Wowings Duck Instructions for use
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Wowings Duck
CONSTRUCTION MANUAL
Copyright 2006 Wowings
www.wowings.com
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Thanks very much for purchasing the Duck combat wing. Although made primarily of soft EPP
foam, this RC slope glider is still capable of causing significant damage to property and serious
personal injury or death to bystanders or yourself. Please ensure that you fly this model in a safe
and responsible manner and obey your local laws and regulations. By building and/or flying the
Duck you assume all responsibility for any damage or injury it may cause. Wowings accepts no
liability for any damage or injury resulting from the use of our products. If you do not agree to these
terms, please contact your place of purchase prior to commencing construction to arrange returning
this kit for a refund.
Please do NOT copy any aspect of the Duck’s design, including its proprietary airfoil sections, even
if only for private use. We have invested a lot of time in developing this unique flying wing and it is
based on a foundation of many years of flying and building experience. These kits are not mass-
produced by a large faceless corporation. We directly rely on, and sincerely appreciate, your
support through the purchase of our glider kits.
Now onto the fun stuff…First, please ensure that nothing is missing from the Duck kit and that
none of the contents have been damaged. If anything is missing or damaged please contact your
place of purchase immediately to make arrangements for replacement parts to be supplied. Your
Duck kit should contain the following:
•2 x EPP foam wing halves
•3 x lengths carbon ribbon spar (two short and one long)
•2 x lengths of balsa (marked with angled lines for fixed trailing edge pieces)
•2 x steel pushrods with clevises attached
•1 x piece of coreflute marked with outlines for fins
•1 x pack of Dubro nylon control horns (total of 2 control horns)
•1 x pack of Dubro E-Z connectors (total of 2 connectors)
. This construction manual!
To complete the kit you will require the following tools and supplies:
•Sharp trimming knife (large retractable disposable type is ideal)
•Sandpaper and sanding block, screwdriver, drill, pliers and ruler
•48mm (2”) wide cross-weave filament tape
•Covering material (eg. coloured packing tape or iron-on film such as UltraCote or Profilm)
•3M “Super 77” or 3M “Multi-Purpose” spray adhesive
•5 minute epoxy glue (eg. Selley’s Araldite)
•CA glue (eg. Pacer’s ZAP CA) or Polyurethane glue (eg. Selley’s Durabond, Gorilla Glue or
Elmer’s ProBond)
•Hot-melt glue –not essential
•Lead for nose weight
The following radio equipment is recommended:
•Rechargeable receiver battery pack in flat configuration of 4 x AA size cells.
•Receiver
•2 x standard size servos (eg. Hitec HS-311).
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Take a few minutes to have a quick read through this entire instruction manual prior to starting so
that you have a basic overview of the steps involved. Please don’t be tempted to deviate from these
instructions unless you are an experienced builder and are confident that your changes won’t
negatively affect the structural integrity or flying performance of the Duck. These instructions are
based in metric units but I have also tried to include the equivalent imperial measurement as much
as possible. For your reference, 1 inch (”) equals 25.4 millimeters (mm). An online version of these
instructions, with colour photos, is located on Wowings website at:
www.wowings.com/instructions/duck.doc
INITIAL WING ASSEMBLY
1. Remove the two wing halves from their beds and glue the wing together using hot-melt
glue, contact adhesive or spray adhesive (epoxy is not ideal because it’s hard and brittle).
2. Locate the two balsa trailing edge pieces. Cut along the angled lines marked using a sharp
blade (many light cutting strokes are better than trying to cut through in one or two goes).
The remainder will be used later for the “elevons” (moveable control surfaces for combined
elevator and aileron function). Place the balsa trailing edge pieces up against the foam sub-
trailing edges (rear edge of the EPP foam wing cores) in the middle of the wing to make sure
that their angled centre joint fits nicely together. The BOTTOM surface of the balsa trailing
edges is the one that had the cut-out lines marked on them (and the surface that meets its
leading edge at a 90 degree angle). When butted up against the foam sub-trailing edge, the
bottom surface of the balsa trailing edge piece should form a straight line continuation of the
foam airfoil shape.
3. Once you are happy that they will fit
nicely, round off the top and bottom edges
of the outer end only of each balsa trailing
edge piece (not where they join together in
the middle) to make covering easier later.
4. Use 5 minute epoxy to glue one of the
balsa trailing edge pieces to the foam. Use
a straight edge (ruler) held against the rear
section of the bottom surface of the wing
and the bottom of the balsa trailing edge to
ensure correct alignment (straight line).
