Purchase ratios

Have a look at the below picture;

The top system is the standard 4:1 purchase on the Musto Skiff, the blocks hook into two loops one each side of the sail (same as a 29er & 49er).

What is the purchase ratil of system A & B?

In in the case of B is the purchase ratio the same on starboard and port?

There must be some mechanics graducates out there ...

regards,

Rick

For the record I believe A= 8:1 & B=6:1 and that B offers the same advantage both sides.

See below;

But I am open to correction...

With B I think that you would have different loads going through each of the hooks which may give problems depending on how they attach to the sail.

How much space is there between the hooks and the deck and what sort of fittings are there on the deck to attach to?

6:1 is tricky if you want to get the tail out to both sides.

The only thing that I can think of to give you feed out to both sides is a straight strop from each hook to a moving tripple block in the center then double block at base of mast as a turning for the purchase giving the whole thing as a 6:1 and then two singles to take the line out to each side.

I think those ratios are correct. The advantage must be the same on both sides. It is the same bit of string and therefore the tension in it must be the same over its whole length.