Multiplex PiCO CUB Building Instructions

22

Electric model aircraft

MULTIPLEX Modelltechnik GmbH

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# 21 4111

The beginner’s model with flair

Super flying qualities

Ideal for the beginner - flies great all by itself

Quick to assemble

Complete it in one afternoon

No finishing required

The model components are moulded in coloured plastic foam, and
come out of the mould as finished items

Can even be flown with only two channels

Fixed elevator

Flies in a very small space - even on a football pitch!

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PiCO CUB

PiCO CUB

Version 2 07/2001

GB

23

[1. Examine your kit carefully!
MULTIPLEX models are subject to constant quality checks throughout the production process, and we sincerely hope that you are
happy with the contents of your kit. However, we would ask you to check all the parts before you start construction, with reference to
the parts list, as we cannot exchange components which you have already worked on. If you find any part is not acceptable for any
reason, we will readily correct or exchange it once we have examined it. Just send the component to our Model Department. Please be
sure to include a brief description of the fault.
We are constantly working on improving our models, and for this reason we must reserve the right to change the kit contents in terms
of shape or dimensions of parts, technology, materials and fittings, without prior notification. Please understand that we cannot entertain
claims against us if the kit contents do not agree in every respect with the instructions and the illustrations.

Caution!
Radio-controlled models, and especially model aircraft, are by no means playthings in the normal sense of the word. Building
and operating them safely requires a certain level of technical competence and manual skill, together with discipline and a
responsible attitude at the flying field. Errors and carelessness in building and flying the model can result in serious personal
injury and damage to property. Since we, as manufacturers, have no control over the construction, maintenance and operation
of our products, we are obliged to take this opportunity to point out these hazards, and to emphasise your personal
responsibility. Please check that your private third-party insurance policy covers the flying of model aircraft of this type. If you
are not sure, expand your insurance cover, or ask for help from your national body. In the U.K. this is:

British Model Flying Association (BMFA),
Chacksfield House, St. Andrew’s Road, Leicester, LE2 8RE
Telephone: [phone]
E-Mail: [e-mail]

Adhesives:

MULTIPLEX 5-minute epoxy dispenser # 60 2740

and/or

White glue e.g. Bindan express (supplied in the kit)

Tools:

Scissors, combination pliers, balsa knife, screwdrivers (slot-head, cross-point), 3.5 Ø + 4.5 Ø drills,
small round file, 150-grit abrasive paper, sawblade (junior hacksaw).

Specification Wingspan 1160 mm

Fuselage length 785 mm
Wing area (FAI) approx. 28.3 dm²
Weight approx. 590 - 675 g
Wing loading approx. 20 g/dm²
Wing section Benedek mod., thickened
Tailplane section Flat plate
Controls Elevator, rudder and motor

Important note
For all joints involving the styrofoam components it is essential that you avoid the use of solvent-based adhesives, and instant
or cyano-acrylate glue (cyano, or CA) in particular. These materials will melt and destroy a large volume of foam, and the
component will be completely ruined.

Use solvent-free adhesives, such as 5-minute epoxy or white glue.

Using 5-minute epoxy

This adhesive should only be used at normal room temperature. The maximum working time (“pot life”) of the mixed resin is about 5
minutes, so you should only mix up the quantity required for the job in hand. Take great care to mix equal quantities of the two
components, and mix the epoxy quickly and thoroughly. Apply the glue to one side of the joint only, and don’t use excessive amounts.
Press the parts together immediately and tape or clamp the joint for at least 10 minutes. Freshly mixed epoxy can be wiped off the
model readily using methylated spirits on a rag. Do not use any other type of solvent, as the solvent itself may attack and destroy the
foam and ABS parts of your model. Be sure to read and observe the safety notes provided by the adhesive manufacturer.

