What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Time for new rear window ...

JerryG150

Well Known Member
I've 77 hours on my Hobbs and I need a new rear window. :( Any suggestions to make this new one last? Maybe someone is manufacturing a better design ... different material or special coating. The standard Lexan window, as we all know is very allergic to fuel ... and no matter how careful I am, accidents do happen. :( Perhaps a 9'x3' rubber tarp laid across the fuselage covering the window would do the trick ... maybe ... :confused:

If there are no better rear windows for the -12, I'll order another standard one from Van's ... then another one and then another one and then another one ... help! :rolleyes:
 
Just curious how many times fuel has been spilled on the lexan to ruin it. I have spilled fuel 1 time and no problems. It would be nice to come up with a solution to this. Good Luck
 
See if you can convince Carl Eldridge to make you one out of plex. I used one of his and it worked great. I also used a tinted one that looks great. Search plexiglass window RV-12.

Doug Dahl
 
While initially testing the fuel system with auto gas and my hand-cranked Flo-Fast system, I had a horrible spill onto the window, despite a piece of rubber mat with a hole in it. NOTHING WHATSOEVER HAPPENED! I thought "Whew!!! Maybe they changed the formulation!" Then on the way to OSHKOSH I had a small spill - first time using a commercial high-flow airport nozzle (still it was auto gas.) The rear window crazed in less than a second! Darn ! Darn ! Darn! The crazing does not extend very far from the edge - about a half inch or so. At OSH I talked to a few plexi and polishing vendors and all said that nothing can be done, but that the cracks won't spread any further. So I've temporarily run a piece of black electrical tape around the edge next to the aluminum to cover the crazing up. We'll see how that initially works, I have some other ideas short of changing the window out. Like they also make some metallized tapes that might not look too bad.

Be really really careful. A mat with a hole in it - well - it is easy for the gas to get under that hole. Another guy was using blue paint tape to attach a manila folder to shield that area. A small fuel amount would not be able to get under the blue tape.
 
Rear window gas detector

You guys miss the point. The rear window on the RV-12 was designed to detect the presence of any gasoline. This way, you never run out of gas, because you can't realistically put any in your airplane to start with. Safety first, folks!

But seriously.....am I to understand that my $65,000+ investment will result in an airplane with a problem like this? Why is no one complaining (loudly) about this debacle?

Unimpressed.
 
Just as another data point with nothing else whatsoever intended, implied, or intoned I have been putting gas in my RV-12 for 2 years and 2 months and have never had a drop get on the window. I started out covering it with a rubber mat that kept blowing off so after about 2 weeks I stopped using it. I am just uber careful. I use a Bykas Fun Fueler to fill it with that only pumps about 3 or 4 GPM powered by air pressure. I can hear when the fuel level just enters the filler neck and I stop, tank full.

http://www.bykas.com/Fun-Fueler-30-gallon-Portable-Gas-Caddy-p/30 gal.htm
 
I did the same thing, will probably have the clear one for sale when I get done. The tint in this area of the country is welcome as well as not being prone to cracks.

See if you can convince Carl Eldridge to make you one out of plex. I used one of his and it worked great. I also used a tinted one that looks great. Search plexiglass window RV-12.

Doug Dahl
 
Plexiglass

After hearing about the Lexan crazing after several dousings with Mo gas I have no regrets going to Plex. I think Carl is actually using a different material now that doesn't crack as easily during drilling etc as Plex and still resists fuel damage. You'll have to contact him.

He may need some urging however...


Jersey
 
Last edited:
I've 77 hours on my Hobbs and I need a new rear window. :(
... then another one and then another one and then another one ... help! :rolleyes:

Jerry,

Do you really need a new window? I have a couple of small craze marks happen after a small fuel spill 2 years ago and guess what -- I just ignore them.

I do notice them when I refuel sometimes and they remind me to be careful.

Tony
 
Very messed up!

Don't ask ... Don't tell ... it's very messed up ... Very! :mad:

Van will issue a new design/material for the rear window in just a couple of days ... Or a couple of weeks .........Or a couple of months .......... Or a couple of years but they will come up with a better design material or location for the filler cap ... Or something ... Just wait and see.

