(Suggested by Nick Rogers)

The following regarding the above project which several of
our entry were involved with, should you have any information
material or photographs you wish to add please email Bob.

Below from Chris Lowe (click to enlarge)
CL-020416-19-Jupiter.jpg (106276 bytes)

This is the author`s own plane, so here is an account of it from the first person.

SUMMARY of its history

1961 The "Hodgess Roper" design. I designed a tailboom-configuration HPA.This 1961 design is referred
to by Lilley (April 1983), and elsewhere, as the "Hodgess Roper". This was never built. although I bought
the tube for the tailboom, and some of this was used to make the pylon of Jupiter.

1962 The design was rethought and lessons learnt from accounts of SUMPAC and Puffin.

1963 "Jupiter" design. I designed Jupiter, and started to build it with the help of Susan Roper and others,
calling ourselves the Woodford Essex Aircraft Group. We received a grant from the RAeS MPAG for
the Jupiter-design project. At this stage it was referred to by some as the "Woodford".

1963-1968 Much of Jupiter was constructed at Woodford, Essex, by myself and others.

1968 I was prevented by ill-health from continuing.

1970 All the hardware was handed over to John Potter, ( then Flight Lieutenant J. Potter MA RAF ).

1970-1972 The project continued at Halton under Potter`s leadership, with the help of 99 others,
including myself. completing the construction.

1972 Jupiter, my 1963 design, built at Woodford and Halton, first flew. All the best flights were in that year.

.Subjectively, my seven years of effort were well rewarded by being able to observe the excellent piloting
of John Potter and others including Roger Hardy ( see Dragonfly).


Some histories of Man-powered Flight present inconsistent and even self-contradictory facts about this aircraft.
This is understandable considering that the name changed from "Woodford" to "Jupiter", and I shortened
my own name, ( at the same time as my brothers) from "Hodgess Roper" to "Roper". and Susan`s surname
changed from "Jones" to "Hodgess Roper" when we married and then to "Roper".

From the bibliography, I recommend John Potter`s accounts of the flying aspects and the articles in
Aeromodeller March to June 1973.





                 79.6 feet 24.3 metres



300 sq ft 27.9 m2

Aspect Ratio


Root Chord

5.59 ft 1.71 m

Tip Chord

2.23 ft 0.68 m


NACA 653618


5 degrees from 0.21 semi-span

Aerodynamic Twist 

2 deg wash-in root to 0.21 semi-span 6.5 degrees wash-out 0.21 semi-span to tip 4.5 degrees wash-out overall

Mean aero. chord 

4.03 ft 1.228 m







Span (total)

 25.2 ft 7.7 m

Area (total)

24.2 sq ft 2.25 m2


Up 17 deg, down 17 deg (Alternative rigging, not used, up 45 deg down 0 deg )



Horz. Tail


All moving



15.0 ft 4.57 m


27.5 sq ft 2.56 m2

Total travel

36 deg


NACA 63012

Tail Arm

20.5 ft 6.25 m

Aspect Ratio




Vertical Tail 

Total Area

24 sq ft 2.23 m2



11 sq ft 1.02 m2

Aspect Ratio


Tail Arm

21.5 ft 6.55 m

Max Deflection

30 degrees


NACA 0012 - NACA 0006




Max Width

1.75 ft 0.533 m


Overall Length

29 ft 8.84 m

Max Cross Section

8.25 sq ft 0.766 m2

Undercarrriage Type

Driven main wheel, non-castor tailwheel

Wheel Diameter

24 inch 610 mm front, 4 inch 101 mm tail





9 ft 2.74 m


Gear ratio pedal to prop

adjustable on ground, 1.5, 1.7, 1.9(initially set at 1.7, 1.9 was favoured)

Assumed pedal cadence


Rotational Speed  

108, 120 or 137

Groundwheel gear  

69 inch 1.75 m(adjustable to 89 inches 2.26 m)



Design Flight Envelope




Max Load

154 lb 69.8 Kg ( 170 lb, 77Kg was carried )

Max permissible AUW

300 lb 136 Kg ( 315 lb, 143 was flown  )

Design Manoeuvering Speed 

20 mph 8.9 m/s

Design Diving Speed

30 mph 13.4 m/s

Ultimate Factor

2.5g to -0.5g



cg position intended

25% to 31% m.a.c.


measured 20 Nov 1971




150 lb pilot leaning forward 

27% m.a.c.

150 lb pilot mid-position

31% m.a.c.

150 lb pilot leaning aft

35% m.a.c.



Weight of components

March 1963

20 Nov 1971


original estimate lb (Kg)

measured or derived lb (Kg)


67 (30.4)

92 (41.7)


6 (2.7)

8 (3.6)

Forward Fuselage

18 (8.2)

15 (6.8)

Rear Fuselage

11 (5)

14 (6.3)


2 (0.9)

3 (1.4)


12 (5.4)

14 (6.3)

Total Empty

116 (52.6)

146 (66.2)


Was Jupiter an experimental aircraft ?

An experimental aircraft :-

Out of these four, Jupiter scores about half a point, thereby contrasting strongly with most HPAs.


Very few innovations. Similar to its immediate predecessors in many respects.


During its design stage and all of the construction stage which required assembly jigs, Jupiter was under the
control of an engineer. During its flying stage it was under the control of, and at the base of, an operating
organisation, the Royal Air Force. The relevance of this "delivery" lies in differing learnt attitudes of the two
people. As an engineer, I was used to thinking of an aircraft as something that one designed and built. John Potter,
an RAF pilot, who had also flown with the Cambridge University Air Squadron was accustomed to climbing into
aeroplanes and flying them.


John Potter achieved a very hign usage of the plane, unusual in the sixties and seventies. he also fine-tuned
the "engine", doing much cycle-training, Although he found himself at the helm of an overweight aeroplane of
mediocre design, he concentrated on achieveing longer flights and was thus able to claim the World Distance Record.
Those responsible for other HPA. such as Puffin 2, made many changes to the lateral control system and concentrated
on trying to make the plane turn. With Jupiter it was not so much "let`s change this and see if it makes it fly better", as,
"let`s pedal harder this time".


Jupiter flew without needing any alterations, straight from the drawing board. The only modifications made after the
first flight were the addition of a chain tensioner and of instrumentation.

Thus it can be claimed that Jupiter was the first non-experimental HPA. What was certainly true was the benefit to be
gained by having a person of one background leading during the construction stage, and a person of a different
background leading during flying.



" One of the first things I was taught at school was that I had spelt my surname wrong. To prove teacher wrong took
twenty-four hours. I took my birth-certificate to school the next day to show that I had spelt it right. "Another thing
I was taught at school was that in order to fly by your own power you would need arm muscles six feet (two metres) thick.
To prove teacher wrong in this instance took twenty-seven years and the help of a lot of other people.


