Testing a new theory.

I saw what is being called "Gurney flaps" in the spring. I have tried them on several of my planes with some success. Mention was finally made of them on a forum. I have found that they work on some planes and not on other designs. I have 18 planes to test with. I think the thickness of the elevators has something to do with how effective the "flaps" are. (The flaps are only 1/8 x 1/4 strips on the elevator trailing edges.) If the elevators are tapered to a point the flaps may be more effective than on a thick, 1/4 inch, elevator trailing edge. I have two Twisters with stab. and elev. made from the same, 3/16, balsa sheet. I didn't taper anything so the elevators end in a square edge. I put strips of 1/16 x 1/8 balsa on the trailing edges of the elevators and will give that a try as soon as it stops raining. The curret design philosophy is to have the stab. thicker than the elevators. Why is not up to me to know and I don't. Generally the elevators are 1/8 inch thinner than the stab. If you sand the elevators to a point the elevators are slow to react. By putting a thick piece (1/8 high) on the trailing edge that puts the flap 1/16 into the airstream at all times. There are some that are about an inch tall total but not full elevator span. Plus there is a bit of drag induced by the strips which helps keep the tail in place. Much like an arrow with no feathers vs. an arrow with feathers. The arrow with feathers will go straighter than the other one. Which brings me back to my early childhood. I was less that 10 years old helping my father make a concrete step. I was out of position, according to my father, and he told me to "get your ass behind you". If I had feathers I may have understood what he was trying to say. He did finally explain what he meant. "Turn around and face the other way". At the field with the Twister I got in a flight and the Gurney flaps didn't do much of anything on the flat plate elevators. I didn't think they would as the elevators are in the air flow at all times not like ones that are thinner than the stab. and tapered to boot.