AH1”W” COBRA - Approach Engineering

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AH1”W” COBRA - Approach Engineering
AH1”W” COBRA
DESIGNED FOR THE SWIFT 16
APPROACH ENGINEERING
WWW.APPROACHENGINEERING.COM
APPROACH ENGINEERING
1.0 Purpose
To establish a process that ensures control and standardization in the manufacturing of AH-1W Cobra for use with Swift 16
electric mechanics.
2.0 Tools Required
Note: (A) denotes tools required for assembly and
(T) denotes tools required for testing.
Basic Hand Tools
(A, T)
Sanding block and paper (A)
Dremel Tool
(A)
Epoxy 30 Minute
(A)
Cyanoacratulate (CA)
(A)
3.0 Reference Documents
Exploded View Plans for AH-1W Cobra
(A, T)
4.0 Attachments
5.0 Introduction
1.
WARNING This aircraft is not a toy. It is capable of serious bodily harm and property damage. Every precaution
must be taken to properly build this kit and install all radio components. It is your responsibility alone to ensure all
safety steps are taken outlined in the Academy of Model Aeronautics safety codes. If this is your first time building a
aircraft kit it is highly recommended that you find experienced help for the first flights. Consult your local hobby shop
or write to the AMA for further guidance.
Academy of Model Aeronautics
5151E. Memorial Drive
Muncie, IN 47302 (800) 435-9262
2.
Please inspect all parts before building. If any parts are broken or missing please feel free to call or write for replacement. All instruction manual photos are included with the CD along with other scale documentation pictures to ease in
finishing. If a step or photo appears unclear to you inspect the CD for additional photos with different views to aid in
assembly If you have any questions, comments, or improvements please call or write to:
Approach Engineering
Ridgecrest, Ca. 93555
www.approachengineering.com
3.
We as the kit manufacturer can provide you with assistance and a top quality kit and instruction manual. When built
light, straight, and true you will have a model that flies as well as it looks on the ground. However the finished product
depends on the quality built into it. We can not guarantee the flight performance. Take your time and read all instructions carefully before and during construction.
4.
During the assembly procedure the use of the term CA refers to thin CA glue and CA+ refers to medium viscosity glue.
AH-1W COBRA—ELECTRIC
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6.0 FUSELAGE ASSEMBLY
6.1 Locate fuselage side pieces S1, S2 and S3. Glue these
together to make a left and right fuselage side. Add triangle
stock as shown.
6.2 NOTE: before beginning, read through to step 6.4 and
determine which assembly procedure you will use. Punch out
the two FB1 side doublers and glue in place, taking care to align
the bulkhead slots. On both sides, add the forward ply doublers
FPD as shown, notch forward.
triangle stock
NOTE: alternate
procedure listed
below in 6.4
6.3 Install and glue bulkheads F3, F4 and F5 onto FB2 and
FB3, then glue and insert into a fuselage side, ensuring that all
the pieces are aligned and straight. Install the hardwood chassis
mount blocks to the inside of bulkheads F4 and F5. Install the
second fuselage side.
6.4 An alternate method is to assemble the fuselage center as a
box. Fit the F3, F4 and F5 bulkheads to the deck pieces FB2 and
FB3. Attach sides FB1, then glue each side to it’s proper fuselage side. Add chassis support blocks before final glue.
NOTE:
alternate
procedure
Hardwood blocks
Below plywood
6.5 Temporarily position your mechanics in the enclosed
Fuselage and mark mounting points on the mechanics mounts.
6.6 Drill holes in the mechanics mounts on the marked positions with a 9/64” drill bit. Press in the four 4-40 blind nuts on
the bottom side of the mechanics mounts.
This picture is for reference only—
some parts are removed for clarity
This picture is for reference
only—some parts are
removed for clarity
AH-1W COBRA—ELECTRIC
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6.0 FUSELAGE ASSEMBLY
6.7 Turn the fuselage over and add the 1/4” square corner
stock as shown. Epoxy in the forward landing gear support
block, and the rear gear doublers making sure that the holes
align with the holes in the fuselage sides. Then glue the 1/4”
Ply Doublers over that 1/8th inch Ply to strengthen the
landing gear supports. Make sure to align the holes.
