Replacing Fixed Windows Research [Master Thread]


O34 - Los Angeles
+1 for 795 sealant. But one cautionary note, make sure you buy and use a fresh tube. I did a port light with a tube that was ~2 years old and discovered that it doesn't ever really dry. more like butyl, except less sticky.

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
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Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Recent threads, some of them with historical opinions, recommend butyl rubber for portlight frame installation into the cabin house.

I feel (strongly) that caulk is much better for portlights. Yes, butyl is marvelous for deck fittings, as popularized by Mainesail. I don;t think he ever suggested using it for portlights.

Butyl requires pressure, which bolted deck fittings provide in spades. Ericson portlights are not bolted on. They're held in place mostly by the low adhesion of the sealant, and the flange which resists forces from the outside (breaking waves). The interior cover, with its many screws, is mainly cosmetic, and if you honk down on the screws it just bends the aluminum and ruins the cover.

The openings for portlights in the Ericson cabin house are famously approximate, presumably so the metal of the frame has a little float. In any case, they were not made as precision holes for a tight fit. There can be gaps. Caulk, by its nature, flows to fill gaps. Butyl doesn't have the same property.

Painters tape makes caulk overflow on the exterior easy to clean up. Caulk doesn't ooze over time, either, as butyl can. I've replaced portlights both ways and concluded that caulk is the way to go.

Butyl works, but caulk is better. Use lots of it, as Ericson did.



Member I
I went with new portlights from New Found Metals out of Port Townsend Wa. Pricey but quality.. I have the old ones out of a 74 32-2. if anyone is interested, there not in to bad of shape.


Sustaining Member
Butyl works, but caulk is better. Use lots of it, as Ericson did.
Christian, What you write about caulking makes a lot of sense but as you also point out,"Butyl works..." Back in 2019 I pulled the two fixed ports from the port side of my E32-3 because both were leaking around the frame. Both were set in an amazing (and scary) amount of caulking and required a lot few hours of work to pry the ports out and many more, back at my workshop, to get all the caulking off the frames. Because of that mess I decided to use butyl tape when re-installing the ports so that if they needed to be removed again the process would be easier and I just didn't like the idea of caulking. If the butyl tape didn't work then it would be much easier to get them off and then use caulking. That was five years ago and there has been no sign of leaking. So, as you say, butyl works.

Lots of old caulk that the water got passed.

Maybe they cut this opening after a few beers at lunch??!!

Temporary cover while fixed ports are being worked on.

Temporary cover made from painted plywood with a foam strip between the cabin top and the cover.

Trimmed butyl tape seal.


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Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Copied from Post #52

Mr. Scarlett said:
. . .
One thing that blew me away was the absolutely horrible cutouts on both. Rough, wavy, bulging. The larger port has less than 1/8" of cabin sides to bond to on one of the upper corners. This does not take away from the build quality of mine or anyone else's Ericson, but wow.
We found this too, though the actual cut-outs weren't as bad as some people have shown and there was a tight contact between FG outer shell and plywood inner fascia.
fixd prtlt hole 03.jpg

. .
fixd prtlt hole 02.jpg

However, like yours, in some spots there was precious little overlap between the portlight frame and the cabin sides.
fixd prtlt hole 01.jpg

Before reinstalling, I was inside adjusting the port for even placement in the hole. Then from the outside Donna drew a pencil line around the frame. We used this to lay out the tape which, in addition to aiding cleanup, allowed us to align the port. It was still tricky because of the caulk squeeze-out over the tape. By the fourth portlight we about got it right.
fixd prtlt hole 04.jpg

s/v "Kismet", E35-3 hull # 238 (1986) Universal 25 w/ some XP upgrades


Sustaining Member
Rather than trying to get the OEM black rubber I bedded the replacement panes with butyl and they've stayed dry as a bone.
Can you describe this in more detail? Did you use no pre-made gasket material at all, and only butyl? Isn't a gasket needed to keep the glass in the frame? Today, I pulled out two of my port lights and hope to pull the other two tomorrow, and I'd like to re-do the glass-to-frame installation before they get re-installed.

