CLEW RADIAL
THE CLEW RADIAL APPROACH - RACING, CLUB RACING AND CRUISING SAILS
BACKGROUND:
Sobstad’s adopting of the clew radial sail skin construct has its origins in a long ago photo of the winning Olympic Flying Dutchman from the 1963 World Championship regatta in St. Petersburg, FL. While commencing what was to be a nine-year effort in Finn sailing, I would study and re-study that photo and the radially designed genoa aboard this winning boat. Years later, during the 1971 Soling Worlds in Oyster Bay, while staying at the same home as the skipper of that Flying Dutchman, we found ourselves talking well into the night about sails and sailing. We had raced against each other in the ’69 Finn Worlds in Bermuda and consequently had a lot to talk about. When I asked him about the Flying Dutchman genoa, he stated with conviction: “You know, that was the best genoa we ever had.” Later, in 2002, as Sobstad and Elvstrom Sails embarked upon a joint venture and began an innovative sail design software project, the use of the fundamentals observed within that Flying Dutchman genoa crossed my mind. Sobstad’s new laminated racing sails eventually became the twenty-first century’s illustration of that very 1963 genoa.
REASONING:
RESULTS:
On-the-water performance. Early versions of the Sobstad clew radial sail were put to rigorous test – without need for re-adjustment or “re-cutting” whatsoever – aboard Sobstad’s own Cookson Farr 40. They performed remarkably and contributed to a class victory in the very windy 2006 Key West Race Week chapter. Since then, Sobstad’s clew radial racing sails have performed beautifully within the myriad of racing venues in the United States, Canada, and Western Europe.
CLEW RADIAL VS. TRI-RADIAL CONCEPTS
A substantial number of sails on the water – including sails for racing, club racing, and cruising utilities – conform to what is colloquially referred to as the tri-radial type. Here an attempt is made to enable the sail skin to mimic an imaginary model which sees all three corners confronting forces of a purely radial nature. A differing description of each corner’s relationship to forces has been set forth above. Additionally, the tri-radial scheme apparently assumes the presence of significant force running in a vertical manner and parallel to the leading edge. Clew radial thinking and emphasis dismisses the presence of such a force and instead assumes that residual forces – more horizontal in direction – which have originated at the very clew, intersect the leading edge along its total length. Finally, the all-important concept of preservation of the uninterrupted definition of the clew radial’s structural yarns is absent from the tri-radial’s inherent nature. In short, the clew radial approach is sounder of theory and better equipped to successfully accomplish the task of force distribution.
THE CRUISING APPLICATION
There is no doubt but that racing success validates a specific sail theory. Most sails, however, are assigned missions – club racing, day sailing, coastal cruising ones – which don’t involve intense racing and hence reflect a specific set of imperatives and necessities.
Most racing sail skins are composite in nature, in that they are comprised of several components: structural yarns, polyester or high tensile yarns, adhesive. Most sail skins for informal racing, day-sailing, and coastal cruising applications are comprised of a woven polyester material which, in turn, is finished with a coating or impregnation which lends stability to the woven material.
The clew radial concept is every bit as necessary to the fashioning of the woven sail skin for the club racing, day-sailing, coastal cruising sail skin as it is for the flat-out racing sail skin. On occasion, if a sail plan is adequately small, and price the overriding concern, a cross-cut sail skin with transverse seams can be considered. The great majority of Sobstad mainsails and headsails for club racing, day-sailing, and coastal cruising missions are clearly of the clew radial type. It is altogether true, therefore, that this governing approach ensures that sails with woven sail skins of the clew radial type will project that great unblemished and three-dimensional ‘brand new’ sail appearance season after season. The perfect radially-intensive structural scheme distributes forces in the correct manner, and the skin material’s rock solid rigidity keeps that scheme in its ideal and intended position.
Sobstad’s adopting of the clew radial sail skin construct has its origins in a long ago photo of the winning Olympic Flying Dutchman from the 1963 World Championship regatta in St. Petersburg, FL. While commencing what was to be a nine-year effort in Finn sailing, I would study and re-study that photo and the radially designed genoa aboard this winning boat. Years later, during the 1971 Soling Worlds in Oyster Bay, while staying at the same home as the skipper of that Flying Dutchman, we found ourselves talking well into the night about sails and sailing. We had raced against each other in the ’69 Finn Worlds in Bermuda and consequently had a lot to talk about. When I asked him about the Flying Dutchman genoa, he stated with conviction: “You know, that was the best genoa we ever had.” Later, in 2002, as Sobstad and Elvstrom Sails embarked upon a joint venture and began an innovative sail design software project, the use of the fundamentals observed within that Flying Dutchman genoa crossed my mind. Sobstad’s new laminated racing sails eventually became the twenty-first century’s illustration of that very 1963 genoa.