Once the glue has cured repeat this process
for the second balsa trailing edge piece,
also end gluing to the first piece where
they meet at the center of the wing.
5. Measure approximately 25mm (1”) in from
each wingtip along the foam sub-trailing
edge. This will be the width of your
trailing edge fin supports made from small
sections of the two remaining lengths of
balsa trailing edge.
6. Hold one of the lengths of balsa trailing
edge up against the foam sub-trailing edge
at a wingtip so that its end is aligned with
the line you just marked (25mm in from
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the tip). Use a straight edge (ruler) held against the wingtip to mark the correct width
(25mm) and correct angle onto the balsa trailing edge and then cut along this line.
7. Repeat for the second wingtip using the other length of balsa trailing edge. Keep both
remaining pieces for the elevons.
8. The leading edge face of each of these
balsa fin support pieces needs to be shaved
or sanded slightly so that it meets its top
and bottom surface at the same angle ie. so
its cross-section forms an isosceles triangle
9. Round off the top and bottom edges of the
inner end only of each balsa trailing edge
fin support piece (not at the wingtip).
10. Use 5 minute epoxy to glue on the two
balsa trailing edge fin support pieces. They
should be attached so that they form a
reflexed (trailing edge raised) airfoil shape
at the tips. The trailing edge should be raised about 2mm or 3mm above a straight edge
(ruler) held on the underside of the airfoil.
11. The remaining two lengths of balsa trailing edge will now be used to form the two elevons.
Hold one of the pieces so that it is firmly up against the foam sub-trailing edge with its
angled end up against the outer end of the fixed trailing edge piece. They should match up
perfectly ie. the cuts should be parallel. Now slide it away slightly so that there’s a gap of
about 2mm (3/32”) between it and the fixed trailing edge, with its other end underneath the
trailing edge fin support. Mark a line on the elevon piece that is parallel to the fin support
with a 2mm gap ie. the elevon should have a 2mm gap at each end. Now cut out the elevon
along the angled line you just marked.
12. Repeat for the second elevon on the other
wing half.
13. Using a sanding block with rough
sandpaper (or a balsa plane), sand/plane a
45 degree bevel along the leading edge of
each elevon, with the 45 degree opening on
their bottom surface (ie. they’ll be hinged
on the top surface).
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14. Round off the top and bottom edges of each end of both elevons. Put them aside to be
attached later.
RADIO AND SPAR INSTALLATION
15. Gather together all the radio equipment you plan to install into the glider and test that it is
working properly. Ensure that your receiver and transmitter batteries are fully charged.
16. Working on the BOTTOM surface of the wing, measure back about 230mm (9”) from the
tip of the nose. At this point draw a line perpendicular (at right angles) to the wing’s central
join line that extends 305mm (12”) to either side ie. forming a straight line measuring
610mm (24”) centered over the wing’s join line. This marks the location for one of the small
(24”) carbon ribbon spars.
17. Cut a 10mm (3/8”) deep slit along this spar
line and trial fit the carbon ribbon spar.
18. Once you’re happy with the fit, glue the
spar in place using thin CA glue. Dribble
the glue along the top of the spar while it’s
in position. Although the glue bonds
within a couple of seconds when exposed
to air, some of the glue will penetrate into
the foam and can take a couple of hours to
completely cure. CA “kicker” will ensure
it sets rapidly; otherwise you’ll just need to
be patient. Alternatively you can use
polyurethane (PU) glue for gluing the spars in. Please seek advice if you have not used PU
glue previously as it foams and expands while curing and can create a mess of your wing.
19. The following steps now reference the TOP surface of the wing.
20. Draw a line parallel to the leading edge (front edge) of the wing setback 35mm, or 1 3/8”,
(measured perpendicular to the leading edge) extending from the nose to about 1/3 span of
each wing half. In consideration of safety and durability, nothing should be installed or
embedded in front of this line. NB: If you wish to use your Duck in combat competitions
please consult your local rules for the minimum leading edge and nose setback requirements
to ensure this distance complies. Usually it will be a minimum of 1 1/2” (38mm) back from
the leading edge measured chord-wise (line of flight).
21. Centre your receiver’s flat 4xAA size
battery pack on top of the wing about
65mm (2 9/16”) back from the tip of the
nose. Trace around it with a pen.
22. Position your receiver directly behind the
battery pack leaving a 25mm to 35mm (1”
to 1 3/8”) buffer of foam between them.
Trace around it with a pen.
