1245 mm Span
(with Tip Tanks)
Scale Slope Soarer
by Stan Yeo
by PHOENIX MODEL PRODUCTS
MB339 is a stylish crash resistant character scale EPP slope soarer designed
for the sport flyer looking for something different. It will fly in relatively
light winds up to very strong winds with added ballast. Whilst the inverted
performance is limited (it will perform outside loops (bunts)) this is
more than compensated for by its manouvreability and docile handling characteristics.
Building time is anything from 6-8 hours upwards depending on the care
taken and the finish required i.e. whether decorated using coloured vinyl
tape or as, like the protoype, covered in Easycoat.
/ Materials Required
tools required are a modelling knife with spare blades, a pair of sharp
scissors, 180 grade Wet & Dry sanding block, a tube of impact adhesive
such as Evo-Stik, Epoxy, some runny super glue (please observe safety
precautions on packets!) and a soldering iron.
The R/C equipment
used in the prototypes consisted of standard size servos for the elevator
and ailerons (single servo installation), HS300 size, a square 700mA nicad
pack and a Hitec mini Rx. For the twin aileron servo installation any
mini / metal gear micro servos can be used. We recommend the Perkins SuperTec
3002BB minis and HS81MG servos along with a Webra 6 ch. Rx / Hitec 7 ch.
Dual conversion receivers. All the items mentioned are available from
PMP. Impact adhesive is used for all 'foam' joints EXCEPT the mainspars
and the wing brace where Epoxy is used. Superglue is used for all wood
to wood joints except wing brace.
- Lightly sand the fuselage and doublers with 180 grade wet and dry.
Remove dust with a small brush or vacuum cleaner.
- Glue nose & tail sections together using impact adhesive and drill
wing dowel holes in ply nose doublers in positions marked.
- Glue nose and tail doublers in position using impact adhesive. Note
tail doubler position on plan.
- Drill dowel holes in foam. Glue nose former in position. Fit B5 &
B6 12mm balsa blocks in position (fit wing dowels and use as a guide
to get fuselage square).
- Fit elevator servo to blocks B1 & B2 glue in position ensuring they
are flush with the top of the fuselage but not protruding.
- Join fuselage at rear using surplus foam from fuselage bottom. Taper
underside of fuselage top in tailplane area and dry fit. Cut to shape
and radius corners at base of fin.
- Mark elevator hinge line on Correx tailplane and remove strip of
plastic on one side to form hinge line. The elevator hinge line is 6
whole flutes forward of the trailing edge. Push fit elevator joiner
- Fit Fin to Tailplane using strip of 25mm CW (cross-weave) tape. Glue
tailplane to fuselage. Fit fuselage top, cockpit and nose cone.
- Check which side the control rod must be connected to the elevator
servo for the controls to operate in the correct sense and plan route
for elevator control rod.
- Install elevator control rod. Bore hole in foam by heating the end
10mm of elevator control rod. Drill and fit control rod support blocks
B3 & 4. Support control rod in middle using scrap foam from wing outers.
- Fit fuselage bottoms (front and rear) checking that fuselage is not
bent or twisted.
- Cover fuselage using CW tape. In restricted areas such as the base
of the fin etc strip CW tape to 25mm wide. In high stress areas such
as under the leading edge of the tailplane and above the wing trailing
edge apply an EXTRA layer of tape for added strength.
Building the Wings.
- Lightly sand wing surfaces and remove dust as before. Using a SHARP
scalpel and straight edge trim spar slots to size. Unfortunately due
to restriction in the CNC foam cutting machines tapered wings produce
tapered spar slots. Remove waste from wing brace slot.
- Fit 3mm
x 10mm hardwood trailing edges using impact adhesive. Ensure that the
TE is straight otherwise difficulty will be experienced in fitting the
- Fit top
wing spars using Epoxy, cut to length and join wings upside down (helps
overcome the droop wing look). TE should be STRAIGHT i.e. no sweep either
- Fit wing
brace and bottom wing spars, again using Epoxy. Trim spars to length
and shape wing tips.
- If fitting
individual wing servos cut boxes for the servos in the wing behind the
main spar. Distance from wing joint will depend on the length of servo
lead. If servo lead is too short use servo extension leads to allow
mounting of the servo further outboard. With mini servos the servo may
protrude slightly from top of the wing.
