Mountain Models DuskStik User manual

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DuskStik Builder’s
Manual
Thank you for purchasing the DuskStik. The DuskStik has been designed to be easy to build, easy to fly,
and strong enough to withstand the abuse of a beginner pilot. The plans have been written for the first
time builder. Take your time and enjoy building this plane. It is a great, well-behaved flyer. I have had
many wonderful hours flying it and hope you will too.
Doug May 17, 2001
Last revised March 25, 2002
Copyright 2001 Douglas Binder, Mountain Models
www.mountainmodels.com
[phone]
[phone] fax

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Required Equipment
To build:
! Xacto with #11 blades
! Thin and Thick CA – Cyanoacrylate glue (Super Glue)
! Sanding block with 200 grit sandpaper
! Smooth, flat work table
! Wax paper to protect plans
! Needle nose pliers
! Wire cutters
! Hobby Iron for applying covering – also called a sealing iron
To fly:
! Three channel radio (The FMA Extreme 5 is highly recommended, second is the GWS-R4P
micro receiver. The Hitec Feather with the Laser 4 transmitter provides a low cost solution for a
first time radio, however, the Feather receiver has a reputation for glitching easily. In my opinion,
if you can afford it, you are much better off starting with a good radio such as the Hitec Flash 5 G
with HS55 servos substituted for the HS80s that normally come with it.)
! Two micro servos: Hitec HS50s, HS55s, or GWS Pico servos recommended
! GWS A motor with 1047 propeller
! Motor Speed Control: GWS ICS50 or GS100 suggested
! Battery pack: 7 cell 300mAH Nickel Metal Hydride recommended.
Parts List
1 ea – 1/32” laser cut balsa spar webbing sheet
1 ea – 3/32” laser cut balsa sheet
1 ea – 1/16” laser cut balsa rib sheet
1 ea – 1/32” laser cut plywood sheet
4 ea – 1/8”x1/4”x36” balsa spars
2 ea – 1/8”x36” hardwood dowel leading edge
1 ea – 1/16”x3/4”x5” plywood battery holder
4 ea – 3/16”x5/16”x2 ¾” balsa breakaway motor mount (3 spares)
1 ea – .085”x3/8”x2 1/8” solid wood servo mount spacer
1 ea – 1/4" carbon fiber fuselage tube
2 ea – .050” carbon fiber pushrods
2 ea – 1/4"x7” carbon fiber spar reinforcement tape
1 ea – 1/16” landing gear wire
1 ea – 14” thin music wire for tail skid and pushrod ends
1 ea – Heat shrink tubing for pushrods and wheel retainers
1 ea – Velcro strip for mounting the battery
1 ea – Kevlar thread for attaching landing gear and skid to fuselage
1 ea – Wire tie pushrod retainer
1 ea – Tire Rubber
2 ea – 1/2” long aluminum tube wheel axle bearings
1 ea – Roll of covering material

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Notes and Hints
• The plywood built up parts should be assembled with thick CA or white glue. Thin CA sets up
too fast to allow you to align the parts.
• The DuskStik has been designed with weight in mind. Parts and reinforcements were chosen so as
to keep the plane light. Special care must be taken when making glue joints to ensure that the
DuskStik can survive rough landings.
• There is very little that is critical when building the DuskStik. The only thing that requires special
attention is to make sure the wings are not twisted. If the wings are straight, the DuskStik should
fly hands-off without any trim.
• Heat shrink can be heated with a hairdryer, a soldering iron, or, if you dare, with a lighter. Pay
close attention to what is near the heat shrink when you are heating it.
• You really need the sealing iron. You will find putting on the covering so much easier. They are
reasonably inexpensive and invaluable
DuskStik Assembly
Motor Mount, Wing Mount, Wheel, and Servo Mount Assembly
1. Break apart all plywood parts, set control horns aside.
2. Glue two motor mounts together with thick CA.
Fig 1.
3. Cut out wing mount and wing yoke from 3/32” balsa.
4. Sandwich balsa wing mount with plywood wing mounts (plywood-balsa-plywood), glue with
thick CA or white glue. Do the same for the wing yoke.
5. Slide the yoke into the mount, insuring that the yoke is flush with the top of the mount. Glue with
thick CA.

