Caulk It!

Caulk It!

Technical Editor, Joe Rocchio

I had just finished a quiet and relaxing shower aboard Onward, C470-126. My daughter and two grandchildren had flown home to LA after a wonderful week together during the Corinthians 2017 Ocean State Cruise. In the dim daylight, something caught my eye at the base of the shower forward bulkhead in the corner with the seat. I reached down to touch the shadow and my heart fell as I realized it was a ripple in the laminate surface of the bulkhead. I left the shower and stern head doors open while Peggy and I headed off to Long Island by car for a few days – the plan being to let the area dry out so I could fix the de-lamination by cleverly injecting an adhesive of some type behind the problematic laminate layer. When I arrived back aboard, I was startled to find the de-lamination area was almost 18" high and 20" wide – a major problem. There was no alternative but to probe the area and this indicated the affected area of the 3/4" plywood bulkhead had lost structural integrity. Major surgery was in order.  In the C470 stern shower, the forward bulkhead is constructed from a panel of 3/4" teak plywood. The shower side is covered in a plastic laminate and the salon side is a ply of decorative teak. The former provides a waterproof surface in the shower and the latter forms part of the varnished teak finish of the salon. The salon-facing bottom section of this panel is concealed behind the seat of the nav station. To fix the problem, it would first be necessary to cut out the section that had become structurally damaged in what had apparently been long-term exposure to shower water. Next, a waterproofed plywood panel would need to be fitted to replace the damaged section and then fastened in place. Finally, a layer of plastic laminate (e.g. Formica) would be fitted in place, glued, and then caulked to again provide a waterproof surface. For some time, I had wondered if I should add a “multi-tool” head to my suite of Ryobi One+ 18V Li-ion battery powered tools. Well now I did the research and found that this tool was the only way I was going to be able to do the necessary surgery with plunge cuts to remove the damaged bulkhead section. To start, I used the multi-tool scraper attachment to remove the failed caulking along the edges of the base and side adjacent to the shower seat. Then, I used a 1.5" wide plunge-cutter blade to remove small sections of the bulkhead, increasing the perimeter until the remaining panel was undamaged by water penetration. See Photo 1 for example of damage. Next, I cut out as little as possible additional material to make a section that was more regular in shape to facilitate installing the insert. See Photo 2. I purchased a piece of 3/4" 7-ply birch plywood and a similar size piece of plastic laminate that matched the original color almost exactly. I made a cardboard template of the cutout area before I cut the plywood to near net shape. Then, I used a plane and file to taper the edges back slightly for a firm but easy fit. Next, the plywood insert was waterproofed with two heavy coats of polyurethane varnish. The cut edges were thoroughly soaked with the varnish to prevent any future water infiltration; the same was done to the cut edges of the bulkhead. Once the varnish was thoroughly dry, I used 3M 5200 adhesive caulk to coat the edges of the bulkhead and the insert well. I masked both sides of the seams to allow liberal application of the 5200. Then, the insert was put in place and three SS 8 x 1.25" screws used to fasten it to the fiberglass that forms the aft face of the navstation seat. See photo 3. The 5200 adhesive caulk was allowed to set before I made a paper template of the rectangular section that would be covered with the new laminate that was then cut and carefully shaped to fit snugly. After carefully masking off the surrounding bulkhead area, spray contact cement was applied to the bulkhead and to the back of the laminate. When the contact cement was “tacky dry,” I covered all but a ~1" strip along the shower seat side with heavy brown paper and aligned the laminate carefully in place before removing the paper. I used a wallpaper seam-roller to make sure there was good contact all over. After the laminate had set overnight, I masked off both sides of the perimeter leaving a ~1/4" unmasked area on each side of the seam. A robust caulk seam of 5200 was formed all around the laminate insert. Next, a silicone rubber tool was used to make the surface of the seam continuous, even and smooth. The caulk was left to set and when safe to touch, the masking tape was removed to leave a fine looking caulk seam. Wow, that first shower was WONDERFUL (and badly needed). See Photo 4. Note that all of the salon face of the insert was hidden by the nav station seat except for a 1.5" x 6" section at the lower inboard corner below the seat cushion. Here I covered the entire 4" x 14" bulkhead area with a thin sheet of 1/16" thick teak veneer and varnished it. Why did this happen? Well, part of the problem was frequency of use as I have used the aft shower almost daily over the last 14 years! However, it points out that even the amazing 3M 5200 has a finite life and will develop micro cracks and pores that can allow water to penetrate. But, while necessary, these factors are not sufficient. The real issue was an oversight during construction by Catalina whose overall work is exemplary. In this case, they failed to seal the edges of the plywood panels used as bulkheads. Over the years, water had penetrated the caulking and the raw edges of the plywood soaked up water until de-lamination occurred. The affected area was backed by the fiberglass of the nav station seat and thus, could not get enough air circulation to dry.  Recommendations: If you use any type of plywood or wood on a boat, take the time to seal the edges to be hidden using polyurethane varnish or old fashion but effective shellac. A multi-tool is a wonderful thing to have aboard. And, see that seam before it fails: Caulk It Now!!! Note: The sensors and editors have caused me to remove several pages of oaths and expletives that were uttered while painfully trying to make my body fit the space available to do the repair! Ouch! It hurts just to write about it. –Joe Rocchio,


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