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.
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.
If Steve's plastic hasn't crazed ten years from now...we'll know the maufacturers were all wrong.
IF your leaks are due to flexing, it will be difficult to get *any* lens or frame to seal for very long. Flexing is rather common to some cheaply-engineered / -constructed boats, which is why they cost a lot less in the first place. But you knew that, right?
External lens caution: be sure that the material has the strength for the width/length on your particular boat. Note that you trade off strength between acrylic (less bend, more chance of a crack or break) and polycarbonate (more bend, little chance of a break). Also, without expensive surface coatings, the stronger polycarb. will degrade a lot quicker in the sun light.
Gasket material: the author is happy with rubber. I would advise using sealant.
The part of the narrative about "floating" the new lens on the outside surface is VERY important. I would go for at least an eigth of an inch of black sealant. Use a special commercial goop or get some Boatlife "LifeSeal" from your chandlery. This is just about the only commonly-available sealant/adhesive for this application.
Dealing with the mess... leave the protective paper on the new lens, both sides, except where the inside mates to the cabin side. Next, sand the surface of the plastic lens where the sealant must adhere, about a half inch around the inside surface.
After you dry fit, tape off the outside of the boat around the lens edge with 3M FineLine or Blue -- same for the inside of the cabinside edge. Run some wider paper masking at least 4 inches beyond the tape...
In order to get the lens to float at the right heigth and not squeeze out the sealant layer, put small O-rings around each screw hole. Once you have the screws in, do Not overtighten them -- if you are indenting the lens around the screw, back off.
Note that the author told you to over-drill each hole. This is because of the expansion coeficient of the lens in heat and cold.
We did this work 12 years ago, using Lexan polycarb. and it is still leak free - although we do now have to polish out the surface once a year to clear up the UV degradation.
Oh, and keep a plastic-lined bucket near at hand while doing clean up with paper towels. You *will* need it.
Style and appropriateness for your particular boat design was not mentioned... some boats look fine with this modification. Others look, well, um, not so good. Consider carefully, before you choose to go frameless. Remember the fellow in the Indy Jones movie that chose the wrong goblet... "He chose... poorly," said the ancient knight...
Last edited by olson34; 06-20-2007 at 04:21 PM.
In my former life I worked on aircraft. A miserable job handed to the lower seniority techs (me, at the time) was repairing/replacing the cabin windows during the phase inspections. Needless to say Boeings and the other airliners have a lot of windows...
The windows are thicker than what is required in the marine industry (Learjet windshields are three layers over an inch thick) due to cabin pressurization, possible bird strikes, and the extreme temperature and pressure operating environments, but straight sealant is used and when properly done seals cabin air pressure from leakage at over 10 psi cabin pressure.
Depending on the installation, some windows requiring drilling while others have a mitre external surface that positions the window on the inner skin surface. Bits specifically manufactured to drill plastics are used to drill the retaining screw holes through the window due to chipping and possible stress cracks that may not be immediately visible wood/metal bits may cause.
Once the window is trimmed to size and retaining screw holes drilled - oversize holes as mentioned, a coating of the sealant is rolled on both inner and outer window surfaces, the aircraft skin, and window retainer mating flange).
The screws are coated with a good helping of the sealant and inserted into the screw holes while a helper installs the washers and nuts. Once all are inserted, they are first tightened until snug (using a cross-torque patter - evenenly on opposite positions similar to tightening your wheel lug nuts) then the final torque sequence is applied to the nuts/screws in the same pattern. While tightening the fastners, the excess sealant oozes out of the surface sealing areas and screw holes making a water and airtight seal.
The sealant is cleaned from the surfaces with MEK prior to setting up but, extreme caution must be used since MEK will easily damage plastic, fiberglass, melt you sneakers, etc.... and could damage the window or paint and fiberglass surfaces of your boat. Leaving the protective film on the lens surface and taping them and the adjoining cabin surfaces with several layers of good masking tape will help insure damage will not occur.
