You've actually got closer to a 3:1 purchase, rather than just a 2:1. If the
lines came straight down to a block with cam
cleat at the transom rather than further forward, it'd clearly be a 3:1 purchase, but since it comes forward a bit, you're losing some leverage, as the lever arm is shorter compared to the other
lines.
Basically, to figure out the purchase, you need to look at how many
lines are attached to the moving part of the tackle, which is the boom in this case. There are three
lines... so the purchase is almost 3:1.
See the diagram here:
Of course, the diagram in question is actually upside down for our purposes... since the boom is pulling away from the cockpit. Of course, another way to measure it is to see how much the boom moves when you haul in 3' of line. If it moves about a foot, it is 3:1, if it moves about 18", it is a 2:1.
__________________
Sailingdog
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Telstar 28
New England
You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.
—Cpt. Mal Reynolds, Serenity (edited)
If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts..
Still—DON'T READ THAT POST AGAIN.