Originally Posted by tommays
If you have straight spreaders on and older style mast then a back-stay failure is really BAD
... keel stepped or not.....
To figure the purchase advantage on a tackle you look at the number of moving parts... your pic looks like 8:1...cascade that with a two part and you have 16:1... another two part after than makes it 32:1 and so on.
You can get away with very small line and blocks as they share the load.. making the whole installation a little less bulky. But you should have a fixed strop parallel to the whole setup with its length set for the 'released' setting as a backup in case your tackle fails or is accidentally let run through.
The other thing to keep in mind is that you'll be pulling a lot of line through to make a small adjustment.. with the backstay on hard you'll have to figure a way to safely store the tail of the adjusting tackle.