 1930s, the Hawker Fury. Taking the Currie Wot as an example, his Fury replica was all wood, with fabric covered wooden wings, and ailerons on the top wing only. He selected as the powerplant for the design a Czech-built four-cylinder inline engine, the Walter Micron III, producing 65hp. The aircraft’s first flight was made from Thruxton Airfield, Hampshire in 1963.  Later, G-ASCM was modified to take a Lycoming O-290-D of 125 hp, which rather ruined the lines of the cowling, as the cylinder heads of this flat-four engine protruded on either side.

The Popular Flying Association (now the Light Aircraft Association) approved the Isaacs Fury as a homebuilt design, and sets of plans were sold in the USA, Australia and the UK. Currently, there are at least 15 examples of this pretty, little, (but fully aerobatic) aircraft on the British Civil Register. The aircraft you can see above is an Isaacs Fury II (PFA c/n 1588), and the builder, Michael Clark, solved the aesthetic problem associated with the flat-four engine by means of a highly-polished cowling, which blends the nose contours into the fuselage lines rather well. G-BEER is now owned by Roger Simon, and is wearing the famous black and white chequer-board markings of No. 43 Squadron, RAF. 43 Squadron (motto ‘Gloria finis’ – Glory Is The End) was the first unit to receive the Hawker Fury in 1931; ‘The Fighting Cocks’ were at Hawkinge, Kent at the time. Here you can see G-BEER parked at the Great Vintage Flying Weekend, Cotswold Airport, Kemble.

What of the first Isaacs Fury, G-ASCM (which belonged to the designer from 1962-1968) you say? Well, it is still on the British Register, after no less than 11 owners! The fortunate and current owner of this delightful replica, painted as Fury K2050,  is Roger F. Redknap, of Abingdon, Oxfordshire.

http://bit.ly/TPMFund

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9 comments on “Scaled down, but still full of fun – the Isaacs Fury”

  1. John Isaacs sure did build an aircraft that lasted. His choice of the Hawker Fury is understandable as the design is classical. He scaled to 7/10 — do you know why he chose that ratio? Perhaps he selected the engine and scaled the design to that amount of power, or possibly the engine’s dimensions? An aviation regulation, perhaps?

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  2. A couple of things spring to mind…..

    As you approach 1: 1, you might just as well build a flyable version of the Brooklands ‘static display’ Hawker Fury. For that you really need a RR Kestrel (think, hen’s teeth, here)! Failing that, you might get by with an Argus As440 (Pilatus P2 engine) which gives you around 400 horses, or, you might stagger around the sky on a DeH Gipsy Queen (at 200 hp). These alternatives give either 2/3 or 1/3 the horsepower of the original.

    So, you are stuck with reducing the size and, therefore, the weight of the airframe. The Mikron III only gave 65 hp (from a relatively high dry weight of 132lbs) the O-290-D (in later versions), can be persuaded to give you 140 hp from 264lbs. I know that this is ALMOST the same power to weight ratio, but things don’t quite work on a one to one basis in scale aircraft. Raw power helps!

    If you go SMALLER, you would have problems with control effectiveness (if surface areas remained the same, proportionately), and the moments of force acting around the aircraft’s c of g when control inputs were made would be such as to make the aircraft very ‘tender’ (It is the same argument as the one regarding the point along a lever that force is applied and the distance away from the fulcrum on which it pivots). Also, you would have to carefully select your pilot (Royal Hobbit Air Force, anyone?).

    The War Aircraft Replicas International Inc. designs are scaled at 50%. This is the very lowest that I would suggest anyone go, both in flyability terms (unless you want your feet IN the same compartment as the engine). Also, visual appearance takes over at this point, and the W.A.R. Me-109 looks OK-ish, but the Sea Fury does not. I think 7/10ths is about at the limit, in terms of aesthetics and technical considerations (but that is a personal view, of course).

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  3. I see…so may ripple effects with each change in an aircraft design. With so many compromises to made for a successful design the chief engineer could probably fall back on to a career as a mediator.