I have always been interested in off-beat vehicles. In 1947, when I was 10 years old, I made what was effectively a
skateboard. Unfortunately this was hampered by a fifth wheel in front for steering, and was much too long.

 Later, when cycling down and up the valleys of Berkshire in my early teens, it often occurred to me, when about to
descend a hill, how good it would be to be able to cut across in a straight line through the air to the top of the next hill.


I was an aircraft engineering apprentice from 1953 to 1958, and a design draughtsman until 1961, thereby gaining
experience in many departments of aircraft-manufacturing firms, both in the technical offices concerned with design
of airframes (not engines) and in workshops. With the possibility of sometime building an HPA in mind even then,
I wanted to get experience in one of the offices concerned with production (analogous to the builder, rather than the
architect, of a house. Quantity production is not necessarily implied; the `production' departments are busy on
prototypes as well). However it was generally considered necessary for an apprentice to be versed either in design
or in production, but not both, so I never worked in a production office. My main hobby was building canoes and
then paddling them. These were all made with a spruce framework onto which was stretched a canvas skin.
("Fibreglass" was being used by others for some sailing dinghies). In one of these canoes I travelled down the
Thames from home, and then around the coast and across to France, camping overnight on the way


The 1950s in Britain were a time of expansion. The Festival of Britain in 1951 showed that the nation had got
its breath back after the war. For the first time ever there was a `youth culture' exemplified by rock-and-roll,
and there was the money to buy gramophone records, teddy-boy clothes and motor-bikes. The power of
youth was increasing and in 1958, as conscription for two years of `National Service' ( the draft ) ended, many
males suddenly discovered that they had two years of unexpected freedom.


In 1959 I was feeling that I would like to attempt something more original than another canoe and was wondering
whether to build a human-powered submarine or a human-powered aircraft, and had started calculations
and sketches for the former. Nobody offered a prize for a human-powered submarine in 1959, but I can remember
being at home in my parents' suburban house where I lived, one lunchtime that November, and turned on the
wireless to hear, as the valves warmed up, `...businessman has offered a prize of five thousand pounds for
the first man powered flight. Our next broadcast .... '. I wasn't interested in their next broadcast, and
suddenly I wasn't interested in submarines either. I reached for my slide-rule and started to calculate how
much wing area would be needed. At this time I was more ignorant about what an HPA would look like than
anyone reading this, although within a few months I began to get to hear of Mufli and Pedaliante through
the RAeSMPAG. The details of the first Kremer Prize were not published for two months. I made a mistake
that was consistently made by many people for several years, namely to suppose that anything that
could fly would be able to get round the figure-eight course. I was a 22-year-old with no tools but those I
built canoes with, and those I shaved with. I did have a Higher National Certificate in Aeronautics, and I was
full of optimism. I even convinced myself that my ignorance on the subject of engines was almost an advantage
on a plane that would not have one! Muscle-powered-flight had never been accomplished and maybe it would
never be, but if anyone was going to, it might as well be me.


There was another big event in my life in 1959. I met Susan Jones, later to become Susan Roper. This
was three weeks after the Kremer announcement. Before long I had to tell her `Look, I am building an aeroplane',
`I will help' she replied. I was 22, she was 19; we thought it would take two years. As it transpired she devoted
eight years of her life to me and to the project. We married in 1963.


It never occurred to me that any type of aircraft other than a monoplane would be the appropriate layout. A
cycling attitude for the pilot was chosen because it would require no experimentation. Bicycles work.
You can take a dynamo drive off the wheel ( for the lights). I would take the propeller drive off in a similar way.
However, there was no point in the weight of two big bike wheels and centre-of-gravity calculations of my first
sketches showed the ( single) wheel position to be interfering with where the pilot's feet should be.

To make the pedals and wheel concentric as in the "penny-farthing" bicycles seemed to solve this, and my
1960 design had this feature. This dictates a minimum wheel size for the feet to clear the fairing
(see fairing in Glossary) and the fairing to clear the ground. During various re-thinks, this layout for
the front end remained

. My brother Geoffrey and I conducted some tests bicycling up and down a hill to determine power-output
and air-resistance of the unfaired cyclist. The strengths of a few wood/glue/wood joints were tested. My job
at this time was design draughtsman for metal aeroplanes. I needed to fill out the gaps in what I would need
to know. At about this time,(early 1960), I visited The Cycle Show, an annual event in London, to see if
there was anything which might be relevant. On one of the trade stalls were displayed a number of samples
of chain. `Do you have a chain that twists ?', I asked. `Our chains do not twist' was the emphatic reply of the
salesman. I then took hold of one end of the yard long sample of 8mm pitch chain with my right hand and of
the other end with my left hand - and twisted - easily. I looked at the salesman. `Our chains do not twist' he
repeated in exactly the same tone of voice. The drive chain for Jupiter was therefore acquired through
a stockist, rather than direct from the manufacturer. This chain is about a third the weight of bicycle chain. 
For test, I made, by hand, an 8mm chain-wheel and sprocket to suit my bicycle and road-tested it for a year,
before it showed signs of wear.


 There are various methods of arriving at the best size of wing and of making the other quantitative design
decisions. Since that time it has become common to set up a computer program, but this will often be
preceded by one of the more primitive techniques. I saw that the most important thing was to so arrange
matters ( "arranging matter" includes the quantitative decisions) so that the pilot would not have to pedal
harder than necessary. The job was to find the combination of span, area and other parameters which would
produce the lowest value of required power. Thus the power-required would be the parameter which would
be optimised,(ie minimised). All these things that are being varied are numerically definable, and at this stage
exist only hypothetically. But the final sizes chosen will be translated into concrete reality. I would list a set
of values, sufficient to define the size and the general shape of the aeroplane, seeing always that each value
was within practical constraints, and then calculate the result, namely the required power with that set of
dimensions. Then one of them would be varied and the process repeated. In order to do this one needs a set of
assumptions, for instance as to the manner in which increasing the size of the wing will increase the weight.
I made the best estimate that I could, which at that time was based mostly on guesswork. No-one knew for sure
how much a 60 ft (18.3 m) HPA wing would weigh, or even how much less it would weigh than an 80 ft (24.4 m)
HPA wing. Although I had studied aerodynamics, there was a certain amount of guesswork here as well,
because although the principles of flight were to be the same as for any conventional aircraft, the expected
profile drag could not be accurately predicted, since flight would be outside the range of Reynolds numbers
which had previously been of interest.


The aerofoil section chosen for the wing was NACA 653618 which seemed to be the most appropriate. I boldly
extrapolated the published drag figures down to the relevant Reynolds number. The second 6 denotes camber,
and of the sections of various camber for which ordinates had been calculated and test results published, this was
the most cambered section. It did occur to me perhaps to try to squeeze a little more lift out of the wing by adding
another 2% camber (2% of the chord, over the length of the chord). This would have meant extrapolating beyond
the published data. I decided against this, because I preferred to stay with what had been proven and because
down-ailerons would be adding yet more camber still. Meanwhile the Southampton group had done just this,
but they knew that they could tunnel-test their own section.


