With what shall I seal my windows?

[Keylime 0]

My windows leak, and my boat fills up. The windows were added by a previous owner, they're adhered with some kind of rubber, but it's come loose in several places. I plan to drill holes through the panes and fiberglass, remove the panes, clean the surfaces, apply a sealant, replace the panes and screw bolts through the pane and the fiberglass. Does anyone have feedback on this approach? Could you recommend a sealant? Sikaflex 291 seems to be an option - though it doesn't seem to be recommended for plexiglass ("Sikaflex®-291 must not be used to seal plastics that are prone to stress cracking (e.g. plexiglass, polycarbonate, etc.)"). Is this gonna be a problem? Otherwise a silicon sealant?

 

Thanks!!

[Keylime 0]

found these in other forums:

• Sikaflex MS: https://nzl.sika.com/en/46072/sealants-fillers/exterior-joints/walls-and-facades/sikaflex-ms.html
• Fixtech FS200: https://www.seamac.co.nz/new-products/fixtech-fs200-310ml-cartridge-black
• Dow Corning 795: https://www.dow.com/en-us/pdp.dowsil-795-silicone-building-sealant.01595717z.html
• QUILOSA MS35: https://www.glueguru.co.nz/shop/BRANDS/QUILOSA/QUILOSA+MS35+Adhesive+280ml+Cartridges.html

Any preference? Maybe I won't need the bolts?

 

[alibaba 71]

How much overlap have you got? ie from the inside of the cutout in the cabin side to the outside of the window pane? If you have 20-25 mm, then the best way seems to be to use glazing tape around the cabin side to hold the window on. Then, mask carefully level with the outside of the window, then fill the gap between the glazing tape edge and the top[outside] of the window - hope that is clear. The glazing tape not only holds the window on firmly, it provides a 5mm gap for the adhesive sealant.

There appear to be plenty of different sealants about which would work, but the only one I have used successfully is Dow Corning 795. It's best to give a slight key in the window material, and the easiest way to do this is to use a kitchen scourer - the green ones and just rub the inside edge of the window with it.

I've done two sets of windows - D28 and a Lotus with the above method with not failures.

 

[Island Time 1,175]

Don't use bolts or screws, that's where the leaks start. Modern glues is all you need. Search the forums on here, lots of talk about this

[wheels 543]

20 hours ago, Island Time said:

Search the forums on here, lots of talk about this

Wow, a great example of people not looking before posting. The very answer being in the thread directly below this one.

[Keylime 0]

9 hours ago, wheels said:

Wow, a great example of people not looking before posting. The very answer being in the thread directly below this one.

guilty

[Keylime 0]

On 6/06/2021 at 8:42 AM, alibaba said:

How much overlap have you got? ie from the inside of the cutout in the cabin side to the outside of the window pane? If you have 20-25 mm, then the best way seems to be to use glazing tape around the cabin side to hold the window on. Then, mask carefully level with the outside of the window, then fill the gap between the glazing tape edge and the top[outside] of the window - hope that is clear. The glazing tape not only holds the window on firmly, it provides a 5mm gap for the adhesive sealant.

There appear to be plenty of different sealants about which would work, but the only one I have used successfully is Dow Corning 795. It's best to give a slight key in the window material, and the easiest way to do this is to use a kitchen scourer - the green ones and just rub the inside edge of the window with it.

I've done two sets of windows - D28 and a Lotus with the above method with not failures.

 

I found this video that I think explains your method (can watch at double speed)- but with VHB tape. I've seen that butyl tape is recommended over VHB tape - though in this video the VHB tape that failed was being used without a sealant.

 

 

[Island Time 1,175]

I don't use the VHB at all. The Quilosa has great initial bond, and is only workable for a few mins. I use lots of it, put the window in place, brace if needed to hold there (if its got lots of bend, for example), then use a scraper and then thinners to clean up the ooze. Small bits of timber - or matchsticks - can be inserted until the initial bond is taken, to ensure sealant thickness, then removed and the holes filled - make certain that there is lots of matchstick sticking out for removal!

[wheels 543]

I do suggest the use or turps for cleanup. I have noticed any acrylic that has been wipped with Thinners seems to craze much earlier than acrylics that have not. Maybe it is coincidence, but I have always wondered if thinners may remove something from the Acrylic surface that causes UV to break it down faster.

The issue of using the sticky tape stuff is the UV attacking the Adhesive over a long time and likely causing the tape to release eventually. The Sika products use a paint on stuff that is actually about stopping the UV from attacking the Sealant, not just better adhesion to the acrlyic.

[Keylime 0]

3 hours ago, wheels said:

I do suggest the use or turps for cleanup. I have noticed any acrylic that has been wipped with Thinners seems to craze much earlier than acrylics that have not. Maybe it is coincidence, but I have always wondered if thinners may remove something from the Acrylic surface that causes UV to break it down faster.

The issue of using the sticky tape stuff is the UV attacking the Adhesive over a long time and likely causing the tape to release eventually. The Sika products use a paint on stuff that is actually about stopping the UV from attacking the Sealant, not just better adhesion to the acrlyic.

I would be removing potentially fragments of what I guess is rubber (butyl?) from the acrylic, and preparing the surface for adhesion to butyl tape, and Quilosa MS35. I was anticipating using acetone to clean up rubber fragments. Better to use turps? (Isn't turps a thinner? What thinner do you not recommend?)

[wheels 543]

The Turps comment was for " wet" adhesive. Which is usually recomended on many of the products for clean up.
Acetone doesn't seem to hurt the Acrylic immediately. But I found that some acrylic had crazed in areas that I had also used either thinners or Acetone when I installed it. I had just assumed it may have been the solvent that caused the damage. That is simply an observation though.

[Keylime 0]

2 hours ago, lateral said:

Do NOT use acetone, lacquer thinners, MEK on acrylic or polycarb.

It will haze at very least, or craze. Been there done that.

Definitely weakens it.

Abraid it off or rubber stripper wheel. Tape up where you want to remain clear. Use blackout primer after to edge

of rebate/FG on acrylic.

 

Thanks - I’ll keep away from acetone. Regarding the primer, for the Quilosa ms35 I don’t think it needs a primer, but I was going to etch the acrylic with a kitchen scourer. Is the primer needed for the Butyl tape?

[Island Time 1,175]

Yep, turps on Quilosa, while wet. Sorry, should have been clearer! Once it's dry, it must be mechanically removed...

And no primer, no special prep. Just clean, dry surface on the boat, and the window, and away you go..

 

[Zozza 272]

At IT's suggestion, I will be Quilosa'ing my boat windows in a month or so, and will report back.

Good tip re turps to remove excess while wet - check .
Thanks

[Ex Machina 341]

On 9/06/2021 at 1:41 PM, Zozza said:

At IT's suggestion, I will be Quilosa'ing my boat windows in a month or so, and will report back.

Good tip re turps to remove excess while wet - check .
Thanks

Yep me too …thanks to all who gave valuable feedback in the “other” window thread !