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Scratches on Lexan

test first!

...just found some tech info that say NOT to use # 3 Novus, other that says #2 AND #3 are too coarse.
some polycarb has a hardened surface that will withstand more abuse.
What does Van's say to do?
What brand and type is it...there are dozens of variations in chemistry.
I find it to be a totally different animal than acrylic.
 
I had an old-timer show me how to use Brasso on a rotary buffing wheel to take out scratches - I was amazed at the results achieved on his Tailwind windshield in very little time.
 
If I remember right, someone posted that the polycarbonate rear window has a special coating to protect it from gasoline and sunlight.
 
Use care around the window

This has been in the forum before several times, but it won't hurt to emphasize again that the Lexan window can be severely damaged by fuel and perhaps other products. My plane was an early build and the original window was not sealed and I waited too long to do so. This was the result of a gas spill, the window virtually shattered in about 2 seconds. I could not believe my eyes. In looking at the damage I find it hard to believe that that could happen just from the exposure of the unprotected edge and holes. But maybe so, you decide. The lesson -- seal them edges and holes and be very careful when refueling or putting anything on this Lexan window.
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To me it looks like the cracking is occurring where the window is stressed due to bending and maybe the bending damages the coating. I donno, not a materials engineer. Just be careful.

Here it is all fixed back up, and nicely sealed. I am very careful, the window is expensive, so is crating and shipping and it takes a fair amount of time to replace it.
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I have similar crazing in my lexan but its on both sides and I know I haven't spilled any fuel on the pilot side so I suspect there is more going on here.
Over stressed?
I think a plexiglass replacement would be nice.
 
IMO, Lexan is known for crazing like this particularly if it has any stress in it- like when formed to shape.

Also a hard coat is required or it scratches really easily. The trouble with the hard coat is then there is no repair for damage without further compromising the hard coating.

Lexan :( Plexi :)
 
Why not plexiglass?

Maybe this is old ground, but why not just replicate the window in plexi? Maybe the window itself is structural? Hope not :confused:
 
Maybe this is old ground, but why not just replicate the window in plexi? Maybe the window itself is structural? Hope not :confused:

Dick, I am pretty sure it is considered structural. Someone was making a premolded plexi unit, but I haven't heard anything of it in several years.
 
Dick, I am pretty sure it is considered structural. Someone was making a premolded plexi unit, but I haven't heard anything of it in several years.

As an EAB builder, I installed one of the draped plexi back windows from an aftermarket supplier. I did it, primarily because I wanted a deeper tinted rear glass. I have had no issues with the fuel damage and crazing that folks have endured with the lexan. The problem is that, as noted above, that supplier is gone, so if I would need a new one, I would be up a creek. So, I have another thought. What if you had a tinted film overlay installed, similar to the car window tinting procedure. Then, all that would be necessary is to seal the mounting holes and edges. My thoughts are that this film may well be fuel impervious. I have that tinted coating on the door glass in my camper, and it has held up for almost 20 years.
Just a thought!

Tom
 
I have similar crazing in my lexan but its on both sides and I know I haven't spilled any fuel on the pilot side so I suspect there is more going on here.
Over stressed?
I think a plexiglass replacement would be nice.

You can't cold form (ie: hand-bend, in this case) acrylic (trade name Plexiglas) to fit the RV-12 rear window application. It will most likely shatter like an egg. That's why the guy that was previously offering acrylic rear windows was drape forming them, with even heat throughout the bends.

Polycarbonate (trade name: Lexan) on the other hand? You can bend it and jump up and down on it, and you'll probably never get it to break. But it is delicate when fuels and other chemicals are spilled on it.

We use tens of thousand of pounds of both materials each year, building windshields that we offer for another industry.
 
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This is what I am working on.


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http://www.joesrv12.com/Builder Log/al_07_01.htm

If anyone has experience bending Plexiglas please let me know.
Can I heat the small side windows and bend them around the aluminum or do I need to make a mold for bending
any help will be appreciated

Thanks

Joe

Joe,
If you heat those small pieces to a pliable state, your heat source needs to be pretty close to the aircraft. The acrylic will start to cool very fast, and you won't have too long to work with it. IF you went this route, you'd need a helper to quickly hand you the 'D' windows while you are inside the fuselage, then you kind of hand form them into position while waiting for them to cool. But even then, you may not have enough time to work the material. I'd build a simple form and drape form them outside the aircraft, let them cool, then proceed.

