@Jim Briggs wrote:
I presume you mean a purchase of 1:2 ie for every foot of halyard you pull, the spinnaker actually rises 2 feet ? Also, what is the best way to gain access the inside of the mast to install a block inside it?
Indeed a purchase that allows you to pull only half the length. I have made a quick sketch that (hopefully) shows how its done.
The knot (dot in the sketch) is outside the mast. The halyard goes from the knot through a small hole with a diameter slightly larger then the halyard diameter, down to a block and back up to the spi-sheave. Then a new line goes from the block down to the foot, over the sheave where the halyard used to be. Then you need to tweak the length of the halyard in such a way that the spinnaker can be hoisted fully with the block just above the sheave in the foot. This maximizes the halyard length and ensures the halyard is long enough to store the spinnaker and cleat the halyard near one of the shrouds. Provided the new control line has some excess length, maximizing the halyard length also allows it to be shortened when it starts to shows wear marks.
The hole that holds the bitter end is located a few inches above the hounds to avoid weakening the mast any further. There are enough holes as it is at the hounds. To mount the halyard it needs some diddling after the foot has been removed. Use the existing halyard to pull in a helper line. Other tools are an electricians spring or a bowden cable to thread a line through the mast. Some say a nylon fishing line with fishing lead attached works just as well, but I never mastered that technique. Use tape to connect the halyard to the fishing line, spring or bowden cable.