6.8 Now install 3/32” cross-grain sheeting from bulkhead F3
to bulkhead F4. The sheeting should only cover half of F4, leaving a ledge for the next bottom skin sheet, BS1.
gear side doublers
1/8th Inch Ply then
Epoxy the 1/4th ply
doublers over this.
Hatch area- leave open
6.9 Find the belly skin BS1 and hatch. Glue the hatch frame
(1/8” Ply , Use 1/8th ply scrap for filler pieces) to the bottom of
the hatch, then install the magnet bases on both the frame and
the hatch. Fabricate a small catch on the front of the hatch using
scrap 3/32” material. Glue BS1 to the bottom of the fuselage. A
small UHF antenna will later be added to the hatch to pull it
open.
6.10 Begin forming the nose by adding the nose
floor sheet, NS1. Wet the nose pieces to make them
contour to the shape, while adding bulkheads F1 and
F2. The two bulkheads are tied together by the forward brace FBR. Continue with 3/32” sheeting until
the nose is complete.
NS1
6.11 Glue together the 3 upper nose blocks UNB and 3 lower
nose blocks LNB as shown. Glue them to the front of the fuselage as shown. Then glue the TSU shim TUS to the bottom of
the upper nose blocks as shown.
6.12 Assemble the four nose chin blocks NCB. Glue together
three TSU lower mounts TMT. Glue them to the front side of
bulkhead F1.
NCB
TSU shim
AH-1W COBRA—ELECTRIC
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6.0 FUSELAGE ASSEMBLY
6.13 Punch out the two 1/8” light ply vertical fin supports
VFS and two tail rotor tube supports (TSR). The rounded edge
of the tail rotor tube support faces foreword. Glue the two TSR
supports in the mid and lower slots on one side only.
6.14 Assemble the two belt idlers pulleys as shown. The
chamfered edge of the pulleys should face inward to help guide
the belt.
Bearings 2 each
TSR
Bearings
Guide Washers 2 each
6.15 Assemble each pulley idler assembly by first pushing the
1/8” shaft through the bearings. Place one bushing on each side
so that the end of the shaft is flush with both sides. Complete for
both idlers. NOTE: plastic housing ends must be drilled open to
make clearance for the shaft width, otherwise the shafts will be
too long to fit into the tail.
6.16 Place the toothed idler assembly in the lower hole and the
smooth idler in the upper hole. Take the supplied belt, not the
one with your mechanics, and place it between your idlers so
that the teeth are facing toward the toothed idler. Glue the other
vertical fin support to the tube supports. You may place a small
amount of glue on the outside of the bushings to help hold them
in place.
Note direction of teeth
Smooth Idler
Tooth Idler
6.17 Punch out the 1/8” ply tail rotor frame base (TFB).
Note: the base has a break out tab that will be removed later at
the front of the part. Do not cut at this time. Slide the vertical
fin supports into the base and glue with CA+.
AH-1W COBRA—ELECTRIC
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6.18 Glue on the 1/8” ply side pulley doublers (SPD) to the
outside of each pulley assembly by aligning the edges.
6.0 FUSELAGE ASSEMBLY
6.19 Cut out the 1/8” ply trailing edge former (TE-2) and glue
6.20 Pull out the larger diameter, longer, tail rotor tube. Using
it into the notches provided on the top of the vertical fin assembly.
30 minute epoxy glue to the vertical frame so that the bottom
edge is flush with the bottom surface of the bottom tail rotor
tube support and the vertical cuts are at the top of the fin assembly..
Bottom edges line up.
6.21 Cut out three tail rotor tube leading edge supports (TSF)
from the 1/8” ply. Using 30 minute epoxy glue to the vertical
fin supports and the tail rotor tube.
