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11-07-2012, 02:28 PM
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Join Date: Aug 2010
Location: Marshall TX (KASL)
Posts: 1,783
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Why do you think that the ethanol or lack of it is afactor with the window crazing? My initial spill that did no damage was non ethanol auto premium as was the next spill that did do the damage. Is there testing or documentation on this that you can relate?
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11-08-2012, 09:17 AM
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Join Date: Jan 2006
Posts: 905
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Flying two and 1/4 years and no window problems yet. I do place a rubber sheet over the window with a fuel filler cutout which is a drag, but maybe it helps in event of spill/spray of fuel.
I choose not to use the newly proposed solution using fuel sealant on the window. Failure of seal later makes the window replacement on a painted (or unpainted) airplane a major project likely including a removal of tank, and replacement and re finishing of the surrounding skin. Additionally there is the messy installation process of the preceding "fix" as well.
Dick Seiders 120093
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11-08-2012, 12:04 PM
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Join Date: Jan 2005
Location: Arlington, TX (DFW)
Posts: 1,164
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Quote:
Originally Posted by Bill_H
Why do you think that the ethanol or lack of it is afactor with the window crazing? My initial spill that did no damage was non ethanol auto premium as was the next spill that did do the damage. Is there testing or documentation on this that you can relate?
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I've been told by my polymer extruder (they ARE the big boys: they own and produce Lexan, which is the world's largest brand/extruder of polycarbonate, as well as all other polymers), that any standard/typical clear optic polycarbonate (be it Lexan, Makrolon like the factory uses, etc.) will be affected eventually by any type of fuel, be it ethanol auto fuel, non-ethanol auto fuel, 100LL, etc.
It was stated earlier that the curvature of the window has something to do with the possibility of crazing due to chemical contact. I haven't asked my extruder about that, so I can't comment now, but I will inquire!
I'm digging into this, as I've promised for quite some time now. I really don't like the idea of popsicle sticks and ProSeal on my newly installed rear window. There MUST be a better solution, and if anyone can figure it out, it is my polymer extruder. As the world's largest at what they do, they are the experts and I am awaiting their solution. I will pass along their information when I obtain it. The quicker the better!
__________________
Gary Robertson
Arlington, TX
RV-12 Built / Sold / Flying
Currently Flying: Cessna Skyhawk 172
Rebuilding a true barn find J-3 Cub
Last edited by txaviator : 11-08-2012 at 12:07 PM.
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11-08-2012, 03:13 PM
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Join Date: Dec 2005
Location: San Pedro
Posts: 1,013
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Thanks Gary
Thanks for doing the research for us all. Hopefully, there is a 'best' solution as opposed to 'better'. Hope that you find the answer and that Van's will have a serious look at whatever you find.
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11-09-2012, 08:20 AM
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Join Date: Oct 2010
Location: Aguanga, Ca
Posts: 55
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CONSIDER THIS:
Refer to NORTH UP's reply. The surface is protected. It is the exposed cut edges and the holes that are the problem. Seal the edge and holes with Epoxy. "System Three Clear Coat epoxy resin is a very low viscosity (thin), almost colorless epoxy system".
First mask the window. Then fabricate a long narrow container for the epoxy by ripping away a third of the longitudinal surface of a 1" PVC pipe with your table saw and cap the ends. Fill with the epoxy to the dept that will include the holes when placing the edge of the window into the epoxy. Dip the edge of the window into the epoxy.
The question is would the epoxy "crack" when the window is bent and installed? Lets get a length of scrap plexiglass laying around the shop, dip it and see if it cracks. Epoxy is pretty flexible and can take many hours to reach a 100% cure - long enough to install the window.
Follow the instructions for sealing with Proseal but instead use Clear Silicone. Much easier to remove for replacement in the future.
Just stepping back and thinking out of the box - might be my lifetime experience as an Industrial Designer??
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02-12-2013, 09:44 PM
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Join Date: May 2011
Location: Katy, TX
Posts: 39
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Anything New?
Gary,
Any news on the issue from your experts?
Thanks,
Tom
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02-13-2013, 11:14 AM
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Join Date: Oct 2008
Location: Lake Country, B.C. Canada
Posts: 2,416
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caution. silicone.
[quote=RV12Roger;715047]Refer to NORTH UP's reply. The surface is protected. It is the exposed cut edges and the holes that are the problem. Seal the edge and holes with Epoxy. "System Three Clear Coat epoxy resin is a very low viscosity (thin), almost colorless epoxy system".
