Rectifying warped windscreens.

[PatW]

I'm building a car model that has the windows seperated in single units fitted from the outside of the bodyshell. The rear and sides fit perfectly, but the front screen is warped/distorted on the sprue and when offered up to the body touches along the top but is a distance away on the bottom right hand corner.

I regularly make roll chages so know how to warm plastic rod/sprue to the right temperature to bend to shape and not to burn or melt through.

But how do you straighten out, bend reasonably thick clear 'glass' plastic windscreens to fit the aperture in the shell please?

[Snake45]

I doubt you're going to be able to satisfactorily "unwarp" a windshield. You should probably be thinking along the lines of replacing it with sheet clear, perhaps formed by "heat and smash" if necessary using the corrected kit part as a mold.

If the kit's in production and you think the problem is limited to just your example, you could ask the manufacturer for a replacement.

[PatW]

Thanks for your input Richard. I have tried with  thin clear plastic, having used the original as a template, but because the 'new' piece is 'springy' it's difficult to set it into the slotted groove below the edge of the window surround which is very narrow even to tape it down.

As it is a Revell Germany kit, I have contacted them for a replacement only today and hope for an answer to my email soon. 

Edited November 11, 2016 by PatW

[Harry P.]

Bring a bowl of water to a boil in the microwave. Remove the bowl and drop the "glass" in it. Wait a minute or two, then take out the glass and working quickly, twist it into the shape it should be, using the body as a guide. Run the glass under cold water to set it into shape permanently.

Even if you mess up, you have nothing to lose, as the glass is already unusable.

[PatW]

Thanks Harry. It's just as I thought.

Since putting this on here I found a youtube video where the guy was straightening out a warped shell,with boiling water,  so I thought I might try that.

Thanks again. 

[Snake45]

Boiling water is MUCH too hot, and after "a minute or two" in boiling water your part is likely to look like a wadded up cigarette package cellophane wrapper.

Heat also shrinks styrene, something you don't hear too much about.

Please don't ask me how I know these things. The story is much, much too painful.

[PatW]

Thanks again Richard, for your info, I suppose it's a suck it and see job!  Gradually heating the water and trying the screen at different temperatures and tweaking it as I go along.

Edited November 12, 2016 by PatW

[Snake45]

I still think your best bet (assuming Revell doesn't come through for you) might be to correct the flawed windshield you have using putty, filler, add-on pieces, whatever, and then use it as a mold to "heat and smash" a piece of clear plastic over it. Model airplane guys have been doing this for canopies for decades.

If you go trying to correct your windshield with heat, there's a good chance that you'll damage/distort it to the point that it can't even be used as a mold.

What kit is this for? Maybe one of us has a spare part, or can suggest a viable replacement.

[Harry P.]

Boiling water is MUCH too hot, and after "a minute or two" in boiling water your part is likely to look like a wadded up cigarette package cellophane wrapper.

Heat also shrinks styrene, something you don't hear too much about.

Please don't ask me how I know these things. The story is much, much too painful.

What I said was you bring the water to a boil in the microwave, then remove the bowl. The boiling instantly stops. I didn't say let the part sit in boiling water for a minute or two.

[Snake45]

What I said was you bring the water to a boil in the microwave, then remove the bowl. The boiling instantly stops. I didn't say let the part sit in boiling water for a minute or two.

You said drop it in water that had just been boiling for a minute or two. That's still too hot and too long.

[Ace-Garageguy]

And this is how you make one from thin stock that looks much more realistic anyway (Bill Geary aka MrObsessive adds little strips of plastic to the inside of the windshield frame for the "glass" to snap into too). Both these techniques work very well.

Edited November 12, 2016 by Ace-Garageguy

[Harry P.]

You said drop it in water that had just been boiling for a minute or two. That's still too hot and too long.

You're right! My advice is wrong, the water is too hot.

Ignore my previous "help."

[MrObsessive]

And this is how you make one from thin stock that looks much more realistic anyway (Bill Geary aka MrObsessive adds little strips of plastic to the inside of the windshield frame for the "glass" to snap into too). Both these techniques work very well.

To expand upon what Bill said (thanks Bill!), you can go here to check out how I make windshields using clear stencil sheet. If you start with pic #80 in the album, that's where I get into using plastic strip in holding the glass in place after you make your template.

It's a bit time consuming, but IMO this yields better results than kit glass as the stencil sheet "reads" a lot like actual glass, and doesn't have the optical distortions that many kits have with their clear parts. You didn't mention which model this is for as this technique works best with flatter glass, but I have done this with models that have wraparound windshields.

Edited November 12, 2016 by MrObsessive