Lear Jet Manual
Contents
If you have not worked
with foam before, it is strongly recommended that you read the
How To section
first.
1.0 Assemble the wing.
2.0 Assemble the tail.
3.0 Assemble the Fuselage
and Ducted Fans.
4.0 Assemble the Nacelles.
5.0 Align and install the tail.
6.0 Finishing options
7.0 Center of gravity
and battery compartment.
Let's
get started
This is how it comes out of the
box. Not shown in this picture are the cutting beds for the parts
that are included. DO NOT DISCARD ANYTHING until the construction is
complete, as some of these beds will be used as jigs during the construction
phase.
Click picture to enlarge
When assembling the model, follow the order below.
You will also need:
- M77 spray glue
- Water spray bottle
- Masking tape
- Wax paper
- 150, 220 & 320 grit sandpaper, blocks, & sponge.
1.0
Assemble the wing
The Lear Jet uses a one piece
wing attached to the fuselage with 4 screws. The wing can be detached for
transportation.
1.1 Sheet the wing
Sand the top and bottom
of the wing cores lightly to remove any
rough spots on the foam surface. Wet one
surface of a 1/32" x 4" x 36" balsa sheet with water, and spray the opposite
side with M77 glue. Place the balsa sheet on a flat surface with the glue
side facing up. Spray the wing cores on the top and bottom with M77. Wait for the adhesive to get aggressively tacky.
Place the leading edge of the wing roughly along the mid line of the balsa
sheet. Carefully smooth
it over the top and then the bottom surface of the wing with the palm of
your hand. Do not apply
excessive pressure as this will bend and warp the wing. Use more
water if necessary to make the balsa more flexible and avoid splitting. If
it does split, do not worry, we will be filling in with wood filler later on. Continue with additional balsa
sheets to completely cover the top and bottom surfaces of the airfoil. Go
past the trailing edge about 1".
Click picture to enlarge
Trim
the excess balsa at the wing root, the wing tip, and the aileron cutout with good quality scissors, exacto
knife, or a blade. The fine trimming can be done with a sanding block.
DO NOT trim the excess at the trailing
edge at this time. Epoxy a 1/16" balsa strip to the hinge face of the aileron slot and 1/32" balsa
strips to the sides. Trim and sand flush.
 Click picture to enlarge
1.2 Join the wings
Locate the bottom beds of each wing half and set them on a flat
surface. Align the root ends and tape them in place with
masking tape. Place a strip if wax
paper at the center joint.
Use liberal amount of 30 minute epoxy to join the wings to each other, using
the bed as a contoured level surface. Dry fit before gluing. The wing cores have dihedral angle pre-cut on the bottom surface, so
join the wings such that the upper surface is level at the
maximum chord thickness. Place a straight edge on the top of the wing to keep it aligned while the
glue sets. Use weights to hold it flat & allow the
epoxy to set.
 Click picture to enlarge
1.3 Prepare and dry fit the ailerons
Sheet the top and bottom only of the ailerons with 1/32" balsa
going past the trailing edge about 1". Sand a 20 degree bevel on the
hinge face of the aileron. Sheet the
hinge side with 1/16" balsa. Use care so as not to bend or warp the aileron
while sheeting. Trim and sand as necessary, but do not trim
the trailing edge as yet. Place two scrap pieces of 1/16" balsa spacers at
each end of the aileron cutout and sand the ends of the aileron to get a
snug fit. Sheet the aileron ends with 1/32" balsa. Remove the spacers and
tape the aileron temporarily in place with masking tape. Test for free
movement.
 Click picture to enlarge
1.4 Make the servo boxes
We recommend using Hitec HS81 or equivalent servos for the ailerons.
Make two templates using file folder paper. One
template 1.5" x 10" and the other 1.75" x 1.75".
Place the long template along the hinge line of the aileron cutout and the
short one at one end as shown in the picture below.
