Tall Paul,
Nice wee aeroplane. A homebuild I assume?

We can find the Aerodynamic Centre of a wing or pair of wings but no way can we discuss CG without knowing details about the tail. I know nothing about this aircraft's tail, so how about adding a tail and discussing the CG of my hypothetical 100% staggered biplane which you also drew and I have tried to upload here.[img][/img]

To sumarise, we have two identical wings, each 4" chord, section does not matter but I drew approx Clark Y, with 4" normal stagger, and a tail whose area is 15% of the total wing area and whose c/4 is 15" aft of the datum (LE of top wing). Let's say for completeness that the wingspan is 26".

Where would the CG go according to the method proposed and used by Tall Paul and others?

Too far aft I would suspect, unless a second error compensates for the first.

Alasdair

Hey, the image upload worked, thanks again!