Balancing Biplanes (From the May 2011 issue of Electric Flight Magazine)
From the Recent Electric Flight Top 10 Biplanes Article, this online article includes diagrams for balancing biplanes.
(Above) the Pitts Special is a common aerobatic biplane and it has a swept back top wing. The illustration below shows how to find the MAC and thus your 25 and 33 percent MAC locations for the CG range.
(Above) The Albatross D.III is a prime example of a plane with larger top wing than its lower wing. The Illustration below, shows the side view illustration for finding the model’s Center of Lift (CL). Placing the CG forward or aft of the CL effects the model’s performance.
The Illustration Below shows the quick and easy way to balance a biplane with two equal upper and lower wing chords
These techniques for finding the center of lift and the MAC and CG locations for Biplanes have worked on several different models. They are meant to get you into the ballpark so you can perform a safe and controllable test flight. After you fly your model, you can make fine adjustments to dial in the balance point that you are most comfortable with.
Don’t let this happen to your multi-wing airplane. Proper balance is the most important thing for safe RC flights.