Some of you may recall when Bob noticed a crack in a photo of my fairlead collar. That was almost a year ago, I think. I talked to Mike Quill about it and he said it would be OK to sail it like that for a while as long as I didn’t push the rig hard. So I’ve been raising the sail just until I saw the tack shackle start to lift and stopping there. That left the luff a bit loose and I’ve been happy that the boat actually sailed pretty nicely even like that.
I bought a new fairlead collar and in December I started to replace it, only to find some corrosion beneath the tack collar. There were a few paint bubbles visible with the collar on, but it didn’t look bad at all until I removed that collar. After extensive consultations with Mike and with Klacko Spars, it turned out that the corrosion was well within limits. (The wall thickness of the mast is 1/4" in this area and the corrosion was mostly just superficial.) So Mike advised me on the repairs.
I first sandblasted the corrosion and then treated it with a chemical from Star Brite. (Sorry, I forgot the name.) Then I primed with an aluminum primer, an epoxy primer and painted with two-part polyurethane - all from Interlux. I put the old tack collar back on with new neoprene beneath it, installed the new fairlead collar with a dab of Sikaflex on the “ears” to prevent twisting, and put on some new mast bands with neoprene beneath them.
I did all of this with the mast up, so didn’t paint anything above about 7’ off the deck. But that lower 7’ looks pretty good now. 
Yesterday morning a friend and I put the sail back on and took it out for a trial. I raised the sail all the way up and tightened the luff. It was a breezy day and we hit 8kts (GPS) within a few minutes of raising the sail. That’s a full knot more than the best I’ve ever been able to manage. I de-powered a bit because my friend’s wife’s eyes were getting too big, but we sailed for a few hours, rarely getting below 6.5kts. It was a very brisk and enjoyable sensation for a change, rather than worrying about the cracked fairlead collar. I’m not a racer, but the improved performance tells me that the boat can now sail correctly.
Then I had to dock the giant windvane in my downwind slip in all that wind. I didn’t hit or damage anything, but it took two tries and was not one of my finest moments. I am moving to an upwind slip on March 2nd. Hopefully that will be better.
The tack collar had a rotted and crumbling piece of red rubber of some sort beneath it when I took it off. According to Klacko, this allowed salt water to get down in there and led to the hidden corrosion, made worse by the galvanic reaction between the aluminum and the stainless. I used neoprene when I put the collar back on. (Solid sheet, not foam.) The collar fits tight and this should keep salt water out from between it and the mast. It will also protect the paint and keep the two metals apart - as long as it is in good condition. I intend to remove the tack collar occasionally, clean out any salt that manages to get in there and replace with fresh neoprene.
This has been grueling and a bit scary until I understood everything. I’m sure the old timers here know it, but for everyone else: keep a close eye on the various bands and collars that wrap around your mast. If you see even the tiniest bubble of corrosion around an edge, or if the padding beneath the collar looks dried out or worn, take it seriously. I caught mine before the damage was too serious, but during one of our consultations, Mike Quill sent me a photo of a mast that broke off due to corrosion beneath the tack collar.