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Kolb-List:Windshield plastic crazing

 
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victorbravo(at)sbcglobal.
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PostPosted: Mon Mar 05, 2018 10:28 am    Post subject: Kolb-List:Windshield plastic crazing Reply with quote

John H and Kolb List,

I'm no expert on the polycarbonates or acrylics, but could this crazing be from internal stress over time? Meaning that when you take a flat sheet and bend it into a curve, then fasten it down into that curved position (the shape of the Kolb nose cone), there is a small stress put into the plastic. Over a long period of time, perhaps the stresses eventually cause the internal cracks or difference in transparency?? This is a wild-a$$ guess on my part.

Most "airplane" windshields are thermoformed, heated until the plastic is soft, so perhaps the internal stress is not as much?

If this is not a viable explanation, perhaps the previous suggestion of a bad batch of plastic is the likely answer IMHO.

Most of the manufacturers have a website or some sort of tech help phone number where you can ask a technical question. They may have seen this problem before and have a useful answer.

Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Mon, 3/5/18, John Hauck <jhauck(at)elmore.rr.com> wrote:

Subject: RE: Re: Kolb-List Digest: 6 Msgs - 03/01/18
To: kolb-list(at)matronics.com
Date: Monday, March 5, 2018, 9:11 AM

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#yiv8117676239 Jack H/Kolbers:  Doubt the polishing kit would
correct my problem.  The failure is in the generic
polycarbonate I used last time I replaced windshield and
doors.  I think if I had stuck with more expensive GE
Lexan, I wouldn't be having this problem.  Right now I am scratching my head
to figure out why this polycarbonate failed.  One
possibility is a reaction to the last windshield cover I
made about 4 or 5 years ago.  I found some heavy material,
similar to Naugahyde, at a local fabric shop.  I was tired
of making new covers out of plastic table cloths every
year.  My thought is there was a chemical reaction from the
gassing of the material used to make the material.  Maybe
not.  I don't know.   Darn shame though.  The surface
of the polycarbonate is in great shape.  Thanks for the
suggestion.  john hmkIIITitus, Alabama        From:
owner-kolb-list-server(at)matronics.com
[mailto:owner-kolb-list-server(at)matronics.com] On Behalf
Of Jack Hart
Sent: Monday, March
05, 2018 10:13 AM
To:
kolb-list(at)matronics.com
Subject: RE:
Re: Kolb-List Digest: 6 Msgs -
03/01/18
  John,  I have had good luck with
using the headlight polishing kits that are sold at auto
parts stores.  The kits are not expensive compared to a new
windshield.  Try it on the windshield in a small area and
see if it helps out. Jack B. Hart
FF004 Winchester,
IN  From: "John Hauck" <jhauck(at)elmore.rr.com>
Sent: Sunday, March 4, 2018 1:02 PM
To: kolb-list(at)matronics.com
Subject: RE: Re: Kolb-List
Digest: 6 Msgs - 03/01/18  Chris D/Kolbers: -----my 1992 MKIII, is in need of
a lot of cosmetic TLC, especially the glass.  The
windshield has started crazing which gives it the diamond
glare effect when flying into the sun. 


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John Hauck



Joined: 09 Jan 2006
Posts: 4600
Location: Titus, Alabama (hauck's holler)

PostPosted: Mon Mar 05, 2018 10:52 am    Post subject: Kolb-List:Windshield plastic crazing Reply with quote

Stress may very well be the culprit. Takes a lot of pressure to conform 1/8 polycarbonate to the nose pod and upper windshield frame. Doors are 1/16, but not much pressure to bend them to conform.

Thanks for the suggestion.

john h
mkIII
Titus, Alabama


--


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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama
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