Drexel's Home Page
Webmail
Drexel One
Google

 

Paul Briedé Jr

       

HOME

RESEARCH

TUTORIALS

RESUME

       

DREXEL SAE AIRLIFT

AVIATION

PICTURES

MISCELLANEOUS


 

Magpie AP

Background
The purpose of the Magpie AP is to serve as the test bed for the GPS waypoint navigation. This R/C aircraft was chosen for many reasons. First and foremost, the Magpie AP was designed for the added payload of a digital camera. Because of this, there was a section cut out of the fuselage where a digital camera could be placed. For this project, we needed a plane that could hold the added payload of a GPS, BS2p, and a serial servo controller. The added payload would take place of the digital camera and would all fit very well in the designated section (the camera bay). Secondly, this model was chosen because it is easy to fly. The Magpie AP does not have ailerons and relies solely on the rudder for turning. The dihedral shape of the wing allows the aircraft to be very stable in flight, thus not requiring ailerons for direction control.

The purpose of this tutorial is to show where you can purchase the Magpie AP, what resources you will need to build the R/C aircraft, and many additional steps to the assembly instructions (that come with the Magpie AP) that I learned that might help anybody else in assembling the Magpie AP.

 

 

This is a photo of the Magpie AP fully constructed before the GPS and BS2p were attached.

 
 
 
The Magpie AP and wing tape are available at http://www.mountainmodels.com
The electronics on the parts lists are available at http://www.allerc.com
 
Parts List
1 Magpie AP with 54 inch Wing
Wing Tape, 2inchs x 55 yards (white)
2 Waypoint Precision Sub Micro 6 gram Servo + Servo Extension Cables
1 GWS Pico Receiver with GWS 72FM Pico Receiver Crystal (Channel 55)
1 Castle Creations Phoenix 25 Brushless Speed Control
1 Transmitter (DASL has many)
1 GWS EPX 300 Gearbox with 66 Tooth Spur Gear and 10 Tooth Brass Pinion
1 HA2025-4200 HIMAX Brushless Motor
GWS EP1260 Propeller
1 3D Wobbly Propsaver Adapter (3mm) and extra O-Rings
1 Thunder Power 11.1V 1320 mAh Pro Lite Lithium Polymer Battery Pack
Soldering Iron with solder wire
Thin Cyanoacrylate (CA) Glue and CA Accelerator
Wax Paper
5 Minute Epoxy
Xacto Knife
Pliers and Screw Driver
Velcro
200 Grit Sandpaper
3M 77 Spray Adhesive
Masking Tape
Wire Cutters
Vise
 
Changes in Magpie AP Assembly Instructions
When building the Magpie AP, there were several steps in the instructions I though were unclear or needed to be changed. Below is a detailed list of the clarifications and changes. Please note - this is not to serve as assembly instructions for the Magpie AP. This is to serve as a guide to the assembly instructions which at some times may be unclear or vague. The number before the clarification or change signifies what number within the assembly instructions the clarification or change applies.
 
In the assembly materials section, the thin cyanoacrylate (CA) should be the type of CA that is safer to use on plastics. Also, a spray accelerator is helpful in decreasing building time. Five minute settling time turns into seconds when using a spray accelerator. The wing tape used to cover the wings and fuselage comes in a single roll. Initially, it looked as if more than one roll was needed. This is not the case because at the end of the project I still had tape leftover. The leftover tape can be used later for repairs if needed.
 
Assemble the Wing
1. Make sure the leading and trailing edges of the left and right wing halves lineup with each other. I used 5 minute epoxy to glue the sections together because it has a faster setting time and should be stronger than regular glue.
2. The spar slot is the long "caved in" section on the top and bottom surface of the wing running the length of the wing (from right to left). The vertical spar is the large V-shaped piece of wood that came with the parts. When the vertical spar is inserted, make sure it is flush with the top and bottom surfaces of the wing and no epoxy is seeping out the top or bottom section where the vertical spar was inserted. If epoxy is seeping out, when it dries it will pose a problem in the next step (step 3). 
3. The way the spar strips were packed makes them have a tendency to roll into itself. Beware of this when applying glue and securing spar strips to the airplane. Also, there are spar slots on the top and bottom of the wing. Make sure spar strips are placed on both bottom and top surfaces of the wing. The remaining spar strip material will be used later for the fuselage.
4. A very sharp xacto has a problem cutting this foam. Unless you are removing a large section of the wingtips, which is not recommended, use sandpaper to shape the wing rather than an xacto.
5. The reinforcement plates are to be glued only on the top surface of the leading and trailing edge.
 
Covering the Wing
More Tape = More Weight = Less Payload = Decreased Performance
 
Choosing a Pattern
This step was skipped. The only pattern that might be necessary or even appropriate would be the DASL logo. 
 
Applying the Covering Tape
Disregard the section explaining covering the wing in low temperature iron on covering.
 
Applying the Covering Tape
2. Do not spray too much 3M 77 adhesive because it will dissolve the foam, will not produce a "sticky" surface for the tape to adhere and also leads to the need for steps 1 and 2 to be repeated. Make sure the 3M 77 is sprayed on lightly.
4. Tape the bottom surface of the wing first for aesthetic reasons . I suggest this because whatever surface you start on will serve as your test surface. Mistakes in applying the tape are probable, and since the bottom surface is not seen as much as the top surface (when the Magpie AP is not flying ), it serves best as the surface to cover first. Also, cover the leading edge of the entire wing with one (or even two) pieces of tape running the length of the wing for protection. Make sure no tape is extending over the surfaces (leading and trailing edges, right and left side).
 
