visitor Bob wrote to ask that I scan and post the construction article
and plans for the F-84G Thunderjet control line model. The unique
feature of this model is that the power is supplied by the pilot.
A fishing pole and line is used to drag the airplane around the
flying circle and a separate, standard two-line elevator control
is used to maneuver the model. Construction is sheet balsa. Author
Joe Wagner (well-known in the modeling world) claims that with a
bit of practice just about any aerobatic maneuver can be accomplished
except for the overhead routines like the figure 8.
F-84G Thunderjet -
For the Tenderfoot
by Joe Wagner
Whip-powered with up-and-down control is quite a way to
try control line modeling. Sharp-looking model is also a
Motorless control line models are inexpensive, large enough to be
interesting, yet small enough to be convenient to build, carry and
fly. They don't make any noise, so they can be operated almost anywhere:
in the backyard, in a school playground, or in a vacant lot.
The pilot has more control over a whip-powered model than a
powered job, has complete command of speed, and can stop any time.
With the whip pole in the left hand and the control handle in the
right, control lines can be run in or out as much as five feet while
flying. This allows some stunts with the whip-powered plane that
are impossible for an ordinary model.
My six sons and I
fly constantly in our front yard. We have flown big models and small
ones, monoplanes and biplanes, trainers and stunt ships. The Thunderjet
is one of the best-flying and best-looking whip-powered models.
The Republic F-84G Thunderjet once was standard in 14 different
air forces. In the Korean war it flew over 140,000 combat missions.
The model can be made into either a highly-maneuverable but touchy
airplane that can do nearly anything in the book except the overhead
maneuvers - or a steady-as-a-rock ship that forgives some uncertainty
on the controls. Construction
out all parts before gluing anything together. The plans show the
required materials. One possible change is thickness of the wing.
It can be made out of either 1/8-in. or 3/16-in. balsa. With 1/8-in.
wood the airplane will fly faster; with 3/16-in. it will loop tighter.
The thicker wing is also more durable.
Trace the outlines
of the parts onto paper, then cut out these tracings to use for
patterns. Trace the insignia and markings that appear on each part.
These patterns are used later to locate details properly. Sand the
major pieces. Round off the outer edges of the fuselage, the wingtip
tanks, and the stabilizer. Glue the wing leading edge pieces on
the front of the wing, and the under-fin to the bottom of the rear
fuselage before sanding these parts. Assemble the elevators together
with their little popsicle-stick joiner and control horn. If inexperienced
with control line models, make the control horn twice the length
shown on the plan. This reduces the control sensitivity.
Another way of reducing sensitivity is to add weight to the
nose. A lump of modeling clay on the nose tames the ship considerably.
To do loops and figure eights, peel off the clay again. The more
nose-heavy a U-control model is, the less touchy and, of course,
the less maneuverable.
When sanding the wing, elevators,
vertical tail, and the two small fins for the wing-tip tanks, round
off their front edges and sand the rear portions to a tapered shape.
Don't make the back edges thin as a knife. Sand the wing to fit
as accurately as possible into its cutout in the fuselage. Cut the
wing in half on its centerline; glue it back together again with
the dihedral angle bend in the middle. (See front view on plan.)
Lay one half of the wing down flat on the workbench and raise the
other tip 1 1/8 in. off the surface. Sand the two edges to fit together
While waiting for the wing center joint to set,
cement the stabilizer onto the fuselage, making sure it is straight,
looking both from the top and the rear. Set the elevator assembly
loosely in place; next cement the vertical tail. A whip-powered
airplane doesn't pull heavily on the control lines, so the controls
must work freely. Hinge elevator when the model is practically finished,
using figure 8 stitches of nylon thread. Don't do it now.
Cut out all parts before building. The inexpensive 1/2A
Top Flite bellcrank and 1/2A Goldberg control horn can be
used instead of plywood parts shown.
It is the nifty doped-on tissue markings and decals which
make model look so real. Felt-tipped or ball-point pens
may also be used.
Install the bellcrank so that it moves freely. Be careful not to
get glue between the bellcrank and the wooden dowel it pivots on.
(Sketch shows how parts fit together.) The four little scrap-balsa
pieces are used to fill up the slots over the dowel ends. This part
of the model has to stand a lot of strain!
Put the wing
in place. Make sure it isn't crooked, either from the top or from
the front. Then cement the wing and fuselage joint all around on
both sides. After it has dried, put a double coat of glue along
joint. Add the wingtip tanks and their little fins.
nose weight may be entirely concealed; here's how. Hollow out the
front of the nose, then pack the hole with birdshot. Dump the birdshot
into a small paper cup, mix thoroughly with glue, then pack the
sticky mass back into the nose cavity. Or, glue a nickel or penny
to side at nose. After painting, put a turn or two of tape around
the nose over the coin.
Brush an even coat of clear dope
over the whole model, but don't gum up the bellcrank. The balsa
will feel fuzzy when dry, so sand off the fuzz with some very fine,
nearly worn-out sandpaper. Then brush on one more coat of clear
dope. Always dope both sides of balsa wings and tail parts at the
same time to reduce warping.
