sillyness

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It fits perfectly... if the CG moves forward, CLTail must decrease (to provide more down-force), so CLWing must increase... clear as day!!! The nomenclature is confusing... the equation is botched a little... it should say CLAirplane = CLWing/Fuse + CLtail... obviously the way it is written CLTail would have to equal zero or the equation would be invalid.


Changing AOA... the only way to increase CL at a constant speed, air density, and wing area is to change AOA... it's one of those aerodynamics basics. CL is dependant only on wing shape and AOA. The graph looks like a 45 degree line with a bump at the top, then it falls a little and disappears... the bump is critical AOA.

I have to admit... after a little more reading the tail does produce a little more trim drag than I thought, so I think we need to meet somewhere in the middle for a correct answer.

BaldEagle,

When you asserted that I was wrong talking only about parasitic and induced drag I let you talk me into a wrong statement... my bad. I was correct to begin with. Parasitic drag is a generic term used to describe the sum of skin friction, form, and interference drag. Straight from a Stanford text.

rmh

OK and really the the speed must increase over the original --enough--to compensate for the increased drag
Here is my view of powered aircraft:
the airframe is a shape - made to provide a "space/size and lift POSSIBILITY" as required for a specific task
the thrust available--is the key to it working - period
that is-- no matter how weird it looks - power will make it work . The classic comment of flying a barn door with enough power is a true statement -and that is demonstrated more and more every passing day .
Over the years -- power has controlled the shape of the powered airplane.
All of the volumes of drag and minute definitions of drag and endless futzing on airfoils on and on ad nauseum, are and were done to make an aircraft work --- with the power available for the job.
Had anyone - anywhere --even Outer Mongolia- in 1900 -- been given a extremely light reliable engine with 10 times the power available at that time -
The evolution of the powered airplane would have happened 100 times as fast
It is all about power and the adaptation of materials to utilize it.
don't buy it?
look at current aircraft design - the driving forces are material adaptability and structure and power-power- power -power

Wings-RCU

My Feedback: (2)

That is why I quit contributing to the thread. There is no factual information discounting the FAA reference or supporting the "wing loading doesn't change with a shift in CG" theory. There may be, but I can't find any, and it's not presented here. right now it has become an academically challenged marathon where the person who gives up last wins. Too bad.

rmh

academically challanged?
You may choose to accept only what you read but making that kind of comment is a bit off base.

BTerry

My Feedback: (8)

Only a fool allows his schooling to get in the way of his education.

This thread has been an education. Much of it violates my "education", but at one time we couldn't explain why a bumblebee can fly.

The secret to a Cap is keep it LIGHT, pay attention to speed over the lifting and controlling surfaces, keep plenty of thrust on tap, and enjoy the heck out of it.

Wings-RCU

My Feedback: (2)

You are right Dick, academically challenged was off base. My apology.

bterry, Cute saying: But, like medicine aerodynamics is a science, not an art, and hypothesis should be proven through research. If you chose to call "because I think it so" education you’re free to do so. I am only asking for some corroborative information, not multiple double blind studies.

BaldEagel

Silly

If that is from the Stanford Text then they are wrong also, parasitic drag is from parasitic influences to use one of your favorite comments thats a indisputable fact.

Someone said earlier "Do not let your schooling get in the way of your education"
I could not agree more, this discussion and the theories being miss quoted are so off base its become a nonsence. its the way of the world that some think that if you talk long and loud you eventually will be belived, unfortunatly the more often they say something the more they convince themselves they are right.

Unsubscribing from this thread.

Mike

sillyness

My Feedback: (25)

Thank You.

Dick,

I talked to a friend of your recently... co-writer for 3DFlyer. VERY NICE GUY!!! Gave you endless compliments... you're lucky to have such a great buddy. I won't repost his e-mail since I didn't ask permission, but his feeling is that the truth lies in between our two viewpoints. He said int he classical sense AOA must increase, but with long tail moments and zero or upthrust generating a vertical prop normal force with the required power increases, there may be no AOA change. It all depends on the particular design.

Can't we all just get along!

rmh

Thanks - He puts up with my home spun ideas --
The only formula I really ever understood was Similac

sillyness

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[sm=bananahead.gif]

BTerry

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Nice attitude. This pissing contest should probably get moved to a different forum, the original intent of the thread is long since past. I was responding only to your personal attack comments.

I was referring to the talk of high-AOA flight referenced in this thread, not the steady-state, level flight, shifting CG stuff. Trim drag induced by the stab to offset the couple created when CG is moved further forward of the Center of Pressure, I understand that stuff and I don't dispute it.

Aerodynamics IS a science, but one which is not yet fully understood or explained, especially in the low Reynolds/high relative viscosity ranges we are using. We can NOT see the "whole picture". Also like medicine, aerodynamic knowledge is progressing. This is where the "art" comes into play. The rules are not always black and white, otherwise ANYBODY could be a good doctor!

The bumblebee analogy was used to demonstrate a situation wherein science was not fully able to MEASURE what is happening, and that aerodynamic knowledge at the time was insufficient to explain why the beast flies. We lacked the tools to solve the proper equations. With modern computers, and progress in the art of aerodynamic science and high-speed cameras, we can easily see why the bumblebee flies.

If you want corroborative information, take a look at the real-world flying experiences being expressed by people in these forums actually flying multiple airplanes and experimenting. Discounting a person as "academically-challenged" only because his topics don't completely conform to known formulaic constraints is an exercise in futility.

The real answer lies between the viewpoints (referring to the high-AOA flight stuff) expressed herein. Perhaps we need to get our collective noggins together and write the RCU Principle for the next generation of aerodynamic textbooks.


Unsubscribed...

rmh

On a happy note -- the ol CAP has a new carb and it now works as it should and just needs enough fuel to fly 2300 miles --
So ---------- put all this conjecturing to the real test .


fly it

sillyness

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Geesh... people with tempers!

It's fluid dynamics... by nature there are no closed form classical equations to describe every possible scenario.

sillyness

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FWIW... the same CG scenario should apply to glider... your friend reminded me of something I forgot... Power is nothing more than speed*drag. Gliders have power too, they just get it from gravity, and they are a cleaner model to look at... no Normal force, P- factor, thurst angles, centrifugal, or torque, or other effects. But, on most gliders, the tail moment is very long, resulting in minimal changes in tail downforce, and very miniscule changes in AOA (little additional induced drag) or tail trim drag (since very small inputs required)... hmm... seem well designed, don't they?

BTerry

My Feedback: (8)

Silliness,

When I look at free-flight gliders and discus-launched gliders I notice an interesting concept, relating to your analogy. Many designs now use an extremely-long tailbooms with miniscule control surfaces. The torque applied to change the AOA is the same, but the actual downforce supplied by the elevator is significanly lower.

Is this efficient? Definitely. Is it practical for most airplanes, especially the aerobatic planes, probably not. However the concept is an interesting one!

BTerry

My Feedback: (8)

I'm not going to change the CG on that plane. Why should I mess with success, the plane was already set up by The Master himself!

Thanks for the carb work, btw.

Brett

F2G-1

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NEXT TOPIC FOR DISCUSSION:

Why is water 'wet'?

BTerry

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Hydrogen bonding between water molecules and with hydrophylic surfaces?

F2G-1

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does a symetrical airfoil produce any lift @ 0 AOA?

rmh

It won't produce a negative lift.

F2G-1

My Feedback: (13)

just goes where you point it?