Walt:

Apologies, sir. The twin rudder optin was not on the Twin-Air 25 plan, it was instead on the preliminary Twin-Air 15 plan. I am attaching three shots of that section of the plan. You will note it says the rudder linkage is "Left to the builder."

On the dihedral. With a "Hershey Bar" wing, you can look at the front view of the airplane, mark the center of each wing panel, and draw a line between these two points. This line roughly shows the center of lift. If the true center of gravity is below this line, the airplane has positive roll stability, If it is above this line, the airplane has negative roll stability. This is why a really good aerobatic high wing plane will have anhedral; the wings bend down rather that up. Other things will affect this also, so this method is just a rough approximation, it will get you in the ball park

For an absolutely neutral stability, all centers will be at this CG point. The thrust line, the roll center, the aerodynamic leverage of the rudder an elevastor all will be on a line through the CG. And they also will conform to the datum line of the airplane. That's why rudders are usually wider at the bottom, the Cap series is an extreme example of the rudder being biased toward neutrality. And the center of drag should also pass through the CG.

Please remember, Walt, while the Twin-Air is a really fine airplane, it is not intended to be competitive in pattern competition. It wil, however, fly the pattern, but other planes do it better.

If you want a twin that will do a really god job in pattern build the Duellist 2/40 Mk II. Please note this is not the one kitted by Pica, although the Duellist Mk I kit from Pica can be built as an almost Mk II without any great effort.

Bill.