Old as Dirt!
On the older Cal's (we owned a '76 Cal 2-29 for 20+ years), the foot of the sail was attached to the boom. With this arrangement, the boom was allowed to rotate about a pin to align its vertical axis with the surface of the sail to eliminate torsional shear in the boom at the goose neck. A vang could be connected to a hooped bail fitting. To employ a solid vang, one would simply use a fitting plate on the underside of the boom that was oriented transversely rather than along the length-wise axis with a pinned connection.ok. here is an odd question. the boom on my cal 27 spins around the gooseneck fitting. i think it's not a roller furling boom, though. no crank and the boom isn't round. in order to hook up the boom kicker, i have to secure the boom with an additional kit to keep it from rotating.
never had a sailboat with a boom that rotates, that way. never read anything about booms that do that, except for roller reefing booms. very curious as to what the purpose was for that design. seems to me, it wold be easier to produce without the rotating feature. so, it must have a purpose. anyone have an answer so i can stop wondering?