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carbon got milky from wetsanding

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wavy navy
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carbon got milky from wetsanding

Postby wavy navy » Thu Sep 23, 2021 10:54 am

Hi,
I wetsanded my carbon wing to remove scratches. From 400-800-1000 to 1500. Now I it ist in general a bit milky. The manufacturer says I shouldn´t use more than 1500. Also it go some spots where it is milkier than at the rest.

What can I do? Thanks!

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Re: carbon got milky from wetsanding

Postby pmaggie » Thu Sep 23, 2021 11:02 am

The best occasion you can have to tell your wife you need a new foil! :-)))))))

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Re: carbon got milky from wetsanding

Postby Pierrot » Thu Sep 23, 2021 12:03 pm

You mean the water from wet sanding becomes line milk?
Same every time I sand carbon wings/mast/board. I’m guessing the epoxy does that.
I think it is absolutely normal
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wavy navy
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Re: carbon got milky from wetsanding

Postby wavy navy » Thu Sep 23, 2021 12:43 pm

See this pic:
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20210923_134017.jpg

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Re: carbon got milky from wetsanding

Postby consumer » Thu Sep 23, 2021 12:58 pm

sorry not an expert on this so excuse my ignorance, but I think you have to re-coat with clear coat and polish it now to get the shine back?

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Re: carbon got milky from wetsanding

Postby wavy navy » Thu Sep 23, 2021 3:35 pm

@consumer: Sure polisihing would get it shining. It seems that your not into foiling. A lot of guys (including the manufacturer) say that one should stop wetsanding at 600-1500 or 2000 and not do polishing, because that would decrease the performance of the foil.

But what I don´t understand: When the foil came from the factory it looked shiny - how can that be when not polished?
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Re: carbon got milky from wetsanding

Postby BWD » Thu Sep 23, 2021 5:05 pm

Did you use a machine to sand or just a sanding block?

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Re: carbon got milky from wetsanding

Postby wavy navy » Thu Sep 23, 2021 5:20 pm

@bwd: no machine. Some parts with a sanding block, but as it is concave some parts with only sanding paper and finger. Maybe that was a mistake.

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Re: carbon got milky from wetsanding

Postby jonysan » Thu Sep 23, 2021 6:22 pm

When 'wet sanding' the resin coat above the carbon weave, the water (add a tiny bit of washing up liquid to the water) will become slightly milky due to the powdered resin which is being removed. If the water starts to get black/grey, or you notice black/grey water on the production/sand paper, then you have gone through the resin coat, that black/grey is from powered carbon weave, Stop. and re resin the item/foil. start again.
I can't tell from the photo, but it looks like you have sanded through the resin coat in places, you can probably feel the different surface finishes with your finger nail.
I would wet sand it with 400/600 get it smoothish and flowing. then paint on a coat of epoxy resin , leave for 24 hours to become hard enough to sand, then carefully sand with paper up to 1500, then polish with "T Cut" or equivalent Auto polish to get factory shine.
If you are looking for maximum performance, then forget the mirror finish, and leave it Matt.
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Re: carbon got milky from wetsanding

Postby wavy navy » Fri Sep 24, 2021 6:24 am

Thank you jonysan. That was exactly the point. The water got grey. I will follow your suggestions.


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