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Build Log - Pixie 20" Electric Flying Wing

Old 09-07-2010, 09:30 PM
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Default Build Log - Pixie 20" Electric Flying Wing

This build thread is intended to be an all inclusive ”how to” for building the Pixie 20" Symmetrical flying electric wing. As my intention is to present this as if this were a person's first scratch or kit build, some of the information may be too basic for some in the beginning. I will attempt to present as many techniques and approaches as necessary to build the plane well, but invite other ideas also. Enjoy!


Pixie


The Pixie flying wing has been designed to be a fun aircraft that is inexpensive, exceptionally durable, great flying and easy to transport. The use of inexpensive components embedded within the 20” symmetrical EPP wing makes the Pixie the perfect choice for recreational flying, small course pylon racing, or full on combat. The comprehensive, photograph rich, construction thread covers all aspects of the assembly and setup process so that even inexperienced builders can successfully construct the Pixie with good results. Particular attention was given to durable, low drag construction that places the servos completely inside the wing and shields the push rods and control horns from wind drag and damage. The high lift, low drag airfoil provides predictable flight characteristics over a wide range of speeds and wind conditions, while accepting large control deflection for maximum aerobatics with minimum drag.

Specs :

Wing : 20” 1.3# EPP
Airfoil : Symmetrical CG3S
Typical AUW : 5.5-6.0oz
Wing Area : 110 sq.in
Wing Loading : 7.2-7.9oz/sq.ft

[media]http://www.youtube.com/watch?v=_cXnqRRwC1A[/media]
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Old 09-07-2010, 09:31 PM
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Kit Contents :

EPP wing cores
beveled balsa elevons ( 2 )
carbon fiber flat spar stock ( 24” stick )
carbon fiber push rods ( 2 )
Z-bent wire push rod ends ( 2 of .020” size, 2 of .032” size )
micro control horns ( 2 )
corrugated plastic for winglets
push rod sleeve material ( 1 straw )
Mylar sheet component cover ( 1 )
scrap EPP cleaning block ( 1 )
foam blank for CG and lateral balancer. ( 1 )
Template sheet for winglets and deflection reference marks ( 1 page )

Additional Tools & Materials Required/Suggested for building the Pixie per manual :

Glues, Tapes & Adhesives :

3M Super77 Spray Glue
Goop ( Household variety is fine )
Low temperature hot melt glue stick and low temperature glue gun
3M Scotch Extreme Bi-Directional fiberglass packing tape ( about 36” worth needed )
2-3 Rolls of light wight colored packing tape for covering ( this will cover a LOT of Pixies )
5-6 Minute epoxy
30 Minute epoxy
Blenderm hinge or bandaging tape ( Bi-Di can be substituted, but it will make plane heavier in the end )Nail polish
Medium or thin CA glue
Low tack masking tape
Double Sided tape ( or hot melt glue ) for testing the CG

Tools and Equipment :

Safety glasses
Steel ruler ( various sizes )
Fine tip markers and pencil
#11 razor knife and extra blades
Scissors
Wire cutters
Needle nose pliers
Channel lock pliers
Wire lead crimping tool and ends ( if resizing the servo leads )
Various clamps
Various small metal files
Drill and 1/16” drill bit
Electric rotary tool with flat stone bit and router base ( if available )
Small Phillips head screwdriver ( for servo arm )
Solder iron and electrical solder
Butane torch ( or flame ) and lighter
Straight pins
Large T-Pin
Ψ7/16” O D Brass tube ( for cutting motor mount )
Ψ9/32” O D Brass tube ( local hardware store )
Covering iron
Small plastic card ( such as credit card ) for applying the tape
Deflection meter
Dial or digital calipers ( nice but not necessary )
Electronic scale ( if available )
Timer
Square blocks and book ends ( during gluing )
Various weights ( soft preferred )

Consumable Supplies :

Scrap balsa ( 3/32” flat, 1/2” triangle )
Lead shot or BBs ( for CG correction )
Micro-balloons ( preferred ) or talcum powder
A few coins ( to determine balance weight )
Small stack of paper
Sandwich bag ( 1 )
Small nuts ( 2 ) ( slightly smaller than the side of servos )
Small board or book
Index card ( 1 )
120 Grit sandpaper
Brillo pad
Mixing cups and stir/application sticks
Light weight spackle ( as desired )
Paper towels or rags
Rubbing alcohol
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Old 09-07-2010, 09:33 PM
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Prepping the Wings :

Materials Required : Wing block, scrap foam ( if desired )

Gently separate the wing cores by starting at the leading edge and running your fingers between the wings and husks. Proceed slowly across the span toward the trailing edge with each pass to release any adhesion between the foam pieces. In order to prevent tearing, be particularity careful as you approach the trailing edges of the wings as they become thinner and more fragile. Remove any foam whiskers that remain from the cutting process from the wings and the inner surface of the outer husks by using your fingers and/or a scrap piece of foam. The outer husks need to be clean as they will be used in the building process repeatedly.

