bs wings and rudders

[Vortex]

The part about lift...you know where two air molecules separate at the leading edge and race to the trailing edge but the top mol....yadayadayada...it's complete baloney! Lift is not generated because air must travel faster over the top of the airfoil--the increase in velocity is just a byproduct of the decrease in pressure. Lift is generated by the downwash resulting from the airmass returning to equilibrium after being constricted by the wing and the airmass above. The equal and opposite reaction to this downwash is LIFT. Any suction on the top of the airfoil amounts to just a fraction of one percent of the total lift generated.

 

Ah yes the great debate Bernoulli's theorem VS Newtons Laws of Motion.

 

Everyone can debate the theory all ythey want, but neither is proven incorrect.

All I have to say about that debate is my practical experience in flying a semi symmetrical airfoiled sailplane. On take off, after the sailpane has lifted off you need to increase the nose down attitude until the tug takes off. With a large negative attack angle (chord pointing below the horizon) required when taking off, the wing still creates large amounts of lift.

[ericinexile]

Vortex,

 

There is debate about String Theory and Supersymmetry and the number of dimensions in the Universe. There is no debate about the forces involved in creating lift. The old "air molecules must travel faster over the top of the wing...." nonsense was an invention of Flight Instructors (like myself) to explain lift quickly and simply so we could move on to stuff we ourselves understood--like flying.

 

As to creating positive lift with a negative angle of attack--it's just not possible. I fly sailplanes too and what looks like a negative angle of attack from the perspective of the pilot is still positive from the perspective of the wing's cord line. Remember also that, despite what we instructors say, the relative wind is not EXACTLY perpendicular to the flight path since air changes velocity and vector as the airfoil approaches.

[EtherealN]

Well eric, since your talk is contradicting the material I have from my own studies, I'm going to have to say [citation needed]. Would be an interesting read with some sourced material to pour into the actual maths of it.

[Lobo_63]

So, how come we can hover and change our yaw attitude with the rudder? I've never thought about this before but it does seem to make some sense that you would need at least some airflow over the rudder to have it make a difference. Someone explain to me whats happening please!

 

Check this link for explanation. About halfway down page. Contra-Rotating Coaxial Rotors.

 

http://everything2.com/title/Helicopter%2520yaw%2520control

[triumph]

They cancel out each other's torque, not precession.

 

 

 

Only helicopters with a coaxial rotor system us differential torque for yaw control. Tandem rotor helicopters, like the Chinook, use cyclic inputs.

quite true,the aircrafts body precesses about a fixed point, caused by the input of torque from the rotor shafts.and chinooks do manage to turn quite well without a tail rotor using one of several solutions used in twin rotorcraft.

[triumph]

They cancel out each other's torque, not precession.

 

 

 

Only helicopters with a coaxial rotor system us differential torque for yaw control. Tandem rotor helicopters, like the Chinook, use cyclic inputs.

quite true,the aircrafts body precesses about a fixed point, caused by the input of torque from the rotor shafts.and chinooks do manage to turn quite well without a tail rotor using one of several solutions used in twin rotorcraft.

[triumph]

I'm also really sorry but I don't really understand the meaning of this post either. If you've read about people not knowing these things in other threads, why not post it there so the thread starter (or others in the thread for that matter) could learn from it there - where it connects to what is being said.

 

Also I'm hurting from the horrible paragraphing, why not put some whitespace in the text to make it easier to follow or read - maybe this could even be improved a lot with a small paragraph at the top explaining why this thread was started?

 

Just my humble opinions and constructive criticism =) Hope you don't take it the wrong way

i am sure you are correct, i dont use many forums, so iam new to this.its starting to dawn on me that forums, are mainly for critisism of posts.but its good for info. black shark has a superb flight model.

[Vortex]

Vortex,

 

There is debate about String Theory and Supersymmetry and the number of dimensions in the Universe. There is no debate about the forces involved in creating lift. The old "air molecules must travel faster over the top of the wing...." nonsense was an invention of Flight Instructors (like myself) to explain lift quickly and simply so we could move on to stuff we ourselves understood--like flying.

 

As to creating positive lift with a negative angle of attack--it's just not possible. I fly sailplanes too and what looks like a negative angle of attack from the perspective of the pilot is still positive from the perspective of the wing's cord line. Remember also that, despite what we instructors say, the relative wind is not EXACTLY perpendicular to the flight path since air changes velocity and vector as the airfoil approaches.

 

Point taken about the chord, it sure seemed to me that that old wooden bird was at a negative angle of attack, the damn stick had alot of back pressure and I wondered if the tug was attempting to hit it's vne while still rolling :lol:

 

As I said we could go on and on about this, but if you do have some real proof from a recognised source to post then I'd like to see it. I spent a week last year pouring over the latest submissions and it's still a debating point. Though it doesn't matter really as long we know that you need to have some laminar flow over the wing, and too much angle of attack decreases lift.