Masthead sheave

[abyssal]

Does anyone know the outside diameter, width and pin hole width of the 310 masthead sheave for the jib?

 

[valcour]

OD=3 3/16"; ID=1/2" Width 3/4"; 2 15/32 diameter where rope runs. These came out of hull#218 (2003) with a regular slab reefing main.

 

[abyssal]

Did you need to bring down your mast to do the replacement, as it appears from the photo that your mast is down. Could the sheave have been replaced without unstepping the mast if you had a high-lift or other way to get to the top?

 

[valcour]

Pulled the mast the first winter after I bought her because halyards would not run free...turns out here were four twists of internal jib halyard around each other and main inside the mast making the friction. Why do you want to replace the sheave? The only way to do it with the mast stepped is to remove the forestay and backstay. You would be relying on just the forward and aft lowers for mast stability in that direction, and would need a high reach (halyards can't be used to haul up, and you will have to support the slackened forestay once you get up there) to disconnect the masthead fitting. Could possibly be done on the hard on a calm day, but risky if you can't put back together the same day. I replaced the sheaves while it was down, but the real problem for me was the twists in halyards when the boat was initially commissioned.