[media]http://www.youtube.com/watch?v=qmcpW8iQ6aQ[/media]
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Old 09-07-2010, 09:34 PM
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Joining the Wings :

Materials Required :
Wing panels, 3M Super 77 Spray Glue, 120 grit sand paper, marker, timer

Confirm that the spar locations are marked and visible on the bottom of each wing root and tip to serve as a reference for locating the spar in later steps. Spray a moderate coat of 3M Supper 77 spray glue onto each wing root, allow to dry for 6 minutes, then carefully tack the wing halves together. Once satisfied with the alignment of the wings relative to each other, press the two panels together firmly to finalize the joining. Sand any alignment imperfections along the seam with 120 grit sandpaper after the glue has fully dried and lost its tack.
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Old 09-07-2010, 09:35 PM
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Components Required :
( 2 ) 5g micro servos
( 1 ) “end pin” park flyer receiver
( 1 ) 6-10A ESC
( 1+ ) 1000mAh 2S ( 7.4V ) Lipo battery ( approx. 61g )
( 1 ) 12mm inrunner brushless motor
( 1+ ) GWS 3X2 propeller

Note : The Pixie was designed, built, and tested with the following gear : Keep in mind, this particular approach was to keep the cost to a minimum, not build the ultimate performer. Most likely, there are better components that can produce an even more responsive and exciting plane. Going "cheap" on equipment is not recommended and high performance alternatives will be researched. Any suggestions in this area are welcome.

HXT500 5g / .8kg / .10sec Micro Servo ( decent and inexpensive , but some midpoint “drift”.
Spektrum AR6110e RX (small, light, inexpensive, 2.4GHz )
TURNIGY Plush 10amp 9gram Speed Controller ( With the Pixie pulling less than 5A, this ESC may be overkill, but has been a solid performer. In some cases, the amp draw of the system is too low for the low voltage shut-off function to work correctly. For this reason, it is suggested to calculate the flight time for each setup. Soft start/stop settings suggested. Long term durability of this item is currently in question.)
Turnigy 1000mAh 2S 20C Lipo Pack ( Performs great, but consider a faster charging equivalent for convenience. )
Turnigy 1230 12mm Brushless Inrunner Motor 4500kv ( Great performance value. Only compatible with the 2S Lipo and the 3X2 prop due to overheating potential. Alternative motors should be close in weight for CG and total weight considerations. )

Substitution of alternative components may improve performance, or not, but is entirely the responsibility of the Builder. The above components were chosen on the basis of costs and availability. Keep in mind that weight and CG can change very quickly on a plane as small as the Pixie. A heavier motor and/or battery combination may quickly increase the wing loading to an unacceptable level when balanced. Efforts should be taken to keep the All-Up-Weight as low as possible for best performance.
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Old 09-07-2010, 09:36 PM
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Component Layout :

Place each component upon one surface of the wing, which will be referred as the “top” of the wing from this point on. As the wing airfoil is symmetrical, it makes no difference which side you start with. Trace around each component with a fine tip marker while making any necessary allowances for wiring and connectors. Start with the largest battery you may consider for the plane so as to leave adequate space for later modification. Place the elevon servos so that the center of the servo arm will be 3 inches from the center of the wing with the corner of the servo case 1/2” from the leading edge. The servo arm and lead should be positioned aft ( toward the tail of the plane ). Mark the location of the motor last, placing it in the center of the wing root behind the other components while allowing enough space for the wiring and connectors.
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Old 09-07-2010, 09:38 PM
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Creating the Component Pockets/Recesses :

With the gear locations marked on the top of the wing, lay the plane in the two husks so as to support the wings firmly on a flat surface. Using a rotary tool in a router attachment with a flat stone bit , if available, route a cavity for each component just barely deeper than the item being fit so it will fit below the contour of the airfoil. This is particularly important for the servos as they will be “potted” in a future step, which will consume a minor, but present, amount of height. Begin with the smallest components first so as not to route away the router base support which would make the process more challenging. ( Note : If you do not have access to a rotary tool router, you can mark the item depth on the stone bit with a piece of tape and lay a piece of paper over the wing to serve as a depth guide for freehand routing. If using a razor knife, mark depth on the blade and cut the perimeter first, then carefully remove the foam in the pocket with pliers. For a smoother floor, it can be melted smooth with a hot knife by hand. ) Repeat this pocket routing process for each component except the motor and confirm proper fit making each component just below flush with the upper surface of the airfoil. The placement of the motor should allow approximately 1/4” air gap forward of the motor and the aft end of the motor canister should extend beyond the trailing edge of the foam about 1/4” as well for cooling and clearance purposes. It will be necessary to cut full thickness through the wing in the location of each servo arm, as the servo arm is directed down into the wing and the push rod connections will be made from the bottom side of the wing later.

[media]http://www.youtube.com/watch?v=2TfEtYV-XnY[/media]
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Old 09-07-2010, 09:39 PM
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Creating the Prop Clearance Cutout :

Materials Required : Ruler, marker, wing, wing bed, elevons

Draw a line along each wing to mark the trailing edge of the foam in the motor region. ( Remember, the motor needs to stick out 1/4” beyond the trailing edge of the foam for cooling purposes. ) Using the elevons along each trailing edge, place the wide end of each elevon 1/8” in from the the tip of the airfoil and mark the location and angle for cutting the foam to the prop clearance trailing edge. Cut the prop clearance pocket from the wing and wing bed at this time. ( The bed needs to be notched as well to assist in cutting the motor mount pocket later. ) Check for proper clearances.
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Old 09-07-2010, 09:40 PM
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Making the Motor Mount Cutter :

The motor will be mounted into a cylindrical recess centered in the trailing edge of the wing. This pocket is easiest cut by using a thin walled tube. The outside diameter ( OD ) of this tube should be slightly smaller than the OD of the motor so as to provide a friction fit of the motor into the EPP foam. Cut small notches to serrate the edge of the tube to help with the cutting process and bevel the inside of the tube as needed to sharpen the edge as you would a chisel.
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Old 09-07-2010, 09:42 PM
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Cutting the Motor Mount Pocket :

