New cabin windows. Need guidance on painting and VHB

[Cdn_bacon]

I thought I knew what I was going but I need some advice. My old windows are being replaced. They were previously adhered with something that looks like super glue (I know). Everything is removed and prepped. New acrylic is in hand and cut to size. I have VHB 5952 tape, black that I’m going to double up in thickness and I have some primer 94.

The old windows had no paint on the adhered surface but it did have a black line painted about 1” in from the edges to hide the face of the interior window frame.

So… I was planning on avoiding painting because the VHB is black. I am going to paint a line to mask the interior frame or is the 2074 acrylic dark enough to hide the white surface of the interior frame?

Should I just paint the entire section and put the VHB tape on the paint? Can I use a high temp rustoleum paint? If I dont and use the primer 94, will that show since it’s yellow (per the can description). I’m nervous of the paint bond not holding once the tape is applied since there is a very slight curve to the glass (1/8” over 30”) and I’m not using screws to hold the glass in place due to another issue I have.

Appreciate some advice here.

[chris mac]

I don't have experience with using vhb tape, I've used it but not for windows.
When I replace our windows I went with dow 795 for the whole thing. Bonding and sealing. Bear in mind our windows have big curves top to bottom and left to right. So a perfect fit wasn't likely, nor was a uniform gap. After cleaning the fibreglass opening and sanding the acrylic at the bonding locations and taping off everything, I "painted a 1/4" layer of 795 over the fibreglass side. I then applied 2 thick beads on the acrylic. Then placed the acrylic in and pressed while sliding around slightly until it seated well with slight squeeze out on all sides. Placed shims to maintain position and left it to set.
The next day I caulked the outer edge(a gap of about 3/8" all the way around) and let that set.
2 years in and no problems.
The key to acrylic lenses is they move at a much higher rate then the fibreglass. So they must have the ability to move. Dow 795 has a very good adhesion and stretch capability. But... There needs to be a good thickness there to allow stretch without losing adhesion.
The vhb tape should allow the same thing, with enough thickness. It probably has the same issues holding the acrylic though, so rough sanding is essential.

[tkeithlu]

You can take the flatness out of the window panels with gentle application of heat. Acrylic is thermoplastic. In the extreme case you make a dummy curve, put the piece on top, and bake it at a bit over 200 F. In your case it may be easier to use the ports as the curve, and a heat gun to soften it.

Simple mounting on black butyl tape is the favorite method among forum posters in the past.

Good luck with your project.

[marcjsmith]

Cdn bacon

When I did my fixed portlight on my moody I ditched the frames and used vhb tape as my primary method of adhesion. Originally I had frames, but ditched them

I made sure the vhb tape covered all visible gelcoat so I didnt use any paint.

I had a mild bend in the cabin lines. In hindsight I should have done some heat to add some curve to windows, But the vhb initiation high grip I didn’t have any issues. After bonding with the vhb, I followed up with Dow 795 inside and out

The dark tint of the windows also helped