Companionway Hatch, Construction, Part III

The fillets await Sanding
Part III: Prep Work for Finish Coatings

In the third part of this four-part article on the construction of a new companionway hatch for the Ericson 25, I illustrate, through many pictures, the work I completed in preparation for the application of the finish coatings. This prep work involved the sanding of the fillets, the planing of the port and starboard sides of the frame, and finally, the paying of the seams with black polysulfide.

Section 1: Sanding the Fillets

The sanding of the fillets was tedious, but then again isn't any sanding job this way, especially when it involved epoxy? You just gotta do it.

The Frame, Standing on End, awaits Planing

Section 2: Planing and Sanding the Hatch to Size

Before going in further, I decided it would be a good idea to see if the frame would fit underneath the bridge for the traveler. It's a good thing I did. I had made lots of measurements prior to the construction of the frame, but of course things will shift around just a little during the cutting and the assembly of any wooden pieces. And besides, during the measuring process, it was hard to judge with great precision the clearance I would need, because I was dealing with a plywood mock-up. As it turned out, the actual frame could hardly fit beneath the bridge on the port and starboard sides. It needed to be able to slide freely beneath the bridge. Fortunately, I had plenty of material to spare on the sides of the frames. You'll recall that I constructed the frame out of 5/4 inch mahogany. I ended up planing about 1/4 inch off of the port and starboard sides. This left me with 4/4 material, in other words, 1 inch of material on each side. It was nice to have plenty to spare.

You might have noticed that in these pictures there is no longer any epoxy coating that is visible on any part of the exterior of the hatch. You'll recall that in the previous posting I described how I epoxy coated the entire thing to protect it from the elements. As time went along, I began to worry about how the epoxy might be damaged from UV radiation, since I would not be painting this hatch, but instead varnishing it. I had read and I had heard from others that its better to use simply varnish as the protective coating rather than an epoxy and varnish combination. Sure, varnish must be maintained, but its easier to maintain varnish if it doesn't have an epoxy coating beneath it that is failing.
As I have said elsewhere, sanding epoxy is like sanding concrete. This is even more true when it comes to sanding mahogany with epoxy on top of it. Do you see that 40 grit paper below? You better buy a bunch of that stuff if you ever work with mahogany. The other grades were simply for finishing the hash off and making it nice and smooth.
One last thing I did before paying the seams was to inject thickened epoxy into any little crack I could find in the joint between the frame and the shell. I wanted to make sure that if the varnish failed and the black polysulfide sealant failed, the water could not get into the hatch.
Section 3: Paying the Seams

In this section I describe the process by which I paid the seams with black polysulfide caulk. This part of the project itself required some prep work. I had decided to use Boatlife brand Life-Caulk. I had heard a lot about this product, and besides, the company was based here in Charleston, so I figured I could get plenty of help if I needed it. As it turned out, I did need some help, and the owner of the company herself not only returned my call, but gave me lots of good advice. She said that lots of people use Life-Caulk to pay the seams of hatches. She said, though, that some people neglect an important step - the application of a bond-breaker at the bottom of the seam. The bond-breaker, at the bottom of the seam, prevents the Life-Caulk from forming a bond with the substrate, in other words, the shell of the hatch. You do indeed want the Life-Caulk to form bonds with the sides of the mahogany planks, in other words, the sides of the seam, but you don't want it form a bond at the bottom. The reason? Being free from the bottom, the Life-Caulk can expand and contract as the mahogany planks expand and contract during different weather conditions.

The owner said that here company sold a bond-breaker product, but she said some people opt to use any number of things, for example, strips of paper, or even magnetic tape from old cassette tapes. I appreciated her candor, thanked her for her help, and then went on about my business.

I experimented with several different bond-breakers, some natural, but I eventually settled on strips of plastic. I was a little concerned about using plastic, since the Boatlife website, and Don Casey, This Old Boat, said that polysulfide would cause plastic to deteriorate. From what I could gather, however, the thrust of these warnings was that you should not use polysulfide to seal plastic parts. I wasn't sealing parts. In fact, I was trying to prevent any sealing from taking place. Besides, I figured that if the owner had told me that people had used cassette tape, which itself is plastic, as a bond-breaker, then I was okay.

Once I had it all taped-up and ready to go, I pulled out the Life-Caulk. I had no idea at this point how much I would need. For this reason, I had only purchased one tube.
One tube only filled five seams. I've done a lot of caulking in my time, but it took me a while to get the hang of this stuff. It was thicker than your typical caulk, and I wasn't really laying a bead. I was filling a little canyon, and somehow I needed to make this stuff flatten-out on top. I started out by spreading the bead of caulk. Not satisfied, I decided after the third row that I would simply over-fill the joint. I figured it would make for a clearer joint if I allowed the over-filled joint to dry lumpy and then be planed smooth with a razor.
At this point I took a break and made a trip to the local West Marine with three more tubes of Life-Caulk. Did I pay full-price? Not on your life. I price-match everything - everything, that is, except for the plastic cups used for the mixing of epoxy. This is about the only thing at West Marine that is not over-priced. Do I mind spending my money at West Marine? Not at all. I know quite a few people who work there. They are good people, and my purchases support their jobs.

At any rate, back to the subject at hand . . . after saving about $7 per tube of Life-Caulk by price-matching, I returned to the hatch, ready to complete the job.

This concludes the third of a four-part series on the construction of a new companionway hatch for the Ericson 25. In the four and final posting, we'll address the application of finish coats to the hatch.

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