Ripmax WOT 4 MK2 User manual

The Designer
WOT 4 - Instructions
The fascination of flight captured Chris's imagination early on in his life when he started building, from kits and plans,
simple free flight gliders and rubber powered models. By his early teens, Chris was already experimenting with his own
designs, several of which have been featured as constructional plans in various aeromodelling magazines.
It wasn't long before his fiercely competitive nature started to show itself, with Chris channelling his energies into competing
at national level with his own high performance free flight gliders.
In due course, Chris became tempted by the affordability of simple and fairly reliable radio control equipment, so by 1967
he had already designed, built and flown his first radio controlled glider. By 1976 his career in the architectural profession
came to an end when he decided to channel his knowledge and experience into a full time kit manufacturing business,
'Chris Foss Designs'. It soon developed into one of the UK's most successful and respected R/C model businesses, offering
a range of stylish and quality products.
With the advent of reliable and advanced radio control systems, Chris was able to expand his competition flying with
considerable success. His competition highlights include becoming 1977 British National Thermal Soaring Champion,
1986 British National Scale Champion, placing 4th at the 1986 World Scale Championships in Norway, placing 6th at the
1992 World Scale Championships in the USA, and winning both 1992 and 1993 'Radioglide' National Thermal Soaring
Championships.
In the late 70s Chris joined the local gliding club and achieved his ambition to actually fly himself! A few years later he
expanded into powered flight and qualified for his Private Pilot's Licence. By 2007 Chris had accumulated 2000 flying
hours in a wide variety of light aeroplanes, including a vintage Piper Cub, Jungmann aerobatic biplane, various glider tow
planes and his favourite, a Vans RV8 American aerobatic kitplane.
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Chris Foss
Chris Foss
Chris Foss outside his factory in 1990

WOT 4 - Instructions
Introduction
Congratulations on your purchase of the WOT 4 Mk2 ARTF - the
first Almost Ready to Fly version of his timeless classic. Described
as the most exciting sports aerobatic models of all time, it can be
assembled in the minimum of time.
Before commencing construction, please ensure that you read
these instructions in their entirety.
Fitting the Ailerons and Completing Wing
STEP 1
The wings and ailerons are supplied with the hinges loose fitted, ready for
installation. Remove both ailerons and ensure that the hinges are inserted mid-
way in their slots. Using thin cyano, pour a couple of drops onto each hinge -
above and below - ensuring the glue soaks into the hinge and the surrounding
wood.
STEP 2
Carefully slide each aileron into position, ensuring a gap-free hinge line. Make
sure that each aileron lines up with the wing tips and that they are free to move
through their entire travel. Centre each aileron between the root and tip so that
there is an equal gap at both ends. Minimise any hinge gap, then carefully add
a couple of drops of thin cyano to the top and bottom of each hinge ensuring
that the glue does not run through the hinge line onto the bottom of the wing.
Turn the wing over and drop more cyano onto each hinge from the other side.
STEP 3
Prepare your aileron servos by connecting a suitable 300mm extension lead to
each. It is a good idea to use a lead-lock, a turn of insulation tape or heatshrink
tube over the joint for additional security.
STEP 4
Check that your choice of servo fits the servo apertures in the underside of
the wing. Adjust the size of the mounting holes with a sharp knife if required.
Carefully tie each aileron servo's lead to the lead to the length of cotton already
in the wing panels.
STEP 5
Cut away the covering over the servo lead holes in the underside of the wing
panels, and carefully pull the leads through to the centre of the wing using the
cotton thread. Lift out the servo connector through the hole then retain the servo
lead with a short length of tape to stop the lead pulling back into the wing.
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WOT 4 - Instructions
STEP 6
Screw the aileron servos in position using the mounting screws, rubber grommets
and ferrules supplied with your radio. Note that the output arms face towards
the rear of the wing.
STEP 7
Locate the aileron control horns. They are screwed in position on the ailerons
in line with the aileron servo's output arm. Align the row of holes in the horn
with the hingeline. Mark and pilot drill two
mounting holes then screw the horn to the
aileron. The screws thread into the moulded
horn plate on the top surface of the wing.
STEP 8
Do not overtighten the control horn mounting screws - you don't want to crush
the aileron. Turn the model over and trim off any excess thread using side
cutters.
STEP 9
Use a small length of tape to hold each of the ailerons at their neutral position
while you complete the aileron linkages. Ensure that both aileron servos are
centred.
STEP 10
Locate a threaded wire aileron pushrod and attach a nylon clevis to the end.
Connect it to the aileron horn and mark the position the control rod passes over
the servo’s output arm. Bend the pushrod up at 90° at this point.
STEP 11
Slide the aileron servo horn over the wire, re-fit to the servo and snap a moulded
keeper onto the pushrod to retain it as shown.
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WOT 4 - Instructions
STEP 12
Trim off the excess pushrod wire using side cutters. Repeat the procedure for
the second aileron in exactly the same way.
STEP 14
Using a sharp knife, prepare the wings for joining by trimming off any excess
film that has overlapped the root ribs during manufacture.
STEP 15
Locate the wing joining brace. Measure and mark a centre-line on the joining
brace. Coat the inside of the corresponding slot in the wing panel and one half
of the brace with rapid setting epoxy. Ensure that adequate epoxy is used to
fully cover all surfaces.
STEP 16
Insert the brace half-way into one wing panel using the centre-line as a guide.
Wipe off any excess epoxy.
STEP 13
Adjust the pushrods to ensure that the ailerons are centred with the aileron
servos at their neutral position. Test to ensure that both ailerons move freely
across their entire throw. Note that we have fitted short lengths of fuel tube over
the clevis to ensure it cannot open under flight loads.
STEP 17
Protect the covering with masking tape, then spread sufficient epoxy over the
opposite panel joiner slot, wing joiner and root rib. Bring the two panels together
ensuring the epoxy fills the join. Wipe off any excess that squeezes out of the
joint, then use tape to hold the panels together as the adhesive cures.
5

