Capt. Neal® wrote:

... but when the outhaul is tensioned, the shelf foot closes and the
bolt rope in the boom tends to flatten the sail.

Once again, a self-proclaimed old salt embarrasses himself by inviting a
sweet, innocent, fresh-faced n00b to provide an elementary lecture in the
dynamics of the outhaul on a shelf-footed main...

The sail is flattened under outhaul tension due to the direct pull between
tack and clew. When thus tensioned, the surplus material in the shelf foot
sags. Since the shelf is sagging, it imparts no downward pull on the main -
it is slack cloth between the bolt rope and the sail, proper.


--
Wally
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www.wally.myby.co.uk