Unsuccesfull windows. What to do?

[carlo de leo]

Hey guys,
need some help on this windows...
recently refited in Acrilic, they were fixed with 3M double tape (correct name?) and also used Sikaflex on edges. They are leaking in 3 points on top sides. In the picture one can see there's an off set bevel where they adapt, and is where is the leaks. I allready remade the sikaflex all around.
Possible faults: too much contraction/expansion in the acrilic, need some bolts, small offset, wrong material, what else??
How is this kind of windows is attached on traditional boats (Jeaneau, etc)?
Any help is welcome!
TKS!!!

[Hudson Force]

I have a similar application, but I'm at a far lower latitude. I used the Dow 791 as a sealant after my 3M VHB tape due to it's elasticity for holding with temperature changes. I've had no leaks, but my project outcome is still young and my exposure to temperatures ranges has been from just near freezing to about 90*F.

[Charlie]

Originally Posted by carlo de leo

Hey guys,
need some help on this windows...
recently refited in Acrilic, they were fixed with 3M double tape (correct name?) and also used Sikaflex on edges. They are leaking in 3 points on top sides. In the picture one can see there's an off set bevel where they adapt, and is where is the leaks.

Any help is welcome!
TKS!!!

The method that I used is as follows:

1) Remove windows.

2) Clean all of the old adhesive from joint

3) Sand the joint with 80 grit sandpaper

4) Use acetone to wipe down after sanding

5) Use the sikaflex primer

6) Sand the edges of the lights (windows) where they will touch the sikaflex to provide grip.

7) Adhere Tape wherever you don't want sikaflex and to make a clean joint

8) Place small pieces of rubber washer 3/16" thick to hold the light off of the fiberglass. This creates room for the sikaflex.

9) Find a method to hold the lights in the correct shape of the cabin while the sikaflex cures.

Dow Corning 791 also works but they have no primer

8)

[44'cruisingcat]

Originally Posted by Hudson Force

I have a similar application, but I'm at a far lower latitude. I used the Dow 791 as a sealant after my 3M VHB tape due to it's elasticity for holding with temperature changes. I've had no leaks, but my project outcome is still young and my exposure to temperatures ranges has been from just near freezing to about 90*F.

Second that. Dow 791 silicone has better flexibility than most polyurethanes.

[boatpoker]

I wanted some windows made in Acrylic. My vendor (whom I trust) refused saying the windows were too long (2.5ft) and the expansion/contraction over that length would be a constant problem. I had to re-design.

[barnakiel]

You may have moved the panel to close to the top edge of the gap. If the sealant seam is too narrow, it can detach while curing.

Estimate max panel stretch in its coldest and hottest dimensions then add at least 5 mm each side of the panel for the seam (also between the panels ...).

BTW if there is any bevel, clean and degrease this surface very very well. Some sealants do not stick well to some contaminated surfaces.

b.

[s/v Jedi]

I noticed the use of Dow Corning 795 as well as 791. That boatworkstoday guy on Youtube uses 795. Can't get either in Panama though so I'm gonna try DAP glazing silicone. I hope it has a longer open working time than most of the silicones available.


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[carlo de leo]

Good to hear from everyone!
BTW, I dont want To rebuild the Windows, so Im thinking a way to fix this using same. I think the water that drops from the deck is turning through the upper side of the window and entering all the a gap that formed from the expansion/contraction. So my idea is make a dam like and droping point over the ipsis of the Windows...
Anyway, does anybody knows How Windows work on standard boats like "jeanneaus"?? Material and instalation?

[carlo de leo]

Originally Posted by barnakiel

You may have moved the panel to close to the top edge of the gap. If the sealant seam is too narrow, it can detach while curing.

Estimate max panel stretch in its coldest and hottest dimensions then add at least 5 mm each side of the panel for the seam (also between the panels ...).

BTW if there is any bevel, clean and degrease this surface very very well. Some sealants do not stick well to some contaminated surfaces.

b.

Yes, Those distances were not planned on the upper side, maybe thats one of the major problems. Tks!

[reed1v]

And when the cabin top is hit with a substantial wall of water, the panels will flex, pop out, and you will be left with a very flooded cabin.

[deblen]

MAS Precision Plastics: How To...

[foufou]

a lot of good comments above. the supplier where I get my acrylic near San Francisco advises not to use polyurethanes with acrylic but rather the Dow Corning 795 or GE Silpruf SC-2000. And for the caulk to have the capacity to move it must have some thickness so spacing the acrylic from the cabin sides is advised.

[carlo de leo]

Originally Posted by foufou

a lot of good comments above. the supplier where I get my acrylic near San Francisco advises not to use polyurethanes with acrylic but rather the Dow Corning 795 or GE Silpruf SC-2000. And for the caulk to have the capacity to move it must have some thickness so spacing the acrylic from the cabin sides is advised.

Yes! but there's special polyurethanes for acylic also. Have to be carefull to use those sykaflex 295UV and 3M 4000UV

[carlo de leo]

Originally Posted by deblen

MAS Precision Plastics: How To...

Very good step by step instructions!! tks

[barnakiel]

Originally Posted by reed1v

And when the cabin top is hit with a substantial wall of water, the panels will flex, pop out, and you will be left with a very flooded cabin.

Do you suggest the cabin roof is not held up by structural members but only by the glass?

I ask this a s normally the loads are not taken by the window panes.

b.