Aerodynamics of Wingsails

Wingsail Science on the Web

There are several resources on the internet that give info about the science of wingsails: LUSAS, an engineering software firm, have an analysis of the wingsail; the US Windsurfing Newsletter has an introduction to marine aerofoils; and Dynawing offer a comparison of wingsails and conventional sails, as does Wingsail Co.

The following is extracted from a report prepared as part of the work done by Cooke Associates on establishing the commercial viability of the wingsail. The bulk of this report necessarily remains confidential. If, however, you should have a commercial interest in the commercial development of wingsail technology, please contact Anne Toms at


The Walker wingsail is a novel form of marine propulsion, expected to provide significant advantages over traditional, "soft" rigs. To do so, it needs a higher maximum lift coefficient and lift-to-drag ratio than such rigs. Current sailing knowledge suggests that wingsails do fulfil these requirements but that, at low wind speeds, their associated weight penalty can nullify their benefits.

Comparisons between available data for the Walker wingsail and soft rigs have been made, confirming the aerodynamic superiority of the wingsail; however, the specific extent of the weight penalty remains unknown. The Walker wingsail has also been compared with another design, by Boatek, via numerical simulation of two-dimensional section aerodynamic characteristics. The Boatek design is predicted to exhibit better aerodynamic characteristics, probably due to the use of cambered, as opposed to symmetrical wing elements. Cambered designs, however, must be rotated each time the boat changes tack.

This report describes a brief aerodynamic assessment of the Walker wingsail.

Summary of Principal Conclusions

This report has assessed the aerodynamic characteristics of the Walker wingsail via a general study of the literature (section 2), a comparison of Walker experimental data with soft rig results (section 3) and a numerical study of the Walker and Boatek wingsail sections. The main conclusions are:

  • a sailing rig needs to be able to produce a high maximum lift coefficient, and to operate at high efficiency (lift-to-drag ratio);
  • the need for high maximum lift coefficient implies the use of multi-element sails;
  • multi-element wingsails can (and the Walker wingsail does) surpass soft rigs in both maximum lift coefficient and efficiency, but the weight penalty that they impose can result in a net detriment to boat performance at low wind speeds;
  • the Boatek wingsail is likely to be slightly (around 10%) more efficient than the Walker design; it probably also has an advantage (around 20%?) in maximum lift coefficient. These benefits are most likely due to the use of cambered sections, which is made possible by providing a mechanism for the sail to rotate through 180° each time the boat changes tack.

It is clear that the performance of any given rig is strongly dependent on its detailed design. However, for the purposes of comparison between different types, a summary of the 'typical' aerodynamic performance characteristics quoted in this report is given in the table below, which assesses sail performance in terms of the maximum lift coefficient, CLmax, and the maximum value of the lift-to-drag ratio, L/Dmax. The less reliable values are followed by a question mark.

soft, jib/sail
Walker wingsail
Boatek wingsail
> 3?
rigid, plain flap
> 10?
rigid, split flap
> 10?