REASONING:
- Mainsail and headsail clews are the only corners (the mainsail is essentially a headsail set with an out-rigger – the boom) floating in space. Forces surrounding mainsail heads and tacks are defined, to a certain extent, by the fact that their leading edges are attached to either mast or forestay. And these attachments diminish and attenuate the purely radial definitions of force which are so often, I think, incorrectly assigned to them.
- A famous author of one of the sail industry’s first and most comprehensive sail design programs once said to me: “Peter, you are right; forces flow along the leech and forward to the leading edge of the sail.”
- The somewhat infrequency of horizontal seam - which is subjected to constant and consequential shearing force - failure notwithstanding, the essence of the clew radial sail avoids glaring seam failure vulnerability and compromise. Because of their size, sails – and even small sails, as manufactured products go – are comprised of panels. But unlike those within other panel arrangements, Sobstad’s clew radial seams illustrate widths which are correctly defined by their lengths. Put another way, forces travel ALONG the seams, rather than ACROSS them. Consequently, structural yarns within the clew radial sail are continuous and uninterrupted. And as far as we at Sobstad are concerned, this defining characteristic should never be compromised. Within Sobstad’s clew radial sail there is a pronounced and beautiful three-dimensional form. This form’s definition, though, is achieved without the traditional manipulating of transverse seams and without the severing of structural yarns.
RESULTS:
On-the-water performance. Early versions of the Sobstad clew radial sail were put to rigorous test – without need for re-adjustment or “re-cutting” whatsoever – aboard Sobstad’s own Cookson Farr 40. They performed remarkably and contributed to a class victory in the very windy 2006 Key West Race Week chapter. Since then, Sobstad’s clew radial racing sails have performed beautifully within the myriad of racing venues in the United States, Canada, and Western Europe.
CLEW RADIAL VS. TRI-RADIAL CONCEPTS
A substantial number of sails on the water – including sails for racing, club racing, and cruising utilities – conform to what is colloquially referred to as the tri-radial type. Here an attempt is made to enable the sail skin to mimic an imaginary model which sees all three corners confronting forces of a purely radial nature. A differing description of each corner’s relationship to forces has been set forth above. Additionally, the tri-radial scheme apparently assumes the presence of significant force running in a vertical manner and parallel to the leading edge. Clew radial thinking and emphasis dismisses the presence of such a force and instead assumes that residual forces – more horizontal in direction – which have originated at the very clew, intersect the leading edge along its total length. Finally, the all-important concept of preservation of the uninterrupted definition of the clew radial’s structural yarns is absent from the tri-radial’s inherent nature. In short, the clew radial approach is sounder of theory and better equipped to successfully accomplish the task of force distribution.
THE CRUISING APPLICATION
There is no doubt but that racing success validates a specific sail theory. Most sails, however, are assigned missions – club racing, day sailing, coastal cruising ones – which don’t involve intense racing and hence reflect a specific set of imperatives and necessities.
Most racing sail skins are composite in nature, in that they are comprised of several components: structural yarns, polyester or high tensile yarns, adhesive. Most sail skins for informal racing, day-sailing, and coastal cruising applications are comprised of a woven polyester material which, in turn, is finished with a coating or impregnation which lends stability to the woven material.
The clew radial concept is every bit as necessary to the fashioning of the woven sail skin for the club racing, day-sailing, coastal cruising sail skin as it is for the flat-out racing sail skin. On occasion, if a sail plan is adequately small, and price the overriding concern, a cross-cut sail skin with transverse seams can be considered. The great majority of Sobstad mainsails and headsails for club racing, day-sailing, and coastal cruising missions are clearly of the clew radial type. It is altogether true, therefore, that this governing approach ensures that sails with woven sail skins of the clew radial type will project that great unblemished and three-dimensional ‘brand new’ sail appearance season after season. The perfect radially-intensive structural scheme distributes forces in the correct manner, and the skin material’s rock solid rigidity keeps that scheme in its ideal and intended position.