One of my colleagues at work suggested making a test-section of wing: a few feet of span, at full scale.
Making this would serve many purposes, provide an estimate of the likely weight of an entire wing, demonstrate
and provide practice on a form of construction with a good enough surface profile shape and give an indication
of feasibility in general. I discovered that thin wooden panels warp, and this is particularly the case when it is
covered and doped. The shape of this test-piece was awful. This was clearly an aspect of the project that
would need further attention if a laminar-flow aerofoil was going to be used, and for a while I considered basing
the design on a non laminar wing section, which would not need such accurate construction.

Either I had to find a way of making the thin panels which formed the outside shape retain their correct shape
accurately without warping. or else resign myself to the fact that they would warp, in which case I would switch 
to a different shape which can be built lighter.

It is an either/or decision laminar or turbulent flow section. Turbulent flow creates more drag but the wing can be
built lighter because it does not need to be so accurately made.


Initially, these various items of work such as tests, calculations and finding what chain and other necessities
were available were not well co-ordinated. When RAeS grants towards HPF projects were announced in mid
1960, I started to prepare an application for one of these. The grant application forms of that time requested
information on many relevant aspects of the project, some of which I had considered insufficiently, if at all.
Thus I was encouraged to consider the project as a whole, rather than just parts of it.


My 1961 design, the `Hodgess Roper', showed a span of sixty feet (18.3 m), an area of 200 sq.ft (18.6 m2),
and the pilot without a fairing, although I wrote that this could always be added later. On the drawing, the
propeller was just aft of the wing, and from behind the propeller hub extended an aluminium tube, at the aft
end of which the tail surfaces and a skid were fixed. As far as I know, this was the first drawing of a propeller
concentric with a tail-boom; although the design published by Beverley Shenstone in 1957 showed the
propeller in a similar position but around a more normal fuselage. The time-estimates which I quoted in the
grant application were little more than guesswork. The grant was not awarded, but the experience of having
made the application was useful. I continued to refine the design, and to make tests. Also I attended all of the
RAeS lectures on the subject of HPF which were more frequent than annually then.


I decided to make the propeller first. I felt that being the smallest component it committed me the least.
Also I felt that if I could make this complex shape then I could certainly produce the simpler shaped components.
It was very satisfying to see the blades swing. In the front room of Susan's flat a jig of 2 inch by 4 inch
(50 mm by 100 mm) timber was erected for the construction of the tailplane. This jig was subsequently used
for the other tail components. Susan was helping with the construction, working to a high level of accuracy.


The aluminium tube that I needed for the tail-boom, 2.5 inch (64 mm) diameter and 0.022 inch (1 mm) wall
thickness, was not a standard size, but British Aluminium Co Ltd quoted me 19 pounds 6 shillings and eight
pence for 4 lengths of 17 feet (5.2 m). This was ordered in November 1961 and arrived in January 1962.
It was the most expensive item up till then.


The tail components were completed and assembled to one of these lengths in my father's garden, taking up
half the lawn. One of my sisters boldly declared that any aeroplane which you needed to pedal would not be
so good as one that you did not have to pedal. To a greater or lesser extent my other four siblings gave
occasional help, and tolerated the monopoly of the lawn. The work was being done mostly by me with
assistance from Susan. Despite the domestic surroundings, I was working as I would on any aeroplane.
A record was kept of the weight of each part, and testpieces had indicated that each part would be
strong enough to withstand the loads which I estimated would be applied in flight. Looking back,
I can see that I was excessively aping standard aircraft practice, for instance ball-race-pulleys were used
for the control surface hinges. Another mistake was an over-elaborate detail design. The tailplane tips
were built up like half a model-aircraft fuselage with their own frames and stringers.


It began to occur to my father that there was not going to be room for the wings in his garden, and he
contacted Sir Stuart Mallinson who was one of the more colourful characters of an otherwise dormitory suburb.
His grandfather had started the Mallinson plywood factory, which had flourished, and Sir Stuart had a large
estate bordering Epping Forest. He was a prolific benefactor and interested in sport and in enterprise.
A part of his estate was open for Scouts to camp in, and he was allowing Christine Truman (then Wimbledon
centre-court frequenter) the free-run of his tennis-court. Sir Stuart was invited to view the tail on the lawn.
He was impressed. He would provide spruce for the wing-spars and advice on how to use it, and he
offered the use of a double garage for construction. In August 1962, Susan and I carried the components there.


The new surroundings elicited a new approach from me, and I began to re-appraise the design. I was now
free to think wing. I took advantage of accounts of SUMPAC and Puffin, and I now had the
experience of the tail fitted to the boom.


The first job at Sir Stuart's was to make another wing-test-specimen. This was of 3 ft (0.9 m) span with the
same 5 ft (1.5 m) chord and the same taper as at the centre of the proposed wing. After many amendments
this proved satifactory in all respects. We developed the technique used on Puffin of using sponge under
 the Melinex. The weight was less than estimated. Crude timber girder extensions to the spar at
each end made a thirty foot bridge, the wing-specimen being the centre-section of the bridge. Thus the specimen
could be tested structurally. On first tests the joint fittings to the extensions, which were to the design of the
transport-joint fittings of the actual wing, tore away from the spar. Mallinson's (Sir Stuart's firm) made up some
special sheets of birch ply bonded to light alloy. The fittings were cut from these sheets and then glued to the
spruce booms using wood glue. These held. However there was one thing that those working in Sir Stuart's
garage could do, and those in his plywood factory couldn't. That was to make Balsa-plywood. We heard from
members of their technical department that the Puffin group had approached them with just that request, and
Mallinson's said it couldn't be done. Puffin I wing was skinned with a single thickness of Balsa. This involved
the complication of a two-cell torsion-box, the grain of the wood being different in each, so that torsion in
either sense would be resisted. We had already been using our home-made Balsa ply on the tail-components
of the 1961 design. The details of how to make such panels and other techniques used are described more fully
in `Aero Modeller' (Roper 1973). I used the data from the weight of the test-specimen, and each part of it, to
re-optimise the wing, and to finally establish Jupiter's wing dimensions. The actual weight of the wing was in
excess of the value estimated from this test-specimen. To a considerable extent this was because we could not
control the weight of glue on a large assembly so readily as on the test-piece; for on a large assembly there
is an urgency to get the whole area wetted in a certain time. John Potter quite rightly blames the Woodford
people for this (Potter 1973).


The ordinates for each of the 55 rib stations along the wing were calculated by a colleague of my brother
John Roper who, on the staff of Manchester University at the time, had access to one of the few computers
in the country. My brother offered other computer-help, but I didn't know what other questions it could answer.
Writing programs and even the range of programs that could be written were mysteries known, at that time,
only to a few. Optimisation was done by calculating a series of values by slide-rule, and plotting graphs.
The prop design was particularly tedious and took 3 weeks use of logarithm tables.


