Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.) Filing date Publication date Priority claimed from US13245271A external-priority Application filed by Boeing Co filed Critical Boeing Co Application granted granted Critical Publication of US3698668A publication Critical patent/US3698668A/en Anticipated expiration legal-status Critical Status Expired - Lifetime legal-status Critical Current Links Original Assignee Boeing Co Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.) Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) Expired - Lifetime Application number US132452A Inventor James B Cole Current Assignee (The listed assignees may be inaccurate.
#Low camber airfoil pdf
Adding slots between segments will make those work even better than a solid airfoil and allow to use more camber.- Google Patents US3698668A - Variable camber airfoilĭownload PDF Info Publication number US3698668A US3698668A US132452A US3698668DA US3698668A US 3698668 A US3698668 A US 3698668A US 132452 A US132452 A US 132452A US 3698668D A US3698668D A US 3698668DA US 3698668 A US3698668 A US 3698668A Authority US United States Prior art keywords airfoil hinges canted pair camber Prior art date Legal status (The legal status is an assumption and is not a legal conclusion. Again, as soon as a lot of lift at low speed is needed, thin, highly cambered airfoils are the best choice. Note that aircraft with a high wing loading use extensive and extensible high lift devices which turn their wings into thin, highly cambered structures for landing. This is similar to the use on propellers: A wider operating range requires to move away from the narrow optimum offered by those highly cambered airfoils. As soon as the aircraft needs to cover a wider speed range, however, a lower camber is needed to keep drag low at high speed. Those with low maximum speed like human powered or electric propulsion aircraft prefer those airfoils because they create the needed lift at the lowest possible speed, so the aircraft can fly with the limited installed power. Use on wings: Some aircraft do indeed use highly cambered airfoils. Those are more stubby and enjoy much narrower variations in flow conditions, so the highly cambered, thin airfoil is indeed the best choice here. Note that indeed thin, highly cambered airfoils are used on compressors and turbines in jet engines.
In off-design points (i.e., most of the time) the propeller would have poor performance when compared with one which tolerates more diverse conditions. Of course you can pre-twist the blade so it will assume the correct shape in the desired operating point, but a propeller needs to work over a wide range of operating points, from take-off roll to high speed flight at altitude. First propeller use: A highly cambered airfoil would cause high pitching moments and twist the propeller blade.
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