It should be very easy to measure/map the radius of that area, and build the form. You can obviously map the radius' from the outside and build the form. Cover the form in felt, heat your material, and drape it onto the form while it is still very pliable. Hold flush on all edges until the material cools.
 
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Thanks
Gary
I think that is the best way

If I roll the Fuse on its side can I use Plaster of Paris to make the mold from the inside or is there a better material.

Thanks

Joe





Joe,
If you heat those small pieces to a pliable state, your heat source needs to be pretty close to the aircraft. The acrylic will start to cool very fast, and you won't have too long to work with it. IF you went this route, you'd need a helper to quickly hand you the 'D' windows while you are inside the fuselage, then you kind of hand form them into position while waiting for them to cool. But even then, you may not have enough time to work the material. I'd build a simple form and drape form them outside the aircraft, let them cool, then proceed.

It should be very easy to measure/map the radius of that area, and build the form. You can obviously map the radius' from the outside and build the form. Cover the form in felt, heat your material, and drape it onto the form while it is still very pliable. Hold flush on all edges until the material cools.
 
How about this idea? To make a female form, put some wax paper on the fuselage to protect it, then layup some some wet fiberglass on the wax paper. Some wooden battens can be laid on the wet fiberglass to reinforce it. Cover the battens with another layer of fiberglass. Keep in mind that I have never done this.
 
Joe

I think that would be the best way and I will save the molds to use in the future.

Thanks

Joe D


How about this idea? To make a female form, put some wax paper on the fuselage to protect it, then layup some some wet fiberglass on the wax paper. Some wooden battens can be laid on the wet fiberglass to reinforce it. Cover the battens with another layer of fiberglass. Keep in mind that I have never done this.
 
Or how about covering the outside surface of the aircraft with felt. Then heat the acrylic and lay it onto the felt and hold it until it cools.
 
I am curious? What do you use to evenly heat the plexiglass? It is getting interesting.;)
 
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Joe
This was my first thought but I am not sure that the Plexiglas will stay hot long enough to get from the kitchen oven to the shop, however I think I will try this first.

Thanks





Or how about covering the outside surface of the aircraft with felt. Then heat the acrylic and lay it onto the felt and hold it until it cools.
 
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Scott,

I'm curious as to what the forces are on the window that makes it structural. I assume it's part of a stressed skin analysis, but is it in tension, compression or both?

Rich
 
How about this idea? To make a female form, put some wax paper on the fuselage to protect it, then layup some some wet fiberglass on the wax paper. Some wooden battens can be laid on the wet fiberglass to reinforce it. Cover the battens with another layer of fiberglass. Keep in mind that I have never done this.

BINGO! This is exactly how I would make my forms!
 
Joe
This was my first thought but I am not sure that the Plexiglas will stay hot long enough to get from the kitchen oven to the shop, however I think I will try this first.

Thanks

It typically won't, Joe. Unless you run like a cheetah. This polymer will still feel hot for awhile, but it's got to be right at a perfect temperature to be pliable enough to form to a tight fit. I'd go the fiberglass mold method. Heck, you've got an electric opening canopy, and all sorts of other innovative designs....you ought to be able to whip out a set of molds in seconds! :D
 
Scott,

I'm curious as to what the forces are on the window that makes it structural. I assume it's part of a stressed skin analysis, but is it in tension, compression or both?

Rich

Makes me wonder too. Depending on the answer, Joe may need to rivet in some supports to prevent wrinkling?
 
I am curious? What do you use to evenly heat the plexiglass? It is getting interesting.;)

Dave,

Small parts like this can be placed in the oven. Just be sure the wife is gone while you do it :p

On larger parts, we use heat strips, which are basically round rods that are electrified and heat up lengthwise. These are for area specific bends and curves....they are fairly directional. To form a larger piece as a whole, it takes what is similar to a giant oven and the machine evenly heats the entire piece at one time. But despite how hot it 'feels', you've still got to work rather quickly.
 
Lexan Permanent Fix

I just replace my rear window with 2024 T3 aluminum and painted it black. Can't see out of it anyway. I think it looks awesome. Saved almost 4 pounds.
 
Picture please!

Please take several pix from different angles so we can really see how the plane looks. Also, what thickness?
 
I think he used .024 2024 T3

From the weight savings I think he used .024 2024 T3 the same material as the F01227 Deck skins.

