Resolving Hatch and Portlight Problems - SailNet Community
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Resolving Hatch and Portlight Problems

The essential hatch: it offers light and ventilation to the interior, but requires diligent maintenance.
Hatches and portlights are double-edged swords. Like Damocles' blade, they hang over your head offering light and fresh air, but threatening to shower you with sprinkles at any minute. Few sailors would live below in a boat without at least a few ports and hatches, but the more you have, the more time you need to spend inspecting and maintaining them.

There is such a variety of ports and hatches on the market that only a few generalizations can be made about their common problems. Let's take a look at the specifics first, beginning with materials:

Wood    Hatches and skylights made of wood are common on many boats. Properly varnished they look very shippy and offer the designer the opportunity to build any shape or size desired. The major problem with wooden hatches is that the wood swells and contracts with variations in temperature and humidity at a different rate than the deck. This movement eventually cracks even the finest wooden cabinetry, breaking the caulking seal to the deck or any imbedded glass, and eventually loosening the paint or varnish which will allow rot-producing moisture into the wood. Inspect wooden hatches often for signs of moisture penetration and repair them immediately.

Portlights, like this one over the galley, need secure gaskets and functioning dogs to ensure that they keep the weather out when not open.
Fiberglass    Hatches made of fiberglass have the same design flexibility as wooden ones but without the fear of deterioration. While some are robust replicas of their wooden cousins, many builders of fiberglass boats unfortunately make flimsy hatch covers to save a few bucks. Some of these twist out of shape easily and will show cracks in the corners or at stressed fittings. Failure to design a proper seating area for a gasket between the hatch cover and deck flange is another common problem. If a poorly designed or built fiberglass hatch conforms to a reasonably common shape, it can easily be replaced with a stock metal or plastic hatch.

Aluminum    Probably the most common material used for hatches today is aluminum, and there is a wide range of quality. Cast aluminum hatches and ports offer greater strength and design flexibility, but they are far more expensive than aluminum formed of extruded shapes. The most common problem with extruded hatches and ports is that their frames are often warped in the installation process, making a seal between the glass and the frame impossible. Aluminum and salt water are mortal enemies and the anodized or painted surface coating will eventually need to be renewed.

Bronze   The old standby in hatch and portlight materials is bronze, especially for portlights. It is strong, inexpensive to cast, and is not degraded by corrosion (if you don't mind a little green on board). Bronze can also be chrome plated if a yacht-like appearance is desired, but such plating eventually wears away.

Stainless Steel     At the high end of the scale are hatches and portlights cast in stainless steel. Offering the ultimate in strength, corrosion-resistance, and long-term good looks, these are very expensive, and carry a bit of snob appeal.

"The main advantage to plastic ports and hatches is the low initial price and wide availability of replacement parts."

Plastic   Of course plastic is very commonly used for portlights and some hatches on inshore boats. There are actually several different materials from the ubiquitous PVC to the much stronger filled Nylon. The main advantage to plastic ports and hatches is the low initial price and wide availability of replacement parts. This availability is a good thing since plastic ports and hatches are easily warped in installation, break easily when mishandled, and have little long-term UV stability. However, they fill a need for daysailers and inshore cruisers where expense is a major consideration.

Regardless of the material used to construct a port or hatch frame, all of them share common failures that need to be addressed before the raindrops will stop falling on your head—or your berth and books for that matter. Here is a list with some general thoughts on repairs:

Glass used in hatches and ports often breaks, crazes, or cracks. In fact, very little of it is glass anymore—if it was real tempered automotive safety glass, it wouldn't craze, would it? The only solution to these problems is to replace the plastic sheet. This is easiest on plastic portlights, since the whole glass is usually a molded piece including the hinges and dog ears. With some metal ports and hatches where holes have been drilled at specific points in the glass to accept dogs or hinges, the best way to get a replacement glass is to buy one from the manufacturer. For many others, including most wooden and fiberglass hatches, you can often replace the glass with sheet cut at your local hardware or plastics store.