Although I have not used this sealant yet on my boat, I have purchsed several tubes to seal the LARGE side windows on my Conyplex during my refit project. I chose to use this type sealant since it is verry strong. It is also used on the wing stringers and rib to wing inner surface skin surfaces to form the integral wing fuel tanks. It is so strong, having a failed rivet or other fastener where it is used, the surfaces will still be in shear and held together. The sealant is a two-part mix, called Pro Seal with a P/N of 890 BX. The number in the X position = cure time in hours (1/2, 2, 4, etc.) available in several tube sizes and can be purchased from a aircraft parts/material supply stores.
After reading the Solar Stick thread I must say, I am not in any way aligned with the sealant manufacture. I'm just an everyday sailing nug applying differnt processes leasned along the way.
We use polycarbonate in our operation as machinery guards for many Fortune 500 companies.
Karen Larson, founding editor of Good Old Boat
Good Old Boat Subscriber Newsletter, April 2006
Surface-mounted ports, Part I
In the March 2006 issue, Steve Stoehr wrote about replacing leaky portlights with surface-mounted acrylic. I have an older Catalina 25 and deal with the same issues with water leaks. Unless I misread the article, Steveís instructions were to predrill holes in the cabintop for the self-tapping screws, yet I see in the photo the existing holes that held the original frame. My questions are: did he use these holes, did he fill in the holes, or could you use the existing holes for mechanical screws to anchor the acrylic to the cabintop?
Like so many of your readers, Iíve given up on the slick sailing
magazines. Keep up the good work.
Surface-mounted ports, Part II
Iím not sure he filled the old holes with anything because they would be hidden by the rubber gasket. I am sure he did not reuse the holes. There are ways to reuse the holes, but it is a matter of piloting, by which I mean that one would have to transfer the location
of the old holes to the new windows. It is actually easier to mount the new windows and transfer the hole locations to the boat by drilling through with the tap-sized drill and then later drill out the window to the clearance-size hole.
Jerry Powlas, technical editor
Surface-mounted ports, Part III
Jerry is exactly right. I covered the original holes in the cabin wall with the gasket and drilled new holes for the self-tapping screws. By drilling new holes I could follow the shape of the new port for a neater appearance, and better center the screws out over the sealing area. You could use bolts through the acrylic, the old holes, and the inside frame. However, as Jerry pointed out, that would be difficult to pilot and would be more expensive. Barrel bolts or bolts with cap nuts cost much more than stainless self-tapping screws, are more difficult to seal, and each bolt would need to be cut to length.
Surface-mounted ports, Part IV
Thanks, Steve; I think Iíll go with your approach. I canít get too excited about the idea of rebeddng (once again) old portlights. Plus, I think Iíll like the updated look.
Surface-mounted ports, Part V
Yes, there really is a lot of interest in this subject. Last week I received a call from a fellow sailor in Sacramento, Calif., who read the article. He went to the trouble of finding me using
the Internet (Tartan website and Google) to get his question answered about the gasket material. Leaking ports in his Freedom 32 ruined his favorite book, so he plans to try surface-mounted ports.
Thanks for sending the comments from Jim Donovan of Braintree, Mass. (Mail Buoy, May 2005 of Good Old Boat ). I looked up a Seidelmann 30 (29.9) and can see why Jim may
have experienced some chipping and cracking around the fasteners in his attempt at surface-mounted ports. That boat has a very low curved coachroof so the portlights are at about
a 45-degree angle from horizontal. That makes them very vulnerable to lateral stress when stepped upon or otherwise knocked about.
If I were designing surface-mounted ports for the Seidelmann 30, I would increase the acrylic thickness from 3/ 8-inch to1/2-inch, bevel the edge, and make sure there is at least a 2-inch overlap all around the port. I would not recommend using stronger polycarbonate because polycarbonate turns cloudy from sunshine.
Good Old Boat magazine, July 2006
Ports discussion continues
Having read the surface-mounted ports article in the March 2006 issue, Iíve been trying to find some of the rubber adhesive sheets you used between the fiberglass and the acrylic windows. If you had an exact name for a lead on the stuff, it would be greatly appreciated.
Author Steve Stoehr replies
The rubber gasketing material I used was plain 1⁄8-inch closed-cell foam neoprene rubber sheet stock. It was not adhesive sheet stock. Go to your nearest industrial rubber distributor (there is at least one in every city) and tell the man at the counter what you need. If you must substitute another material, choose one that is UV- and chemical-resistant. Closed-cell means that water can not migrate through it like it can through a sponge.
