weight on main sheave

[Tony]

I've just bought a west marine bosun chair and will plan on going up the mast for some work over the weekend. I replaced one halyard with a new line to make sure that there are no surprises given that the one line that I have is pretty old. I've since started thinking about the sheeve mechanism on the top of the mast - how can I tell if the block and sheeve will be able to support a 180lb weight? My halyard runs inside the mast and comes out of the mast on top and right above the moom on the side - someone mentioned that if the block or sheeve breaks under load the halyard holding me will break the fall since it runs out of the mast. Is this thinking correct, or will I keep falling all the way down

 

[bob Gorman]

Safe but stuck

If the sheave pin or block breaks the halyard would hang on the end of the mast extrusion. That would hold you stationary, but would be difficult to lower you to the deck with the friction of the halyard rubbing on the mast edge. However the pin should be stainless steel and the chances of it being corroded are slim, the block is probably nylon and could be brittle but the chances of a complete failure are also slim. My guess if that if you were to have a problem it would occur before you get to the top, so your odds seem good!

 

[Seattle Scott]

Tony always have a back up

either another halyard tied into the chair or a line taken around the mast,with a girth hitch or prussik knot. I don't just trust the chair, I use a climber's harness when sitting in the chair. If someone is cranking you up, ask yourself what will happen to you when the "cranker" gets stung in the eye by a bee and lets go of the line.

 

[Don S/V ILLusion]

Tony

If I understand correctly, you don't have an existing halyard to which you can attach the new line to pull through?If you do not, people have successfully installed a new line by dropping a small chain or the bead chain used as ceiling fan chain which may have sufficient weight to drop past any obstructions.

 

[Seattle Scott]

Bicycle chain

sewed on to end of halyard, heavy and flexable for fishing it out at the bottom. Glad to hear you are staying safe.