PFD floatation - question - Mountain Buzz
 



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Old 06-30-2008   #1
 
FatmanZ's Avatar
 
Northern Utah, Utah
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PFD floatation - question

Why doesn't the floatation in PFD's increase with the size of the PFD? For example, my friend weighs 125 dressed for cold temps, I'm well over 250 dressed the same. We both use the same type of Astral PFD - his is size S/M and mine is L/XL. Yet the amount of floatation is the SAME for both - 16.5lbs.

Any reason why (other that cost) that manufacturers don't offer more lbs of floatation in the larger sized PFD's?

Even with the hi-float type PFDs that have around 22lbs floatation - it's the same lbs of floatation regardless of what sized PFD.

Thoughts?

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Old 06-30-2008   #2
 
Cisco, Utah
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As I recall, a test from underwritters lab... 95% public weigh between 14 & 15.5 lbs in the water (under water?). So past the weight of skin & Bones alot of what a person is made up of is either neutral or negative boyancy (75%ish water essentially)

So these figures are from trying to remember many many years ago, and are probably not exactly accurate, but this is the concept / theory / resoning...

A Pfd only has to float more than 15 lbs to make you possitively boyant. Certain situations any more boyancy can be a problem (recirced in a hole, etc.) A lot of people feel high float pfd's are most suited to High Volume Rivers (Grand Canyon etc.) while lower float is just fine if not better for rivers such as in colorado; lower volume... Lower profile of pfd is also a valid consideration beside just comfort.

So there you go. How much do you weigh in the water? Can your friend pick you up in the water? On land?....
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Old 06-30-2008   #3
 
Denver, Colorado
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Quote:
Originally Posted by UserName View Post
As I recall, a test from underwritters lab... 95% public weigh between 14 & 15.5 lbs in the water (under water?). So past the weight of skin & Bones alot of what a person is made up of is either neutral or negative boyancy (75%ish water essentially)

So these figures are from trying to remember many many years ago, and are probably not exactly accurate, but this is the concept / theory / resoning...

A Pfd only has to float more than 15 lbs to make you possitively boyant. Certain situations any more boyancy can be a problem (recirced in a hole, etc.) A lot of people feel high float pfd's are most suited to High Volume Rivers (Grand Canyon etc.) while lower float is just fine if not better for rivers such as in colorado; lower volume... Lower profile of pfd is also a valid consideration beside just comfort.

So there you go. How much do you weigh in the water? Can your friend pick you up in the water? On land?....

I am no expert on flotation and PFD's, but I think what the previous poster is saying makes sense. A stocky, muscular 125lb person will have a harder time floating in water than a 275lb, shall we say less muscular person. That being said, I assume the testing each PFD undergoes to get certified would factor in different body weights, shapes, etc. and the floatation is safe for all variables. That maybe a wrong assumption though.

I would also like to hear peoples opinion on high float (over 20lbs) and standard 16lbs or so PFD's. Do you think the floatation should change if you are kayaking vs. rafting?
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Old 06-30-2008   #4
 
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SE, Wyoming
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specs and production cost

I asked a friend in the gear biz and he said that it was cheaper to cut (or mold) a standard set of foam floats for a certain model of PFD and then pattern different dimensions of fabric to fit the varying body sizes.

Some makers might spec out a target flotation and just keep that number for their catalogs and stuff that gets printed in advance of actual production runs. For instance, the prototype gear shown at the big OUTDOOR RETAILER shows is a year ahead of the market, so the specs can change by the time stuff actually hits the shelves.

Some designs (like the ExtraSport Hi-Float) use foam blocks that can be easily cut to different lengths, so their buoyancy might actually vary by size. The label in my size XL says 24 lb 1 oz. The Cascade Outfitters catalog says 26 lb 12 oz. But since Johnson Outdoors bought them up, who knows.

Chip
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Old 06-30-2008   #5
 
Salida, Colorado
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Here is the real deal

Most people out there weigh between 10-12 lbs in the water, which is a neutral buoyant state.

To break it down more, a larger individual will take a little less buoyancy as they will displace more water to float them easier, where as a skinny person will displace less water therefor they tend to sink, so bigger folks tend to float easier.

Yes, it costs a ton of money to change the buoyancy for each individual size, because to get these things certified, each individual part needs to be tested separately. So for each size change that is another set of tests therefor increasing the cost of the product to you the consumer, which I know you all would love.

So the manufacturers use one size for foam for the size run.

It is the same thing with ski boots, they make 1 shell size for 4 boot sizes.

I hope that helps.
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