Follow the instructions for sealing with Proseal but instead use Clear Silicone. Much easier to remove for replacement in the future. QUOTE]
I agree with the advice to seal the holes and edges.
One potential pitfall...if the epoxy is chipped off somewhere during installation, the garden variety silicone has enough acetic acid or something in it that it attacks and guarantees a crack where it hits the edge of stressed lexan. This is from many trials with a windshield in our previous plane. 'Aquarium' silicone or others with a different curing agent may be ok.
you are the experimenter!
another point... as I understand, lexan was created as a hi-impact glazing sheet, and was never meant to be cold formed...it just happens to do it!
We cold wrapped 1/8" lexan for our windshield, and it looked beautiful, although the optics were not perfect looking thru the curved sections.
Within months, if not weeks, the stressed areas developed the classic stress risers, or checking, if you like.
__________________
Perry Y.
RV-9a - SOLD!....
Lake Country, BC
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08-18-2013, 11:39 AM
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Join Date: Nov 2010
Location: Trenton Ga
Posts: 102
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It can't hurt, right? W*R*O*N*G*!
I drilled and trimmed the canopy and rear window with only one tiny crack in canopy. (as fate would have it...it was the very last hole) Instead of "stop drilling" the crack, I melted a stop crack hole.
I attached canopy and rear window several months ago without incidence. Today, the painter was looking over the plane when he said "what caused all these cracks in your rear window?" My heart sank as I rushed to the window and saw a "star" (cracks or crazing) around every screw head attaching the window to the roll bar. However, NONE of the of screws attaching the window to the rear skins had any cracks, crazing or "stars."
What caused every hole over the roll bar to crack and absolutely none of the holes touching the skin to crack? The roll bar has threaded holes. The screws were not tight. They could have been removed with tweezers. The rear of the glass was attached with screws, washers and nuts...also not tight.
Later, my wife helped me removed the window. She asked "why do all these messed up holes feel sticky and have this red tint, while all the good holes feel smooth and look clear. Out of the mouths of babes (beautiful women) the problem was solved....I had put a small amount of Permatex Red Thread Locker on each screw inserted into each threaded hole in the roll bar. Although I used only a minute amount, the Permatex could easily be felt on both the top and bottom edge of the glass. Like the "Blob" (old movie) the stuff had climbed out of the hole and spread out on the glass around the hole...about the size of a dime. I took photos, but can't attach. It asked for a URL....ha. That's as far as I got. I will email if anyone wants to see a black star around 30 or 40 holes. I wonder if PERMATEX will buy me a new window?
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08-29-2013, 06:12 AM
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Join Date: Jul 2008
Location: kansas
Posts: 330
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Gary, do you have a progress report from Tarrant County?
Quote:
Originally Posted by txaviator
Gentlemen,
Sorry for my delayed response. I've been out of town and away from the computer. OK as I catch up on the thread, Bill H volunteered to do some testing, and others have offered some materials in addition to my plastics, so that Bill H can do some testing. But I may have another solution?
I received a message from David Hill (Delta Hotel on the forums). David is an A/P, IA, DME, pilot, and a professor at one of our local colleges. David teaches aviation courses at Tarrant County College, and has asked if he could take on the testing/project as a unique challenge for his students as an extra credit project! I think this offer is fantastic, and I believe we would all benefit from their findings. David is local and I could get him the plastic samples quite easily and quickly. Bill H, if you agree, I'll get the materials to David Hill and his students can begin tests. If you'd still like to do some tests on your own, I'll gladly still send you some plastic test pieces. Just let me know you thoughts on the proposal from Daivd and his college students, and/or if you'd still like to do some tests on your own.
Thanks!
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__________________
Larry Vandegrift
ULPower 260is
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09-09-2013, 07:36 AM
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Join Date: Jan 2005
Location: Martinsville, IN
Posts: 2,326
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After reading all the posts and threads regarding sealing the rear window, I couldn't find any solution posted other than what Van's recommends. I'm getting ready to permanently install my rear window as soon as I paint the interior so I plan to go with Proseal.
I think with Proseal properly installed and a little dab used on the screws as they are installed will ensure that no fuel can reach an untreated edge in the Lexan. And if that happens, then there's never a reason to replace the window so removal is less of an issue.
__________________
Randy Pflanzer
Greenwood, IN
www.pflanzer-aviation.com
Paid through 2043!
Lund fishing Boat, 2017, GONE FISHING
RV-12 - Completed 2014, Sold
427 Shelby Cobra - Completed 2012, Sold
F1 EVO - partially completed, Sold
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RV-7A - Partially completed, Sold
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