hazed acrylic

gkny

Member
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I have some hazing on several ports that I have not seen before.  Normally, there is crazing but this is like a film that is cloudy.  I sanded them out with 1500 wet/dry and then used the Novus products and they were pretty clear but several months later this film has appeared again.  There is no crazing and the acrylic doesn't look all that old otherwise.  Not sure if you can make out the difference between where it is shinier to the right and distinct line where the haze starts.  Any suggestions are appreciated.  thanks.

IMG_0482.jpg

 

gkny

Member
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26
I bought the boat about 4 years ago and the ports were pretty clear.  One of them started to show some hazing so I did what I mentioned in my original email.  This seemed to clear it up pretty well but then the hazing came back.  This is what I took a photo of.  I had assumed that it was plexiglass but I really am not sure.  I have never seen this kind of film develop on the top of acrylic before.  Is this something that would happen if it was polycarbonate?

 

Grrr...

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In addition, that last bottle of Novus is a silicone based 'make it pretty'.  It's fine for an 'in the shed' showcar, but in the environment not so much.  In my experience, there is almost no way to get it completely clear again.  I've considered flame-smoothing as my next attempt after sanding.  But no amount of sanding and polishing will bring it back to 'glass' clear.

Also - you sure it's polycarbonate?  For window applications, acrylic is a better choice because it's harder and more scratch-resistant.  Yes, it can shatter if hit hard, but again in my experience it's worth the extra clarity that they'll retain.

 
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It looks like the novus polish layer has worn away and your seeing the exposed micro scratch's from wet sanding.

You have to use a high speed buffer (extremely very carefully to avoid melting the surface) to polish out the scratches instead of just filling them with acrylic wax.

 

SloopJonB

Super Anarchist
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Try a headlight polishing kit from HF - did wonders on clouded ports & hatches on a couple of my boats.

If it's Lexan you're sorta screwed - that's why you don't use Lexan in that application.

 

gkny

Member
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I suspect that the ports are polycarbonate and I am thinking about replacing them with plexiglass.  The current thickness appears to be 1/4".  The ports are 48" long by 9.5" wide with about 1.5" overlap with the hull all the way around.  This means that the unsupported width is about 6".  Is 1/4" plexiglass sufficiently strong in this application?  They are on the cabin house.

 
Polishing can restore the transparency but if the material is UV sensitive, they'll cloud over in a couple months.  There are UV coatings available to apply after polishing that may get you a couple years.

 

Will1073

Anarchist
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I suspect that the ports are polycarbonate and I am thinking about replacing them with plexiglass.  The current thickness appears to be 1/4".  The ports are 48" long by 9.5" wide with about 1.5" overlap with the hull all the way around.  This means that the unsupported width is about 6".  Is 1/4" plexiglass sufficiently strong in this application?  They are on the cabin house.
Yes

 

gkny

Member
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Polishing can restore the transparency but if the material is UV sensitive, they'll cloud over in a couple months.  There are UV coatings available to apply after polishing that may get you a couple years.
Shenanigan- Are these coatings DIY or do they require removing the lens?  Any coatings in particular that you think would work?

 

gkny

Member
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26
Actually, the line is a scratch but I am going to replace this port anyway.  I know that quite a few installs are without screws but  the original was screwed to the hull as well as being caulked with something like dow 795.  My assumption is that the original was polycarbonate but I plan to replace with plexiglass.  Does anyone know if the expansion is similar to polycarbonate.  My plan would be to replicate the hole pattern ans size of the holes as this seemed to work well before.

 

SloopJonB

Super Anarchist
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Great Wet North
Just drill the holes in the plexi slightly oversize to allow for expansion and do not countersink them - use only surface mounting style heads - pan head, truss head or similar.

 

El Borracho

Sam’s friend
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Pacific Rim
Does anyone know if the expansion is similar to polycarbonate.
38 vs 40 – So no significant difference.

You might as well just glue screw heads onto the outside for all they accomplish with acrylic. My screws fell out periodically but the silicone adhesive pulled the gel coat off the cabin sides during removal. 

 

Israel Hands

Super Anarchist
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You might as well just glue screw heads onto the outside for all they accomplish with acrylic.
I was going to say - if you can eliminate fasteners please do so. Acrylic and frp are dissimilar enough to generate a lot of movement with changing temperatures.  Fasteners invite cracking, so rely on the adhesive to anchor the acrylic if possible.

 

Sailabout

Super Anarchist
I was going to say - if you can eliminate fasteners please do so. Acrylic and frp are dissimilar enough to generate a lot of movement with changing temperatures.  Fasteners invite cracking, so rely on the adhesive to anchor the acrylic if possible.
Use 3M VHB tapes to hold your windows on and then just sika to make them waterproof.
Plexus spray to keep them perfect

 
Shenanigan- Are these coatings DIY or do they require removing the lens?  Any coatings in particular that you think would work?
Sorry to be slow to get back.  They are DIY and can be done in place.  There's a lot of information on the topic if you Google headlight restorers.  Sylvania makes a fairly highly rated UV coating.

 
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