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Fig 2.
Wing Mount Flush Wing Yoke
6. Build wheels the same as in step 3, i.e., sandwich plywood-balsa-plywood. In this case it is
plywood hub, balsa hub, plywood wheel, balsa wheel, plywood wheel, balsa hub, plywood hub.
Slide the parts over the aluminum tube and get everything aligned. The smaller round punch-out
with the axle hole is the wheel hub. Flow thin CA over the wheel to glue it taking care to not get
CA in the aluminum tube.
Fig 3.
Wrap the tire rubber around your wheel to measure it and cut it 1/16" too short. Glue the ends
together with CA. You now have a ring. Slip the ring over the wheel, center it then glue it to the
wheel with thin CA.
7. Using four plywood servo mounts and solid wood servo mount spacer, glue up servo mount with
thick CA. Spacing is determined by the servos you use. The servo should fit snug but not tight.
Trim excess solid wood.
Fig 4.
Spacing determined by servos.

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Vertical Stabilizer, Rudder, Horizontal Stabilizer, and Elevator Assembly
The tail assemblies are made up from parts found on the 3/32” balsa laser cut sheet. The plans are laid out
on a flat worktable and taped down, and then a sheet of wax paper is laid over the plans. This will protect
the plans from the glue. The pieces of balsa are positioned over the plans. Each joint can be glued by
holding the two pieces in place and applying a drop of thin CA to the joint. In the past, you may have
used pins to hold parts down, but I find this process to be faster and you don’t have to worry about the pin
damaging the 1/8” balsa. You do have to worry about keeping your fingers far enough away from the
joints or your fingers will become part of the model.
Fig 5.
Rudder
Vertical Stabilizer
Horizontal Stabilizer
Elevator
1. Tape plans for vertical stabilizer and rudder to a flat building surface, and cover with wax paper.
2. Using the drawing as a guide, glue with thin CA the vertical stabilizer and rudder. When dry,
remove from wax paper and reinforce joints with thick CA. Set aside.
3. Using the drawing as a guide, glue with thin CA the horizontal stabilizer and elevator. When dry,
remove from wax paper and reinforce joints with thick CA. Set aside.
Wing Assembly
Note: The wing can be built as a dihedral or polydihedral, standard 42” or extended 50” wing. There
are two extra ribs on the 3/32” balsa sheet for the extended wing. The standard wing is a good, all
around wing, which can handle small amounts of wind. The extended wing is more suited for thermal
chasing and slower flight but will be more susceptible to gusts. The polydihedral wing is an excellent
wing for beginners. It is very stable and handles slow flight exceptionally well. The dihedral wing
will loop better and is more fun at higher speeds.
Building the extended wing involves adding an additional rib to the end of each wing and moving the
polydihedral break out one rib.

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1. If you are not building the extended wing, cut off the extra length of the trailing edge. Cut outside
the notch (keep the notch).
Fig 6.
If you are building the extended wing, glue the trailing edge extensions on to the trailing edge
pieces with thick CA. Why didn’t I just make the trailing edge 25”? The laser cutter will only cut
up to 24”! Fig 7.
2. Sand the rear edge of the trailing edge to make it rounded.
Fig 8.
Back of Trailing Edge rounded

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3. Remove ribs from 1/16” balsa sheet. Stack up the ribs and lightly sand the edges to remove the
little nubs that held the ribs in the sheet.
4. Tape the wing plans down on a flat building surface and cover the wing half you are building with
a sheet of wax paper to keep the glue off the plans.
Polydihedral Wing Assembly (To build Dihedral Wing, go to step 26)
Note: R1 through R8 indicate rib 1 through rib 8.
Build center wing section
Fig 9.
5. Cut trailing edge and lower spar (1/8”x1/4”) at the polydihedral break as marked on the plans.
This is 14 inches out, or 17.5 inches out for the extended wing. Cut outside the notch on the
trailing edge.
6. Position trailing edge and lower spar over plans.
7. Position ribs R2 – R4 (R2 - R5 for extended wing) on lower spar and trailing edge. Note that you
are not gluing the end ribs on now, just the middle ribs.
8. When everything is aligned, glue ribs in place with thin CA.
9. Use rib gauge as shown to angle R1 inward. This creates the proper wing angle between the
center wings.
Fig 10.
10. Use rib gauge to angle R5 inward (R6 for extended wing) inward.
11. Position top spar (1/8”x1/4”) across R1 – R5 (R6 for extended wing), mark length, cut, and glue
with thin CA. Cut the spar so that the cut matches the angle of the ribs.
12. Position 1/8” leading edge dowel from R1 – R5 (R6 for extended wing), mark, cut, and glue with
thick CA. The 1/8” dowel commonly has some warp to it. It is not necessary to remove the warp
but it is a good idea to orient the bow horizontally, not vertically
13. Cut to length and glue with thin CA the 4ea 1/32” balsa spar webbing between R1 and R5.

