# P-39 - P-51 drag comparison



## Vic Nighthorse (Jan 13, 2019)

I think I once saw a P-39 - P-51 drag comparison of some sort, maybe here. No sure if it was all drag or parasite or what. I don't remember much about it other than I found it interesting and that the P-51 had less. Does anyone know of any such comparison and or can point me in the right direction?
Thanks again.


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## P-39 Expert (Jan 18, 2019)

The P-51A obviously had less drag since it was 10-15mph faster than the P-39 with the same engine even though it weighed 1000# more and had a 10% larger wing. Irregardless of the Meredith effect and the laminar flow wing (doubtful that either achieved the test results in practice) the P-51 was maybe the cleanest propeller plane in WWII.

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## Vic Nighthorse (Jan 18, 2019)

The P-39's NACA 66-116 root - 66-216 tip profiles were attempts at greater laminar flow as well, no? I am very interested in where the P-51's drag savings over the P-39 were and at what 'opportunity' costs they were achieved.


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## P-39 Expert (Jan 19, 2019)

Vic Nighthorse said:


> The P-39's NACA 66-116 root - 66-216 tip profiles were attempts at greater laminar flow as well, no? I am very interested in where the P-51's drag savings over the P-39 were and at what 'opportunity' costs they were achieved.


P-39 had a symmetrical airfoil (top same as bottom), different from a laminar flow airfoil on P-63.


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## Vic Nighthorse (Jan 19, 2019)

Oops, I did mix up the airfoils of the two aircraft and did so many months ago too However, just in case you were unaware, NACA 6 series airfoils (which the P-63 used) can be symmetrical or not. If the zero degree attack lift coefficient after the hyphen is 0, it is symmetrical. As you mention in your first reply, however it is all moot anyway since riveted aluminum wings are almost never smooth or accurate enough to achieve the greater laminar flow of the designs. Thanks for your responses and correcting my mistake.

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