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Old 09-09-2004, 08:08 AM   #43
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Bent Lexan Test #2

Well, we've done the second "Bent Lexan Window Test" ... with poor results but some knowledge gained.

Technique: Heated Blodgett commercial oven to 350 degrees F. The form (measuring 30" x 22") would not quite fit, so we decided to heat the Lexan on a sheet of plywood (flat) and then put it on the form, outside the oven.

Result: This was a mistake. 350 degrees is a fine temperature for "drape molding" the Lexan, but if you intend to transfer it from one piece of wood to another, the Lexan will be too soft.

See below for the awful result.

A subsidiary part of this test was to see if we could leave the protective film on the Lexan during baking and forming. While it is possible, we found that the lettering on the film will offset (imprint) on the Lexan. After peeling the film off, we were still able to read the words on the Lexan!

The film may also have negative effects on the Lexan adapting to the form shape perfectly. I recommend removing it before baking.

Next test: (a) Heat the Lexan to a lower temperature (perhaps 320 F) and transfer to the form, then continue to raise its temperature with a blowtorch or heat gun until it forms -- OR -- (b) find a bigger oven that can accomodate the entire form.

Note that using a blowtorch will be as much art as science, and good even results may be difficult to attain.
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Old 09-09-2004, 08:34 PM   #44
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"Let's look Death in the face and say, 'Whatever man.'"
~ Hurley

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Old 09-09-2004, 09:14 PM   #45
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I've never done anything like that before, but I applaud your effort.

Now, a suggestion.

Since an oven is basically a stell box that is insulated is it not possible for you to build a steel box in the size you need with a door that has the same type gasket on it as an oven and use an old heating element from an electric oven for this. You would have to have a thermometer on it, but since the heating is so small in time I would think that it would be fairly easy to control the heat inside.

Actually I would only build this type thing if I were going to make these up to sell because the investment may not be worth it.

Like I said I've never done it, and I hope you have better luck with the next few pieces.
Just adding my 2Ę worth

John G
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Old 12-08-2004, 11:15 PM   #46
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Cold forming of Lexan (with a bit of heat)

Just replaced the front side window in my 69 tradewind. It is slightly odd shaped and has a curve to it. After cutting the new Lexan to size I decided to try and put a pre-bend in it to help match the curved aluminum frame. The lexan pane I was replacing was installed flat and so was distorted and was allowing water to enter the shell.

I placed the bottom edge of the lexan on the top of my workbench (just rough plywood) and folded the lexan over along the line of the bend I desired. The first couple of tries seemed to impart a slight curve to the lexan. So I got a little bit more energenic with the bending (was laying on it an bouncing). This bent the lexan even more but still not to my satisfaction. I pulled off the protective plastic coating, got out my propane torch and heated the line of bend (wide swath). The flame could just touch the lexan if you keep it moving an not affect the surface. I tried a little heat at first and then quickly bend the lexan, look for the desired affect and heat a bit and bend allot. Took about 15 min. and I had a window that was bent close enough to slide easly into the curved frame.

Lexan is by nature tough stuff. I don't think that it can be snapped under normal temperatures (65 degrees F). But please keep the possibility in mind as you bend. Plexiglas on the other hand will break and send shards flying.
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Old 12-09-2004, 09:53 AM   #47
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Tempered glass can fail, when the tempered surface has been penetrated.

The 66,67 and 68 windows are famous for this.

The thickness of the temper on those windows is very small. Therefore a simple grain of sand can penetrate the temper.

When that happens, it may not shatter, at that time. However, as I am sure many of you have experienced, when enough temperature changes have taken place, from the sun to the cool evenings, the glass may shatter.

We originally came out with Acrylite and then upgraded it to Acrylite with an abrashion resistant coating on each side.

Acrylite, in time, will conform to the curvature of the window frame simply by being exposed to the sun. However, Acrylite is not a very tough material.

We then did some research and decided to discontinue the Acrylite and switch to Lexan, a polycarbonate, but with the "abrashion resistant" coating on both sides.

Seldom can Lexan with the AR-2 coating be found at local stores, as most people are not aware that it exists. Of course this special coating, very similiar to that that is used on plastic eyeglass lenses, adds considerably to the cost.

The problem with Lexan, is that it is very tough, and will not conform to the needed curvature. We therefore came out with the stainless steel moldings for the two sides and bottom of the window.

Airstream learned that the original windows on the 68 models, did not break as often. Theory has it that the stainless steel moldings added enough additional rigidity to the window to help compensate for the flopping of the windows while they were open from simply gusts of wind.

Bottom line is that the best replacement for the 66-67 and 68 windows is Lexan, with the moldings added. The moldings are shaped to the contour of the trailer and therefore will seal against the gasket as it should.

However, some owners don't want to have one or two windows with the moldings. On the other hand many owners have updated the looks of their trailer, and at the same time added to the rigidity of the glass, by adding the moldings to every window.

It really becomes an upgrade advantage and does considerably help against breakage of the glass.

But to some, it doesn't look original, but to many others it makes a 66 and 67 trailer look like a 68.

That certainly is very much on the plus side, and certainly adds beauty as well as increases the value of the trailer.

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Old 12-09-2004, 10:44 AM   #48
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Thanks for that, Andy. I am about to replace my front window in my '67 and wasn't sure if I should get the molding or not, if it was necessary. I don't care what year it makes my trailer look like; I want it to not leak!

"Let's look Death in the face and say, 'Whatever man.'"
~ Hurley

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