Thursday, November 26, 2009

Portlight gasket replacement

Replacing the portlight gaskets on a 1990 Pacific Seacraft 37.

This post is offered to other Pacific Seacraft owners who may want or need to replace their portlight gaskets.  I don't offer this solution as The Ultimate solution, but it was the best I could come up with.  If anybody solves this problem in a more elegant or reliable manner, please let me know!

Luckness is a 1990 Pacific Seacraft 37.  The portlights are the rectangular New Zealand portlights.  If you look closely at the portlight lens, bottom right corner, there is a logo from the company in New Zealand which produced the glass.  This solution will likely not apply to other portlights.

The portlights gaskets are moulded and one piece.  The glass lens fits into a slot in the gasket, the gasket is fitted into a bronze frame and the frame is clamped down to the portlight frame bolted to the hull to form a seal.  Or that was what used to happen - after 20 years the gaskets were starting to fail and several of them no longer formed a reliable seal.  Three of the 10 were leaking, with the others on their way.  I could see no way to repair the gaskets other than to replace them.  An example of an old gasket follows:

The portlights were made by a company that is no longer in business.  The gaskets for the portlights are custom and I had no luck in sourcing them.  The Pacific Seacraft factory could offer no advice in sourcing the gaskets.  After searching around Seattle and online, I finally came upon a solution which appears to be working for me.

An example of a completed portlight, with a brand new gasket follows.  The white flecks in the picture are rain drops, not damage to the lens.

Be warned that if you start this project, once you take the gasket out of a portlight there is no going back.  Removing the gasket is a destructive process - you won't be able to put it back again.  Once you take the gaskets out you are committed to solving the problem of finding a new gasket somehow!

If you proceed with this project it may also be worth while buying the material and constructing a gasket or two to get a feel for it.  Before you destroy what you have, you will want to gain confidence in what you're replacing it with.

Also, you will need patience for this project!  It will take several weeks to complete.

No warranty!

I'm not an engineer.  I have not had the new portlight gaskets installed for a long enough period to really know how reliable and robust this solution is going to be.  The result appears to be working, but I won't really know for a few years.  I need to subject the new gaskets to some real world abuse.  It may well be that this solution starts to fail a year from now.  If that's the case, my next option will be to buy new portlights from New Found Metals and have them installed.  The approach described here is much cheaper and allows you to keep the original bronze portlight with the boat - but it is offered without any guarantee or warranty!  I'm some random dude on the net - if anybody follows these steps you would be well advised to think through each step carefully, examining the materials and seeing if they or the process can be improved on.  Or perhaps you want to try some completely different approach.

Enough about that.

Materials required

The solution I ended up with was to build a new gasket out of two pieces.  In a nutshell, I glued the pieces together, fit the result to the lens and used Sikaflex to bond the new gasket into the bronze frame.

I found the gasket material from McMaster Carr.  The two items are:
    Self-Gripping Vinyl Edge Trim with Metal Core.  1/4" opening, 1/2" wide: 24175K16
    Neoprene rubber bar, 1/4" thick, 1/2" wide: 90125K53
I bought 50' of each and have some left over.  You should plan on building three or four extra gaskets to experiment on or to replace failures.

As I live in a wet climate, I also needed to build blocks to fit into the portlight frame once I had removed the lens.  I built three of these (two small, one large), using starboard with gasket material glued onto one side, two bolts attached with a piece of wood to hold the block into the frame.  To build these, the gasket I used was:
    Neoprene rubber sheet, 1/4" thick, various sizes.  durometer rating: 30A   9455K156
cut the board to size, cut the rubber to the board, glue the two, drill holes, attach bolts, attach small boards.

The gasket adhesive I used during the project was 3M Super Weatherstrip and Gasket Adhesive, in black.

I also used Sikaflex 291 for bonding and sealing.  Many paper towels and q-tips for cleaning, many latex gloves, styringes found in the epoxy section of my local chandlery (Fisheries.)  Tin snips are handy for cutting the vinyl trim.

The process

There was some trial and error involved.

Build the blocks for the portlights:

Pick a portlight.  Put the block into the portlight frame:

Now you need to remove the old gasket.  Read the warnings above about this step - you can't go back once you do this!

