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Crash Resistant Sports Aerobatic Slope Soarer
by Stan Yeo
by PHOENIX MODEL PRODUCTS
is a stylish, high performance, crash resistant, sports aerobatic slope
soarer designed to meet the ever increasing demands of the discerning
everyday sports flyer. It will do all manoeuvres expected of a sports
aerobatic sloper i.e. sustained inverted flight, loops, rolls and bunts
etc., It will also do a 'bun-roll' (an outside loop with a roll at the
bottom) a manoeuvre few aerobatic slopers are capable of. Despite this
the Bedlam is a graceful docile model to fly and will thermal turn with
the best of them when the need arises.
In its basic
form the Bedlam can be flown with any 4 channel transmitter but to achieve
the best from the model a computerised transmitter is recommended so that
the ailerons can be used as flaps (flapperons) and the flaps can then
be coupled with the elevator to improve the 'looping' performance. The
flaps can also be used assist landings in confined spaces.
not attempt to use plastic geared servos - they do not last long in EPP
models! Our EPP models are a little more complex to build than most of
their contemporaries this is more than compensated for in their performance.
Building time however is still relatively short when compared to that
of an equivalent wood foam model.
The R/C Equipment
used in the prototypes consisted of four metal gear micro servos (HS81MG/
85MG) a 2/3 AF size Rx flat Nicad pack plus a JR R700 / Hitec Slimline
/ Webra 6 / Futaba 147F Rx, two servo extension leads and a switch harness.
All the items are available from PMP at competitive prices.
/ Materials Required
tools required are a modelling knife with spare blades, 180 grade Wet
& Dry sanding block, a can of spray impact adhesive such as Stikatak,
some runny super glue (please observe safety precautions on packets!),
12 minute epoxy a soldering iron and a long straight.
sand the fuselage sides, top and bottom with 180 grade wet and dry to
remove the 'release' agent. Remove dust with a small brush or vacuum
position of 4.5mm distance pieces (5 off) to fuselage sides ensuring
you have a left and right side!
4.5mm sq. strip and triangular nose strips to fuselage sides.
wing seats in position.
nose former and the other four 4.5mm distance pieces to one fuselage
side ensuring they are all perpendicular (use set square). Check dowel
former can be slid in position.
fuselage sides together over plan checking that the fuselage sides are
correctly aligned using set square.
- Cut 1.5mm
ply fuselage top to length and superglue in position.
Step 8 above for fuselage bottom allowing for wing dowel plate.
triangular strip to outside of fuselage to extend tailplane seat.
Wing Nut block assembly as per plan. Slide into position and hold in
place with scrap foam rubber. Slide into position the 6mm ply Wing Dowel
- Fit the
wing to the fuselage and mark position of wing dowel hole on dowel plate.
Tip - wet end of dowel tube with felt tip pen to leave impression on
dowel plate. Ensure dowel hole is in middle of dowel plate and dill
dowel hole. Do not allow centre of dowel hole to drift towards bottom
of fuselage as this will prevent wing fitting snugly in wing seat.
dowel former in position. If necessary, slide former 'in & out' as appropriate
to compensate for any inaccuracies in drilling dowel hole.
- Fit triangular
strip to front of dowel former (see plan).
- Fit wing
to fuselage and locate position of wing nut assembly.
nut assembly in position.
EPP sheets to fuselage sides using spray adhesive (spray both surfaces).
Allow a couple of minutes for solvent in adhesive to evaporate before
fitting EPP to fuselage. Extend the EPP past the nose former by at least
12mm to form nose weight cavity (see plan). Due to the length of the
EPP blocks this will leave a gap at the tail. Fill this gap with an
off-cut. Also remember this is a ONE shot operation!
the EPP to shape of fuselage using White Spirit to lubricate knife.
The best tool for this operation is one made from a broken piece of
hacksaw blade approximately a 75mm long. Grind the teeth off without
getting the blade so hot that it loses its temper and goes soft. Sharpen
blade on a whetstone or oilstone so that you could almost shave with
it! The advantage of this blade over commercial blades is that it is
flexible allowing the 'handle' to be bent out of the way when cutting
the EPP to achieve an acute cutting angle.
Construct Elevator and Rudder hinges by removing 1.5mm wide strip
of Correx on one side of tailplane / Fin as per the plan.
- If applicable
fit the optional 3mm dia. carbon rods into fin. Wrap carbon rods in
masking tape to produce a snug fit (see plan).
balsa strips to base of fin after shaping. Check fin sits vertically
on a flat surface.
centreline on top of tailplane (hinge cut-out underneath) ensuring that
it is at right angles to tailplane axis.
Fin to tailplane ensuring it is square and vertical. If the Fin is not
vertical slice along the balsa strip on the side the Fin is leaning
towards and insert a piece of thin cardboard. Superglue in place.
the wing on the fuselage. Check that it is square to the fuselage. Check
tailplane seat is clean and flat.
