All good discussion. UStik, I think you have inferred so, but I just wanted to specify that when we talk about CG of an airplane, we also should be talking about the neutral point and static margin of the entire airplane. Not just the wing. So the size of the horizontal stab and the distance from wing to tail have a great influence on the position of the Neutral Point and on the acceptable CG position. In the model world, the Goldberg Sailplane has a large stab and long tail. The Sailplane flies very well with the CG at the wing trailing edge.

In the pictures shown on the original post, the horizontal stab looks huge. I was a little surprised that the numerical data shows the stab area to be only 23% of the wing area. UStik correctly points out that the lower aspect ratio of the horizontal stab diminishes it's effectiveness somewhat. But we also have to remember that the biplane configuration diminishes the effective wing area and aspect ratio somewhat as well.

I've not found a handy online neutral point calculator for biplanes. Does anybody know of one ? That would make life simpler for us.

There is a photo on Wikipedia that is telling. Notice the angle of attack and the downward curvature of the stabilizer/elevator. That says the stab is pretty heavily loaded. And look at the two guys standing on top of the fuselage ! Either the pilot was about to lose control or the airplane tolerates a fairly aft CG. There's no record of a crash immediately after the picture was taken, so I guess the airplane remained controllable in spite of the two "pedestrians" on board.

Dick


Note, I'm not having any luck adding the photo file. If someone will lead me through the upload process I'll add the photo.