THUNDERHEAD, today, once the rain stopped.

Nearly 1000 sq.ft. SA, the main looks like half of that, with a boom about 22' feet long. The forces involved are formidable. New ball bearing blocks made me think the arrangement was all new. Then I saw the old South Coast block(brown-50's,60's rigging), making the last turn to the self tailing winch. I'd bet this is the original mainsheet configuration.

Makes sense, THUNDERHEAD has a true dog house over the cockpit. Not a good place for a mainsheet.

No traveler nor is there a hydraulic vang(spruce spars). I would guess preventers and vangs are rigged when needed, looking at the 3 pair of self tailing winches per deck. The mainsheet was big, maybe 3/4 dia.