Epoxy tailplane assembly to fuselage. Check the tailplane is parallel
to the wing and the Fin is in line with the axis of the fuselage and
perpendicular. The epoxy an be 'bulked' out using an appropriate filler
such micro balloons. This will assist in 'seating' the tailplane.
- Fit rudder
and elevator pushrods. Anchor to fuselage on opposite side to exit at
mid-point and end. Throughout this operation the pushrod must remain
in the conduit and checked regularly for free movement.
plastic aerial tube / Fin fairing to Fin leading edge using impact adhesive
such as Evo-Stick. Tape in position until glue is set (24hrs).
10mm thick EPP to fuselage top again extending EPP forward of the nose
former and stopping at Fin base.
EPP sheet to fuselage bottom at nose. Again extending beyond nose former.
Glue EPP sheet to rear of Fuselage and trim to shape.
approximately 150grams of roofing lead to front of nose former in cavity
formed by EPP sides. This is typically 2mm thick and equates to 5 layers
of lead. Flatten lead before fitting. Roofing lead is available from
the scrap yard at approximately £1.00 a kilo.
EPP in front of nose weight to provide flat surface on which to glue
- Fit nose
block and shape fuselage i.e. round corners using sharp knife and 180
grade wet & Dry (use dry!).
- Fit Rudder
and Elevator servos to balsa blocks but do not glue in place (see plan).
Bias servos away from fuselage side that connects to the pushrod to
get maximum control movement from servo. Position servo assembly in
fuselage and superglue in place.
fuselage with Impact Adhesive and cover fuselage using CW tape. Overlap
each strip by 6 - 10 mm or 1/4 to 3/8 inch. If top covering is a polyester
iron film then the CW tape can be laid diagonally (see plan). Use Film
Iron to remove wrinkles around compound curves. Temperature required
for this operation is fairly critical. Do not dwell in one spot too
long to avoid damaging the foam. Use white spirit to lubricate cutting
knife. 36. After covering fuselage connect up control surfaces. Check
all transmitter trims are in neutral. If using a computerised transmitter
use the sub-trim facility to zero the servo output arms and lock the
control surfaces in neutral before cutting pushrods to length.
impact adhesive can be removed using white spirit.
sand wing surfaces and remove dust as before. Trim and sand spar slots
to accommodate mainspars. This is best achieved using very sharp knife
and a spar length straight edge (tip - stick 180 grade we & Dry to under
surface to prevent slippage) plus a short length of 100mm thick ply
fitted with Wet & Dry along the edge to final sand the spar slot. Unfortunately
CNC cutting tapered wings with spar slots results in a tapered spar
slot due to the way CNC cutters work.
waste from wing bracing slots.
- Fit top
wing spars using Epoxy keeping spar bracing slots free of Epoxy. Place
packing tape along spars, place wing on a flat surface. Hold flat with
weights until epoxy set.
spars to length.
- Fit 6mm
sq trailing edges using epoxy again keeping bracing slots free of epoxy.
Use masking tape to hold spar in position whilst Epoxy sets. Trim to
- Dry fit
bottom mainspars and trim to size.
- Dry assemble
wing and check wing roots 'mate'. Adjust as necessary.
wing upside down fit wing brace and bottom wing spars.
- Fit rear
spar brace and trim to size when epoxy set.
- Fit rear
wing brace using epoxy.
Elevons and wing centre by laminating 0.8mm ply and balsa trailing using
spray impact adhesive. Place under weight until adhesive has properly
centre section to wing observing wing reflex (apparent up elevator).
Refer to wing seat on fuselage.
- Fit 0.8mm
ply ends to centre section and one end of each Elevon.
wing tips to shape and trim Elevons to size. Sand to shape.
balsa block in position at wing join. Bottom of block should be flush
with bottom surface of wing.
top surface of block to shape of top surface of wing. DO NOT trim bottom
Locate centre of balsa block and centre of wing leading edge. Drill
hole for 5mm diameter brass tube the houses 4.5mm diameter hardwood
wing locating dowel.
wing dowel tube in place. Mark centre of tube hole on 6mm ply dowel
locater in fuselage. Use felt tip pen to assist in this.
hole for M5 wing bolt in wing and ply bolt plate. Do not drill through
- Fit 1.5mm
ply wing bolt reinforcing plate using superglue.
position of wing servos (plan drawing is NOT full size. Position of
servo is dependant on servo lead length. Allow 30mm from end of plug
to servo lead exit from wing for connecting to receiver extension lead
when fitting wing. Note servo arms both point outboard of wing.
- Cut rectangular
hole for servo in wing ignoring servo mounting lugs.
