42 M ODEL AVIATION
GEO
Bill Werwage holds the final GEO-XL (L). Robby Hunt displays his downsized version—
the GEO-Star. Also shown is first GEO-XL, Bob Hunt’s Saturn. Bob Hunt photo.
As a 13-year-old spectator at the
Willow Grove PA Nationals (Nats) in
1961, I had my first chance to watch Bill
Werwage fly. He won the Senior Stunt
crown that year, flying his fabulous Ares.
Bill won his first Senior division crown in
Control Line (CL) Stunt two years earlier,
and had gone on to best the Junior and Open
division winners to capture the coveted
Walker Trophy—symbolic of the overall best
Stunt flier in the nation for that year.
It was the first of three times—so
far—that Bill’s name has been on that
trophy. His name was also featured twice
on an award that bears the name of the
late, great Jim Walker.
Bill captured the F2B (CL
Aerobatics) World Championships
(WC) Gold Medal twice in a row
(1970 and 1972) and the perpetual
trophy, the Walker Cup, that
comes with the title.
Bill is by far the most talented and
accomplished Stunt flier it has been my
pleasure to know and watch. The
fact that he is also a close friend
and fellow competitor makes the
presentation of one of his legendary
designs an especially great honor for me.
I have asked Bill to chronicle not
only his gorgeous GEO-XL design, but
n Bill Werwage
April 2001 43
Bill’s gorgeous GEO-XL performs a Wingover at the AMA National Championships in 1996. Photo by Dick Byron.
A true
thoroughbred
with World
Championships
-winning
heritage.
This design presents well in any attitude. The racerlike trim scheme adds flair. It’s a proven design! Byron photos.
Photos as noted Graphic Design by Carla Kunz
April 2001 45
GEO-XL’s wing was built using the Lost-Foam system. Here the rib locations are laid out on the core. This page: Hunt photos.
The half-ribs have been installed; Bill is detail-sanding them to
match the D-tube spar. It’s a very accurate system.
The balsa ribs have been generated from the foam templates,
and have been assembled in the lower foam cradle.
The base wing assembly weighs less than five ounces! With
controls, tips, and flaps, it should be 91⁄2-10 ounces.
Bill uses a hot wire-cutting bow to separate the rib sections from
the core. Note that he doesn’t cut through the cradle!
46 M ODEL AVIATION
Three out of four of the Junar series used the USA-1 wing
design. Bill won the 1989 FAI Team Trials with it. Hunt photo.
The GEO-Max featured a Warren Truss I-Beam wing and twin
rudders. It captured a place on the 1992 FAI team. Paul photo.
The GEO-XL’s lineage began with the USA-1. It won two Nationals
and two World Championships—a legend! Wynn Paul photo.
Bill’s USA-1P featured a piped OPS engine and radical styling. It
incorporated the USA-1 wing design. Hunt photo.
Type: CL Stunt
Wingspan: 62 inches
Engine: PA .51 with pipe
Flying weight: 53 ounces
Construction: Built-up balsa
Finish: Silkspan and dope
its lineage from roots in his legendary USA-1 series of
Stunters.
Bill is not one to talk much about himself or his
accomplishments; he’d rather let his flying do the talking. I have
asked Bill to make an exception in this case, and tell the technical
story of this design and the background stories of the many models
that led up to it, and their incredible competition record.
His fellow competitors call him “The Man.” The following
story may help explain why.
—Bob Hunt
The year 1961 brought the first serious change in competitive
philosophy in the CL Stunt event since the implementation of the
“modern” pattern in 1958. Up to that point, most successful
modern flapped Stunters were powered by .35-size engines and
were in the 525- to 575-square-inch wing area range.
Lew McFarland threw a serious monkey wrench into that
equation by winning two Nats in a row with his behemoth (at least
for the time) Stunter—the Shark 45.
Lew’s performances at Willow Grove in 1961 and Glenview in
1962 served notice to the CL Aerobatics community that there
GEO
was at least one more formula that would
work and win in Stunt. His big Squalo
(Shark) was powered by a K&B .45, and it
produced a considerable balsa overcast
with its approximately 680-square-incharea
wing.
I flew in the Senior division with my
original Ares design at both of those Nats.
The Ares had been very good to me,
netting three divisional wins (1959, 1961,
and 1962) and one Walker Trophy Fly-Off
victory (1959). The Ares was, and still is, a
great-flying .35-size Stunter.