Using white glue

White glue should be used at normal room temperature. The maximum working time of the glue is about 5 minutes. Apply a thin layer
of the glue to one side of the joint only. Press the parts together immediately and tape or clamp the joint for at least 15 - 30 minutes.
Excess glue can easily be wiped off using water. Don’t use solvent for this, as the foam and vacuum-moulded parts of the kit might be
damaged. White glue is only suitable for gluing wooden parts and styrofoam parts. Be sure to read and observe the safety notes
provided by the adhesive manufacturer.

PiCO CUB - Building instructions

24

Motor cowl

Propeller

Fuselage

Undercarriage set

L.H. wing panel

Seitenruder

Höhenruder

Fin

Tailplane
Fuselage turtle
deck

R.H. wing panel

Längsachse

Querachse

Hochachse

PiCO CUB

GB

Basic information relating to model aircraft

Any aircraft, whether full-size or model, can be controlled around the three primary axes: vertical (yaw), lateral (pitch) and longitudinal
(roll).
When you operate the elevator, the model’s attitude alters around the lateral axis. If you apply a rudder command, the model swings
around the vertical axis. If you move the aileron stick, the model rolls around its longitudinal axis. As our PICO-CUB has considerable
wing dihedral, ailerons are not required for roll control. In this case the rudder is used both to turn the model around the vertical axis,
and also to roll it (longitudinal axis). External influences such as air turbulence may cause the model to deviate from its intended flight
path, and when this happens the pilot must control the model in such a way that it returns to the required direction. The basic method
of controlling the model’s height (altitude) is to vary motor speed (motor, gearbox and propeller). The rotational speed of the motor is
usually altered by means of a speed controller. Applying up-elevator also causes the model to gain height, but at the same time it
loses speed, and this can only be continued until the model reaches its minimum airspeed and stalls. The maximum climb angle varies
according to the power available from the motor.

Longitudinal axis, lateral axis, vertical axis

Wing section

The wing features a cambered airfoil section over which the air
flows when the model is flying. In a given period of time the air
flowing over the top surface of the wing has to cover a greater
distance than the air flowing under it. This causes a reduction in
pressure on the top surface, which in turn creates a lifting force
which keeps the aircraft in the air. Fig. 1

Centre of Gravity (CG)

To achieve stable flying characteristics your model aircraft must
balance at a particular point, just like any other aircraft. It is
absolutely essential to check and set the correct CG position
before flying the model for the first time.
The CG position is stated as a distance which is measured aft from
the wing root leading edge, i.e. close to the fuselage. Support the
model at this point on two fingertips (or - better - use the MPX
CG gauge, # 69 3054); the model should now hang level. Fig. 2
If the model does not balance level, the installed components
(e.g. flight battery) can be re-positioned inside the fuselage. If this
is still not sufficient, attach the appropriate quantity of trim ballast
(lead or plasticene) to the fuselage nose or tail and secure it
carefully. If the model is tail-heavy, fix the ballast at the fuselage
nose; if the model is tail-heavy, attach the ballast at the tail end of
the fuselage.

The longitudinal dihedral is the difference in degrees between
the angle of incidence of the wing and of the tail. Provided that
you work carefully and attach the wing and tailplane to the
fuselage without gaps (using glue or screws), the longitudinal
dihedral will be correct automatically.

If you are sure that both these settings (CG and longitudinal
dihedral) are correct, you can be confident that there will be no
major problems when you test-fly the model. Fig. 3

Control surfaces, control surface travels

The model will only fly safely, reliably and accurately if the control
surfaces move freely and smoothly, follow the stick movements
in the correct “sense”, and move to the stated maximum travels.
The travels stated in these instructions have been established
during the test-flying programme, and we strongly recommend
that you keep to them initially. You can always adjust them to
meet your personal preferences later on.

Transmitter controls

The transmitter features two main sticks which the pilot moves
to control the servos in the model, which in turn operate the
control surfaces.
The functions are assigned according to Mode A, although other
stick modes are possible.