Smoothing out the Covering Tape (Optional)
The was not done on my model. Make sure if this is done, it is done to a trial surface first. Make sure the foam of the wing is not deformed due to this process because it will effect the flight characteristics of the Magpie AP.
 
Assemble the Camera Mount Base
3. Make sure blind nuts are oriented as they are in the photo. This is very important.
4. Be sure to use spray accelerator in this step.
 
Assemble the Fuselage
1. Use epoxy rather than glue or foam safe CA. Take great care to keep the fuselage straight!!!
3. The fuselage reinforcement straps are the same as the spar strips.
4. I feel this step is not needed. Skip this step.
6. Make sure front section of wing saddle (where landing gear is attached) is strongly glued. This area needs to be strong because it supports the airplane while on the ground and also it must withstand hard landings, which might happen with a beginner. When I first flew the Magpie AP, I had a hard landing on the gear which resulted the gear coming off the aircraft and removing the plate on the saddle that attaches the landing gear to the airplane (which explains why I had to hand launch the aircraft for my second flight in the video showing the Magpie AP's first day of flight gathering data from the GPS via BS2p). 
8. Do not cut through entire fuselage when cutting the servo holes.
 
Building and attaching the motor mount
This aircraft requires the stick mount.
1. Don't forget to use the accelerator.
2. Make sure the CA is not laying on the surface of the stick mount. Excess CA on the surface of the stick mount will make it hard to slide the GWS motor/gearbox over it.
 
Installing the Landing Gear
No corrections or additions were needed in this section.
 
Assemble and Install the Stabilizer, Rudder, and Elevator
5. DO NOT cut the bevel into the trailing edge of the horizontal stabilizer! Sand the trailing edge of the horizontal stabilizer to obtain the bevel. Sanding will be easier than cutting with an xacto (it will also look cleaner). 
6. The 7 3/16'' dowel is the longest wooden rod in the bag (not the metal wire). In this step, wax paper can really be helpful. Make sure the edge of the elevators face the horizontal stabilizer and is aligned and square with the surface, with slight spacing (to allow free movement).
7. Again, do not cut the bevel. Sand the bevel into the leading edge of the rudder.
10. Taping might require more than two hands. If another person is around, ask then to give you a hand.
11. I always tape both sides of moveable surfaces (like the elevators).
12. Use epoxy, not CA or glue
13. Again, an extra hand is helpful in this step.
 

 
Install the Elevator and Rudder Servos
Do not grind the gears of the servo (i.e. move them through other means rather than from a PWM signal). Make sure servo's are centered before attaching to rear fuselage.
1. Make sure the servo's are secured in the servo slots. I found mixing the epoxy in the servo holes rather than on a different surface (the surface you have been using to mix the epoxy) was easier. Make sure you do not fill the holes with too much epoxy mix. To be save, fill the servo holes just under halfway the volume of the hole. When inserting the servo's into the servo slots after slightly filling the holes with epoxy, make sure the servo arm is facing out (perpendicular to the fuselage) rather than facing up as it is shown in the picture of page 10 of the assembly instructions. The wires (red, black, and white) exiting the servo will be under the servo, inside the servo slots. Make sure the wires exit the servo slot on the side closest to the front of the plane (so the servo wires will be closer to the receiver slot).
2. The pushrods do not come with a Z bend. Make the Z bend yourself.
 

 
Installing the Wing
1. You will need to make a small cut in the tape to get to the holes in the wing mount. I did not glue the dowels because they were not loose.
 
Installing the Motor
First, attach the 10 tooth brass pinion to the motor shaft using your hands. Using your hands will snugly secure the pinion to the shaft (it is ok if the end of the shaft is not flush with the pinion yet). Next, use the vice and a piece of wood (which will be resting against the pinion so the vice does not damage the pinion) to move the pinion further back on the motor shaft. Once the two are flush with each other, use the same piece of wood and drill a hole in it a little bigger than the shaft diameter but smaller than the pinions diameter. Place the motor shaft over the hole in the piece of wood and use the vice to push the motor shaft through the pinion. Make sure the pinion is lined up with the spur gear on the GWS gearbox. Next, secure the brushless motor into the gearbox with the screws and plates given with the gearbox. Make sure the shaft of the motor is in the center of the opening and the spur gear aligns with the brass pinion.

1. Slide the GWS gearbox over the motor mount stick and slide the gearbox back as far as possible. Make sure there is epoxy or CA making a bond between these two components. Skip step 2 of Installing the Motor.

After the motor is GWS gearbox and motor are mounted on the motor mount shaft, solder the connectors given with the motor to the different color leads coming off the speed controller (black, red, and white). These are connected to the speed controller to give an easy connection to the motor (you will notice the motors already have the other portions of the connectors). After soldering is complete and there is a good connection between the wires and connectors, connect the speed controller to the motor.

 
Installing the Receiver and Speed Controller
The instructions tell where to plug the servos and speed controller into the receiver, which effects what channel they will be on. For this aircraft and receiver, I installed the servo's and speed controller the way it says in the assembly instructions. See the above picture for where to locate the speed controller (ESC).
 
Installing the Camera Cradle
Follow steps 1 and 2 for this section. Forget steps 3-8. The stamp, GPS, and serial servo controller will be connected to the camera cradle.
 
Setting the Center of Gravity
Attach the battery at the location shown in the picture below.

 
After all the above steps are complete, the Magpie AP will be ready for flight. Make sure there are good connection between anything electric and the prop is secure to the gearbox.
 
Conclusion
If the steps in the assembly instructions and this tutorial are followed, the Magpie AP can be assembled in just under a weeks time. This aircraft will later serve a purpose for GPS waypoint navigation. This is further described in my other tutorials on my webpage.