I've got to make a decision on this:
Do I fill the joint with 2-part polysulfide sealant, as recommended in almost all references?
Or do I use fiberglass and resin and make the joint solid?

Bud Taplin, the Westsail Guru of Record, says polysulfide.

Two Westsail owners have gone the FRP route. But they have not put many miles/years on that repair and the longevity of the joint is not known.

I have about 20-feet of the teak caprail off. Under the rail was a disgusting pile of crumbling, wet caulk and sealant. This is what it looked like before I started scraping it out:


After I'd cleaned that out I found a deep groove that should really be filled with poly. But it will take about 1.5 gal to do the whole joint.


The Engineering Drawings of the hull-deck joint look like this:



On the left is "as designed" and on the right is my alteration showing "as built." Note the void under the caprail?



The forward end of the caprail, as it drops off the high bulwarks down to the bow, was glued to the chine rub rail and the two came off as a unit (for the first 3-feet or so).

Seen here on my dockbox with the bow end toward the left. More holes to seal.

I've found that 2-part concrete expansion joint compound is the exact same stuff that is sold in marine chandleries but it's less expensive when purchased at a hardware store. And I'm going to need a lot of the goo to fill this gap properly.

I'm leaning toward the poly. Faster, easier to work with, more forgiving, proven track record, highly recommended..... Yeah, I'll probably go that route. But then again....