The transmitter controls the control surfaces as follows:
Rudder (left / right) Fig. 4a
Elevator (up / down) Fig. 4b
Throttle (motor off / on) Fig. 5
Unlike the other controls, the throttle stick must not return to the
neutral position automatically. Instead it features a ratchet so that
it stays wherever you put it. Please read the instructions supplied
with your radio control system for the method of setting up and
adjusting the transmitter and receiving system.

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Assembling the model:

Preparation:

Check all the styrofoam parts carefully, and clean up any rough
edges using 150-grit abrasive paper before starting construction.

Start with the tailplane 15: locate the hinge channel on the
underside, and mark it carefully on the top surface. Run a soft,
rounded-point pencil along the hinge line on the top surface. This
ensures that the foam bends exactly along the recessed line, rat­her than “giving” randomly around individual foam particles. For
safety’s sake apply a strip of adhesive tape (e.g. Tesa multifilm)
centrally along the top of the hinge line. Repeat the procedure
with the hinge line of the rudder 16.

Fig. 6

At the bottom of the rudder 16 and the tail end of the fuselage
cut a slot for the leaf hinge 27; it should be exactly in line with the
main rudder hinge line.

Fig. 7

Glue the elevator joiner 48 to the elevators using 5-minute epoxy.
Lay the elevators down flat and weight them until the glue has
set hard, to ensure that they are exactly parallel.

Fig. 8

Glue the tailplane and fin 15/16 to the fuselage 5. Hold the
fuselage turtle deck in place to help you position the fin correctly,
but don’t glue the turtle deck in place at this stage. Glue the hin­ge 27 to the fuselage and rudder as you do this. Check that the
rudder is aligned correctly, and deflects freely to both sides of
neutral. Before the glue sets hard, carefully align the fin and
tailplane relative to the wing (tailplane / fin angle: 90°).

Fig. 9

Completing the fuselage:

Using a small round file (a screwdriver also works well) cut the
tunnels through the fuselage from the motor to the battery box
on the underside of the fuselage, and from the battery box to the
RC compartment.

Fig. 10

The undercarriage reinforcements 44 fit in slots on both sides of
the battery compartment on the underside of the fuselage. Before
installing the reinforcements, use a fine-tooth hacksaw blade to
cut slots 3 mm deep and 1.5 mm wide in them at the marked
points; the undercarriage units fit in these slots later. Drill two 3.5
mm Ø holes in both reinforcements at the marked points. Hold
the undercarriage reinforcements against the outside of the
fuselage, and drill 3.5 mm holes half-way through the styrofoam
from each side, using the reinforcements as a template. The
reinforcements can now be glued in the fuselage using 5-minute
epoxy. Cut two pieces of 3/2 mm Ø plastic tube 64 80 mm long,
and push them through the fuselage at front and rear to form
undercarriage attachment dowels. Set the tubes central while the
epoxy is still soft. Cut slots across the underside of the fuselage
for the undercarriage legs, using the 3 x 1.5 mm slots in the
reinforcements as a guide.

Fig. 11

Installing the RC system components in the fuselage:

The rudder and elevator control systems are based on the “snakes”
60/61, which run through holes cut in the tail end of the fuselage.

In order to position these holes accurately it is necessary to install
the servos in the fuselage. Screw the two servos to the mounting
rails 47 and check that this assembly fits in the fuselage. Shorten
the rails if necessary. Finally glue the servo rails 47 to the fuselage
sides, with the servos still attached.

Fig. 12a

If your model is # 21 4048, the kit does not include the RC system
components. In this case you can decide for yourself whether to
install individual servos or an “Einstein” or “The Brick” module (=
MULTIPLEX module containing receiver, two servos and switch).

Fig. 12b

Using side-cutters, a short pair of scissors or a saw blade, cut off
the lower part of the T-piece of the horns 20 leaving just a short
stub. Fit a pushrod connector 32 in the outermost hole of the
elevator and rudder horns 20. Slip the M2 washers 33 over the
threaded shank, then fit and tighten the nuts 34. Fit the socket­cap screws 35 in the threaded hole in the pushrod connectors,
and tighten them using the allen key 76. Now glue the horns in
the recesses moulded into the control surfaces, with the row of
holes facing forward in each case.

