hagedoorn - inventing the hapa
TRANSCRIPT
Geophysical Prospecting, 2001, 49, 735±745
J.H. Hagedoorn ± inventing the Hapa: A review of a geophysicist's
`other' work and how it inspired others
Theodor Schmidt*TO Engineering, OrtbuÈhl 44, 3612 Steffisburg, Switzerland
Received July 2001, revision accepted July 2001
A B S T R A C T
This paper describes J.G. Hagedoorn's work on `ultimate sailing' ± the combination
of a manned kite and a water kite called a Hapa, constituting a minimal sailing
system ± and the way others have taken up his challenge to sail while suspended from
a kite. Hagedoorn's goal has not been entirely achieved, but `near' and partial
solutions have been reached. Kite-Hapa-sailing continues to pose a `Holy Grail' type
challenge to many kite-sailors.
I N T R O D U C T I O N : E A R LY H A PA S
Besides his professional geophysical work, Hagedoorn had
another scientific interest, which he pursued as an amateur.
It is a field so exceptional that he was able not only to
invent it and give it a name, but also to inspire dozens of
enthusiasts and become known to thousands of people
outside geophysics, and that with only two publications!
The title of his 40-page principal monograph, Ultimate
Sailing (Hagedoorn 1971), describes the subject. Hagedoorn
managed to reduce the concept of the sailing boat, which
usually consists of a hull, a keel or centreboard, a mast and a
sail, to a simpler system consisting of a kite in the air, a line
and a kind of water-kite for which he coined the name `Hapa'
(HAgedoorn-PAravane), liking its vaguely Polynesian sound.
The components of Hagedoorn's concept were already
known. Kites have been used to propel boats for many years,
beginning perhaps with the above-mentioned Polynesians and
later the great thinker Benjamin Franklin, then in earnest by
the Englishman George Pocock (1827/1851), who mainly
undertook long journeys in southern England by means of his
kite-powered carriage and who described man-lifting kites
for nautical use. More recently kites have been used by
members of the Amateur Yacht Research Society (AYRS) with
whom Hagedoorn corresponded. His Hapa or water-kite is
also not entirely original, similar devices having been used for
mine-sweeping, fishing and oceanographic work. Many
synonyms are in use, such as paravane and `chien-de-mer'
(sea dog). As early as 1845, a Dr Collodon operated a model
kite-Hapa on Lake Geneva (see Fig. 1). Burgess (1939/1995)
suggested sailing buoyant airships with paravanes. O.W.
Neumark flew buoyant kites from motorboats, but lacked
any sort of Hapa (Morwood 1961).
Hagedoorn was the first to suggest coupling such a device
to a manned kite, instantly forming a minimal sailing system,
but still a proper one capable of travelling upwind. Air-
inflated kites known as parafoils had just been invented and
were used by parachutists to glide through the air a distance
several times greater than the altitude from which they
jumped. Hagedoorn's concept was to equip such aviators
with his Hapas, which they could fling into the water while
still flying and, with sufficient wind, immediately begin to
sail in this new mode, becoming `aquaviators' capable of
unlimited travel without even getting wet, as long as the wind
lasted. The Hapa was thus not to be merely a sailing novelty
or thought experiment, but a device for rescue and possible
military use.
In the early 1970s, Professor Jerzy Wolfe and his students
at the Polish Aerodynamics Institute in Warsaw built and flew
a `paravane hang glider', apparently with many crashes, but I
do not know whether there was any connection between
Wolfe and Hagedoorn (Bradfield 1979).
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*E-mail: [email protected]
After having established the theoretical feasibility of the
Hapa, Hagedoorn undertook to make a scale prototype
himself. The first Hapa was a beautiful piece of work but it
simply did not work. The second model was disc-shaped to
avoid directional instability. With this prototype, drag tests
were carried out in a local canal (see Fig. 2). Hagedoorn
drove his car along the canal and the line was held by one of
his sons. At low speeds, the system was stable. Thanks to a
forward mounting, the Hapa was more or less at right angles
to the direction of propagation. At higher speeds, however,
the kite started to oscillate and the Hapa jumped out of the
water. An improvement was achieved by allowing the disc to
rotate freely, without creating a torque. The other end of the
system consisted of a parafoil. Hagedoorn went to the US for
its purchase, but it came without any instructions. A crash
landing on the heath caused him to perform his duties as
professor with a neck-band for several weeks. Another series
of tests was conducted, in which one of his sons was equipped
with a parafoil and pulled in the air behind a motorboat.