Tin Kicker

Sustaining Member
Can you describe this in more detail? Did you use no pre-made gasket material at all, and only butyl? Isn't a gasket needed to keep the glass in the frame? Today, I pulled out two of my port lights and hope to pull the other two tomorrow, and I'd like to re-do the glass-to-frame installation before they get re-installed.
It’s been several years and I believe there are more photos somewhere around here, but no I did not use pre-made gaskets. Was just on the boat last week and there were no leaks. I used the 3M black butyl that any auto parts store carries to seal the acrylic pane and hold it in a fixed position. Then used Dow 795 to fill the rest of the channels, which also will keep the panes from settling in the butyl over time. Each pane is essentially double sealed and Heaven help whoever needs to clean them out many years from now.


Sustaining Member
I have been following most of these threads on re-bedding of fixed port lights with great interest. I have read about, and experienced, the difficulty of removing port lights bedded with various modern squeeze-tube caulks. And I know that butyl tape, while great for bedding things bolted down, is not ideal for something as delicate as our fixed port lights. I can now share my limited experience in using an old-school product called Dolfinite for fixed port lights.

When I got my 1987 32-3 in spring of 2021, there was obvious rot at the aft corner of the aft-most port fixed light over the nav station. I posted about that issue nearly 2 years ago. Soon after that post, I removed that port light, cleaned it up, and rebedded it with Dolfinite. Dolfinite bedding compound has been around for a long time. It sells for around $80 for a quart, not much less by volume that 3M 4200, but it never goes off like an open tube of modern caulks, and it never hardens. And it is very easy to work with.

Two years after using Dolfinite on that one port light, with no signs of leaking, it was time to remove the other three fixed port lights for eventual rebedding. Aided by Anti-Bond, as recommended by Christian Williams, it took a total of about 4-1/2 hours to remove them (90 minutes each!). In contrast, I was able to remove the Dolfinite-bedded leak-free fourth port light in only eleven minutes.

When I eventually re-install the fixed port lights, they will be bedded with Dolfinite.

I have noticed, from my own port lights, and photos of others' here, that typically great massive gobs of "adhesive sealant" materials are commonly used for bedding these port lights. But it occurs to me that there is little need for "adhesive" for our port lights, but only for "sealing", and no need at all for "filling", which is all that most of that stuff is doing.

Dolfinite spreads with the consistency of thin peanut butter, so it is easy to apply. Cleanup is easy, and can be expedited with mineral spirits. The manufacturer claims that it never hardens, but instead it can dry or cure to something like a stiff wax. When I re-bedded my port aft port light, I applied the Dolfinite to the aluminum flange only, where it comes in close contact with the fiberglass hull. There is no value in material placed between the port light frame and the hull material, except at the outboard surface. After installation of the interior trim for the port light, a cloth soaked with mineral spirits can easily remove any Dolfinite which oozes out from between the frame and the hull.

After struggling to remove the port lights, with concerns about breaking the glass, damaging the hull, warping the frame, and even whether successful removal is possible, the ease of using Dolfinite bedding compound looks really appealing.

Port light removed after two leak-free years after bedding with Dolfinite. Elapsed time for removal: 11 minutes.

Dolfinite bedding compound after 2 years. It resembles a stiff wax.

Waiting for the Anti-Bond to break down the caulking. Lots of wedges in use in hopes of breaking the bond.

Ninety minutes of struggle, using Anti-Bond, the fixed port light finally lets go.
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Contributing Partner
Blogs Author
Dolfinite sounds promising. One of the main reasons I used butyl was for ease of removal after struggling like you did to remove the portlights. I wonder if that is the same stuff that I see the Tally Ho builders using extensively?