Hobie 20 Mast Base Sheave (Block) for Main Halyard -- Replace with larger diameter block

My Hobie Main Halyard is the standard Hobie dimensions (D = 3/16"by 64ft Long), that is to say extremely thin to allow it to reside inside the mast going up and down without interference along any of it's length, while also being relatively strong, and it exits a 90 degree corner at the base of the mast around a sheave. This sheave is the pinch point when hoisting the sail, and if there is any cross wind or any excess friction in the sail track, the load on this component climbs greatly.

Typically, this delrin on delrin bearing sheave is used (29mm Harken Bullet Sheave #160), but I've noticed it worn or completely destroyed on a couple of Hobie 20's that I've encountered, and I decided to take action to prevent recurrence of failure on my boat.

As commented in the blue text-box above, the stock 29mm Bullet Sheave riding on Delrin internal balls burns out every 2-3 years or about 100 cycles.

Although pricey at about $33/piece at West Marine, I found that this 38mm wire sheave just barely fits with some very minor interference with the center bottom Cunningham Block which straps up from below and is pulled upward and out of the way when under any tension. The sheave cross-profile is design for wire, hence a much tigher radius, but it seems to fit snugly on the 3/16 rope halyard and the bigger diameter (38mm) translates into better pulling power in my tests so far. [Update 8/17: I've been using it now for 9+ months without too many issues -- it is crucial to keep the delrin spacers and sheave tight laterally so the line doesn't jump off the sheave while hoisting.]

The other option would have been to go with a solid delrin sheave, not spinning on internal delrin balls, but rather the through bolt itself. While likely stronger against all loading, this I felt would be a step backwards as the friction to spin it about the 1/4" bolt that secured it would have been far greater than that of the ball bearing versions. So I think my solution was a good improvement without many adverse trade-offs.

For reference, here is a link to all Harken "small boat" self-contained sheaves for your perusal: http://www.harken.com/productcategory.aspx?taxid=393

Burned out Delrin Sheavee