Ericson 25, Deck Core Repair, Cabin Trunk, S/V Flibbertegibbet

Deck core repair work by Robert Slocum on Flibbertegibbet
Repairing rotten deck core on a fiberglass boat is one of the most unpleasant tasks that any owner can undertake. Deck core typically consists of balsa wood or plywood sandwiched between a top layer and a bottom layer of fiberglass. Almost all of the core of the Ericson 25 consists of balsa wood that is 3/8 inch thick. The fiberglass on either side of the core is between 1/8 and 1/4 inch thick. This combination of balsa and fiberglass is incredibly strong, as long as the balsa core is not compromised by rot. Deck core rot occurs whenever water seeps into the core through some penetration in the deck, usually through a bolt hole or screw hole beneath a piece of hardware. If you've read my article, "Deck Core Repair, Chain Locker," then you'll know that there are two different ways that you can tackle a deck core repair job. You can come in from the bottom, as I did on Oystercatcher, my Ericson 25, or you can come in from the top. Robert Slocum, who sails his Ericson 25, Flibbertegibbet, out of Lake Texoma, Texas, sent me some pictures of a major deck core repair job that he completed by coming in from the top.
Most of the rot was in the area forward of the companionway hatch
Robert reports that a previous owner had tried (and failed miserably) to accomplish a deck core repair job by coming in from the bottom. I was able to come in from the bottom on Oystercatcher, because I was working in the chain locker. This is one of the few areas of the boat where there is not a fiberglass hull liner. The hull liner is a two-part shell of sorts, which provides structural support to the boat, and which conceals the unsightly bare fiberglass of the hull and of the overhead. The hull liner is covered with glossy white gelcoat, which provides a bright and tidy appearance to the interior, especially when balanced with the generous portions of varnished mahogany throughout the boat.
While the hull liner does have its benefits, its also has its costs, especially when it comes to doing any work on the deck core. Within the galley, main salon, V-berth, and the head, it is impossible to access the underside of the deck without first cutting through the fiberglass hull liner (or more properly speaking, the head liner). Doing so, of course, means that the hull liner is forever damaged and you must take some action to conceal the hole, unless of course you're the type of person who is not bothered by the wretched appearance of a hack job. It's into the latter category that the previous owner of Robert Slocum's boat fell.
In the picture below we see the overhead of the main salon. The scars around the perimeter indicate the area of the cuts that the previous owner had made through the hull liner (head liner). Robert reports that the previous owner, after making the sloppy repair to the deck core, did not bother to permanently reinstall the fiberglass liner by glassing it into place. Instead, he simply stuck it up there and concealed the cut marks with pieces of wood trim. Robert speculates that the previous owner might not have wanted to glass the liner into place, because the sanding and fairing would have damaged the textured surface of the overhead. I should note that the textured surface to which Robert is referring is found on all Ericson 25s. It provides a matte finish to the overhead and thus reduces the glare from the gel coat.
Here is how Robert himself described the situation: "A previous owner attempted to fix the boat from the inside, and he never glassed it back in. He just screwed some trim pieces around the overhead where he had cut. This repair job [on the interior of the boat] completely failed. I thought it looked awful, so I ground it all out, re-glassed [the liner], and faired it back in. There was no end to the awful sanding dust falling on my head. I assume the logic was that the previous owner didn't want to mess with the texture [of the head liner]. I don't know."
Robert did not indicate to me whether he concealed his glass work on the interior of the boat with his own wooden trim pieces, but I cannot imagine, given his concern for the appearance of his boat, that he did not do so.

Let's now consider Robert's solution to the problem of the deck core rot. Having re-glassed the head liner into place, Robert supported the head liner with a pole and then cut into the deck from the top. This pole was necessary to prevent any sagging while he worked from above.
One would think that the deck core rot originated at the point where the winch was joined to the deck. Notice in the picture below the six holes, which form a circle (not far from the pole). On some Ericson 25s (but not all) there is a winch in this location, which serves to raise and lower the centerboard.
Concerning the origin of the rot and his approach to the repairs, Robert says the following: "I went in from the topside. That way I could brace the ceiling from below, while setting it up, and gravity was my friend. What I found was random rotted out plywood that had completely failed and swelled. I assume this was the previous owner's fix. I ground it all out clean, and went back in with end grain balsa and liberal amounts of West Systems epoxy. I put several laminates of glass over the top of the repair job, and I spent time fairing the glass all back in around the perimeter. [In place of the original textured, non-slip deck], I went back with kiwi grip after I painted her. So far, she's holding up fine. I'm still not 100 percent sure what caused the softening. Weirdly, the area around the winch was fairly sound. The worst softening was between the companionway hatch and the winch, and along the sides where the hatch rails run. This is all fairly elevated, but I suspect that to be the culprit. Everything got re-bedded anyway after painting."
Doing a deck core repair project from the top side of the deck is, as Robert suggested, much easier, since gravity works with you instead of against you. There is, though, a downside to this approach; after all is said and done, you must start yet another project - that of fairing and sanding and priming and painting the deck. Robert, though, appears to have approached this project with the right frame of mind.
He would later, in a separate project, not only paint the hull, but also apply an epoxy barrier coat and an anti-fouling paint to the bottom. I would say that Robert did a fantastic job bringing his boat back up to speed.
This ends this posting on the deck core repair job that Robert Slocum completed on the cabin trunk of Flibbertegibbet, his Ericson 25.

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