6.22
TSF
6.23
6.24 Glue the completed assembly into the notches provided
in the fuselage side. The telescoping tube fits inside this epoxied
tube, with the clamp located at the top.
Telescoping tube
clamp goes here
AH-1W COBRA—ELECTRIC
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6.0 FUSELAGE ASSEMBLY
6.25 Once the nose blocks are sanded to the proper contour,
dremel out the bottom of the nose blocks where they meet bulkhead F3. Using the existing oval hole in F3, form an air intake
for the battery compartment.
6.27 Find the cheek corner blocks CCB and glue them together into two stacks as shown. Locate and install the cheek
cowl blocks CCW, and chin cowl block CWB after taper sanding to the
proper
Cheek and chin blocks
shape.
6.26 Install the balsa canopy retainer side rails CRR.
Balsa side rails CRR
6.28 Glue together the TSU blocks and gun turret blocks
TUR. Use these assemblies to aid in placing the chin and cowl
blocks. Do not glue them into place at this time, wait until after
finish and paint, then final assembly of the gun.
TSU blocks
Corner blocks CCB
6.29 Glue together the tail blocks TBL and fit them into the
end of the tail, as shown.
tail blocks here
AH-1W COBRA—ELECTRIC
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TUR blocks
6.0 FUSELAGE ASSEMBLY
6.31 Before adding the fuselage top and bottom sheeting, install the rudder control nyrod in the fuselage. It must be routed
so it is free of binding, and does not contact the belt drive or
pulleys.
Telescoping tube and clamp
6.32 Using scrap plywood secure the nyrod away from contacting the pulleys.
scrap plywood guard for NYROD
6.33 Install the lower fuselage sheeting LFS to enclose the bottom of the fuselage.
6.34 Working from the open top of the fuselage, install nyrod
supports as required to position the nyrod so it will terminate in
line with your servo arm.
6.35 Before sheeting the top of the fuselage, clip out this forward cross brace on the tail base. This is necessary to provide
belt clearance.
6.36 Add the upper fuselage skin UFS. At this point it is
advisable to install the tail drive gearbox as well.
Add gearbox
upper skin
AH-1W COBRA—ELECTRIC
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7.0 FUSELAGE ASSEMBLY
7.1 Install a piece of 5/8” triangle stock for the vertical tail
leading edge. Make a paper template for the correct shape of
the left and right skins. Using the template cut out the sheet
stock and glue in place. Wetting the wood makes it bend easier.
7.2 Before proceeding further, adjust the tail housing height to
1 5/8” . This will provide the proper position for setting the belt
tension.
Telescoping section
clamp
1 5/8”
7.3 Canopy frame construction begins by placing the canopy
frame lower frames CLF in place on the canopy side skins CSS.
Note that the CSS has a small additional piece that goes in front.
Also test fit into your fuselage to ensure the proper curvature in
the front. Glue the mid and read
bulkheads in place as shown.
7.4 Locate the canopy side frames CSF, canopy center rails
CTR, canopy top skin CTS, canopy middle bulkhead CMB and
canopy rear bulkhead CRB. First glue the two bulkheads to the
canopy side skins CSS. . Place the canopy front bulkhead CFB
in place and glue the side frames, making sure the bulkhead is
lower than the nose so the
canopy fits flush.
CSS
7.5 Do not glue the rear of the upper frames just yet. They will
fit into the doghouse lower frame when it is installed, in a later
step.
AH-1W COBRA—ELECTRIC
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7.6 Continue the upper fuselage by gluing the transmission
lower rails to the trans side skins TSS.
7.0 FUSELAGE ASSEMBLY
7.7 Add transmission housing bulkheads TB1, TB2, TB3 and
TB4 to the trans housing skins.
7.8 Assemble the exhaust frame by punching out EXH1,
EXH2, EXH3, EXH4, EXH5, EXH6. First place EXH2 and
EXH5 between EXH 3 and 4. Then place this assembly on top
of EXH1. EXH 6 then goes on top.
