Balsa RC Conversion build and fly checklist

I’ve learned a few things (as at 2021 August) as I’ve been getting back into building balsa model planes, and getting into radio control flying those same planes. This is a simple checklist for a new model, based on lots of accumulated online wisdom, and the many mistakes I’ve already made in less than a year of this excellent adventure.

  1. Check the centre of gravity. Double check it, triple check it and check it again every time you make even the slightest change to the model.
    • Err on the side of front heavy vs tail heavy. As Cliff Harvey says – a front heavy plane will fly, a tail heavy plane won’t fly.
  2. Check the horizontal balance. Make sure the plane isn’t heavier on one side or the other. Balance it with weight on the wingtips if necessary.
  3. Make sure the servo arms and control rods are moving freely and not catching on anything inside the model.
  4. When setting up your model in the transmitter:-
    1. Set up a throttle cut switch
    2. Set up failsafe
    3. Set up a flight timer. Start with about 50% of expected flight time, extend it as you learn the model.
    4. Check the controls work the right way. Reverse if necessary in ‘outputs’ (OpenTX)
    5. Check the throw on all control surfaces and use the transmitter to drop it back if necessary (by setting the “weight”).
    6. Put some low rates and expo “options” on a 3 position switch, so you can easily adjust them while flying. For example set up 20%, 30% and 40% expo depending on the switch.
      • This is just the starting point for the maiden flight. Once you figure out the correct rate and expo based on actually flying behaviour, set it as the default for the model.
    7. If you have ailerons, add a mix to add in some rudder (maybe 10-20%) with the ailerons to make turning easier.
  5. Check your connections. A loose wire can pop in flight, you don’t want that.
  6. Make sure your landing gear is solid (not loosened in the last flight?). Check the wheels are spinning freely.
  7. Check the motor is firmly attached (not loosened in the last flight?)
  8. If the wings are held on by rubber bands, make sure they hold firmly. Add more bands if necessary.
  9. If you have a tail dragger, make sure there is enough clearance so the rudder isn’t dragging. This might look fine in the hanger, but watch out for long grass that might catch or even break the rudder. Check the rudder is solid.
  10. Make sure your battery is fully charged before flying. Double check it with a battery tester.
  11. Turn on your transmitter first – make sure the right model is selected.
  12. Check all controls are working correctly. (ailerons, rudder, elevator, motor)

Enjoy!

Some other tips:

  1. Don’t sweat the small stuff. It’s the big ticket items that impact the model weight.
    • Covering, electronics, battery!
    • I saved more than 20 grams on the weight of my Guillows Sopwith Camel 801 by using small (1.7g x2 and 3.7g x 2) digital servos rather than “standard” 9g servos. I don’t think I could save 5 g by spending hours shaving off balsa from the wing ribs, trailing edges, keels and formers.
  2. Test the electronics at every step – from before they go in the plane.
  3. Build in the electronics as you go. Trying to add them in at the end, even with a well designed kit, is fraught with challenges. Continue testing as you build up the plane around the electronics.
  4. Try to add access to the electronics. You will probably need to fix or replace or check them many times.
  5. Strengthen weak points on the model using carbon fiber. Good places to look are undercarriage, wings, and where the wings connect to the fuselage. If it’s a biplane strengthen the struts, especially where they connect to the wings.
  6. Put some down thrust angle and right thrust angle (for a front mounted “puller” model) in for the motor to counteract the centrifugal force created by the motor, likely about 5% right and 5% down. This is especially important for outrunner brushless motors.
  7. Always take off the propeller when messing with anything electronic with a battery connected.

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