Remove the long template and trace out the outline of the short template
with a pencil. Score and remove the balsa
with an Exacto knife. Use a Dremel tool fitted with a drum sander or router
to hollow out the servo box to a depth of approximately 3/4". Line the
bottom of the box with 1/16" balsa. Coat the visible side of the liner
with epoxy to provide a smooth surface for the servo tape to stick.
 Click picture to enlarge
1.5 Add the fixed main U/C mounts
If you purchased the retractable gear option, skip this section and
follow the instructions that came with retractable gear option.
Cut another cardboard template 8" x 4". Place it such that the long
edge is in line with the center of the wing joint. Locate a 1/4" x 3 x 2 plywood
mount and place it as shown in
the picture below. Remove the template and trace out the outline of the
plywood. Score and remove the balsa. Hollow out the foam to a depth of
1/4" with a Dremel tool. Dry fit the
mount to get a flush fit. Pour a liberal amount of epoxy into the
cutout and insert the mount. The U/C takes a lot of stress during landings,
so do not spare the epoxy.
Draw a line down the middle of each mount. Drill a 11/64" dia hole, 1/2"
from the root end of the line. Install the U/C with the straps provided. You
may delay this step until after the final finish has been applied. Use 3"
diameter wheels (not provided) if you fly off grass. Smaller diameter can be
used if taking off a hard surface. Wheel retaining collars are provided.
 Click picture to enlarge
1.6 Attach control horns
mounts
Tape the aileron in its neutral position. Position the servo in the
servo box as shown. Draw a line where the control rod should be and extend
it to the aileron. Position a 1/8" x 1" x 1" plywood control horn mount
provided, such that one side is lined up with the hinge and the piece is
roughly centered over the line. Trace out the location, score the balsa,
make a 1/8" deep cutout. Pour 6 minute epoxy in the cutout and insert the
mount.
 Click picture to enlarge
1.7 Assemble the wing mount box.
Locate the upper and lower bed sections of the wing foam beds that
will form the wing mounting box. Epoxy 1/16" balsa sheet to the tip
end of each section and trim. Position the upper bed pieces at the wing joint and glue them
with 6 minute epoxy. Sand the top flat.
Glue the 6" x 12" x 1/16" plywood piece with the cutout to the top the wing box.
Do not glue the lower bed pieces as yet.
 Click picture to enlarge
1.8 Trim the trailing edge
Place a straight edge against the rear face of the wing mount box and trim the excess balsa sheeting from tip to tip using a
sharp razor blade.
 Click picture to enlarge
1.9 Position the servos
and complete the wing mount box.
Make a 1/16"
channel
about 1/4" deep from the leading inside corner of the servo boxes to the
wing joint. Drill a 1/2" hole at the wing joint all the way through to the
top of the wing. Attach 12" extension cables to the servos and a Y Harness.
Position the servos in the servo boxes and route the cables as shown below.
Place a strip of masking tape over the mid 6" of the cable channel. Glue the
lower beds of the wing mount box in place. Sand flat and glue the 1/8" x 6"
x 12" solid plywood piece, in place. Sand the front & rear ends of the box
flat and glue the 1/16" x 2" x 6" plywood end pieces. Sand any rough
edges.
Click picture to enlarge
Locate the 1/8" x 5 7/8" x 12"
plywood piece with the cutout. Mark 4 hole centers as shown in the picture
below. Lay a sheet of wax paper on top of the wing mount box, and position
this plywood piece on top, align and hold in place with with some masking
tape. Drill four 9/64" holes all the way through to the bottom plywood
plate. Locate the four 2 3/4" screws, blind nuts and nylon washers. Insert
the screws from the bottom and install the 4 blind nuts. You will have to
enlarge the hole in the top plate for the blind nuts to fit flush. Cover
the blind nuts with masking tape to prevent glue from fouling the threads.
