Hot tip
In the infamous 13 page letter S2 owners are familiar with Tiara. I think you absolutely must mask off the windows non-sealing surfaces then abrade the bonding surface or forget it. I looked at an S2 with brand new windows...that had popped right off and were merely lying in place. Here is the excerpt...note that they repeatedley refer interchangeably to plexi as lexan and they are two different materials. The theory should be the same. A link to the whole letter is attached. I hope this is helpful. BobM "Here is how we installed the window's originally. We took a plexi window with the outer surface covered entirely in masking tape, and set it temporarily in its opening. Next we shimmed it (only if necessary) to ensure it would be flush with the surrounding fiberglass. We masked off the surrounding border of the opening and drew "cross hairs" on the masking tape (both on the window and the surrounding mask) to aid in alignment while installing the window with sealant. The perimeter of the window's surface (that comes in contact with the opening) was then roughed up with 80 grit sandpaper. Take care not to scratch any portion of the window that you will be looking through. With the window removed, both the opening perimeter and the edges of the window received a generous bead of black silicone caulk. Here comes the Chinese fire drill; the window was literally mushed in place from the outside, while someone inside the boat armed with a putty knife and lot of rags, caught the oozing caulk and wiped it on rags." "From the outside, once the window was in flush with its surroundings and aligned with the cross hairs, a plastic scraper was used to scrape all the outer ooze off flush with the window and cabin house. The caulk was then allowed to cure for twenty-four hours. The thicker the bead of silicone, the longer it needs to cure, and it will take a while before the entire seal is cured all the way through. The masking tape wasn't pulled off until after the twenty-four hours elapsed. If you just need to make your seal look pretty again, dig out the outer layer of sealant. Mask off, overfill with silicone and level with a plastic scraper. Now, the people that did this on regular basis did not really need to touch up the caulk much to make it look pretty. Nevertheless, if it does need to be touched up, here is what you do. You will need a small container of water, more rags, and more black silicone. Apply the silicone where you need it and then dip your finger in the water, smooth the caulk, wipe your finger on a rag. Re-wet your finger, smooth seam, wipe finger on rag, repeat as necessary. You may elect to do this step while the masking is all still in place." Things to Remember: #1. If you skimp on the caulk, you will end up with either air bubbles, voids in the seal or both. #2. Silicone does not stick unless all the surfaces are clean and dry. #3. Don't let someone talk you into using something other than silicone. The thermal expansion and contraction rates are drastically different between the Plexiglas and the fiberglass. So elasticity of the cured sealant is critical. #5. Your elastomeric poly-sulfides are better adhesives (remember cleanliness when using silicone). But, they cure hard and cannot expand and contract with the changes in temperature. #5. Keep solvents away from Plexiglas, Lexan, and acrylics. They will craze Plexiglas and speed its degradation. Even Windex has NO PLACE on or near these polycarbonate materials. For general cleaning, furniture polish like Pledge is your best bet. For more serious cleaning use denatured alcohol.
