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.
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
1.1 Sheet the wing
The wing is made from 9 parts as shown in the picture below:
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".
 
 
 
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.
 
 
 
1.2 Join the wings
Glue the 1/16" plywood pieces to the underside of the mid-wing
section in the locations shown below. Locate the bottom beds of each wing half and set them on a flat
surface. 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.
 
 
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.
 
1.4 Make the servo boxes
We recommend using Hitec HS81 or equivalent servos for the ailerons.
Cut out the balsa sheeting on the underside of the wing to expose the servo
boxes. 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.
 
1.5
Add the fixed main U/C mounts
If you purchased the retractable gear option, skip this section and
click here.
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.
 
 
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.
 
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.
 
1.10 Add the winglets
Sheet the winglets with 1/32" balsa on both sides.
Glue the winglets
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
trailing edges. Paint the exposed foam with 30 minute epoxy to harden the
foam.
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.
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.
 
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.
 
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.
 
 
Mark the root rib as shown in
the picture below.
Drill a 1/2" 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.
 
Dry fit the
stabilator as shown in the picture below. Insert the 1/2" dowel provided
into one stablizer, slide the bearing block onto the dowel, 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.
 
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.
 
 
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 and wing mounts
Locate the 1/4" x 2 1/8" x 7"
and 1/4" 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.
Insert the 1/4" x 2 1/8" x5 1/18" plywood piece into the slot as shown below
and glue in place.
 
3.2 Attach the wing
Mark the center line of the wing at the trailing edge. Mark the
center line of the mid-fuselage cross-section at the rear end. Place the
wing in the wing cutout of the mid-fuselage section, aligning the center
marks. Drill a 1/8" hole vertical to the wing surface, centered on the
plywood piece that you had glued to the trailing edge of the wing
mid-section. Drill all the way through to the ducted fan mount below it.
Insert a 6/32" screw to act as a pivot point. Square the wing to the
fuselage by measuring from the center line of the front of the fuselage to
each wing tip.
When satisfied, hold wing in place and drill two more 1/8" screws in to the
front plywood piece along its center line about 1" in from each edge. Drill
all the way through to the 1/8" plywood that you had inserted and glued to
the fuselage.
Install 3 blind nuts as shown.
 
 
 
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 measuring the distance from the center
line of the tail cone tip to both wing tips as shown
in the pictures below. 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.
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.
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.
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.
 
3.6 Attach the nose wheel
If you purchased the retractable gear option, skip this section and
click here.
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.
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.
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.
 
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.
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. We will use the battery or
batteries to help balance the model. The Center of Gravity is 4.3" back
from the leading edge of the wing's mid-section. 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.
7.2 Wire the power plant
Connect the power set up for 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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