This once resulted in a spectacular splash from about 30 m
height ± but at least it was better to land in the water than
on dry land. The Hagedoorns faced the same problems as
the very first designers/flyers of aeroplanes. Not only had
they to build a plane, but they also had to learn to fly it. The
idea of launching the Hapa when the flyer is pulled up behind
a boat, thus achieving forward movement, was alas not
achieved as the instability problems persisted. A recent
picture of the last and best-performing prototype is shown
in Fig. 3.
Realizing that further progress and development could be
made only with more human resources, Hagedoorn put pen
to paper and produced the manuscript Ultimate Sailing in
1971. In the years thereafter Hagedoorn tried to arouse
interest amongst professional maritime journals and institu-
tions, without success. He then turned to Scientific American,
which published a synopsis of his manuscript in 1975.
Belatedly, in 1994, the full manuscript was published by the
Amateur Yacht Research Society.
This paper gives more details of the development of the
Hapa and describes some of the ways it has been
implemented and put to use.
D E V E L O P M E N T A N D I M P R O V E M E N T O F
T H E H A PA
Hagedoorn developed his idea of the sailing Hapa by first
examining a type of sailing craft known as the Pacific, or
flying, proa. This is a slim Micronesian outrigger craft which
is normally stabilized by the crew balancing the forces of the
wind by climbing on the outrigger `flying' just above or on
the water-surface. Members of the AYRS, notably Edmond
Bruce (Bruce and Morss 1965/1970/1976), realized that a
single hydrofoil attached to the outrigger could perfectly
balance all sailing forces ± in steady-state conditions.
Figure 1 Collodon's self-steering kite-Hapa,
1845.
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However, the sea is not `steady-state' and the craft remains a
highly capsizable object. Hagedoorn suggested using a curved
foil as shown in Fig. 4, but quickly went on to suggest that by
separating the structure of the sail and the hydrofoil, all
forces could pass through a single line, provided the hydrofoil
could be induced to keep its required attitude and angle by
itself, following the water-surface faithfully on its leash. He
was especially worried about the Hapa's pitch angle, i.e. its
rotation around the axis of the connecting line, and thus
suggested not only using a perfectly circular meniscus-shaped
hydrofoil, but also attaching this through a ball-bearing, so
that no pitching moment whatsoever could arise from the
foil. A float is still needed in order to ensure the proper depth
of the foil just below the surface, and a fin on the float is
required so that it will track in the proper direction. Figure 5
shows Hagedoorn's drawing of his Hapa and the way it might
be used to stabilize a sailing dinghy.
Hagedoorn's next step was to free the boat's working parts
± the airfoil (sail) and the hydrofoil (Hapa) ± completely, by
replacing the sail with a kite, doing away with the hull and
mast entirely and suspending the pilot from the kite. Figure 6
shows the final concept developed in Ultimate Sailing.
Hagedoorn provided a detailed theoretical basis and con-
jectured various ways in which the system might actually be
used in practice. Then, with the publication of the article in
Scientific American (Hagedoorn 1975), more people took up
the challenge.
I read this article while a student and immediately built a
Hapa to Hagedoorn's specification. I spent many hours
experimenting with it in the strong current of the Rhine at
Basel, trying to improve its efficiency, expressed by the angle
between its line and the normal to the direction of travel or
flow (the drag angle). For an `ideal' Hapa, this would be 08. A
circular foil is intrinsically inferior in this respect to more
slender, higher aspect ratio foils. Therefore I made wing- and
hoop-shaped Hapas and experimented with a depth sensor
designed to keep them just below the surface at all times. The
problem with these more efficient Hapas was that they would
suddenly become unstable if pulled too hard or fast, either
diving to the bottom or jumping in the air. Still, they worked
and achieved drag angles as low as 188. I attached kites to
these Hapas and sailed them across ponds, achieving
Hagedoorn's goal in a very small (unmanned) way. After
finishing my degree in physical oceanography in Wales, I
would have liked to develop kite-Hapas as autonomous
sailing oceanographic instruments, but was unable to get very
far with this. I had been corresponding sporadically with
Hagedoorn, but letters always took many months and, most
Figure 2 Hagedoorn's second Hapa in action in the Oegstgeester Kanaal, about 1972 (provided by the Hagedoorn family).