Materials Required : Ruler, marker, squared blocks, masking tape, weights, motor mount cutting tube from previous step, stack of paper, motor ( for test fit )

Place the wing firmly in the beds on a flat surface with the center line of the wing along a straight line marked on the table or paper underneath. Mark the center of the wing and motor location, height-wise, and measure the distance down to the table. Take a tube approximately 1mm smaller in OD than the OD of the motor case, which will be used as a hole cutter for the motor mount, and subtract its radius from the same value of the wing center. This value represents how high the cutting tube needs to be shimmed up off of the table to center the motor pocket into the center of the wing straight and level. ( In practice, the motor doesn't need to be perfectly centered, just straight and level relative to the center line of the wing halves and cord line. )

Lay the cutting tube along the center line behind the plane and shim up the entire length of the tube with a stack of paper equal to the calculated height performed earlier to bring the center of the cutting tube to the same level as the center of the wing at the trailing edge. Secure the tube into position between a couple pair of squares, blocks, or brackets to keep things in place and apply some weight onto the cutting tube as well to keep it down against the paper shim. A couple of weighted bags will keep the tube down yet allow it to turn during the cutting procedure. Slowly rotate the cutting tube while feeding it into the trailing edge of the foam at the center of the wing. The tube will slowly cut a cylinder out of the foam wing as you progress and push a plug into the tube. You should be able to perform the entire cut in one plunge. Cut the tube to the mark of the most forward portion of the motor canister, not up into the air space. We will cut this in later so as to keep the motor from being able to ride up into the extra space. With the #11 razor knife, cut the leading edge of the foam plug core to free it from the wing without ripping. Remove the plug from the cutting tube and discard. Test fit the motor into the mount pocket. It should have a mildly snug friction fit yet be adjustable for centering.

Bevel the trailing edge of the motor cutout pocket to the center line from top and bottom.

[media]http://www.youtube.com/watch?v=7RvxaI_dot4[/media]
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Old 09-07-2010, 09:43 PM
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Fitting the Spars :

Materials Required : Wing, wing bed, weights, ruler, spar stock ( Carbon Fiber Strip .019” x .118” x 24” / .5mm x 3mm x 610mm ), fine tip marker, straight pins, razor knife with old #11 blade, flame ( heat source )

Place the wing, bottom side up, into the beds and weight it down to force the wing straight. Since the Pixie is symmetrical, the beds will properly support and align the wing. Close to the tips, insert two ( 2 ) pins into the foam at the spar mark on either side of the carbon fiber ribbon spar with the narrow edge of the spar facing up to hold the spar in place. Repeat on the other wing. Bend the spar forward along the center until the spar is tangent to a line 1” behind the leading edge and pin in place along the length of the spar. ( Note : If using different radio gear, the bend of the spar may need to be altered to place the center in a location of sufficient foam depth.) Mark along one edge of the spar with a pen onto the wings to record position in case the spar is removed before the spar channel is cut. The spar shouldn't run to the very tip and should stop 3/4” shy at each tip, thus the spar channel will also be a little less than the full wingspan. The remaining flat carbon is to be used as the secondary spar, which is placed centered 1/4” forward o f the motor.

Rather than just cutting a slot to push the carbon fiber ribbon spar into the wing, which would deform the airfoil slightly, foam will be removed to allow space to accept the spar material using an old #11 razor blade. By heating the blade momentarily, the application of the blade into the EPP foam will melt a small portion of foam away which will create the spar channel needed. The channel needs to be only deep enough to allow the spar to be fully recessed below the airfoil surface, but no more. With the spar pinned in place upon the wing, momentarily heat the #11 blade in a flame and guide it along the bent carbon fiber spar along either the forward or aft side. Only cut a few inches at a time and turn the blade slightly to widen the path a little. Do not get the blade excessively hot during the cutting and practice on a piece of scrap to get a feel for how fast the foam will melt. Continue along the path of the spar, bypassing the location of the pins, then reposition the pins and complete the path. Press the carbon ribbon into the slot to test the fit, then cut to length.

The remaining piece of the carbon fiber ribbon spar material will serve as a secondary spar which is positioned just forward of the cooling vent of the motor ( i.e. 1/4” forward of the motor ), also along the bottom of the wing. The length is relatively arbitrary, so just use what you have left over from the spar stock and center it from side to side. Cut the spar slot the same way as with the main spar to allow full burial.

Gluing the Spars in Place :

Materials Required : Wing, wing beds, weights, spar material, Goop and applicator ( toothpick ), low temp hot melt glue and gun, light weight spackle and sand paper ( as desired )

With the wings pressed firmly into the wing beds on a flat table, confirm the fit of the spars then press a thin layer of Goop into the spar slot along the entire length. Firmly insert the spars into the slots and secure the spar in place and fill in any gaps with low temp hot melt glue. Wipe away any excess hot melt glue while still warm. This will hold things still so you can keep working while the Goop dries over the next 24 hours, but overnight drying under the pressure of weights is preferred. Repeat this procedure for the shorter aft section spar/doubler as well. Light weight spackle can be applied to fill in any voids in the foam along the spar to smooth things over, sanding as needed.