Cut-out colored tissue paper
is used for the USAF, the star-in-circle insignia, the red arrows
on the tip tanks, and the red warning line around the fuselage.
Since all these items are in pairs (except the line around the fuselage),
two pieces of the proper color of tissue are cut for each detail,
a little bigger all around than the finished insignia would be.
Tape these down, two at a time, on a smooth surface. Then tape an
accurate tracing of each insignia item down on top of its proper
color tissue. After that, it is an easy job to cut out the decorations
by slicing down right through both the patterns and tissue.
Attach the cut-out tissue insignia to the airplane with clear
dope. Position each tissue item in the right spot and hold it down
temporarily with one hand while lightly brushing thin clear dope
over the. cut-out. The dope penetrates right through the tissue
paper and glues it firmly in place.
bubble canopy, rudder, aileron, and flap outlines are all drawn
on the model lightly with a soft pencil. Ink over the pencil lines
with India ink or ballpoint pen. The red nose and the dark green
anti-glare areas are painted on the model with colored dope. Lastly,
the U. S. Air Force and 92026 on the vertical tail are decals. These
can be bought at the hobby shop.
With an ordinary needle
sew the elevators to the stabilizer. Add the music wire pushrod.
(It can be kept from falling off by wrapping a few turns of thread
around the wire where it sticks through the bellcrank and the control
horn. Keep the thread from coming off by coating it with clear dope
just before winding.) Flying
power, we used regular fishing rods. A seven-ft. fiberglass rod
was less than five dollars at a discount store. Even inexpensive
toy rods work fine. My son David got a five-ft. steel fishing rod
free from a neighbor. We made still another whip pole out of a six-ft.
length of bamboo, using the bottom parts of three big safety pins
for the line guides. (Fasten the guides to the pole by wrapping
them tightly with heavy thread, and then brush a couple of coats
of clear dope over the windings.)
The fishing rods don't
need reels, and it's not necessary to alter them. For stunt flying
it is helpful to keep the control lines from twisting together as
they pass through the rod guides. To do this, I added separators
on my own pole. The easiest and neatest way is to tie a piece of
nylon thread across the opening of each guide, dividing the round
hole into two equal D-shaped areas.
For the control handle
and the lines I use Carl Goldberg's little red plastic handle for
1/2-A models. It comes with a spool of Dacron cord for the lines.
At the pilot's end, I attach the lines to the two holes closest
to the middle of the Goldberg handle. Then the lines go through
the fishing rod guides, out toward the airplane. (Before the lines
are fastened to the model, decide how long they should be. The shorter
the lines, the more positive the control over the model will be,
especially in a wind. But this limits stunting and the pilot may
get dizzy from having to spin around pretty fast. Longer lines make
flying more interesting and challenging, but then a helper is needed
to hand-launch the model.)
About 15 or 16 feet of line between
the control handle and the fuselage of the airplane is a good length
to start with. That's short enough to launch and fly the model without
a helper, and yet not too short for doing stunts. At the airplane,
both control lines go through the one hole in the left wingtip tank.
Then the up line (the one from the hole in the control handle just
above center) is tied to the rear hole of the bellcrank. Thread
the cord through the bellcrank hole and tie a loop an inch or so
long with a square knot. Don't tie the knot right on the bellcrank
because it may snag in the fuselage slot when the model is flying.)
Also, put a drop of glue on the knot to secure it. Dacron cord is
stiff and springy, and even a tight square knot will work loose
eventually if it's not cemented.
The other control line
- the down line is tied to the front hole in the bellcrank. It's
a little tricky to tie the knot at just the right spot. Both control
lines must be exactly the same length and, when the control handle
is held straight up and down, the Thunderjet's elevators must be
flat and even with the stabilizer. This is really quite an important
detail, so it's best to be patient. When hand-launching the airplane,
don't toss it into the wind. A control line ship of any type should
always start off downwind, so that the wind won't blow it in toward
its pilot before it picks up full flying speed.
weight and an offset rudder don't seem to be necessary on whip-control
models. The control lines are swept forward from the bellcrank instead
of aft because, in flight, the tip of the whip pole points ahead
of the airplane. If the lines were swept back, as they are on an
engine-powered U-control model, the whip-control ship would yaw
outward far too much to fly or be controlled properly. As can be
seen from this little Thunderjet, whip-powered models aren't especially
F-84G Thunderjet Plans
The AMA Plans Service offers a full-size
version of many of the plans show here at a very reasonable cost. They will scale the plans any size for you. It is always
best to buy printed plans because my scanner versions often have distortions that can cause parts to fit poorly. Purchasing
plans also help to support the operation of the Academy of Model
Aeronautics - the #1 advocate for model aviation throughout the world. If the AMA no longer has this plan on file, I
will be glad to send you my higher resolution version.
Try my Scale Calculator for Model Airplane Plans.
Posted May 18, 2013