Too bad It won't help me since I am ordering a new "disposable" rear window tomorrow.
 
rear window

Hi I had the same problem so got a new window and covered it with headlight protector film seems to work ok
ashley
 
I use the rubber mat with a hole in it. Never had a problem until I flew to Oshksoh and had to fuel up with 100ll. The problem is I have to pump gas with a stream flow about 1/2" in diameter. It took one back up overflow to which was large enough to go under the hole edge onto the window to learn the flow requirement, but the Lexan was not harmed. Maybe 100ll doesn't affect it? I don't usually have a flow problem with mogas as I pump from my 2 five gal bottles.
I imagine Van's uses the Lexan as it doesn't have to be formed like plexi would so they can keep costs lower. This keeps the 12 price lower, but if that is the reason I suspect we ALL would rather have the plexi and pay a little more for it. Another helpful move would be providing a vent for the tank filling which would elininate most spills.
Dick Seiders
 
What if?

What if I carry an empty 5 gal gas can in my luggage compartment and fill up the 5 gal can from the fuel truck a good distance from my RV-12 and then carefully, using a funnel, transfer fuel to the -12. Then have the truck wait till I pour the gas into the RV and then fill the five gal can again and again till the tank in the -12 is full. If there is any gas left in the can when the tank is full in the -12 I can either dump on the tarmac and risk a fine or smell gas from the 5 gal tank till I need to refuel or offer free gas to anyone available.

Perhaps if I dilute the gas with large amounts of water ...
 
For sale

I still have Van's rear window from my kit. It has never been used and is still covered by protective material. I'd be willing to sell, but not sure of the shipping issues involved with such a large piece. It might be best to live close enough to me in Texas to come and pick it up.
 
I use the rubber mat with a hole in it. Never had a problem until I flew to Oshksoh and had to fuel up with 100ll. The problem is I have to pump gas with a stream flow about 1/2" in diameter. It took one back up overflow to which was large enough to go under the hole edge onto the window to learn the flow requirement, but the Lexan was not harmed. Maybe 100ll doesn't affect it? I don't usually have a flow problem with mogas as I pump from my 2 five gal bottles.
I imagine Van's uses the Lexan as it doesn't have to be formed like plexi would so they can keep costs lower. This keeps the 12 price lower, but if that is the reason I suspect we ALL would rather have the plexi and pay a little more for it. Another helpful move would be providing a vent for the tank filling which would elininate most spills.
Dick Seiders

Being in the plastic forming business, I can tell you'll that Lexan is much more expensive than plexiglas (acrylic), so I'm not too sure why they don't just use acrylic in the first place!!?

I wonder about the automotive 'wrap' stuff? A friend of mine just bought he and his wife matching Ferrari's (they are exec's at a little company called Apple). He had the front clips of both cars 'wrapped' in clear, to protect from rock chips, and you can't even tell it's there. Wondering if it's fuel proof?
 
Some of the cracks are radially out of a screw hole. I had smoothed those holes. So any fuel that gets in there past a surface film can cause it. I am wondering if using silicone seal when putting in the screws might have blocked that path. The cracks are mostly starting from the edge of the lexan, not so much from the surface of the lexan. Protecting that edge would be important. Again I wonder about some sort of sealant application on that. If I was building again, I would put something there just because it would be easy. Maybe even seal the entire edge with some metallic tape that would wrap around it to the screw holes.
 
Stronger?

Stronger with Cracks? The end of a crack is a stress riser. I don't know if this is an issue though. :rolleyes:

Jersey
 
Gary, will you introduce
me to your friends from Apple? I would like to borrow one ( or two) of their cars. Thanks.
Dick Seiders
 
Rear window

I got a replacement from Carl and it is excellent. But, I don't think he is making them any more. I think I would take the old one to Tap Plastic and explain the problem to them. Let them pick a plastic replacement and use the old one as a template to cut you a new window. Then you just match drill the holes using the old window............?
The new material Carl is using is Vivak from Bayer, seems like nice stuff.
 
I wonder if Vans ever tested various rear window materials. We can agree it is structural perhaps, but as was mentioned, how much is the structure weakened by the cracks. Perhaps Vans would direct replacement of the window if it suffered these cracks? Without testing, I would prefer a lesser material to the stronger one filled with cracks.
 
Maybe Carl would be willing to do some more if he had a large enough committment??? If his product does as advertised I would even be willing to pay more for it than he originally was getting.
 
