Very nice work, thank you for sharing your project with us. Mike Skywalker 34' -----Original Message----- From: Gary Russell via CnC-List <cnc-list@cnc-list.com> To: C&C List <cnc-list@cnc-list.com> Cc: Gary Russell <captnga...@gmail.com> Sent: Wed, Dec 2, 2015 8:48 pm Subject: Stus-List Bonded Windows (continued)
For those who were following my post on bonded windows onHigh Maintenance, I have an update and many thoughts on the project enumeratedbelow. I have successfully installed twowindows on the starboard side and replaced the acrylic on all the hatches andcan say that the project has been very successful. I have terminated my project at this point asthe temperatures are now too low for the VHB tape which requires a temperatureof greater than 60 degrees F for application. Here are my observations: #1. Plexus is evilstuff and should not be allowed on a boat. It is too hard and tenacious a bond. Because fiberglass and acrylic have such a different expansion coefficient,fracture of the acrylic is assured. Removing the stuff is impossible without destroying the gel coatunderneath. I tried a sharp bladebetween the fiberglass and the acrylic and all I managed to do was rip up thegel coat. #2. Before removingthe windows, make a template out of some thin plywood (or other material) becausethe window will (no doubt) come out in pieces and you will have nothing as areference for making the new windows. #3. I finally wassuccessful removing the acrylic with a 5/8” router bit set to a depth equal to thethickness of the acrylic plus the thickness of the Plexus. I actually used a Roto-Zip instead of arouter as it had a smaller footprint and was easier to handle. I free-handed the router to cut through theacrylic and into the Plexus. It’s riskybut effective. Don’t cut all the wayaround the perimeter, but leave tabs to support the window. Otherwise, the window will sink under theweight of the router and you will cut into the gel coat. You can break out the tabs later. #4. Once the windows wereout, I used West System epoxy thickened with low density filler to repair anydamage to the gel coat. Fortunately, all my gel coat damage was limited to the area under the windows. Once the windowsare out and the damage is repaired, the rest is fun and easy. #5. I cut the newwindow out of 3/8” Plexiglas using a pattern router bit (sometimes called a Formicatrimmer). I used masking tape folded inhalf lengthwise to stick the new Plexiglas to the old window (or template). I ran the tape at right angles to insure thatthey wouldn’t slide in either direction with respect to each other. It does a very nice job and is quiteeasy. I then used a 1/8” round offrouter bit on the outside edge of the new window for cosmetic reasons and a 45degree chamfer bit on the inside edge to make room for the Dow Corning 795silicone. #6. I installed the3M VHB 4991 tape on the coach roof and masked around where I wanted the windowto go. This would help me locate the window and provide the masking for the Dow Corning 795 siliconeto follow. I also masked the edge of thenew window for the same reason. #7. Now cones thetricky part. You only get one shot withthe VHB tape, because once it is down, it is not coming up. I tried adhering two small pieces of acrylicto each other with about two square inches of VHB tape, and I can assure you,you won’t pull them apart. VHB isamazing stuff. As a guide, I mounted twosmall wooden blocks to the masking take below the window with a small piece ofVHB tape. By attaching it to the maskingtape, I was sure I could get it back off. Actually, VHB doesn’t stick very well to masking tape anyway. I also stuck a small wooden block to the maskingtape at one end of the window as well. This allowed me to set the window on the two bottom block and then slideit over to the end block before pushing the window into place. By all means, make several trial runs withthe film still on the VHB tape before removing the film. Once the film is off you are committed. I pushed the window in place and it lookedperfect. Then it is simply a matter ofsquirting the Dow Corning stuff into the gap and smoothing it out with afinger. As soon as the silicon issmoothed out, you can remove the masking tape and pour yourself a stiff one,while you admire the fine job you have done. #8. There was concernexpressed that the VHB tape would be visible through the window, and it wassuggested that the window should be painted with Krylon Fusion Black. Actually, the VHB tape is the same color asthe Plexus which is not visible, so the VHB won’t be visible either. No paint is necessary. I used the darker shade of grey Plexiglas andcan say that it look spectacular. Thedarker shade really “pops” and the contrast is particularly attractive (in myhumble opinion). The darker color makesit difficult to see into the boat, but has a minimal effect when lookingout. The VHB is not visible at all. #9. There was alsoconcern expressed concerning whether the curvature of the coach roof wouldcause a flexing force to peel the VHB tape. I can say that the radius of curvature is very large (>20 feet) andthe forces are thus very small. 3/8”acrylic over those lengths is quite flexible. I see no problem at all. #9. I have postedsome pictures on Google Drive and I think you can view them at: https://drive.google.com/folderview?id=0BwQRSP2fYIFmemxYOGlVcHNUNVk&usp=sharing I am new to posting pictures, so if you have trouble seeingthem, email me and we can get it fixed. I will add more pictures as they become available. #10. Needless to say,I am thrilled with the outcome so far. Ihave also re-glazed the hatches using the Boatworks video and they came outspectacular as well. The only differenceI made from their recommendations is that I bedded the acrylic in butyl tape insteadof the Dow Corning 795 because it was much easier to get a uniform bead andthat was the way it was done from the factory. I still filled the gap around the windows with the Dow Corning 795. Boatworks is right, the Dow Corning 795 is nice stuff. #11. If I have leftanything out or you have any questions about this post, just give me a shout. Gary S/V High Maintenance ’90 C&C 37 Plus East Greenwich, RI, USA ~~~~~~~_/)~~~~~~ _______________________________________________ Email address: CnC-List@cnc-list.com To change your list preferences, including unsubscribing -- go to the bottom of page at: http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com
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