This is part two of an article that began in the September 1974
American Aircraft Modeler. The
Supersweep was used to
break the long-standing Indoor Hand Launched Glider (IHLG) record
of one minute and thirty seconds. In 2009, Stan Buddenbohm set a
new record for 1:52.12 (see
video below). Website visitor Ward B. recently wrote
asking that I post the second article on the Supersweep, so, here
it is. Plans can be found in the
September 1974 edition.
Here's what to do with all those balsa parts with which you were
left hanging last month. Now you, too, can have a record-setting
hand launch glider (conclusion).
By Ron Wittman, as told to Bob Meuser
Ron chucks one toward the ceiling. The test describes
some hints for getting into the good physical shape that
competitive IHLG flying requires.
(From last month, we continue Ron Wittman's construction and
finishing techniques for his record-setting design. The full-size
plans appeared in the August issue. For those who missed Part 1,
the Supersweep broke the long-standing 1:30 barrier for IHLG, for
an AMA Open Record. Ron's son, Steve, set a Junior mark with the
same design. Last month, the text described the cutting, shaping
and final sanding of all the components. -php.)
Assembly: Before gluing any of the parts together,
make sure that they fit together perfectly. Any gaps must be filled
with glue, which will add weight and causes warping. Note that the
top of the fuselage is sloped downward and to the left in the region
where the wing goes - the dihedral joint is to be flush with the
left edge of the fuselage.
The bottom of the fuselage must be carefully shaped to conform
to the shape of the top surface of the stabilizer. Otherwise, the
bottom of the stabilizer will not be flat after the glue dries.
Check the fit as follows: Lay the stabilizer on a flat surface,
and position the fuselage over it. With the fuselage nose resting
on the flat surface, the fuselage should fit the stabilizer. At
the same time, check the wing mount to ensure that it is exactly
parallel to the flat surface.
Ron usually uses a white glue, although Ron's record-setting
"22" is assembled with a model airplane cement. Ron's advice: If
you prefer a white glue, use Titebond. If you prefer a model airplane
cement, use Ambroid. All parts should be "pre-glued" before assembly.
That is, each part is coated with glue and allowed to dry. When
the parts are to be joined, each part is again coated with a thin
layer of glue. After the glue becomes tacky, press the parts together.
There will usually be enough tack to the glue to hold the parts
together without pins or clamps. As most of the solvent will have
evaporated before the parts have been joined, a thin, strong, non-warping
joint will result.
After the final polish-sanding, saw the wing into four parts,
using a jigsaw or a fine-tooth razor saw. Cut carefully, especially
at the trailing edges. Sand a bevel into each edge for the correct
dihedral angle. Every builder has his own trick for doing this.
Hold the part down on a hard, flat surface with a true edge - the
plate glass sanding board again. With a sanding block, sand the
edge to be beveled flush with the edge of the work surface. The
hard edge of the work surface will ensure that the joint is straight.
A template taped to the work surface will aid in obtaining the correct
angle. Ron sands the bevel on the corresponding parts of both halves
of the wing at the same time, to ensure that they have the same
The Supersweep 22 was developed over a period of a year.
It has many subtle features that distinguish it as the champion
that it is.
At age 11, Steve Wittman is hardly big enough to heave
a glider of this size, yet he set a new Junior record with
the Supersweep 22.
Glue the four panels of the wing together. While the glue is
drying, prop the parts up to the proper dihedral angles. Some builders
prefer to make the outer dihedral joints first, while the inner
panels are held flat on the work surface. Then, after those joints
are dry, the center joint is glued.
Glue the fuselage to the stabilizer while the stabilizer is resting
on a flat surface. Then glue the rudder in place. As you sight along
the fuselage from the back, the trailing edge of the rudder should
appear slightly to the left - no more than 1/32".
After the tail joints are thoroughly dry, glue the wing to the
fuselage with the dihedral joint flush with the left edge of the
fuselage. Prop up both wing tips equally. Ensure that the wing is
slightly skewed (the right tip forward) by measuring the distances
from the outer dihedral joints (at the trailing edge) to the point
where the stabilizer intersects the fuselage. The distance on the
left side should be 1/16" less than that on the right.
Finally, sand the finger guard to fit snugly between the wing
and the fuselage, and glue it in place. When all of the joints have
dried, cut the finger notch into the trailing edge. The notch should
be about 3/8" deep, and should be formed to fit your finger snugly,
comfortably, and naturally. This is essential for good control during
The final assembly operation consists of applying a glue fillet
to the outside of all the joints. Apply a little glue to the joint,
then spread it with your finger. Several thin layers are better
than one thick one. Five-minute epoxy is convenient for the fillets.