The rear window is structural. Polycarbonate is stronger than acrylic.
Joe Gores

Joe is correct on the strength. As an example, let's take two sheets of material, both .250" thick. One is Plexiglas (acrylic) and one is Polycarbonate. After slightly bending the acrylic (by hand) it's going to shatter like an egg. Bend the polycarb in half, jump up and down on it, and it will NOT break. It is 'cold-formable', meaning it may retain the bend after you've jumped on it, but it simply won't break.

I didn't realize the rear window was considered part of the structural safety in the design. This explains the use of polycarb. Have you seen the teller windows at the bank, or at a gas station in a 'rough' part of town? That's polycarbonate in a much thicker form. Essentially, bullet-resistant material!

And on the Ferrari's, I haven't been lucky enough to obtain driving privledges........................................yet! :)
 
Last edited:
I haven't seen where Van's has said that the rear window is "structural" - with the SPECIFIC APPLICABLE MEANING HERE of that word meaning it cannot be replaced with plexiglas or some other material. Of course the rear window adds some "structural rigidity" but (and we are using the word without engineering precision) it may not be adding structural "strength" - remember, it is held in by rather loose screws in slightly oversize holes. Yes, it will have some strength in both tension and compression but how did that factor into the design? The mother ship knows, we are speculating.
 
I will do a little more speculating and say that the RV-12 will fly just fine with an acrylic rear window. But in the event of an off-airport forced landing where the plane flips onto its back, a polycarbonate rear window will do a much better job of holding the roll bar in place.
Maybe Scott M will chime in and set us straight.
Joe Gores
 
I hope to never have an extremely hard landing but it has happened to pilots much superior than myself. I have seen Cessnas bounce off the runway because of wind currents. With my upper harness connected to the tailcone I would want the highest level of integrity available to me if an event should occur. I'll have to trust someone else for this one even though I do not like the thought of replacing an affected window. Maybe a solution will be found before my window gets mounted.
 
Thanks Tony! I stand corrected! If I was doing mine over I would definitely seal the holes with silicone as I was installing the screws, and cover the bottom edge and one-half inch or so of each side of the window from the edge with metallic tape - all of the window hidden behind the skin. If someone has access to scrap pieces of this lexan, some TESTS would really be good! Would tape like that make a difference? Or silicone in screw holes? Why sometimes 2 spills until crazing? Does it craze more or less If the piece is under a bending load? Does the roughness of the edge make a difference (I.e. different sanding grits.) Is the edge flame polishable? Does it make a difference? (THAT is probably a mod that steps over the bounds though! But it would be interesting to know, that treatment could weaken it - would need to look that up.) What about those films mentioned i.e. typical auto window tinting film? Mogas vs. 100LL? Would make a neat little research project and all that is needed is a bunch of scrap.
 
Thanks Tony! I stand corrected! If I was doing mine over I would definitely seal the holes with silicone as I was installing the screws, and cover the bottom edge and one-half inch or so of each side of the window from the edge with metallic tape - all of the window hidden behind the skin. If someone has access to scrap pieces of this lexan, some TESTS would really be good! Would tape like that make a difference? Or silicone in screw holes? Why sometimes 2 spills until crazing? Does it craze more or less If the piece is under a bending load? Does the roughness of the edge make a difference (I.e. different sanding grits.) Is the edge flame polishable? Does it make a difference? (THAT is probably a mod that steps over the bounds though! But it would be interesting to know, that treatment could weaken it - would need to look that up.) What about those films mentioned i.e. typical auto window tinting film? Mogas vs. 100LL? Would make a neat little research project and all that is needed is a bunch of scrap.

Bill and/or anyone in our group:
I'll gladly supply ALL the acrylic and polycarbonate scrap pieces you could ever want, if someone wants to do some testing. I'd gladly volunteer to do some tests myself, but between work, family, and everything else, I'm doing good just to find the time to work on my -12.

Please, if anyone has the time to devote to testing various 'barriers', etc., let me know. I'll FedEx you'll boxes of scrap for your testing. In the end? I'll bet we will ALL benefit! Just let me know if someone wants to devote the time to try.
 
