Flexible tailored elastic airfoil section

A flexible elastic wing assembly for generating lift as a result of cambered deflection under load in a moving fluid medium, mounted on a support structure attached to an apparatus operating in contact with a moving fluid medium, said flexible wing assembly comprising

• a) a wing of general planform, having a root section, a tip, a span s, an average chord c.sub.ave, and an aspect ratio AR, said wing having flexible, elastic airfoil sections having an exterior profile of a general, continuous streamlined shape such that adjacent points on said exterior surface remain in contact as the wing deflects in camber, the wing being generally made of flexible materials,
• b) means for pivotably mounting the wing near its leading edge forming a leading edge pivot axis, said pivot axis aligned generally in the spanwise direction, said leading edge pivot axis mounting means attached to the support structure, said leading edge pivot axis mounting means constructed and arranged for passive rotation about the pivot axis said leading edge pivot axis passing generally through the airfoil sections at points near the leading edge, the portion of the leading edge pivot axis between the root and tip of the wing being located an average distance in the chordwise direction from the leading edge of the wing not exceeding 0.25 of the average chord c.sub.ave of the wing,
• c) means for pivotably mounting the wing near its trailing edge forming a trailing edge pivot axis, said pivot axis aligned generally in the spanwise direction, said trailing edge pivot axis mounting means attached to the support structure, said trailing edge pivot axis mounting means constructed and arranged for passive rotation about the pivot axis said trailing edge pivot axis passing generally through the airfoil sections at points near the trailing edge, the portion of the trailing edge pivot axis between the root and tip of the wing being located an average distance in the chordwise direction from the leading edge of the wing of at least 0.6 of the average chord c.sub.ave of the wing, with the average distance between the portion of the leading edge pivot axis between the root and tip of the wing and the portion of the trailing edge pivot axis between the root and tip of the wing having an average distance in the chordwise direction of at least 0.6 c.sub.ave,
• d) means to permit the airfoil sections to slide in a direction generally aligned with their undeformed centerlines to permit proportional cambered deflection of the airfoil under load, the sliding means incorporated into one or both of the pivot axis mounting means.

A flexible, elastic blade assembly for a rotating device operating in a flow mounted on a rotating hub support structure, said flexible blade assembly comprising

• a) a blade of general planform, having a root section, a tip, a span s, an average chord c.sub.ave, and an aspect ratio AR, said blade having flexible, elastic airfoil sections having an exterior profile of a general, continuous streamlined shape such that adjacent points on said exterior surface remain in contact as the blade defects in camber, the blade being generally made of flexible materials,
• b) means for pivotably mounting the blade near its leading edge forming a leading edge pivot axis, said pivot axis aligned generally in the spanwise direction, said leading edge pivot axis mounting means attached to the support structure, said leading edge pivot axis mounting means constructed and arranged for passive rotation about the pivot axis said leading edge pivot axis passing generally through the airfoil sections at points near the leading edge, the portion of the leading edge pivot axis between the root and tip of the blade being located an average distance in the chordwise direction from the leading edge of the blade not exceeding 0.25 of the average chord c.sub.ave of the blade
• c) means for pivotably mounting the blade near its trailing edge forming a trailing edge pivot axis, said pivot axis aligned generally in the spanwise direction, said trailing edge pivot axis mounting means attached to the support structure, said trailing edge pivot axis mounting means constructed and arranged for passive rotation about the pivot axis said trailing edge pivot axis passing generally through the airfoil sections at points near the trailing edge, the portion of the trailing edge pivot axis between the root and tip of the blade being located an average distance in the chordwise direction from the leading edge of the blade of at least 0.6 of the average chord c.sub.ave of the blade, with the average distance between the portion of the leading edge pivot axis between the root and tip of the blade and the portion of the trailing edge pivot axis between the root and tip of the blade having an average distance in the chordwise direction of at least 0.6 c.sub.ave,
• d) means to permit the airfoil sections to slide in a direction generally aligned with their undeformed centerlines to permit proportional cambered deflection of the airfoil under load, the sliding means incorporated into one or both of the pivot axis mounting means.

An elastic articulated airfoil for generating lift as a result of deflection under load in a moving fluid medium, mounted on a support structure attached to an apparatus operating in contact with a moving fluid medium, said airfoil assembly comprising

• a) a plurality of sections joined together to form an articulate airfoil section of a general streamlined shape,
• b) an axis disposed between eac neighboring pair of sections as a means of attaching them together and permitting rotation about said axis,
• c) means for pivotably mounting the airfoil at an axis near its leading edge forming a leading edge pivot axis, said leading edge pivot axis mounting means attached to the support structure, said trailing edge pivot axis mounting means constructed and arranged for passive rotation about the pivot axis the leading edge pivot axis being locatd a distance in the chordwise direction from the leading edge of the airfoil not exceeding 0.25 of the chord c of the airfoil,
• d) means for pivotably mounting the airfoil at an axis near its trailing edge forming a trailing edge pivot axis, said trailing edge pivot axis mounting means attached to the support structure, pivotably mounted on the pivot axes mounting means incorporating the sliding means having a deflection response w to a load p per unit span concentrated at a point Q on the surface of the airfoil section midway between the leading and trailing edge pivot axis, said deflection w at the point Q being generally proportional to p for w between zero and a value such that the point Q passes through the undeflected centerline of the airfoil section, the ratio p/w being the section stiffness S.sub.s the trailing edge pivot axis being located a distance in the chordwise direction from the leading edge of the airfoil of at least 0.6 of the chord c of the airfoil, with the distance between the leading edge pivot axis and the trailing edge pivot axis being at least 0.6 c,
• e) the axes constituting rotation points for the airfoil sections in relation to one another and to the pivot axes mounting means,
• f) means to permit the airfoil section to slide in a direction generally aligned with its undeformed centerline to permit proportional cambered deflection of the airfoil under load, the sliding means incorporated into at least one of the axes,
• g) at least one torsion spring located at said axes disposed between the two relatively rotating elements.