Cut around the gasket, freeing it from the sides of the frame its in:

The gasket can now be pulled out.  Grab a piece of the gasket with a pair of pliers and pull.  You're trying to pull the gasket out from around the lens - you're not trying to pull the lens out at this point.

Once you have a piece of the gasket free of the lens, removing the rest will be easy - simply keep pulling and the lens will pop free.  If the gasket you first grab breaks off, move over and try again.

You'll need to clean the bronze frame of all the old sealer as well as cleaning the lens of old sealant as well.  The sealer is a little tenacious, getting it off the bronze frame is a little tedious.  I ended up scraping most of it off and then using a circular wire attachment on my Dremel tool to get the rest off.  This step was messy, I hung pieces of plastic up to try to isolate the black pieces flying of the dremel as much as possible.  If you have cushions on board, you may want to move them to a different part of the boat, this is messy.

Cleaning the glass is easy - I used a glass cleaning tool with a razor blade attached.  This tool was also useful for trimming the neoprene gasket to size.  There is a picture of it later.  If you are removing multiple portlights, it would be wise to label the lens so you know where it came from - I kept the lenses matched to their original portlights.

Clean the lens and bronze frame with mineral spirits.

I covered the lens in blue tape in order to keep the new sealant off the glass in later steps.  When you do this, make a mark on the tape to indicate where the New Zealand logo is.  You will want to place the finished portlight back into its frame in the correct orientation, so you need to know where the logo is.

At this point you have a clean glass lens, and a clean bronze frame - time for the gasket.

Building the gasket to wrap around the lens will initially take some trial and error.  I first built a gasket set, let it set for a few days (the adhesive gets stronger over a period of 4 or 5 days) and then tested it to destruction - pulled it apart.  I built another, installed it on the lens and again tested it to destruction.  I encourage you to do the same.  Get a feel for the materials.  Also note what type of stress the gasket will likely endure in practice.  Pulling the old gaskets out wasn't too difficult.  The new ones need to be strong in the right directions, not all directions.

The new gasket will experience its strongest loads while under compression in the closed portlight.  So things like the gasket adhesive and sealant needs to be strong enough to hold the pieces together when the portlight is open, but when it is closed everything presses together.

To build the gasket you first need to determine a good length for the vinyl trim.  Press some of the vinyl trim onto the portlight.  Arrange for the start/end of the trim to be on top of the portlight when its closed, not the bottom.  Go around the portlight pushing on more trim, coming back to the start and cut it off.  This step is actually a little tricky.  You need to adjust how far you press the trim onto the glass so that when the portlight is closed the gasket hits the frame at a good place.  If you press the trim on as far as it goes, the gasket may end up being too far inside the frame.  You also have control over how tight a radius you make at the corners.  It will likely take some trial an error for the first piece of each of the small/large portlights to decide on a good length for the trim.  I ended up with the vinyl trim being 38 3/4" for the large portlight and 27 1/2" for the small.  You may end up with something different.

Once you decide on a good length for the vinyl trim, cut the neoprene bar roughly an inch longer.  I found it easiest to glue the two pieces together while they are lying flat and straight on a table.  I had two boards which I placed the trim between.  I also had a bar that I could press on top of the bonding pair overnight, and two clamps to keep them tight.

The vinyl trim has a tab inside of it - I put that tab on the outside of the boat.  Sand down the outside of the trim to roughen it up slightly.  Do the same with the neoprene bar.  Clean them both off with mineral spirits.  Apply the 3M gasket adhesive, follow directions.  Attach them, clamp, put on bar, weight it down.  I offset the neoprene bar from the start of the vinyl trim - I didn't want to have one spot where they both met.

After drying, the gaskets now look something like this:

Let the glue dry for a day.  Once I started this project and got the sizes right, I could build one gasket per day.  This was sufficient as the other steps are slower.

Now you need to put the gasket back onto the covered lens for a final test fit.  Start with the two pieces:

Attach the gasket, fit it into the frame, adjust the tightness of the fit, repeat until you have a good fit.  Its surprising how as you vary the size of the radius and how far the gasket is pushed onto the lens how you can change the length of the gasket used by several inches.  You'll probably end up redoing your first few after you complete all the steps - don't sweat it, by the third or forth you'll have the hang of things.

