GB2100688A

GB2100688A - Airfoil construction

Info

Publication number: GB2100688A
Application number: GB08120584A
Authority: GB
Inventors: Derek Alan Taylor
Original assignee: Open University
Current assignee: Open University
Priority date: 1981-07-03
Filing date: 1981-07-03
Publication date: 1983-01-06

Abstract

A semi-rigid airfoil or sailwing is characterised by the provision of a rigid trailing edge (14), for example a tubular metal spar. The trailing edge is preferably linear. The blade is completed by a rigid leading edge (10, 12) and a flexible cover (16) which defines the airfoil shape. Applicable to wind turbines, helicopter rotor blades, sailing vessels, hang-gliders. <IMAGE>

Description

SPECIFICATION Airfoil construction This invention relates to semi-rigid airfoils, or sailwings, and is particularly concerned with the construction of such sailwings.

Semi-rigid airfoils or sailwings find application in many aerodynamic machines and structures, for example in wind turbines, helicopter rotor blades, sailing craft, hanggliders, etcetera.

in the conventional sailwing or airfoil, such as described in US patent specification 3597108 for example, the sailwing assembly comprises a rigid tubular spar and leading edge fairing, which defines the leading edge of the sailwing, a trailing edge cable which defines the trailing edge of the sailwing, and a flexible wing material which extends around the leading edge fairing and trailing edge cable to define the shape or form of the airfoil. The trailing edge cable extends in a predetermined catenary or curve, and it is known to provide means to vary the tension in this cable as a function of rotary speed in order to reduce undesirable stresses which can be induced in the structure.

It is an object of the present invention to provide a sailwing of improved construction and which has a number of important advantages.

Broadly in accordance with the present invention there is provided a semi-rigid airfoil or sailwing which comprises a rigid leading edge, rigid trailing edge, and a flexible material extending between the leading and trailing edges for defining the form of the airfoil or sailwing.

The sailing preferably includes a root portion at one end and a tip portion at the other end with the leading and trailing edges extending between the root and the tip.

The use of a rigid trailing edge provides a number of important advantages as compared with the use of a trailing edge wire or cable.

The relatively simple blade construction avoids the need for any complex profile shaping.

Also, the use of a rigid trailing edge avoids one of the problems of conventional sailwings, where a catenary trailing edge has to be cut in the sail fabric. Additionally, the use of a rigid trailing edge enables sailwing blades made with this construction to be used on relatively large wind turbines for example. One can also achieve a relatively lightweight construction, resulting in as much as 50% saving in weight compared with conventional airfoil blades.

The sailwing of the present invention also has good safety characteristics.

One presently preferred embodiment of sailwing in accordance with the invention will now be briefly described by way of example and with reference to the accompanying drawing, in which: Figure 1 is a schematic view of a sailwing in accordance with the invention; Figures 2a and 2b show respectively the unloaded and loaded profile of the sailwing of Fig. 1; and, Figure 3 is a schematic sectional view through the sailwing of Fig. 1, again showing the loaded and unloaded profile of the sailwing.

As shown in the drawing, the sailwing of the present invention comprises a rigid tubular spar 10, for example of aluminium alluy, which extends between a root portion and a tip portion, neither of which are shown in the drawing. A drooped leading edge fairing 1 2 is secured to the tubular spar 10 to define a streamlined rigid leading edge of the sailwing.

The droop angle is indicated at a in Fig. 3.

The sailwing includes a rigid linear trailing edge which is here shown as a second aluminium alloy spar 1 4 set at an appropriate orientation in relation to the leading edge. For example, the sailwing may have a fixed pitch with a twist of 28 . The combination of rigidity and linearity for the trailing edge gives the advantages referred to above. A flexible wing material 1 6 extends around and over the streamlined leading edge and the rigid trailing edge with or without attachment to either edge. The wing material 1 6 is preferably a polyester fabric material, although any suitable flexible material which will define the shape or form of the airfoil may be used.

In Figs. 2 and 3 of the drawing the contour of the sailwing fabric 1 6 when subject to aerodynamic loading is indicated. The contour of the sailwing fabric when unloaded is indicated in Fig. 2a and by broken outline in Fig.

3. The contour when loaded is shown in Fig.

2b and in solid outline in Fig. 3.

1. A semi-rigid airfoil or sailwing comprising a rigid leading edge, a rigid trailing edge, and a flexible material extending between the leading and trailing edges to define the contour of the airfoil or sailwing.

