Surface-mounted portsOld leaking portlights? Here's one solution
by Steve Stoehr
Just about every sailboat over 20 years old has the same basic construction for its fixed portlights. Clear
plastic or glass in the window opening was kept in place between frames (usually metal) on the inside and outside of the cabin trunk, all held together with bolts or screws. Liberal applications of caulk were required to seal the whole assembly.
Over time, the seal failed due to aging caulk, different rates of expansion of the components, and hull flexing. Then, invariably, the port began to leak. The whole assembly needed to be disassembled, cleaned, and reassembled with new caulk if the leak was to be stopped. That worked for a while . . . until the whole cycle started over and the settee cushions got soaked once again.
In the 1980s, sailboat manufacturers started using surface-mounted fixed portlights. Clear plastic was fastened directly to the outside of the cabin wall using screws or adhesive caulk and no frames. Flexible caulk or a rubber gasket provided the seal. The clear plastic was free to "float" on the cabin surface and better maintain the seal, despite expansion, contraction, and flexing.
Recent boats have recessed lips molded into the cabin trunk around the window opening so the surface-mounted clear plastic fits flush to the cabin trunk. My previous boat, a 1986 O'Day, had surface-mounted fixed portlights. During 18 years of hard sailing, they never leaked.
Last year I bought a 1976 Tartan 30 to restore. It had the framed fixed portlights. All of these ports leaked and had been leaking long enough to stain the interior teak. I needed a more permanent solution. But, I wondered, are surface-mounted ports "proper" for a quality sailboat? Then I saw a beautiful Hinckley with surface-mounted portlights and made the decision to go ahead.
The first step was to design the size and the shape of the new portlights. Surface mounting allows some flexibility. They needed to be large enough to have the strength of storm shutters and plenty of overlap for a reliable seal. I decided on smoked plastic with a stylish rake in the forward portlight to soften the boxy lines of the Tartan. I made several prototypes out of black construction paper and taped them to the cabin to see how each candidate would look. After I decided on the design I had a local plastics fabricator cut the four portlights out of 3⁄8-inch acrylic stock and polish the edges for a professional job. The protective paper was left on both sides to make marking the pieces easy.
Finally, I located the positions of and pre-drilled holes for the self-tapping flathead stainless-steel screws that would secure the portlights to the cabintop. They were pre-drilled in the clear plastic to the tap size of the screws. The tap size is usually a drill bit one size smaller than the screw's outside diameter (OD). The portlights were ready for the next step.
I marked positioning guides next. Then I penciled in the exact vertical and horizontal centers of each portlight and its corresponding opening. Lining up the vertical and horizontal lines positioned each piece perfectly.
To prevent stress cracks from forming in the clear plastic over time, it's important to allow expansion and contraction tolerance around the mounting screws and to accurately center each of the pre-drilled mounting holes in the cabin trunk. I waited for a warm, but not hot, summer day to take off the old portlights and mount the new ones. I precisely located each new portlight on the cabintop, using the horizontal and vertical positioning guides and manually holding each in place. Using the two holes marked with arrows as drill guides, I drilled two holes into the cabin at each end of the new portlight, using the tap-size drill bit.
Once the piece was removed, I redrilled each of the two holes marked with an arrow to the exact OD of the mounting screws and temporarily mounted the new portlight using two screws in those marked holes. With the piece securely fastened in place, all the rest of the holes for that portlight could be accurately drilled into the cabin using the piece as a drill guide and using the tap-size drill bit. Finally, I removed each portlight and redrilled each hole in the piece to a size slightly larger than the OD of the screw, allowing for expansion and contraction. I remembered to mark the cabin location of each piece. The new portlights were now ready to be permanently mounted.
I purchased neoprene closed-cell foam-rubber gasket material from a local rubber distributor. A 4-foot square sheet of 1⁄8-inch-thick material was more than enough for the project and cost less than $20. The rubber material sealed all of the spaces between the smooth clear plastic and the irregular fiberglass while allowing the portlight to "float" on the surface without breaking the seal.
I cut out four rubber pieces slightly larger than the portlights and taped these over the window openings. After I removed the protective paper, I placed each portlight over the rubber gasket material and screwed it down, using the predrilled tap-sized holes in the cabintop. A dab of caulk was used with each screw and washer to seal the screw in the portlight and keep it from backing out while allowing for some expansion and contraction around the screws. Lastly, I used a sharp box cutter with break-off tips to cut away the excess rubber gasket material inside and outside. Soapy water makes the rubber easy to cut cleanly.
Steve's Tartan has a new look with her surface-mounted portlights
Since the new portlights were now outside the window opening, I needed to cover the raw edge of the window opening inside the cabin. I reused the original aluminum inner frames after bringing them back to like-new condition using mag wheel cleaner purchased at a local auto supply store. The gap between the inner frame and the inside of the portlight's clear plastic was filled using self-adhesive weather stripping. This hid the raw edge of the window opening nicely.
The acid test
Using a high-pressure hose, I leak-tested the new surface-mounted portlights on a very hot summer day and again on a cold autumn day after a hard sail. There were no leaks whatsoever. Plus, the boat now has a pleasing, more contemporary look. I'm satisfied.
Steve Stoehr built his first sailboat in 1961 from Mechanics Illustrated plans, taught himself to sail, and has been sailing, repairing, and upgrading sailboats ever since. He's restoring a freshwater Tartan 30 in Ohio with plans to sail it to Massachusetts via the New York Barge Canal.