McKELLAR AERO DESIGN CF-105 Construction Manual

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CF-105

Avro Arrow

Construction Manual

McKELLAR AERO DESIGN

Wingspan: 19.17” Wing Area: 180 in² Length: 27.9” Weight: 13-14 oz Power: Speed 400 or

100-120W brushless

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Table of Contents

Introduction…………………………………….…………2 Kit contents…………………………………….………….2 Required to complete……………………….………….3 General building instructions………………...………3 Building the fin……………………………………………3 Building the wing………………………..………..…….3 Building the nose and intake nacelles…….……..5 Building the fuselage…………………….……….……7 Building the canopy and spine…………….……….10 Final assembly……………………………………………11 Prepare for flight……………………………….……….12 First flight……………………………………….…………12

Introduction

Thank you for purchasing this model kit. We have worked very hard to provide a model that is both easy to build and fly while giving spirited performance on modest power. Please read through all the instructions before you begin building so that errors can be avoided.

Kit Contents

• Eight sheets of laser cut 1/16” balsa

• Two sheets of laser cut 3/32” balsa

• One sheet of laser cut 3/16” balsa

• One sheet of laser cut 1/16” plywood

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Required to Complete

• Two lengths of 1/8” diameter carbon fibre rod (7-11/16” and 11-9/16” long)

• One package of CA hinges

• Two pre-bent pieces of 1/16” piano wire for the aileron torque rods

• Two 12” lengths of 0.032” piano wire

• Two plastic tubes

• Two 1/8” diameter by 1/8” long rare-earth magnets

• One length of 3/32” aluminum tube

• Four 2-56 X ¼” socket head cap screws

• Two Dubro Micro E/Z Connectors

• Covering

• Self-adhesive Velcro (can be found at most hardware stores)

• Medium and thin cyanoacralate (CA)

• 10 minute epoxy

• Two micro servos weighing 8-10g with 12-15 oz-in torque rating

• One micro receiver

• One speed control with BEC (battery elimination circuit) suitable for your motor.

General Building Instructions

• It is best to remove the parts from the laser cut sheets only as they are needed. This will reduce any chance of confusion since some of the smaller parts are not labelled on the actual part.

• Sand down any remainders of the tabs which held the parts in the sheet.

• Do not force any tabs into the slots. Enlarge the slots if the tabs are a bit tight. A

jewellers file or nail file works well for this.

• Be sure to check the fit of each part and assembly before applying glue.

• Use medium CA for all joints unless told otherwise.

Building the Fin

Begin by removing Appendix A from the manual and place on building board with wax paper over the sheet to protect the plan. Pin V1 in place over the plan. Glue V2 to V3 and then pin V4 in place. When everything is aligned, you can glue V4 to both V2 and V3. Now fit the remaining parts (V5, V6, V7 and V8) in position and apply med. CA to the joints. Once all the glue has cured, you can remove the fin from the building board. Lightly sand both sides so they are flat with no lumps. The leading edge and tip should be rounded over with a sanding block. Finally, the trailing edge can be sanded to a taper with a thickness of roughly 1/16” at the outer edge. Make sure this taper is even on both sides of the fin.

Building the Wing

The first step is to lay the lower wing skins in place on a flat surface and glue them together. The right wing lower skins are made from parts WR1, WR2, WR3, and WR4. The left wing lower

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skins are made from WL1, WL2, WL3 and WL4. Make sure these parts are lying flat when you

W13

WR9

WR10

LONG ROD

SHORT ROD

glue them together. Once the glue has dried, give all the joints a light sanding so they are flush.

Next, the wing ribs R1-R5 are fit in place on the lower wing skin. The tabs in the ribs fit into the slots in the skin. Once the ribs are in place and everything is flat you can glue the wing ribs to the skin with medium CA. Once the glue has cured, sand the ends of the ribs so they are flush and perpendicular to the edges of the wing skin.

The leading edge is made by laminating WR9 (WR9 on the bottom) and WR10 together for the right wing. Do the same with WL9 and WL10 for the right wing. Now glue the trailing edge (W13) and the leading edge in place. Sand the top surface of the trailing edge so it follows the profile of the wing ribs. Now, take the short length of carbon fibre rod and fit it in the forward holes through R1 and R2. The rod should protrude outward of R2 by 1/16”. Apply CA to the rod/rib joint to fix in place. Do the same thing with the longer rod and it should again protrude 1/16” outboard of R3. *NOTE* only glue the rods into one wing panel at this time. The final step is to glue the top wing skins together like was done for the bottoms skins. The upper skin for the right wing is made from WR5, WR6, WR7 and WR8. Similarly, the left skin is made from WL5, WL6, WL7 and WL8. When these are complete, you can glue the skins onto the wing panels. Make sure everything fits well before you start with the glue. First, glue the skin to the leading edge with CA. Apply aliphatic glue on the tops of the ribs and trailing edge. Apply weight (phone book works well) to the panel and leave this a few hours until it has dried. Now you can sand off any overhang and shape the leading edge. The elevons need to be sanded to shape. Take the left (WL15) and right (WR15) elevons and sand a

