replacement of glue-in fixed ports

[Hayden Watson]

I have made mant post both inquiring and discussing my experience in replacing the acrylic fixed ports in my C30 Mk2 but did not create a thread of my own with the write-up of my experence here on SBO. This is the posting I did on the C30 Owners group and a couple of years overdue but better late than never.

I finished installing my 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 paring knife that was thin and flexible enough to fit into the small gap and cut the old silicone.
I then used the original lenses 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 old lens to the new rough blank with SailRite SeamStick tape.

Then 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. 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. 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, 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.

This is the setup just before positioning the new lens. One change I would do is not mask the cabin top until after the lens is set into the tape because it is hard to gauge where to place it. We were too wide which made it more difficult to smooth the surface after applying.


This shows the three tape hinges. This tape is 3M Preservation Tape and should be on every boat. I will stick incredibly well to fiberglass and stay waterproof all winter long. When you want to remove it, it comes off clean with no residue left on the surface. It was made to tape on the shrink-wrap winter covers.


The lenses stuck into tape without push sticks and no sign of edges lifting. These lenses were flat 30 seconds prior to photo and perfectly curved.


finished product speaks for itself!




So nice to have clear window for the first time in 20 years.

 

[Hayden Watson]

I was concerned that the tape would not be strong enough to hold the new lenses on the curve of the cabin so I had sticks cut to fit between the life lines and the each end of the lens.
Did not need to worry about it. once it hits the VHB it ain't go'n no-where!

 

[Hayden Watson]

I ordered the Chemcast dark smoke 1/4" x 37" x 32" for $123.33 plus shipping and cut all four fixed ports from that sheet. I also got enough to re-lens the companionway doors and 3/8" for the v-berth hatch. https://www.tapplastics.com/.../acrylic_sheets.../519

 

[Ralph Johnstone]

Thanks for your write up (it goes into my collection) as your fixed port mountings are 100% identical to mine on my 1999 H-310 :

The first question that comes to mind concerns how you got the finished appearance on your interior if you have the thickness of the VHB holding the glass out from the frame :

I would think it would show open gaps due to the thickness of the VHB or protrusions of DC795 as you seem to show. How do you avoid having a mess all over the glass and the adjacent finish ?

Then 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.

This I haven't seen this idea before. Please clarify, is there any 795 present when you are adhering the glass into place against the VHB ? I always thought that getting 795 on the VHB would destroy its adhesive properties. Do I understand that the 795 is uncorked only after the glass is held tightly in place on the VHB ?

I take it the 45º bevel on the back side of the glass is then filled with 795 to add an extra barrier against water intrusion ?

One last question for this session, given an arrangement like this on the forward fixed hatchlight of my H-310, is the VHB placed :

Strangely enough, after 24 years of exposure, the forward fixed hatchlight looks brand new. Not a blemish and crystal clear. The side fixed portlights however, have varying amounts of damage from UV over the 24 year. This one looks like the product of a drive-by shooting :

.............................................. although the exterior is unblemished. These do require replacement and I've got to get to work on these sooner rather than later.

 

[Ralph Johnstone]

@Hayden Watson , this picture may clarify my question a little better than the previous example. Sorry for the repeat.

 

[Hayden Watson]

Thanks for your write up (it goes into my collection) as your fixed port mountings are 100% identical to mine on my 1999 H-310 :

View attachment 219981

The first question that comes to mind concerns how you got the finished appearance on your interior if you have the thickness of the VHB holding the glass out from the frame :

I very carefully placed the VHB right along the inside edge of the opening so that it would make a black gasket around the frame. I am not sure what the squiggly line is at the lower left corner because I have never seen in on the boat. I will look the next time I am out there. when I laid the VHB down, if it hung over the edge at all, I used a single edge razor blade to trim if flush. The VHB that I used was about 45-mil thick and it is all closed cell foam. That smooth black edge makes a very nice border.

View attachment 219982

I would think it would show open gaps due to the thickness of the VHB or protrusions of DC795 as you seem to show. How do you avoid having a mess all over the glass and the adjacent finish ? :

Because the VHB is continuous around the inside edge of the opening it forms a dam to seal out the 795 from getting onto the visible inside part of the lens.

This I haven't seen this idea before. Please clarify, is there any 795 present when you are adhering the glass into place against the VHB ? I always thought that getting 795 on the VHB would destroy its adhesive properties. Do I understand that the 795 is uncorked only after the glass is held tightly in place on the VHB ? :

You are totally correct. If the 795 is installed before the lens is stuck to the VHB would make a complete FUBAR! The 795 goes in after the lens is stuck to the VHB which makes a seal to keep the 795 off the inside of the lens.

I take it the 45º bevel on the back side of the glass is then filled with 795 to add an extra barrier against water intrusion ? :

This is not quite correct. On my boat, the recess that the lens fits into has a 45º bevel on the edges that softens the transition. I put the bevel on the back side to allow it to match the bevel on the cabin top. Your boat may be different. I also used the bevel to make the new lens about 1/8" smaller on each side because the factory lenses were too tight to allow for a decent thickness of 795. If you have too thin of a layer, it will not stretch enough to resist the thermal expansion caused by the sun on the black lens being hotter than the white fiberglass.