If one wanted, they could make supports inside to replace the strength lost from changing rear window material, perhaps even strengthening the structure more than the window does..
I hope to never have an extremely hard landing but it has happened to pilots much superior than myself. I have seen Cessnas bounce off the runway because of wind currents. With my upper harness connected to the tailcone I would want the highest level of integrity available to me if an event should occur. I'll have to trust someone else for this one even though I do not like the thought of replacing an affected window. Maybe a solution will be found before my window gets mounted.
 
Well, I really stepped in it by opening my big mouth...

I'll do some testing if you send me a bunch of scrap! I do not intend to text plexiglas, no one has ever said that fuel crazes that and I do not intend to do any structural strength testing or otherwise open that can of worms!

So just pieces of the existing material in the rear window - in that thickness. From only a few minutes thinking about it, I'll need a bunch of pieces about a foot long in one dimension, maybe 6 inches in the other. Yeah, those would be good. Even some larger like 12" x 12". Tiny pieces like 4"x4" might not be much use. I could cut those from bigger ones if I needed them

I may use a vise and a wood jig to slightly bend the pieces as they are tested so they are under a similar load curvature to the installed piece. In some I will drill holes and attach scrap aluminum (simulating the fuselage) and the sames screws/nuts/washers use to attach the existing window. This allows testing of the silicone-filled-holes idea - plus figuring out a way to introduce the silicone effectively and non-messy. (Maybe a hypo needle?)

In fact upon thinking further - to simplify my work it would be really great to get a bunch of 12"x6" pieces. Do you have the saw or setup to make a bunch of those easily from your scrap? I am thinking of building a jig to hold the test pieces and a uniform size would be much easier for that. Don't worry about dressing the edges because I intend to use several grits for that.

]
If someone wants to donate me some window film or tapes for the testing, please send that as well. Otherwise I'll just go by a nearby auto window tint shop and beg for scraps, or get some cheap film from Wal-mart. The metal tape I am thinking about is the type that they use on metal HVAC ducts - peel and stick, a really SOLID stick.

Any other suggestions / ideas are WELCOME! I intend to take lots of pictures of the test setup and the results.

Gary - please email me at billhollifield AT iname DOT com for my address.
 
I will furnish some 3M paint protector film. Very durable stuff.
From what I have heard though it is the cut edges and screw holes that are introducing fuel penetration, allowing the rapid degradation of the Lexan to occur. I would assume a scratch on the main surface would have the same results. It is extremely difficult to mar this film and appears impervious to auto fuel.
 
That video looks applicable. It might be the ideal way to non-messily plug the screw holes. And, if the spilled gas never reaches the lower edge it can't cause crazing - except for surface crazing. BUT!!!

But when I remember the issues about actually installing the window and bending it and sliding it under the edges of the skins to line it up, I think that the example of the video isn't very realistic and it might be very difficult to keep the butyl rubber in place during that installation process. Someone should try this!

I still plan to do the testing and will get some of this to see the effect gasoline has on it as a barrier at the screw holes. But unless this installation is perfect in the area around the gas filler, spilled gas could seep past it to the window's edge. So I am still thinking that a tape covering on the edge might be useful.

Larry - thanks for the film offer, please email me for the address. billhollifield AT iname DOT com
 
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!
 
That is a great idea! Very practical for those students. One thing they will need is pictures of the crazing and event reports like in this thread and others. Can you be the clearinghouse and get the pics and info to them? They will also need some scrap aluminum and the plans instructions for the size of the holes, nuts and screws, etc. to do the simulation. I'll take some pics Saturday of my "event aftermath."
 
Steward Systems EverShield

As one data point, I queried the folks at Stewart Systems regarding their protectant, "Evershield", advertised as "An Easy-To-Apply Glass-Like Finish With Many Incredible Protective Properties For Almost Any Aircraft Surface." I thought that would be a really swell thing if it worked for the crazing problem.

They planned to obtain some scrap from Van's to test for crazing.

They never got back to me, so I asked them last year at Airventure... apparently they didn't have a positive (protective) result--so no magic cure there.


One question I have--are all polycarbonates created equal? Lexan, etc., as opposed to the brand that Van's uses???

Rob
 
I am amazed that a small amount of crazing (on a back window) would cause such dismay. There is no damage to the Lexan, they are not cracks...why not live and let live. To me, its kind of like buying a pick up truck and then getting upset when the the truck bed gets scratched. What counts is how the plane flies. Surely, everyone is not building a show plane? Unless you lock it in the hanger, its going to get dinged and chipped and dirty and all the other things that happen to transport vehicles over time. I'd be amazed if people are as concerned about how of they handle plastic gas cans as they are about spilling gas on their back window.
 
