Nearly fifty years ago Airstream Philips and Corning met and conspired this window design.
I'm not a Forensic Philips-Corning Scientist. There's certainly greater authority, but I have read nearly every post about them. I don't fit into the debate as I have never held the “replacement” glass in my hand and am unable to make a physical or molecular comparison. What I understand is that the thickness is different, the temper is different, and the logo/label/stamp/bug is different. I would guess that what also differs are the ratios of glass formers, flint, sand, quartz, Potash, fluxes, coefficient of expansion, heat ramps, annealing temperatures....
“Replacement” glass is not Corning Glass.
I have thoroughly rebuilt all my Corning windows. They operate and fit as new.
If you've read all the posts about Philips/Corning, you've read the argument between the two prominent suppliers as to which is the superior “replacement”. Safe to say, that they are both inferior to original Corning.
I can't imagine that AS went to Corning and asked for the finest glass that money can buy. It was more likely “Furnish the cheapest glass that you're willing to put your name on.” Corning of course, would have replied, “Our way or No way.” So, there must be some Corning science employed.
I'm a bit fascinated by the science, design and manufacturing expectation that the glass has to bend
just enough to evenly
compress the seal. That's not an easy task. I'll bet that getting the glass to bend and seal evenly upon closure with the sill winders isn't something considered with the "replacement" glass, otherwise why does it seal better upside-down?? Yup, folks get better sealing that way.
type 1... Very difficult to replace silicone bedded glass, leaked at top horizontal edges.
type 2.. Introduced the clamp-bar and tape bed, leaked at top edges(clamp-bar ends). Easier to replace glass.
type 3... Improved clamp-bar end design?, maybe leaks less, stainless steel glass edging to enable deeper skull gouges and enhance outward appearance by hiding black window seals. The edging may protect glass and aid in prevention of breakage. Seal is a little better hidden from UV by stainless edge. Not real sure if there is much difference other than stainless edge.
The desperately needed type 4, 5... were never conceived.
All types leak through the long horizontal top hinge in wind-blown rain.
If you leave them open in a wind-storm, they'll blow away.
The foam tape deteriorates and windows fall out if not latched closed. Always close windows for travel.
There is very little concurrence on how to restore these windows. There are pages and pages of posts with varying opinions. Everyone is trying to help, but without the knowledge and material of Corning scientists....
The ten pound 3M outdoor tape is grey foam with red release film. I think it is important that the glass centers in the channel exactly as corning intended. The rack and pinion winder mechanism appears to stop at a specific point of closure and if the glass is “cocked” in the head-rail channel, it'll be a bit too open or closed more than intended by Corning. This could matter a bunch.
There is no agreement as to which type gasket/seal to use along the two vertical jams and sill. The rectangular solid foam v the hollow “D”tops the list, but other gasket types have been used with unreported results.
No one has surfaced to say, “I was there in 1966
and remember that Airstream window gaskets looked like …??” Where's a witness?? The old, apparently original gaskets that I removed from my 1968
GT looked like the square foam style replacement available today, so that's what I used. Whether it is formulated to have the same compressive resistance as the original gasket, I don't know. I also don't know if it is 1968
If it is what Corning/Philips specified in the sixties, I'll trust it. Corning isn't going to put their name on something that doesn't work. Corning makes the windows for the US Space Shuttles and Space Stations. Here on Earth, Corelle plates and Pyrex. No Contest.
When the window is being pulled shut by the silly little Philips sill winders, somewhere along the body contour, the vertical jamb gasket becomes the fulcrum for the flex of the glass. As the glass bends, the fulcrum moves. The amount of loft and resistance provided by the gasket determines how deeply the glass seats into the gasket, and how well the glass curve matches the body curve. Closed, my all original corning glass windows have no more than .030” deviation top to bottom, a visually undetectable deviation and don't leak. I mop the gaskets with Aerospace 303 hoping to prolong the gasket's resilient quality.
Your large front facing window could be bullet resistant clear polymethyl methacrylate, polycarbonate, in order to prevent it from shattering by rocks and road debris, and it would eliminate the need for a front “rock guard”. I enjoy the see strait through out the back trailer window from my TV rear view mirror. I can always identify the vehicle following me, and observe its behavior...
I was pleased to find that in the $20 VTS reproduction, every piece of the mechanism is an exact replica of the original Philips. The nob of the winder has a slightly different profile than 1968, so I used my old nobs. The stainless steel cover has a VTS logo, so I used my originals, which better matched the patina and logo of the original. Last year, I saw original, used, winder/closure mechanisms battled for on eBay, selling for $75. $20 to get all new guts is a great deal... And they work like new.
There are more than a few folks who have installed their replacement windows upside down because they seal better. Some say that they cut strips of tire inner-tube to make shims to compensate for poor fit. This would cause pause to me.
The replacement glass which is said to “fit the window frame perfectly” is 1/8” thick, and if it is indeed fitting the window frame perfectly, it's my contention that it cannot seal as designed for the flexibility and uniform compression of the gasket, and maybe that's why they seal better upside-down. Maybe that's why the loftier hollow “D” gasket is a better seal, as it is more compensating for poor fitting replacement glass. The original Corning glass is closer to 1/10”, and there may be a reason for that thickness with respect to the sealing design...
If I were faced with your concerns, and if you're as fussy as I, I suggest that you make poly windows and wait for original Corning windows to surface from a donor trailer. I would not waste $$ on “replacement glass”.
Kind of a long-winded thread bump. Now maybe we'll find someone has had miraculous success with “replacement” glass, and explain their satisfaction???