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taper so the top surface thins to 1/16” thick at the trailing edge. Mark the leading edge 1/2” in

N6A

N7A

N7B

N6B

N2-R

N2-L

Nose sanded to shape

from the inner end of the elevon and drill a 1/16” diameter hole 3/8” deep. Make a 1/16” slot from this hole to the inner end. This hole and slot will fit the torque rod. Mark the three hinge locations on both the wing trailing edge and the elevon leading edge. Using a hobby knife, make a slot at these locations. Finally, sand the leading edge of the elevons so a slight bevel (20°) top and bottom. See Appendix B

Building the Nose and Intake Nacelles

We will build the nose section first. Begin by gluing the formers N5, N6A, N6B, N7A, N7B and N8 in place on N1. Make sure these parts are perpendicular to N1. Next, fit the top sheeting (N3) and the bottom sheeting (N4) in place and apply CA to the joints. The right (N2-R) and left (N2-L) side sheeting can now be glued in place. Sand the sheeting edges so they are flush with the former corners. Now you can glue the corner sheeting in place. Glue one top corner sheet (N10) and one opposite bottom corner sheeting (N11) in place. Trim these parts flush with the top and side sheeting and then apply the remaining top and bottom corner sheets (N10 and N11). Sand the sheeting edges flush with one another and sand the sheeting flush with the front N8 and N5. Laminate the nose block from the four parts labelled N9 and glue in place on N5. Finally, sand the sheeting and nose cone into a nice round shape.

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The intake nacelles are

Nacelle sanded to shape

built next. Start by building the left nacelle. Glue E3 and E4 onto E1 making sure they are both perpendicular to E1. Fit E5 in place and apply glue. Now, glue the top sheet (E6) and the bottom sheet (E7) in place. The outer side sheet (E2) is glued on next. Sand the sheeting edges so they are flush with the corners of E3 and E4. Glue E8 onto the top corner and E9 on the lower corner. Carve and sand the corner sheeting to a round profile. The right nacelle is built in the same way using parts labelled D1 to D9.

Once the intake nacelles are finished it is time to mount them on the fuselage. Glue the intake nacelles into F16 on the forward end of the fuselage. The tabs will fit right in place. Blend the nacelles into the fuselage with some light sanding.

Nacelles glued onto the fuselage

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Building the Fuselage

F16

F17 F18

F19

F14

F3R

F3L

F11

F13

F9 F12

F10

The first step is to build the two center fuselage formers (F17 and F18). These are built up

from parts F17A,B,C,D and F18A,B,C,D. Assemble these parts over Appendix A and apply CA to all the joints. Lay F1 flat on the building board and fit the formers (F16, F17, F18 and F19) in place. Use a small square to keep the formers square to F1 and glue the formers to F1 with some CA. The fuselage sides (F3R and F3L) are now fit in place. Make sure all the joints are tight and then apply CA to the joints. Glue the two F14’s in place. Using a sharp hobby knife, cut the battery hatch (F4) free of F1 and set aside.

The battery opening doublers will now be installed. Now, glue F8 in position up against the forward former (F16). Next, the two F6 doublers are glued in place. Make sure these parts are pressed against F8 and the fuselage sides. Finally, F7 is glued in place. Take one of the magnets and glue it in the hole in F7. The magnet must be flush with the top side of F7. Take the part F4 that you cut from F1 and glue in place the two F9’s, F11, F12 and F13. Then fit the two F10’s in position and apply glue to the joints. Glue a 1/8” magnet in the hole in F4 making sure it is flush with the underside of F4. Make sure that the battery poles in the fuselage and battery hatch are opposite so that the hatch will close. This completes the battery hatch for now. Remove the eight F21 parts from the sheet and laminate then together is pairs. Fit these in the slots in the fuselage sides and the two F14 parts. Apply CA to the joints to fix in place. Using the carbon fibre spars or a 1/8” dowel, position P4 so the hole lines up with the forward spar hole in both

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fuselage sides. Carefully apply CA to P4 making sure the dowel or spar does not get glued in

F21 laminations

P5 P4

Epoxy fillet here

place. Do the same thing with P5 and the rear spar hole on both fuselage sides. Take the two plastic tubes and cut them so you have two lengths 8.5” long. Fit these tubes in place through the holes in the F17 and F18 formers. The forward ends of the tubes should protrude beyond F17 by 1/4”. When these tubes are positioned properly, glue in place with CA. The firewall is made by laminating P1 and P2 together. Make sure the small holes in P1 and P2 line up before gluing. Use 10 minute epoxy to glue these two parts together. Note that the photo shows blind nuts which were used on the prototype but not required for the kit. Make sure the firewall is perpendicular to the fuselage top (F1) and glue the firewall to the fuselage sides. Next, bend F1 into contact with the firewall and apply glue to the joint. Make sure the firewall has not shifted during this process.

