Part of the reason we chose Lagoon models later than 2005 was the windows. Cabins in the later models have a large picture window that keeps them from feeling cave-like. They brighten up the cabin and provide ocean views that one would pay big bucks for on a cruise ship. But they are not without their issues.
These windows are set into the hull walls. They are set into a pocket that is molded into the hull. They are then bonded and sealed with an acrylic friendly bonding/sealing compound. The problem was a large temperature fluctuation combined with a constant bashing against a dock in South Carolina. During our stay in the Chesapeake, we experienced temperatures in the single digits. Then as we moved south in the spring the temps were still chilly and began to warm up fairly rapidly. This temperature fluctuation was the first part of the problem.
Part two started after we had a rough bashing passage after leaving Southport, North Carolina. We ducked into Hilton Head, SC to catch a break from the horrible sea state. The winds that caused that sea state were still a problem at the dock. We had a significant portion of the Intracoastal Waterway as fetch. That fetch allowed chop to build which constantly bashed our starboard hull against the dock. Even with all of our fenders out we were getting beat up. As the winds began to die off we began assessing damage from our passage. We discovered among the things that were damaged, the picture window in our starboard forward cabin was hanging out, literally. It was only held on by the bead of sealant along the bottom of the window. Now what?
Having a large hole in the side of your boat is not really ideal. I also had no idea how to go about making this repair so that I wouldn’t have to re-repair later. I hate re-work, a lot. We soon discovered that our same issue was not as obscure as we thought. It was actually quite common. A few posts on Facebook and we found friends who had experienced the same type of window failure. Along with other friends who were worried about their own windows failing.
Thanks to those friends, and a significant amount of research and reading about bonding agents, primers, sealers, acrylic, perspex, polycarbonate, fiberglass, gel coat, and the chemistry of all of the above. That combined with a good technical paper from the company that makes Sikaflex. We had a plan. Here is the product of that learning. I believe our end result looks better than what came from the factory and also seems to be stronger. I’m much more comfortable with that window than any of our others.
The plan called for a number of components, only a few that I did not have on hand. I’ll dive right into those. You will need the following items:
Sika Aktivator 205 – 250ml bottle
Sika Primer 209D – 250 ml bottle
Sikaflex 295 UV – White – 10.3oz Tube
Sikaflex 295 UV – Black – 10.3oz Tube X2
3M Auto Care Performance Masking Tape (It works better than the blue but I didn’t have any so I used blue with no issues, YMMV)
Denatured Alcohol
Hot Glue Gun
Hot Glue sticks
Wooden blocks, wooden stringers, wooden wedges, wooden spacers
Screws (See below, this is important)
Sanding block/sandpaper/Dremel w/flapper wheel/whatever works for you
Scraper
Rags
Adhesive vinyl or paint appropriate for acrylic. (This is to protect the bonded surfaces from the sun.)
Download Sika’s Guide to Bonding & Sealing Plastic Marine Windows with Sikaflex 295UV
While we waited for the various bits & bobs to arrive I used white duct tape to keep the window in place. This also helped to keep the rain out. While it worked just fine, I would recommend using something other than duct tape. Removing the residue made for a little extra unnecessary work. Make sure you use denatured alcohol instead of the usual cruiser go to, acetone. I repeat, DO NOT USE ACETONE for this project. Acetone will destroy acrylic and you don’t want to have to buy another one of these windows.
Attaching these windows to a Lagoon hull requires two components. The first component, the bonding phase, requires the additional Sika primer and cleaner (Aktivator) listed above. The second component, the sealing phase, is the final phase that gives you your end result. For the bonding phase, I used a little more than one 10.3oz tube of Sikaflex black. I probably could have gotten away with only one tube but I feel that having a little extra was the better path. Plus I had a little extra to repair a crack in our salon windows (also from the cold). For the sealing phase, I purchased two tubes of Sikaflex white but I really only needed one. I’m happy to have an extra as the Sika is so much easier to work with than the 3M 4200 or 4000 (I don’t use 5200 for anything).
If you are removing your existing windows to re-bed them, I won’t be of much help for that specific activity. Mine had already fallen out. But, I would recommend a generous use of denatured alcohol and a syringe to soften up your existing bonding. Then, working with someone on the inside and someone on the outside to make sure the window doesn’t fall, provide gentle constant pressure until it comes loose. Don’t force it, and don’t try to pry it out as you can easily damage the window itself or the molded gel coat pocket.
After the window is out either by removing it or if it removed itself, you will need to remove as much of the existing bonding and sealing compounds as possible. Preferably, every bit of it. If you are lucky the prior bonding compound will have left all of itself on the gel coat pocket instead of the window. Removing it from the window will take a lot more patience and time so you do not damage the acrylic. Removing the bonding from the gel coat in the molded pocket is not trivial either. But you can get away with using more aggressive mechanical methods, such as a Dremel with a sanding flap-wheel. Start reverse to conventional wisdom and use the finest grit you can that still removes the bonding compound while limiting damage to the gel-coat as much as possible. You can use the If you end up with any significant nicks or raw spots on the gel-coat you may need to touch those up before you can proceed with re-bonding your window.