Test fit the gasket, you want some overlap between the vinyl trim and the frame, but not too much:

Once the gasket is on, you want to add more blue tape to the vinyl trim and make registration marks so that you can return the gasket to exactly this position.  Also draw around the gasket in the blue tape so that you can cut the tape back to inside the gasket.  You'll want to leave a bit of a gap between the gasket and the edge of the blue tape to allow for a good seal with the sealant.

Remove the gasket and cut the tape on the lens:

Now you can seal the gasket to the lens.  Squeeze a bead of Sikaflex 291 (or an alternative sealant you use) into the trim.  Again, you'll get a feel for how much to use after a few experiments.  You want enough to seal well, but not so much that it interferes with pressing the gasket onto the lens.

Once the trim is full of sealant, put it back on the lens.  Start in the middle, lining up the mark you made to indicate the middle of the gasket and lens.  Press it on toward both ends.  I preferred to have a small amount of sealant advance as I pressed the gasket onto the lens.

Once the gasket is again on the lens, clean up the sealant that has come out and then fit the lens into the portlight frame and clamp it in.  You want the gasket to adapt to the frame shape as it dries.

Let it dry overnight in the frame.

You're getting closer now!

The neoprene bar is too long and you need to cut it back to the right size.  Take care with this step - if you cut too much you may end up with a gap which will cause you to start over with this portlight.  Been there, done that.  I used a glass cleaner razor for this step, putting the razor blade on the neoprene at the spot I picked and then rocking it back and forth to cut.

Apply the gasket adhesive to the vinyl and neoprene.  I would stick a small nail into the corner where the neoprene meets the vinyl to keep them separated while the glue gets tacky.  Then press together with a clamp.  I used a short popsicle stick (bought a bag from the kids art section of Fred Meyer) to spread the clamp force out across the seam.

Give it a short while for the glue to fix.  While the portlight is out of the frame its easy to add more sealant to the edges of the vinyl trim to create a good seal.  I used a small syringe I found in the epoxy section of Fisheries which I filled with Sikaflex.  This gave better control over a small bead.

Apply sealant to the edges, then cleanup to give the bead good shape.  I used q-tips and paper towel cut into small rectangular pieces for this.

Let the portlight lens dry overnight again.

The final step is to seal the lens and new gasket into the frame.  Rough up the outside of the vinyl trim with a piece of sandpaper.  Apply a bead of your sealant into the frame, then put the lens in, cleanup the sealant that oozed out.

The vinyl trim will not meet the corner of the frame.  Fill this gap with more sealant if its not full already.

Cleanup the sealant again.  I found small popsicle sticks useful for leveling the corner areas.

Let the combination dry overnight.

This is also a good time to clean the portlight clamps.  I used my dremel tool with a wire brush attached to clean out the threads on the bolts.  Apply a little lubricant so the clamps close well.

Come back the next day, take off the clamps, rip off the blue tape and admire your new portlight!

The first few closings will be difficult, but the gasket will form to the portlight over a short amount of time.


This is a pretty tedious project and takes some time.  But the result seems satisfactory so far and the benefit is that I have new portlight gaskets and was able to keep the original portlights in the boat.

If anybody has a better solution, I would love to hear how you've solved this problem.

Feedback is welcome.


  1. Wow! Thanks for this. I'm about to perform the same surgery on my Flicka. This helps a lot.

  2. Hows it holding up after these years. Need to do the same on our PS44

    1. The portlight gaskets are actually holding up very well. As I tell anybody who is considering this project - if you can find an easier way, go with it.

  3. Thanks for posting. I am considering purchasing a 20 year old PS 40. I will need to adjust the offer again. I'm glad your solution is working for you. However, it looks torturous. I just completed rebedding the ports on my Cape Dory 36. The Spartan portlights provide a simpler solution by design. The glass is sealed into the frame on its own using silicon (32 years and seal between the glass and frame is still good). A round EDPM gasket material is the contact cemented into a grove on the fixed frame and seals against the glass when closed.