Cut slot in EPP for servo lugs and fit servo so that it is flush with
top of wing. Note gap between top of servo and bottom of wing. From
block of EPP removed for servo from wing slice off the required amount
and fit in this void.
wing servos for covering.
wing with spray adhesive and cover wing with CW tape. For torsional
rigidity cover the wing with CW tape diagonally. There is no need to
wrap around rear spar but do overlap by 5 - 10mm at leading edge. For
smooth finish do not overlap CW Tape. Use film iron to remove wrinkles
covering fit aileron servos. Cut vertical slot in wing to hide servo
wing with either coloured vinyl tape or an iron on polyester film (NOT
polypropylene it stretches!). This is necessary for two reasons, one
to decorate the model and secondly to protect the CW Tape from the effects
of ultra violet light. If film covering roughen surface of CW Tape a
lightly spray with impact adhesive.
Elevons in an iron on film in suitable colour. DO NOT use CW or vinyl
Ailerons using Sellotape diamond as shown on the plan.
- Fit control
linkages and adjust to obtain required throws (see flying section).
Before manufacturing control pushrods centre the servos first ensuring
the aileron trims are in neutral. If applicable use sub-trim facility
for final adjustment and tape ailerons in neutral using masking tape.
Tip - place masking tape under pushrod when soldering to avoid solder
damaging covering should it drip.
- DO NOT
replace the plastic mini-snaplinks with metal devises. In the event
of a mishap the plastic snaplinks will break thereby reducing the risk
of damage to the elevon servos.
the design performance of any model care must be taken in
setting up the controls and balancing the model, both laterally (wing
tip to wing tip) and longitudinally (nose to tail). The Bedlam is no exception.
Control movements must be symmetrical i.e. the same both sides.
- Set the
controls to give the following movements for initial flights:
+/- 12mm Rudder +/- 45 degrees
6mm UP Down Elevator 5mm DOWN Up Elevator
Point 100mm +/- 3mm from LE at back of dowel former.
balance to within recommended limits. Prototypes required a small amount
of additional nose-weight to that fitted in the nose. Do not worry about
the amount of lead carried in the nose. With slope soarers there is
an optimum weight for a model. If the model is too light or too heavy
then the performance will suffer. The only energy a model has to perform
aerobatics is that due to its speed and weight. If too light then it
will run out of 'puff' before it has completed the manoeuvre. Too heavy
and the excess drag created as a result of the extra work the wing has
to do will either result in a tip stall or a failure to complete the
manoeuvre for a similar reason to that above.
all aerobatic manoeuvres require energy to perform them. If the model
has insufficient speed it will fall out of the manoeuvre or perform
it half-heartedly. Vertical or near vertical dives are not an efficient
way to build up speed, 20- 30 degree dives are much more efficient.
Avoid sudden control inputs unless you intentionally want to carry out
'flick' manoeuvres. In most cases all they do is scrub off speed and
lose height. Try to fly smoothly with the minimum of control input as
not only do the manoeuvres look better but you will be able to perform
more of them before having to regain height. Try stringing manoeuvres
together paying particular attention to positioning. Be creative and
set yourself targets for each flying session.
- If the
lift is very good or you are having difficulty penetrating into wind
try ballasting the model. This will increase penetration and help to
model maintain speed through manoeuvres. Note when adding ballast take
care not to disturb the balance point. We have found the optimum ballast
to be about 200 grams. Over-ballasting any model as previously mentioned
leads to a degradation in performance often accompanied by tendency
to tip stall.
- The suggested
control settings are a starting point and can be adjusted to suit your
personal tastes. An indication that the balance point is about right
can be gauged by the amount of down elevator required for smooth inverted
flight and how the model naturally recovers from a dive with the controls
(sticks) in neutral.
- If you
are using a computerised transmitter program in positive Exponential
on the Aileron and Elevator controls. This will 'soften' the controls
around the neutral position and facilitate smoother flying particularly
on the elevator control.
- The Bedlam
will take a lot of punishment. 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. The CW tape
used for covering also degrades in ultra-violet light so store the model
in a relatively cool place away from direct sunlight.
landing the Bedlam treat it like you would a conventional wood / foam
model or moulded machine and fly a conventional landing circuit (see
Prepare to Land article on our website). Using the typical combat style
flying wing landing technique is not only high risk due to the Bedlam's
increased flying speed but does nothing to improve your landing technique
in preparation for the day when you fly a model that breaks more easily
when it hits the ground.
- The modified
MH42 wing section is very efficient and performs well in light lift
so with good ballast selection Bedlam will cope with almost any wind
/ lift conditions you are inclined to fly in.
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.
and safe landings
Top Slope Sites
to slope soaring or want to visit a new site. Check out the PMP
slope site listings.
which shows PMP will be attending this year
about the design principles behind the PMP range of models
Articles written by Stan Yeo for national magazines on a wide range
instructions on how to construct our EPP Models
to Club Sites and Product Information.