[media]http://www.youtube.com/watch?v=OHknMiNcmrI[/media]
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Old 09-07-2010, 09:45 PM
  #12  
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Cutting the Wiring Paths :

Materials Required : Wing, servos, receiver, battery, ESC, razor knife with old blade, flame

Due to the the fact that the Pixie's size makes it a thin wing, most of the wire routing will need to be run just below the surface level. Decision Time : To decrease the final weight of the plane and minimize the difficulty of fitting a lot of gear in a very small space, it can be advantageous to re-size the servo leads, ESC leads, and even solder the motor to the ESC directly. The extra wire and connectors, if left in place, can become challenging to run otherwise, but not impossible. Creating wire paths and pockets may be done by several methods such as routing with a rotary tool or burning with a hot knife. Remove just enough foam to allow each component to reside below the foam surface while providing access to critical areas such as the receiver plugs, battery, and power connection. Once satisfied with the component placement and access, each item ( except battery, which should remain removable ) can be tacked in place with a small drop of low temp hot melt glue.

Potting the Servos :

Materials Required : Servos, scissors, plastic sandwich bag, 30 minute epoxy, micro balloons, stir stick and applicator, mixing cup, 2 small blocks or nuts slightly smaller than the size of the servo case, a board, weights

Potting the servos into the EPP foam allows a more rigid attachment that will stay tight over time and help prevent development of slop in the controls. Place the servos, with servo arms removed, into the pockets routed in the earlier steps to confirm proper fit. Cut two ( 2 ) small, single layered squares out of the sandwich bag about twice the size of the servos and set aside. These bag pieces will serve as a release film in the next step which will allow the removal of the servos after potting. Mix a relatively small quantity of 30 minute epoxy in your mixing cup and add the micro-balloons ( talcum powder can also be used, with varying results ) until it forms a moderately thick paste about the consistency of peanut butter . The epoxy needs to be pretty thick for potting to work well. ( Note : The addition of the micro-balloons to reach this consistency drastically shortens the pot life of the epoxy, making it necessary to work faster. For this reason, 5 minute epoxy is not suggested when potting servos in this manner. ) Apply a generous layer of splooge ( epoxy and micro-balloons ) into main area of each servo pocket where the case of the servo will rest into the foam. Do not place too close to the spline region as it will just need to be removed later. Make sure to apply a good layer of splooge at the servo tabs, but leave a little space dry at the area where the servo lead exits the case for give on the wiring. With each servo pocket layered with the splooge mixture, lay the small squares of sandwich bag over the servo pocket and firmly press the servos down into the pocket, trapping the bag between the foam and the servo. This will keep the servo from being epoxied in place. Position the small wooden blocks or nuts onto the case of each servo and then place the board across both blocks. This will force the weight onto the servos and ensure they seat firmly into the foam without deforming the foam around it. Apply a little weight onto the top of the board to press the servos in to the foam pockets and allow to cure at least an hour. ( Note : While the micro-balloons tend to speed up the exothermic reaction and pot life of the splooge mixture, it also seems to lengthen the final cure rate a bit, so be patient here. Let the epoxy fully cure before proceeding. ) After fully cured, remover the weights, board, nuts and gently remove the servos from the wing. Remove the plastic bag to reveal a form fit hardened pocket in which your servos will “pop” into place and not shift around. Clean up any excess dried splooge with a razor knife and/or rotary tool with the flat stone bit used for routing the pockets.

[media]http://www.youtube.com/watch?v=2_xllyUMedk[/media]
[media]http://www.youtube.com/watch?v=zgHZ7qH-pBA[/media]
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Old 09-07-2010, 09:47 PM
  #13  
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Path of the Push Rods :

The servos are positioned with the arms pointing down into the wing to minimize air drag as well as add a degree of durability to the plane. Without excessive push rod material and servo arms hanging out in the air, there is less stuff to get snagged in contact situations. The push rod jig is designed to line up the two ends of the push rods at the servo arm and the control, while letting the bulk of the distance to be traveled within the wing, where it is protected. The measurements are based on the servo arm being 3” off center and 1 1/8” aft of leading edge, as discussed when locating the servos earlier. Slight deviations from the 3” mark will be relatively insignificant in the final outcome of the push rod path, as it is a little over sized to allow some leeway. The control horns will be placed upon the top of the elevons and the servo arms will be concealed while facing down into the wing upon final installation.

Making the Elevon Push Rod Tunnel Jig :

Materials Required :
9/32” brass tube, scrap 3/32” balsa, 1/2” triangular balsa stock, thin or medium cyanoacrylate glue, stick pin

Prepare the 9/32” brass tube to cut through the foam in the same manner as with the motor mount cutting tube in previous steps. This diameter tube has been chosen to accommodate the push rod shields installed later.