Finishing: Some theorists claim that, at the
low Reynolds numbers at which models operate, the boundary layer
has such-and-such a thickness. Therefore, there is no use trying
to make the bumps and wiggles of the surface smaller than some fraction
of the boundary layer thickness - so, a mirror-like finish is a
waste of time. Perhaps. Ron's gliders do have a mirror-like finish.
Take your choice: either a plausible theoretical argument, or the
experience of a guy who regularly gets flights of more than 1:25.
It takes a long time to obtain a good finish, so relax and enjoy
If you have read many how-to-do-its, you'll know that every glider
expert has his own special recipes for the various brews and nostrums
used for finishing. Fasten your seat belts; here is Ron's magic
potion: plain, ordinary lacquer sanding sealer, straight out of
It is available at most large paint stores. Be sure to get lacquer-base
sanding sealer, not the oil-base type. Some sanding sealers are
called "water white" and have a creamy, often slightly yellowish
appearance. Some are clear. The water white is the stuff to get.
A small amount of plasticizer added to the sealer will prevent
the finish from being too brittle; but, if you overdo it, the surfaces
will be too limber. One drop of castor oil to an ounce of sealer
will probably be enough. Ron's gliders have many hairline cracks
in the finish, particularly where adjustments have been made.
If the sealer is too thin, let the excess thinner evaporate until
the sealer has a creamy consistency - the finish is supposed to
go on the wood, not into it. Ron applies two or three thick, flowing
coats of sealer. The first coats should be sanded with 400 paper,
and the final coat with 600. Use new sandpaper, and discard it when
it begins to clog.
For polishing, use (would you believe) a polishing compound,
not a rubbing compound, DuPont Polishing Compound, available at
auto supply and automotive paint stores, is a good one.
Support the surface to be polished on a flat surface, as it will
be necessary to apply a light pressure. Work on a small area at
a time - about half of a wing panel. Dab a few pea-size gobs of
compound on the surface and, with a soft cloth such as a piece of
a T-shirt, start rubbing lightly. A little pressure is required,
but go easy or the bare wood will become exposed.
After the compound starts to dry, the surface will start to shine.
If dull spots appear, you have probably rubbed the sealer right
down to the wood, so you'll have to start all over. When the polishing
is completed, remove any dried bits of polishing compound with a
damp rag. Apply a paste-type silicone auto wax, using a ball of
cotton cheesecloth, and wipe off the excess immediately with a soft
rag. Rub everything to a mirror finish with a clean cloth.
For decades, the practice has been to glue pieces of sandpaper
on the sides of the fuselage, forward of the wing, to ensure that
the model won't slip from the thrower's hand at the wrong time.
Instead, Ron cleans his fingers with lacquer thinner, then applies
violinists' bow rosin (available at music stores) or bowlers' wax
to his fingers.
Check the distance from the dihedral break to the stabilizer
center. The left wing measurement should be 1/16" less than
Finger-molded glue fillets add strength and streamlining
to all joints.
Apply Ron's patented Magic Potion (see text) with long,
Trimming and Flying: The moment of truth has
arrived: Will the bird fly? First comes the preflight check. See
that no warps have developed, and that everything is the way it
was planned - fuselage straight, wing panels and stabilizer flat,
rudder slightly to the left. Turn the model upside down, and balance
the fuselage on your fingers. The left wing (the one on the inside
of the turn) should drop. If it doesn't, add a bit of clay to the
left wing tip, and smooth it out.
Add washout to each outboard wing panel by bending the trailing
edge up and pushing it forward at the same time. If you just bend
it without pushing, the bottom surface will probably crack, and
you might end up with a piece of wing in your hand. Pushing forward
keeps the wood in compression while it is being bent, and tension
cracks can't develop. The extreme tips are washed out about 5°.
As you sight along the wing from the rear, the trailing edge will
be up nearly 1/8" at a point 1 1/2" from the tip (relative to the
wing at the tip-dihedral joint). That is a lot!
Bend down a 2" portion of the trailing edge of the left inboard
wing panel, near the dihedral break. The deflection here is about
Add clay to the nose, until the model balances at a point about
1/4" ahead of the CG position shown on the plans. Launch the model
at what you expect its gliding attitude and speed will be, and note
its reactions. If it tends to dive or stall, bend the trailing edge
of the stabilizer up or down, respectively. The model should show
a tendency to turn to the left.
