If it is straight cord wings then it is still easy to estimate a good starting point for the CG which for most airplanes I prefer 25% MAC of the collective cord. Collective is a a key word and an important technique for doing the estimate for biplanes.

Folks are bringing me airplanes at the field all the time for a quick estimates and its not that hard to estimate a biplane/triplane or more. This is not some computer program but a simple method that works well for me and you can make your own decision, I,ve even received unpleasant Pm's in the past for suggesting something that was not a computer program so if your interested I will elaborate further after I return from the field this morning.

What I believe Gray Beard was getting at is the name of the airplane is not really important but what is will be the configuration. So here are the questions:

Is one or both of the wings swept?

Are the wings staggered, if so how much and is it positive or negative stagger.?

Is the wing straight cord?

Or are one or both wings tapered?


A shorter lower wing is usually not a problem when using the 'collective or projected Planform' estimate. Actually biplanes are simple but what I have had the most trouble with are canards and in one case a straight cord flying wing "flying plank".

John