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  4. Read what John O. Isaacs wrote on the scale 7/10 finding in his autobiography “Aeroplane Affair”, page 124:

    “At the Aeroplane Club several new projects were considered and I sometimes amused myself by drawing rough schemes… … I was encouraged to investigate a two-seat Wot and a smaller, aerobatic Wot with simplified fuselage and reduced span.
    The rather quaint ‘perpendicular’ impression of the aeroplane (the Wot) stemmed from Joe Currie’s near vertical struts and large interplane gap, chosen to facilitate eventual wing folding. As I doodled at my drawing board, adding stagger to give more dashing lines, the idea of a similar sized Hawker Fury came to me. A quick calculation indicated that a 7/10 scale Fury would produce the right sized aeroplane since the original fighter’s 30 foot span reduced to 21 feet which compared with the 22 feet of the angular Wot. The near perfect proportions of the plan, featuring rounded tips and a shorter span lower wing diminished the lifting area by an acceptable 16 per cent. In the absence of detailed Fury information, I obtained a set of three-view drawings from the Aeromodeller magazine from which I could produce my own outline drawings at the desired scale. A side elevation drawing of the Hawker interceptor superimposed over that of the Wot confirmed how similar the two aeroplanes would be in size, presumably in weight, and therefore in general constructional methods. By good fortune too, little juggling of component positions or areas seemed necessary, subject always to later mathematical confirmation. Excitement grew.”

    Greetings from Switzerland, Claude E. Vonlanthen, owner and pilot of Hawker Fury II, N37896

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    • Thank you, very much for your comment, which provided me with a great deal of background knowledge. I have always thought that the only thing you could wish for in an Isaacs Fury is FOUR ailerons, as opposed to just two! (That would make it roll like a Jungmeister!)

      We shall have to see if someone is willing to make a scale ‘Hawker Demon replica’ with dummy Lewis gun and ‘head and shoulders’ in the rear cockpit, (rather like the Bowers Fly Baby, converted to look like a Junkers J 1).

      More vintage aircraft soon………….

      Ross

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  5. Hello Gents, from Smithy in Australia.
    I am currently redesigning the Issac’s Fury II. I felt this particular aeroplane had not reached its full potential from design and aesthetics view point. My new design will resemble, in good detail, the original Hawker Fury lines and will also include good range, spacial cockpits and the capacity for two decent weighted pilots for extreme comfort with an all up weight of 1320lbs. This weight is our MTOW for Recreational Aircraft in Australia. I plan to have a modular off the self kit available new year.More details will be available soon on : http://www.aerowelding.com.au I would also like to here from owners and builders of this fine machine around the world too please. Many thanks, Glenn Smith
    mobile 0417 854654 – 03 5429 3713 E: smithy@aerowelding.com.au

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    • Good to hear from you, Smithy! Obviously, you are going down the Sidney Camm route with your Fury – although he loved steel tube, didn’t like welding much, (see the RAAF Demon, ‘A1-8’ at Point Cook, and my post on the Sea Hurricane). The Currie Wot – on which John Isaacs based his Fury – is a wooden aircraft, so I dare say you will be making some radical structural changes! The choice of engine will be interesting (Jabiru 2200? 3300?) as this will affect not just the power/weight ratio but the aesthetics of the nose contours, something that I feel could have been handled better in the Isaacs Fury. Please keep us informed. G’day mate, and have a bonza barbie at Christmas!

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  6. Good on ya! Had a bonza barbie at work today …too! Yes, 3300 Jabiru or 4CYL super charged LOM engine. Modular in construction incorporating welded sections. I will be using similar construction methodology in place by the great (‘miles ahead of his time’ ) thinker, Sidney Camm. I have studied many biplanes including the Pitts and Steen Skybolt. I get some small things from every aircraft i examine. I am a professional welder and hold the experimental recreational L2 certification for welding airframes and line maintenance on engines. Iam very excited about this project. I am learning CAD programs now and have existing formulas for Cof G ect so this method should be of extreme use.
    thank you for your wonderful reply, i will check out other posts. Smithy

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  7. G’day Ross, hope you’re well mate, I thought I’d update you. I started mapping out the Fury II as mentioned, Then I came across Lynn Williams, i don’t really need to say more do I …! I found an aircraft that really nailed me, the Matty Laird racer of the1930’s. Lynn had a design based on this called a Flitzer / Laird . The design was originally in timber, however after many conversations Lynn is designing the basic airframe in 4130 now to better handle the Rotec Radial, I will be the person to build the prototype which is a great honor. Well it’s been about 3-5 months now and i have been involved with other developments across the Flitzer range (evolution) such as the new Meteor J6R, which will handle the Rotec Radial too. So the Ol’ Fury is off the board. I am now the Official exclusive dealer for the Flitzer range of aircraft in Australia , this means high support for Flitzer builders and parts here in Australia. My new site is under development http://www.flitzersportplanes.com.au So that’s where I am at the moment Ol’ mate….take care, and best wishes, Smithy

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