A flexible elastic wing assembly for generating lift as a result of cambered deflection under load in a moving fluid medium, mounted on a support structure attached to an apparatus operating in contact with a moving fluid medium, said flexible wing assembly comprising:

• a) a wing of general planform, having a root section, a tip, a span s, an average chord c.sub.ave, and an aspect ratio AR, said wing having flexible, elastic airfoil sections having an exterior profile of a general, continuous streamlined shape such that adjacent points on said exterior surface remain in contact as the wing deflects in camber, the wing being generally made of flexible materials,
• b) means for pivotably mounting the wing near its leading edge forming a leading edge pivot axis, said pivot axis aligned generally in the spanwise direction, said leading edge pivot axis mounting means attached to the support structure, said leading edge pivot axis passing generally through the airfoil sections at points near the leading edge, the portion of the leading edge pivot axis between the root and tip of the wing being located an average distance is the chordwise direction from the leading edge of the wing not exceeding 0.25 of the average chord c.sub.ave of the wing,
• c) means for pivotably mounting the wing near its trailing edge forming a trailing edge pivot axis, said pivot axis aligned generally in the spanwise direction, said trailing edge pivot axis mounting means attached to the support structure, said trailing edge pivot axis passing generally through the airfoil sections at points near the trailing edge, the portion of the trailing edge pivot axis between the root and tip of the wing being located an average distance in the chordwise direction from the leading edge of the wing of at least 0.6 of the average chord c.sub.ave of the wing, with the average distance between the portion of the leading edge pivot axis between the root and tip of the wing and the portion of the trailing edge pivot axis between the root and tip of the wing having an average distance in the chordwise direction of at least 0.6 c.sub.ave,
• d) means to permit the airfoil sections to slide in a direction generally aligned with their undeformed centerlines to permit proportional cambered deflection of the airfoil under load, the sliding means incorporated into one or both of the pivot axis mounting means,
• e) said leading edge pivot axis mounting means, the trailing edge pivot axis mounting means and the sliding means provided by mounting the wing to the support structure, said structure containing a cavity into which the wing is inserted, said wing in its undeflected position bearing against the walls of the cavity at its leading and trailing edge and bearing against the side of the cavity in its fully deflected position, with the leading and trailing edges of the wing being made of relatively stiff material.
• f) said flexible, elastic wing pivotably mounted on pivot axis mounting means incorporating sliding means having a deflection response w to a load P concentrated in the chordwise direction, and uniformly distributed along the spanwise direction along a line on the wing surface located midway between the leading and trailing edge pivot axis and located between the root and tip of the wing, said deflection w taken at a point Q on the surface of the airfoil section midway between the root and tip of the wing, point Q located on the loaded line on the wing surface, the deflection w being generally proportional to P for w between zero and the value such that the point Q passes through the undeflected centerline of the airfoil section located midway between root and tip, the ratio P/(s w) being the wing stiffness S.sub.w.

A flexible elastic airfoil for generating lift as a result of cambered deflection under load in a moving fluid medium, mounted on a support structure attached to an apparatus operating in contact with a moving fluid medium, said flexible airfoil assembly comprising

• a) a flexible, elastic airfoil section having a leading edge, a trailing edge, a chord c and an exterior profile of a general continuous streamlined shape such that adjacent points on said exterior surface remain in contact as the airfoil deflects in camber, the airfoil being generally made of flexible materials,
• b) means for freely pivotably mounting the airfoil near its leading edge forming a leading edge pivot axis for allowing free pivotable action, said leading edge pivot axis mounting means attached to the support structure, the leading edge pivot axis being located a distance in the chordwise direction from the leading edge of the airfoil not exceeding 0.25 of the chord c of the airfoil,
• c) means for freely pivotably mounting the airfoil near its trailing edge forming a trailing edge pivot axis for allowing free pivotable action, said trailing edge pivot axis mounting means attached to the support structure, the trailing edge pivot axis being located a distance in the chordwise direction from the leading edge of the airfoil of at least 0.6 of the chord c of the airfoil, with the distance between the leading edge pivot axis and the trailing edge pivot axis being at least 0.6 c,
• d) means to permit the airfoil section to slide in a direction generally aligned with its undeformed centerline to permit proportional cambered deflection of the airfoil under load, the sliding means incorporated into one or both of the pivot axis mounting means.