HI Guys, I'm still trying to get a handle on the forums...As a general note ,emailing me directly
dan@flywithspa.com is the best way to get a quick reply.Also I typically answer tech questions first, I want to provide good service to those building. If the question seems appropriate I may ask that you post it here for others to see.I will see if Rachel can spread the word.
Ok Tail strength. First we do hammer heads, and snaps rolls on almost every flight. The Panther LS doesn't snap or spin as cleanly as many would like due to its good stability and low wing low wing loading.it has a small entry airspeed window ,and you must make it enter with g load and full rudder. It doesn't retain energy in the snap very long (light wing loading) .To snap/spin you must stall one wing,so stall strips properly placed would likely improve stall/ snaps for the purist.
Next I have heard the accidental tail slide and locked control stuff before and also the no hammer head or tail slide with out tail brace wires. Both are totally unfounded .Many aerobatic aircraft designed in the past 20-30 years do NOT have tail brace wires. think Extra,Yak ,Sukoi,Zlin,Chipmunk,Giles etc. But many do , if you are using steel tube stabs, and control surfaces which are not as common in current design ,you have to have them. adding tail brace wires to a Panther would do nothing but add weight ,drag, complexity, and false piece of mind! You would just shift the load into the fuselage ,with a unknown and likely poor load path! Also consider the fuse has the same torsional margins as the tail was designed for,so if you don't feel the tail is strong enough ... the tail cone isn't either! If you added brace wires,you would falsely think you have made it "stronger", and "safer" but wouldn't have .
As for jamming controls in tail slide (regardless of how it was entered) it is not a real concern. if you freak out and go into the fetal position and leave controls to flop and did this repeatably you may have stress cracking and damage etc. But if cannot keep pressure on rudder pedals and a firm hold of stick ,you have absolutely no business doing any acro ,in ANY aircraft! Also consider that the Panther LS has a VA of128 mph (maneuvering speed). Below this the aircraft will stall before doing structural airframe damage. If Sean D Tucker tried to get the Panther to tail slide he couldn't even get close to this speed while "backing up". Watch Him do tail slide on you tube, his controls are constantly moving trying to force the aircraft into "Rutan" mode! How could he do this if the controls "JAM" in a tail slide? The Panther has a good tail volume (length VS area) and will aggressively resist becoming a canard! In respect to botched hammer head (which we all do) the Panther dose just fine and quickly, but some time uncomfortably for your stomach, points it self in the correct direction again. The engine sometime quits do to the "whip" but it fires right back up.
In regard to hinge design ask any engineer (Paul) if he would rather have 2 points to gather loads across a stab /control surface, or the load spread evenly across entire structure! When we load test the Cougar tail I will include a hinge loading case and then repeat this with a Harmon rocket horizontal I have on the shelf (2 hinge points for each elevator 270 MPH vne and a 300 hp engine beating it to death, hmmm) and will have some interesting data to show ! also the Panther has good stops on the controls also.
Two more points this brings me to, tail slide /whip stall can produce very high loads on other components , mostly the engine mount and its attach points. this is a serious concern on heavier engines.
Another concern is the "pounding" from the engines. This is a big reason we do not design for constant speed ,or metal props. Watch a RV-x with a wood prop, then a metal, or constant speed prop crank up or shut down, and notice how the tail shakes ! The pounding and vibration from the high inertia props combined with the larger (0-320) 4 cylinder engines ,On the low mass Panther Airframe will effect the service life (this is true for any aircraft)
Last Point , Anytime frequent "hard" aerobatics are preformed , the inspection and maintenance program need to be adjusted. All parts of airframe need post flight inspections and frequent "heavy" inspections on all attach points etc!
The Panther will satisfy the aerobatic itch of most pilots , but if aggressive high energy snaps, tumbles ,and outside maneuvers are needed ,then you should consider one of the many unlimited choices (pitts one desighn etc)
Thanks Dan