The elevon tunnel cutting jig is constructed from scrap 3/32” balsa sheeting and 1/2” triangle stock. Cut three ( 3 ) small wedges, two ( 2 ) larger wedges, two ( 2 ) 1” long pieces of triangle stock, and one ( 1 ) rectangular top piece to the dimensions shown in the pictures. Make note of the orientation of each piece, as they can start to look the same. Place the 3 smaller wedges together side by side and attach the larger triangle pieces on either side while all pieces are flat on the workbench and flush along the rear edge. It is useful to insert a pin through all five ( 5 ) wedges to keep them in alignment while gluing with thin cyanoacrylate glue. After these pieces are dry, remove the pin and glue the two ( 2 ) triangular blocks to either side of the assembly. Attach the rectangular stock upon the top in order to create a tunnel in which the 9/32” brass cutting tube will pass through during the cutting process. Some of the wood may swell during the gluing process, so use the cutting tube to adjust the final fit inside the jig as needed. Mark the center of the leading and trailing edges of the jig for alignment purposes when in use.
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Old 09-07-2010, 09:48 PM
  #14  
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Cutting the Elevon Push Rod Tunnels :

Materials Required :
Marker, ruler, 9/32” brass cutting tube, tunnel cutting jig, wing, wing bed, weights

Mark a line upon the top of the wing 3 1/16” from the center that is parallel to the center line of the plane. This line should be 1/16” further out from the previous line you drew that represented the center of the servo arm. ( Note : The center of the push rod path should be offset a little due to the lateral shift of the push rod that will occur with the use of the Z-Bend that will attach the push rod to the servo arm. Position the offset further out the wing to place the control horn further into the aileron where it will be a little stronger. ) With the wing firmly weighted in the wing bed, place the tunnel jig upon the top of the wing with the front and rear center marks aligned with the line 3 1/16” from the center of the plane and flush with the trailing edge of the wing. Using the 9/32” brass cutting tube, slowly cut the push rod tunnels until the cutter just enters the aft edge of the servo arm pocket. Do not proceed any further forward into the wing. Back the tube out of the wing and jig then remove the foam plug to reveal the elevon tunnel. Repeat with the other wing.
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Old 09-07-2010, 09:49 PM
  #15  
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Reinforcing the Leading Edge :

Materials Required :
Wing, Elevons, Bi-Directional fiberglass packing tape, razor knife, plastic card or scrap piece of plastic, 3M Super 77 spray adhesive, timer

Lightly mist the top and bottom leading edges of both wings, as well as top trailing edges ( for the upcoming elevon attachment ), with 3M Super 77 spray adhesive and set aside to dry for 10 minutes. Go ahead and mist the top surface of the elevons as well for the next step to save on glue and time. Meanwhile, cut a piece of 2” wide bi-direction fiberglass packing tape ( Bi-Di ) 13” long and then split it so you end up with two 1” X 13” pieces. Center one of the pieces of tape at the tip of one of the leading edges and tack it along the leading edge toward the nose and around toward the other tip. Cut the Bi-Di at a slight angle near the nose along the top and bottom, then carefully fold the edges of the tape onto the top and bottom of the wing using a credit card or similar flat stock to help prevent wrinkles. Repeat along the other wing. The tip sections will overlap slightly at the nose adding strength where needed.
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Old 09-07-2010, 09:51 PM
  #16  
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Attaching the Elevons : Considerations

The elevons can be attached with hinge tape ( 3M Blenderm ) tape, or the Bi-Directional fiberglass packing tape you already have on hand. Both work well. The Bi-Di provided a very strong hinge than will not stretch, but it is a little more stiff and heavier than the hinge tape.

Inspect and mark the elevons before attaching them to avoid confusion. The larger end of the elevons will go toward the wing tips and the bevel of the elevon leading edge open along the bottom of the hinge line. In other words, the top side of the elevon is a little larger then the bottom side. Remember this when taping the elevons in place, as they will be installed with the plane placed on the table upside down.

Attaching the Elevons : The Process

Materials Required :
Wing, soft weights, Hinge or Bi-Di tape, both elevons, razor knife, 3”x 5” index card

The top surface of the elevons and trailing edge of the wings were sprayed in the previous step with 3M Super 77 Spray Adhesive and has now been dry at least 10 minutes. ( If this is not the case, perform this step. ) Apply a strip of 1” wide tape across the top of the leading edge of one wing so that only about half of the tape is adhered to the foam. Flip the wing over and weigh it down in place so that the trailing edge is pressed flat into the table. Place the index card on edge and against the trailing edge of the foam to act as a spacer along the hinge line. Align the small end of the elevon even with the inner edge of the wing while placing the elevon against the index card with the bevel opening facing up. Carefully press the elevon down onto the tape to adhere it. Trim off any overhanging tape at each end, then repeat for the other elevon. Check for an even gap along the hinge line and adequate deflection.
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Old 09-07-2010, 09:52 PM
  #17  
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Balancing the Propeller :

Materials Required : Propeller, razor knife, large T-pin, sandpaper, clear preferred, small clamp

( Note : These little propellers can be significantly out of balance. Imbalanced propellers have been proven to increase vibration wear on the motors and increased amp draw, which results in decreased flight times and power output while increasing the motor temperature and airframe stress. Skipping this step can have detrimental effects on the overall performance and longevity of any aircraft. )

Clamp the T-pin to the edge of a table so that the propeller has enough clearance to turn freely. Clean any flashing or rough edges from the propeller with the razor knife and then place it onto the T-pin hanging over the edge of the table. An ideally balanced propeller will stop horizontally after spinning. If one blade is heavier, it will be the one pointed down. The Pixie runs the propeller as a pusher, so make any changes on the back of the blades ( the side without the embossed writing ). First, try sanding the backside of the heavy blade to lighten it. In many cases, it may be difficult to safely remove enough material for proper balancing, so apply a thin coat of clear nail polish to the tip of the lighter blade. Allow the nail polish to fully dry before rechecking the balance as evaporation will change the final weight. Apply another light coat or sand off any excess nail polish after it has fully dried to achieve a balanced position.

