Hey P-7 jockeys!
Does your P-7 carry some up elevator trim? Mine sure did. And so did every other P-7 that I have seen up close. Hmmm, there must be something to this.

So a couple of weeks ago, I loosened up the rear wing screws, inserted a couple of wooden "Popsicle" sticks between the wing TE and the saddle, then tightened up the screws. Totally unscientific, just kind of winging it so to speak.

I set the elevators to a neutral position using the trim, and took off. All I can say is WOW. Night and day difference. I asked Tony F to fly it, and he also concurred that it was a major improvement. After flying Tony's now deceased Phoenix, and noting how much betterthat his flew compared to mine, he graciously worked with me to dial it in. And while we got it close, there was that elusive "something" that was still not right. It looks like we found it.

When I returned home, I aligned the ailerons and elevators using to the airfoil using my calibrated MK 2 eyeballs, and took measurements with the Robart incidence meter. (Note- never trust the tips! Especially on an ARF). The resulting measurements showed that with the shims, that aircraft now has a +.25 degree wing incidence (or decalage) relative to the stabilizer. This is right about where it should be. Without the shims, the incidence was -.1 degrees.

Any negative incidence will cause weird trim issues. No amount of negative incidence is good- ever. You need a little bit of positive incidence, or the airplane will tend to "hunt" in pitch. The Zero-Zero setup is a myth. Joe Bridi got it right. Look at the plans for the Dirty Birdy, etc, there it is- positive incidence. The classics need some positive pitch stability to really fly right.

So take a look at your P-7. If it is carrying some up trim, give the shims a try. BTW, the shims that I used (and have since made permanent) are .080" thick.

Hope this all helps someone.
-Robert