Spruce and Balsa were ordered and we launched into the construction of the wing. This had a main spar at
40% chord, with spruce booms and Balsa-ply web. Skinning with Balsa-ply between there and a front spar
at 7% chord completed the torsion box. The nose forward of this was skinned with spanwise grain Balsa.
Ribs forward of the spar were of 1/16 inch Balsa-sheet and were stacked in a pack 20 inches high and
sanded to profile together. Aft ribs were Balsa girder construction. The only jig used for the wing was an
18 ft long bench. The spars, skin panels and the five sections of the wing were all made on this bench.


               The author building the wings


I came to adopt a policy of inviting someone to join us only if they could demonstrate an ability to
perform at least one relevant task better than anyone else in the group. Susan and I had help with
construction from John Bowan, Martin Gelling, David Green, Victor Hurran, Eric Gilbert,
Helen Kuczinska, Geoffrey Roper and Jennifer Roper. Victor Hurran, who was a student at the
City University, London at the time, was able to make an analysis of the aircraft's flight
dynamics, with other students including Dave Newby. This counted as part of their course and
they used the college's computer. The result was that a dihedral of 5 degrees was recommended
for stability. Alan Vincent, an ex-colleague of mine, gave design advice from a prospective
pilot's viewpoint. On one occasion he took Susan and me in a light aircraft to West Malling,
one of the airfields we were considering.


In January 1963 I redesigned the fuselage. The existing tail components and the propeller were to
be modified to suit. I discovered that a propeller, efficient under the flight conditions of the new design, could be made by adding 9 inches (230 mm) to the tip of each blade. The lower part of the old fin became the upper fin on the new configuration. The original ball-race bearing is still there at the top of the fin. At this stage the original tailplane was incorporated, but before flight this was replaced. Tube as bought for the boom was ideal for the pylon structure. I realised that the pitching moment of inertia on an HPA was likely to be considerably smaller than the moments of inertia about the other two axes. In the belief, at the time, that flight-dynamics would be improved if this disparity was minimised I drew Jupiter with a long fuselage. In deciding the wing position relative to the fuselage, there were three considerations :-

In a 5 degree bank, the wheel must be the lowest point.

The lower the wing , the more beneficial ground effect.

Interference drag must be minimised.

( Nowadays, more attention is given to interference drag and less to having a low wing)


Having heard of the problems SUMPAC had encountered with interference drag at the pylon to wing junction, I gave very careful attention to this area. In our case the top of the canopy would also be above the wing. It was arranged that at no point would the region behind maximum thickness on any two of these components coincide. The base of the pylon has greater chord than has most of its length; not, as it might appear, for structural reasons but so that for the thickness necessary for chain clearance a section of lesser thickness ratio may be employed. The small pod at the top of the pylon could have fulfilled its task of fairing the top of the transmission without protruding forward of the pylon.

However, drawn like that it looked hideous, and a few square inches of area were added for aesthetics. The shape of the front fairing was dictated by my choice of a cyclist attitude pilot, and this was faired in to a glider-style rear fuselage in a functional manner. The point of inflexion of the "S" curve so formed was arranged to coincide with the joint of the fairing. The rear-fuselage was designed with stringers along the sides and top to split the Melinex panels down to a size which would not flap, and to keep the Melinex away from the struts. They would also reduce the effective strut-length of these members. Because of a misunderstanding these stringers were actually assembled inside the struts. The lower fin neatly houses the tailwheel and reduces the torsion applied to the rear-fuselage under rudder loads, by partially balancing the load from the upper fin. It was proportioned so that rear-fuselage torsion resulting from side-load on the tailwheel had the same magnitude as in the rudder-applied case.


Susan had kept us in touch with the RAeSMPAG, and in February 1962 it was arranged that Beverley
Shenstone would visit. This was his year as President of the Society. I couldn't believe it. He came.
He was impressed. "That looks more like an aeroplane", he said, looking at my drawing board.
This despite the fact that the scheme of having the propeller concentric on the fuselage, as originally
proposed by him for HPA in 1957 had been abandoned. He saw the the pack of wing-nose-ribs which
was declining in height as we took them off the top for assembly to the spars, - indicating progress.


We applied for a grant from RAeSMPAG funds for completion of Jupiter, to my 1963 design. We were
successful. In total, nine increments of 100 were claimed. On each occasion we had to justify past
expenditure. There was minimal delay, because of the system of delegation then in use. Many materials
were given free by the manufacturers, and Sir Stuart was providing space, heating and lighting.
Wing construction continued during that year.

In 1964 I turned my mind to the details of the transmission, and this and the seat frame were made.
There are four rotating parts. The pedals and wheel are concentric, and a chain from the pedals
drives the layshaft at a gear-ratio of 2/1. From the layshaft a chain twists up to the propeller shaft and
another chain takes the drive back to the wheel. This all worked satisfactorily when a spring-tensioner
had been added to the propeller chain. The layshaft was arranged to rotate at double pedal speed
in order that a Bradshaw spring could be incorporated.


This is a device to reduce the cyclic variations in torque which occur when anyone pedals anything.
A crank on the layshaft is connected to a spring. This spring will be loaded while either of the feet are
at the front and will unload, returning its energy, to help carry the feet over the top and bottom of the stroke.
On Jupiter the shaft was made to suit the fitting of such a crank, but no arm or spring was ever fitted.
Manufacture of some of the transmission components and the brazing of the seat frame were done outside
by specialist firms. The rear-fuselage structure was made and by July 1964 we were able to invite
Mr Shenstone to witness testing of the transmission system. He sat and pedalled it himself and the
propeller spun and rustled the leaves on the trees of Sir Stuart's famous arboretum. Wing construction
was complete by the end of 1964.


I had considered all the possible combinations of pilot-hand-movements to correspond with each of the
control-surfaces. It annoyed me that the only logical one was a copy of the Puffin. Already the nose
looked like that aeroplane, and I would have liked to show some originality.
I rigged the controls so that rudder operation is in the same sense as the steering of a bicycle. Later I learnt
that the Hatfield group had followed an aircraft-rudder-bar, which is the opposite way. Another innovation
was to make only part of the length of the elevator twist-grip movable. I felt that this would enable more
precise control. I couldn't imagine applying aileron and not inadvertently applying elevator without a
fixed part of the hand-grip to hold onto.

