MkII Fixed Portlight Replacement

[Robert Mann]

Over the last couple of days I replaced the forward starboard fixed portlight on my 2002 boat.  This is what I learnt and the mistakes I made.
 
The leak has been present, from the forward end of the portlight, for a good while. This meant I could get a sharp, very flexible gasket scraper/putty knife into the sealant, at the leak point and work it gently around the acrylic with some light outward pressure on the acrylic.  The window came out in one piece and was reusable.

The tapered edge of the acrylic looked like someone chewed the chamfer on it rather than routed it.  Secondly, there were no foam spacers between the acrylic and the edge of the recess for the portlight. This results in uneven thickness of sealant. However the boat is 22 years old and probably made 20 years without a leak!

Cleaning the old sealant isn't too bad a job, using a scraper, plastic razor blades, acetone, scotch pad and 180 wet and dry paper. Needs some patience and time. I used plastic drop cloth inside taped around the window to contain the debris.

Basic mistake number 1: I masked the window and the opening, inside and out on one day, ran out off daylight and adjourned until the next day. This caused the tape to be difficult to release.

I used 1/2" x 1/8" self adhesive foam tape cut in 3/8" pieces around the aperture at 6" spacings.  I then applied Dow 795 in a 1/4" zig zag to the aperture flange.  I bought the sealant from a construction supply company in Atlanta for about $11 a tube.

Basic mistake number 2: I should have used more sealant than I did. Really pile it on, you can clean it up later.  You need a good amount around the port after, to allow a consistent fill between the acrylic and the hull.

Dow 795 flies further than birthday cake at a toddlers party.  This stuff goes everywhere.  The good news is it's silicone based, so it's relatively easy to clean up, but plan to cover everything around inside of the boat in the vicinity of the port, as you will be moving quickly, if you are working alone.

I braced the window with ratchet straps and a 2x4 brace with two 4" standoffs from the acrylic.  This standoff is about the maximum that you can get between the inner shroud and the port, as they need to be closer to the ends of the portlight due to the slight curvature, and the only place I could see to attach the ratchet strap was the base of the shroud.  This isn't the best way to do it. Although I did not apply a lot of pressure the acrylic still moved downwards slightly.

Basic mistake number 3: I pulled the tape before I realized that I didn't have a complete bond around the whole width of the flange, (if you don't have a full width seal you can see white around the edge of the portlight).
I applied pressure to squeeze the sealant, and in doing so gave myself a mess to clean up later, around the inner edge of the acrylic. At this point I was not happy with one 4" section of the outer seal, so I applied more sealant.  Unfortunately this section was under the brace and this also gave me some extra cleanup.

I pulled the brace off after a day and a half and the seal is intact, continuous and looks decent before final cleanup, which I will do after the 14 - 21 day full cure time.

In the end, this isn't a difficult job, the masking and the bracing need to be well thought out.  I am not sure any of the bracing ideas I have seen, including CTY cradle with 25LB lead pigs, are completely reliable, and ensure the acrylic doesn't slip. Someone showed suction cups on the inside of the portlight, using line and a truckers hitch to tighten the window.  I think this is a better way, certainly than mine, as you can vary the tension across the acrylic. I might try this on the next one this spring.  If you are replacing the acrylic with new, and they are complete with paper coverings the masking becomes easier and more complete.  The price of 4 new portlights encouraged me to try and remover the old ones first.  If this hadn't worked my next fallback was to buy acrylic and try to cut and rout my own from a paper pattern I made before pulling the old unit.

[AndyBC]

Thanks for the great details!  This is the hull deadlight between the 2 cabinets in the saloon, right?  Did it leak onto the wood slats, any damage?

How are your deadlights by the galley and nav table btw?  Mine do not leak right now, but they are badly crazed.  Not looking forward to eventually replacing those.

[Robert Mann]

Andy, it's the forward fixed one over the settee by the table, the one with the pointed end.  The wood is slightly discolored, but it's fixable.  The portlight above the stove also has a leak and I will do this one in the spring. The port side portlights are currently not leaking, these are north facing and not subject to quite as aggressive sunlight.

[waughoo]

Thanks for the write up.  I have been quite anxious about doing this job.  I have planned for the foam tape spacers.  Can you elaborate more how you did this part?  I am a bit curious how to do it so the foam tape doesnt show up on the outside of the glass. 

