Leaking Window

[Ken Juul]

The aft port window that stretchs between the head and the Nav station has been my achiles heel all summer.  I must have removed and rebedded it at least 3 times using 3M 4200 following all the advice not to over tighten the screws until fully cured, etc.  The leak moves, so i think I have several problem areas.  Looking at the other windows it appears that they just have a thin rubber gasket with no other sealant.  The gasket is present on the leaking window, I have been applying the sealant on top of the gasket because it appears to be well bonded to the top liner.  I've tried the larger screws and get a nice bead flowing out of the seal as recommeded by Stu in a previous post.  Am I using the wrong sealant?  Why won't my gobs of sealant do what the thin rubber does on the other windows?  I'm checking with Catalina parts on the availability of a new seal.  Any suggestions!

[Gary Ambrose]

Ken,

I am about to leave myself wide open on this suggestion. When confronted with window leaks I have very good luck with a small silicone bead added above and around exterior frames. Water shunted away from the windows usually does not find a way behind and to the interior. It really works. And has helped with the most stubborn leaks, as well as being a quick repair when re bedding is not feasible. The silicone is invisible and can be easily removed.

[Jim Price]

No advise from me but I think Catalina Direct carries gaskets for the sealed ports.  You might want to look at what they have in addition to working with Catalina factory.  I cannot help otherwise because (knock on wood) I have not experienced any leaks yet.  

[Ron Hill]

Ken : Don't feel like the "Lone Ranger" people have had similar leaks.

I wrote an article in the Mainsheet on this problem.  Don't remember the exact sealant that Catalina used, but the usual problem is that with a curved lens, people tend to "squirt out" the caulk.  That's why Catalina recommends the use of 1/4" small pieces of double sticky tape every 6 ".
I'm cruising and reciting from memory so look it up in the Mainsheet Tech notes.

BTW, don't believe there's a gasket - what you're seeing is the old caulk.  

[cat_jim]

It is a sealant called "Dow 795".  Nothing else sticks to the plexi.

[SteveLyle]

If you have the early fixed windows, then you've got a problem.  Not sure what year hull #1090 is, but then again I'm not sure what year/hull # Catalina revised the design - I thought it was in '88, but it may have been later.

Catalina used a poor design initially for the fixed ports.  Let us count the ways....

The windows are plexiglass, with the edges beveled, that fit into an opening molded into the cabin top that consists of a matching beveled edge with a lip 'seat' for the window.  Countersunk ss screws are fitted through holes drilled in the windows, and screwed into the lip.

The first and biggest problem with this design is the use of the countersunk screws.  Screws/bolts are not recommended for attaching plexiglass or polycarbonate, since the holes create stress concentration points.  If screws/bolts must be used, the worst option to choose is to countersink them.  Plexi is weakest in tension, and the countersunk heads put the periphery of the screw hole in tension, leading to cracks radiating out from the holes over time.  Not good.  A flat head screw, or a finishing washer under an oval head screw, with a simple, non-countersunk hole would minimize this problem.

The second problem is the beveled edge.  The edges of the window thus come to a point, where of course the material is thin.  Cracks can thus easily start at this thin edge, and radiate back into the window.  Not good, and not readily worked around.  My theory on avoiding this (which I haven't tried yet) is to eliminate the bevel on the window, making them smaller with a squared off edge, and simply use more sealant between the window and the opening (since the gap will be larger).

The third problem is the sealant.  Easily dealt with, but you have to know what you're doing.  The windows come with a paper 'skin' that protects them in handling/shipping.  When you peal this skin off, there's a residue of adhesive left behind.  In addition, when the beveled edge is machined onto the window, it's possible to get a plastic 'fuzz' on the surface of the bevel.  When you set the window into the silicon sealant, you'll be ok at first, but over time the sealant will lose adhesion as with the adhesive surface and the machined surface.  The way to deal with this is to clean off the sealing edges of the windows very carefully - both chemically (lacquer thinner) and mechanically (sandpaper).  

Ron's right in that it's a good idea to use spacers between the window and the lip to ensure that all the sealant doesn't get squeezed out.  However, that spacer won't help you if you lose adhesion because the window isn't clean to begin with.

Another problem with the bevel is that when the top edge of the window loses adhesion with the sealant, the bevel is like an open mouth begging water to flow down off the cabin top into it - there's no natural drain (say like there would be if the bevel was on the outside edge, not the inside one, so it would shed water).

