Dramatic drag comparison
 

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.
http://i1271.photobucket.com/albums/...titled5_14.jpg
(we don't need no stinkin' streamlining):p
PS, the table is from 'Boundary Layer Theory,' by Hermann Schlicting,7th-Edition

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.

Change that circle to a square and see how much smaller it'd have to be.

Either way, good lesson.

Just need to quote this next time the "Can I increase frontal area AND reduce drag?" question comes up.

Now I understand, thanks aerohead. CD and frontal area much more dependent on cd, especially when it gets low enough.

regards
mech

Clarify for me, by "drag" do we mean CdA and not just Cd? The airfoil has identical CdA? Seems increadible. That's not the case right? This is just identical Cd, yes?

Drag is the force pushing back on the body as it moves through a fluid. it is directly proportional to CdA as long as fluid density and velocity are held constant.

Exactly! My travel trailer build will have a much lower CDa because of this. More can be less, much less :)

That's stunning.

I remember seeing add-on fairings to make the cables on one's ultralight aircraft less of a drag, but they didn't significantly increase the frontal area, they weren't much more than stiff tapes to add to the cable.

This shows that one could replace the cables with, for instance, spars and still have no net gain while picking up lots of strength.

A little reality check on the math though....

35 times the frontal area? That means it has 1/35 the drag coefficient, right?

1/35 = .029

IF the coefficient for the round shape was 1 (it must be less, but follow along), the coefficient for the airfoil is .029? Seems too low, even for a section of a chord? Someone has some numbers, right?