 Click
picture to enlarge
1.10 Add the winglets
The winglets are made by laminating two cross grained patterns cut
from 1/8" balsa for added strength. One pattern is made with the grain running
along the length and one along the width. You will have to add a small piece
to complete the pattern in one of the directions. Mark out the dimensions as
shown in the picture below on the 1/8" x 4" x 36" balsa sheet provided. Cut
out the winglet shape. Place one winglet on the 1/8" sheet such that the
wood grain is not running in the same direction. Mark & cut the winglet
shape again. Glue each
pair as a laminate to form each winglet.
Glue the winglet
to the tip of the wing by aligning the bottom to the wing profile. The tip is already cut to the correct
angle. Trim excess, shape and sand round the leading and knife edge the
trailing edge.
Click picture to enlarge
1.11 Fill and sand.
Seal
all joints and seams with epoxy glue. Fill any gaps with light weight
spackle or wood filler. Sand smooth when dry and vacuum.
 Click picture to enlarge
1.12
Attach the ailerons
This section should be attempted after the final finish has been
applied to the wing.
Attach the aileron control surfaces with transparent hinge tape on both
sides of the hinge. Alternatively, you can use strips of heat shrink
covering to obtain an invisible hinge line. Install the servo with servo
tape and center it. Connect the control rod between the servo control arm
and the aileron clevis with a z-bend at one end and a threaded insert/clevis
at the other. Make servo covers using the same template used for the
servo the boxes, attach with tape or heat shrink covering.
 Click picture to enlarge
Congratulations, the wing assembly is now
complete.
2.0 Assemble the tail.
The Lear Jet uses a stabilator which
combines the functions of the stabilizer and the elevators. It is not
necessary to have a rudder, although one can be added very easily.
2.1 Sheet the foam parts
Sand the top and bottom
of the three foam cores lightly to remove any
rough spots. Sheet with 1/32" balsa
sheet. Trim the excess balsa at the root, tip, and trailing edge.
2.2 Prepare the Fin
Mark and cut
a notch at the tip according to the drawing below. Dry fit the
bearing block to ensure a snug fit, and ensure that the block is square with
the fin. Do not glue the block in place at this time.
 Click picture to enlarge
2.3 Assemble the Stabilator
Glue a 1/16" balsa strip to the root rib of each stabilizer half, trim &
sand to shape. Glue a 1/4" thick balsa strip to each stabilizer tip, trim
and sand to make a wing tip. Install a 1/8" x 1" x 1" plywood control horn
mount on one of the stabilizers as shown in the picture below.
 Click picture to enlarge
Mark the root rib as shown in
the picture below.
Drill a 1/4" hole in
each stabilizer at the intersection of the two lines. Mark the tube drill
with masking tape to obtain a hole 3" deep. Use a block guide to ensure that
the hole is perpendicular to the root end of the stabilizer half.
 
 Click picture to enlarge
Dry fit the
stabilator as shown in the picture below. Insert the carbon tube provided
into one stablizer, slide the bearing block onto the carbon tube, and
insert the free end into the other stabilizer. Use the
foam beds as jigs to make sure the halves are level and that the root ribs
are parallel to each. Measure at the front and the rear of the root ribs and
make this equal. When satisfied, put about two or three drops of Gorrilla glue
in each hole and hold the stabs upright to allow the glue to flow into the
hole. Re-assemble the stabilator. As Gorilla glue sets it will expand and fill in the
hole but it may ooze out and foul the bearing. To prevent this, use
1/32" spacers and wax paper between the root rib and the bearing as
shown in the picture below. Tape or weigh down the stabilator assembly while
the glue sets. Allow at least 3 hours for the glue to set.
 Click picture to enlarge
2.4 Assemble the tail
With the stabilator still in its jig, dry fit the fin by sliding it over the bearing
block. Ensure it is square and perpendicular to the stabilator using triangulation.
