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Polishing Windshield


milotron

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Hey folks,

The glass in my K is vintage 1995 and is in reasonable condition except a haze is becoming more evident on the windshield. Side windows are fine.

I have the 3 stage polishing kit and have given it a try with not a lot of success so far so I have a question:

Is the haze on the interior or exterior surface of the windshield? Anybody have success removing this?

 

iain

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It's the internal structure of the plastic that is compromised. It's done. You could sand/grind/polish thru the windscreen and it would still be hazy. Kinda like a bad pair of head lights. 

If you can live with it great. If not you'll need to replace the glass. 

-Matt

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Things about acrylic windshields....

the plastic is cast (liquid polymerization) between two sheets of glass., annealed, then formed and cut to fit... (Polycast acrylic sheet)

The glass like smooth surface stays pretty well but is sensitive to UV light and erosion from everything that hits it.  Some chemical cleaners over its life add to the erosion.

If you look closely, surface issues are not too hard to see.

Most likely the exterior surface has the most challenges.  

There are airplane specific windshield polish kits that would be worthwhile looking into.  

What are the choices..?

  • do nothing
  • use a polishing kit
  • replace the windshield
  • practice on a small spot to see if you can get the result you are looking for.
  • practice on a piece of acrylic from Home Depot first.  If it completely ruins a new piece of acrylic, using it on an old piece of acrylic won't make it better... this will give you a feel for how much work Is involved and if you can apply your skill to the more important windshield.

 

Comparing to headlights... different polymer, but same technical issues... UV light (sunlight) and oxidation. 

PP thoughts only, not a mechanic.

Best regards,

-a-

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17 hours ago, MB65E said:

It's the internal structure of the plastic that is compromised. It's done. You could sand/grind/polish thru the windscreen and it would still be hazy. Kinda like a bad pair of head lights. 

If you can live with it great. If not you'll need to replace the glass. 

-Matt

 Bad headlights? I just used "Turtle wax headlight lens restorer" on my headlight. It was $9.99 at autozone. I have no idea if it's legal and if you try it I would only use the lens clarifying compound, but I was shocked at what it did for my headlights. Again I have no idea if it's legal or allowed but I was pleasantly surprised.

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17 hours ago, MB65E said:

It's the internal structure of the plastic that is compromised. It's done. You could sand/grind/polish thru the windscreen and it would still be hazy. Kinda like a bad pair of head lights. 

No, if you ground through the windshield, it would technically be very, very clear :P

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14 minutes ago, MB65E said:

Haha, just saying you can polish all you want on nasty headlights and you'll never get it perfectly clear again. The composition of the plastic has been damaged by the UV. 

-Matt

I know, I was just joking :D It would have been very, very windy too

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  • 2 years later...

Sorry to resurrect this thread, but does anyone have a polish product and procedure to recommend for a windshield in need of tlc?  It’s not terrible yet, but noticeable and annoying.  Couple bigger scratches that might be permanent, but I’d be happy getting the smaller imperfections fixed.

My problem is I’m no pro with doing stuff like this and don’t want to make it worse or waste time.  I’d actually take it to someone if I could find someone close.

Thoughts?

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36 minutes ago, carusoam said:

Yes, the lpaero site has some helpful information, but they basically recommend all the commercial products and then say be careful... which is all probably accurate.

 I guess I’m looking for some personal experience.  Did you use power tools or by hand?  Was it easy to cause more trouble or relatively safe for a beginner?  Any idea where to find someone who does this for a living?  After doing this would you tackle it again or hire someone?

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Just now, Ragsf15e said:

Yes, the lpaero site has some helpful information, but they basically recommend all the commercial products and then say be careful... which is all probably accurate.

 I guess I’m looking for some personal experience.  Did you use power tools or by hand?  Was it easy to cause more trouble or relatively safe for a beginner?  Any idea where to find someone who does this for a living?  After doing this would you tackle it again or hire someone?

Being the plastics guy that I am...

And knowing the original polished surface came from the mold’s surface...  It’s not normal to polish the windshield...

I would only experiment with other pieces of acrylic first...

And have a pretty low expectation that this will work out very well...

Especially if the scratches are of any depth...

It is a two part problem...

1) Getting an optically smooth surface...

and...

2) Not changing the depth very significantly... this will cause a lensing effect...

We used to have @Canopyman around here... he was a great resource for some of these types of questions...

A search through some of his posts may be interesting...

3) a Google search through other canopy suppliers may also be interesting...

4) expect to run into challenges for both manual and powered tools... the window is in a frame...

