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Originally Posted by sailingdog
Sheaves used for rope generally have a u-shaped profile to the groove, while sheaves for wire generally have a v-shaped profile to the groove. While you can sometimes use v-shaped wire sheaves on rope, it will tend to cause the rope to wear through faster than if you had the proper sheaves.
You should also inspect your sheaves and boxes for scores, rough spots, and sharp edges. Any of these will damage your new rope halyards.
When sizing your halyard using Novabraid Polyspec
you need to go by core diameter, outside diameter. The price compared to Spec-12 will be comparable.