6
2
4
3
1
5 angled
7.9 Glue spacer EXH9 to the back of EXH3, then install the
two EXH7 and 8 pieces to the back of EXH3. Add block
EXH10 to the rear of this assembly, then add 1/4” stock cap to
the top edge as shown.
7.10 The lower portion of the housing can be filled with some
scrap 1/4” balsa stock and sanded to the contour. Also note that
now is a good time to apply wood sealer and primer to the aft
portion of the housing, since the exhausts will cover this part
making it impossible to seal later.
9
Seal and prime
10
Filler blocks
7.11 Prepare to sheet the engine cowl sides by adding the square basswood stock as shown.
7.12 Assemble the doghouse structure by first placing the trans top skin TTS in place at the aft and.
Then place the doghouse base DHB across the trans
housing bulkheads. Glue the canopy rails in place to
the front of the doghouse base. Add DH1, 2, 3, 4 and
5.
Then add the doghouse top DHT.
DHT
1
AH-1W COBRA—ELECTRIC
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2
3
4
8.0 FUSELAGE ASSEMBLY
8.1 Make small paper templates and apply the transmission
housing sheeting using the supplied balsa sheet stock. Keep in
mind that the trans housing will be split in the middle when
complete.
8.2 Continue sheeting small sections, wetting the wood to aid
in contouring around curves.
Split line
8.3 Attach the sheeting on the intakes in sections. Keep the
wood wet and it will contour around the corners.
8.4 Sheet the doghouse with the supplied 3/32” sheeting. Once
the sheeting is applied, add the doghouse front DHF and rear
DHR blocks. Lastly add the doghouse upper caps, DHC. Sand
to the appropriate contours. The forward and rear sections of the
trans bay may now be separated from each other.
Cut here
DHC
DHF
8.5 Assemble the horizontal tails from the HTL pieces. The
light ply tail support blocks TSB are added in their notches, also
add a piece of basswood stock to the center to act as a spar.
Glue the upper and lower pieces in place, sandwiching the
center piece with the spar. Sand to an inverted airfoil shape and
install on the left and right sides.
AH-1W COBRA—ELECTRIC
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DHR
8.6 Sand to an inverted airfoil shape and install on the left and
right sides.
9.0 ENGINE AND TRANSMISSION
BAY ASSEMBLY– INTAKE AND EXHAUST
9.1
Punch out the 10 INT intake pieces, and 18 EXH pieces. Assemble the intakes 5 per side, and exhaust 9 per side. Glue in place and
sand to shape.
9.2 The intakes, exhausts and the exhaust center frame are
glued to the rear transmission housing, and stay attached to it
when the rear trans housing is removed. Glue the rare earth
magnets into the forward and rear transmission housings and
fuselage base.
9.3 The exhaust diffuser assemblies are made from supplied
card stock. Using the interior of the exhausts, roll the card stock
to conform to the inside of the exhaust, trim to fit so the overlap
is only 1/2 inch. Glue with white glue. The diffuser rings DFR
are glued to the card stock afterwards.
9.4 The diffusers will extend past the exhaust exactly 1 inch.
Allow 1/4” inch extra length so the diffuser can be glued into
the exhaust, and still protrude 1 inch. Add the stiffener pieces
EXS to the outside edge for proper appearance.
9.5 The tail rotor drive fairing is made of 1/2” square balsa,
rounded at the top. A relief hole must be made in the rear of the
exhaust frame so that it will sit down over the fairing when installed.
9.6 Assemble the gun by placing the two gun barrel supports
AH-1W COBRA—ELECTRIC
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onto the 3 dowel gun barrels. This assembly fits in to the forward slot of the turret. On the bottom of the turret, dremel out a
cooling duct that will align with the battery compartment cooling duct made earlier. Finish and detail the gun as desired.
9.0 Wing assemblies
9.7 Locate the 1/4” x 11.5” wing spar dowel. Cut it
into two 4” long pieces. This will allow 1/4” spar
insertion into the fuselage. Place a sharpie mark at
1/4” from the inside end, this is where WR1 will go.