STEP 23
Screw the tailwheel assembly in position with the tailwheel wire inline with the
rear of the fuselage.
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WOT 4 - Instructions
STEP 20
Using a sharp knife, locate the position of the captive nuts already installed
for the undercarriage in the underside of the fuselage. Carefully trim away the
covering with a sharp knife.
STEP 18
Locate the aluminium main undercarriage, wheels and wheel mounting
hardware (mounting screws, plain and nyloc nuts).
STEP 19
Pass the mounting screw through the wheel, screw on a plain nut, then pass
through the main undercarriage. Now fit a nyloc nut on the inside. Hold the
inner nut still and tighten the nyloc nut. Check the wheel rotates freely. Repeat
for the second wheel.
STEP 21
Install the main undercarriage using the two mounting screws supplied.
STEP 22
Locate the pre-bent tailwheel assembly and fit the tailwheel using the collet
supplied.
Installing the Undercarriage

WOT 4 - Instructions
STEP 26
Insert two hinges in each elevator half, ensuring they are located mid-way in
their slots. Using thin cyano, pour a couple of drops onto each hinge - above and
below - ensuring the glue soaks into the hinge and the surrounding wood.
STEP 24
Slide the tailplane into its pre-cut slot in the
rear of the fuselage. Ensure that it is square
to the fuselage and centred in its slot using a
long ruler or string as shown in the diagram
on the right. Mark the tailplane on the top
and bottom where it enters the fuselage
using a soft, water-soluble pen.
STEP 25
Remove the tailplane and cut away the covering from just inside the marked
lines to give a film-free surface for the glue to bond. IMPORTANT: Ensure that
only the film is cut - not the tailplane - as this will seriously weaken the structure.
Roughen the wire elevator joiner to increase the bond strength in the next step.
Now loosely position the joiner at the rear of the tailplane slot. Using epoxy
applied to the exposed wood, glue the tailplane into its slot. Check that the
tailplane is correctly aligned and square to the fuselage. Use masking tape to
protect the covering whilst you do this (removing it as soon as you are satisfied
with the alignment and before the epoxy cures). Any excess epoxy can be
wiped from the model before it cures using methylated spirit or methanol.
STEP 27
Protecting the rear of the tailplane with a strip of masking tape, apply epoxy
to one half of the wire elevator joiner and force it into the corresponding slot
and hole in the elevator half. Now slide the first elevator into position ensuring
that the joiner and both hinges enter their pre-cut slots/hole in the tailplane/
elevator. Ensuring a gap-free hinge line and a 1mm gap between the elevator
and tip, add a couple of drops of thin cyano to the top and bottom of each
hinge. Make sure that the glue does not run through the hinge line onto the
bottom of the tail.
STEP 28
Turn the model over and drop more cyano onto each hinge from the other side.
Repeat for the second elevator half.
STEP 29
Slide the fin into its pre-cut slot in the top of the fuselage. Ensure that it is
pushed down far enough to touch the top of the tailplane. Mark the fin on both
sides where it enters the fuselage using a soft, water-soluble pen.
Tailplane and Fin
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WOT 4 - Instructions
STEP 32
Using epoxy, glue the fin in its slot. Use masking tape to protect the covering
whilst you do this (removing it as soon as you are satisfied with the alignment
and before the epoxy cures).
STEP 30
Remove the fin and cut away the covering from just below the marked lines to
give a film-free surface for the glue to bond. IMPORTANT NOTE: Ensure that only
the film is cut - not the fin - as this will seriously weaken the structure.
STEP 33
Before the glue cures, check that the fin is pushed down fully into its slot in the