If all is well, launch the model a little harder, slightly upward,
and with a slight left bank. The model should go smoothly into its
normal glide at an altitude of about eight feet. If it tends to
maintain an excessive left bank and flies too fast, add more "up"
to the trailing edge of the stabilizer. At this stage, it should
demonstrate its ability to recover from a slightly harder throw
with a steeper left bank without showing any tendency to spiral
in. Launch the model up at about a 60° angle above the horizontal,
with enough speed for it to recover at an altitude of around 50
feet. Watch its recovery.
From here on in, it is impossible to tell you exactly what to
do to correct every fault, but we can lay down some general rules.
The tightness of the glide turn should be controlled primarily by
the stabilizer warp (left trailing edge up, right down) or by a
slight amount of stab tilt (left tip high). The amount of wash-in
in the left inboard wing panel will affect the turn, too, but its
main use is to prevent the model from spinning in. Attempting to
tighten the turn by increasing the amount of left-rudder can lead
to instant disaster. Add weight to the left wing tip if necessary.
A tendency to roll too much one way or the other during the launch
and transition can be corrected by warping one side of the stabilizer
trailing edge up and the other down very slightly. Whatever you
do, do it gradually. After you have worked out the bugs with a moderate
chuck, start increasing the launching speed. As you do, you will
find it advisable to remove some nose clay. Then bend the trailing
edge of the stabilizer down to maintain sufficient speed in the
glide, and to prevent the model from "mushing."
Ron's model makes about 5/8ths of a complete circle to the right
during the climb, then makes a gradual transition into a rather
fast half-turn to the left, before settling down into its steady,
left-circling glide pattern.
If you can launch the model straight up with your full force,
by all means do so. But, if attempting to launch straight up causes
your throwing speed to decrease, launch at a more moderate angle.
Ron launches at about a 60° angle (that is about the angle at
which most fellows launch when they think they are throwing straight
You might try copying the launching techniques used by the local
hotshots, or someone you have seen at the NATS or some other contest.
Ultimately, you will have to develop a style that suits you best,
and trim your model accordingly.
The finger notch must be snug, but not tight, for proper launch
The glide circle should be as wide as the flying site permits.
The model should glide slightly nose-high, and slowly, But, it should
not be trimmed to fly at the slowest possible speed just short of
a stall. Better flight times will be obtained if the model flies
a little faster, Try adding or removing clay, and let the stopwatch
be the judge.
A polishing compound, then a final waxing, gives the model a
super shine (and it may just help the time).
Stan Buddenbohm in
Tustin Blimp Hangar - F1N (Indoor Hand Launched Glider).
New endurance record set for 1:52.12 (minutes:seconds)
Those Other Factors
A good glider is only one of the requirements for winning performance
- you also have to be able to throw it. This means that you should
be in pretty fair physical shape, but it doesn't mean that you have
to be an Olympic star (although it might help). There does not seem
to be a "typical" IHLG physique. Being tall or short, heavy or skinny
doesn't seem to make a lot of difference, What little difference
this makes is outweighed by the many other factors.
However, whatever your size and shape, you should get yourself
in the best possible physical condition if you are at all serious
about this IHLG business. This means general physical conditioning
(jogging, bicycling, tennis, swimming) and specific physical conditioning
- developing your throwing arm.
Ron threw a baseball for a half-hour every evening for months
before breaking the record. Throwing horizontally is not the same
as throwing vertically, so try to get in a little high-angle throwing,
too. If you have to do your practicing alone, try throwing a gob
of modeling clay against a wall or, better still, against the ceiling
of the garage - it won't bounce and roll like a ball will. All is
lost if you can't throw with good control, so try throwing for accuracy
Finally, chucking a glider requires concentration. Before chucking
the glider, stand still awhile. Run through all of the launching
operations in your mind: The approach run to the chosen launching
spot, the wind-up, exactly how you are going to swing your arm to
get the right elevation and bank angle, the particular spot on the
wall or ceiling toward which you are going to aim.
Those factors must be programmed into your brain cells before
you start the approach run, so that your body, in the final split
second of the launch, will follow its programmed routine automatically.
Getting that glider up should be the only thing on your mind.
Ron takes a long run (perhaps 25 yards) before launching. This
is not to get up speed, but for psychological reasons - it is part
of the automatic countdown he has trained his mind and body to go
through during the launching process.
A Word of Caution: Unless you have built several
IHLGs before, by methods similar to the ones recommended in this
article, we suggest that you don't start building the ultimate Supersweep
22 right off the bat. Rather, we suggest that you build a couple
of "learning machines," possibly from kits, to get the hang of each
operation involved in building and flying an IHLG. Those models
will be useful later for warming up your throwing arm.