DLE Section : Building Materials and Tools

Getting the things you need to get started.


Prepare the propeller before use

Reamer and prop balance tool

 

The driving system plays a primary role in the model aviation. The thrust force produced by the driving system is required to be as precise as possible for an effective and efficient flight. An electrical motor drives the propeller in a revolution motion; providing the propulsion thrust for the flight.

The propeller looks simple, yet it requires precision to produce and to assemble to the model. In this article, the scope is only on a nylon propeller for electric model with direct drive (without gearbox) through a propeller adapter. However, some of this technique is also applicable to other systems which implement a prop adapter.

This technique is optional and some modelers prefer to just use the propeller without any pre-preparation. Most of the propellers provided from the manufacturer are already able to fit in the prop adapter just fine, but some have hub center holes which are required to be enlarged.

There are many ways to enlarge the existing center holes of the propeller. The most precise process is to use a bench drill press, but a proper clamp has to be used for securing the propeller in place during the drilling process. There is also risk involves a propeller damage during the clamping process. Secure it too tightly; it might damage the leading or trailing edge of the propeller blade or damaging the center hub. Secure it too loose; the propeller might fly- off, hurting the people in the area (this should be prevented at all cost).

All these risks also present when you decide to use an electric hand drill. The less precise and safest way is to use manual hand reamer tool. You could just slowly rotate the reamer tool manually by hand; the tapered cone should self-feed to the centre axis of the hole. With this manual tapered hand reamer, you are free from the mentioned risks.

Prop preparation 01

Hand reamer tool                                Reaming

The deeper the reamer feed into the hole, the larger the hole is formed. Be cautious not to oversize the hole. Try to test fit the propeller to the prop adapter after a few revolution of the reaming process and repeat the process until the propeller is just-fit into the prop adapter.

Reamed prop

Another preparation process involves in balancing the propeller. The production process from the manufacturers is already precise, but there are always tolerances in the manufacturing process. Again, this is optional. A more balanced propeller would help to minimize vibration during the flight. Vibration could be small, but even a small and continuous prolong vibration will caused uneven wear on the ball-bearing of the motor; reducing the performance and the lifetime. Besides the wear and tear issue, vibration is the notorious enemy for aerial photography/videography/cinematography. The vibration results in a jelly-like video. This issue is overcome by implementing steady gimbals for the camera.

In this article, only the 2 blade-propeller is discussed. A prop balancer tool is used to show whether the propeller is balanced or not. The propeller is secured on its center by cone nuts on a shaft. For a smaller prop center hole, the cone nuts are configured in such way that the cone’s peak is facing each other. For a larger prop center hole, the one of the cone nuts is swapped for its face orientation. When the shaft is mounted on the tool, the magnets on each end will automatically hold the shaft at its centre axis.

Prop balance config

If the propeller is unbalanced, it should be heavy on one side and one of the blades will rest on the ground.

Unbalance

To balance the propeller, a strip of tapes is used. Try to mount the tape closer to the center as it will reduce the disturbance near the edge of the blade. Adjust the mount position and the amount of the tapes until the propeller is balanced and automatically rest on the center.

 

 

Tapes on prop

 

 

If you have finished with the adjustment, you may finalize it. Try not to mount around the leading and trailing edge of the blade to minimize the change in the blade’s airfoil. You may mount the tapes on both the front and back sides.

Tapes on prop 02

Balanced prop

The propeller is now ready for use.

Prepared prop 02

“Have no fear of perfection – you’ll never reach it.” ― Salvador Dalí


Here is what you need

The materials:

 

  1. The mechanical parts:

    • A4 Size papers – for printing the parts’ template from the Design Plans
    • Foam sheets (5mm thick) – the aircraft’s main frame material :
      1. Polyfoam sheets (plain white without any coating)
      2. Foam board Polystyrene (with coloured coating)
      3. Styrofoam block (bulk-head) – for plane’s nose protection (OPTIONAL)

      Foam materialFoam Closeup

     

    • Carbon tube 4 mm / 5 mm diameter – for the wing / body spar
    • Carbon rod 1 mm / 2 mm diameter – for control rod