- If using
a single servo to drive the ailerons mount the servo along the wing
join behind the mainspars and use the torque rods supplied. Relieve
ply doubler to accommodate the torque rods to prevent any unnecessary
friction. Using 50mm CW tape, tape torque rods in position.
a rectangular template of the aileron servo(s) ignoring lugs but allowing
for output arm and cut rectangular hole(s) in wing. Servo(s) should
be a snug fit in hole. If fitting outboard wing servos use foam block
removed to restore wing lower surface and a hacksaw blade to cut recess
for servo lugs.
covering the wing with CW Tape remove the aileron servo(s) and prime
the foam with a spray on impact adhesive. Hold nozzle 40 to 50 mm away
from foam and allow 10 minutes for solvent to evaporate before covering.
wing with CW tape. Start by laying a strip along the TE of each wing
panel. Each strip should overlap the wing joint by 100mm each side.
This provides increased strength and stiffness at the wing joint. Work
forward, bottom first, overlapping the previous strip by 6-10mm. At
the leading edge overlap tape by 10 mm.
- Cut ailerons
to size and shape aileron leading edge. The ailerons are top hinged
for twin servo installation and centre hinged for single servo installation.
the ailerons, starting at TE using either CW tape or coloured vinyl
ailerons using M&M Developments Sticky Hinge supplied in kit. If top
hinging use either aileron covering tape as a hinge or the M&M Developments
Sticky Hinge. Cut Sticky Hinge into 50mm lengths, 3 per aileron. If
desired ailerons can be sealed between hinge sections using 6mm sq soft
draft excluder trimmed to 1.5mm thick.
model using stick on trim such as Protrim / Solartrim / Fablon or coloured
vinyl tape which is available from PMP. Alternatively an iron-on film
such as Easycoat can be used (Easycoat comes highly recommended and
is a polyester film with excellent shrinkage properties)
- Fit control
linkages and adjust to obtain required throws (see flying section).
- Fit tip
tanks if desired using Velcro.
- Set the controls to give the following movements for initial flights:
- Elevator +/- 12mm
- Ailerons +/- 15mm
- Flaps (if fitted) +/- 7mm
- Rudder (optional) +/- 30 degrees
- Adjust balance to within recommended limits (100mm +/- 5mm from LE).
Prototypes required 20 - 40gms of lead in the nose. Check alignment
of wing and tailplane and wing to tailplane incidence (bottom of flying
surfaces should be parallel). Laterally balance wing and check that
it is not twisted. If the wing is twisted, twist back in the required
direction and re-smooth covering tape with warm iron. If model is fitted
with flaperons check zero flap is in fact zero flap otherwise performance
will be impaired!
- Please remember all aerobatic manoeuvres require energy in the form
of speed to perform the manoeuvre. If the model has insufficient speed
it will fail to complete the manoeuvre or perform it half-heartedly.
Vertical or near vertical dives are not an efficient way to build up
speed. A 30 deg. dive is much more efficient. Avoid sudden control inputs.
In most cases all they do is scrub off speed and lose height. Try to
fly smoothly as not only do the manoeuvres look better but you will
be able to perform more of them before having to regain height. With
tip tanks fitted and only aileron elevator control the AerMacchi spins
well and takes approximately ONE turn to come out of it.
- Pay particular attention to positioning and where others are in the
- If the lift is good or you are having difficulty penetrating into
wind try taping ballast under the balance point. This will increase
penetration and help the model maintain speed through the manoeuvres.
- The suggested control settings are a starting point and can be adjusted
to suit your personal tastes. Adjust the balance point so that when
the model is trimmed the elevator is more or less in the neutral position.
- The AerMacchi will take a lot of punishment although the tiptanks
can get knocked off in 'screwed' landing. It is excellent for building
confidence and will add another dimension to your flying but please
remember if you take a big enough hammer to anything it will break.
Store the model away from direct sunlight in a cool place as the CW
tape degrades in UV light. Do not rest anything on the Correx tailplane
as this will deform it.
- Finally should you require further assistance or advice please contact
us either by letter, telephone, email or visit our website (http:///www.phoenixmp.com)
where you will find useful information on sloping etc.