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Cooling holes

F22

The fuselage bottom skin (F2) can now be glued in place. After the bottom skin is in place, apply a fillet of epoxy with some filler on the firewall/fuselage skin joints. This will strengthen the joint and secure the firewall very well.

The corner sheeting will now be installed. Start with the top side. Sand the edges of the fuselage sides and top sheeting on an angle so they match the angled edge of the former F19 and the firewall. Take F20 sheeting and glue it over this corner. Do this on both sides of the fuselage and then sand a radius into this edge. Do the same procedure for the bottom corners of the fuselage using F22 for the long section and F23 for shorter aft section. Cut out the two cooling holes in the lower aft fuselage skin after all the sanding is complete. This finishes up the fuselage for now.

Fuselage sanded to shape

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C12

C11

AFT Spine

FWD Spine

Canopy

Building the Canopy and Spine

Start by gluing the canopy formers (C3, C4 and C5) onto C2. Now glue the canopy base (C1) onto the bottom of C2 and the formers. Frame up the fwd spine by gluing the formers C8 and C9 onto C7 and then gluing C6 to this assembly.

Cut some balsa from sheet MAD-ARW12 and sheet both the fwd spine and the rounded section of the canopy. Bending the sheeting into shape is easier if you wet the outside with some window cleaner containing ammonia. Once this sheeting has dried fully, trim and sand the edges as well as the forward section of the canopy sheeting so that you can apply flat sheeting to the forward area. Sheet one side of the fwd canopy and then sand the sheeting edge flush with the opposite face. Apply sheeting to the remaining face and sand everything flush. The rear spine is laminated from the two C11 and C12 parts. Now, trim and sand this part so it blends in with the rear end of the fwd spine and the fin.

AFT Spine sanded to shape

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Final assembly

1”

Covering removed to glue wing in place

Cover all the individual parts with your favourite film. Remove any covering from where the parts will be glued together. Glue the wing panel with the carbon fibre spars in place first. Now glue the second wing panel in place using a little epoxy on the carbon spars and CA on the wing rib. The nose is glued on with some CA. Glue the fwd spine in place on the battery hatch and fit the hatch in position once the glue has set. Glue the canopy on making sure it lines up with the fwd spine. Next, the fin is glued in place using epoxy in the fuselage slot and CA on the fin base.

Finally, glue the aft spine in place again making sure it lines up with the fin and fwd spine. Remove six hinges from the hinge sheet and mount them in the elevons. Press the hinges halfway into the elevon slot and apply some thin CA to the joint. Let this CA cure fully before going on to the next step. Sand the ends of the elevon torque rods with some 220 grit sandpaper and then clean these ends with alcohol or acetone. Fit the elevon torque rods through the pre-cut holes just aft of the wing trailing edge. Make sure these are installed correctly. The end inside the fuselage should be pointing down towards the belly of the plane. Tape a small piece of wax paper onto the inner trailing edge of the wing. Apply some epoxy to the torque rod hole and slot in the elevons and fit in place on the wing. When the elevon is positioned properly, apply some thin CA to the hinges so that they are locked into the wing trailing edge. Set aside until the epoxy has cured fully.

Take the aluminum tube and cut two 1” lengths from it. Now, and flatten one end of each tube with smooth jawed pliers. Drill a 1/32” hole in this flattened area making sure that the holes in both tubes are the same distance from the other end of the tube. If this distance is unequal, you will have uneven control throws on the elevons. Make a “Z” bend on one end of both 1/32” steel rods and fit the aluminum tubes on theses “Z” bends. Apply some epoxy to the end of the torque rod and inside the aluminum tube. Using the motor hole, slip the pushrods through the plastic tubes and slip the aluminum tube onto the end of the elevon torque rod. Leave the fuselage upside down while this epoxy cures. Bolt your motor to P3A or P3B and then attach that onto P1 using the supplied #2 screws .Note that P3b has no bolt holes for the motor so you can drill your own mounting holes should your selected motor not fit P3A.

NOTE: Aluminum tubes shorter than required in this photo

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Finally, install the servos and receiver and apply some sticky Velcro onto the battery tray F15 and glue it in place on the forward end of the F14 stiffeners.

Prepare for flight

Support the wing at the location shown in Appendix B and place the receiver, speed control and battery in position so that the plane balances level. You should be able to achieve this balance point by shifting the battery fore and aft. Do not fly the plane with the balance point further aft than the indicated range. A tail heavy plane is unstable and extremely difficult to fly. Set the control throws as shown in Appendix B. Use the bottom side of the wing root as the reference plane.

First flight

Be sure to do a range check before the first flight to make sure the radio is operating properly. Check once again that the control surfaces are moving in the correct direction when the transmitter sticks are moved. Apply three to four clicks of up elevator (nose up) for the first launch. Get a friend launch the plane for the first flight. Apply full power and have your friend launch the plane into the wind at a level altitude. Get a feel for the plane and try a few approaches to get ready for the landing. You will find that the plane lands at a nose high attitude and fairly slow speed. I hope you will have many enjoyable flights with this new plane!

Good flying!

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