Camber Spar Dynarig
Hi Terry (Ancient Kayaker),
I can see from your contributions to this discussion and contributions to this other subject thread, ‘
Square Rig Variation’, that you have a great interest in this subject matter.
I do as well, but unfortunately at the moment I’m working on the opposite end of vessels…a propulsion drive leg design rather than the sailing rig
I knew this fellow Dave Bierig, a sailmaker in PA, who developed this Camberspar idea. It was right about the same time that Freedom boats were introducing their wishbone booms on their freestanding mast, and here was a concept that required only a half of a wishbone boom. It was contained in a pocket built into the sail as opposed to double arms ‘around’ (external) the sail.
I’ve often thought of other applications where this camberspar idea might be utilized, including
the mizzen sail and the inner foresail on my mast-aft concept. Perhaps it was this posting of yours #20;
…but I’m also thinking of having a double skin forming a full aerofoil profile which would be symmetrical on either tack and self-tacking. In my earlier adaptation of your concept I planned a one-piece sail with pockets for each yard instead of separate sail panels.
..that prompted me to think of possibilities of using the Camberspar concept on a Dynarig design. I have a bunch of ‘doodles’ on various napkins and pieces of paper, but I’ve never gone through a development process.
My basic thought was a round freestanding mast that has external tracks down either side 180 degrees apart. These tracks would allow the a ball-ended ‘camberspar yard’ to ride up and down the mast, and these camberspar yards (half yards really) would be able to rotate over 180 degrees in the horizontal from one camber of sail to the opposite camber. This rotation of the camberspar yard (better described as a ‘flop’ from one camber to the opposite) would occur within a pocket built into the sail panel. This sail panel pocket would be horizontal on its bottom edge such that the camberspar yard would rest in it at full camber when on either tack. The sail panel’s pocket would be exaggerated in dimension at its outer edge in order to allow the tip of the camberspar yard to flop over on the opposite tack (camber). Perhaps some sort of ‘leech line’ internal to the sail would be needed to facilitate the ‘flopping’ of the camberspar yards. Naturally you would want both ‘halfs’ of any one camberspar yard to rotate onto the new tack in unison, or you might end up with an ‘S’ shaped sail aerofoil rather than a full camber foil shaped sail.
That nice round mast might have two cambered panels bonded on either side, that project out at each end to form a small slot that allows the camberspar yard and its sail to exit the mast’s slot. These two panels would act to make the mast appear as an elliptical aerodynamic shape at the center of the cambered sail.
I know this is an incomplete thought process, but it was my idea for using the camberspar concept as a yard for the square sail ‘dynarig’ configuration. It harkens to your call for a “one piece sail with pockets for each yard instead of separate sail panels”, and could “form a full aerofoil profile on either tack” while requiring very little mast rotation.
(I'll try to add a sketch in the next few days when I get a chance)
