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The final version of the Junk Rig Glossary is now available and can be found under the Junk Information menu, or directly here.  This Glossary lists all the terms related to the junk rig, its implementation and use.

We were formed in the UK, and although our 'office' address and banking remains in the UK we are run by an increasingly international Committee via the Internet. A number of posts become vacant every year, at the AGM, so if you choose to join you could also put your name forward to help run the 'club'. It doesn't run itself. Our membership is now more than   50% outside the UK. Click the chart for detail.

August 2017 - Bunny Smith's Fenix

Group Capt. I.R. “Bunny” Smith was an early investigator of the windward performance of the junk rig. He proposed what he called the Insect Flight Theory - concerning insects that are, according to aerodynamic theory, incapable of flight, and yet they do it. He explained this by the presence on their wings of 'turbulators' - irregular surfaces generating vortices, accelerating air flow over the upper wing surface, reducing drag and producing low pressure and, thereby, lift.

During the early 90's Smith described experiments with his Sadler 26 Fenix, creating camber using flexible battens. The battens were 'fanned' at an increasing angle from luff to leech with increasing height up the sail, producing further camber by 'scalloping', controlled by adjustable leech lines. Secondary (keep) battens on the opposite side of the sail from the main battens acted as 'turbulators'.

Subsequently Fenix would point inside 40° on each tack, with improved speed. Some who sailed in Fenix before and after were convinced this was a huge step forward in the junk rig development. Smith designed a similar sail for the Vertue Jillie, whose owner was equally impressed. Smith was convinced that having battens (turbulators) on the leeward side of the sail on both tacks contributed significantly to the improvement. The advantages of camber-inducing flexible battens and the keep battens were later supported by wind tunnel experiments (with rather small scale models) by Victor Winterthun.

Others were sceptical, particularly of the Insect Flight Theory, observing that boats do not flap their wings. Alan Boswell was one such, having sailed in the modified Fenix and Jillie, and was convinced the improved performance was due to camber induced by leech lines and by flexible battens. He noted that performance improved only at wind speeds over 12kts., at which speed the batten sections chosen by Smith began to flex significantly. Smith rejected this analysis, wryly observing that the latest Boswell-designed sails looked very much like those of the modified Fenix, incorporating most of his improvements including the keep battens.

Whatever the truth of the matter, Smith's efforts and the undeniable improvements in performance he achieved led the committee of the JRA to vote funds to support the wind tunnel testing programme he had called for, to evaluate the aerodynamic principles of the junk rig and to assess his theory and results. They also helped to stimulate experimentation within the JRA over the next two decades.

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