[Robert Mann]

Alex, I bought Yotache foam weather stripping tape from Amazon. It's 1/2" wide and 1/8" thick and quite dense.  It's self adhesive on one side and it's black so it blends into the sealant.  I cut 3/8" wide pieces and went at it. The basic premise is to allow the sealant a thick enough bed and prevent inward pressure on the acrylic from squishing the sealant completely out.  Remember, the boats aren't made with great precision, so if the portlight material is a bit oversize and the recess a bit undersize the integrity of the seal depends on sealant bed thickness. Don't stress over this job, I did, and it's easier than you are picturing. Bracing and masking/protection are the critical points.  You have approx 15mins to work once the acrylic is positioned in the sealant.

[Gulfsailor]

Alex, I bought Yotache foam weather stripping tape from Amazon. It's 1/2" wide and 1/8" thick and quite dense.  It's self adhesive on one side and it's black so it blends into the sealant.  I cut 3/8" wide pieces and went at it. The basic premise is to allow the sealant a thick enough bed and prevent inward pressure on the acrylic from squishing the sealant completely out.  Remember, the boats aren't made with great precision, so if the portlight material is a bit oversize and the recess a bit undersize the integrity of the seal depends on sealant bed thickness. Don't stress over this job, I did, and it's easier than you are picturing. Bracing and masking/protection are the critical points.  You have approx 15mins to work once the acrylic is positioned in the sealant.

Can you post some photos?

[Noah]

Here are some pics when I did my Mark I in 2019. Used small pieces of foam 1/8 x 1/2 in. high density foam tape as spacers and Dow 795 sealant. My windows had/has screws.

[Noah]

A couple more. Removing old sealant and inside masking. Kind of a messy process.

[Robert Mann]

Gulf, I didn't take any pics of mine, I was stressing getting the acrylic in place. Noah's photos show the foam tape placement  and the fun cleaning the recess and the aftermath. The Mk II boats don't have screws holding the acrylic, so bracing is necessary.  Getting the bracing right makes things a lot easier, and i didnt do well with that. I was cleaning mine up today and I do have a couple of white spots showing where I didn't get a thick enough bed of 795 in place. Although I do have a continuous seal, so it should be good. Also using the existing portlight you need to mask the inside and outside surfaces. The paper protective layer on new units make cleanup a little easier. 

[Gulfsailor]

Thanks for the photos!

Question, do the foam spacers stay after you apply the caulk?

[Noah]

 Yes. The foam spacers stay in place and sealant applied around and on top of them. Their purpose is allow a deeper/thicker sealant bond between the fiberglas and gelcoat so all of the sealant doesn't get squeezed-out when pressing the window against the gelcoat.
The Catalina factory window replacement drawing/instructions can be found on our website (but I can't locate an easy path to them). A .pdf file of them is in the follow thread in Reply 11.

https://c34.org/bbs/index.php?topic=5579.0

[justinsteele]

I just redid mine using 3m VHB tape, I cut new polycarbonate and everything. The whole job was much easier than expected and it came out incredibly well. The worst part was removing and cleaning up the old adhesive. The VHB tape holds incredibly well and then only a little 795 is needed around the edge to seal it so there is no oozing 795 mess inside the boat. My friend did it this way years ago and hasn't had any issues. See this video I followed for guidance https://www.youtube.com/watch?v=MQyjxVUskd8

[ewengstrom]

I also used the 3M VHB tape method and am very happy with the results over 4 years later. No screws, very little mess, etc.
One thing I'll add learning from experience, Mark where the adhesive tape will be on the inside on the window, then sand the surface and the edge where the tape and caulk will actually contact it. Sanding this area prior to installation helps the adhesives adhere better.
I failed to do this on a past project and ended up with leaks. I removed the window, sanded the surface and reinstalled and never had a failure after that.
Another tip is do not cut the new windows too tight, there needs to be enough room for a bead of caulk that will be able to stretch a bit as the boat moves, temps change, etc. Time spent for a good fit on each opening is time we'll spent.
I was able to install all four windows in one (long) day, but it's not really a difficult job if you prepare well.

[Robert Mann]

Eric, I've debated using VHB for the next job, which is the aft, starboard portlight.  On the MK II boats this aft unit is partially over the galley and partially in the rear cabin. This means there is a wide fibreglass area under the acrylic where the transition takes place. This will be a big white chunk that's visible using VHB. Is that the same on Mk I boats? If so how did you address that?

[ewengstrom]

Robert, I painted that area flat black.