( In later years, I have observed such an arrangement on bicycle handlebars for the gear-change.
I believe that mine was the first.) Aileron linkage was designed with two options. The first was a simple
linkage so that one aileron moved up the same amount as the other moved down (Max. +17 degrees, -17 degrees).
The other option was to have one move up and the other not move (+45 degrees, -0 degrees). This would
involve restraining springs. John Potter did not like the idea of springs and only the simple system
was used. The control bar and some of the control linkage was completed at Woodford, Essex.
All the Balsa hoops for the cockpit canopy were made and this was partially assembled. At this time, it
seemed evident that Jupiter would fly. It also seemed evident that it was unlikely to fly the Kremer
figure-eight circuit since it was similar to others that had not done so. However I was confident that
since there were so many "measures" such as altitude, turning ability, duration and rate of climb, that
there would be one at which my design would excel, but couldn't then specify which of these. As
things turned out, John Potter decided to go for distance, and made a record. The plane was also
recognised as having the most accurately made wing-profile. I hadn't seen the other wings and
assumed they were being made as accurately as ours.

                        The author and Susan Roper checking the controls of Jupiter


Some visitors to the workshop treated the partly-built aircraft as though it was more fragile than it really was, but sadly that didn't make up for the others! Bitter experience showed that usually there is a complete lack of appreciation of what can be handled and how; in particular, that a half-built component is more vulnerable than it will be when complete. `Friendly' photographers assumed a divine right to anything and were amongst the worst. No malice was involved, and therefore further damage was often done when they tried to `just put the bit back again'. Notices were found to be useless, verbal requests little better. One ruse that was found to work quite well was to realise that they WILL handle something, and to hand them an old testpiece. Another is as follows. In order to help prevent ourselves from blundering into anything that mattered, we had been found it worthwhile to arrange a few inches of scrap wood jutting out from any component so that one only snapped this stick off if passing too close. Use of these sticks provided the clue to the most effective guard against visitor-damage. A few more were added, typically along the span, and it really did work like magic in keeping anyone off. Present someone with a component in its assembly jig, and they would always reach forward and feel it. Fix a few two foot lengths of 1/8th inch square Balsa projecting from it, and although they were perfectly capable of reaching past these spikes, experience showed that they just didn't. Surprisingly, it works. This was my experience in Sir Stuart's garages. It is true that the spike principle is effective in minimising damage both from constructors clumsiness and from outsiders. However it is clear that at best this is only part of the answer to a problem that I failed to solve. Another recommendation, which again is only part of the answer, is to acquire a trailer at an early stage and use it to store any parts not being worked on. You're going to need a trailer eventually anyway.


Another of the mistakes I was making was not to realise to what extent skills other than engineering were needed.


It was around this time that work started to slow down. Half of what remained to be done was being done each year. On this basis it would take forever. The reasons for this were all organisational, not technical :-


The authorities at various airfields were contacted. In some cases they even said `Yes, bring it here', but the plane was not ready at that time, and we could give no definite date when it would be. In other cases hangar rent was prohibitive. It was realised that a grass field would not be adequate.


During 1963 and 1964, over half of an aircraft was built with not much more than one person working normal hours. If we count this as equivalent to 1 1/4 people, this implies 10,000 hours total construction time. Figures of the same order were quoted by members of both the Puffin and the Toucan groups. Thus the basis on which the work had been progressing could be said to have been satifactory, if it could have continued. At this rate construction would have been completed during 1966. However, the time involved in making arrangements for a move was not now (1965 onwards) being spent on construction. It was also felt, at the time, that more people, conversant with the project, would be needed during and after any move.


From 1963 onwards, Sir Stuart had provided building space, and materials had been donated by firms or bought from the RAeSMPAG grant. Domestically, Susan had been the sole breadwinner, thus supporting me, but this had meant that money available for luxuries amounted to little more than the cover price of "The Observers Book of Astronomy". There was no money or hope of money to cover moving and flying expenses, nor the additional domestic costs this might incur, although we had gone as far as obtaining a small caravan and locating this close to an airfield at which we had been given permission to operate the aircraft. However the airfield circumstances changed, and the caravan was towed back to Woodford, Essex.


`Oh, I would never have the patience, I am surprised you have', was a remark often made by someone seeing the amount of work involved. Logically, it can be inferred that the magnitude of the speaker's surprise would have been less if morale had started to drop after two years rather than after three years. But it wasn't so much patience running out as losing a sense of direction. I was motivated to make the spars and ribs because I could see that these would form the wing. I was motivated to make the wing because I could see that this would fit to the fuselage. But there is no incentive to complete the construction unless it can be seen that there are the airfield arrangements ready for the next step - flying. Love blinds, but I have heard Susan described as a very sensible person. Her support, right up to helping arrange the handover demonstrated an exceptional strength of character and level of commitment. But she also, after so many years of the lifestyle we had chosen was feeling and showing the strain. The strain of thinking up answers to `When is it going to fly?', alone would have been too much for many others, over that length of time.



1968 was a year of disasters. One of these was that I was injured in an accident. 5th February 1968 was the last day I worked on Jupiter until much later


Susan and I realised that the best chance for the aircraft was for someone to take over. She wrote to the RAeS Journal and Flight International and arranged for them to publish "... should anyone wish to save the project will he contact .. S.Hodgess Roper .".


Beverley Shenstone (ex-president RAeS) wrote on 1st January 1969 `... I am very sorry to hear of the difficulties and vicissitudes that you have had to bear... ... It appears to me that what you are doing to enable some other person or group to take over the project is the correct thing to do..' and `..write about your aircraft. Describe the technical design, with reasons for decisions made. Discuss the main problems which arose, both technical and organisational. Point out for the benefit of others, things to avoid and things of positive importance.'

  Am doing so.

Various people showed interest until they appreciated that a take-over would involve them taking it away. One group and one individual visited the garage in January, but declined the offer.


In June a fire destroyed part of the machine. From this time on, not being so well stored, the remains further deteriorated.


Flight Lieutenant John Potter MA RAF had contacted the Royal Aeronautical Society asking about HPF and learnt of the plight of Jupiter. A plane without a group. Well, actually the plane was in almost as bad a state as the group. He arranged to meet Sir Stuart and myself at Woodford, Essex to see the hardware. Number one, chronologically, in the actions for which he deserves special credit is having the imagination to see a heap of rubble and think `I am going to transform that into an aeroplane'. As I saw it then, my options were to allow this man to turn it into a static exhibit at best, or to let it carry on rotting; so I chose the former.

MY FEELINGS (with hindsight ) about the HANDOVER

Jupiter was to become the only HPA which performed better after being handed over to new leadership. Is this a point for me to be proud of ? Yes, insofar as John could generally follow drawings originally prepared only for myself.  Yes, insofar as it meant that as mentioned above, Jupiter became in some ways the first non-experimental HPA. No, since if the mistakes I made had been different ones, the original group could have seen the project through. I had built the fuselage big enough for my 6ft 2inch (1.88 m) self, but realised that others have more flying skill. While being sole leader of the project, my intention had been that when it came to flying, that at the moment of take-off the pilot would become the boss. Thus you are flying your aeroplane. It is one system, maybe not the best, but the decision on my part to adopt this policy had partially prepared me for relinquishing control.


