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LAMINAR FLOW, BY ACCIDENT!
During the 1930’s a self-taught aerodynamicist named David R. Davis went to the trouble of patenting an airfoil design, which he called the “Fluid Foil” (US Patent #1,942,688). He considered his design special because it exhibited lower drag than most other common airfoils, but he wasn’t sure why. Fortunately for Mr. Davis, the Consolidated Aircraft Company was looking for a marketing trick to make their new aircraft stand out from the competition; a unique low-drag wing was just the ticket. After verifying the low-drag performance of the Fluid Foil, Consolidated licensed the airfoil patent from Mr. Davis in 1937. Fluid Foil eventually found its way into the wing design of the B-24 Liberator bomber during WW2. (Ref: Vincenti, 1990)
Without knowing it, Mr. Davis had inadvertently invented the first airfoil to achieve low-drag through encouragement of a laminar boundary layer; the rarely seen smooth airflow that briefly exists before the higher-drag, turbulent boundary layer takes over.
Consolidated Aircraft went on to build over 19,000 of the B-24 bombers, putting it ahead of even the venerable B-17 in production count. Although many people consider the P-51 Mustang to be the first aircraft to use laminar flow airfoils, the truth is that the B-24 was the first, albeit accidental, aircraft to use laminar flow airfoils. The true significance of the P-51 wing was that it was the first to intentionally use the new scientifically developed NACA 6-series laminar flow airfoils.
As interesting as these historical facts are, it’s even more amazing to learn that neither of these airfoils actually produced much usable laminar flow when integrated on real world aircraft. In fact, they were just as turbulent as every other plain vanilla airfoil out there. We can forgive the designers though because all of their data came from finely polished wind tunnel models built to exacting contours. When they tried to reproduce the same contour and finish with sheet metal, rivets, bucking bars, hammers, and a War raging, it just did not function. Add mosquito guts to the wing leading edge and...
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Recommended References For Airfoil Enthusiasts:
About John Dreese:
John Dreese is a graduate of the Ohio State University, having earned both a Bachelors and Masters Degree in Aeronautical Engineering there during the 1990's. An aerodynamicist by training, John has spent over a decade working with all aspects of wind tunnel testing. Since 1996, he has been developing airfoil geometry generation & analysis software. After completing his Masters Degree, he worked in the exciting world of experimental aviation. Since then, he's worked on many interesting projects. John is a licensed pilot, a member of the EAA, and flies in brutal RC combat competition.