Rob,
Generally speaking, yes. Lexan is simply a well-known trade name, but is still polycarbonate. Kind of like calling a tissue a Kleenex, or a cotton swab a Q-Tip. However, there ARE different grades of polycarbonate. The basic is called a utility grade, then you move up into scratch-resistant, UV-coated, etc. Polycarbonate, despite being as strong as it is, is VERY VERY prone to scratching. It is a soft substrate for sure. As a side-note, one of my products that we manufacture is a windshield for Kawasaki Mule utility vehicles. We sell thousands of these units each year, and you can only imagine the kind of abuse that a windshield on a off-road utility vehicle goes through...trees, mud, road rash while trailering the vehicle to the ranch, etc. We use a utility grade polycarbonate material, with a UV coating. We place special instructions into each unit basically telling the end-user that polycarbonate, while strong as heck, is rather soft. With any polycarbonate, cleaning it must be done with a mild detergent, a microfiber cloth, or a chamois. But one more thing: polycarbonate is highly prone to static electricity. In my world (UTV windshields) the dust and dirt can quickly gather on the windshields due to this static cling. We highly recommend a product called Plexus. A lot of aircraft folks may already know about it, but if not, it is fantastic for polycarbonate (and acrylic, for that matter). The Plexus is a foam spray, and while it does a superb job of cleaning, most importantly it removes the static cling from the polycarbonate. I have no ownership in Plexus, but it works great! It's available online, but more conveniently at most any motorcycle shop. I use it on my Cessna 140 windows and it's great.

Sorry for the long reply.
 
Last edited:
You put hundreds of hours into something, you want it to be really nice. Yes, it is like getting your first parking lot ding on a new car. It is not a huge deal. But if we find out that 50 cents worth of metal tape covering the edge would prevent this kind of stupid problem, wouldn't you put that tape on?
 
You put hundreds of hours into something, you want it to be really nice. Yes, it is like getting your first parking lot ding on a new car. It is not a huge deal. But if we find out that 50 cents worth of metal tape covering the edge would prevent this kind of stupid problem, wouldn't you put that tape on?

Agreed, a million percent! Maybe our little test bed will come up with a cheap solution? If not? Hey, we tried, right?
 
That is a great idea! Very practical for those students. One thing they will need is pictures of the crazing and event reports like in this thread and others. Can you be the clearinghouse and get the pics and info to them? They will also need some scrap aluminum and the plans instructions for the size of the holes, nuts and screws, etc. to do the simulation. I'll take some pics Saturday of my "event aftermath."

Absolutely I can. Bill and any others, send me any photos or data points you want David and his students to check. My email is gary(dot)robertson(at)sbcglobal(dot)net.

I don't have my RV-12 finish kit yet, so if someone can take a quick measurement of the back glass thickness, I'll provide samples to David in that exact thickness. Maybe Van's can chime in on the thickness and the brand they send in the finish kit? Or, it's probably got a protective film on the back glass with the trade name. If I have some of the same brand in stock, I'll provide that to the students.

Thanks.
 
Polycarbonate type

Absolutely I can. Bill and any others, send me any photos or data points you want David and his students to check. My email is gary(dot)robertson(at)sbcglobal(dot)net.

I don't have my RV-12 finish kit yet, so if someone can take a quick measurement of the back glass thickness, I'll provide samples to David in that exact thickness. Maybe Van's can chime in on the thickness and the brand they send in the finish kit? Or, it's probably got a protective film on the back glass with the trade name. If I have some of the same brand in stock, I'll provide that to the students.

Thanks.

I beleive it was Marklon.
 
Thickness

I have an unused rear window from my Van's kit and it is still coated with covering advertising "Marklon". The thickness is not .220, it is more like .150. Maybe others can confirm also. Steve
 
I have yet to receive my finishing kit. But out of curiosity, how does the rear window arrive when shipped? Is it a flat piece cut into an odd-looking shape, and then you 'bend' it into position into the fuselage? That's what I'm guessing, if it's as thin as you guys are saying it is.
 
Back
Top