Can I use a blue plastic tarp to float my vehicle across water?

Ok to address your question: Can I use a plastic blue tarp to float my vehicle over water?

Yes

Limits and Considerations:

WILL YOU FLOAT?

First off I will describe the physics of the floating car. The force of buoyancy acting on your car must be greater than the force of gravity pulling it down. The equation for buoyancy is this . Where Fb is the force in the upwards direction, Vs is the volume submerged in meters cubed and rhoL is the density of the liquid/gas the object is in. g is the gravitational constant (9.8 m/s^2). This is my source.

So in order for this to work you'll need to know the mass of your vehicle plus tarp entity to calculate the force due to gravity acting on this entity. Next, determine how much volume your entity will take up in the water (so consider taking 75% of the total volume of your entity as you'll need part of the car above water). Also know the density of the fluid you are traversing. Only after knowing this will you be certain your car will or will not float.

Should your tarp break and water starts engulfing the space that was filled with air, recognize that the volume of your entity will decrease (thus decreasing the buoyant force). So make sure your tarp doesn't let water in!

If someone that's actually good at physics could review this answer that would be tremendous.

Traversing bodies of water can be DANGEROUS!

Bodies of water can contain foreign, sharp objects that could jeopardize the ability of your car to float. For example, what if a stick tears a hole in your tarp? If we're assuming your traversing a pool, then the STRENGTH of your tarp shouldn't worry you. But if you do think the strength of your tarp is a consideration, look up the numbers for your particular tarp.

posted over 8 years ago

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Dzhao‭

21 reputation 3 2 4 0

In addition to previous answers:

Consider the center of mass. The "modern" car usually are quite front heavy (quite often the engine, gearbox, clutch etc. are all in the front) in contrary to the depicted jeeps. That means a "modern" car will by no means float as level as the depicted one, even if you have enough lift.

posted over 8 years ago

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flawr‭

71 reputation 1 19 7 0

The whole thing comes down to weight, if your setup can displace more than its weight then it will float, those jeeps were made to be very light. You could be in the situation where your "wrapped car" could float but its so deep in the water you wont be able to move it anywhere (or you would need an huge canvas and a mean to hold it in deep water as much as the soldier standing in the river is doing in the video). As for the durability of those blue tarps you can never tell, i have polytarps that are extremely sturdy and some that will rip apart very easily. I wouldn't trust them for these kind of things. I would probably end using a double or triple layer of polytarps.

But, that said, if you have a car from a scrapyard, a body of water to try and a mean to pull the car out if it sinks it can be a fun idea to try. (Often boatramps have a decently steep entry, so chances are that something like that will start floating one end of the completely wrapped car while the other end is still resting at the edge of the water on the ramp. That could give you a safety margin to still be able to drive out of the water in case things don't go the way you want. If it works that way then you can be more tranquil when you will try driving on the tarp further in the water like in the video)

If you calculate the volume of a box that has the dimensions of the car, then see how much water it displaces and compare that with the curb weight of the car you can have a very very rough idea on how high it will float. Then, obviously, you have to take in account that the cube doesn't have the tires sticking out etc but as I said its just to give yourself an idea. (a rough calculation using dimension and weight of an accent hatchback gives an immersion of about 8inch for the cube example) Or you could go high tech and use Delftship and a model built on the profile of the car you want to use to see its displacement ;)

posted over 8 years ago

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Erik vanDoren‭

211 reputation 0 41 21 0

Based solely on the video you provided the link to, and my experience with blue thick tarp, I have a few things to address. I don't know what kind of tarpaulin you have, how heavy your vehicle is, and how deep is the river/pond/lake you're trying to cross through. Despite that, there are a few things you should keep in mind.

• You should make sure that your vehicle's density is always equals to or less than: 1 g/cm3 so if you have an object that weighs 1000g it needs to have at least a volume of 1000cm3 to "Float" (1 to 1 means that the object will not stick out because it'll be as dense as water)

density = mass / volume

Example:

Let's say you have a Hybrid Prius:

Weight: 1325 kg or 2921 lb or 1325000 g

Volume: 12.68 M³ or 774317 inches³ or 12688798 cm³

Thus: 1325000g / 12688798cm³ ~= 0.10g/cm³

Will it float?: Yes, and 90% to 80% of your car will stick out of the water

So grab your measuring tape, get your vehicle's sizes, and get ready for some simple math

Calculator: http://www.calculator.net/volume-calculator.html it helps you with the conversion

Buoyancy: http://scienceprimer.com/buoyancy

But I still think you shouldn't risk sinking thousands of dollars because you didn't want to spend some hundreds of dollars on a canvas tarp, but it's just my two cents.

posted over 8 years ago

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Kyle‭

26 reputation 4 1 4 0

If your tarp is heavy duty enough, I'd expect it to work. Most blue plastic tarps are fairly thin and weak, so while it might work, it would be risky.

The difficulty is that you will be abrading the tarp by driving onto it, probably subjecting it to abrasion from rubbing against the jeep's body, and risking the tarp catching on underwater debris. The thinner your tarp, the higher your risk.

Even a pinprick leak could be a problem, depending on how long you are in the water. A flimsy tarp of any material will develop leaks or rip relatively easily, maybe even while loading for your first test. A sturdy one would probably hold up to a few trips, although I've got no idea how many. The toughest waterproof fabrics are used for whitewater rafting vessels, which gives an idea of how sturdy a tarp (not polypropylene) can be.

Make sure before you start that you don't have any leaks in the tarp. I've never had to do this, but a possible setup that comes to mind is hanging the tarp in a cup shape and dumping in 10 gallons of water or more, then swishing it all over the tarp surface to make sure it doesn't leak. At the minimum, I'd spray one side with a hose, but that has a few problems: 1) it's hard to be sure no spray is reaching the far side, which makes leaks harder to spot, and 2) if the material is only somewhat waterproof, it might still seem impermeable when sprayed, while holding several gallons would show that it can't stand up to long, heavy exposure.

posted over 8 years ago

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Karen‭

136 reputation 1 36 14 0