Then punch out wing ribs WR1—WR5.
9.8 WR1—5 have a flat spot to aid in alignment.
Using the skin as a guide, space the ribs 7/8” inches
apart and glue them to the spar only, with WR1
placed at the previous line. Keep the trailing edges
aligned, not the leading edges. Be sure to make one
left, and one right side.
9.9 On each wing rib, carefully cut off the alignment tabs at
the dotted line, and apply the upper and lower wing skins WSS.
Wet the wood to aid in bending.
9.10 Add the triangle stock leading edges, and WNG outer
wing armament rack pieces. There are 2 balsa WNGs with a
plywood WNG in the middle. Add alignment tabs.
tabs
9.11 Sand the wing assemblies to final shape and glue in
place after the fuselage is finished. Add armament as desired for
a scale appearance.
AH-1W COBRA—ELECTRIC
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9.12 Now glue together the four CMM countermeasure pod
blocks, glue in place on the tail after the tail is final sanded.
9.0 FUSELAGE ASSEMBLY— VERTICAL
TAIL CAP & LANDING GEAR
9.13 Locate vertical tail cap ribs TR1 and TR2. Cut a piece of
9.14 Make a paper template for the two side skins, and using
5/8” triangle stock 1 5/8” in length. Glue the two ribs to the
leading edge, and add a piece of scrap 1/4” balsa as a corner
gusset for each rib. You can use the tail tube as a guide to keep
the ribs aligned.
that template cut out two skins out of the supplied sheet stock.
Remember to keep the grain vertical so it will contour.
9.15 Wet the two skins with warm water, and shape them to
9.16 The two halves should slide together onto the tail tube.
conform to the two ribs. Glue in place, bringing the skins together in the rear. Once the water in the sheets has dried, draw a
line on the left and the right and split the pieces in to a front
and rear section. Make 2 small screw tabs for installation.
Adjust the telescoping tail clamp and trim the lower rib slightly
so that the lower rib fits UNDER the clamp. The clamp will
then help retain the tail cap. Install 2 small screws to secure it.
Sand the trailing edge to match the trailing edge of the vertical
tail.
9.17 Lay out the 4 landing gear struts and mark each one
9.18 With the struts in the fuselage, attach the lower gear
1 3/4” from the inside end. This will mark how far to push the
struts into the fuselage. Now make another mark 3/8” further
inboard from the first mark. This is the cutoff line. Cut the struts
off at this line. When inserted into the fuselage, there will be
3/8” epoxy contact inside the fuselage.
clamps to the lower strut ends, and insert the skids. Once satisfied with the alignment, epoxy everything in place. Note, you
may want to wait to glue the gear into the fuselage until after
the fuselage is painted.
3/8”
1 3/4”
AH-1W COBRA—ELECTRIC
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clamps
9.0 ENGINE AND TRANSMISSION
BAY ASSEMBLY
9.19 Prior to installing the chassis, the top frame inside the
rear transmission housing must be removed for clearance. Remove the section marked below.
9.20 Remove the forward plastic tray from your
swift. It is not necessary in the chassis.
9.21 There is no need to use a section of tail boom
for the belt exit. Allow the belt to simply exit the
plastic belt drive housing as shown.
9.22 Cut out a section from the rear portion of the vertical tail
9.23 Trim the canopy for fit on the canopy sill.
remove the skin and bulkhead sections in the 3 x 1.5 inch area I
indicated in the picture for servo linkage clearance."
AH-1W COBRA—ELECTRIC
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cap to allow for the tail rotor bell crank clearance.
18.0 APPENDIX
9.24 The model is ready for final contour sanding and the finish method of your choice. You may apply an
elaborate detailed paint scheme, or simply cover it with any of the available colored plastic films. Add armament details as desired.
VERTICAL FIN EXPLODED VIEW
AH-1W COBRA—ELECTRIC
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18.0 APPENDIX
AH-1W COBRA—ELECTRIC
Page 17

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