Bmathews, no offense taken. Based on your many posts, I have great respect for your aeronautical knowledge. I don’t think we are very far apart, but are looking at the question with different goals in mind.

A free flight model, whether powered or glider has unique requirements that often result in unique solutions. The flight profile involves a drastic launch (power or tow) followed by a minimum sink rate glide. The transition from extreme power to gentle glide without benefit of any control from the pilot has resulted in all sort of aerodynamic gyrations in an attempt to achieve satisfactory flight. High dihedral angles, polyhedral, limited pitch stability, pylon mounted wings, “lifting” tails, ad infinitum, are all means of achieving some control during the high power climb and the transition to glide. An aircraft with significant pitch stability tends to be “loopy” with sharp pitch changes with power. This and the fact that with the cg near the neutral point, there is a slight improvement in sink rate, dictate that sort of balance for endurance type models. However it was not uncommon for these aircraft to make contest winning flights in still air but to become erratic and unpredictable if there were significant turbulence.

When I first started in radio control, we simply added a rudder escapement to an existing free flight model and didn’t touch it until the top of the climb and the engine had quit. It was then used it to keep the model in the area until it glided to the ground, eliminating the necessity of following it cross country (at least when the radio worked). If the goal is to reproduce this kind of old time flight profile, your comments are right on the mark.

The fact is that if we had had a way to control the elevator and rudder most of the aerodynamic gimmicks would not have been required. As we begun to fly R/C (rudder only, escapement) the airplanes begun to change dramatically. The pylon disappeared, dihedral was flattened, cg was moved forward, and most of all, the flight profile was changed to a gentle climb with a long engine run, and a glide to a landing somewhere in the vicinity of the launch area. The much better flight characteristics resulting from these changes are just as valid today as they were then.

If one wants to authentically reproduce an old timer free flight airplane and add radio control, the pre- WW-2 models designed before limited engine runs were introduced are the best choice. My ‘Miss America” is an exact replica of the 1936 nationals winner, except it is scaled down to fit an OS 10 engine. It has several hundred flights and even won a SAM radio assisted free flight contest (because I was the only contestant to enter that category).

I built the Berkley Brigadier as per the plans except I left off the polyhedral and moved the cg slightly forward. After several dozen flights, I cut the wing and reduced the dihedral to that shown in the photo, as turn entries were pretty jerky. I take off, throttle back and watch it slowly climb and circle above with the sunlight shining through the doped silk and think about all the models I’ve chased over hill and dale in years past. Sometimes I make a few swoops and dives that I could only imagine doing in the old days. If the goal of building an antique free flight and adapting to R/C is to capture some of the nostalgia of bygone days, without all the headaches we went through, I think my approach works quite well.

Back to the original question concerning incidence, granted the wing incidence and resulting decalage set the trim point (for a given cg location). However incidence has no direct effect on stability. It gives an indication of stability because a forward cg (stable) requires more decalage to balance at the trim speed than a more rearward cg (less stable). The reason I said it is not relevant to R/C models is that as soon as the pilot changes the trim, he in effect changes the decalage. Regardless at what angle the horizontal stabilizer is physically mounted, the actual decalage is changed by the trim. If the incidence of the wing is changed, and everything else stays the same, the pilot must adjust the trim to balance the aircraft and the effective decalage is right back where it was originally. The only difference will be the pitch angle of the fuselage.

(Now regarding driverm391's comment regarding stability, sometimes what a person means by stability is not necessarily the same as what an engineer means. To many, an aircraft is considered stable if it is easily controlled and doesn't require a lot of control input. It may or may not be stable in an engineering sense.)