It was a Harken Magic Block system which went from 4:1 to 7:1 by hauling in until one stopper hit the block then releasing slightly and then rehauling. Seemed to work alright but was too long in total due to the internal cascade. We and I do say we ( we spent a bored morning at Mumbles trying to understand how it worked )never quite worked out how it did what it did.

On the basis that I couldn't get enough block spacing we converted it to a makeshift 6:1 hence the question as to get 7:1 will mean buying new triple blocks. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />