I think a couple guys here have installed a false windshield.
Can you describe what you did and how?
Flexible plastic or clear? Does it go all the way to the front edge of the hood? How did you deal with the need for access to lift the hood? How about rain - what did you do for that?
Any other considerations or tips?
I don't know if I have the nerve to build and drive one, but I have to consider it as my car's windshield is not sloped nearly as much as on modern cars, so it's a place where I likely could get some significant improvement. My car probably has separation at hood's front edge as well as the windshield's top edge, and probably some nasty turbulence where hood meets glass.
Currently getting +/- 50 mpg in fall weather. EPA is 31/39 so not too shabby. WAI, fuel cutoff switch, full belly pan, smooth wheel covers.
I thought about making a velcro attaching slope for my windshield since it's angle is a bit off from the angle of the hood. My quick image below shows what I mean. The top half is what it looks like with the hood (has a little curl on the edge), then wipers in that pocket, then the angled windshield. The bottom half of the image shows where I want to put a sheet of plastic, only about 10" tall, that would curve out the angles a bit and I think help a few percent.
try to have a smooth transition between the top of the windshield and the roof! Or the air will probably just seperate at that point as it has a lot of upward momentum!. (I'm not an aerodynamics expert but this seems to make sense). Modern cars often have no sudden change of angle between the top of the windscreen and the roofline.
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I'm not sure about others who have covered their windshields, but I would not feel as safe behind a "second windshield". By the looks of Basjoos' car, it is plastic sheeting, and unless I could make something like that tight enough to not show wrinkles and clean just as well as a windshield, I wouldn't want to try it. My plan was just to cover the lower third or so of the windshield, so that I get some benefit, but not block any of the viewing area. I think where I live in NYS, I would be much more likely to get pulled over if I covered the whole windshield.
I agree with landspeed that the transitions are important. If the bottom is not right against the hood, then you'll just be scooping air into it. If the top doesn't round off, then you'll be adding more turbulence. I'm sure anything would help over a steep windshield.
My plan for all mods is to try something cheap first, then when I find out the benefit decide if it's worth putting money into making a good/permanent version. If I find plastic of some sort to make my attempt at this, I'll post about it.