If the distance x = x and y = y, then the fin is square in both the
horizontal and vertical. When satisfied, glue the fin to the bearing block using
6 minute
epoxy, being careful to not let the glue foul the bearing or the carbon
tube. Glue a 1/4" piece of balsa to the tip of the fin and sand to shape. Tape the stabilator in its
neutral position. Project a line 3 1/2" long, perpendicular to the
control horn. Mark the position of the servo box using the template used for
the wing servos, and
make a 3/4" deep
cutout. Line the bottom of the servo
box with 1/16" balsa. We recommend a Hitec HS81
or equivalent servo.
Drill a 1/2" hole from the root of the fin
to the servo box. Mount the servo using servo mounting tape, and route the cable through the hole to the root of
the fin.
 Click picture to enlarge
2.5 Optional rudder
Although not required, if you wish to add a rudder, it is very
simple. Mark out the outline of a rudder 2" x 5" from the trailing edge of
the fin, and carefully cut it out. Sand and bevel the hinge edge to about
20%. Complete the installation using the technique for the ailerons.
2.6 Fill and sand.
Seal
all joints and seams with epoxy glue. Fill any gaps with light weight
spackle or wood filler. Sand smooth and vacuum.
Congratulations, the tail assembly is now
complete.
3.0
Assemble the fuselage and ducted fans
3.1 Install the ducted fan mounts
Cut the mid section blank in half and use this as a cradle to hold the
fuselage.
Locate the 1/8" x 2 1/8" x 7"
and 1/8" x 2 1/8" x 11 1/8" plywood motor mounts and the foam mid-section of
the fuselage. Mark the mid-point of each motor mount, on one long edge. Mark
the mid-point of the cross section at the rear end of the fuselage
mid-section. Dry fit at each stage before gluing. Glue as
shown in the picture below with epoxy. Use balsa shims if necessary. The mid-point marks on the mounts
should line up with the center line of the fuselage, and the mounts should be
square with the sides of the fuselage. Clamp in place until set. Use a scrap
balsa piece between the clamp and the foam to avoid denting the foam.
 Click picture to enlarge
3.2 Attach the wing
Sheet the front and rear faces of the wing slot with 1/32" balsa.
Drop the wing assembly, complete with the wing retaining screws and blind
nuts, into the slot, making sure that it sits flat against the fuselage.
Make a mark at mid point of the nose tip. Square the wing to the fuselage by
making the "X" dimensions equal. Mark the position, remove the wing, apply a
liberal coat of 30 minute epoxy to the top, re-seat and re-check the
alignment. Use weights. Allow the glue to set. Unscrew the 4 wing
retaining screws and remove the wing and the wax paper. You should now have
a perfectly aligned wing. Use a Dremel tool to hollow out the foam under the
cutout in the wing mount plate to make a radio compartment about 1" deep.
Line the bottom with 1/16" balsa. Cover the top of the liner with a thin
layer of epoxy. The receiver can be attached to the liner with Velcro tape.
 Click picture to enlarge
3.3 Attach the tail cone
Using the same method, align and glue the tail cone in place. Square
the tail cone to the wing by making the "Y" dimensions equal as shown
in the picture. Use wax paper to keep the tail cone from becoming glued to
the rear end of the wing mount box. Make sure the top of the tail cone and
mid fuselage are in line
with each other by placing a straight edge as shown in the picture. Sand the
mating faces of the foam if necessary. Sheet the front and rear ends of the
nose cone with 1/16" balsa. Do not
worry if there are minor misalignments at the joint as these will get sanded out later.
 Click picture to enlarge
3.4 Attach the nose cone
Glue the nose cone, making sure it is correctly centered and
aligned. Tape the fuselage to the cradle
and the work surface,
trim and sand the nose cone to shape with 100 grit
paper and finish with 220 and 320 grit. Hold the sheet of sandpaper as shown
in the picture and pull it back all the way towards the nose tip or use a
see-saw action from side to side until the flat spot disappears. Clean the
sandpaper often with a wire brush. Sand the top, then the bottom, and then
the sides.