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14. Glue the eight ¾” triangle braces in place with thick CA.
Fig 11.
Spar Webbing Braces Sand flush with rib
15. Sand the ends of the leading edge, trailing edge, and two spars so that they are flush with ribs.
Build outer wing section
We will build the outer wing directly onto the center wing to ensure a good fit between the two. The
outer edge of the center wing will be held down with tape to hold it in position, and the inner edge of
the center wing will be lifted to form the correct angle between the center and outer edge. See Fig 13.
16. Tape R5 (R6 for extended wing) to wax paper over plans.
17. Lift R1 until it is 5” high, measured from the bottom of the rib.. This will set the proper dihedral
angle for the outside wing (for the extended wing, measure 5” from R2).
18. Sand outer-lower spar until it mates with center wing section lower spar. Cut to length.
19. Sand outer-trailing edge to mate.
20. Position trailing edge and lower spar over plans.
21. Position R6 and R7 (R7 and R8 extended) over spar and trailing edge and glue with thin CA.
22. Position top spar (1/8”x1/4”), mark length, cut, and glue with thin CA. Cut the spar so that the cut
matches the angle of the other spar so that they meet flush.
23. Position 1/8” leading edge dowel, mark, cut, and glue with thick CA. You should sand the dowel
so that it is flush with the inner leading edge dowel.
24. Cut to length and glue with thin CA the remaining 1/32” balsa spar webbing. On the extended
wing, the last rib bay does not get spar webbing.
25. Add the four ¾” triangle braces.
26. Make other half of wing following the previous steps.
27. Go to “Completing the wing”.
Fig 12.
Outer rib of center wing taped to plan. Inner rib raised 5”.

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Dihedral Wing Assembly
28. Cut trailing edge and lower spar (1/8”x1/4”) to length as marked on the plans. This is 21 inches
out, or 25 inches out for the extended wing. Cut outside the notch on the trailing edge. The
extended wing trailing edge is already the correct length.
29. Position trailing edge and lower spar over plans.
30. Position ribs R2 – R7 (R2 – R8 for extended wing) on lower spar and trailing edge. Note that you
are not gluing the center rib (R1) on now.
31. When everything is aligned, glue ribs in place with thin CA.
32. Use rib gauge as shown to angle R1 inward. This creates the proper wing angle between the
center wings. (Fig 10)
33. Position top spar (1/8”x1/4”) across R1 – R7 (R8 for extended wing), mark length, cut, and glue
with thin CA. Cut the spar so that the cut matches the angle of the center rib.
34. Position 1/8” leading edge dowel from R1 – R7 (R8 for extended wing), mark, cut, and glue with
thick CA. The 1/8” dowel commonly has some warp to it. It is not necessary to remove the warp
but it is a good idea to orient the bow horizontally, not vertically
35. Cut to length and glue with thin CA the 6 1/32” balsa spar webbing between R1 and R5. (Fig.11)
36. Glue the five ¾” triangle braces in place with thick CA
37. Sand the ends of the leading edge, trailing edge, and spars so that they are flush with ribs. (Fig 11)
38. Make other half of wing following the previous steps.
Completing the wing
39. Glue wing halves together using thick CA. Rather than concern yourself with the angle of the two
halves, ensure that the halves meet flush and that you have a good glue bond.
40. Glue the 7” strips of carbon fiber tape to the top and bottom spars where they join using thin CA.
The CA must flow under the entire length of the carbon tape. Use wax paper to hold tape down.
Fig 13.
41. To prevent the outer ribs from bowing in when you cover the wings, glue a piece of 1/8” x 1/4"
balsa from the trailing edge to the spar webbing and another from the spar webbing to the leading
edge. Fig 14

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42. Set aside for covering later.
Fuselage Assembly
1. Lightly sand the carbon fiber fuselage tube to remove any coating so that the CA will stick to it
better.
2. Bend the 1/16” music wire landing gear as follows:
2a. Bend the 1/16” music wire in half.
2b. Measure back ¾” from bend and make the second 90 deg bends, angling out slightly from
each other.
2c. Create the final bend for the wheels 6” from previous bend insuring that the legs are the same
length.
Fig 15.
3. Attach landing gear 2” back from end of the carbon fiber tube. Wrap the gear and fuselage with
Kevlar thread then apply a few drops of thin CA till the threads are soaked. Save some thread for
the tail skid. Fig 16.
Two inches back from front of fuselage tube.