top of the fuselage and ensure that it is perpendicular to the tailplane using
a set square. Any excess epoxy can be wiped from the model before it cures
using methylated spirit or methanol.
STEP 31
Using a sharp knife, carefully remove the film from the fuselage from just in
front and behind the fin mounting slot as shown so that the fin has a completely
film-free surface to bond to.
STEP 34
Insert two hinges into the rudder, ensuring they are located mid-way in their
slots. Using thin cyano, pour a couple of drops onto each hinge - above and
below - ensuring the glue soaks into the hinge and the surrounding wood.
STEP 35
Protecting the rear of the fuselage with a strip of masking tape, mix and apply
a small quantity of epoxy to the tailwheel wire. Force some into the slot and
hole in the rudder then slide the rudder in place making sure that both hinges
are located in their slots in the fin and that the tailwheel wire fits neatly into its
recess in the rudder. Wipe off any excess epoxy.
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WOT 4 - Instructions
STEP 37
Locate the closed loop exit slots on each side of the fuselage under the tailplane.
Use a sharp knife to carefully remove the covering from the slots.
STEP 38
Locate the closed loop horn and
install it in the rudder in line with
the slots in the fuselage using the
nuts and washers as shown. Use a
threadlocking compound on the nuts
to ensure they do not loosen due to
engine vibration.
STEP 39
Ensure that the closed loop horn is
aligned to the hinge line as shown.
STEP 40
Cut the supplied single piece of closed loop wire into two equal lengths, then
fit a clevis and locking nut onto the closed loop adaptor. Now loop one piece
of the closed loop wire through the adaptor, and slip the brass tube supplied
over the join. Crimp carefully with pliers or side cutters. Repeat for the second
length of wire.
STEP 36
Ensure that the rudder is aligned to the top of the fin and there is free movement
left and right plus a gap-free hinge line. Now apply a couple of drops of thin
cyano to each side of each hinge taking care not to allow the adhesive to run
through the gap onto the other side of the model.
STEP 41
For additional security, we recommend a drop of cyano on each crimp. Once
this has cured connect one of the clevises to the rudder horn, and feed the wire
through the slot in the fuselage and forward to the servo bay. Repeat for the
second wire, connecting this to the other side of the rudder horn.
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Control
Horn
Threaded
Rod
Nut
Washer

WOT 4 - Instructions
STEP 44
Locate the elevator pushrod exit slot on the right hand side of the fuselage
(looking from the rear). Use a sharp knife to carefully remove the covering from
the slot.
STEP 42
Install your throttle and elevator servos in the pre-fitted servo tray. Note the
orientation of the servo outputs. Now glue the two servo spacers to the tray.
These raise the height of the rudder servo for additional clearance of the
elevator servo.
STEP 45
Locate the factory assembled elevator pushrod and slide it into position from
the radio bay and out through the exit slot. Screw a nylon clevis onto the rod
as shown.
STEP 43
Install the rudder servo and with the servo and rudder centred, connect the
closed loop wires to the servo horn. Slip brass tubing over the wires, ensure
that both wires are tight without being stretched, then crimp and add a drop
of cyano to secure.
STEP 46
Connect the clevis to the elevator horn and with the elevator and servo centred,
mark the point that the pushrod passes the servo output arm. Use a wrap of
masking tape on the rod to make marking it easier.
STEP 47
Form a 90° bend in the pushrod at this point using a pair of pliers.
Radio Installation
10
Throttle
Servo
Elevator
Servo
Servo
Spacers