On arrival at Halton John and I dumped all the components in the canoe-club shed. The task of convincing others that here there was a worthwhile project began. Sir Stuart Mallinson wrote to Air Commodore Weighill, the commanding officer at Halton. `When Flight Lieutenant John Potter came here, he took away what was left over from a fire of an aeroplane built by Hodgess Roper. ... worked in two of my garages building what he hoped ... Unfortunately, after 5 1/2 years he had an accident which prevented him for over a year doing anything, and after some 6 1/2 to 7 years a fire broke out and destroyed part of the machine. It is quite impossible for him in his condition to carry on or replace, and eventually he apparently arranged for it to be taken over to your Base. I think there is no question that Hodgess Roper had a good idea and there was a reasonable prospect that he might have been successful. .. I hope it may be possible for you to encourage the finishing of this machine.  ` Stuart Mallinson'


In much the same way as at Woodford,Essex, the plane was moved step by step into better premises. At one time it occupied the only room at Halton College which had access without going around twisting corridors. This was necessary because of the length of the wings. Other staff, Mrs Potter, and the more senior apprentices became interested, joined the Halton group and helped with the repair and later with the flying operations.


John's policy was that if anyone turned up, then he would find them something to do. I took a friend with me to Halton on one occasion and they were promptly given the task of making sanding blocks. In this way, if a person persisted they could then proceed to other tasks, if they didn't, then at least they had done something. As the group built up, he was able to delegate entire components, and 3/4 of the work of restoration was done in 20 weeks. (Potter 1973)


As far as I was concerned, from now on, Jupiter was nothing to do with me. But this situation did not last very long. John was working to the detail-working-drawings that I had prepared at Woodford, Essex for my own use, and they were such that he was able to do this. Well, there was an exception to this. On one drawing, I had written .028" x 1/4" which taken literally indicates a strip 0.7mm x 6 mm and John quite rightly didn`t believe that this was what I intended. So he phoned me. I replied that this meant a tube 1/4" diameter and .028 thickness; a stocked size. Being asked to resolve this ambiguity was all it took to re-awaken my interest in the project. I visited Halton from time to time. I made a few new drawings or new copies of old ones.


The original tailplane and elevator needed replacing, and I took the opportunity of a redesign here, in consultation with John. The new surface was all-moving, had a higher aspect-ratio and was positioned slightly further aft. This component was built at Woodford, Essex in 1971. The original control linkage was retained. Unfortunately this led to flying problems, a small movement at the control bar having too much effect. I had made outrigger wheels and fitted these just inboard of the ailerons. John decided to dispense with these and they were not used in flight. I feel that this was probably the right decision. The Puffin I outriggers had been removed after early flights. However on Toucan, outriggers at 40% of the semi-span had proved satisfactory. The Halton group finalised the detail design of the aileron control linkage, and made and fitted these parts Much of the trailing edge had warped because of damp storage. This would increase induced drag because the lift distribution would be affected. Looking at it another way, in flight each warp would create its own little additional trailing vortex. So, a lot of the trailing edge was cut away and replaced. The outer wing sections were found to be in good condition and were left with the original blue Melinex covering which Susan and I had put on at Woodford, Essex. The other three sections needed various repairs and were then covered in John's choice of aluminised Melinex.


When the plane was nearly assembled, I noticed that it was very easy to move the top of the fin from side to side because the rear-fuselage is easily twistable. This didn't seem right, but apparently didn't matter, being less critical than wing torsional stiffness. Ironically, it was partly because of the observed low torsional stiffness of the tail-boom that I had rejected it.


Halton is a grass airfield. When the aeroplane was in one piece, John tried some runs there, but was finding that the tail was staying on the grass and with only a small wheel, that end was being alarmingly shaken. Hence he moved the aeroplane twenty miles (32 Km) to RAF Benson. This meant that during all the flight trials, people from Halton had first to make this journey. During the first runs on the Benson concrete runways the tail still would not lift. Then John found that all that was needed was more speed to make the tail lift. This is due to the constraints of this type of layout with the concentric wheel and pedals, affecting the centre-of-gravity position relative to the mainwheel (see Puffin). On Jupiter, more weight is on the tailwheel than one wants for take-off.

 I arrived at Halton on February 10th 1972 with a list of a few jobs which I considered needed doing before the plane was airworthy, to be informed that Jupiter had flown the previous day, twice. Three more flights were made on the 13th. On the last of these the wheel buckled on landing. I had seen none of these flights, and it was not until after the 25th February that I was able to write :-


"Dear Geoffrey          28th February 1972

"A great shame you couldn't be there on Friday (25th), actually we only just managed to get a flight as by the time we had put the wheel back on and a new chain and got it outside it was nearing darkness. I believe I told you the wheel was damaged on the fifth landing, and the people at Halton had only just repaired it and took it to the aerodrome with me on Friday, When we had put the wheel back, a task which was accomplished not without my local knowledge of the particular machinery, it was discovered that the wheel-drive chain had also been damaged during the landing, but luckily we had a spare length and the special tools at Benson. So this was then trimmed to the exact number of links and fitted. (The old chain which had made five flights was cut up and a short length given to several of those who had helped with the project.) We then opened the hangar doors, having got clearance to use the runway, and seeing that the weather was calm enough and trundled the machine outside, the wingtips just clearing the sides of the doors of the hangar which could take a Concorde. Taxi to end of runway, and you wish you had taken a taxi because you get more puffed out running alongside than the pilot who can cycle the machine at ten miles an hour with very little effort. Surprisingly, since the aeroplane only has two wheels like a bicycle this can be done without the assistance of anyone at the wingtip to hold it level because aileron becomes effective at quite an early speed, but assistance is required to help turn sharp corners on the ground since the wheels don't swivel to steer. So, having got to the end of the runway you have to point the plane in the right direction. There were only three of us there - John Potter, Ernie Moore and myself on Friday, which is the minimum, one inside and two ground assistants for handling and to put the cockpit hood on which is quite a knack as it has to mate up in several places at once. Having fulfilled these tasks, I was going to act as timekeeper of the flight, and Ernie as photographer. Two youths leaning against the enclosing fence of the aerodrome thought fit at this stage to shout to us "You'll never fly". On our first attempt that day we actually didn't, this was because I hadn't grasped the fact mentioned above re wing tip holding. I as wing tip holder had held on far too long as I ran alongside whereas I should have let go when the aircraft reached walking pace. All my previous wing tip holding had been with gliders. Ernie claims that it took off and he could see daylight under the wheel while I was still holding the tip. He may well be right, it turns out that the pilot finds it not clear to tell whether he is still on or just off the ground, and on this occasion the feel was further complicated by me holding on. I was looking forward and forty feet from the wheel all the time, and it was beginning to get dark. We waited for John P to get his breath back before making another attempt. Meanwhile I was thinking that if what I had just witnessed was flying then it was a bit low. This time he reached flying speed much quicker and when he left the ground there was no doubt at all that he was going up. What impressed me most was the rate of climb, particularly as my calculations had shown and I had read in several places that this would be a most difficult manoeuvre. The aircraft then levelled out to a height well above our heads and giving us the illusion of hovering. Then John must have given an extra burst of energy because the machine once more started to climb and then went off into the distance. Then I realised that I hadn't pressed the stopwatch. It certainly was a sight worth seeing. The day's events had very much taken the form of going upto a bicycle, fixing the wheel and the chain and then just wheeling it out of the shed and pedalling it into the sky. I have up to now felt insulted when the machine has been described as a "flying bicycle" rather than as an aeroplane, but once airborne the size is apparently lost amongst the vastness of the sky, and what has happened is that he's pedalled and its flown. It is a Flying Bicycle. He landed and we ran to the aircraft, and he commented on some minor adjustments we had made to the instruments. I felt that watching the flight was a worthwhile recompense for having travelled to Halton, travelled from there to Benson, worked on the wheel and the chain and done quite a lot of running along the side of the runway. The true cost, of course, is all those, but multiplied by you-name-it and then put a nought on the end, or two noughts. And whether I feel it was worth this true cost I can't say. Thinking about it since, sometimes I feel I can't say yes and sometimes I feel that I definitely can't say no.'