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4. Glue motor mount to top of fuselage with thick CA. The motor mount should be flat on the
fuselage and level with the work surface, side to side, when the landing gear is resting on the work
surface.
Fig 17.
5. Glue wing mount to fuselage with thick CA. Front of wing mount is 3.75” from front of fuselage
measured from where the wing mount touches the fuselage. The wing mount should be
perpendicular to the work surface when the landing gear is resting on the work surface.
Fig 18.
6. Glue the servo mount to bottom of the fuselage with thick CA. The back of servo mount is 1”
forward of back of wing mount. The servo mount should be parallel to the work surface when the
landing gear is resting on the work surface.
Fig 19.
Photo shows underside of fuselage. Note rubber band holding servos in place.

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7. Bend the tail skid out of a 3½” piece of the thin music wire using the plans as a guide. Note that
you start by bending the wire back on itself to form a ½” long loop. Attach the tail skid to the
fuselage 3” from back of fuselage. Wrap with Kevlar thread and glue with thin CA.
Fig 20. Fig 21.
8. Glue the 5”x3/4”x1/16” plywood battery holder under wing mount with thick CA.
9. Attach Velcro to the plywood battery holder.
Fig 22.
Battery mount showing rubber band backup.
10. Slide wheels over axle and retain with 3/16” long heat shrink tubing. Heat the tubing then set with
a drop of thin CA, taking care to not get any CA on the wheels.
Fig 23.
Heat Shrink Wheel Retainer

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Covering The Tail
1. Sand the vertical stabilizer, horizontal stabilizer, rudder, and elevator smooth and round edges
(except bottom of vertical stabilizer where it will be glued to the fuselage).
2. Sand bevel between vertical stabilizer and rudder, and horizontal stabilizer and elevator.
Fig 24.
3. On a flat table, lay a sheet of covering over the surface being covered leaving at least an inch
around all edges. The glossy side of the wrap should be away from the surface being covered. The
frosted side contains a heat activated adhesive.
4. With a hobby iron, tack the corners down (after tacking the first corner down, make sure the wrap
stays snug while tacking the other corners down).
Fig 25.
Note: Do not put wrap on bottom of vertical stabilizer. This area will be glued to fuselage.
5. Slide the iron along all edges to glue the covering down.

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6. Flip the surface over so that the covering is under the surface and trim the wrap with NEW Xacto
blade leaving 1/8” excess.
7. Tack the excess wrap down with the hobby iron.
8. Cover the other side the same way.
9. Once both sides have been covered, tighten the covering by passing the iron over the middle of the
covering. Go slowly and try not to over-shrink the covering.
10. Check for warps induced by the covering being shrunk. If a surface is warped, heat the covering
while gently bending the surface the opposite direction from the warp.
11. Once all the tail surfaces are covered, we will apply the hinges. I have had excellent results using
Scotch Tape as a hinge. Position the two surfaces being hinged so that there is a slight gap
(~.010”) between them, bevels facing down. Apply the scotch tape to the top side only, being
careful to maintain the gap between the surfaces. Ensure the control surfaces move freely.
Fig 26.
Tape Bevel
12. Cut slots for control horns as per the drawing and glue control horns in place with thick CA.
13. You can now apply a light misting of paint if you like. Take care to not use too much paint. Paint
is quite heavy.
14. Carefully remove a 1/8” wide strip of covering off the top of the horizontal stabilizer so that the
glue will adhere to the balsa, not the covering. Glue the stabilizer to fuselage using thick CA. The
horizontal stabilizer should be parallel to the work surface when the landing gear is resting on the
work surface.
15. Glue the vertical stabilizer to the top of the fuselage tube using thick CA. The vertical stabilizer
should be perpendicular to the horizontal stabilizer.
Fig 27.
Coffee cup not included in kit

