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I see Permatex makes a clear RTV silicone, I think I'll go with that one. I like the idea of it being easily removable. If it fails, it will be an easy job to replace. I'm not concerned about the color (even though this one is clear) because I've painted the edges of the new dodger glass just like the original, so the sealant will be out of sight.
Thanks for the advice!
SM 233 Iteration
Boston, MA, USA
On Thu, Apr 26, 2018 at 11:25 AM, James Alton lokiyawl2@...
I did some research on using Mineral Spirits and Paint thinner on Plexiglass to see if my past experience in working with these materials seemed to be accurate. I found that there seems to consensus that 100% Mineral Spirits is considered safe for Plexiglass. While “Paint Thinner” (for oil based paints) tends to be mostly Mineral Spirits it can apparently also contain a mixture of other solvents, some of which could be harmful to Plexiglass. So I want to correct my statement that Paint Thinner is safe for use on Plexiglass, even though I have used various brands of solvent labelled “Paint Thinner” for decades without any problems. It is possible that I might have just been lucky in selecting Paint Thinner brands that were safe and I sure don’t want an Amel owner to find one that isn’t based on something that I posted.
In my research, I also found that apparently Isopropyl alcohol is often used to clean silicone from aircraft canopies and is apparently considered safe but I have not used it myself so don’t know how well it works for this application.
Well I have used mineral spirits/paint thinner (for oil based paints, not urethanes) on Acrylics for 40 years on countless boats without any obvious negative effects but that is the only testing that I have done. I always tape to keep the worst of the caulking off. Scrap the bulk of the material off with something soft like the soft plastic spreaders used for applying bondo and then finish cleaning with rags and the paint thinner. Also, if you only clean up a small area at a time, your caulking will be easier to remove. Once you disturb the bead and spread it out thin, it cures much more quickly.
Bill R. is definitely right that if you use a lower strength silicone that the future removal will be much easier. My reasons for using the 3145 is because the caulking can last the life of the new plexiglass without leakage and I would rather fight with the removal aspect at the end than to deal with leaks and having to redo the caulking. There seems to always be a piper to pay! (grin) The 3145 btw is also non corrosive so the stainless screws fair a bit better than if you use the more common silicones with the acetic acid in them. I think that there are other non corrosive silicones with a lower strength than the 3145 out there but don’t know of any that are clear or white off hand. Perhaps others can help.
Best of luck with your project.
Silicone RTV. If you get any squeezed out when screwing down, cut it with a razor and peel it off. Let the screws do the securing and the RTV, the sealing. The next owner will be thankful.
Pat and Ian, that might be a workable idea, but it would be a lot of work. Getting the masking tape right to paint the edges (to cover the sealant) was a huge job, and this would be the same again.
James, both of your ideas seem like much less work. I had not considered using longer screws. That still leaves the problem of getting the butyl tape into position, and it's very frustrating to cut... so I think perhaps I'll go the silicone route. I also was not aware silicone could be easily wiped off acrylic. I thought I would have to use a solvent (like acetone) which would attack it. I'm surprised mineral spirits is safe; I usually consider that harsher than acetone.
Does anyone have a recommendation for a silicone?
SM 233 Iteration
Boston, MA, USA