Inventing the Hapa 737
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unfortunately, everyone in the AYRS believed a rumour that
he had died ± many years before his actual death ± so it is
possible that he never knew about the very slowly ripening
fruits of his work in this field.
In 1980 I went to a symposium on wind propulsion of
commercial ships, where I met kite manufacturer Keith
Stewart, who immediately offered me a job ± designing
Hapas! Stewart was in contact with AYRS member Didier
Costes from Paris, who had built some very efficient Hapas
indeed (drag angle of about 108), wanting to use these to
stabilize and speed up his highly experimental triscaph
Exoplan. Costes' Hapas, like Hagedoorn's original, had to
be manually flipped in order to change direction, and since
Stewart was interested in selling autonomous sailing devices,
I was installed in Dorset designing remote-controlled Hapas!
Both these and the kites were radio controlled. This was not
required for steering, as the kite-Hapa combination is
automatically self-steering, but rather for changing the
course: all points of sailing up to `fine reach' (slightly
upwind) were available. Downwind was achieved by setting
the kite and the Hapa on opposite tacks. Figures 7 and 8
show some of these devices in use (Schmidt 1984, 1985/1995,
1991).
The usual type of Hapa-symmetry did not allow a kite-
Hapa to tack: unlike a sailing boat there was too little inertia
to carry it through the eye of the wind. I therefore went back
to the proa-type symmetry and constructed a bi-directional
Hapa which simply changed direction by shifting the point of
line attachment ± also by remote control ± and which also
had a `pure drag mode' for drifting slowly downwind with
the wing stalled. Successful as these experiments were, the
devices were too small to support a pilot; the most that could
be carried aloft was a camera.
Quite independently, William Roeseler (Roeseler and
Funston 1979) suggested sailing sailplanes on the sea using
Hapas, which he called `fish'. He later tried this in practice
and was able to fly devices from motorboats, but not actually
sail them.
F U RT H E R H A PA E X P E R I M E N T S
A keen follower of the Hapa concept was Roger Glencross, a
London accountant who wanted to achieve Hagedoorn's aim
in practice: that of sailing a manned kite-Hapa, with the pilot
supported in the air. In Ultimate Sailing, Hagedoorn had
shown this to be theoretically feasible, but much work
remained to make it work in practice, the major hindrance
being the issue of safety. The combination of heights, strong
forces, unstable components, tangled lines and water is a
formidable opponent. Glencross started building Hapas of all
shapes and sizes, testing them on a pond. Besides this, he
purchased a hang-glider and later several paragliding
canopies, now much more advanced and cheaper than the
first Jalbert parafoil that Hagedoorn used. I helped him fly
them in the wind in Portland Harbour, always only a short
distance above the ground, but enough to prove that with a
Figure 3 Hagedoorn's last Hapa working prototype (provided by the Hagedoorn family).
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steady wind of the right strength and a Hapa of the right
dimensions, it would be quite possible to sail airborne at
roughly right angles to the wind. One day we were nearly
successful: we had tried out one of Glencross's Hapas from a
motorboat and measured its forces and angles. The same day
we produced the same forces and angles suspended from the
paraglider in the wind. However, we never got the two
devices together under the required conditions. Every year
Glencross gets a little closer, but the combination of
conditions needed continues to elude him: a suitable wind
window (not too much and not too little), the right state of
the tide, a safety boat in readiness, the equipment in good
condition and enough competent helpers (Glencross 1993,
1996; Kitson 1994; Schmidt 1994/1996).
The main problem is getting started. I do not think
anybody has yet seriously contemplated Hagedoorn's ulti-
mate concept of launching the Hapa while free-flying in the
air, but even simpler methods, like starting from a motorboat,
require considerable resources and experience. The only
method useful in practice would be for the pilot to start
unaided in the water or at least from shore. This would
require entering the water with the Hapa ready to be released
from a backpack or some similar arrangement. This is not
very complicated, but nobody seems yet to have tried it. What
has been achieved is to travel sitting on a commercial
hydrofoil called an `air chair' while being propelled by a kite
instead of the usual ski-boat. Cory Roeseler (1997), the son of
W. Roeseler and the first expert kite water-skier, described
this in detail. In contrast to Hagedoorn's scheme, the
hydrofoil does not pull, but rather supports the pilot, but
Roeseler described brief uncontrolled excursions in `Hage-
doorn-mode', resulting in some back injuries, and has
understandably been reluctant to continue this line of
experimentation.
