[ backstory ] Yesterday I finally, and sadly, put my Matilda http://davesbrain.livejournal.com/315479.html" [Broken] to bed for the winter. I want to lift her off her trailer so I can work on her hull. She's 1500lbs. The barn she's sleeping in has a massive travelling lift system (18" steel I-beam on a track) but no winch. I can't afford to rent a winch for the whole time I have it hanging. (Yes, I know I can build a cradle to sit her on, but...) So I've been thinking about building a manual winch using block & tackle. [ /backstory ] So I started wondering how big a block & tackle system I'd need. A rope with 1500lb test? Question 1 : Correct me if I'm wrong: for a block & tackle with, say 4:1, my line's strength need only be 1500/4=375lbs, right? What if my block & tackle were 100:1? I'd only need a line that could support 15lbs. I know that 100 pulleys may sound like a lot but each wheel would only have to support 15lbs. so they could be compact. What if I had 500:1? 3lb test line. I could lift my boat off its trailer with sewing thread tied to my pinkie! (Of course, to lift it a mere foot, I'd have to run a tenth of a mile away!) Question 2 : Is there a flaw in my logic? I'm thinking the friction might do me in, but I'm also thinking that the friction would be distributed among the 500 strands so it shouldn't be a problem. Or is the friction cumulative?