 Geoffrey, to whom this letter was sent, came to Benson in June 1972 and observed the record-distance flight. As it happened he had the aggravation of a minor car-accident on the way. I asked him ( 1990 ) whether he felt it was worth it. `Yes, definitely', he replied.

(In 2002, Geoffrey himself became airborne under his own power pedalling the hovercraft, Steam Boat Willy. I remember that one too. An ex-marathon-runner, at the age of 62 he pedalled excessively on his first take-off and the craft shot away uncontrollably. But that`s another story. )

Two more flights were made on the 27th February, and three more on the 1st March. By the end of 19th March, twenty five flights had been made, the longest about a quarter of a mile.

Jupiter flying at the press conference at RAF Benson in 1972. RAeS collection


John Potter had made several flights before having the opportunity to observe one from the outside. It was Ernie Moore who gave him this opportunity, by making a few flights. Based on his observations, John was able to establish the best speed and attitude-in-pitch for Jupiter. Following this, flights were of longer duration as they were less exhausting.


It was found that aileron became effective at 5 knots, rudder at 8, but the tail did not lift until 13 knots. ( 1 knot = 1.15 mph = 1.69 ft/sec = 0.52 m/sec ) After this point, John recommends holding the acceleration steady. He later analysed the optimum pedalling effort during the ground-roll in order to be the least exhausted at the point of take-off (Potter 1975). However this analysis omits that the relevant quantity is anaerobic energy. Such an analysis will be vital for take-off from water.


It took some time to locate the source of an occasional loud banging noise that was occurring during flight. I discovered that on the ground this could be cured by holding my thumb against the moving chain as John pedalled, and we deduced that the propeller drive chain was sometimes jumping a tooth. Halton group members fitted a spring-loaded tensioner.


The Community Relations Officer at RAF Benson arranged a press-conference for a Sunday, always a good move, namely March 19th. This was to include a demonstration flight. As mentioned in the foregoing letter, I had been impressed by the flight-pattern of holding one height for a while, and then doing a further climb. I discussed this with John, who for most flights had been inside. We agreed to do this during the demonstration flight since with the capabilities of the aircraft as it then was, this was one of the most impressive series of manouevres that could be done. The first flight that day was disappointingly brief, as was the second. By the time the aeroplane was repositioned for another attempt, the wind had sprung up. Take-off into wind is considerably easier in Jupiter, thus conserving the pilot's energy. John was able to start the series of manoeuvres we had planned. As it happened, just as John started the second climb, the plane met a gust with the result that the climb was much more impressive than we had expected. The effect of the gust was to increase the effective airspeed, and the plane climbed like a kite, the mass of the aircraft being the "string". John levelled out, and for a while held a straight course. Then a second gust hit the plane, this time from the side. The effect of the gust and the wind-shear put the aircraft out of control Suddenly I noticed that Jupiter looked different, but it had a familiar appearance. Somewhere I had seen that view before. It took me a few milliseconds to remember that it was on my drawing-board that I had seen that view. It was a front elevation - spot on. Jupiter was heading straight for my bit of grass, it was out of control and losing height. Luckily I had thought out the appropriate response for just such an eventuality. I dropped to the ground. The rationale is that the wing will pass over you. It did. Seconds later I was on my feet and observing the heavy landing, wing-tip first. I was in line with the wing at this moment and observed it to be deflected into a curve I would not have thought possible, but nothing broke on the Balsa and spruce wing. A second later the fuselage came down with a thud and its height was reduced to a dimension that was surely not enough to house a living John Potter.  It was a worrying few seconds until Tony Gilchrist and I reached the cockpit and tore away at the fairing, to find John all in one piece. `Actually, that wasn't supposed to happen', said John for the benefit of the pressmen who were arriving. It had been Tony who had installed the aileron control linkage, and since it was failure of lateral control which had occurred, he promptly checked to see if it was the linkage that had been at fault. It was not so. Photographs show the controls at full deflection during the descent. The weather conditions had just been too much for it.

DAMAGE On inspection later it was found that damage was only to the wheel, the cockpit canopy and a dozen spruce to spruce glue joints on the top and bottom of the portion of the fuselage under the wing.

`IT'S DOWN, LET'S KICK IT' Journalists at Benson 1972, who would not have deigned to touch it when it stood majestically in one piece, swarmed forward to have a prod after Jupiter was seen to crash-land. There was already damage which turned out to take six weeks to repair. We didn't want any more. I was the only civilian in the group who was present at the time, and the only person who made any attempt to defend the aeroplane from this aggression. The Royal Air Force had been invaluable in enabling John Potter to restore and fly the machine, (Seven years later the RAF helped Gossamer Albatross), but my belief in the benefits of national armed forces in general had been declining for several years and took another downward turn when observing their inaction while our aeroplane was being attacked. This demonstration received greater media exposure than that of any other aircraft prototype except the Concorde, but as is usual, some of the descriptions were imaginative. One photograph showing Tony Gilchrist and myself running is captioned "..as running sightseers keep pace with it ..". Flt Lt A J Gilchrist was effectively the chief maintenance engineer, and as I remember, I had some sort of connection.

NAME During this much publicised flight the aircraft still did not have a name. The previous evening I had thought up two; both retained the tradition of the first vowel being "U". "Unicorn" because the pylon is like the single horn of this mythical beast, and because it was now flying from Benson, the home of the Queen's flight, and the Unicorn is one of her symbols. "Jupiter", after the planet, astronomy being one of my hobbies at the time. I had once managed to see this planet in the daytime without binoculars (we couldn't afford binoculars); it can be done if you know just where to look. This had reminded me of the discovery of the planet Uranus in 1781. Herschel first observed this through a telescope, then realised that it can be seen without such aid. Similarly, flight was first made only with the aid of engines (or winches), and now we were doing it without. I wasn't calling it "Uranus" and John didn't like "Unicorn" so that settled it.