Fig. 13

The holes for the snake outers 60/61 must be positioned to give
the wire pushrods 62/63 as straight a run as possible from the
servos to the control surfaces. The linkages must run smoothly
and easily.
Pierce the tunnels at the tail end of the fuselage using a small
round file or a screwdriver, and temporarily fit the snakes. Note
the position of the rudder and elevator horns 20 when you do
this. The snake outers should exit the fuselage side about 85 mm
forward of the tail end of the fuselage. Slip the pushrods (0.8 mm
Ø steel wire) into the outers and check that they run smoothly.
When you are satisfied, glue the snake outers to the fuselage using
5-minute epoxy.

Fig. 14

Form a Z-bend in one end of each of the steel pushrods, and
connect them to the fourth hole of the servo output arm (approx.
10 mm from the pivot axis).
If you are using an “Einstein” or “The Brick” module, bend the final
5 mm of the pushrods 62/63 at 90° at the servo end, and connect
them to the servo output arms (second hole from the centre ­approx. 10 mm lever length), fitting the plastic spacers 29 (0.8 to

1.6 mm) at the same time. Secure them with a drop of 5-minute
epoxy.

Fig. 12b

Check that the fuselage turtle deck 6 is a snug fit, trim it if
necessary, and glue it to the fuselage using 5-minute epoxy. While
you have a little spare epoxy mixed up, glue the tailskid 45 into
the tail end of the fuselage.

Fig. 15

The wing is attached to the fuselage by plastic screws which
engage in the wing plates 41 + 42; press the captive nuts 21 into
these and glue them with 5-minute epoxy. At the same time glue
the wing plates in the recesses in the fuselage. Be sure to keep
the epoxy out of the threaded part of the nuts.

Fig. 16

26

Installing the motor (# 21 4111 only):

The standard power system for the model is the direct-drive Per­max 400 6V motor 71. The first step is to separate the motor plate
49 from the die-cut sheet; note that the in-fill piece 50 is not
required and should be cut out. The motor plate should butt up
against the fuselage at the rear. The bulkhead is intentionally
narrower than the surface on which it rests; this allows for the
thickness of the motor cowl, which is fitted later. Check that the
motor fits snugly in the motor plate, and glue the parts together
by applying a narrow fillet of 5-minute epoxy on both sides.

Fig. 17a

Run the motor power leads back into the battery compartment.
Temporarily fit the motor cowl, and adjust the position of the
motor and motor plate if necessary. When you are satisfied, glue
the motor plate to the fuselage using 5-minute epoxy.

Installing a motor with integral circular controller

If your power system includes a motor with integral circular
controller, it can be mounted as follows: the motor bulkhead 49/
50 is not used, and instead the wooden spacer 53 is glued in the
motor well, flush at the front. The motor can now be placed on
this and positioned accurately: it should project by 12 mm at the
front. Check this by fitting the motor cowl over it. When everything
fits, glue the motor to the foam on both sides and the wooden
spacer 53 at the bottom with a small fillet of 5-minute epoxy. Use
a small strip of tape to hold it in place while the glue sets.

Fig. 17b

Optional upgrade:

If you decide to install a geared motor, leave the in-fill piece 50
in the motor plate rather than cutting it out. Apply a few drops of
cyano to the die-cut slots to restore the plate’s strength. Drill 2.5
mm Ø holes in the motor plate at the punched points. With the
motor plate in position on the fuselage, hold the geared motor
against the plate. Drill 2 mm Ø holes in the gearbox flange, working
through the existing holes in the motor plate, and fix the gearbox
to the plate using the screws 28. Place this assembly in the
fuselage again, and ascertain the correct position with the help
of the motor cowl, as described earlier. Check that the motor plate
rests flat on the fuselage, and open up the space under the motor
slightly if necessary. The motor case should end flush with the
front face of the fuselage. When you are sure that everything fits
correctly, glue the motor plate to the fuselage using 5-minute
epoxy.