Mounting the Propeller to the Motor :


Materials Required :
Motor, Propeller, channel lock pliers

The propeller and motor wires will be in line with each other and horizontal to the wing. Final positioning is adjusted during the actual motor installation. The motor spins relatively freely, but will ultimately come to rest in one of two positions, which are 180 degrees apart from each other. Spin the motor shaft slowly by hand until you feel it hang and stop in between the magnets. This is the position in which the motor is more apt to stop on a slow glide or landing approach. At this point, gently press the GWS 3x2 propeller onto the 2mm motor shaft, with the channel locks opened wide, so that the motor wires and propeller are in line with each other.. Make sure that the embossed writing on the propeller will be facing the front of the plane. It does not take excessive force to get the propeller onto the shaft and no reaming or drilling of the hole is needed. Try to position the pliers so that the force is directed upon both ends of the motor shaft, and not the motor case, to avoid pressure on the motor bearings and/or bushings. The propeller will bottom out on the shaft a little short thus leaving the required clearance between the propeller and the motor.
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Old 09-07-2010, 09:53 PM
  #18  
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Installing the Servos, Receiver, ESC, and Motor :

Materials Required : Servos ( with servo arms removed ), receiver, ESC, battery, Bi-Di fiberglass tape, Goop, low temperature hot melt glue and gun, rubbing alcohol, Brillo pad or fine sandpaper

Note : It is a good idea at this time to hook up all the radio gear and make sure everything is working correctly. Confirm that the motor is turning the propeller in the correct direction and directing the thrust rearward. After rough fitting of the components, it it advantageous to shorten the wires on the servos, ESC, and motor to avoid complications of dealing with excessive amounts of wiring and unnecessary weight. The motor leads are best soldered to the ESC wiring, but connectors may be used at the expense of size and weight. Confirm that the motor is turning clockwise when viewed from behind and that all three wires from the motor to ESC are of the same length.

Install the receiver and ESC in place using the low temperature hot melt glue. Very little will be needed for the receiver, but the ESC may require a more generous application due to wire control and irregular contours. Slide the motor in place while confirming proper fit. Snap the elevon servos into their respective pockets and secure with a tiny drop of hot glue as well. Run and connect all wires and secure in place with hot glue only as needed. Further protect and secure the components with Bi-Di fiberglass tape.

The motor is to be mounted with Goop into the wing. Since the Pixie uses a 2S battery, the motor does not get hot enough to degrade the bond of the Goop. Carefully pry the motor out of the pocket and pull it gently aside enough to expose the inner surfaces of the motor pocket. Scuff the outer case of the motor with a Brillo pad or fine sandpaper and then clean it with rubbing alcohol. Apply a generous layer of Goop to the inner surface of the motor pocket, then slide the motor back in place. Pulling the foam apart slightly will allow the motor to pop in place without as much Goop displacement. Be careful to avoid getting the Goop into the ends of the motor and blocking the cooling vents. Clean up around the edges of the motor and confirm that it is sitting straight and level in the motor pocket with the propeller even with the trailing edge. Once satisfied with the position, set the plane aside with motor pointing up to dry. Allow at least a couple hours of set time before proceeding.
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Old 09-07-2010, 09:54 PM
  #19  
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Push Rods ( Part 1 ) :

Materials Required : The wing, .040” carbon fiber rod, .032” music wire, small and medium heat shrink tubing, flame or heat source, thin or medium CA glue, servo arms and set screws, small screw driver, needle nose pliers, scrap wire, paper towel, transmitter and receiver battery ( to center the servos )

Since the servo arms are concealed within the wing of the Pixie, the push rods and servo arms will need to be in place before the color tape is applied for the smoothest finish. The control horn end of the push rod will be finished in a later step when setting the control throws and push rod sleeve. A Z-bend should be created one one end of .032” music wire, leaving about 1” of the section straight. Slip two very short pieces of small heat shrink tubing onto each carbon fiber push rod and around the wire push rods so that they extend beyond the carbon rod enough to engage the servo arm without binding. Shrink the small pieces of tubing in place to secure the union, confirm the alignment, then apply some CA glue at the junction of the wire to the carbon fiber rod. After about 30”, wick away any excess glue with a piece of paper towel, then set aside to allow it to fully dry. Slide the larger diameter shrink tubing over the junction area and shrink it as well to lock every thing in place and smooth over any sharp edges. Repeat for the other push rod.
Confirm that both elevon servos are trimmed and centered, then insert the Z-bend into the 3rd hole of the servo arm ( approximately 5/16” from the center of the arm ). Slide the servo arm/push rod assembly into the wing from the bottom so that it runs within the push rod tunnel and exits above the elevon. Push the servo arm onto the servo with the arm pointing straight down, or as close as possible. To secure the arm to the servo, plunge a short hole through the wing with a hot wire so that the screwdriver can access the set screw. It is easiest to hold the set screw in place with a pair of small needle nose pliers and then screw it into place. Repeat for the other elevon servo.
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Old 09-07-2010, 09:55 PM
  #20  
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The Component Cover & Color Taping the Wing :

Materials Required : Bi-Di fiberglass packing tape, Mylar component cover, colored packing tapes ( as desired ), masking tape, #11 razor knife, small scissors, 3M Super77 Spray glue, flat plastic card stock ( such as a credit card ), covering heat iron, timer

Note : The Pixie uses a thin Mylar sheet as the component cover to allow easy battery and plug access. In use, the cover is merely taped down with colored tape. The Mylar component cover was chosen as the lightest and most stream lined method for when in flight, but other options may prove more convenient for some. Colored packing tape has thus far proven to be the cheapest, easiest and lightest option for covering the Pixie, but other methods and materials may prove just as valid.

