atmosphereship wrote:So, as airspeed increases the pitch stability increases? Bar pressure is increasing? I'm trying to understand the y-axis of the graph and the measurement of "pitch-up moment".
Scott, yes the pitch stability increases with airspeed as does bar pressure. This is because the tail is canted down 5deg.
It is also mounted on the long fulcrum arm of the keel which gives it a mechanical advantage over the sprogs which are just lifting the trailing edge of the sail and are therefore much less effective for pitch stability.
The large jump up in the yellow line at higher speeds represents this effect on pitch stability with the tail in use.
I have flown my T2C with my atos tail a few times to experiment with its effects on pitch stabillity. It obviously dampens out the pitch stability of the wing but the Atos V tail is canted up or positive so it would lift my keel and bring my control bar back around 6 inches and lowered the bar pressure and I wasn't comfortable with this.
I therefore shimmed it up in back to make it neutral in pitch and found it much more to my liking. The control bar stayed in it's previous position with the same amount of bar pressure throughout the speed range and the tail added some pitch and directional stability also.
Although the Combat has a 2 ft. longer wingspan and greater aspect ratio wing so the tail probably does more for it then it would on my T2C. I rarely fly with the tail anymore because I find the wing is very balanced and stable without it. Although it does add 5sq/ft. of lift to the overall performance and therefore I might use it in early spring or winter conditions for that purpose.
Alot of design perameters go into adding the tail for pitch stability and over all safety and I'm sure that Aeros has considered them alll and feels the tail adds more safety and better handling and performance in their package.
Hopefully your first flight on it will alleviate any concerns about wether you stepped into something above your skill set and we can blow off some long flights together in the coming season.