Now is a good time to read Sika’s Guide to Bonding & Sealing Plastic Marine Windows with Sikaflex 295UV.
Once you have removed all of the old bonding and sealing compounds from both the hull and the window, clean everything thoroughly with denatured alcohol, including the gel coat outside of the window pocket for at least twelve inches or so. Now you can tape up the inside window frame to make for easier removal of any excess bonding that may squeeze out when the window is pressed into place. Wait to tape up the outside until later as you will have wooden blocks in the way.
Here is where the wooden pieces come into play. You will need to hot glue four or more wooden blocks to the outside of the hull. These are there to allow you to screw in the wooden stringers that will provide counter-pressure to the wooden wedges that will help hold the window in place while the bonding compound cures. Make sure that you clean the gel coat thoroughly with denatured alcohol under where the blocks will be glued. You will glue them evenly a couple of inches outside of the window pocket. Once the glue sets, give them a little tug to make sure they have adhered to the hull. You may have to repeat the process until you get a good “stick”.
Do a trial/dry fit now to make sure that your blocks, stringers, wedges, and spacers are all the correct size before you get started!
Now is a good time to re-read Sika’s Guide to Bonding & Sealing Plastic Marine Windows with Sikaflex 295UV
Follow that guide closely for the bonding portion. You will need to clean everything again with the denatured alcohol, then following the guide to use the Aktivator and then applying the Primer to the acrylic window. Note: You don’t apply the primer to the gel coat, just the window. You will be using the Sikaflex black for the bonding phase. You don’t have to follow my color guidelines but the white will be much more visible if you use it for bonding. The black will make for a less abrupt transition between your hull and the window if you use black for the sealing phase.
Once you have all of that done and the window set into place, screw in your wooden stringers to the blocks you hot glued to the hull. IMPORTANT!! Double & Triple check the length of your screws!!! You DO NOT want the screws to penetrate your hull or even touch your gel coat. I can not stress enough how important this is. These screws are only there to hold the stringers to the blocks, they are only temporary. Once you have your stringers in place, gently add your wedges to provide just enough pressure against the window to hold it in place and prevent it from moving while the bonding cures. You will likely need to add spacers at the bottom and sides of the window to keep it centered in the molded pocket. I also taped the wedges to help keep them in place should they try to work themselves out while the bonding was curing.
The guide states to let the bonding set for a few hours. We waiting at least 4 hours before moving on to the sealing phase. Before you move to the sealing phase you will want to remove your spacers, wedges, stringers, and blocks. Be very careful when removing the blocks so as not to allow any of the denatured alcohol to come into contact with the Sikaflex you just use for bonding. I used a number of blue rags to make sure that any extra alcohol didn’t go anywhere. If you use a syringe to slowly soak the block with denatured alcohol where it is joined to the hull, the hot glue should soften enough to allow you to remove the block and glue without issue. Do not force or pry as you could damage your gel-coat. Be patient and allow the alcohol time to do its job.
Once you have the blocks removed, give it all a quick clean with a rag and some denatured alcohol or any of the Aktivator you have left (should be plenty). Then tape around the edge of the window pocket where ever you do not want sealant. Also, tape the window itself up to the edge. Take your time as this will determine how the end result looks. Once you are completely done taping off, follow the guide again and fill in the gap with the Sikaflex White and smooth out with your finger or whatever tool you prefer to use for such things. Make sure to remove the tape once the sealant has set partially and not wait until it is fully cured. This will prevent any extra tape from getting caught underneath the sealant and thus preventing you from removing it completely. (Don’t ask me how I know this.)
After everything has had a couple of days to cure completely you will need to either apply a vinyl border around the window or apply some form of acrylic safe paint. This is to protect the bonded surfaces from exposure to the sun. Since we already had a black vinyl border a couple of inches thick around our window we didn’t have to worry about it.
If you are going back over the window with the stock perforated vinyl that Lagoon likes to use make sure that a couple of inches around the edge of the window is solid vinyl. The previous owner of our boat did us a solid and had all of the perforated vinyl removed and replaced with the black vinyl borders. They had a local auto window tint shop take care of that and add a good tint to the inside of the windows at the same time. It is a much cleaner look and now may be the perfect time to do something like that if you, like me, dislike the perforated vinyl look.
I wouldn’t consider myself a professional at replacing these windows but I hope this little how-to can help save you some time and effort and perhaps a little heartache if you are faced with having to replace your Lagoon hull windows. I’d also like to thank everyone that chimed in on how to best go about replacing these windows. Especially, s/v Bonanza who, like us are on a Lagoon 420 and, had to deal with these windows falling out!