he Gweduck (say “gooey duck”
really fast) is a much-bigger-than-average homebuilt,
twin-engine, six-place, 600-hp
amphibian that lit the imagination of all who saw it.
“The enthusiasm for the airplane,” Ben,
EAA 72406, the elder says, “was huge, but
only a small number of onlookers had serious
aspirations. However, those who had amphibian and bush flying backgrounds were very
serious because they recognized what we had
done: We had designed a corrosion-proof,
difficult-to-damage but easy-to-repair
amphibian that avoids all the bad flying characteristics amphibians have possessed almost
since the dawn of aviation.”
The Gweduck sprang from the imagination of the Ellison brothers and a friend, Ross
Mahon, EAA 215408. All three can boast of
enormously long and varied aviation pedigrees. Ben was the first pilot in the family,
soloing at 16 and eventually working for a
crop duster while getting his degree in engineering. Ben taught younger brother, Marty,
EAA 1008402, to fly, and he wound up doing
two tours in Southeast Asia flying A-6s before
working his way up to the left seat at a major
airline. You read about their friend Ross and
his restoration of the Wickham B in the
November issue (“Preserving the Past,
Homebuilt-Style”). His father, Brian Mahon,
was the Gweduck design team’s mentor.
When Ben and his wife started boating,
they bought a Cessna 180 on floats for transporting family and friends from their home
near Seattle to Roche Harbor in the San Juan
Islands, where the boat was moored. Eventually
SIDENOTE
About That Name… Grumman had taken all the
really cool bird names, so we named it after a
local deep-digging clam. —Ben Ellison
they traded the 180 for a de Havilland Beaver
on floats. After the Beaver, a Widgeon was
going to be Ben’s next airplane. At least it was
until he looked closely at buying one and realized it had a serious skeleton in its closet.
“Given enough time, saltwater would literally dissolve the airplane. That’s when I
started designing an amphibian of our
own,” says Ben.
Although he recognized the Widgeon’s
faults, he nonetheless used it as a comparative design guide of sorts, or maybe a design
non-guide, because he designed the Gweduck
around the Widgeon’s shortcomings and, one
by one, eliminated them. “We put together a
matrix of the flying characteristics, good and
bad, of the better-known amphibians, kept
the good characteristics, and worked to avoid
all the others.”
They started designing the airplane in
1990 and quickly realized they didn’t know
enough about amphibians. “But we were fortunate to know the people who not only knew
the questions but had the answers, many of
which could only come from years and years
of operating amphibians and floatplanes.”
Ben continues, “One of our greatest sources
of knowledge was Ross’ dad; he taught us the
realities of operating on the water. For instance,
he said you don’t design an amphibian that’s
going to be operated in the bush with a nose
gear because you won’t be able to beach it without it digging its nose into the sand. And the
tail has to be enormously strong because it’s
going to get bashed into tree branches and dock
pilings. The hull has to be almost entirely boat,
not airplane. You need to be able to walk on any
part of the airframe, and it has to be able to
bounce off docks, and smash into oncoming
waves and the occasional log, and suffer no
structural damage. Lastly, landing on the water
can be much, much harder on an airplane than
landing on a runway. Virtually every rough
water landing is a crash.”
With those lessons “in hand,” design work
began in earnest. But designing an amphibian
means designing a vehicle that must work in
two entirely different fluid mediums: one, the
air, is compressible and extremely well understood and documented, while the other,
water, is very incompressible and not well
documented at all. In effect, Ben was designing an airplane that sat on top of a boat. But
before doing that, he had to first set his goals,
then decide how to best meet those goals.
“Right up front we knew we wanted to
have an airplane with a 400-nautical-mile
range that could easily carry three 185-pound
men, three 160-pound females, and 300
pounds of cargo. This automatically says we’re
not talking about a small airplane, and there
were a lot of design parameters concerning
water operations that aren’t commonly
known.” Again, Brian came to their rescue. In
his aviation collection were lots of little-known National Advisory Committee on
Aeronautics and United States Navy reports
on amphibians. “He even had some from the
United Kingdom,” Ben adds.
“One of the first things we learned from
the reports is that building scale models for
testing works extremely well. In fact, much of
what was learned in the 1930s, ’40s, and ’50s
in this field was learned empirically from models, so we built a quarter scale, 11-foot model
with two chainsaw engines that had interchangeable ‘slippers’ on the bottom, allowing
us to easily change hull shapes. It was one of
the smartest things we did. Duplicating the
Widgeon’s hull, for instance, clearly showed us
the well-known Widgeon problem of porpoising and how the airplane had a very narrow
stable region between nose-up and nose-down
porpoising limits. You had to be in that range
or risk getting a very exciting roller coaster ride
when landing on water.
“We kept fine-tuning the model until we
had an extremely benign hull shape. And that’s
The wing center section showing the starboard
aileron bellcrank. The long white bearing sup-port is to carry the flap actuating through shaft.
The hull jigged up for the installation of the horizontal tail. The vacuum-formed cabin windows
were covered prior to painting.
The harmonic drive gear housing as well as clutch
and limit switch mounting brackets for one of the
main landing gear legs.
Checking visibility past the engine nacelles. The
hull is still jigged in position for the wing installation, which had just been completed.
