When I replaced my portlights on my 29-2, I became quite paranoid about the spray paint attacking the plexiglass and undermining its longevity. I tried looking at the technical data sheets for various paints like Krylon and found they contained chemicals that would theoretically harm the plexi.
My approach instead was to use just Dow 795 for the entire job. The slightly tricky part was making 3/16”x3/16”x3/4” spacers with cured 795 to allow enough silicone between the fibreglass and plexi. The rate of expansion between the dissimilar materials being the concern, and having enough silicone thickness to accommodate that movement. I made up an mdf board shaped slightly smaller than the portlights to hold it in place while the 795 cured for 10 days or whatever it was. The mdf was wedged against the portlights against the lifelines. The 795 just appears black at the overlap and the portlights have held up for 2 years of big temperature swings in Toronto, Canada. Derek McLeod Aileron 1983 C&C 29-2 Toronto > On Mar 13, 2018, at 10:45 PM, Jeremy Ralph <jeremy.ra...@gmail.com> wrote: > > I hope it doesn’t undermine the VHB. Here is where I got the idea... there > is another thread somewhere about it too but can’t find it now > > “If the color of your plastic is not dark enough to hide the grey tape (and > sealant), you may want to paint the inside perimeter of the pane. This will > also protect the adhesives from potential UV attack, but the bond strength > will depend on the paint adhesion. According to some professionals, > silicone-based, high-temperature exhaust paint is both compatible and > tenacious. The area to be painted is the area exposed when you remove the > ring of film.” Don Casey > https://www.sailmagazine.com/.amp/diy/replacing-fixed-portlights > > > >> On Mar 13, 2018, at 10:42 AM, Matthew L. Wolford <wolf...@erie.net> wrote: >> >> Won’t that undermine the bond with the 3M tape? >> >> From: Jeremy Ralph via CnC-List >> Sent: Tuesday, March 13, 2018 12:36 PM >> To: cnc-list@cnc-list.com >> Cc: Jeremy Ralph >> Subject: Stus-List Reinstalling plexi windows...again. >> >> My plan is to paint the acrylic underside with VHT Silicone header spray >> paint. Saw this recommended on a forum somewhere . Anyone try this? Good >> or bad idea? >> >>> From: Chuck Saur <cssau...@gmail.com> >>> To: cnc-list@cnc-list.com >>> Cc: >>> Bcc: >>> Date: Tue, 13 Mar 2018 10:00:35 -0400 >>> Subject: Stus-List Reinstalling plexi windows...again. >>> Happy spring?? I recall someone commented on priming and/or painting the >>> smoke-tint plexiglass edge areas, prior to installing, to hide the the VHB >>> and Dow 795, so all does not show through the smoke plexi against the white >>> cabin side along those edge areas. >>> >>> I have the window dug out, whew, and cleaned up with Mechanica silicone >>> remover and mineral spirits. I actually lost only three patches of knuckle >>> skin. I have also sanded the receiving perimeter of the plexi where it will >>> make contact with the tape and/or paint. >>> >>> I could not find the mention of the painting step in the archive. Has >>> anyone painted this and have advice? I purchased a can of Krylon High-bond >>> plastic paint in flat black. It's waiting in the barn... Thoughts? >>> >>> >>> Chuck Saur >>> Morning Sky >>> C&C 35-3 >>> >>> > > > >
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