Bottom Painting. The Good and the Bad
Wednesday June 2nd, 2010 (Simon) - Splashed the boat after a quick haulout for bottom paint and zincs. When whoever it was first put antifouling on the bottom, I don't think they prepped the hull properly. At any rate, several areas (notably the aft buttock sections and the turn of the bilge at the keel) have suffered from delamination of the bottom paint off the hull, leaving shiny gelcoat visible. I finally got annoyed and scraped back a lot of this to where the adhesion was somewhat better, then prepped the exposed gelcoat with light sanding and Interlux Fibreglass primer (YPA something-or-another) before putting on fresh bottom paint. This way, to the extent the boat has "repaired" patches in the bottom paint, at least the patches are a few large continuous areas, rather than dozens of little patches.
I also continued my battle with Krikkit's krazy keel. The boat likes to burn the paint off its keel, even though lead is supposed to be pretty much inert. It was terrible the first year -- the paint on the keel was what they call "sick," delaminating in big multi-coloured sections over some areas of the keel, while other sections had seawater in between the lead and the paint, which created pus-like white oxide under the paint. Yuck. I took pretty much the entire keel down to bare metal last year, except the sections that had fairing compound (mostly near the hull/keel joint). After all, fairing compound should form a pretty good barrier, right? I then put on five coats of Interlux 2000E epoxy barrier coat on the whole keel before bottom painting. Well guess what? This year most of the keel was mostly alright, except the sections with the fairing compound that I'd left in place last year had all blistered or delaminated. So I fixed those this year, taking them down to bare metal, smoothing out the imperfections (which the fairing compound had been covering) as best as possible with a scraper and rasp, and putting on three thick coats of Interlux 2000E (time was tight!). I feathered these new barrier coat patches into the existing 2000E. There were also several isolated dime-sized spots where last year's 2000E had let in water and created little pocks in the paint. Again, I scraped and sanded these spots out and reapplied 2000E, feathered it into the surrounding solid 2000E barrier coat.
I've never before heard of a lead keel being so "active." I wonder if our marina is particularly hot, or if there's some interaction going on between the lead keel and the copper in the bottom paint? Certainly when we first got the boat, it appeared they'd bottom painted straight on top of the lead, with maybe just a thin coat of some kind of primer. It also appears that one of the earliest bottom coats was some sort of hard, metallic, copper-coloured paint, almost like sprayed-on metal (damn hard to sand, too!) It was a fresh-water boat for the first several years, so they probably got away with it because of that. Some research on the web also turns up some newer (2004ish) Hunter 33s that have experienced similar problems (see http://archives.sailboatowners.com/pviewarch.htm?fno=9&sku=2007080172316.99&browse=T&g=%5Bg%5D&ptl=Corrosion%20on%20my%20Keel and click on the related photo link in the first post). In that case it seems they chalked it up to impurities in the lead, and the solution is to encapsulate the keel in 2000E, just like I've done (or have tried to do).
But at any rate, Krikkit is nice and slippery for now, at least ... we glided back into our slip, all the way down the slipway with the engine in neutral. Splendid!