View attachment 47282
Not sure if this explains or not
The straight lines would be your digital level
It was set to zero at the fw vertically to start.
The horizontal ref is 90 to the fw for reference.
The other 3 lines are the wing and stab measurements.
I am assuming that is the way you measured Adam to come up with numbers like that?
Your up stabilizer has a value of 2.5 which is greater than a wing value of 1.0
The elevator should be exactly in trail of the stab, at all trim settings...
The bungee cord is supposed to keep it exactly in trail, but in truth, it doesn’t seem to matter much. My bungee cord was way too long (how the heck did that happen?) when I got it, but when I replaced it with the correct part number, it didn’t change the trim at all....but, it would probably make more of a change if it was too short, and the elevator was deflected up. When it’s just hanging down, the slipstream tends to lift it into trail.
Now my head is starting to hurt again...when you trim nose down, it raises the leading edge of the stab, which loosens the bungee cord, which deflects the elevator down, in order to keep it at the same level as the stab...(rather than lowers, lets gravity take the elevator down...)
Now my head is starting to hurt again...when you trim nose down, it raises the leading edge of the stab, which loosens the bungee cord, which deflects the elevator down, in order to keep it at the same level as the stab...(rather than lowers, lets gravity take the elevator down...)
The elevator mostly stays in trail near neutral trim, at the extremes, it moves more than the stab, but it matters more when the elevator is pulled up.
I believe that the primary purpose of the bungee spring(s) is to provide resistance feedback in the elevator control. Secondarily it assists the stabilizer in pitch trim. There are specific control pressure limits to meet the certification requirements. If there was no resistance when you move the stick, it would be easy to over control the airplane (PIO) pilot induced oscillation.Small drift here - What happens to flight characteristics if no elevator bungee is installed? The bungee on my plane is weak or too long; the elevators sag, which results in the horiz stab leading edge downward (nose up trim). But it seems to fly ok? It seems I've read in threads long ago about eliminating the elevator bungee, but I'm not certain what was said.
mark I guess I thought based on the numbers that the stab angle nose down trim would be a greater number that the bottom of wing. What about longerons coming up and 3/4” gap at tail post?
Distortion from welding.Around here most all fabric planes have bowed longerons since the one shop who covers planes has never learned how not to over tighten the fabric.
Distortion from welding.
StewartSide question. How do lower longerons get bowed? Ive see tail sections get twisted and single longerons bent by impact but both longerons bowed equally is new to me. And wouldn't bowed lower longerons improve nose down trim? I don't see how that alone would hurt it.