Seagull Models L-4 Grasshopper 90 inches User manual

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Specications:
Wingspan--------------- 90.0 in (228.6 cm).
Wing area--------------- 1182.3 sq.ins (76.3 sq.dm).
Weight------------------- 13.2 lbs (6.0 kg).
Length------------------- 56.8 in (144.2 cm).
Engine/Motor size----- 20cc gasoline.
Radio--------------------- 4 channels with 5 servos.
ASSEMBLY MANUAL
Code : SEA 325

L-4 Grasshopper 90 inches Instruction Manual.
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ank you for choosing the L-4 Grasshopper 90 inches ARTF by SG MODELS . e
L-4 Grasshopper 90 inches was designed with the intermediate/advanced sport yer
in mind. It is a semi scale airplane which is easy to y and quick to assemble. e air-
frame is conventionally built using balsa, plywood to make it stronger than the aver-
age ARTF, yet the design allows the aeroplane to be kept light. You will nd that most
of the work has been done for you already. e motor mount has been tted and
the hinges are pre-installed. Flying the L-4 Grasshopper 90 inches is simply a joy.
is instruction manual is designed to help you build a great ying aeroplane. Please read
this manual throughly before starting assembly of your L-4 Grasshopper 90 inches Use
the parts listing below to indentify all parts.
Please be aware that this aeroplane is not a toy and if assembled or used incorrectly it is
capable of causing injury to people or property. WHEN YOU FLY THIS AEROPLANE
YOU ASSUME ALL RISK & REPONSIBILITY.
If you are inexperienced with basic R/C ight we strongly recommend you contact your
R/C supplier and join your local R/C model Flying Club. R/C Model Flying Clubs oer a
variety of training procedures designed to help the new pilot on his way to successful R/C
ight. ey will also be able to advise on any insurance and safety regulations that may ap-
ply.
INTRODUCTION
WARNING
KIT CONTENTS
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KIT CONTENTS
SEA325 L-4 Grasshopper 90 inches
1. Fuselage
2. Wing set (2)
3. Tail set (2)
4. Canopy
5. Cowling
6. Wing tube
7. Pilot
8. landing gear
9. Fuel tank
10. Tail wheel
ADDITIONAL ITEMS REQUIRED
TOOLS & SUPPLIES NEEDED
in cyanoacrylate glue.
Medium cyanoacrylate glue.
30 minute epoxy.
5 minute epoxy.
Hand or electric drill.
Assorted drill bits.
Modelling knife.
Straight edge ruler.
2mm ball driver.
Phillips head screwdriver.
220 grit sandpaper.
90° square or builder’s triangle.
Wire cutters.
Masking tape & T-pins.
read-lock.
Paper towels.
�20cc gasoline engine.
�Computer radio 4 channel with 5
servos.
�Glow plug to suit engine.
�Propeller to suit engine 20x8-20x10.
�Protective foam rubber for radio
system.
HINGING THE AILERON
Note : e control surfaces, including the ailer-
ons, elevators, and rudder, are prehinged with
hinges installed, but the hinges are not glued in
place. It is imperative that you properly adhere
the hinges in place per the steps that follow us-
ing a high-quality thin C/A glue.
Carefully remove the aileron from one of
the wing panels. Note the position of the
hinges.
Remove each hinge from the wing panel
and aileron and place a T-pin in the center
of each hinge. Slide each hinge into the wing
panel until the T-pin is snug against the wing
panel. is will help ensure an equal amount
of hinge is on either side of the hinge line
when the aileron is mounted to the aileron.
Slide the wing panel on the aileron until
there is only a slight gap. e hinge is now
centered on the wing panel and aileron. Re-
move the T-pins and snug the aileron against
the wing panel. A gap of 1/64” or less should
be maintained between the wing panel and
aileron.
T-pin
Hinge

L-4 Grasshopper 90 inches Instruction Manual.
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NOTE : e hinge is constructed of a spe-
cial material that allows the C/A to wick
or penetrate and distribute throughout
the hinge, securely bonding it to the wood
structure of the wing panel and aileron.
Deect the aileron and completely saturate
each hinge with thin C/A glue. e ailerons
front surface should lightly contact the wing
during this procedure. Ideally, when the
hinges are glued in place, a 1/64” gap or less
will be maintained throughout the lengh of
the aileron to the wing panel hinge line.
Turn the wing panel over and deect the
aileron in the opposite direction from the
opposite side. Apply thin C/A glue to each
hinge, making sure that the C/A penetrates
into both the aileron and wing panel.
Using C/A remover/debonder and a paper
towel, remove any excess C/A glue that may
have accumulated on the wing or in the
aileron hinge area.
Repeat this process with the other wing
panel, securely hinging the aileron in place.
Aer both ailerons are securely hinged,
rmly grasp the wing panel and aileron to
make sure the hinges are securely glued and
cannot be pulled out. Do this by carefully ap-
plying medium pressure, trying to separate
the aileron from the wing panel. Use caution
not to crush the wing structure.
Work the aileron up and down sev-
eral times to “work in” the hinges
and check for proper movement.
Note :
INSTALL THE AILERONS
CONTROL HORN
Hinge
CA glue

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4.
Fiberglass control horn
Fiberglass control horn
INSTALLING THE AILERON SERVOS
Epoxy
Epoxy
Because the size of servos dier, you
may need to adjust the size of the precut
opening in the mount. e notch in the
sides of the mount allow the servo lead to
pass through.
Minimum servo spec.
Torque : 80 oz-in (5.8 kg-cm) @ 4.8V;
100 oz-in (7.2 kg-cm) @ 6.0V
Place the servo between the mounting
blocks and space it from the hatch. Use a
pencil to mark the mounting hole loca-
tions on the blocks.