When #75 became mine in '01, all the ports were cracked and leaking.  I went to Catalina and had replacement's made that I installed in '02.  No problems until this year.  Katrina passed overhead dumping 6" in 24 hours.  All the ports leaked around the entire edge.  I had the adhesion problem that showed up after 3 years.  I also had cracks radiating at the screw holes and from the edges, although if these were causing leaks I couldn't and haven't been able to tell.

The fix this time was to remove the windows (no problem there, there was NO adhesion with the sealant), and reseat them.  I'm living with the cracks for now - they don't seem to be a problem at this  point.  Next time I replace the windows, my thinking is to go with a squared off edge and either flat head screws (maybe through bolt them) or finishing washers.

As for sealants, Dow 795 is a silicon sealant.  Nothing particularly special about it.  Any good silicon sealant will work, as long as the windows present a clean surface.

Interestingly enough, I was browsing old Tech Notes the other day, and saw in the Nov '94 edition where Catalina highlighted that the key to leak-free windows with this design was to ensure that the window sealing edge surface was "perfectly clean".

Cruising Concepts sells a package for sealing these windows.  See
http://www.cruisingconcepts.com/retroftwin.htm.  $275 with the windows, $60 without.  Uses butyl tape on the lip/window seal.  Anybody tried their approach?

[dpenz]

I installed two replacement windows from Cruising Concepts.  I am waiting for a "round tuit" to do the other two.  Each window took about half a day.  The tedious part was removing the original window and the remaining gasket material and cleaning the mounting lip.

Cruising Concepts furnishes a roll of rubber tape.  This tape is a low durometer, probably about 40, which means that it is quite soft and sticky by itself, there is no additional adhesive.  The good news is that it sticks quite well to the fiberglas and to the window.  The bad news is that it is so soft that the tape can't be handled without stretching it, which changes the thickness.  So when applied to the mounting lip, the tape inevitably has high spots and low spots, and wide spots and narrow spots.

The windows are furnished with drilled holes and with black stainless steel screws and washers.  These look quite nice and I have not had any cracking problems.  In my experience, there were not enough screws to seal the window.  The large window has eight, if I recall correctly, which is the same number as the original window.  But more screws are needed to  pull the window into intimate contact with the sealing tape all around.

This may have a lot to do with the weather.  In warmer weather, the tape will be more elastic and thus may seal better when first applied.  In my case, both windows leaked substantially at first.  I ran a bead of silicone around each, and this stopped the leaks.  By now, after a summer of exposure to the hot sun, I can tell that the gasket has extruded some more.  Still no leaks, so either the silicone is doing the job or maybe the tape gasket is sealing better now.

I think the soft rubber tape gasket is a good idea.  It conforms to the fiberglas, which is not a perfectly flat surface.  But I have been thinking that an installation tool, a stiff steel flange rim, would be a good idea.  When installing a window, you would use this flange temporarily on the outside of the window, and it would apply uniform pressure all around the perimeter of the window.  After the gasket has had some time to set, the flange would be removed and the screws replaced.

But I would probably still run a bead of silicone around the thing to be sure!

[Stu Jackson]

Ken,

Thanks for quoting me, and I'm sorry you're having such bad luck.  As I recall, our port problem occurred on a rainy day at anchor.  At least we were there for the waterfall!  No rainbows, though.

It seems to me that the trick is to get enough sealant in so that when you tighten the screws the sealant oozes out, especially on the top.  Since we were at anchor, I did NOT have the gasket that's been mentioned here, just a tube of good old West Marine sealant, not even Boat Life.

With excess sealant oozing out the top, it sure didn't look pretty, but all we did was trim the excess off with a knife.  I liken this to what I did with our forward starboard Beckson and our chainplates:  if (and when) I re-seal anything, I put enough sealant on so it oozes out.  At least then I know, just by looking at it, that I've actually done something!

I think Steve's right about the design limitations of the embedment, and Gary's right about the "squeezing out" which worked for us.  Sure, it doesn't look like it's right out of the factory, but it works.

[Ken Juul]

We had 4 days off and friends in town so I haven't even thought about doing the window.  He used to be a charter captain/delivery skipper who now has a land job and no boat.  Spent every minute of a great weekend on the water.  Will tackle the window this weekend.  I think the problem is I haven't been removing what I thought was a rubber gasket.  I'll clean everything as suggested by Steve and I think I'll add a couple of screws to the top edge and hope for the best.