5) If it is age related surface cracks that are causing sparkles... it may be the only route since replacement is the only other option...

6) Wait to see if anyone has the experience to share...

Best regards,

-a-

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I met a guy a few days ago who was using “Scratch Off” on his Cessna. I didn’t see the before condition but I did see the after and the windshield looked new. He said it was a multi-step process & takes quite a while but worth it for the end results. 
 

http://www.mypilotstore.com/mypilotstore/sep/8416

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1 hour ago, carusoam said:

Being the plastics guy that I am...

And knowing the original polished surface came from the mold’s surface...  It’s not normal to polish the windshield...

I would only experiment with other pieces of acrylic first...

And have a pretty low expectation that this will work out very well...

Especially if the scratches are of any depth...

It is a two part problem...

1) Getting an optically smooth surface...

and...

2) Not changing the depth very significantly... this will cause a lensing effect...

We used to have @Canopyman around here... he was a great resource for some of these types of questions...

A search through some of his posts may be interesting...

3) a Google search through other canopy suppliers may also be interesting...

4) expect to run into challenges for both manual and powered tools... the window is in a frame...

5) If it is age related surface cracks that are causing sparkles... it may be the only route since replacement is the only other option...

6) Wait to see if anyone has the experience to share...

Best regards,

-a-

Thanks for the thoughts and expertise.  I definitely agree that it may be more than I’m willing to tackle.  I definitely don’t want to make anything worse as it’s not terrible now.

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54 minutes ago, Matt_AZ said:

I met a guy a few days ago who was using “Scratch Off” on his Cessna. I didn’t see the before condition but I did see the after and the windshield looked new. He said it was a multi-step process & takes quite a while but worth it for the end results. 
 

http://www.mypilotstore.com/mypilotstore/sep/8416

Thanks.  That seems to be one of the recommended kits.  Id really like to find someone who’s used it. Good to hear that it can work depending on what his windshield looked like before.

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3 hours ago, Ragsf15e said:

Thanks.  That seems to be one of the recommended kits.  Id really like to find someone who’s used it. Good to hear that it can work depending on what his windshield looked like before.

Let us know if you end up using it. I'm fine now, but it's good to know options when the time comes. 

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I have polished the windows on my airplane.. it made a big difference, however I suspect a lot of the haze I was seeing was actually overspray.  For me it made a BIG difference just doing the outside... I used the 3 part NOVUS with some foam heads on a drill.  This makes a ROYAL MESS on the outside of the aircraft.  splatter everywhere!  I STILL have some on my wingwalk that has made it through 2-3 washes.

I also have experience taking deep scratches out of a acrylic aquarium.  It is very very time consuming.  You start with I think 400 grit paper, go only in 1 direction, parallel to the scratch to be removed first.  Then you go down a grit level and go perpendicular to the first pass.  Then down another grit and perpendicular the the last... rinse repeat up to 2000 grit wet.  then a final polish. 

I THINK this could be done on an aircraft window, but I would never do it... You see as you go from 1 grit to another, the area you have to sand grows... so even a small scratch can result in more than a square foot as you change grit 15 + times.  VERY time consuming... I think I spent about 10 hours doing this INSIDE a 250g aquarium.

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One thing to keep in mind...

The acrylic sheet has an aging challenge that is surface related...

So... expect to only have to work the one side.  The side most exposed to the sun...

 

Austin has done a nice job explaining the multiple passes involved from going from rough to fine grit... and how the work area spreads out...

On side windows, or the aquarium... some lensing or ‘fish eyes’ will probably be acceptable...

Some pilots may not even notice small distortions in the windshield either... others may be bothered by it depending on where it is...

 

The cool thing... the kits have been shown to not make things worse...  it kind of adds comfort to experimenting in less visible areas...

Flying towards the sun, where haze and surface imperfections really become visible... may get traded for something that looks good from the outside, but still not as perfect as you like...

Ask @Alan Fox or @M20Doc if they have experience of perfecting windshield surfaces vs replacement... both have seen a lot of different Mooney windows and owners...

Add @orionflt to the conversation, because Brian has always added to Deep-ish technical Mooney conversations.

I’m sure there are other people to add... these are the guys I know a little better than everyone else...

Best regards,

-a-

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We’ve had good luck polishing aircraft windows with 2 different kits from Spruce.  These combined with a small angle drill worked on the inside with the glare shield removed for better access.  My suggestion is no headsets, clipboards, charts etc. on the glareshield to avoid scratches.

https://www.aircraftspruce.ca/catalog/cspages/scratchoff.php

https://www.aircraftspruce.ca/catalog/cspages/windshieldrestor.php

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