Mast head design flaw

[gareth harris]

The sheaves on my masthead do not extend out past the sides of the mast, and over the last 29 years the wire halyards have carved right through. The sheaves are mounted on pins that extend through the masthead, but have been drilled too close together.
Has anyone encountered this and found the best solution? (Or have I just got a lucky one?) Either new holes need to be drilled, or a sheave arrangement mounted inside the top of the mast that mounts the sheaves internally.
Any recommendations on how to drill the holes through the mast, since they need to be perfectly perpendicular?
Gareth

 

[Loren Beach]

Given the age of the spar, perhaps this should be your next big "winter project." Remove the spar, strip the hardware, repaint with LPU, put in new wiring, run new (low-stretch line) halyards, and..... have a new masthead fitting welded up with the sheaves sized and placed where they belong. There is also the off-chance that a search of the Kenyon site would turn up a new fitting, but your spar may be from a sparmaker long gone from the market. I know this is a lot of work and a bit of money, as well. If the standing rigging is over 10 or 12 years old, it's time to replace the wires anyway, imho. This way you can really check the spreader bases, the mast base, etc, etc.
If there is some ages-old coax in there, replace it with new low-loss stuff -- and talk to boats you've been missing!
Not the solution you probably wanted... but that's my take on it.
Loren in Portland, OR
'88 Olson 34, and scheduling new standing rigging for next season, so the rigging will keep standing...

 

[Bill Robbins]

I have an 1970 E-35. Five months ago I took down the mast, stripped Everything off, repainted and reaffixed everything. I also replaced the spreaders.
I needed to replace my sheaves. I had wire on rope halyards which wore down the groove deep enough to allow the wire to start rubbing on the spar as it left the head. This was not a design flaw in this case, but rather the sheave simply loosing its diameter as the wire carved deeper towards the center of the sheave.
To fix this I replaced the sheaves and went with all rope halyards. I could find sheaves that had the correct overall diameter and thickness, but not the correct pin diameter. I purchased the sheave that was closest in size and had the boat yard's machine shop press in a bushing to accommodate my existing pin. This worked well and was easy to do.
Look carefully to see if this is the case with your situation. I am really glad I did this job. It was really rewarding and has given my much peace of mind when I am sailing with the family.
If you have any more questions please contact me. It is still fresh in my mind!
Good luck.