Ports: what color acrylic?
I read the article about surface-mounted ports by Steve Stoehr and Iím wondering what material was used to make the ports? The article says 3⁄8-inch acrylic stock. Can you be more specific about the color and the series or any specific information? I am trying to do the same with my Catalina and have already wasted $200 on plastic that is the wrong color. I would really like to get it right this time. I have to order the material from 60 miles away and I just canít drive there twice, once to look at samples and then again to pick the material up. I canít believe that it is this difficult to figure out what material to use. Any help you can give me would be greatly appreciated.
Back to Steve again
Just about any town of any size has at least one plastics distributor. Check the Yellow Pages under ďplastics.Ē They usually have clear acrylic sheet (Plexiglas) in stock but may need to order tinted acrylic for you. If so, they should have samples to look at to determine what tint you want.
I bought Acrylite GP acrylic made by Cyro Industries. My choices were clear, smoked, and reflective coated. The smoked tint is optically clear for good visibility yet helps filter out bright sunshine and offers some privacy below. The shiny reflective coated version is even better for blocking sunshine, but it looks tacky to me.
Check also for plastic fabricators in your area. They buy from the distributors and make custom things out of plastic, such as display shelves and cases. With any luck, you may find one with enough material left over from a job to make your portlights.
Here are a few more tips. Do not use polycarbonate (Lexan) for your portlights. While Lexan may stop a bullet, it scratches easily and turns hazy in sunshine over time. If you plan to use silicone to seal the portlights, use a silicone that does not smell like vinegar (acetic acid) when it cures. That kind will craze the acrylic over time.
Good Old Boat Subscriber Newsletter, October 2006
Surface-mounted ports, continued
I know that Steve Stoehrís port replacement article has almost created too much interest, but I just replaced the ports on my 30-year-old Irwin with incredible results. I completed the entire project in one weekend, for less than $100, and without the slightest leak.
One deviation that seems to have worked was to cut short (3/ 8-inch) pieces of gas line hose to use as spacers around the screws. This allowed me to greatly enlarge the holes in the Plexiglas and provide lots of cushion for expansion/contraction. Thanks, Steve!
Iím interested in further information on the gasket material mentioned by Steve Stoehr in his article, ďSurface-mounted ports,Ē in the March 2006 issue. I am unable to find similar material in my town, Muskegon, Michigan. Perhaps Steve might share the name of his supplier.
And Steve responds
The industrial rubber distributor I bought my gasket material from is Fournier Rubber and Supply Co., 1341 Norton Avenue, Columbus, OH 43212; 614-294-6453; fax: 614-294-0644;
This summer I installed four opening stainless-steel ports, again using some 1/8-inch rubber sheet stock as gasketing material. This time I bought EPDM sheet stock from Fournier because it is very UV- and weather-resistant. EPDM rubber is used for pool lining and for seamless roofing and can be very pricey ($4.25 a pound). EPDM stock is not foamed like the neoprene stock so it is harder than the neoprene stock. It would seal two smooth surfaces but may not seal irregular surfaces.
But it should last forever. If I had it to do over I might use EPDM for the surface-mounted portlights. So far the neoprene material is holding up well, and there are no leaks.
"Gas Blown" from Rubatex and some other makers, and the more common "chemically foamed" neoprene. The Gas Blown type is made by injecting high pressure nitrogen into the rubber "batter" and then allowing it to expand and cool, producing one inert sheet of neoprene foam.
The "chemically foamed" type is made by mixing in chemicals and the "cooking" the batter to expand and set it, like a giant pancake baking. The problem is, chemically foamed neoprene does SHRINK over the years, and sometimes degrades due to chemical actions or bad chemical choices.
But, most foamed neoprene on the market is chemically foamed since it can cost 1/2 as much to make it that way.
If you are using neoprene foam and want it "forever", buy the nitrogen foamed stuff. There will be a tag or other identifier on the roll. With a good eye, you can also see a difference in the texture of the rubber on bare cut edges.
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