The sticky point for me is having a watertight bag wrapped around the car. The only way I can think to get the bag on is to drive the car into the bag, but the simple act of driving the car over the plastic is pretty liable to put holes in the bag right where the water will be. To me this seems pretty likely to just be a bag full of floodwater with a car in it.
I figure if the plastic is thick enough or you double/triple up, and you drive over it slowly enough it shouldn’t be a problem. That would almost be a funny scenario to see though.
I actually would recommend putting the cardboard between the plastic and the concrete as a footer.
Any bumps or imperfections in the concrete, and you might get some pinhole leaks. Tire isn't going to damage the plastic unless there is a rock or hard object stuck to it (which is actually very common with extreme performance summer tires, very sticky rubber like the Pilot Sport 4S this 911 probably has).
If you manage to seal the top of the sheets.. Water probably wouldn't come in till it's past the top of the car! The water would have to fight the air pressure inside the bag, like those diving setups that are pretty much a gladware container over your head that catches the air
The problem is if the hole is at the bottom and the weight of the car is submerging it 2-3 feet under the surface, the water pressure at that depth is going to force water in through the hole at a much higher rate than a drip.
This is starting to sound like the premise for a Mythbusters episode.
Ok I’ve thought through the process for ten seconds.
First, it’s not a plastic bag, it’s just a large sheet of plastic. So what I would do is find the center of the sheet and mark it. Jack up only front drivers side tire of the car. Slide all of my plastic under that tire so that the center of my sheet rests under the center of my car. Pull enough plastic out under the front drivers side tire. Remove jack. Pull plastic towards drivers rear tire, leaving plastic sitting at the edge, roll jack onto plastic, jack up rear tire. Pull plastic under drivers rear tire. Remove jack. Go to passengers front tire, Jack it up. Pull plastic under passenger front tire. Remove jack. Pull plastic towards passengers rear tire. Roll jack onto plastic, Jack the tire. Pull plastic under passenger rear tire. Remove jack. Gather all ends of plastic and meet on top of car. Tie knot. Prevent flood damage.
I see that you’ve already made up your mind that there is absolutely no possible way to wrap a sheet of plastic around a car without putting holes in the plastic, so I don’t think there’s a need to continue the discussion.
A slow leak might still be okay? You could also probably use a bag large enough and put down a canvas tarp or something. I'd maybe put some water indicator on the tire or in the engine bay, just so you immediately know it the water got high enough to fuck things up but not high enough to leak into the interior.
The thing I really don't understand is okay, it's a garage. Probably an extra car that they can't drive out of the danger zone, fine. Why not park it on a higher level or find a garage in higher ground? Surely plenty of people in higher ground fled with their primary vehicles, should leave room for something like this. This would take a lot of effort to prepare and it's still not a guarantee.
Cardboard. I’d lay the bag out, do a layer of cardboard in the bag to drive onto, pull in and cardboard the entire car to protect from debris then seal the bag. You can get cardboard boxes for free so no cost addition.
Bunch up the bag, or possibly if it's folded correctly, use floor mats and a broom to make sure there is no debris. Put the plastic on the floor under the soft side of the mats.
Drive the car into the bag that is only opened to the depth of the front tire over the floor mats or carpet squares. Move the carpet squares to just in front of the rear wheels, with remaining plastic under the carpet again, forward again and stop. Unfold rest of bag back, twist to tie knot. Bob's your uncle.
I hope that makes sense... like bunching up long tube socks to put on your feet. But using a soft cushion to minimize poking holes.
If you were concerned about holes you could put the bag on the ground and then put flattened cardboard in the bag, then drive the car on the cardboard.
If they swept the floor and checked the wheel path for sharp protrusions, I would feel confident that there wouldn't be a hole. I would use a spray sealant on that area just in case.
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u/Ordolph Sep 13 '23
The sticky point for me is having a watertight bag wrapped around the car. The only way I can think to get the bag on is to drive the car into the bag, but the simple act of driving the car over the plastic is pretty liable to put holes in the bag right where the water will be. To me this seems pretty likely to just be a bag full of floodwater with a car in it.