Size of the blocks: how important is it?


Active Member
Thread starter #1
Looking at Laser pics of the era behind us, I get the impression that all blocks were really tiny. Nowadays, I see boats with Harken's 29mm blocks. Would you consider using bigger blocks an advantage? Smoother running is the first (and only) thing that springs to mind.

Your opinion / experience?



Well-Known Member
To answer the title question: not very. Of course, the larger the radius of a sheave is, the less friction there is. Same with thinner rope - a large part of the friction in a purchase system comes from within the lines, so the less sharp the turns are, the better.

In practice, the difference isn't noticeable, and you probably wouldn't find much of one in a blinded test. The trend is favouring 29/30 mm blocks instead of 16 to 20 mm, but I think that's more of a fad than a conscious logical choice. I personally prefer the compactness of the smaller sizes.



Former ISAF Laser Measurer
Totally agree LaLi. I'd go one step further and suggest that under signicant load (vang for sure) there is minimal difference in friction of a non ball bearing block and a ball bearing block.