Is this method to calculate a biplane's center of gravity using 57% of the biplane's gap and 23% of each wing's MAC correct?

Once you have the MAC for both wings and the CG balance point as a percentage of the MAC. connect the two CG positions with a line. Measure up between the wing Gap distance and place your center of lift (CL) at the 57% reference line. Project this location up and balance your biplane at this postion (see red lines). A CG forward of the CL makes the model more stable. Placing it aft of the CL makes model less stable.

Source: Modelairplanenews.com

I'm trying to use this method for a Bucker Jungmeister model. The gap is 12.5 in. and the top wing MAC is 9.44 in. and the bottom wing MAC is 9.9 in. Is this the best method?

• The graphic came from Model Airplane News. modelairplanenews.com/balancing-biplanes Commented Feb 16, 2023 at 23:42
• I think that that 57% is just the average of the two MACs. If both MACs are equal (let's say 1) then the average is 0.5 i.e. 50%. If the upper MAC is bigger then the average is closer to it, otherwise the other way around. In your case it should be less than 50% since the lower MAC is bigger. Commented Feb 17, 2023 at 9:28
• I think I found the answer. It seems a little more complicated. I'm grappling with the variables and math found in this graphic on Quora I found. It's from a gentleman by the name of Krishna Kumar Subramanian. quora.com/…. The use of wing area seems similar to derive a Gap. I'll try to add the graphic somehow. I'd like to know the combined MAC value. Commented Feb 17, 2023 at 17:19
• I also found this simplified calculation method that comes from "Balancing Biplanes by Dimitrios Katsoulis" rckavalaacroteam.com/balancing-biplanes I am suspecting that both simplified methods are sourced from the more complicated formula demonstrated by Mr. Krishna Kumar Subramanian. Hopefully someone more knowledgeable will confirm this. Commented Feb 17, 2023 at 17:28
• Well I was almost right: it's the average indeed but based on the wing areas instead of the chords 😉 Commented Feb 17, 2023 at 18:57