However, I liked the presentation of
the larger model—especially on the
expansive ramps at the Nats. The
“normal” Stunters seemed small
compared to Lew’s Shark—on the ground
and, more importantly, in the air.
The Shark maneuvered with a
smoothness that seemed to mesmerize the
judges. In an event where impression is an
important intangible, that was a signal to
us all that this wasn’t the last large Stunter
we would see.
New power plants were emerging, and
for the first time I could imagine myself
flying a larger model competitively. The
venerable Fox .35 was the main reason
why the smaller aircraft were so
successful; it was the perfect amount and
type of power for Stunt. However, that
was about to change.
My first meaningful experiment with
larger Stunters began with what seemed to
be a scaled-up Ares; it was actually a
completely different set of “numbers”
stretched onto an aesthetic package that
had been successful for me. The Super
Ares was a new airplane.
The model featured long nose and tail
moments and a fairly high aspect ratio,
swept forward trailing edge, and I-Beam
wing. The wing thickness at the high point
was 23⁄8 inches—not thick by today’s
standards, but beefy for the time.
The Super Ares was developed when I
was serving as a combat engineer in the
Army. Because of that service, I had little
time to devote to development or
competition flying. Still, the model
proved to be good.
I took the Super Ares to the Nats in
California in 1963, with almost no
practice or trim time beforehand, and
placed a close second in my first Open
finals behind Bob Gialdini. He was flying
his rakish Sting Ray.
I had to skip the 1964 Nats because of
commitments to Uncle Sam. Jim Silhavy
captured that contest, flying a traditional
Fox .35-powered Nobler. Hot on his
heels were Mario Rondinelli with his
largish (roughly 600 square inches of
area) Venus (also powered by a Fox .35)
and Larry Scarinzi, who flew an original
Fox .59-powered jetlike design called the
Blue Angel.
The Blue Angel was designed, built,
and finished in less than two months for
that Nats, and it featured a 610-square-inch
wing. From all accounts, its larger size was
very impressive. It would have been
interesting to see what would have
happened had Larry been able to practice
with and trim on the Blue Angel for a few
months before competing with it.
Bob Gialdini brought his giant
Eclipse to Willow Grove in 1965, and
won the Nats with the 760-square-inch
design. Bob’s flying was excellent, as
usual, but the impression of the large
model certainly helped! I finished fourth
or fifth that year (it’s getting harder to
remember these things), again flying the
Super Ares.
Bigger models were starting to score!
The .35-size airplane wasn’t dead, but it
was in a mortal—and ultimately losing—
battle.
Smaller models won the remainder of
the 1960s Nats, but more and more big
aircraft were being flown, and were placing
consistently high in major meets.
In approximately 1967, I began to
realize that although the big airplanes were
impressive, they were not flying all that
much better than the smaller models. They
were better in good conditions, but they
suffered from a lack of power in wind.
The engines of the time were not
putting out enough additional power to
make the larger airframes perform well
in extreme conditions. We either had to
make the models smaller again or find a
48 M ODEL AVIATION
way to make them fly better with the
available power.
I was not ready to give up the
impression that the larger model offered,
and I began to look for ways to solve the
problem. I reasoned that a thinner wing
would be easier to “pull” through
maneuvers, and would not put too much of
a load on the engine. The thrust-over-drag
factor would become better all around.
I wanted smoothness, so I opted for a
fairly low aspect ratio, wide-chord wing.
Extremely tight cornering was not the
main goal at this time, but smoothness and
penetration were very important. This
would change in the future.
I didn’t want this to look like a “barn
door”-type wing, so I swept the wingtips
forward in a graceful curve. This gave the
wing a distinctive shape.
Construction was the proven I-Beam
type that had worked so well on the Ares
and the Super Ares. And this model was
big, with a 62-inch span and 760 square
inches of wing area! The airfoil thickness
was 17⁄8 inches at high point at the root!
I also incorporated a bit more leadingedge
sweep than normal, effectively
lengthening the nose moment.
Instead of the K&B .45, I tried the
SuperTigre .40. Jerry Worth had one in his
Electra design, and I watched him fly it at
a contest in Detroit. I was very impressed
by the engine’s smooth run and abundance
of usable and tunable power.
The SuperTigre .40 was very light, at
slightly more than eight ounces. By adding
a 3⁄4-inch-long aluminum shaft extension,
which set the engine back, the center of
gravity fell right on target. The result was
a very streamlined jetlike look at the nose.
