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rear window dimensions

Rear Window Rough Overall Dimensions - Material

My uninstalled 2013 flat sheet of Bayer Makrolon Abrasion Resistant polycarbonate Part F-1277-A is a tad under 67-inches wide and 21-5/16-inches deep and 0.135-inches thick including protective covering both faces. It is pre-cut with facets to form approximate curves and has many, many pilot holes at the edges.

Looks like material was changed to plexiglass/acrylic Part F-1277-B in my updated working plan set.

Anybody know why the material change?

I plan to install it close to the end to maintain easier access.
 
Looks like material was changed to plexiglass/acrylic Part F-1277-B in my updated working plan set.

Anybody know why the material change?

The change was due to the cracks that developed from the screw holes near the fuel filler if gas was spilled on the window. Only takes one time and you have cracks. There was an independent effort to make heat formed windows, I ended up with the window buck from that effort years ago. There was some debate with Van's about polycarbonate vs acrylic strength and structural use of the window. There were some good threads on material properties at the time, OBE when Van's eventually came around on the molded acrylic window.

John Salak
RV-12 N896HS
 
Picture of my Lexan window in 2014 after I spilled fuel on it:
 

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Rear Window - Lexan vs. Plexiglass

Thanks for the history on the RV-12 rear window. The newer plexiglass/acrylic part is $685 plus possible crating and shipping. I will probably install my Lexan/polycarbonate part and hope for the best.

I remember talk about fuel and Lexan being a bad mix even though the polycarbonate specs say it is gasoline-resistant for 24 hours. I added the fuel tank vent/overflow line and will probably use a pump (Harbor Freight has a great little 2 D-Cell fuel transfer pump for $10) rather than trying to pour through a spout from a jug.

If the consensus is the cracking is an unavoidable problem with Lexan just from vapor, I would prefer to just do a plexiglass part. For me, it is hard enough just installing stuff once.
 
I inherited a new Lexan rear window from a friend who substituted plexiglass during initial build. I used the new Lexan to replace the original crazed Lexan that suffered a fuel splash. New Lexan is holding up beautifully. I now fuel with a FastFlo hand-operated pump and have not splashed fuel on the new window. I little care goes a long way….
 
Lexan

Before installing my Lexan rear window, I polished the edge in the vicinity of the fuel filler. I also used proseal as a sealer in the same area. Fuel has come in contact with the window on 3-4 occasions, no cracks or crazing yet. It will eventually fail and will be a pain remove with the proseal, but I'm at 8 years now.....fingers crossed 🤞.
 
thanks for the info, much appreciated!

My uninstalled 2013 flat sheet of Bayer Makrolon Abrasion Resistant polycarbonate Part F-1277-A is a tad under 67-inches wide and 21-5/16-inches deep and 0.135-inches thick including protective covering both faces. It is pre-cut with facets to form approximate curves and has many, many pilot holes at the edges.

Looks like material was changed to plexiglass/acrylic Part F-1277-B in my updated working plan set.

Anybody know why the material change?

I plan to install it close to the end to maintain easier access.
 
Before installing my Lexan rear window, I polished the edge in the vicinity of the fuel filler. I also used proseal as a sealer in the same area. Fuel has come in contact with the window on 3-4 occasions, no cracks or crazing yet. It will eventually fail and will be a pain remove with the proseal, but I'm at 8 years now.....fingers crossed 🤞.

That is very encouraging! I will put the part I have in with great care and hope for the best! Thanks!
 
Want to buy your Lexan! Or get a tracing...

I may replace my Lexan rear window (the original, flat RV12 rear window that came with pre-drilled holes.) I would love to buy an unused one from someone that went with plexiglas instead. OR IF POSSIBLE, I can source the lexan sheet but would love to get an accurate tracing of the Van's flat lexan piece with all holes marked.

I have no idea if I remove my lexan rear window if it can be pressed flat again to get those hole locations. Please email me at billrhollifield AT gmail DOT COM

By the way, how do you cut Lexan? Grinding disk?

Back in the day we theorized about polishing the cut edge (the crazing seemed to propagate from that edge. (Although pics like Tony's indicate other possibilities.) Then covering that cut edge with a strip of metal HVAC tape and also putting silicone sealant inside the holes when the screws are put in.

I have minor crazing on both sides of the back window near the edges, fuel
has never been near the pilot side. Strange. I think even the vapor can start the crazing.
 
Tracing Lexan Window

I have the flat Lexan part not yet installed with protective facings and might have a roll of vellum (cotton fiber) or Mylar drafting media under my stairs. I am working on multiple things now but I think tracing it is a good idea for my own future replacement. May need a Rapidograph pen for accuracy. I also have to find a big smooth flat surface to work on. I can put a reference scale on it in case of swell or shrinkage and get a full size photocopy (scale controlled) at at "blueprint" shop to mail in a tube. I will try to do it but it may take several weeks. Will post or PM once it is done. Not promising perfection.
 
Thanks Stuart - I think I have a tracing from a new old stock flat sheet coming from another source. Maybe an entire window. I wish I had done a tracing "for the future."
 
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