23. Draw two lines 175mm (6 7/8”) either side
of, and parallel to, the wing’s centre join
line. These represent the location of the
pushrods for the elevons.
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24. Position one of your servos so that its
control arm is aligned with the line you
just marked and one of its mounting lugs is
touching the line setback from the leading
edge ie. it should be as far forward as
possible and orientated so that the servo
arm moves directly forwards and
backwards (line of flight). Trace around
the servo body with a pen.
25. Repeat for the other servo on the other half
of the wing.
26. Measure back 50mm (2”) from the leading
edge of one of the wingtips and 5mm
(3/16”) back from the corner of the servo
case and draw a straight line between
them. Repeat for the other half of the wing.
Now draw a gently curving line joining
these two straight lines that sweeps slightly
forward and curves around passing
inbetween the battery pack and receiver
locations. This line marks the location of
the longer (48”) carbon ribbon spar.
27. Cut a 10mm (3/8”) deep slit along this spar
line commencing approximately 50mm
(2”) inwards from each wingtip. Trial fit
the carbon ribbon spar to ensure the slit is
deep enough. The spar should sit about 2mm or 3mm (1/8”) below the top surface of the
wing towards the centre to allow radio leads to pass over.
28. Once you’re happy with the fit, glue the spar in place as per the first one.
29. The remaining small (24”) carbon ribbon spar is used to reinforce the area either side of the
gap between the fixed trailing edge and the elevons. Draw two lines extending 305mm (12”)
down each wing half, parallel to the foam sub trailing edges and setback about 20mm (3/4”)
with the lines joining in a curved arc at the centre join of the wing just a little forward of the
balsa trailing edge. Ensure it doesn’t overlap the spar embedded in the bottom surface.
30. Cut a 10mm (3/8”) deep slit along this spar line. Trial fit the spar and then glue it in place as
per previous spars.
31. Now it’s time to embed your radio equipment into the wing.
32. Cut around the outline you made for the
battery pack all the way through the foam
to the other side. Remove this foam plug
and draw a line vertically up its front side
for later reference.
33. Hold the side of your battery pack against
the side of the foam plug so that it is
centered and trace lines to mark out the
thickness of your battery pack. Repeat this
for all four sides and then cut off a bottom
slice (base) and a top slice (lid) along these
outlines. Mark the top of the slices with an
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“x” for later reference and discard the remaining piece of the plug.
34. Using hot-melt glue (best), spray adhesive (sprayed into a puddle and then spread on) or 5
minute epoxy (not ideal), glue the base slice back into the bottom of the battery cut-out hole,
creating a base for the battery recess. Use the markings you made to orientate it correctly,
ensuring a perfect fit. Put the foam lid aside for later use.
35. Decide whether you want to mount your receiver flush with the top surface of the wing or
embed it beneath the surface. Base this decision on the layout and size of your receiver and
whether you intend to use a switch or plug the battery plug directly into the receiver. I
personally usually use receivers that have the plug sockets on the top surface (and preferably
the crystal as well) and mount them flush with the top surface of the wing. This means the
servo plugs are then sticking up above the wing’s surface (adding a little drag and ugliness),
but it is then simple and convenient to just
plug in and take out the battery lead to turn
it on and off and gain easy access for
charging.
36. Cut around the outline you made for the
receiver all the way through the foam to
the other side. Remove this foam plug and
draw a line vertically up its front side for
later reference.
37. Hold the side of your receiver against the
side of the foam plug in the desired
position (eg. flush with the top surface)
and trace the line(s). Repeat this for all
four sides and then cut off a bottom slice
along this outline, and a top slice if you’ve
decided to have your receiver embedded
below the surface. Mark the top of the
slice(s) with an “x” for later reference and
discard the remaining piece of the plug.
38. Glue the bottom slice of the foam plug into
the bottom of the receiver cut-out hole
forming a base for the receiver recess. Use
the marks on its front side and top to
orientate it correctly, ensuring a perfect fit.
If you have a top slice, put it aside for later
use as a lid over the receiver.
39. Cut around the outlines you made for the
servos with a sharp knife all the way down
through the foam. Push out the foam plug
and mark with a vertical line up its front
side for later reference.
40. Hold the side of your servo against the side
of the foam plug flush with the top surface
of the wing and trace out a line. Repeat this
for all four sides and then cut off a bottom
slice along this outline. Mark the top of the
slice with an “x” for later reference and
discard the remaining piece of the plug.