Great progress has also been made by kite-surfers who rush
around at great speeds in perfect control, sometimes also
leaping high into the air, momentarily becoming air-
supported. This has also been achieved on snow by Dieter
Strasilla, Andrea Kuhn and Wolf Beringer, who also
experimented with sailing airborne, with and without
`snow-Hapas' in the form of a second skier (Hanschke
1976; Beringer 1996). So, gradually, Hagedoorn's still elusive
goal is approached from all sides, and all that is really
required to achieve it is for somebody to combine a kite-
surfer's skills and boldness, the knowledge accumulated by
Hagedoorn and others, and Glencrossian perseverance.
H A PA S F O R S A I L I N G
With `ultimate sailing' in mind, Hagedoorn dwelt only briefly
Figure 4 The flying proa stabilized by a
curved hydrofoil (from Ultimate Sailing).
Inventing the Hapa 739
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on using Hapas for stabilizing actual sailing craft. Others
have investigated this use, in order to carry more sail and
achieve higher speeds without acrobatics or large outrigger
structures. In Fig. 9, I am shown in a folding canoe using
a Costes Hapa. Many years later, Robert Biegler (2001)
Hapa-sailed the same canoe extensively and methodically.
The main experimenter in Hapa stabilization is Paul Ashford
(1990, 1994), whose article `Seadogs for monohulls' is
published with Hagedoorn's reprint of Ultimate Sailing in
AYRS Publication No. 114 (1994). Ashford compared Hapas
(which he calls `doggers') with fixed hydrofoils and ballast.
He tested and measured numerous models, which achieved
drag angles as low as 108, and also full-sized Hapas intended
for his 7 m yacht. His work continues.
Costes (1994/1996, 1995) also continued to improve and
patent his `chiens-de-mer', intending to use them for sailing
with blimps or Zeppelins, as shown in Fig. 10. Some full-
scale work with the airship `Zeppy-2' actually commenced
(apparently at the cost of a broken leg), but this was too
rounded and had too little wing surface to sail upwind. A
design intended to correct this, his `planostat', was never
built.
Hapa design continues to fascinate, and one of the latest
models by John Perry is pictured in a paper by Quinton
(2001).
C O N C L U S I O N S A N D O U T L O O K
When I first read Ultimate Sailing 25 years ago, I was
convinced that I would be able to build and `aquaviate' with a
personal Hagedoornian kite-Hapa within a short time.
However, this has not been the case because sound engineer-
ing and physics, dedication and perseverance, encouragement
and money, skill and daring are all required, and so far all
experimenters have been lacking in at least one of these items.
What is the present state of the art and what is needed finally
to achieve Hagedoorn's goal or even more?
Figure 5 A sailing boat stabilized by a Hapa
(from Ultimate Sailing).
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q 2001 European Association of Geoscientists & Engineers, Geophysical Prospecting, 49, 735±745
The system
Hagedoorn's classic system uses a kite attached to the pilot by
short lines and a Hapa on a longer line. One of the main
reasons that this has not yet been implemented is the safety
concern: a high perceived risk for a moderate perceived gain.
Also, the system will not work in light winds and requires
considerable logistics at least to begin with. The extended
system I would like to see would allow the pilot to be
attached anywhere on the line between kite and Hapa and
would include a boat-like nacelle for winds when not
enough force is available to lift the pilot's weight. Long
lines allow the kite to be used at an elevated altitude with
more wind. Remote-controlled systems have already been
implemented; the extended system would mainly involve
scaling these up sufficiently to carry a person and equipment.
Adding propellers and electrical power systems to the
Hapa and perhaps also to the kite would facilitate launchings
and extend the possible range of operation. All this is
possible today since the components exist, but it requires
somebody to build them large enough and to put them
together.
The kite
Parafoils as used by Hagedoorn and Glencross have come a
long way. They can now be launched in very little wind and
are very efficient (high lift-to-drag ratio). However, once in
the water they cannot easily be launched again. Kite-surfers
have now developed waterproof and water-launchable kites,
but they use up to four lines and little attention has been
given to launching systems. Inflated and also buoyant kites
have proved excellent in moderate winds but difficult to
handle in strong winds. What is needed is the combination of
the best of the above systems. The ideal sports-kite must be
water-launchable, yet it must have a mechanism to reduce its
pull for handling and emergencies. The best kite for an
extended system would be shaped like an inflated wing with
electrical yaw and pitch control, and would thus take up any
Figure 6 Ultimate sailing: the aquaviator
sailing by parafoil and Hapa (from Ultimate
Sailing).
