I took the leap this weekend and removed my fixed portlights. They were crazed, but not leaking but, couldn't help myself—the crazing just offended me—so I opted to replace them. New ones are being made at a local plastics shop, using old ones as a pattern. I have screws in mine which were easily removed and I will reuse them for install. The two forward windows came out in one piece. But not the aft ones. Due to a solid coating of sealant under them at the aft pillars (by the head) the aft ones snapped into multiply pieces. The first one rear one I removed resulted a big piece falling in the drink and the pillar section chiseled into small chucks. The second one I removed more carefully, resulting in four intact pieces that I seamlessly pieced back together to use a suitable pattern. Both sides are symmetrical including the hole pattern fro the screws.
Now my question:
I have studied the Catalina instructions that call for 3/8-1/2 x 1/8 thick foam spacer every 6-8 inches to hold the window slightly off the fiberglass to prevent the 795 sealant from completely squeeze out when the window is pressed into place. BUT, doesn't that act as a barrier and eliminate any sealant from contacting/bonding the acrylic to the fiberglass where each foam spacer is located? Am I missing something here? When I removed the old windows, interestingly, despite what the Catalina shop drawing shows, there were no visible spacers underneath that I could see? Debating whether to use spacers or not? Thoughts please?
Noah check this out.It may be applicable for you.
https://youtu.be/MQyjxVUskd8
Thx Glenn, I have seen that video. However, I am still opting for Dow 795 over VHB tape, due to historical success and our C34's windows that are bigger than Andy's, and harder to position. I just need to sort out the pros and cons of spacers.
When my portside fixed port started leaking when we were at anchor during our first winter (i.e., rain), when I removed it and rebedded with the silicone we had onboard, I do not recall any spacers. I think your idea about using the 795 and no spacers is just fine, the screws have been holding mine in for 20 years! :D
Noah any chance of some pictures when finished?
Oops [Glenn] NOAH:
Forgive my ignorance on your windows. You're talking about plexi windows that were siliconed on? If so
Yes. Defo 795 it's tenacious and has the best adhesion property and the best elongation before failure property.
1) you don't need screws and many leave them off.
2) IIRC the blocks are partial, ie the 795 seals "outside" the blocks, which sit on the inboard edge.
IIRC becki did hers might be able to answer that.
I also know others who did them if you want to me to connect you up directly.
K
Ken- i sort of get what you are saying with spacers. If they are not as wide as the channel and were set close to the inner radius of the window, sealant would flow around outside edge.? Perhaps. I am happy with screws. The screws will help hold in window while sealant cures and makes it unnecessary to make some sort of jig or suction cups to press/hold in place. Pics. sealant yet to be removed. Cracked section during removal on pillar. Screw for sample depth. Old window before removal showing screws And my assistant. I am cleaning/scraping off old sealant this week.
The CTY drawing shows that the small spacer blocks are way smaller than the total mating/sealing surface and are on the inboard edge, not affecting the 795 that's beyond (outside) the small blocks.
Noah!
My fixed port side large port developed a small crack at one of the screw holes. Made a pattern and took it to Catalina Yachts in Largo, not far from where I live. They used my pattern and fabricated me a new replacement port, but refused to add the holes. They said that the holes are a source of problems when the screws are tightened a little too much and are totally unnecessary when using the Dow Adhesive.
So if you have the holes drilled be careful not too over tighten the screws.
Noah
Along that line, many of the C-30ers who do use screws, they are temporary, remove them and fill the holes w/795. YBYC.
Thx for info Bernie. The screws were very easy to take out when removing old windows and I will be very careful not to over-tighten them when I install the new windows. Been raining here for two days (go figure!?!) but today I start removing old sealant and prepping surfaces for new.
Nosh i got my fixed Windows from Catalina their supplier had the orig. Specs. I didn't use spacers but per advice used 795 with weights hanging on the Windows with screws not fully tightened no leaks 5years.
The old sealant cleans off pretty easy/quickly and effectively with a sharp paint scraper used carefully. Not my favorite job for a guy with an artificial knee :shock: Next comes sanding.
Noah be thankful they didn't use 795 originally - you'd be going in for a new shoulder 😳 as well.
That looks a mess but it will sure be worth the effort whence you get'erdone.
I can't wait to see the new ones.
I just replaced one of mine last fall. Used VHB tape with 795 around edge. My glass shop would not bevel the edge like the original, but I think that actually helped to get more 795 in the gap. No screws. i had the port side window made too, but will save that for another day (it's cracked but not leaking).
Rob
I'm planning on replacing my plexi windows also. As Noah says it's the crazing!
When I replace mine, which also have screws, I'm going to use Snaps on the screws so that I can sew an external cover for the windows to prevent SoFla Sun Damage.
Paul
Paul,
You might want to reconsider that idea. When you pull on snaps, they, well. uhm, pull. You really don't want to be yanking on the screws that hold your fixed portlights in place.
Everyone I've ever seen with sun covers over their fixed portlights has installed separate snaps above and below their portlights.
Please think about it.
Good point Stu.
I could do that, and that raises the question: Are the screws really necessary?
Paul
Paul
The screws aren't recommended by CTY due to issues of cracking around them. You CERTAINLY don't need fasteners to hold the plexi on when using 795.