This is what I used to do mine


Joe D

Please take several pix from different angles so we can really see how the plane looks. Also, what thickness?
 
Pics of metal window

One of our local RV12s is equipped with a metal window. Jay Adams is based out of Arlington and asked me to pass along some pictures and message:

"I did the seal advised by Vans. Later a couple of drops of fuel were spilled and I watched as the cracks started on the Lexan. First solution was to cover the cracks with a decal with 'CAUTION NO FUEL SPILL' printed. Later decided on a permanent fix before paint. Got a sheet of thin plastic from the lumber yard and made a pattern with holes punched. Left the Lexan in place decal and all. Cut out the aluminum and drilled and beveled the edge. Installed the aluminum over the Lexan and went to the paint shop. Grady at Glo Custom. I have plans to copy 'joedallas' idea of the Minicab style windows by removing the aluminum sheet and cutting the windows out and re-installing. But that can wait. Meanwhile, I am enjoying no more cracked Lexan. Photos on New Years at 3W5 plus two during the fix are attached."
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Jay
 
New Plexiglass rear window from VANs!

Talking with the Mother Ship today, I learned there is a drape-formed plexiglass window option now available. Kinda expensive though; I think I heard $389 plus crating plus shipping. I think it's also available as a substitution in the finish kit....but it's way too late for me - think I'll wait til mine crazes!
 
Talking with the Mother Ship today, I learned there is a drape-formed plexiglass window option now available. Kinda expensive though; I think I heard $389 plus crating plus shipping. I think it's also available as a substitution in the finish kit....but it's way too late for me - think I'll wait til mine crazes!
Just what is "drape-formed" plexiglass?
 
Just what is "drape-formed" plexiglass?

It is when heat softened acrylic sheet material is draped over the outside of a male mold of the desired finished shape and allowed to cool while on the mold. this can generally only be done when the curve wraps in just one direction (not a compound curve)

In contrast to the fwd canopy of the RV-12 (and other side by side RV canopies) which is forced into a female mold using vacuum / atmospheric pressure.
 
It is when heat softened acrylic sheet material is draped over the outside of a male mold of the desired finished shape and allowed to cool while on the mold. this can generally only be done when the curve wraps in just one direction (not a compound curve)

In contrast to the fwd canopy of the RV-12 (and other side by side RV canopies) which is forced into a female mold using vacuum / atmospheric pressure.
Thank you.
 
:cool:Hope that this is the 'fix' for the 'splash and craze' problems. If so, then will this be the the standard part for the finish kit? Hope so. Best to everyone at Van's.
 
:cool:Hope that this is the 'fix' for the 'splash and craze' problems. If so, then will this be the the standard part for the finish kit? Hope so. Best to everyone at Van's.

My crazing is over about three one-inch long portions along the aft right edge of the rear window. The crazing can be felt with my thumb nail as surface cracks and each extends about 1/4" from the edge. I spread a bead of super glue over one length to see if it arrests it. I also bought some clear UV activated glue, but it hasn't arrived yet. I plan to use it on one of the other areas. I'll post again after I see if it is an effective fix.
 
one possible band-aid solution.....

for you guys who have crazing happening, one thing you might try is to apply a clear laminate over the entire window. This will take some of the stress should the crazing become cracks, and it will provide some degree of splash resistance, (not including the holes or edges though).
One material is 3m 8991 4 mil polyester graffiti laminate. it is thick, hard and clear. Although not certified for outdoor use, I have had it on signs in the sun for at least 5 years with no yellowing or other degradation. Some of the other, thinner clear polyester is easier to apply, and cheaper, with the same basic result.

I'm somewhat pleased that Van's has reacted with an improved product...one might say, the correct product.
good luck!
 
Talking with the Mother Ship today, I learned there is a drape-formed plexiglass window option now available. Kinda expensive though; I think I heard $389 plus crating plus shipping. I think it's also available as a substitution in the finish kit....but it's way too late for me - think I'll wait til mine crazes!

Thanks for the heads up....I was just about ready to install turtle-back and rear window. With all the controversy concerning the existing one....what the heck; $390 is worth no having to worry. Also, decided to upgrade with "new exhaust" to deal with oil cooler heat and wing spar switch upgrade.

I sure hope this completes the "kit".. My wife is starting to give me...looks every time I head for the hangar😬
 
Hey, Ric, as long as she doesn't find the 16 year old runaway living there she'll never question your time in the hangar cave!😜
 
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