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41. Glue the bottom slice of the foam plug into the bottom of the servo cut-out hole forming a
base for the servo recess. Use the marks on its front side and top to orientate it correctly,
ensuring a perfect fit.
42. Repeat this process for the second servo recess on the other side of the wing.
43. Mark out the area next to the servo recess required to accommodate the servo arm and its
movement. It will be about 10mm (3/8”) wide by 20mm (3/4”) long. Cut out a triangular
shaped wedge down to the depth of the servo recess’s floor.
44. Repeat for the second servo recess on the other side of the wing.
45. Mark out an area next to the receiver to accommodate the excess length in the battery and
servo leads (and electronic elevon mixer if used). An area approximately 30mm by 40mm (1
3/16” by 1 9/16”) is usually enough. Cut out a foam plug using the same method used for
the battery, receiver and servo recesses and glue back in a 5mm to 10mm (3/16 to 3/8”) slice
to form a base. Keep the remainder of the foam plug for later use.
46. Cut slits into the top surface of the wing to accommodate the battery lead and servo leads
inserted on edge. Twist the leads half a rotation where that cross the spar so that they lie flat
over the top of the spar at the crossing point. Avoid cutting into the spar itself.
47. The receiver antenna should be kept clear (and avoid any crossing) of the servo leads,
battery leads and spar if possible in order to avoid possible interference with the radio signal
from the transmitter. If a crossing is required it’s best to orientate it at 90 degrees to
minimise electromagnetic effects.
48. Cut a slit for the receiver antenna that loops around and then runs up about 25mm (1”) in
from the foam sub-trailing edge of one of the wing halves.
49. Fit the battery pack, receiver and servos
into their recesses. Plug everything
together and test that it is working
correctly. Make sure the servo arms are
centered in the correct position when the
transmitter in on and its trims are neutral.
The servo arms should be pointing directly
upwards, or leaning just slightly rearwards.
Unscrew the servo arms and adjust if
required. Also check for correct direction
of servo travel. Viewed from above, when
your transmitter’s elevator stick is pulled
back for “up” control, both servo arms
should move forwards (towards the leading edge of the wing), and both servo arms should
move backwards when “down” control is applied. When your transmitter’s aileron stick is
moved to the right for “right roll” control, the right servo arm should move forwards and the
left servo arm backwards, and opposite when “left roll” control is applied.
50. Perform a “range check” for your radio equipment now. You should be able to control the
servos smoothly from at least 10 to 15 paces away with your transmitter’s aerial retracted
(not extended at all).
51. Once you are satisfied that your radio equipment is functioning correctly it’s time to start
building it into your glider. Soon retrieval of radio equipment will require surgery on your
glider so it is best to make any necessary adjustments or repairs now. Also keep in mind that
you will need to have access to a means of charging your receiver’s battery pack once it is
embedded into the glider. This can be by means of a special switch with charging socket or
as simple as having access to the battery pack’s plug (perhaps just having it plug into an
exposed socket of your receiver).
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52. Coil up the excess length in the leads and insert them (along with the electronic elevon
mixer if used) into the recess you made next to the receiver. Slice off an appropriate
thickness from the top of the remains of this foam plug to form a lid and glue it in place
flush with the top surface of the wing.
53. Glue the battery recess’lid in place over the battery pack so it’s flush with the top surface of
the wing.
54. If you chose to embed your receiver below the wing surface, glue in the top slice from your
receiver’s foam plug now so that it is flush with the top surface of the wing.
55. Cut and/or sand off any excess glue from around the foam plugs so that they’re all flush
with the surface of the wing.
TAPING & COVERING
These instructions are based on using 48mm (2”) wide strapping tape with cross-woven fiberglass
filaments (running both length-wise and width-wise), hereto referred to simply as “filament tape”.
The instructions outline the process of covering with 48mm (2”) wide coloured polypropylene tape
due to its simplicity and low cost. Those who wish to spend a little extra money and take a little
extra care can use a variety of other covering materials such as Ultracote, Oracover and Profilm.
These iron-on coverings provide a much nicer finish and a little more strength but are a bit trickier
to apply correctly. If using an iron-on covering be sure not to use too high a heat or it may deform
(melt) the foam. Also be careful not to introduce any warps or twists into the wing when shrinking
the covering. 3M Super 77 (“multi-purpose”) spray adhesive is required regardless of the covering
method used and is hereto referred to simply as “spray adhesive”.
56. Thoroughly remove all dust from the glider and your work area.
57. Use masking tape to mask off any exposed radio equipment that you don’t want to get
sprayed with glue.