Inventing the Hapa 741
q 2001 European Association of Geoscientists & Engineers, Geophysical Prospecting, 49, 735±745
desired line tension and angle possible within the wind
window available, and this would be on a single line. A
control system would maintain the desired settings auto-
matically. Solar cells would power the system, perhaps also
with enough power left over for propulsion in light winds.
For this, the kite might be equipped with propellers or be
rotary in nature, allowing either high forces in `autogyro' or
electrically powered modes, or the harvesting of excess
energy in stronger winds (i.e. an airborne wind turbine).
For long trips, the kite would be buoyant and have an
integrated small solar-powered electrolyser for replenishing
hydrogen.
The Hapa
Present Hapas are either too small for starting the system or
too large for travelling quickly. What is needed is a multiple-
wing geometry or indeed several Hapas of different sizes
Figure 7 A Costes Hapa and Stewkie inflated kite on a fine reach (T. Schmidt).
742 Th. Schmidt
q 2001 European Association of Geoscientists & Engineers, Geophysical Prospecting, 49, 735±745
behind each other. A Hapa for the extended system would
have an electronic controller communicating with the kite in
order to maintain the desired line tension, direction and
course. It would be able to stay on the surface or operate at a
set depth. A control system would ensure that the Hapa does
not jump out of the water when pulled hard, as is sometimes
the case with present designs. This technology already exists
for hydrofoil boats. A certain amount of electrochemical
energy storage would allow operation in periods of adverse
conditions and facilitate launching procedures, for example
using additional propellers.
The line
This should be streamlined at least near the Hapa. For the
extended system it should be able to transmit electrical power
between the Hapa and the kite. A variation would be a
looped endless line or a torque-resistant component able to
transmit mechanical power.
The nacelle
This would be the pilot's crow's nest, suspended from the line
and able to move up and down along it. In low winds, the
nacelle would float and act as a boat. It would also have its
own adjustable hydrofoil for launching and low-speed
operation.
Future uses
Our third millennium aquaviator might not be Hagedoorn's
suggested military pilot but an oceanographic researcher. A
typical trip might go like this:
You cycle to the hangar where a number of kite-Hapas are
stored, pick the one with a nacelle for overnight trips and
manoeuvre the contraption to the dock on its dedicated
trolley, the kite being completely feathered for this operation.
The wind is onshore, so the Hapa must first pull kite and
nacelle outside ± using stored electrical energy ± like a
Figure 8 A radio-controlled Stewart/Schmidt hoop Hapa.
Inventing the Hapa 743
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veritable sea horse. You remain on the water-surface until you
have cleared the harbour. Freeing off a bit, the Hapa's main
foil begins to work and, speeding up, the line tension
increases sufficiently so that a touch of the joystick pulls
the nacelle free from the waves. Now the speed increases even
more, and rapid progress is made to deep water. You now
advance the nacelle towards the kite and make the Hapa dive,
collecting data and water samples. With the computer doing
all the work, you have time to take aerial videos of the
inquisitive dolphins nearby. As the light begins to fade, you
reduce the speed for safety and the Hapa is power-parked
with sufficient force to keep the nacelle suspended, so that
you may enjoy a restful night, gently swaying in the arms of
an airborne Morpheus.
A C K N O W L E D G E M E N T S
Hagedoorn's eldest son, A. Hagedoorn, was extremely
helpful in obtaining some of the material presented and in
checking parts of the Introduction. Gerhard Diephuis
provided much of the biographical information, procured
the pictures of Hagedoorn's Hapas, and was very helpful with
suggestions and corrections. Roger Glencross was instru-
mental in getting this paper written and was the driving force
in keeping Hagedoorn's goal of `ultimate sailing' in our
minds. Apart from those mentioned in the text and
references, many others have also helped with `ultimate
sailing' experiments ± to them also my thanks. Last but also
foremost, my thanks go to Professor J.G. Hagedoorn himself,
for sharing his ideas with us.
Figure 9 A Hapa-stabilized folding canoe (C. Finlayson).
Figure 10 An airship sailing with Hapa (from D. Costes' French
patent no. 443 378).
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R E F E R E N C E S
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N O T E
Copies of AYRS publications or photocopies of articles may
be obtained by writing to: Amateur Yacht Research Society,
BCM AYRS, London WC1N 3XX, UK.
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