This is from the July 1978 Sport Aviation.
John Chotia and the Weedhopper at Chino '78
The Weedhopper
By John F. Chotia (EAA 125461)
President
Ultra Systems, Inc.
Box 2253 1965 S. 1100 W.
Ogden, UT 84404
The WEEDHOPPER is my 23rd ultra-light design. Over the last 12 years I
have built 18 hang gliders of both rigid wing and flex-wing
types; the other 5 were powered ultralights, some foot
launched and others wheel launched. All of these planes went
through several configuration changes, so all together over 50
aerodynamic concepts have been tried.
The goal has always been a low cost, fun, safe airplane.
The pure hang gliders were certainly fun but lacked
convenience and safety. I concluded that hang gliders are okay
for young, single types with the time to chase the weather,
but for me with 4 children and a wife, flying time is limited
so I didn't want to spend it traveling and waiting for the
wind. Foot launching lends itself to scrapes and bruises, too,
and I was getting tired of that.
I tried foot launched powered hang gliders but I was near
200 lbs. so I still needed a hill and wind. This led me to a
rolling launch and aircraft status. (It interesting to note
that I've found the FAA much easier to work with than some of
the very political hang gliding clubs which control flying
sites!)
This slow reinvention of the airplane has allowed me to
re-evaluate just how much structural complexity was necessary.
The Weedhopper is the final result. I could have made it
perhaps 15% lighter, but construction time would have been
easily 10 times as great and the plane would have not been
nearly as rugged. A 15% savings is only 24 lbs. anyway. I
found it very easy to add pieces to achieve a particular
function, but much more difficult to simplify while retaining
all the functions I consider necessary for safe, convenient,
fun flying.
The final design (Weedhopper) came down to the following:
- It must be powered to be independent of wind and hills.
- The wing structure must be rigid to retain stability,
controllability and safety in all attitudes (even inverted).
- There must be aerodynamic control of at least pitch and
yaw; dihedral has proven adequate when combined with rudder
for roll control when airborne.
- The plane must be capable of lifting a "mature male",
i.e., 220 lbs., at field elevations of at least 5000 ASL.
- Wheels are needed to allow less-than-athletes (soft old
men) to fly in safety.
- Ground handling must be easy and convenient; to me this
meant tricycle gear with a steerable nose wheel.
- Since there are no ailerons, the landing gear must be
very stable. The Weedhopper's main gear is 4' 4" wide and
the pilot sits only 6" off the runway.
- The structure must be simple, low-cost and rugged.
- It must be easily portable and only require one man to
set up.
- Oh, yes, It must be attractive! Everyone has an ego to
deal with!
Any smooth area is a runway for the Weedhopper
Earlier "short nose" version of the Weedhopper in flight
The Weedhopper meets these goals and then some. The tractor
engine choice allows the empty plane to balance at the proper
point to fly so the pilot's seat can be located directly on
the C.G. Weight and balance tests with various pilots show
about 1/2" max. contrast to most pusher-type ultra-lights
which are very sensitive to pilot weight changes. This feature
allows several people to fly the same plane without worrying
about stability or trim. The central pilot forward engine
arrangement is safer in the event of a crash since you don't
have a screamin' 5000 rpm engine out back waiting to punch
through the pilot's back and the pilot is protected at least a
little by the surrounding structure. The central pilot
position also lends a feeling of security because the pilot is
more In the plane than perched on it; he has better attitude
reference, too.
The wide, low landing gear handles crosswinds better than I
hoped for. Take-offs and landings have been made in up to 10
mph winds 900 to the runway. Just keep the nose wheel down
until take-off speed is reached and don't get caught halfway
between rolling and flying. Landings have been made at crab
angles approaching 45° (on grass) and the plane just plops
down and straightens itself out.
The Weedhopper has been flown in moderate turbulence and
handles it quite well, the only problem being low speed and
high drag. This allows sudden gusts to sap your momentum so
you need to use more power. Attitude control and
auto-stability are very good and the rudder is as effective as
ailerons in leveling the wings, if needed. Most often the
pilot must correct pitch to avoid ballooning in gusts. Flying
in gusty winds is not recommended, however, since at low
altitudes the space needed to correct could be greater than
the space available, especially during turns, but if the wind
comes up during a flight, the best method to get down is a
straight in, fast approach and fly it onto the runway. Also
with a 30 mph cruise you might be surprised at how little
headway you can make into a 25 mph wind; you could walk
faster.
Stalls in straight flight and shallow banks aren't unusual
except that only about 25-30 ft. is lost, power off and
slightly less power on. With the small high speed propeller,
torque isn't much of a factor. When stalled at moderate to
steep banks, the inside wing drops. I've never allowed it to
spin beyond V4 turn but the recovery is rapid and normal. The
altitude lost in such a wing-drop-recover maneuver is about 50
ft., sometimes less.
The Weedhopper has flown with adequate performance with a
220 lb. load at 4500 ft. ASL on its single surfaced wing and
direct drive 19 hp engine, but there are add on options, such
as a double surfaced sail and streamlined struts which are
recommended for pilots over 190 lbs. who plan to fly at
altitudes over 4000 ft. These will be especially important on
warmer days. I feel that a plane isn't fun to fly if the
performance becomes marginal even once in a while.
I feel that the Weedhopper really opens a new area of
recreational flying. It is low cost, yet still safe,
functional and not under-powered or difficult to fly. Ultra
Systems was incorporated early this year to promote and
produce the Weedhopper. I had personally carried the cost and
effort of development over the last 12 years with just the
help of my wife and a few friends. Now Ultra Systems, Inc. has
the capital and facility to do a proper job of marketing my
dream. For me it is a dream come true, one I hope many other
people can now share.
Further information is available from Ultra Systems, Inc.,P;
O. Box 2253, Ogden, UT 84404.
Er ... "cockpit" details
Yamaha engine details |