58. Go outside and spray the entire bottom surface of the wing with spray adhesive and then
place it upside down on a cardboard box (or anything else to keep it up off your work
surface). Let the spray adhesive dry for about 5 to 10 minutes (or until aggressively tacky).
59. Now it’s time to apply the filament tape. This provides essential tensile strength to the EPP
foam wing and helps to keep the glider rigid during flight. For each piece of tape applied
overhang the wing by 25mm to 50mm (1” to 2”) and wrap around to the opposite surface of
the wing. When a piece ends at the balsa trailing edge you can just cut if off flush with the
edge (don’t wrap around). Rub each piece that is laid down with some fine sandpaper to
remove the release agent from the tape’s backing for better adhesion of subsequent layers of
filament tape, spray adhesive and/or covering. Thoroughly wipe off the dust that is created
each time.
60. Working on the bottom surface of the wing (that you just sprayed), apply filament tape
following the spar locations as per the following illustration.
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61. Then apply diagonal strips of filament tape to the wing as per the following illustration.
62. Go outside again and spray the entire top surface of the wing with spray adhesive. Let dry
for about 5 to 10 minutes (or until aggressively tacky).
63. Apply filament tape patches over the servos and receiver (if mounted flush with the top
surface) to hold them securely in place.
64. Working on the top surface of the wing (that you just sprayed), apply filament tape
following the spar locations as per the bottom surface.
65. Apply diagonal strips of filament tape to
the wing as per the bottom surface.
66. Locate the elevons you prepared earlier
and spray their bottom surface with spray
adhesive. Also spray the bottom surface of
the wing’s foam sub-trailing edge. Let dry
for 5 to 10 minutes.
67. Cut a length of filament tape in half
lengthways and cut into twelve 65mm (2
1/2”) long strips.
68. Centre one of the elevons so that there is a
2mm (3/32”) gap between both its ends
and the ends of the fixed balsa trailing
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edge pieces and rotate it around so that it’s lying upside down on top of the wing with its
leading edge flush with the foam sub-trailing edge. Use 3 of the 65mm (2 1/2”) long by
25mm (1”) wide strips of filament tape to attach the balsa elevon to the foam wing by
wrapping around pieces at either end and in the middle of the elevon.
69. Repeat this process for the second elevon.
70. Now rotate the elevons back around so that
they’re in their correct position, butted up
against the foam trailing edge with the 45
degree beveled opening at the bottom.
71. Spray the top of both balsa elevons and the
rear portion of the adjoining foam sub-
trailing edges with spray adhesive. Let dry
for 5 to 10 minutes.
72. Use the 65mm (2 1/2”) long by 25mm (1”)
wide strips of filament tape to attach the
balsa elevon to the top of the foam wing at
either end and in the middle of the elevon.
73. Repeat for the second elevon.
74. Spray the bottom surface of the wing along the wing’s center join line and each wing tip
with spray adhesive. Let dry for 5 to 10 minutes (or until aggressively tacky).
75. Lay a strip of filament tape along the centre chord of the wing, overlapping the panel join
line by about 12mm (1/2”). Lay another strip towards the other side of the join line,
overlapping the first by about 25mm (1”) so the overlap is centered over the panel join line.
Split and wrap around at the leading edge and cut off flush with the trailing edge.
76. Lay a 25mm (1”) wide strip of filament tape chord-wise (LE to TE) at each wing tip. Wrap
around at the leading edge and cut off flush at the trailing edge of the fixed fin support.
77. Spray the top surface of the wing’s center join line and each wing tip with spray adhesive.
Let dry for 5 to 10 minutes (or until aggressively tacky).
78. Lay chord-wise strips of filament tape on the top surface at the wing’s center and wing tips
as per the bottom surface.
79. Spray the leading edges of the wing with spray adhesive and let dry for 5 to 10 minutes (or
until aggressively tacky).
80. Lay a length of filament tape along the leading edges with half the width on the top surface
and half on the bottom surface. Split and wrap the tape around at the nose and wing tips.
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81. It’s now time for covering.
82. Spray the entire underside of the glider
with spray adhesive and let dry for 5 to 10
minutes (or until aggressively tacky).
83. Bend over the elevons and cover the hinge
gap area using 48mm (2”) wide coloured
covering tape.
