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  #141  
Old 05-08-2022, 10:23 PM
heaviest heaviest is offline
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Default Re: swim rings
I've inherited a Poolmaster floating chair. It was being used by a guy of about 450 pounds and a woman of about 300. She fit in it and floated just fine. Him not so much.

The main float chamber was deflated and they left it for dead, but it's a puncture and not a seam rip. Easiest fix ever.

It's much more substantial than the Intex sit n float, but narrower in the seat. I fit in it less well than he did, and it's super unstable. It'll be better for 300 pound girl than it is for me. Shorts girl isn't going to fit, but I'm going to bring it and hopefully she'll try!
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  #142  
Old 14-08-2022, 12:42 AM
frankfrank frankfrank is offline
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Default Re: swim rings
Originally Posted by heaviest View Post
Spry Girl has finally popped a 36 inch swim ring in
The science of weighting-down a swim ring in a body of water would actually be very interesting, and I don't know what the answer to this is.

One thing for sure, get a 500-pound person who sits on one of these rings, and manages to entirely submerge it. I would think the amount of weight it would take to submerge it, would be the amount that the cubic volume of the (now-somewhat-compressed-and-reduced-in-volume) tube would weigh if, instead, it was filled with water. An inflated tube won't displace an amount of water that exceeds the water-weight that is instead in the form of air.

I don't think so, anyway...

It might even be as simple as calculating the weight of the part of the person that is still above water. What weight is above the water is directly pressing down on the ring.

And the submerged part of the 500-pound person similarly displaces a volume that would be displaced if it was pure water instead of a person.

If the person on the ring exceeds the weight needed to sink the ring, by displacing a volume/weight of water equivalent to what is needed to submerge the ring fully, the ring will go below the surface, how far below determined by the weight and buoyancy of the person. If one were able to procure, let's say, a cross-shaped apparatus (for stability) made of metal, at exactly the weight the ring would be if it were instead made of water, the ring would stay afloat, just the top breaking the surface.

This assumes that the metal apparatus isn't below the surface of the water itself. Because something going below the water displaces water, it will weigh less in the pool.

This is just my thought, but the science would be interesting; is the pressure on a submerged ring ever more than what the water-equivalent of the ring would be?


Any scientists out there? (I think Archimedes' Principle has a say in this...)
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Last edited by frankfrank; 14-08-2022 at 12:50 AM.
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  #143  
Old 14-08-2022, 12:49 AM
Alan Alan is offline
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Default Re: swim rings
Do you guys get laid? My female friends don’t find the inflatable or balloon fetish weird, but laugh at this forum.
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  #144  
Old 14-08-2022, 02:56 AM
heaviest heaviest is offline
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Default Re: swim rings
Originally Posted by frankfrank View Post
The science of weighting-down a swim ring in a body of water would actually be very interesting, and I don't know what the answer to this is.

One thing for sure, get a 500-pound person who sits on one of these rings, and manages to entirely submerge it. I would think the amount of weight it would take to submerge it, would be the amount that the cubic volume of the (now-somewhat-compressed-and-reduced-in-volume) tube would weigh if, instead, it was filled with water.
I believe you are correct. I think the amount of weight it takes to submerge a ring is the weight of the water it displaces. But when you are on a swim ring, some of your weight is on the water directly. Your legs and your butt and your arms are in the water.

I think I've calculated the water volume of 30, 36 and 47 inch swim rings, and probably posted that calculation on this forum (Hello Alan, yeah, I'm a dork! lol). I can't square that with what I've observed, because it's not obvious how much of that weight is born by the inflatable and how much is buoyant in the water. But by observation, someone under 200 pounds can sink a 30 incher sitting upright on it, but someone bigger than that won't sink it laying across it with much of their body floating on the water. By observation, it takes 350 pounds to sink a 36 incher, though it probably displaces less than 350 pounds of water (I don't remember and I'm too lazy to do that calculation again). And I've seen someone weighing 750 pounds not sink a 47 inch ring, though if I recall it displaces less than 600 pounds of water.

If you google the volume of a taurus you'll find a calculator you can plug numbers into, and you can find the volume in cubic inches (or mm) of a swim ring, and then you can multiply that by the weight of a cubic inch of water (also googlable). Remember the calculator takes radii and not diameter.

I just did that for a 47 inch swim ring, which I believe inflates to 43 inches with a 15 inch inner hole, approximately, and displaces 540 pounds of water. But I've seen someone bigger than that not sink it, because some of their weight is in the water and not on the ring.

Inflatables that you sit in a hole work on this principle. Some of your weight is born by your own buoyancy.

Quote:
is the pressure on a submerged ring ever more than what the water-equivalent of the ring would be?
And by that, if you mean, should a 755 pound person stress a swim ring more than a 350 pound person, given that 350 pounds will sink it, too, I do not know. I suspect the answer is yes, but not by as much as you'd think. I can just tell you that it LOOKS like it should pop. Which is the fun of swim rings. The surprise when they don't pop!

Possibly the extra stress once it is submerged comes from the depth of the water it is in. I just googled and you can calculate the pressure in pounds per square inch according to depth. But I can tell you that it doesn't go far under water. When she's got it trapped under her belly, basically under her hips, laying on it, it is maybe 18 inches under water. She's pretty buoyant, even without an inflatable under her. She can float with it under her belly without a lot of help from me to stabilize her. It goes farther under water if she sits upright on it, but then it very much wants to scoot out from under her.

EDIT: Unless I've miscalculated, a 36 inch ring, which is actually only 32 inches inflated, with a 13 inch hole, only displaces 180 pounds of water. I have one inflated to check my numbers. I don't have a 47 inch, so I've just guessed those numbers. Also guessing at 30 inch numbers, 27 inch outer diameter, 11.5 inch inner, displaces about 100 pounds of water. It takes a person almost twice as heavy as the displaced water to sink a swim ring, because of the buoyancy of the person. Sitting upright on it sinks it the most, as more of the body is out of the water.

Last edited by heaviest; 14-08-2022 at 04:37 AM.
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  #145  
Old 14-08-2022, 04:49 AM
heaviest heaviest is offline
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Default Re: swim rings
Another fun fact about the capacity rating of inflatables is that they rate them for stability in the water, not the amount they'll hold without sinking, or popping. Or if they just have to come up with a number without testing, they pick something in the 175-220 pound range (80-100 kg) times the number of people it's supposed to float. Sometimes as high as 250 pounds or more per person, but rarely. But their rated capacity is nowhere near enough to pop them.

There is a manufacturer (GoFloats) that rates their single-person floats at 500+ pounds. They are perhaps more sturdy than usual, but there's nothing special about their stability.
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