Fig. 18

Motor cowl:

Cut out the cowl 7 and drill holes at the marked points. If you
have installed a geared motor, open up the hole for the output
shaft to the larger marked diameter. Check that the cowl fits really
accurately, trim where necessary, then drill 2.5 mm Ø holes on
both sides for the retaining screws. Screw the cowl to the retaining
plates 51 using the screws 28, then apply 5-minute epoxy to the
edge of the plates facing the fuselage. Taking care not to wipe
the epoxy off, position the motor cowl on the model, push it back
into position on both sides and tape it to the fuselage. This ensures
that the cowl retaining plates are correctly positioned. Allow the
epoxy to set hard, then undo the screws to remove the cowl.

Fig. 19

Installing the undercarriage:

The undercarriage is assembled from the wire legs 80 - 82 and
the spacer sleeves 84. A simple jig is required to ensure correct
alignment. Take a piece of card and draw two parallel lines on it

spaced 100 mm apart. The undercarriage legs are later glued
together and taped down directly over these lines.
Sand the ends of the undercarriage legs, fit the washers 86 on
them, apply 5-minute epoxy, then fit the spacer sleeves 84 and
the wheels 83, and fit the screws 85 while the glue is still soft. Be
sparing with the epoxy, and on no account allow it to get onto
the outside of the spacer sleeves. It is a good idea to grease the
outside of the sleeves lightly before gluing the parts together, as
this effectively prevents them becoming stuck to the wheels. Align
the undercarriage components accurately and leave the assembly
until the epoxy has set hard.

Fig. 20

Joining the wing panels

The first step is to assemble the spar 40 from the two strips of
balsa supplied. Work carefully, exactly as shown in the drawing,
and weight the parts down flat until the glue has set hard.

Fig. 21

Check that the wing panels 10/11 fit together accurately, and trim
the root faces slightly if necessary so that the panels fit together
without any gaps. Pack up one wing tip by about 12 cm, e.g. on a
pile of books, to produce the correct dihedral of about 12°. Use
the prepared spar to aid alignment.

Place the vacuum-moulded wing reinforcement 12 over the rear
part of the wing to fill the opening, and glue the moulding in
place from the underside using 5-minute epoxy. Glue the in-fill
strip 52 in the wing reinforcement at the same time.
Glue the prepared spar and the front wing reinforcement 43 (hole
facing wing leading edge) in the wing. When the glue has set hard,
drill a 4.5 mm Ø hole vertically through the foam from the
underside. Open up this hole on the top surface to accept the
screw sleeve 26.

Fig. 22

Seal the hole in the front wing reinforcement 43 with a strip of
tape, and fill it with epoxy to the point where there is still just
enough space for the reinforcing sleeve 26 itself. Push the sleeve
into place and carefully wipe off excess resin. Apply a strip of
adhesive tape over the top until the glue has set hard. When the
glue has cured, remove the tape and run a 4.5 mm Ø drill bit
through the sleeve and the front reinforcement to clear the hole.
Cut a hole in the recess in the top of the vacuum-moulded rear
reinforcement. Check that the holes line up with the captive nuts
in the fuselage when the wing screws 24/25 are fitted. Trim the
holes as necessary to compensate for any inaccuracy in
construction.

Assembling the model:

Using 5-minute epoxy, glue the “hook” tape 22 in the battery
compartment to take the speed controller and flight pack. Note
that the adhesion of the self-adhesive tape is not sufficient by
itself on styrofoam; glue is required.
Attach the undercarriage using the four rubber bands 30: fit a
rubber band over one of the undercarriage dowels, wind it round
the dowel and the undercarriage leg as many times as possible
whilst keeping the band slightly taut, then slip it over the dowel
again. Repeat the procedure with the other three dowels.

Fig. 23

You are now ready to carry out the first test run using the radio
control system.