84. Now start laying down strips of the
covering tape on the wing’s bottom surface
starting at the trailing edge. Let the tape
overhang at the trailing edge (it will be
trimmed later) and tape right over the gaps
between the elevons and fixed trailing edge
(these will be cut free later). Working your
way forwards, lay down each strip of tape
from the middle of the wing out to the
wing tips, overlapping the previous one by
5mm to 10mm (3/16” to 3/8”). Don’t
worry about overlapping the leading edge
of the wing, just trim off flush for now (it
will be covered later).
85. Turn the wing over and spray the entire top
surface of the wing with spray adhesive
and let dry for 5 to 10 minutes (or until
aggressively tacky). Cover as per bottom
surface.
86. Using a straight edge (ruler) and sharp
knife, trim off the tape that is overhanging
the trailing edge of the wing and elevons.
Leave about 3mm (1/8”) back from the
trailing edges so that the tape is sealed to
each other (sticky side to sticky side).
87. Cut the elevons free and then wrap a piece
of covering tape around each exposed end
of the elevons and fixed trailing edges so
that there is no balsa exposed.
LINKAGE HOOK-UP
88. Draw a line on the elevons straight back from each servo arm. The line should be about
25mm (1”) from the end of the elevons. Measure 8mm (5/16”) back (towards TE) along this
line from the elevons’ leading edge (hinge-line) and mark. This will be the position of the
front of the base of the Dubro control horns.
89. Locate the package of Dubro control horns included in the kit. Separate the control horns
and their mounting back plates. Hold a control horn in place and mark the position for the
two holes. Drill the holes and install the control horns by screwing them onto their plastic
back-plate, sandwiching the balsa elevon in-between. Repeat for the second control horn.
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90. Install the Dubro E-Z connectors onto the
control horns. Just use the re-useable nylon
push-nut for now until its position on the
control horn has been finalized. The
second hole from the top is a good place to
start.
91. Locate the two metal pushrods (with
attached steel clevises). Screw the clevises
so that they are positioned towards the
middle of the threaded section of the rods.
92. Push the metal pushrod through the hole in
the E-Z connector (ensuring its lock-screw
is unwound) and attach the clevis to your
servo arm, clamping together with a pair of pliers. Repeat for the second pushrod.
93. Turn on your receiver and transmitter so that the servo arms are centered in their neutral
position. While holding the pushrod in place, move the elevon (the E-Z connector should be
free to slide up and down the pushrod) so that its trailing edge is in line (or about 2mm
above) the fixed trailing edge of the wing. While in this position, tighten the lock-screw on
the EZ-connector to fix it to the pushrod. Repeat for the second elevon.
94. Trim off the excess length of the pushrods using a pair of side-cutters/pliers.
FIN ATTACHMENT
95. Locate the piece of coreflute supplied in
the kit and cut out the two fins as marked.
96. Slide a 25mm (1”) wide, 65mm (2 1/2”)
long piece of filament tape through the slot
in one of the fins and secure it to a wingtip
by wrapping around from the top to the
bottom surface of the wing. The fin should
be positioned up against the end of the
wingtip so that its trailing edge is aligned
with the trailing edge of the fixed balsa fin
support and so that it’s flush with the
bottom surface of the wing.
97. Use another strip of filament tape of the
same size to secure the front portion of the
fin. Wrap it around the wingtip with 2/3 of
its width over the front of the fin.
98. Finally, secure the trailing edge of the fin
with a 25mm (1”) wide, 50mm (2”) length
of filament tape wrapped around with half
its length on the fin and half on the
underside of the wing.
99. Repeat for the second fin on the other
wingtip.
100. Use coloured tape to cover all the
filament tape. This is not just to make it
look prettier but also to protect it from
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sunlight which causes the filament tape to deteriorate over time. In the process also cover
up the slot in the fin to minimize aerodynamic disturbances.
BALANCING
Correct fore-aft balance is achieved by adding lead to the nose of the Duck. You can use a large
fishing sinker or sinkers beaten into shape with a hammer, lead flashing (thin lead sheet)
rolled/beaten into shape, a slurry of lead shot mixed with glue, or even melt it yourself to the correct
size and shape.
For maximum effectiveness the lead should be positioned as far forward as possible but not so far
forward that it adversely affects the glider’s structural durability and/or the safety risk of impacts.
Please consult your local guidelines as to the minimum setback required for lead balance weight if
you intend to use the Duck for slope combat competitions. It’s usually 1 1/2 inches (38mm) from
the wing’s leading edge and sometimes 2” (50mm) from the nose. Measurements are taken chord-
wise (direction of flight), not at right angles to the leading edge. Even if you don’t need it to comply
with competition rules and want to keep the glider’s weight to a minimum, we still recommend
maintaining AT LEAST a 30mm (1 3/16”) buffer of foam at the leading edge, preferably a bit more.
