Ok got message from Gene (Crumpp) and here's what he had to say (I left my questions to him first);
My mail to Gene (Crumpp):
Gene's response:
Hi Soren,
I hope things are going well for you. I appreciate your vote of confidence.
I do know Bill. He is not only very knowledgeable but someone I consider a friend. It is very disappointing to hear that you two cannot get along discussing old airplanes.
I can certainly clarify what I meant however the two points do not seem to be related or at least I cannot see how they are related. The only thing in common is the term "elliptical lift distribution". Lednicer is referring to the cl/CL ratio which gives us a clue as to the wing efficiency. The analysis is made at 360Kts at 15,000 feet and is good for that condition. Wing efficiency will change with condition of flight and square wingtips can very easily be designed that equal elliptical wings. However they are designed to be that optimal for a specific condition of flight. For example at the Prmin point, L/Dmax, or Va would serve as a design point depending on what the performance the designer desired.
Since the Mustang and FW190 are designed to most efficient at one design point and the Spitfire has an elliptical wing which is efficient at all points, Lednicer's observation is correct in that the Spitfire probably has the most optimal of the three. Probably is used because the aerodynamic twist in the Spitfire wings in order to prevent the wing from stalling all at once reduces this efficiency. That too would be designed for an optimal point of performance.
Make Sense?
This statement refers to the fact aeroelasticity removes the aerodynamic twist placing the airfoil sections at the same co-efficient of lift. The sections then reach CLmax all at the same time. When one side of our wing or the tips stall, the aircraft will drop a wing or if the stall is large enough, the aircraft will roll inverted. That is what Lednicer is saying. This was not a design feature. It is just an explanation for the differences in the FW190's stall behaviors.
That is pretty much what the spanwise lift loading notes. It has nothing to do with the stall behaviors of the FW190 but is gaining insight as to the relative efficiency of the wing designs..
Does that help?
All the best,
Crumpp
I then sent him another mail, just incase I might have misunderstood anything he said, and here's his answer (With my questions):
No you are right. That is what causes the harsh stall. It is not a design feature however. It is just and explanation for the two different stall characteristics of the design.
You are right on this too. The Spitfire does not achieve the full efficiency benefits of elliptical wing construction due to the washout. At the same time though it is probably the most efficient of the three. If we examine the aircraft at a design optimum point, you will find little to no difference.
So the debate is now settled I hope.
Please forward the email to me in it's entirety. And please both thank Gene for his compliment and ask Gene to read this thread and ask him to comment.
I won't contact him directly to ask him to settle this but I would be interested if he wishes to do so at some future time
Then go back to my Post 77 where I discussed varying tip ratios to approximately .4 to obtain eliptical wing like induced drag... and discussed the effect of twist.. and the effect to twist when lift loads change due to aeroelastic effects.
Then please get to point of the effect of torsion versus bending on shift of load distribution causing the violent stall.
Then please go back to the post where I said that all wings show 'elliptical like' lift distributions, but the Spit moreso that the Fw 190 (and the Mustang)
Then please reflect that torsion at the wing tip is what caused the the entire wing to stall nearly at once.
The implication, which I don't think you grasped, was that the wing torsion caused the outer 20 percent to actually 'go positive' from zero twist, thereby increasing that region's approach to CLmax.. as the inboard 80% which was twisted to approach CLmax.
Then contrast that to what Gene said in his email
Then contrast what I have said before about control reversals on a Spit due to the aileron loads causing torsion in the wing at the tip.
Then contrast it to what I have said about manuevering performance is impossible to precisely predict relative to Cl as an example because that changes depending on the aeroelastic effects on the wing (and fuselage in both turn and other loads on the fuse bt the elevator and rudder) cause the geometry and angles of attack locally relative to freestream V.. affecting where it is in the CL curves relative to CLmax
Then go back and read what you just quoted from Gene - and last read what you said to start this debate.
Soren blurts - "However in the
case of the 190 you will note that the wing twist was applied to such a degree as to provide elliptical lift distribution
under G's (which btw is the reason for the violent departure), it was purposely done so to achieve the maximum 'e' factor and therefore L/D ratio in turns. Now ofcourse you wont see that on Lednicer's comparison as his simulation was done under 1 G, something you seem unable to grasp."
Now show each statement you got from Gene to prove your statement
You win - right??