The original USA-1 was the first
model with this new wing and engine
setup. This design was flown to a
disappointing fifth place at the 1969
Nats. I actually won the qualifying
rounds and the first Finals round.
I had to fly early in the last round, and
the scores got higher as the round wore on.
It was a beautiful balloon. However, the
other competitors seemed to like the
model, and I liked the way it handled the
wind. It never seemed short on power, and
it dealt with turbulence very well.
Jerry Worth had built a new design
called the Apterix, and it had some unique
aesthetics that I liked. After the 1969 Nats,
I changed my model’s rudder shape to one
similar to Jerry’s design and the USA-1’s
final shape was established.
The design was flown in this
configuration before the end of 1969,
making it legal for use in the Classic Stunt
event in its original form and its final form.
I flew the USA-1 in this basic
configuration in competition from 1970
off and on through 1984. It did pretty
well for me, capturing two WC Gold
Medals (1970 and 1972), two National
Championships titles (1971 and 1981),
April 2001 49
and several berths at US Team Trials
(1969, 1971, 1973, 1975, and 1981).
During those years I designed, built, and
flew a few other designs, including one of
my other all-time favorites—the Juno.
I also built a one-of-a-kind USA-1
with a thicker (21⁄4 inches at the high
point), higher aspect-ratio wing. It flew
well, but was not as good as the original
USA-1 design.
I used that model to place third at the
1980 WC and the 1980 Nats. Bob Hunt
borrowed the model to train the judges at
the 1981 Team Trials, and he said it was
the best-flying airplane he had flown. He
really would have liked the original model!
Those interim designs were successful,
but the original thin-winged USA-1
usually won in precontest flyoffs. That
wing is really special, and its story
doesn’t end with the USA-1.
In a weak moment in 1986, I tried a
Stunter powered by a SuperTigre .60. I
wasn’t sold on that engine, but it was
having its share of success on the
national Stunt scene.
The original USA-1 wing design was
pressed into service again. Even though
that wasn’t my most successful airplane,
the great windy and turbulent weather
characteristics inherent in that wing design
made it friendly to fly. I called it the
Hungarian Bull, in tribute to the Hungarian
WC in which it was flown that year.
The only change to the wing was in
construction. I made it a D-tube wing, in
place of the I-Beam that had been used in
the first two USA-1s. That made little or no
difference in how the wing performed in
the wind and turbulence.
That airplane was modified a year
later, to accept the OPS .40 and carbon
tuned-pipe setup that Dean Pappas and
Rich Tower had initially developed. The
model came to life with that power
system, and it was a very competitive
package. It was named the USA-1P (The
“P” standing for Pipe).
The aesthetics of that model were too
far from the norm for me, and it didn’t
score as well as I thought it should have.
The piped OPS .40 and USA-1 wing
combination was so compelling, I
designed a new, more classically styled
model around it for the 1989 season.
This was the first of the Junar series of
Stunters. (There were four, but one had a
somewhat smaller wing.)
The original Junar saw a great deal of
contest service, and racked up more than
2,000 flights! I used it at the 1989 Nats in
Pasco, Washington and finished a close
second to Jim Casale, but scored a win
with it at the Team Trials later that year. I
used the Junar for the next couple years,
flying it at the 1990 WC in France and the
Nats that year.
In 1991, I used an interesting variant
of the USA-1 wing in a model I called
the GEO-Max. The “GEO” came from
the angled, or “Warren Truss”-type
ribbing scheme, and the “Max” came
from the engine I used in that model—
the O.S. Max .46 VF.
By this time, I had taken over the
carbon-pipe producing business Bob Hunt
had started, and this model was a great test
bed for piped power system development.
It featured I-Beam wing construction and
sported twin rudders—a radical departure
for me in the looks department.
I tried a side-mounted engine and a
soft mount, in an effort to reduce noise. It
was, and still is, a great-flying model, but
it was prone to breaking the custom-built
headers that were necessary because of
the unique engine system. It placed well
for me at the 1991 Team Trials, earning a
berth on the 1992 team.
I used the Junar for the 1992 WC, and
along with that year’s Champion Paul
Walker and Bob Hunt, captured the first
team Gold for the US in 10 years. That
was the first Fédération Aéronautique
Internationale (FAI) team on which all
Stunt models were powered by piped
engines.
That WCs was held in Czechoslovakia
on an extremely turbulent field, and the
USA-1 wing in the Junar proved to be a
stable, predictable, smooth platform. And
the piped OPS .40’s extra horsepower
didn’t hurt.