    Carbon Spar

    • Pin horns – to connect the control surfaces to the servos
    • Pushrod connectors – to connect the servo horns / pin horns to the control rod

    DC servo

    • Electric nylon propeller with compatible prop adapter

    Propeller

    • Velcro tape / strip – to fasten the Li-Po Batt / other electronics to the plane for easy removal

    Velcro strips_tapes

    • Bolt M3 with 20 mm length with its nut and O ring – for motor mount assembly
    • Plywood / basswood with 5 mm thickness – for motor mount frame
    • Balsa wood (OPTIONAL)

    Wood

     

  1. The electronics:

    • DC Servos – for control surfaces actuators, flaps, slats, landing gears, etc
    • Servo lead extension cable; single cable and Y- cable  (OPTIONAL)

    DC servo

    • Outrunner brushless motor with compatible connector to the ESC – for the aircraft main engine

    Brushless motor

    • Brushless ESC (Electronic Speed Control) with internal BEC (Battery Eliminator Circuit) and proper connector type to the battery and connector lead to the motor

    Brushless ESC

    • Receiver with compatible transmitter( 2.4 GHz, min 4-Channel, Recommended 6-Channel and above with mixing program)

    Transmitter set

    • Li-Po (Lithium –Polymer) Battery with the compatible connector type to the ESC
    • Li-Po Battery proper charger

    Li-Po Batt

     

  2. Finishing materials: (OPTIONAL)

    • Coloured packing tape – for colour finishing process to the aircraft

    Colour packaging tape

    • Foam safe spray paint
    • Flexographic ink

    Flexo inkPaint with Flexo

    • Acrylic paint

    Acrylic paint

 

The tools:

 

  1. Marker (Fine) – for tracing the parts’ template, the fold lines, edge bevel lines, double bevel lines
  2. Stainless steel ruler – for cutting reference tool
    Marker ruler
  3. Screw driver set with various bit driver (Phillips (cross), slot (flat), hex key (Allen), hex socket)
    Screwdriver
  4. Wood coping saw – for motor mount construction
  5. Cutter / utility knife / hobby knife:
    • for trimming the border edges of printed parts’ template
    • for cutting the parts’ template paper out according to the shapes (scissors may also be used)
    • for cutting the foam sheets (complete cut, edge bevel cut and double bevel cut)
      Cutting tool
  6. Single-sided tapes:
    • for joining the printed parts’ template
    • for taping the parts’ template to the foam sheets for tracing process
    • for strengthening the fold lines, especially 90° fold ( fibre reinforced tape is used in this case)
    • for making the control surfaces hinges (fibre reinforced tape is used in this case)
    • for strengthening the all edges of the aircraft; leading edge of the wing / tail / rudder (OPTIONAL)
  7. Double-sided tapes (mounting tape) – for electronics mounting; the servos, ESC, receiver, etc
    Tapes mix
  8. Hot glue gun – for quick assembling process, for filling the gap in between the narrow holes for carbon tube spar installation.
  9. Epoxy glue – for assembling process; the aircraft’s frame, the motor mount, pin horns (much lighter than hot glue, but take a longer time for preparation (mixing) and drying process)
  10. Foam safe glue – an alternative for epoxy glue / hot glue
  11. Spray adhesive (foam-safe is recommended) – for assembling the airfoil part to the main wing/ body
    Glue Notes: be cautious when selecting spray adhesive, some will consume the foam.
    3M foam spray
  12. Abrasive sand paper (fine grit-size) – for shaping the airfoil curves; leading edge of the wing
    Sand paper
  13. Soldering iron/gun – for connecting wires process; ESC, motor, battery connectors
  14. Tin solder wires
  15. Soldering paste
  16. Heat shrink – for neat wires soldering process
  17. Hot wire foam cutter –  for cutting foam sheet with curve / round shapes (OPTIONAL)
    Soldering tool
  18. Electric drill – for motor mount holes construction
    Drill

Happy Hunting!

 

” When an artist of talent makes a painting or a sculpture, he is always aware of the potentials and limitations of his materials; the better the artist, the more likely he is to know just what he can and cannot do with them.”

            – Bruce Cole