L-4 Grasshopper 90 inches Instruction Manual.
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Use drill bit in a pin vise to drill the
mouting holes in the blocks.
Use dental oss or heatshrunk tube to
secure the connection so they cannot be-
come unplugged.
Secure the servo to the aileron hatch
using Phillips screwdriver and the screws
provided with the servo.
Apply 1-2 drops of thin C/A to each
of the mounting tabs. Allow the C/A to
cure without using accelerator.
Apply 2-3 drops of thin C/A to each
of the mounting holes. Allow the C/A to
cure without using accelerator.
1.5mm
C/A glue
Remove the string from the wing at the
servo location and use the tape to attach it
to the servo extension lead. Pull the lead
through the wing and remove the string.
C/A glue

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Set the aileron hatch in place and use a
Phillips screw driver to install it with four
wood screws.
AILERON PUSHROD INSTALLATION
Please see below pictures.
Secure the servos with the screws pro-
vided with your radio system.
.
INSTALLING THE FUSELAGE SERVOS
.
Because the size of servos dier, you
may need to adjust the size of the precut
opening in the mount. e notch in the
sides of the mount allow the servo lead to
pass through.
Install the rubber grommets and brass
collets into all servos. Test t the servos
into the fuselage servo mounts.
105mm
3x10mm

L-4 Grasshopper 90 inches Instruction Manual.
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INSTALLING THE RECEIVER SWITCH
Install the switch into the precut hole in
the side, in the fuselage.
3/32” Hole.
.
Switch
INSTALLING THE ENGINE SWITCH
Trim and cut
Trim and cut
rottle servo arm
Rudder servo
rottle servo
Rudder servo arm
Elevator servo
Elevator servo arm

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INSTALLING LANDING GEAR
Locate items necessary to install Sprin
Landing Gear.
Switch
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2.
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5.
6.
7.
1\4 inch
6mm

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Epoxy

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Epoxy
Epoxy

L-4 Grasshopper 90 inches Instruction Manual.
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3x15mm
3x15mm

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3x15mm
3x15mm
3x12mm

L-4 Grasshopper 90 inches Instruction Manual.
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INSTALLING THE STOPPER
ASSEMBLY
Using a modeling knife, carefully cut
o the rear portion of one of the 3 nylon
tubes leaving 1/2” protruding from the
rear of the stopper. is will be the fuel
pick up tube.
1.
2.
3.
Using a modeling knife, cut one length
of silicon fuel line. Connect one end of
the line to the weighted fuel pick up and
the other end to the nylon pick up tube.
Carefully bend the second nylon tube up at
a 45º angle. is tube is the vent tube.
Test t the stopper assembly into the tank.
It may be necessary to remove some of the
ashing around the tank opening using a
modeling knife. If ashing is present, make
sure none falls into the tank.
Vent tube.
Fuel ll tube.
Fuel pick up tube.
4x5mm

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FUEL TANK INSTALLATION
When satised with the alignment of the
stopper assembly tighten the 3x20mm ma-
chine screw until the rubber stopper expands
and seals the tank opening. Do not overtight-
en the assembly as this could cause the tank
to split.
You should mark which tube is the vent
and which is the fuel pickup when you attach
fuel tubing to the tubes in the stopper. Once the
tank is installed inside the fuselage, it may be
dicult to determine which is which.
Use balsa block to hold in place the fuel
tank with C/A glue to secure the fuel tank.
Use balsa block to hold in place the fuel
tank with C/A glue to secure the fuel tank
inside the fuselage.
Connect the lines from the tank to the
engine and muer. e vent line will
connect to the muer and the line from
the clunk tothe carburetor.
Fuel pick up tube Fuel ll tube
Ven tube
With the stopper assembly in place, the
weighted pick-up should rest away from the
rear of the tank and move freely inside the
tank. e top of the vent tube should rest just
below the top of the tank. It should not touch
the top of the tank.
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5.
3.
6.
Ignition Module.

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Use four 4x30mm head bolts and four
4mm washers to attach the engine mount
rails to the ewall. Tighten the screws .
Make sure to use threadlock on the screws
to help prevent them from vibrating loose.
read locker glue.
MOUNTING THE ENGINE
Position the engine with the drive washer
(140mm) forward of the ewallas shown.
140mm
Use a pin drill and 4mm drill bit to drill
a small indentation in the mount for the
engine mounting screw.
4mm
Use a drill to drill the four holes in the
engine mount rails.
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2.
3.
ENGINE MOUNT INSTALLATION
Locate the items necessary to install the
engine mount included with your model.
4mm

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Machine screw M4x30mm
Reinstall the servo horn by sliding the
connector over the pushrod wire. Cent-
er the throttle stick and trim and install
the servo horn perpendiular to the servo
center line.
Move the throttle stick to the closed po-
sition and move the carburetor to closed.
Use a 2.5mm hex wrench to tighten the
screw that secures the throttle pushrod
wire. Make sure to use threadlock on the
screw so it does not vibrate loose.
COWLING
Please see below pictures.
4.
8.
9.
1.
5.
6.
7.

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11.15.
10.14.
12.16.
13.17.

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Use a drill and drill bit to drill the holes
for the cowl mounting screws. Make sure
the cowl position is correct before drill-
ing each hole.
Tape the cowl to the fuselage using low-
tack tape.
Epoxy