I stripped the finish off of the GEOMax
design in the winter of 1992, and
rebuilt it with a tall single rudder/fin. I
refinished that model in a red, white, and
blue scheme with black checkerboards,
and renamed it the GEO-XL.
It continued to fly extremely well in
that configuration, but it had a more
classic look that I thought the judges
might find more acceptable—and they
did. The first GEO-XL flew to a close
second at the 1993 Nats, and I was sure
this was going to be another good one.
It almost was.
The header problem got very bad at the
Team Trials that year, and several broke
that week. When the header broke, the
engine went quite lean and competitive
flying was impossible.
I lucked out in competition flights for
the first part of the contest, but Mr. Murphy
(Murphy’s Law) showed up in the finals
and that meet was history.
I liked the model’s looks very much,
and the comments I received from other
fliers and some judges convinced me to try
another one with a more practical enginemounting
system.
I built the second version with a
Warren Truss D-tube wing and
incorporated the first radical change to
the original USA-1 airfoil shape since its
beginning in 1968. I blunted the nose of
the airfoil with a larger radius.
This GEO-XL was great from the start.
It flew through wind as well as all the
other USA-1 variants, but it was even
smoother! The biggest improvement this
change made was in cornering. The one
weak area of the low aspect ratio wing
design was finally overcome.
The addition of evermore horsepower
throughout the years had also contributed
to the performance of this wing, and I
finally felt that this design string had
reached its zenith. This was a
thoroughbred Stunt weapon of which I
could be very proud.
The GEO-XL presented here is a direct
descendant of the original USA-1, with
the same wingspan (62 inches), wing area
(760 square inches), and shape. The only
difference—and it’s a major one, which
brought the design up to modern
cornering standards—is the increased
leading-edge radius.
My choice for power was the amazingly
powerful and consistent Precision Aero
(PA) .51, fitted with a carbon-fiber tuned
pipe that Randy Smith and I codesigned.
The finished weight of the GEO-XL
was 53 ounces, which is a big part of why
it performs so well. This model has to be
built on the light side for you to really
experience its advantages.
CONSTRUCTION
Fuselage/tail assembly: There is nothing
too different from the norm in the
construction of these areas.
As with any model, these need to be
built as accurate and light as possible. The
plans are clear on the techniques involved.
Wing: Here lies the real difference in
building this design. Because of the
nature of the Warren Truss ribbing
arrangement, I used Bob Hunt’s Lost-
Foam Wing Building System.
This wing would be difficult to build
accurately in or on any other type of
fixture. And because of the unusual angles
involved in the Warren Truss
configuration, the precise rib shapes at each
rib station would be hard to plot.
The original GEO-XL’s wing (shown in
the construction pictures) featured a D-tube
wing with a 1⁄8 sheet spar. Subsequent
wings have been C-tube types with shear
webbing installed between the top and
bottom spars, from the center to out just
past the landing gear mount area.
The C tube has proven to be a much
easier wing to construct accurately, and
this is the type of wing construction
shown on the plans.
In the Lost-Foam system, accurate rib
shapes are obtained by laying out the entire
ribbing scheme on the upper surface of a
precision-cut foam core. The spar location
is also laid out on the core, on the top and
bottom surfaces.
This exact ribbing scheme and spar
position is laid out again in the lower
cradle halves, from which the cores are cut.
The cradles are just as accurate a negative
shape as the cores are a positive shape.
The corresponding rib positions on the
core and the cradle are labeled with a
ballpoint pen, then the core is accurately
cut vertically at the rib stations, yielding
perfect foam templates of the ribs. Because
the spar was laid out prior to this cutting,
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52 M ODEL AVIATION
its location is also accurate on each of the
foam rib templates.
These foam templates are used to trace
each rib onto 1⁄16 sheet balsa. The ribs are
cut just outside the traced line, then each
rib is realigned onto the foam template
from which it was traced and pinned
securely in place.
Use a sanding block to bring the edges
of the ribs down flush with the surface of
the foam template.
Bob uses two-pound-density foam for
these fixtures, and sanding the ribs against
them will not distort the airfoil shape of
the template. Dozens of wing-rib sets can
be made from one set of templates.
In a Warren Truss wing, cutting the
core vertically yields angled pieces of
foam. There is a rib template on either side
of the angled pieces, which allows you to
pin one rib to each side of the foam piece
and sand two ribs to shape at once! The
result is a perfect rib shape at each rib
station.
