Quote:
Originally Posted by mpg_numbers_guy
....... CdA = Cd*A is more important than just Cd.
|
Not to sidetrack the thread, or dispute the math but those old black and white pre WWII films NACA did on bi-plane aircraft bracing planted a disturbing seed in my head.
If I recall correctly what they showed was a round guy wire in tension having similar drag to teardrop shaped wing bracing of ten times the guy wire size.
If my memory is not faulty, then shape is far more important than size which runs contrary to the math quoted above.
Turn down the sound - sorry, could not find the original narration.
1935 Aerodynamics Air Flow and Flow Separation NACA 1
EDIT-1:
Found this......................
Dramatic drag comparison
https://ecomodder.com/forum/showthre...son-32585.html
Quote:
Originally Posted by aerohead
The following is an anatomical drag comparison between a circular cylinder section and a NACA laminar wing section.
The two bodies are shown in true size relationship to one another.
The laminar wing section is 167-X longer than the cylinder.
They have identical drag.
(we don't need no stinkin' streamlining) 
PS, the table is from 'Boundary Layer Theory,' by Hermann Schlicting,7th-Edition |
Sorry about the blurry image -
freaking Photobucket.
Quote:
Originally Posted by darcane
Last two digits for NACA airfoil designations indicate maximum thickness as a percentage of chord.
21% of 167 is 35.1.
So this NACA airfoil has the same drag as the cylinder in spite of having a 35 times larger frontal area.
|
Not 10X, but 35X ?
Still reading that old thread.
https://ecomodder.com/forum/showthre...n-32585-2.html
Quote:
Originally Posted by RedDevil
Compare this to the old video Darcane posted in this link:
http://ecomodder.com/forum/showthrea...rag-25378.html
From that, at 5:49:
A properly streamlined strut can be 10 times thicker than a wire and yet have no more drag.
Ten times. That is quite a bit less than the NACA wing shape, but the wing shape used there did not have the concave tail section.
Would that alone make for such a big difference? |
EDIT-2:
Here is the link to those old films - with original narration.
2013
NCFMF Video: How to Reduce Drag
https://ecomodder.com/forum/showthre...rag-25378.html
Quote:
Originally Posted by darcane
I found this very interesting video on another forum, but it is very applicable here so I thought I'd share:
There is a whole collection of these National Committee for Fluid Mechanics Films (NCFMF) videos. More here: National Committee for Fluid Mechanics Films |