101. Now it’s time for the most important step in the Duck’s construction; adjusting the
glider’s centre of gravity (CG), also known as its balance point. If the glider is not
accurately balanced it will not fly well and may not even fly at all. An incorrect centre of
gravity is one of the most common causes of poor flight performance so take extra care here.
During balance adjustments your glider must have everything already installed in place
ready to fly, namely the fins and pushrods.
102. First, check that your glider is
balanced side to side at the centre-line of
the wing. If required, you can embed a
small piece of lead (or a nail) into one of
the wingtips towards the leading edge. If
one wing half is significantly heavier than
the other the glider can have a tendency to
roll one way better than the other or
consistently drop one wing tip when stalled
(ie. one wing half is stalling prematurely).
Another sign that the wing is unbalanced
(or warped) is when there is a noticeable
difference between the left and right
elevon’s neutral trim position for straight level flight.
103. Now the very critical fore-aft balance. The Duck has been designed to balance at
210mm (8 1/4”) back from the tip of the nose. Carefully measure this distance back from the
nose and clearly mark it with a pen on the bottom surface of the wing. Measure it again to
make sure it’s accurate.
104. Beginners, or those who prefer a friendlier, tamer handling model, will benefit from
a CG up to 5mm further forward ie. a CG of 205mm (8 1/6”) back from the tip of the nose.
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105. Now determine where your glider’s
current balance point is. There are several
ways you can do this. Manufactured
balancing stands are best but you can also
make your own by vertically mounting
sticks of dowel into a base of wood with
the dowel ends sharpened like a
screwdriver tip, or similar arrangements.
As a next best option you can also use your
finger nail if you’re careful enough. The
idea for all these methods is to accurately
find the distance back from the wing’s
nose where it balances ie. where it is
sitting horizontally and tips forwards as
easily as it tips backwards.
106. Temporarily tape varying amounts of lead weight at the position where it will be
embedded into the nose and keep re-checking the balance point until the correct balance is
achieved. You’ll typically require between 60 and 80 grams of lead in the nose. However,
it’s the point at which it balances that is critical not the amount of lead used to achieve this.
Don’t be afraid of adding the necessary weight and don’t try and fudge the CG measurement
and think you’ll get away with it!
107. Once you have accurately determined the amount of lead needed for correct balance
and the exact location of where it needs to be placed, make a cavity in the foam to
accommodate it. Leave at least a 5mm (3/16”) buffer of foam between the lead and the
battery pack. Cut from the bottom surface and stop short of going through to the top surface.
Secure the nose weight and reinforce the surrounding area by covering with a patch of
filament tape.
108. Re-check the CG to make sure it’s exactly 210mm (8 1/4”) back from the nose (or a
little further forward closer to the nose if desired). Adjust if necessary.
FINAL COVERING
109. Cover the nose weight area with coloured covering tape.
110. Lay strips of the coloured covering tape along the leading edges of the wing so that
half of the width is on the top surface and half on the bottom surface. Split and wrap around
the tape at the nose and wing tips.
111. Apply trims, stripes and/or other decorations as desired.
112. The included computer-cut vinyl sticker has both a backing and a “fronting”. To
apply, peel the sticker off its white backing and press it down firmly in the desired location.
Then carefully peel off the transparent “fronting”, leaving the cut-out lettering in place.
FINAL SETUP
113. Turn on your radio equipment and re-check that everything is functioning correctly
and that the elevons are moving in the correct direction. When viewed from the rear, both
elevons should move up when your transmitter’s elevator stick is pulled back for “up”
control and both should move down when the elevator stick is pushed forward for “down”
control. When your transmitter’s aileron stick is moved to the right for “right roll” control,
the right elevon should move up and the left elevon should move down, and when the
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aileron stick is moved to the left for “left roll” control, the left elevon should move up and
the right elevon should move down.
114. Re-check the neutral position of the elevons. Their bottom surface should form a
straight line with the rear half of the foam section of the wing, measured mid-span. This will
typically mean that they’re about 2mm higher than the centre fixed trailing edge due to the
washout (twist) cut into the wing.
115. Adjust the elevons’ throw. Too much movement and the glider will become hard to
control, easier to stall and generally not very fun to fly. Too little movement and the glider
will become unresponsive and also not very fun to fly. The correct amount of elevon
movement for the Duck is determined by its balance point, the pilot’s skill level and the
desired flight characteristics.