Once all the ribs are cut and sanded,
build the wing in the form-fitting lower
cradle halves. This process sounds
complicated, but it builds up very quickly
once all the parts are fabricated.
The original GEO-XL wing built in this
manner had a standard carved sheet-balsa
leading-edge cap. Through the years, I
have learned that a carved leading edge
can be a source of accuracy problems.
If the radius is not the same from the
apex of the curve to the surface of the
wing on both sides, the model can—and
usually will—be difficult to trim. This
problem can ruin an otherwise good
model.
For this reason, I have switched to
molded balsa leading edges. They are
extremely accurate and are repeatable from
model to model.
A detailed description of the Lost-Foam
building process and the leading-edge
molding technique would take more room
to describe than I have here. Soon Bob will
have a how-to article on the Lost-Foam
system in Model Aviation.
If you have your own foam-cutting
equipment, you should have little trouble
producing Lost-Foam cradle and template
sets and leading-edge mold bucks. The
foam templates for cutting Lost-Foam
wing fixtures are included on the plans.
If you don’t cut foam, Bob offers the
GEO-XL among the many wing designs
for which he produces the Lost-Foam
system. Contact him at (610) 746-0106 or
write to Robin’s View Productions, Box
68, Stockertown PA 18083. Complete
illustrated instructions are provided with
each Lost-Foam system for building the
wing and molding the leading edges.
The plans are complete, and should answer
any other building questions you have.
Control System: This is one of the most
critical parts of any Stunt model.
Throughout the years, I have
experimented with many types of
bellcranks and control horns.
The best control-system hardware I
have used is available from Winship
Models. Dan Winship produces a four-inch
carbon bellcrank that is hand-laid up from
carbon-tow material. It is bushed at both
ends and at the pivot point.
Dan also provides these bellcranks with
mil spec flexible leadout wire installed. He
runs the wire through annealed brass
tubing, which rides in the bushed bellcrank
ends. These are lightweight, strong,
accurate units.
Dan produces a complete line of flap
and elevator horns in a variety of sizes and
types. I use his slotted/adjustable elevator
horns in my models, to allow me to adjust
the ratio of elevator versus flap movement.
I like to dial out as much flap
movement as possible, and fly more off
the elevator. The result is less drag and
tighter corners. These horns allow this
fine-tuning quickly at the field.
You will know you have reduced the
flap movement too much when the model
shows a stall during hard cornering. You
need enough flap movement to provide
sufficient lift, and no more!
You must build a light model to really
get the benefit of this adjustment. If your
GEO-XL weighs less than 55 ounces, you
will definitely be able to dial out some flap
movement. If it weighs more than 56
ounces, you will probably have to stick
with the one-to-one ratio setup.
Dan’s elevator horn features a laser-cut
upright that has a dogleg, to allow the horn
to travel downward without the necessity to
notch the stabilizer’s trailing edge.
I highly recommend using Dan’s
horns and bellcranks in all competition
Stunt models.
You can order this great high-quality
hardware from Winship Models, 5971 Oak
Hill E. Dr., Plainfield IN 46168; Tel.: (317)
839-8316.
engine: The PA .51 in the original
GEO-XL is strong and reliable, and is
excellent for powering a model this size.
Also consider the PA .61, which has even
more power. The PA .61 was not around
when I was flying the GEO-XL in
competition. I’d have used one if it had been!
The PA line of engines, the carbonfiber
tuned pipe, and the Bolly carbonfiber
propellers on the original GEO-XL
are available from Aero Products, 1880
Scenic Hwy. N., Snellville GA 30078;
Tel.: (770) 979-2035.
The best propeller used on the original
GEO-XL was a 12 x 4 Bolly three-blade.
I used 70 feet of .014-inch-diameter
stress-relieved stainless-steel solid lines,
and Sig 10% nitromethane-content fuel
with two fluid ounces of Aero-1 additive
(available from Aero Products).
Finish: I recommend an all-Brodak
system. Brodak’s new dope finishes are
the best I have used in my 47 years of
Stunt flying. The only suggestion I have is
to add a bit more plasticizer. I use Dave
Brown Products’ Flex-All; it is compatible
with the Brodak dope.
I covered the model with 00 silkspan,
which is available from Brodak
Manufacturing.
This line of models built using this basic
wing design were easy to fly and trim. It’s
an airplane you can “pick up and fly.”
Build the GEO-XL light and straight,
power it well, and practice, practice,
practice! MA
Bill Werwage
111 Jacqueline Dr.
Berea OH 44017