REPAIRS On most trips to Benson, the Halton group would need to do some minor repair in addition to any flying, though not as extensive as after the landing of the 19th March. As a result the aircraft was gradually getting heavier.

MIST The inside of the cockpit used to mist up, and John double glazed a small area for forward vision, and cut some slits. It was necessary for the pilot to do some physical warming-up exercises before a flight. This would mean that the screen would become misted during taxiing. To obviate this John developed the technique of a "cold pilot" and a "hot pilot". The cold pilot who had not warmed up and was not perspiring would taxi the plane to the end of the runway.

INSTRUMENT To indicate attitude in pitch, John Potter added a mercury-switch controlling a red and a green light, powered by a hearing-aid battery. On test it was found that the best attitude was when the green light was blinking. The pilot could tell which light was shining without turning the head. This has been recognised by people outside the Jupiter project as a significant innovation. It certainly made a lot of difference to the actual performance of the aeroplane.

RECORD DISTANCE By May 1972, John had learnt exactly what speed to fly at for minmum power and how to take-off with minimum energy, and he had done a lot of cycle training. He had told me he was going to give up smoking. `But you don't smoke', I replied `Oh, I smoke about one a week', he said. It became clear to both of us that Jupiter was not capable of the figure-eight course. Arguably the power-requirements were too high for the climbs and distance alone. Having to do turns made it out of the question. What was worth attempting was a new distance record. The length of the Benson runway had been covered several times, and on the evening of June 29th 1972, John Potter was observed to fly 1171 yards (1070 m). The configuration in which it established the distance record was the 1963 design from my drawing-board with only the addition of the chain-tensioner and the instrumentation.

FIRST "COMMERCIAL" HPA We established another `First' by carrying payload on an HPA, namely printed envelopes stamped `Worlds First Man-Powered AirMail, Jupiter, 1972'. These philatelic covers were sold to collectors, and raised funds for the RAF Museum.


HPA`s have appeared at Air-Shows, for which they sometimes get fees. The current RAeS "Sporting Aircraft" Competition implies that the winner will go into production and sell copies of the winning craft to athletes for use in the sport. Some of the Japanese groups are partially funded by the prizes that they win. Most prizewinners have found that the cash won does not cover the costs. Now you`ve got this free on the web, I don`t even get paid for this book, but you are welcome.

CRANWELL In 1974 John transported Jupiter to Cranwell, where it hangared alongside the Dumbo/Mercury which he also acquired, but no great success was achieved with either of these planes at this airfield. In 1978 the Jupiter was retired to the Shuttleworth Collection and remained there until 1982 along with Toucan and SUMPAC.

THAMESMEAD FESTIVAL of HUMAN POWER 1984 This was a weekend meeting of HPVs of land, sea and air. The Jupiter was on static display and the only aircraft, since no current HPA was in Britain at this time. The purple Melinex on the outer wing-panels and ailerons was still drum-tight 19 years after Susan and I had glued it on (maybe only ten years after John had retensioned it). The propeller still spun. Festival-goers enjoyed sitting in it betwen HPV races.


Jupiter is now located at the Filching Manor Motor Museum, Polegate, near Eastbourne, Sussex, England. It may be viewed by appointment.

What I did right:- Design. Used the conventional answer whenever there was one; and if there was not, then thoroughly bench-tested the new idea before incorporation into the airframe. Organisational. After it became impossible to continue at Woodford,Essex, I handed over as soon as I could.

What I did wrong:- Design. The structural design of the wing to fuselage junction, though satisfactory, could have been neater and lighter. This is one of the ways in which the Stork aircraft was better than Jupiter. Organisational. There could have been contact with other HPA groups. During most of the time that Jupiter was at Woodford, Essex, we were located not far from SUMPAC (London) & Toucan (Herts). As it was, with no such contact, the sense of isolation was contributory to loss of morale. Links with other groups might also have helped solve the other organisational problems. Made plenty of other mistakes as mentioned above.

What John Potter did right:- Took the opportunity of taking over in the first place. Organised the best use of all the people and facilities that he had available, or could make available, to restore and fly the plane. This included, at the flying stage, intensive use of the "facilities" of the aeroplane itself and his own legs.

What John Potter did wrong:- During re-building, no components were weighed. There are a few details of the Jupiter which are badly constructed. Most noticeable is the wrinkled covering of the rear-fuselage. This could have been avoided by more consultation with me. In general the standard of construction of the Woodford-built parts is higher. With regards to flying, as he realised himself and wrote (to me) in 1973:- `I hope we shall be able to conduct our (further) trials in a rather more professional manner than we had time for last year (1972). It was all rather a rush, and I am surprised we achieved our results in a very short space of time '

CHIGWELL My next design never flew. It was based on what I misguidedly thought to be the best points of Jupiter and the best points of Puffin II. My February 1973 drawing shows a span of 80 ft (24.4 m), area 380 sq ft (35.3 m2), much of it constant chord for ease of construction. Ailerons moving up only and tip spoilers. Upright pilot. Twisted chain transmission to 10 ft (3 m) propeller mounted behind tip of fin. No rudder. It was designed to take off from grass.

All moving tailplane, also at tip of fin. Primary structure as Puffin II/LiverPuffin. Secondary structure Balsa and EPS. With its low wing position, tapering rear-fuse and "T" tail it looked like a jet transport, and had enormous fuselage wetted area. Optimisation was based on turning flight. Constructional test-pieces made.  Propeller built by Mike Knight of Essex Gliding Club. Ergonometer made.

METAL CHAINS CAN TWIST - OFFICIAL Lack of sufficient appropriate support ended the Chigwell project, but not before I had written to the Application Services Manager of Renold Ltd with regard to use of their chain 51308/01 (aluminium, fits bike sprockets). He replied `... we confirm that this chain will twist through 90 degrees over 54 inches (1.37 m) and although adequate for the loading figures given [cruise 75 lb(34 Kg), climb 144 lb (65 Kg), ultimate 352 lb (160 Kg)], we are concerned with the effect of the twist and reverse twist under load conditions and suggest that the system be tested before any flights take place. Also the chain should be visually checked at regular intervals to confirm that the security of the chain parts is still intact. [It can be arranged that there is no reverse twist, and if there is any, that it is on the slack side.] `Effective lubrication is most important. The lubricant must penetrate between the the pin and bush and pin and roller, and to achieve this we suggest dipping into a bath of good quality light machine oil prior to assembly, and re-lubricating regularly.'

1975 Frank Vann, John Potter and the author met in May 1975 to consider a new project, but collectively there was not enough enthusiasm at the time for this to proceed.