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Replacing frameless acrylic fixed ports

Apr 5, 2009
1,620
Catalina '88 C30 tr/bs Oak Harbor, WA
I finally got around to replacing the lenses in the fixed portlights in my 88 C30. In the originals, the lens was held in place with screws around the perimeter but I used VHB tape and Dow 795. Here are some photos. The three vertical strips of white tape form a hinge to allow the lens to be properly aligned and then rotated up out of the way to strip the paper off the back and wipe down with alcohol before sticking to the tape.
I removed the old lenses with a kitchen pairing knife that was thin and flexible enough to fit into the small gap and cut the old silicone.
I then used the original lens as a template to cut new 1/4" "dark smoke" cast plexiglass to shape. After drawing the shape on the sheet of plexiglass, I cut the rough shape on my bandsaw and then stuck the new to the old with SailRite basting tape.
I used a flush cutting router bit to trim the rough blanks to the same size as the originals. After switching to a 45º bevel bit with bottom bearing I cut the 45º bevel into the back side.
The original lenses were tight fitting with almost no gap around the edges and very thin layer of silicone between them and the cabin. If the sealant is too thin, it can cause leaks from thermal stresses so i needed to make the new lens about 1/8" smaller on each edge. This also gave me a big enough gap to gun the silicone into. I did this by adjusting the depth of the 45º bevel deeper to cut the extra 1/8".
After cutting all of the old silicone off with a sharp chisel and cleaning it with sealant remover and sanding, we applied VHB tap to the edge of the opening and masking tape to the perimeter. (In hind sight, it would have been better to mask the cabin top after the new lens was stuck to the VHB.) Then we positioned the new lens in the opening and when happy with the location, added three tape "hinges" to the top to hold it in position.
The lens was flipped up on the "hinges", paper removed from back and cleaned with alcohol. Then the backing on the VBH was removed and the lens rotated back into place on its hinges. The alignment was perfect.
The project was then finished with black Dow 795.
So nice to have clear window for the first time in 20 years.
 

Attachments

Jul 26, 2009
258
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What a nice looking job! Looks very good and thanks for sharing - something I'd like to tackle on our boat.

3 questions:

  • Where did you purchase the plexi?
  • Was there any chipout when using the router on the plexi?
  • It appears that your forward portlight curves inward slightly with the contour of the cabin top. Was the VHB tape strong enough to 'pull' the lens against the opening or did you have to setup some type of brace to secure the lens against the fiberglass to allow the project to setup prior to caulking?
 

dmax

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Jul 29, 2018
501
O'Day 35 Buzzards Bay
Very nice - thanks for the write-up of your experience, will be doing this myself down the road.
 
Apr 5, 2009
1,620
Catalina '88 C30 tr/bs Oak Harbor, WA
What a nice looking job! Looks very good and thanks for sharing - something I'd like to tackle on our boat.

3 questions:

  • Where did you purchase the plexi?
  • Was there any chipout when using the router on the plexi?
  • It appears that your forward portlight curves inward slightly with the contour of the cabin top. Was the VHB tape strong enough to 'pull' the lens against the opening or did you have to setup some type of brace to secure the lens against the fiberglass to allow the project to setup prior to caulking?
  • Tap Plastics It cost $236.33 plus shipping for a piece of dark smoke 1/4" x 26" x 32" That I cut the four fixed ports from. (2 each side)
  • I used new bits with ball bearing guides and all cuts were perfect and smooth.
  • There is a curve to the full length of the cabin and toward the cockpit it is a warped curve (twisted) I had 1x2's all cut to brace between the lifelines and the lens but did not need them. On the first one, I stuck down a couple of inches on one edge and wanted to move it just a tiny bit but was unable to get it free, seconds after it touched. When they say VHB (Very High Bond) they are not kidding. I used 3M 5952 VHB. The 3rd photo is right after I pressed the rear lens into the tape and you can see the curve and twist. That is held in place with nothing but the VHB. It is a pressure sensitive / aging adhesive which means the bond gets stronger with pressure and with time. I put it into place and then pressed it hard against the cabin with the heel of my hand all the way around the perimeter.
 
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Likes: Ward H

19thol

.
May 2, 2014
111
Hunter 30 St.Petersburg, Fl
Really looks nice, that's one of the jobs I've been gonna do for years, hard to get motivated since the old cracked ports don't leak, they just look like crap. Already bought the tape, now for the hard part!