The bronze portlights and aluminum hatches seen here are industry standards.
Here you will be offered two choices in a wide variety of tints and colors—acrylic and Lexan. Lexan is so strong it is used for bulletproof glass and it is surprisingly easy to work with metalworking tools. But it has four drawbacks: it is far more expensive, it scratches much more easily, it has very limited life in the sun, and it is more flexible, making the maintenance of a caulked seam more difficult. Acrylic has less ultimate strength and takes patience to avoid chipping in the cutting process, but I normally recommend it unless the application covers a very large window where the extra strength of Lexan is an over-riding concern.

Dogs, riser arms, and hinges eventually become inoperable, especially on inexpensive ports and hatches. If anyone can tell me why a dog with a threaded brass insert riding on stainless threads to a dog pin made of spring steel inserted into an aluminum hatch or port frame is expected to survive in the marine environment, I'll fix their hatches myself. Dog knobs do wear and are sometimes stripped, riser arms accidentally get bent, and hinges work loose. Sometimes you can find replacement knobs, wing nuts with the right threads, or spring pins at the local hardware store in an emergency.

Hatches and portlights generally seal with gaskets, which eventually wear out. Other than a few old double-framed wooden hatches, every opening port and hatch relies on a rubber (or synthetic) gasket to seal the gap between the frame and the opening portion. These materials have a life of about five years and yet I have seen some over 20 years old still dripping merrily away. Portlight and hatch gaskets should feel soft to the touch—if the material is hardened or cracked, it needs replacement to seal properly. Some manufacturers use proprietary preformed shapes that only fit their ports, but otherwise gasket material is easy to find in long lengths or full rolls. It is simple to cut and glue into place even on metals using a rubber cement such as Pliobond. Be sure to cut the two ends on a miter, place the seam at the top of a portlight or aft on a hatch, and glue the ends together to avoid creating a new leak.

Proper bronze portlights with stout hinges and secure dogs brighten the interior for all the crew on board. 

The most common problem with hatches and portlights is leaking between the frame and the deck, cabinhouse, or hull. Sometimes these leaks are from shoddy installation and sometimes from flexing of the boat, but the result is the same. No, you cannot solve these leaks by smearing silicone all over the outside of the boat. The port or hatch frame must be removed, both the frame and the deck cleaned of old caulking, and the whole thing reassembled with new bedding compound. If your boat has stainless steel bolts or screws into an aluminum hatch or port frame, take your time and keep your voice down. Do not use a polyurethane compound such as 3M's 5200 when reinstalling because it makes an irretrievable bond and attacks some plastics. Most silicone caulks have very little bonding power and tend to shrink, making it difficult to get a good long-term seal. Polysulfides like 3M's 101 are more expensive but are best suited for this job. And LifeCaulk offers a new polysulfide/silicone blend called LifeSeal that is made specifically for plastic ports and hatches.

If you like to look on the positive side of boat maintenance, there's a bright spot to removing a hatch or port for re-bedding. While you have the frame out and are scraping the old caulking off the deck, inspect the core material in the deck if any is visible. Leaks around ports and hatches often precipitate rot forming in a plywood or balsa-cored deck. If you can see any coring material and it's in good shape, now is the time to seal it with epoxy. If you find rot, welcome to the wonderful world of unintended-yet-mushrooming-boat-work lists.

Leaks that occur between the frame and the glass on portlights of traditional metal construction are quite common. The glass is often held captive by two metal frame halves using a shaped rubber gasket or bedding compound in between. The bad news is that the halves rarely come apart easily. But there are two pieces of good news here. One is that these leaks are usually small, nuisance items. The other is that there is a product with the highly unlikely name of Captain Tolley's Creeping Crack Cure that is designed specifically to fix these leaks. It is a very low-viscosity polymer that flows into hairline cracks before curing. I've used it in places that I shouldn't have, and I've always been amazed at the stuff. Sojourner never leaves home without three bottles on board.

Dedicating an hour once a month looking for corrosion, cracks, and broken welds in hatches or portlights is time well spent. If you find a problem, or something breaks unexpectedly, don't procrastinate in making repairs since the sword will eventually fall on you. Even tiny drips can do thousands of dollars in damage to the interior woodwork, cushions, and delicate contents inside your boat.

Tom Wood is offline  
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