To be really pedantic but to try and clarify this issue . .
It's a basic rule of pulley systems, if you have 15:1 system, to move the load 1 cm, you have to move the other end of the system by 15 cm no matter how you arrange the pulleys and for a 16:1 system . . etc etc
However, as we set these systems up, the limiting factor is when you put in a cascade or even a partial cascade system which is
when you really run out of travel, and I agree with John, the limiting factor is the distance between the base of the mast and the turning block at the shroud plate.
If you take a typical 16:1 system with 2:1 above the deck and a 8:1 cascade to the mast base and assume there is 1000mm between the mast base and the turning block at the deck. The 8:1 has three blocks in the system but I can only pull 2000mm
of rope out until it becomes block to block, The last block below deck has only moved 250mm so the shroud has only moved 125 mm, which doesn't allow the boom to square off very much.
If I now put a 4:1 on the end of a 2:1 below deck with the 2:1 above (still 16:1), I can pull 4000mm of rope before it goes block to block which means that the shroud has now moved 250 mm. So I have double the movement at the shroud but at the expense of twice the amount of rope round my feet! Not a question of how much purchase there is above the deck but how it
is arranged below deck.
With a 5:1 below deck and a 3:1 above (=15:1) I can move the shroud 330mm but at the expense of 5m of rope
pulled but which probably gives you all the slack you would (ever) want.
So you would of thought that shroud tracks would have a distinct advantage, if only in the amount of rope to be shifted at the corners.
I've gone for a 5:1 and 3:1 system without using the full potential of travel but if I find I'm winding in arm fulls of rope at the bottom mark, I might go tracks yet.
If you have a cascade kicking strap system and find you're running out of travel, same principle applies, try replacing the last block of the cascade with a 4:1 instead of a 2:1 system
It's a basic rule of pulley systems, if you have 15:1 system, to move the load 1 cm, you have to move the other end of the system by 15 cm no matter how you arrange the pulleys and for a 16:1 system . . etc etc
However, as we set these systems up, the limiting factor is when you put in a cascade or even a partial cascade system which is
when you really run out of travel, and I agree with John, the limiting factor is the distance between the base of the mast and the turning block at the shroud plate.
If you take a typical 16:1 system with 2:1 above the deck and a 8:1 cascade to the mast base and assume there is 1000mm between the mast base and the turning block at the deck. The 8:1 has three blocks in the system but I can only pull 2000mm
of rope out until it becomes block to block, The last block below deck has only moved 250mm so the shroud has only moved 125 mm, which doesn't allow the boom to square off very much.
If I now put a 4:1 on the end of a 2:1 below deck with the 2:1 above (still 16:1), I can pull 4000mm of rope before it goes block to block which means that the shroud has now moved 250 mm. So I have double the movement at the shroud but at the expense of twice the amount of rope round my feet! Not a question of how much purchase there is above the deck but how it
is arranged below deck.
With a 5:1 below deck and a 3:1 above (=15:1) I can move the shroud 330mm but at the expense of 5m of rope
pulled but which probably gives you all the slack you would (ever) want.
So you would of thought that shroud tracks would have a distinct advantage, if only in the amount of rope to be shifted at the corners.
I've gone for a 5:1 and 3:1 system without using the full potential of travel but if I find I'm winding in arm fulls of rope at the bottom mark, I might go tracks yet.
If you have a cascade kicking strap system and find you're running out of travel, same principle applies, try replacing the last block of the cascade with a 4:1 instead of a 2:1 system