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Now I´m in it up to my neck!?

Posted by Christer on Fri Oct 05, 2001 11:35:52 AM

In reply top Re: Corsairs bendy wing posted by MickM on Fri Oct 05, 2001 07:17:13 AM

Mick,

again from what I?ve read, the stalling characteristics of the Corsair is due to the flap in fully extended landing position disturb the airflow over the horisontal stabilizer. Especially under cross wind conditions pilots often choose to reduce the flap setting. This prompts a higher approach speed with higher margins but, in consequence longer landing distance.

I?ve also read a little about the Bearcat, the articulated landing gear legs were neccesary to fit them into the wing inboard of the cannons.
There were several means of achieving this, e.g. the twenty-series Spitfires, haveing a larger diameter propeller than the earlier Griffon-Spits, had a device which compressed the oleos when retracting the landing gear.

Regarding the Stuka, I haven?t got a clue, never studied it.

To the subtelties of aerodynamics, well, I?m a keen glider pilot and the design of gliders focus on reducing drag because it?s simply a drag!
One of the most renowned designers is a personal friend of mine (have flown his designs for years) and through him I?m acquainted with the work of a professor of aerodynamics at the University of Delft who is into the airfoil research.

I won?t dig too deep into this but generally the drag-coefficient can be subdivided into three parts:
1) The frontal area of the airframe (what "hits" the airflow) and the wet area of the airframe (what the airflow has to travel along). These two together is called the friction drag or zero drag (when the airfoil is generating zero lift).
2) The interference drag is caused by the airflow around the wing, the horisontal stabilizer and the fin interfering with the airflow around the fuselage.
3) Induced drag is the drag from all lift producing members. The main contributor is the wing but also the stabilizor and fin generate drag. The higher the lift-coefficient, the higher the drag-coefficient.
Lift produced by an airfoil is proportional to the airspeed and angle of attac. To maintain level flight (at constant altitude) the angle of attac is high at low speed, using a high lift-coefficient. The angle of attac is low at high speed using a low lift-coefficient.
If you then start turning the angle of attac gets dramatically higher, especially at low speeds. This is often referred to as bleeding energy.
This put together tell you that the induced drag is predominant at low speeds and whenever you are turning, and the friction drag is predominant at high speeds.
Now we?re back to the Corsair quiz, the interference drag.
The friction drag and the induced drag contribute at least 90% of total drag and the interference drag contribute the balancing less than 10%, which means that it?s not as important as the other two.

In glider design today the interference drag is becoming more and more important. The other two components of total drag have been reduced enough to make a reduction in interference drag a significant improvement.

Now to another quiz:
When a glider flies it trades altitude for speed, unless there are thermals of rising air it will eventually regain contact with terra firma.
The glider weighs some 500 kg, has a rope attached to it, a very long one which runs over a pulley to hang a weight at the other end.
How much weight is required to compensate for the drag and make the glider fly without the sacrifice of altitude?
(I know the answer for the glider but not for the Corsair!)

Regards,
Christer

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