[KenK]

After glassing in my RV-8 windshield, I removed the protective plastic from the plexiglass and found a tremendous amount of optical distortion. It is probably unsafe to fly like it is. The plexi appears to have bands of distortion similar to the patterns of wrinkles in the protective plastic.

I wonder if it is due to solvents in the primer used to finish the fiberglass. Before painting I taped down the edges of the protective plastic so nothing could seep under, then taped down a layer of masking paper. This was done on the outer and inner surfaces. I used the same process on the canopy and it has no distortion. The plexiglass is perfectly clear rather than fogged or dulled as I would expect with solvents. I thoroughly cleaned and waxed the windscreen, so the problem does not seem to be any sort of residue.

Can the windshield be saved with a process of sanding/polishing/buffing? I can just barely feel waves on the outer surface, leading me to think that they are about a few thousanths of thickness change. I can't tell if there are waves on the inside surface. Sanding on this inner concave surface might be
challenging. I would have to start with 320 or 400 sandpaper.

Is this worth trying, or is my best option to rip it out and start over?

 

[Vince Koehn]

Interesting...

This is very interesting. In June of '04 when I peeled the plastic off of my 6A windshied, I had the same problem. It was just as you described, very distorted, and you could almost feel the distortion on the windshield. This of course was after it was installed and getting ready for paint. We had it in several days and tried different things to clear it up and ulitmately tore it out and replaced it with a new one.
Now the punch line... three days later the windshield we took out was laying there on the floor perfectly fine without a trace of distortion whatsoever.
I called several manufactures and discussed this including Aeroplane Plastics and none had ever heard of it before.
What I finally concluded is that there was something I used in the process of installation that caused this. Before you get to aggressive let it set a week or two and see if it clears up...I am not so sure mine would have. Again, the distortion you describe is precisely what I experienced. I had let nothing ever touch the windshield in the way of solvents or any type of cleaner whatsoever. My distortion looked the same as you described as it almost followed the wrinkles in the protective plastic. My canopy did not show a trace of it. All the advice and support I got was useless as everyone said it was simply a film or adhesive from the something and simply needed to be cleaned off. My windshield was perfectly clear and bright and brilliantly clean. The distortion was in the plastic and certainly not on the surface. Now why was it gone three days after taking the windshield out? And why did the new windshield not do it after going through the same installation process using the same epoxy and fiberglass and preped the same way?

 

[rv8ch]

Stress?

... Now why was it gone three days after taking the windshield out? And why did the new windshield not do it after going through the same installation process using the same epoxy and fiberglass and preped the same way?

Just a WAG - is it possible the windshield was under some kind of stress when it was installed, or when the fiberglass dried, it expanded a little and put the windshield under stress? Very strange.

 

[flyeyes]

This is very interesting. In June of '04 when I peeled the plastic off of my 6A windshied, I had the same problem.

While you're waiting for it to clear up, you might want to go over to one of the canard/fiberglass forums and ask. (maybe ez.org for example). If there is some wierd interaction between epoxy and the windscreen these guys would be more likely to know it.

James Freeman

P.S. A tip though, don't make any "compost" or "porta-pottie" airplane remarks until after youv'e gotten answers.

 

[praterdj]

No way to be sure but could the windshield have been defective and it's not a result of anything you did. I'm not to that stage but I'm curious if you ever removed the original protective covering and inspected before you installed. The videos that I have show them just removing enough material to lay in the fiberglass. He never removed the original plastic.

Could be a factory defect.

Just a thought.

 

[jcoloccia]

I have two wild guesses here....both are probably wrong but maybe someone else can weigh in with some similar experience.

First, the SERIOUS long shot: plexi outgasses. Since it was covered in plastic, it may have outgassed unevenly and built up a film unevenly since the plastic covering it isn't perfectly uniform. What did I tell you....a long shot

More reasonable: Plexiglass is hygroscopic (i.e. absorbs water). It's known that plexiglass can warp over time in the presence of water, humidity etc etc etc. Specifically, it will swell on whichever side is contacting water, warping it away from the humidity. If you have some localized pockets of moisture, it could cause local swelling and the kind of optical distortion you're describing. My guess is that the plastic covering unevenly trapped moisture between it and the plexi. Over time it caused some slight warpage. In time, it may go back to normal.

Just some wild guesses. #2 is actually pretty reasonable. Maybe call the manufacturer and see what they think.

 

[664781]

Ken,
Try some Meguiers Swirl Remover. Several canopys and windshields have been saved by polishing them. My canopy looked terrible until I polshed it and now it looks like new. Worth a try!

 

[7pilot]

What to do

So I have my canopy temporarily stored in the top of my hangar - about 12 feet off the ground with a 20 foot ceiling. The plastic is still on it. Should it be removed? I sure don't want to cause myself problems and thought I was doing well to protect it from a buildup of dirt. It gets plenty hot in the hangar, but I didn't think it should get hot enough to distort it.

Stewart

 

[RV8N]

So I have my canopy temporarily stored in the top of my hangar - about 12 feet off the ground with a 20 foot ceiling. The plastic is still on it. Should it be removed? I sure don't want to cause myself problems and thought I was doing well to protect it from a buildup of dirt. It gets plenty hot in the hangar, but I didn't think it should get hot enough to distort it.

Stewart

Stewart, I had my stored for at least 2.5 years just like you; 10 ft in the air and plastic on inside and outside. I had no problems at all. It gets very hot and humid here in the Houston area. If that was problem, I think it would have happened to mine. I'm not telling you what to do, I just don't think that's the problem. Karl

 

[Captain Avgas]

Just some wild guesses. #2 is actually pretty reasonable. Maybe call the manufacturer and see what they think.

John, on the topic of "calling the manufacturer"....did you refer the pitting on your wing spars to Phlogiston Spars for comment. Any feedback.

 

[jcoloccia]

John, on the topic of "calling the manufacturer"....did you refer the pitting on your wing spars to Phlogiston Spars for comment. Any feedback.

I had already called them. Turns out that all they do is assemble the spars. They're then sent out to ElectroChem for anodizing. Vans provides all of the materials.

I'm still pressing Vans for a better answer though personally I think it's caused by contamination when being anodized (this can happen and is not all that uncommon). Vans is aware of the problem, engineering has looked at it and they're satisfied that it's not a structural problem.

Really, though, I'm a bit torqued that they can't give me a better answer other than "it's fine". I believe them and have no reason to think otherwise but (are you listening, Van??) YOU SHOULD REALLY NOT SHIP SPARS WITH PITTS IN THEM! If they're OK, save them for your own fleet, not your paying customers.

It's a shame since it's a huge black eye in what's otherwise been a fine kit.

Sorry for hijacking the thread but he did ask