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Wing Covering
1. Lightly sand the trailing edge, end ribs, the rib at the polydihedral break if applicable, and the
center ribs.
2. We will cover one section at a time so if you built the dihedral wing, you will have a total of four
sections – two top and two bottom. When you are covering a section that is adjacent to a section
that has already been covered, allow the covering to overlap the other section around 1/8” to give
the new covering something to adhere to.
3. Lay the wing on your workbench right side up.
4. Cut off a sheet of covering for the area you are about to cover.
5. Tack down the covering at the four corners then work along the width, tacking the edges down.
Work along the leading and trailing edge pulling the wrap snug as you tack it in place.
Note: At the polydihedral breaks and at the center of the wing, the wrap will be trying to pull up and
away from the ribs so be sure to do a good job adhering them.
6. Cover all the sections before shrinking the covering.
7. When the covering is all glued down, pass the iron over the covering to shrink it. Go slowly to
reduce the amount of warp.
8. Once the covering is reasonably tight, check for warps and remove them by gently twisting the
wing opposite the direction of the warp while heating the covering.
9. When the wing is straight you can apply a light misting of paint if you like. Again, take care to not
apply too much paint to keep the weight down.
Final Assembly
1. Make up the pushrod assemblies by bending the thin piano wire according to the plans. You will
need two Z bends and two locking L bends. Slip a piece of ½” long heat shrink tubing over the
locking L shaped wire before bending. When the ends are made, attach them to the carbon fiber
pushrods with the heat shrink tubing. Carefully heat the tubing to shrink it over the pushrod.
Fig 28.
ZEnd LockingLEnd
2. Insert two servos into the servo mounts and ensure that the control arms are centered. Wrap a
rubber band or two around the servos to retain them. See fig. 19. Insert the Z ends of the
pushrods into the tail control horns and the locking L bends into the servo control arms. Use the
center holes in all control arms. Adjust the length of the push rods by sliding the wire in or out of
the pushrods until the tail control surfaces are even. Carefully secure the wires in position with a

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drop of thin CA. Ensure that the locking arm is in place – opposite the L bend. See fig 19. You
can choose to pull the pushrods in to the fuselage using the black wire tie. Adjust the length of the
pushrods after pulling them in to the fuselage and don’t tighten the wire tie to the point where the
pushrods bind against the fuselage. The rudder travel should be around 2 ¾” to 3” and the elevator
should be 1 ½” to 1 ¾”.
Fig 29.
3. Rubber band a 3/16”x5/16” breakaway stick to the motor mount leaving 1 ¼” in front of the
mount. Use at least two rubber bands. Slide the GWS motor over the breakaway stick. If it isn’t a
tight fit, you will shortly have a glider. The breakaway stick has been designed to break before the
motor does in the event of a hard landing. Carry extra breakaway sticks with you when you fly.
Fig 30.
4. Install receiver and speed control. The receiver is velcroed directly in front of the servos on to the
battery mount and the speed controller is light enough to be suspended by its wires. Wire the
speed control and servos to the receiver. Rudder servo goes to channel one, elevator servo to
channel two, and speed control to channel three. Run the receiver antenna up and over the top of
the vertical stabilizer.

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Flying
Attach the wing to the wing mount with around 5 rubber bands. Check that none of the control surfaces
are binding and that everything, including the battery, is secure.
Before you fly the DuskStik, check that the control surfaces move the correct directions. Always check
the directions while you are behind the airplane. I highly recommend that you check the control surfaces
before EVERY takeoff. I know for a fact that the DuskStik flies fairly well without elevator control from
when I accidentally knocked off the control rod and failed to notice it.
The center of gravity (CG) should be directly under to ¼” behind the wing spar. With the battery
installed, place a finger on each side of the fuselage just behind the spar and lift the DuskStik. It should
balance there. If not, adjust the battery forward or backwards till the CG is correct.
You may want to shim that back of the balsa motor mount to give the motor some down thrust and twist
the motor sideways to give it some right thrust.
Adjust your radio trim so that the rudder is straight back and the elevator is level.
For your first flight, be patient and wait for a calm day. Choose a large field where you have a smooth
surface to use as a runway. Set the plane down pointing away from you. I would say to point it into the
wind but it’s a calm day, right? If everything goes well, applying full power will result in a short rollout
and a rapid climb with little to no need to trim the plane. Initiate turns slowly till you get used to the way
the DuskStik flies. I hope you have as much fun flying your DuskStik as I have flying mine.