 Click picture to enlarge
3.5 Sheet the fuselage.
Lightly sand the whole fuselage to remove any uneven spots especially around
the glue joints. Vacuum to remove any dust from the fuselage and the work surface. Place masking tape on the motor mounts and wing seat. Spray the
whole fuselage and some 1/32" balsa sheets with M77 adhesive. Start at the
bottom front of the fuselage. Lay the sheet so it extends beyond the nose
tip about 1". At the point where the nose cone starts converging, slit the
balsa into strips roughly 1/4" in width and tack each strip to the nose
cone. As long as the balsa is attached to bare foam, do not worry if the
strips overlap each other, because we will be sanding all that out in a
minute. Use water spray to soften the balsa, and more M77 if necessary. Do
not get too close to the bare foam with the M77 because the propellant will
dissolve the foam. Continue all around the fuselage, the nose and the tail
cone, except the flat area which will be the tail mount, glue 1/8" balsa. Try not to trap any air bubbles under the balsa
sheeting. Make relief cuts
where necessary.
 Click picture to enlarge
Sand the nose cone with 100,
220, and 320 grit paper till all the overlaps are invisible. Sand the rest
of the fuselage to remove any overlaps or rough spots. Some of the balsa
strips around the nose may become unglued while sanding, re-glue with 6
minute epoxy and hold together with masking tape until set. Glue 3 layers of
1/4" scrap balsa to the flat end of the nose tip and sand to shape. Use wood
filler to fix any imperfections and sand smooth with 320 grit paper.
 Click picture to enlarge
3.6 Attach the nose wheel
If you purchased the retractable gear option, skip this section and
follow the instructions that came with retractable gear option.
Glue the 1/8" x 1" x 1 1/2" plywood piece
to the hardwood nose wheel insert. Place the wheel insert along the
mid-line of the fuselage, 15 3/8" forward from the front of the wing slot,
as shown in the picture below. Trace out the outline of the insert and make a
cutout so that 1/8" of the insert sticks out. Pour epoxy in the cutout
and glue the hardwood block into place. Drill a 5/32" hole 3/8" from the
front and 1/2" from the side of the nose wheel mount. Assemble the nose wheel as shown
in the picture below.
 Click picture to enlarge
Make a servo box for the HS81 steering servo 2.5"
back from the wheel. Line the bottom of the servo box with 1/16" balsa and
coat the visible surface with a thin layer of epoxy. Drill a 1/2" hole from the servo box to the radio compartment.
Install a HS81 servo using double sided servo tape and attach the control
linkage. Make a servo box cover from 1/32" balsa.
 Click picture to enlarge
3.7 Install Ducted Fans and ESCs
(hardware need for this section is not included)
Position the ESC as shown in the picture, and secure with a cable tie wrap. Mounting the ESCs
outside the fuselage ensures adequate ventilation and keeps them running cool.
Drill
a 1/4" from the ESC to the radio compartment for the power leads.
Place the ducted fan on the mounting brackets and square it with the
fuselage. Drill holes and use screws and nuts to attach it. Turn the
fuselage bottom side up and drill one hole 1/4" from the edge of the plywood
as shown, through to the ducted fan shroud. Secure with a screw and nut.
Repeat with the other ducted fan.
 Click picture to enlarge
3.8 Fill and sand
Seal
all joints and seams with epoxy glue. Fill any gaps with light weight
spackle or wood filler. Sand smooth when dry and vacuum.
Congratulations,
the fuselage assembly is now complete.
4.0 Assemble the Nacelles.
4.1 Assemble & sheet the Nacelles
Glue the main tube at the seam by aligning the inside of the tube. If
the outside is uneven, it will be sanded afterwards. Glue the seam of the
nozzle in the same manner. Sand the outside surfaces to remove any uneven
areas and rough spots.
Glue the main tube to the nozzle by aligning the inside edge as much as
possible. Sand the outside smooth especially around the joints and seams.