One last question for this session, given an arrangement like this on the forward fixed hatchlight of my H-310, is the VHB placed :

View attachment 219984
:

In this situation, I would probably put the VHB on both the inside (to form the finished gasket) and on the outside set back 1/4" ti 1/2" to hold that edge and provide backing for the 795 to be squeezed into. I would suggest using a primer on either the gelcoat or the part of the lens that attaches to the cabin top. There is a primer that is like black paint that will prevent any of the white gelcoat from showing through.

 

[Hayden Watson]

@Hayden Watson , this picture may clarify my question a little better than the previous example. Sorry for the repeat.

View attachment 219987

I think both but the red line would be set back from the edge so that you can squeeze the 795 into the gap behind the lens.

 

[Ralph Johnstone]

OK, that's it, I'm sold. I have got to get to work on my two bad fixed portlights this winter if only for something to do. I'll collect the materials this winter and rough cut them ready for a fast re and re in the spring.

I've read about 3M VHB for several years and thought it was one of these things that's a little too good to be true. According to everyone who's used it, yourself included, VHB sticking to anything is a one way trip, it's not coming off again. I guess so, if you can't trust 3M, who can you trust ?

You're directions for applying the tape are the most detailed of any I've ever seen. And I've got many procedures saved.

I tripped over this in my archives and now see why you have the 45º bevel on the backside of your lenses. I don't even own a Cat but have everything on ports and hatches from every boat mfg. going.

I am not sure what the squiggly line is at the lower left corner because I have never seen in on the boat.

Don't beat yourself up over the mystery squiggly line on the inside of the port FG surround. I'm going to say it was left there from the original installation of the portlight when the boat was mfg. I've got them on my ports as well when the glass was installed in 1998. I think one would do severe damage trying to remove the old 795 when installing new glass.

 

[Hayden Watson]

Don't beat yourself up over the mystery squiggly line on the inside of the port FG surround. I'm going to say it was left there from the original installation of the portlight when the boat was mfg. I've got them on my ports as well when the glass was installed in 1998. I think one would do severe damage trying to remove the old 795 when installing new glass.

View attachment 220009

I will look the next time I go out but suspect that it might be some deformation of the edge of the opening from the knife I used to cut the old sealant.

 

[Ward H]

Great write up and discussion! Thanks

 

[Crazy Dave Condon]

Ditto

 

[william24424]

Thank. you for sharing. I'm inspired to replace mine this winter.

 

[Qomomoko]

Thank for the DIY write up!

 

[thinwater]

Good write up and discussion.

Both of the ports on my F-24 had come loose at the front edge. Based on some math, observations of the condition of the old VHB tape, and that the front corner is thinner and provides less bond area, I concluded that thermal expansion (and age--1996 boat) was the culprit. The windows were ~ 5' long.

The window had a vertical brace in the center, so when replacing the ports I broke them into two sections, leaving a gap about 1/4-inch wide between them and mounting to the brace. With smoked windows, you really cannot see the break. The windows on my PDQ 32 were done this way, in sections, and had no leak problem.

My conclusion is that windows more than about 3 feet long experience more thermal expansion than VHB tape and Dow 795 can deal with. Break them into smaller sections if you can.

The hardest part of the job was removing the old VHB tape. They put it on wide, and it took many hours with a heat gun to persuade it loose.

[PDQ 32 windows. The sides are similar. The screws are not needed, but I used them for snap-on window covers.]

 

[william24424]

Inspired, I started and realized Wrong way is to use thick knife... I quickly changed directions and used a flat metal putty knife that went through old sealant with little pressure, so all four portlights are out, waiting on plexiglass 1/4" dark smoke.

 

[Hayden Watson]

Inspired, I started and realized Wrong way is to use thick knife... I quickly changed directions and used a flat metal putty knife that went through old sealant with little pressure, so all four portlights are out, waiting on plexiglass 1/4" dark smoke.

yep, thin knife is needed. I used a paring knife that has a very thin blade with a nicely tapered point. I could stab it into the gap and work my way along with repeated stabs. Then I went back and started sliding it along with a rocking motion. Once I got one corner free, it got easier because I would put a wedge into the gap which stretched the old sealant at the leading edge of the cut and made it slice through.

 

[thinwater]

Windows have always come out for me, once they were UV damaged, but I'm thinking heat could help.

I wonder if a wire would work, once you got it through one place.

 

[Hayden Watson]

Windows have always come out for me, once they were UV damaged, but I'm thinking heat could help.

I wonder if a wire would work, once you got it through one place.

I had heard that a windshield cutting wire would work so I got one but for me it did not work. I could not get the wire to slide through and cut the adhesive. The gap in my windows was too tight.

 

[Crazy Dave Condon]

As a dealer, I used fishing line using it in a sawing mode back and forth. It requires a second person. No damage

 

[william24424]

Finished fixed port light replacement yesterday...just have to screw on trim pieces. Original crazed acrylic were from 1988 Cal-33. Great winter project, took approx. about 2 hrs to remove, 3 hours to prep openings, 2 hours to cut materials, 3 hours to install, 1 hour to caulk... total time approx. 12hrs. over several weeks (worked few hours each weekend)
'Boatworks today' you tube, has the professional DIY instructions, done in a climate controlled shop, well lit, and explains the process well... However, I was bent over inside my winter cover, moving around a dirty boat deck, banging my head on frame, contorting between stanchions/lifelines/openings... yet it still came out spectacular...I too now can see clearly after 20 years of crazed living. Thank you for posting your project., here is mine.