The Component Cover : Cut the Mylar into a shield that will cover all of the radio gear while leaving the motor vents open. Apply a piece of Bi-Di fiberglass packing tape along one side of the cover so it creates a flap that opens into the battery and component bay. Make sure you choose the side that will allow you the easiest access to the battery and wire leads.

Taping the Wing :
Mask off the motor, prop, push rod materials and all of the radio components as best possible then mist the entire plane with a moderate coat of 3M Super77 spray glue. Allow the glue to dry about 10 minutes, then remove all masking tape. The spray glue will add a significant amount of adhesion for the colored tape since the EPP foam is fairly porous. Cover the plane with the lightest colored tapes first and begin at the rear of the plane, progressing forward when possible. Overlap each piece about 1/4” to ensure a good seal. Since there are no fuel concerns with an electric setup, this step is slightly less critical, but it will align the seams so that the wind will not peel the tape off in flight. Cover all surfaces, except the wing tips, as they need to be left bare for gluing on the winglets later. Avoid loose seams along the leading edges as they tend to peel back over time. While it will shrink a little with heat, apply the colored tape as smoothly as possible. The use of a plastic card works well as a squeegee to lay down the tape with minimal creases and wrinkles. Once completely covered with the colored packing tape, run a moderately warm covering iron over the entire plane to activate the adhesive better and smooth out minor wrinkles.
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Old 09-07-2010, 09:56 PM
  #21  
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Attaching the Winglets :

Materials Required :
Wing, winglets, Goop adhesive, low temperature hot melt glue and gun, pencil, straight edge, large T-pin, lighter, butane torch, paper towel, rubbing alcohol, weights, blocks, and bookends

Using a pencil or water based pen, draw a straight line along the center of each winglet. Place the winglets upon the wing tip flush with the leading edge and centered at the trailing edge. Draw the profile of the airfoil upon the winglet as a reference to where the Goop will need to be placed for gluing to the wing. “Flash” the production oils from the Coroplast by quickly passing a hot flame from the butane torch along the area to be glued. In proper lighting a change in appearance can be seen as the oil rises from the surface. Do not move the flame along the winglet too slowly or you can melt or deform the plastic. Clean any remaining oils with a paper towel and rubbing alcohol. Using a large T-pin, poke an airfoil shaped array of holes through the flashed skin of each winglet to allow the Goop to penetrate into the Coroplast for better grip. These holes should only pass through the one side of the winglet. Apply a moderate layer of Goop to both the wing tips and winglets ( within the airfoil outline ) and let dry about 3-4 minutes. Carefully press the winglets in place, centered on the wing and even with the tip, place the wing on a couple riser blocks to elevate it off the table ( and keep it level ), then press and clamp the bookends against the winglets and to the wing tips. Allow to dry several hours before proceeding for best results. After the Goop has dried and the winglets are firmly in place, apply a small fillet of low temperature hot melt glue along the seams connecting the wing to the winglets.
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Old 09-07-2010, 09:58 PM
  #22  
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Preparing the Push Rods and Elevons :

Materials Required : Wing, Wing beds, control horns, straight edge, #11 razor knife, scissors, index cards, weights, blocks to raise the plane off of the table, drink straw, hand drill with 1/16” drill bit, marker, sand paper, dial calipers ( optional )

Cut about 1/4” off each end of the wing bed to allow clearance for the winglets during the setup procedure. Place the wing upright in the bed and position it elevated off the table to allow clearance of the motor, winglets and deflected elevons. Cut off all but the lowest hole on the two elevon control horns and sand smooth. Locate the small .020” sections of music wire and make a Z-bends on one end if not already prepared. The remaining section of wire should be about 3/4” long. Test fit the music wire Z-bends to the elevon control horns.

Cut away any excess tape at the push rod tunnel exits on the top of the wing until they are clear. The push rods and control horns will be covered and protected by the installation of shields made from a drinking straw and tape. This will also help to reduce the drag of the plane and minimize damage to the control horns during mishaps. Cut the drinking straw at about 45 degrees in the middle of the straw and insert them into the push rod tunnels on the wing and over the carbon fiber push rods. Begin cutting the straws at the square end so that when in place, with the long edges of the angle overhanging to the hinge lines, the straws have an additional 1/2” inserted into the tunnels. Much more than this will cause problems during the final installation.

With the straw sleeves temporarily in place, center the carbon fiber push rods inside the straws and mark this location at the hinge line. The control horns will need to be offset 1/16” to allow proper alignment once the bent wires are glued to the carbon push rods. It is preferred to place the control horns further out the wing where they will be closer to the center of each elevon and where they are a little stronger. Mark the position of the the control horns, drill a 1/16” pilot hole through each elevon, and remove the tiny squares of tape necessary to allow the control horns to be glued to the wood of the elevons, not the tape ( not shown ).