Sheet the main tube with 1/32" balsa and M77 adhesive using, allowing the
balsa sheet to extend past the nozzle's rear end, but do not
sheet the nozzle yet. At the point where the nozzle starts to converge in,
slit the balsa sheet into strips approx 1/4" to 1/2" wide. Tack down each
strip, allowing the strips to overlap, working in a circular manner around
the nozzle. Sand out all the overlaps with 100 grit paper and finish smooth
with 320 grit.
 Click picture to enlarge
4.2 Install the Nacelles
Position the nacelle behind the ducted fan shroud and align it with the
shroud. Temporarily hold it in place with masking tape. Mark the three
points where shown. Make two cutouts as shown below, to clear the mounting
lug and the plywood mounts. Slide the Nacelle over the shroud for a snug
fit. The nacelles are held with a decorative electrical tape around the
intake lip, after the finishing has been applied.
Click picture to enlarge
Congratulations,
the Nacelle assembly is now complete.
5.0 Align and install the tail
5.1 Prepare the tail
Attach the wing and place the model right side up. Position the tail
at the end of the fuselage tail section, and mark the location of the servo
cable exits the Fin. Drill a 1/2" hole from this point to the radio
compartment. Attach a suitable servo extension and fish it through to the
radio compartment.
5.2 Install the tail
Dry fit the tail
with masking tape and sand as necessary, while sighting from the front & rear of
the model to see if the center line of the fin is in line with the center
line of the fuselage, that the fin is vertically square with the wings, and
that the stabilator is level with the wings. Mark the location of the fin on
the fuselage. Glue with 30 minute epoxy. Tape in place and re-check the
alignment. Allow the glue to set, then using fresh glue, build an
epoxy fillet all around the base of the Fin.
 Click picture to enlarge
Congratulations,
the Tail installation is now complete.
6.0 Finishing options
 Click picture to enlarge
6.1
Options
Since the model is completely covered with balsa sheeting, you have several
options to personalize the final finish. The colors and design are limited
only by your imagination, creativity and building skills.
- Heat shrink covering - we recommend using low temp heat shrink
covering such as Polycover, Econokote, Superkote, etc.
- Paint over Balsa - make sure that the paint is foam friendly
or mask all exposed foam areas.
- Fiberglass and paint - use 0.75 oz fiber glass cloth and finish
with paint of your choice.
 Click picture to enlarge
6.2
Decal Placement
Apply the decals starting with the windshield and place them as
shown in the drawing. Click
here for the drawing.
If requested for a username and password, leave it blank and click on the
CANCEL button.
7.0 Center of
gravity and battery compartment.
7.1 Preparation
Before balancing the model, all components need to be installed,
except the battery. The location of the battery
compartment is not pre-determined because we will use the battery or
batteries to help balance the model. Once balanced, the battery compartment
location will be marked and a compartment and hatch will be built. The
Center of Gravity is 4 3/4" back from the leading edge of the wing mount box.
Tape a 1/4" dowel along the CG line on the underside of the wing box. Place
a wooden block or box under the wing such that the model sits as a see-saw
on the dowel. Place the battery pack/s on top of the fuselage and move it
back and forth until the model is balanced. Mark the position of the battery
compartment.
7.2 Build the battery compartment.
Cut out a hatch cover about 1/2" deep. Make a cutout in the
bare foam for the battery pack. Line the inside of the compartment with 1/16"
balsa. The battery/s can be held secure with Velcro tape. The hatch cover
can be hinged on one side with electrical tape and held in place with a
suitable latch or rare earth magnets. Make air intake and exit holes to cool
the battery. Drill a 1/4" hole from the battery compartment through to the
radio compartment for the power leads. Although the pictures below show the
battery compartment located on the top of the fuselage, you can choose to
locate it on the side or bottom.
 Click picture to enlarge
7.3 Wire the power plant
Connect the power set up for 3S or 6S as shown in the diagram below and bench
test.
 Click picture to enlarge
Congratulations the
model is now complete and ready for the test flight!!
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