Acetone can soften the acrylic and leave permanent marks. Also (I've been told) it leads to premature crazing. Furthermore, it doesn't really soften old silicone which is likely what the old windows have. It can be used on gelcoat, but is not _good_ for gelcoat. It will soften new gelcoat, btw--only use on very well cured gelcoat.

However, acetone is surprisingly not as toxic as it seems. Visit your local nail salon to see folks soaking their fingers in it. That said, I still strive to keep it off of me.

Denatured alcohol is safe for most surfaces including most plastics, but doesn't do much to dissolve old silicone. DeBond Marine Formula (have to order online) will soften old polysulfide, silicone, even 5200, and is safe on gelcoat, but I do not know what it will do to acrylic.

For windows, I would carefully scrape the cabin-top clean with scrapers and maybe some DeBond. I've never cleaned old windows--I just replace them if they are off for any reason. Cost to replace is quite reasonable...

:: Tell us more about NOT using acetone or solvents. What
:: should be used and why no acetone or solvents. SDK
::
::
::
:: :: No posted instructions that I know of, though you can
:: :: search the internet and find various approaches people
:: :: have taken.
:: ::
:: :: Generally windows leak through the screw holes, though
:: :: if not well sealed originally they can leak anywhere.
:: :: The cabin top flexes a lot when walked on and will break
:: :: the seal for the windows. If the windows are in very
:: :: good shape and seem well sealed you can try removing
:: :: offending screws, sealing them with silicone, and
:: :: replacing them.
:: ::
:: :: To re-bed the windows they must be removed, all old
:: :: sealant carefully cleaned from boat and windows
:: :: (difficult as you should avoid using acetone or solvents
:: :: to clean the boat or windows), and then resealed. It may
:: :: be a good time to replace them--if you take the old
:: :: windows to Tap Plastics they will fabricate new windows
:: :: for a very reasonable price. Have them drill the screw
:: :: holes also (oversize to allow for expansion), as
:: :: drilling through lexan without a proper drill will cause
:: :: micro cracks that spread later. Note that Tap will bevel
:: :: and/or melt edges to your specifications for a very nice
:: :: look.
:: ::
:: :: After breaking several windows during races, I switched
:: :: to polycarbonate windows, which scratch more easily but
:: :: are much much stronger.
:: ::
:: :: When re-bedding windows, you want to have a good
:: :: thickness of silicone. One trick I learned for this is
:: :: to cut tiny squares of white electrical tape and placing
:: :: them near (1/4" away from) the screw holes, so when you
:: :: fasten the window in place there is still a thickness of
:: :: silicone to make the seal. Don't tighten the screws
:: :: until the silicone has set up somewhat, and then don't
:: :: tighten them very much. Remember, you want a thickness
:: :: of silicone to make the seal.
:: ::
:: :: Masking over everywhere that silicone should not go
:: :: (window, cabin top) is a good idea, as silicone that
:: :: gets loose will both make a mess and make future
:: :: painting / repair jobs go poorly.
:: ::
:: :: I have an Express 37 with the original windows (very
:: :: hazy but no leaks). They have very thick silicone layer
:: :: (perhaps 1/8" thick). I'm not sure what trick they used,
:: :: but it has been very effective over the years.
:: ::
:: ::
:: ::
:: ::
:: ::
:: :: :: Where can I find how to repair Express Window water
:: :: :: leak?
:: ::
:: :: :: I heard it is common for Express 27. Any article or
:: :: :: instruction for the repair?