2. An airfoil or sailwing as claimed in claim 1, in which the rigid trailing edge is linear.

3. An airfoil or sailwing as claimed in claim 1 or 2, in which the rigid trailing edge comprises a metal spar.

4. An airfoil or sailwing as claimed in any preceding claim, which includes a root portion at one end and a tip portion at the other end with the leading and trailing edges extending from the root portion to the tip portion.

5. A semi-rigid airfoil or sailwing as claimed in claim 1, substantially as hereinbefore described with reference to the accompanying drawing.

6. In combination with at least one semirigid airfoil or sailwing as claimed in any preceding claim, a rotatable rotor shaft, and

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Airfoil construction This invention relates to semi-rigid airfoils, or sailwings, and is particularly concerned with the construction of such sailwings. Semi-rigid airfoils or sailwings find application in many aerodynamic machines and structures, for example in wind turbines, helicopter rotor blades, sailing craft, hanggliders, etcetera. in the conventional sailwing or airfoil, such as described in US patent specification 3597108 for example, the sailwing assembly comprises a rigid tubular spar and leading edge fairing, which defines the leading edge of the sailwing, a trailing edge cable which defines the trailing edge of the sailwing, and a flexible wing material which extends around the leading edge fairing and trailing edge cable to define the shape or form of the airfoil. The trailing edge cable extends in a predetermined catenary or curve, and it is known to provide means to vary the tension in this cable as a function of rotary speed in order to reduce undesirable stresses which can be induced in the structure. It is an object of the present invention to provide a sailwing of improved construction and which has a number of important advantages. Broadly in accordance with the present invention there is provided a semi-rigid airfoil or sailwing which comprises a rigid leading edge, rigid trailing edge, and a flexible material extending between the leading and trailing edges for defining the form of the airfoil or sailwing. The sailing preferably includes a root portion at one end and a tip portion at the other end with the leading and trailing edges extending between the root and the tip. The use of a rigid trailing edge provides a number of important advantages as compared with the use of a trailing edge wire or cable. The relatively simple blade construction avoids the need for any complex profile shaping. Also, the use of a rigid trailing edge avoids one of the problems of conventional sailwings, where a catenary trailing edge has to be cut in the sail fabric. Additionally, the use of a rigid trailing edge enables sailwing blades made with this construction to be used on relatively large wind turbines for example. One can also achieve a relatively lightweight construction, resulting in as much as 50% saving in weight compared with conventional airfoil blades. The sailwing of the present invention also has good safety characteristics. One presently preferred embodiment of sailwing in accordance with the invention will now be briefly described by way of example and with reference to the accompanying drawing, in which: Figure 1 is a schematic view of a sailwing in accordance with the invention; Figures 2a and 2b show respectively the unloaded and loaded profile of the sailwing of Fig. 1; and, Figure 3 is a schematic sectional view through the sailwing of Fig. 1, again showing the loaded and unloaded profile of the sailwing. As shown in the drawing, the sailwing of the present invention comprises a rigid tubular spar 10, for example of aluminium alluy, which extends between a root portion and a tip portion, neither of which are shown in the drawing. A drooped leading edge fairing 1 2 is secured to the tubular spar 10 to define a streamlined rigid leading edge of the sailwing. The droop angle is indicated at a in Fig. 3. The sailwing includes a rigid linear trailing edge which is here shown as a second aluminium alloy spar 1 4 set at an appropriate orientation in relation to the leading edge. For example, the sailwing may have a fixed pitch with a twist of 28 . The combination of rigidity and linearity for the trailing edge gives the advantages referred to above. A flexible wing material 1 6 extends around and over the streamlined leading edge and the rigid trailing edge with or without attachment to either edge. The wing material 1 6 is preferably a polyester fabric material, although any suitable flexible material which will define the shape or form of the airfoil may be used. In Figs. 2 and 3 of the drawing the contour of the sailwing fabric 1 6 when subject to aerodynamic loading is indicated. The contour of the sailwing fabric when unloaded is indicated in Fig. 2a and by broken outline in Fig. 3. The contour when loaded is shown in Fig. 2b and in solid outline in Fig. 3. CLAIMS

6. In combination with at least one semirigid airfoil or sailwing as claimed in any preceding claim, a rotatable rotor shaft, and means connecting said at least one airfoil or sailwing to the rotor shaft for rotation therewith.