Buzzard Droppings July 2009

By Ron Swift

Balance—that is an important part of setting up our models for flight.  It is not obvious to many new to the hobby, but the CG marked on the plans and the measurement in the instructions is an initial starting point. It must be adjusted based on the flying characteristics.  Also important is balancing the model laterally—side-to-side.  This will help prevent the model from dropping a wing as the model slows down for those touch and goes as well as the actual landing.

There are some really good tools available to assist in checking the balance points.  The best way to move the balance points is by shifting the battery and other components around.  Lighter or heavier parts can be used like a bigger or smaller battery or engine. As a last resort, weights can be added to move these balance points.

If you inherit a model and don’t know where the CG should be set, a good starting place is 25-30 percent of the main wing chord measured from the front of the wing.  If the wing is tapered and not a rectangle, there are calculators available free on the internet to provide the starting point,

If the model is highly sensitive to control movements—the model is likely on the tail heavy side.  If it is sluggish—it is likely nose heavy.

The model in the photo was field balanced for it’s new maiden flight using a Higley Heavy Hub and a rubber banded Crescent Wrench—it flew great with some minor trim of the control surfaces, but would have flown lots better if the engine could have been mounted further out, battery moved to the firewall, without the drag and extra weight of the stuff used to balance it.