Gone to Pot

 I decided early on I wanted to "pot" most of the deck fasteners with epoxy to prevent moisture intrusion to the deck core. It's a process I've done a few times on previous boats that gives much peace of mind, since any failure of sealant simply results in leaks to the cabin instead of turning the deck to mush as well. Most of my previous experience was with balsa and foam cores, where I used a bent nail (as suggested by West System literature) to clear the core between the skins and make room for the epoxy. I quickly discovered this wasn't going to work on this boat due to the fact that the core material appears to be Masonite!? Some googling revealed Masonite was in fact used as a core material, most notably in the early versions of the venerable Alberg 30. I later found some sections, including the motor mount and the top of the coamings, are marine ply core. I searched for alternative methods and came across Rod Collins' excellent write-up at https://marinehowto.com/sealing-deck-penetrations-to-prevent-core-rot/. While it doesn't address Masonite (or even marine ply) directly, I wasn't previously aware of the dremel bit he recommended so I went out and bought one.

Unfortunately, even with the dremel bit, routing the core was tedious, noisy, and time-consuming. I even destroyed my old dremel in the process. After buying another and still struggling, I decided to give up and try a different approach. I never liked the idea of over-drilling for the same reasons Rod mentions, but I came up with an alternative that I feel better about. I used a step drill bit from underneath to produce a stepped, conical hole which should hopefully yield more surface and better bonding for the epoxy, while keeping more of the thicker top-skin intact.

 

Step-drilled holes

I did use Rod's suggestion for countersinking, which seems logical and was easy to do. I also purchased Bed-It butyl tape from his website to try. I've previously used either 3M 4200 or Life Calk/Life Seal to seal fasteners. I must admit, I found it a bit time-consuming to cover entire stanchion bases with butyl, so after the first few I switched to a hybrid approach: wrap the top of the fastener in butyl, then spread 4200 on the surrounding surface. The butyl works great for wrapping fasteners directly.

In the end, I did all the fasteners through cored sections this way, roughly 70 total. I also added 3mm thick G-10 backing plates to the bow cleat, winches, rudder gudgeons, and motor mount. Amazingly, the only existing backing plates were for the aft stanchions and backstay fitting; everything else was just washers. I strongly suspect the aft stanchion backing plates were added after a repair, quite possibly due to core rot.

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