Bedding Acrylic Ports

[ocarina]

The old acrylic panes are lying on the bench and I'm trying to figure out how to proceed. Last time I replaced these portlights I cut them too large, used the wrong sealent and over tightened the fasteners. They started cracking the first time the vessel was picked up with the travel lift. I'm hoping someone can give me some tips.

[SkiprJohn]

Aloha and welcome aboard!
I know there is someone out there with the experience you need to tap but I'm not the guy. Hope they show up to help.
kind regards,

[Blue Stocking]

Loads of discussion on this recently on CF. From some very knowledgable people.

[Cormorant]

I bedded mine with butyl rubber. It's soft, pliable, and never hardens. Has kept my ports sealed well for six years now.

[jerrymc]

Originally Posted by Cormorant

I bedded mine with butyl rubber. It's soft, pliable, and never hardens. Has kept my ports sealed well for six years now.

Cormorant: more info, please! Did you cut gaskets? How did you "fix" them to the coachroof (sides)? Or are you talking about an adhesive?

Sorry to be so dense, but I'm facing this project myself on 6 ports & trying to put together a plan.

thanks,

[Dick Pluta]

I just finished doing all 12 on my Islander Freeport 41. I first tried butyl sealant based on good experience in my automotive supplier phase, but found that they had to be mechanically fastened. It worked perfectly, until the temperature got to 80 degrees, when they simply slid down the sides of the cabin.

Then, based on recommendations from the acrylic supplier, I used automotive windshield sealant. They told me to clean the acrylic with alcohol, no primer required. I did a test strip and it peeled easily, so I only did one window. It went in ok, but, because the window had a slight bend, the next morning it had also popped off. Finally, I did what a lot of people on this site recommended. I got some Sikaflex urethane adhesive and their pretty expensive primer. You can get the numbers off their web site. The adhesive is the one with the UV suffix. You can buy it from Merritt Marine near West Palm in FLorida. 800 375 2628. Ask for Tim. Use Sikaflex. ACCEPT NO SUBSTITUTES! Primer is MANDATORY!!! 3M windshield adhesive WILL NOT WORK!!!

Here is the detailed procedure. After getting the windows cut to shape from Cyro smoked acrylic, I masked off a 1 inch strip around the perimeter and primed it. The primer is black and provides a good black out strip that does two things. It provides a visual barries that hides the not so pretty adhesive and also provides UV protection for the adhesive. The primer dries VERY FAST. I used disposable bristle brushs. A dauber would have been better. If you're using smokes acrylic the prime job doesn't have to be perfect. The color hides it.

After priming the acrylic, do the same to the deckhouse. Mark the window outline on the dechhouse, mask and prime a strip that matches the window profile. You will have to provide for temporary fastening while the adhesive sets. I drilled six holes, four in the corners and two in the center, top and bottom to hold it in place and put the slight bend into the acrylic.

Next get some spacers. I used the vinly ones you can buy at any hardware store for spacing ceramic tile and cut them into strips. You want to space the acrylic away from the deckhouse to allow for expansion differential between the window and the fiberglass. Apply a thick bead (1/2 high by whatever wide) to the window by cutting a v shaped notch in the side of the applicator tip. Put the spacers inside the bead so they will rest against the deckhouse and space the window out about 1/4 inch.

Press the window in place, squeezing the adhesive out to ensure a good seal. Screw it in place using temporay screws and allow to set overnight. Remove the screws and trim the excess sealant. Check for leaks and backfill wherever necessary.

Good luck. Big, nasty job. Any questions, just ask.

Dick Pluta
AEGEA

[AnchorageGuy]

ocarina, We have been replacing and re-bedding acrylic ports for many years and the one product that has performed the best and never leaked for us is Dow 795. The black is reported as UV resistant but the white is not.

[Cormorant]

The butyl rubber I used is pretty low-tech stuff. It's the "butyl rubber tape" you can find from RV stores or on EBay. It has the consistency of well-chewed bubble gum. You can find it in white, gray, or black.

I have a series of oval portlights along the boat's topsides. Our boat is wooden, so we just cut the lexan to size (1" overlap all around), predrilled holes along its edge, laid a strip of the 1" tape around the opening on the boat, and screwed the lexan down with a dozen pan-head screws around the edge, leaving maybe 1/8" of space between the lexan and the boat so the butyl didn't get all squeezed out. Trimmed off any that did squeeze out.

I realize this might not be an easy method on thinner fiberglass hulls.

[steve_hendry]

I've used Life-Seal (Boatlife Life Seal
with good results. It's a polyurethane/silicone combo.