Modern sailplans, with their high halyard loads, impose unwanted compression on masts. To counter this, many grand prix boats use mechanical halyard locks to confine the load to the top of the spar, rather than carrying it length of the halyard. However, these systems are typically too bulky and complicated to fit in a sportboat’s spindly mast.
To solve this problem the C&C 30 design team decided to employ a pair of narrow, Ronstan Constrictor rope clutches, which use a tubular fabric “sock” (think Chinese finger cuffs), as opposed metal teeth to secure the line.
Fitted inside the mast section just below the main and jib halyard sheaves, the constrictors are released with a pair of thin Dyneema lines that exit the mast around deck level. A pair of shock cords keeps the socks stretched out when the release lines are eased, so that the constrictors will grip hard and fast, ensuring the sails sit squarely on their datum lines after being raised.