There's a C30-er who went to elaborate measures to use screws and not have them put stress on the plexi. D'oh. Why? If you use them to temporarily hold the plexi while the 795 cures, then CTY recommends you remove them/fill the holes w/ 795.
As far as using them for snaps -- the screws don't hold the windows -- the 795 holds them. If you overdrill the holes to assure there's no stress on the plexi, and after the 795 cures back out the screws and put in your snap heads, assuring they don't compress the plexi, then there should be no interference. But that means can't be tightened down to secure them. You'd probably need to dap epoxy on the threads so they don't loosen up (not being tightened down against the coachroof.)
Possibly Lift-The-Dot fasteners would put less pull on the screw threads?
There's some other newer snap-type fasteners that require less "pull." My bro does canvas work - I could pass it by him if you like.
ken
Noah - I've replaced all fixed light ports with replacement lenses from Catalina and using the Dow Corning 795.
Using the foam spacers is not that problematic. Just make sure there is space around them for the glazing caulk to flow AND don't hold back with caulk. Better to put it on too think than too thin. Be sure to blue tape all areas around the window frame inside and out. Lastly I did not use screws and have not had any problems.
I initially rebed two using the Catalina technique.
Last year, I purchased four new lites (since the old ones were crazed so badly and cracked around the screw holes) and did the other two using Andy's technique.
I found using the VHB tape to be much easier, cleaner and professional looking. I'm going to rebed the other two new ones this year with VHB.
One benefit of using the VHB tape was there was no need to use screws or a complicated clamping device.
I did find that the new lites I purchased (I think from Catalina Direct) were just a bit too big and needed to be sanded.
Do you recall if the VHB tape was #5952, and where did you buy it? Did you use 1/2", 3/4", or 1" wide? Thanks.
I ordered 3M VHB #4991 (0.5") from amazon.
Rob
Quote from: Jon W on May 03, 2019, 09:02:07 PM
Do you recall if the VHB tape was #5952, and where did you buy it? Did you use 1/2", 3/4", or 1" wide? Thanks.
I used 5952 in 1" and trimmed the excess on the interior of the frame. 1/2" might be ok and would leave more room for the sealant between the lite and hull.
I believe the 4991 is thicker but does not come in black.
On both aft windows, there is a solid section where the bulkheads are. I framed the VHB around the edges and then spread some black adhesive in the middle just so the color would look uniform.
On doing the c30 replacements I've seen talk about painting some (all?) of the surface(s?) black beforehand. I have a mk-I so don't am not familiar with the particulars but it seems to be the instructions. Maybe from CTY?
To close the loop: i just completed my fixed portlight replacement project. Not something I ever want to do again. I followed the factory instructions using Dow 795 sealant, and foam tape spacers. however I did reuse the screws. I placed the spacers slightly back from the edge of the window to allow the sealant to flow around to the edges of the windows. The sealant is a messy process. Lessons learned.
1. Be careful applying sealant. I used a caulking gun and then spread around with a putty knife.
2. Pull tape and masking paper right after applying. I opted to wait and tool/carve it with razor blade the next day. Very tricky and painstaking job to get correct, especially in compound corners.
3. Watch out for air bubbles and voids in sealant. I had a few that I discovered when I tooled joint flush with razor blade. These may have been caused by my putty knife technique. None of the bubbles/voids went all the way through and I considered them to be mainly cosmetic. But I (hopefully) fixed them by applying another dab/patch of sealant over these 4-5 small areas. Time will tell if it will bond to itself. The cure time is listed as 7-21 days so I am hoping against the old adage/warning that "new" silicone won't bond to "old" does NOT apply here to Dow 795 over itself, one day later.
4. Screws. I cleaned and reused the original screws. Not an easy job. But I like the shiny "bling" and they help hold the window while sealant cured. I later reinstalled them with minimally tightened, in affect gluing them back in with 795. It was a messy job to keep clean. If you opt for screws I would go with two sets—one to install and then remove when sealant sets and duplicate clean set to go in for final finished job. Still messy to neatly dab 795 on these tiny screws but at least you won't have to clean the goop off the first set, just toss them.
Last pic is view through new head window looking out at my neighbor's C36.
Nice job. Your hard work shows. A real labor of love
Thx! I forgot to mention. The install is better to do as a two-man job. Thankfully, Jon W. assisted me down below. He is responsible for the clean edges inside! We used my boat as a warm-up/test platform. When it comes time to do his windows, we will be practiced and it should go smoother!
Whew! Some comfort on patching divots/voids in Dow 795 sealant. Thx to Jsail's research, it is confirmed that Dow 795 can be patched (i.e. "new over old"). Unlike other silicone, Dow 795 silicone adhesive will stick to itself. See pg. 51 of loooong instructions doc.
https://consumer.dow.com/en-us/document-viewer.html?ramdomVar=7547043403372662019&docPath=/documents/en-us/app-tech-guide/63/63-61/63-6132-01-structural-sealant-glazing-manual-asia.pdf
YES. That's why CTY recommends removing the screws (if used temporarily) and plugging; it will cure into 795 that's around the hole.
795 is "space age" LOL. Better living thru chemistry. And all that.