After her restoration Shamrock's running rigging mainsheet consisted of 4 cm (1.5 in) manila rope with a 23 cm (9 in) double block and a 23 cm (9 in) single block with becket and a bulls-eye.
During the 1980s’ this was changed to two 23 cm (9 in) triple blocks, one with a becket and the bulls-eye resulting in more rope being required and such a complicated layout that the crew would have to use a model of the blocks to assist in the mainsheet reeving procedure. When not in use long bights of mainsheet rope were draped over the mizzen sail cover.
Shamrock rigged with triple blocks.
Model triple block.
As the manila running rigging ropes are in the process of being replaced with Polyhemp, the opportunity is being taken to simplify the mainsheet by using only two 23 cm (9 in) double blocks, one with a becket and no bulls-eye which also means one of the deck eyebolts can be removed and a lot less rope is required. This layout also enables greater control of the main sheet with the bight running from the lower block and making it easier to deploy the mainsail to starboard or port. Replacement blocks have already been selected and are in the process of being renovated.