116. As a guide, for experienced pilots the trailing edge of the elevons should be able to
move about 15mm (10/16”) up and the same amount down from their neutral position for
aileron control, ie. total movement of 30mm (1 3/16”) and for elevator control the elevons
should only need about 7mm (5/16”) up and same amount down from their neutral position
ie. total movement of about 14mm (9/16”). For beginners (or those wanting a smoother
response) a good starting point would be movement of about 10mm (3/8”) up and 10mm
(3/8”) down from neutral for the aileron control and no more than 5mm (3/16”) up and 5mm
(3/16”) down from neutral for the elevator control. Of course actual movements during
normal flight will be MUCH less, these just represent the maximum throws you’re ever
likely to require for full stick movement. Control throws should be adjusted accordingly to
suit your personal control preferences ie. the relationship of transmitter stick movement to
control surface movement.
117. The amount of control surface movement for the elevons can be adjusted
electronically via some transmitters. If your transmitter has “end point adjustment” (EPA)
then adjust this setting until you achieve the desired amount of elevon movement for both
channels. Some computer radios with in-built elevon mixing may require this adjustment to
be done in the “dual rates” (D/R) setting instead. If you’re using a separate electronic mixer
to achieve the elevon mixing, good ones (like the DigiMix II) will have independently
adjustable rates to achieve your desired control throws exactly.
118. Generally speaking, it’s best to have the pushrod connect to the servo lower down on
the servo arm and connect to the control horn higher up on the arm. This minimizes the
effect of any “slop” (free-play) in the servo gears.
119. Fully charge both your transmitter’s and receiver’s battery packs and perform a
“range check” prior to your first flight. Don’t forget to also make sure that no one else is
using the same radio frequency as you prior to turning on your transmitter at the flying site.
120. The Duck is launched by hand. The
most powerful launching technique is to
grab the wing in the centre at the trailing
edge so that your palm is against the
wing’s bottom surface and your fingers
curled around the trailing edge onto the top
surface. The glider is then thrown like a
ball, keeping the nose pointing level at the
horizon, while your transmitter is held in
the other hand ready for immediate use.
There are also other techniques where the
wing is held by its nose but these are less
powerful. If you are not confident in
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launching a flying wing it’s a good idea to have someone launch it for you, especially for its
maiden flight.
121. You will likely want to fine-tune the amount of elevon movement and perhaps also
slightly adjust the CG location to best suit your personal tastes. Having the balance point
further forward (a couple of millimeters) has a greater stabilizing effect ie. it will tend to
hold onto a level flight path stronger and/or return to a level flight path quicker. The trade-
off with a balance point further forward than it needs to be is that more up trim is required
for level flight, adding to the glider’s drag (reducing maximum flight speed) and reducing
the maximum amount of lift the wing can generate before stalling. The glider also becomes
less responsive to control inputs (less aerobatic and maneuverable), doesn’t retain as much
speed in its turns and doesn’t fly as well upside down. If the CG is too far back it will be
impossible to trim for level flight (unstable in pitch) and will become uncontrollable. You
can experiment with fine adjustments to the CG by taping a small piece of lead (around 10
grams) onto the middle of the wing and progressively moving it forwards and backwards
until you find the “sweet spot”. Presuming it’s trimmed properly for level flight, when
optimally balanced the Duck should tend to pull up only just a little (or hold course) from a
45 degree dive from altitude and require only a very small amount of “down” elevator
control for level flight when flying inverted. If the Duck pulls out quickly by itself from a 45
degree dive and/or requires significant “down” elevator while flying inverted then it is too
nose heavy. Conversely, if the dive becomes steeper and/or no “down” elevator control is
required for inverted flight than it likely needs more nose weight.
122. These instructions won’t go into any details about correct flying techniques, so if
you think you may lack the necessary flying skills for this glider it’s always a good idea to
ask someone with experience to check your glider over prior to its first flight and be there to
offer suggestions to overcome any difficulties you are having flying it. Most people are
usually more than happy to help you if they’re asked nicely.
If you have any questions about the construction process or the flying behaviour of the Duck please
don’t hesitate to contact Wowings by e-mailing [email protected]om and we will respond quickly.
Similarly, feedback (good, bad or a little of both) relating to any aspect of the Duck and these
you and your glider (preferably at your favourite local slope site) or even a video clip. We sincerely
hope that the Duck succeeds in bringing a smile to your face every time you fly it.
HAPPY FLYING!
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