To adjust and set the position of the elevons, shim them up with a stack of index cards or something similar that can be adjusted and fine tuned. The resting position of the elevons should be directly parallel to the straight center lines drawn on the inner side of each elevon from earlier steps. Secure the elevons in place with a little weight before proceeding.
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Old 09-07-2010, 09:59 PM
  #23  
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Attaching the Push Rods ( Part 2 ) :

Materials Required :
Wings, control horns, 6 minute epoxy, .020” Z-bend wires, small diameter shrink tubing, larger diameter shrink tubing, flame or heat source and flat shield, medium CA glue, low temperature hot melt glue and glue gun, needle nose pliers

Note : The control surfaces of the Pixie are not adjustable after final assembly in order to minimize weight and drag. Any fine tuning will be achieved via the radio trims. Prior to beginning this step make sure the aileron trim is set to center and the elevator trim has 2 “clicks” of down set in it. This is done so that when the push rods are glued in place and the trims are restored to neutral, the Pixie will have the equivalent of 2 “clicks” of reflex set into the wing.

Push the drinking straw into the push rod tunnel as far as it can go to get it out of the way. Cut a section of the larger diameter heat shrink tubing long enough to cover the projected overlap of the wire and the carbon fiber push rod. Then slide it over the carbon rod and down into the straw to get it out of the way. Place a little piece of tape over the push rod closest to the straw, then slide on two very short sections of small diameter shrink tubing over the music wire and carbon push rod. Slide the short pieces of small shrink tubing near each end of the overlap and shrink in place while using something to shield the foam from the heat during this process. This will hold the push rod connection in place but allow for some adjustment. Next, glue the control horn into the elevon with 6 minute epoxy while making sure the alignment of the horn matches to the push rods. Remove any tape from under the control horn to allow attachment directly to the wood of the elevon. After the epoxy has cured, confirm that the servo and elevon is still in position, then lock the .020” music wire to the carbon fiber push rod with medium CA. After the CA has fully set, remove the tape from the push rod, retrieve the larger diameter shrink tubing that was pushed down into the straw with a pair of needle nose pliers, slip it over the wire/carbon junction and shrink it in place to help secure the connection. Pull the drinking straw out of the push rod tunnel until the peak of the bevel reaches over the control horn and secure in place with hot melt glue at the contact points where it enters the EPP foam wing. Make sure the push rod is centered in the straw to allow clean movement. Cover the straw push rod sleeve with some colored packing tape ( or your covering of choice ) to blend it in and reduce drag pockets. Repeat this entire process for the other elevon, then return the radio trims back to neutral for the elevator.
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Old 09-07-2010, 10:00 PM
  #24  
Blue Note
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Setting the Control Throws : ( Measured at the Wing Tips )

Note : Throws may be measured with deflection meter or by reference marks on the winglets ( see template )

Ailerons : High Rates : 1/2” up, 1/2” down
Low Rates : 1/4” up, 1/4” down

Elevator : High Rates : 5/16” up, 5/16” down
Low Rates : 1/4” up, 1/4” down

Control throw rates are expected to be different from person to person and should be tested out on low rates initially. The Pixie has a lot of elevator authority, so be light on the stick until you get a feel for the flight characteristics. Ailerons can tolerate about as much throw as your servos can provide without binding.
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Old 09-07-2010, 10:02 PM
  #25  
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Center of Gravity and Lateral Balance :

Materials Required : Wing, battery, a few pennies, masking tape, double sided tape, ink pen, scale, lead shot, Goop adhesive, mixing cup and stick, Pixie foam balancer block, ( 2 ) #11 razor blades, razor knife, low temperature hot melt glue and gun

Preparing the Balancer :
Locate the piece of 1/2” thick foam and draw a straight line down the length along the center. From the center of the line, place the two #11 razor blades point down into the foam even with the line so that they are 3” apart from each other. The Pixie will be balanced upon the back edges of these blades. While static balance is unlikely on such a sensitive balancer, the speed and direction of tilt will indicate the balance of the plane. Attempt to balance the Pixie so that it tilts very slowly forward when released from a level position.

Secure the Pixie balancer near the edge of a table with double sided tape to allow clearance of the winglets when in position. Place a strip of 3/4” wide masking tape along the center line of the bottom surface of the wing and two pieces perpendicular to that centered at 3 3/8” from the very nose of the wing. Draw the mid-line and CG line upon the tape to mark the balance locations. Install the battery into the Pixie and position it as it would be in flight. Place the wing upon the back ends of the two razor blades of the CG balancer directly on the line and even side to side. If the tail of the plane drops first, then some weight needs to be added to the nose of the plane, which is more likely than the need for tail weight.

Directly in front of the center of the battery, place enough pennies onto the outside of the wing to achieve CG balance. Remove the pennies and weigh them to determine how much lead is needed in front of the battery to balance the plane. Measure out about 10 grams less than an equivalent amount of lead shot in a small disposable cup. The difference in weight will be replaced by glue during the installation process. Remove the battery from the plane and begin removing some of the EPP foam in the center of the wing just in front of the battery. Test the size of the hole by filling it with the dry lead shot. The pocket for the lead should be about 1/8” deeper than needed for all of the shot to fit. Once satisfied with the pocket for the lead, mix a small amount of Goop ( small marble sized drop ) into the lead shot then pack all of it into the nose of the plane. Cut a small piece of EPP foam to form a plug for the pocket that will also serve as a cushion to keep the lead from pushing directly into the battery upon a nose impact. Seal the EPP pocket cap in place with a bit of low temperature hot melt glue. The Pixie should now balance out correctly once the Goop fully dries.

With the CG now set, place the Pixie upon the balancer with the center line resting upon both razor blades. Check lateral balance and adjust with a piece of colored tape at the very tip if one side drops quickly. A slow drop is acceptable.
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