08-04-2008, 09:03 PM
[cool][#0000ff]You are correct. The basic laws of physics state that DISPLACEMENT OF WATER = BOUYANCY. A tube that holds 3 cubic feet of air...at whatever pressure...and made of whatever material...will displace only 3 cubic feet of water. And, the weight rating will be equivalent to the weight of the water displaced...not the size or shape of the bozo using the float tube.[/#0000ff]
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[#0000ff]It is amusing to keep reading all of the pseudo technical opinions and assumptions...that urethane is stronger so it will float higher, etc. Also, the relative weight of the air bladder material will not make even a fraction of a difference in the floatation. Unless you are talking about lead vs vinyl. Then there would be enough weight to partially offset the water displacement weight.[/#0000ff]
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[#0000ff]And...what everybody is overlooking is that there is not a universal standard for thickness of either vinyl or urethane in air bladders. A heavy mil thickness of vinyl could conceivably be just as strong and durable as "standard" urethane.[/#0000ff]
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[#0000ff]I HAVE been doing some heavy research on the differences in properties between urethane and vinyl. THERE IS NO DEFINITIVE WRITING OR WEBSITE that is devoted to addressing this issue, in the matter of float tube or pontoon air bladders. The best we can do is project or extrapolate from information that IS available. [/#0000ff]
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[#0000ff]To distill what I have found: Urethane does have properties which make it more desirable for use as an air bladder for inflated items. On a mil per mil basis, it does have less elasticity and will hold more air pressure without material degradation or failure. That is probably why it is the quality standard of the air bed industry...even though there are some with thicker vinyl that have good warranties.[/#0000ff]
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[#0000ff]PVC (vinyl) is less costly to make and the material is subject to the "migration" of polymers over time. In other words, vinyl does not remain stable or reliable as long as urethane. But, we are talking about decades...not a couple of years of use in a float tube.[/#0000ff]
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[#0000ff][/#0000ff]
[#0000ff]It is amusing to keep reading all of the pseudo technical opinions and assumptions...that urethane is stronger so it will float higher, etc. Also, the relative weight of the air bladder material will not make even a fraction of a difference in the floatation. Unless you are talking about lead vs vinyl. Then there would be enough weight to partially offset the water displacement weight.[/#0000ff]
[#0000ff][/#0000ff]
[#0000ff]And...what everybody is overlooking is that there is not a universal standard for thickness of either vinyl or urethane in air bladders. A heavy mil thickness of vinyl could conceivably be just as strong and durable as "standard" urethane.[/#0000ff]
[#0000ff][/#0000ff]
[#0000ff]I HAVE been doing some heavy research on the differences in properties between urethane and vinyl. THERE IS NO DEFINITIVE WRITING OR WEBSITE that is devoted to addressing this issue, in the matter of float tube or pontoon air bladders. The best we can do is project or extrapolate from information that IS available. [/#0000ff]
[#0000ff][/#0000ff]
[#0000ff]To distill what I have found: Urethane does have properties which make it more desirable for use as an air bladder for inflated items. On a mil per mil basis, it does have less elasticity and will hold more air pressure without material degradation or failure. That is probably why it is the quality standard of the air bed industry...even though there are some with thicker vinyl that have good warranties.[/#0000ff]
[#0000ff][/#0000ff]
[#0000ff]PVC (vinyl) is less costly to make and the material is subject to the "migration" of polymers over time. In other words, vinyl does not remain stable or reliable as long as urethane. But, we are talking about decades...not a couple of years of use in a float tube.[/#0000ff]
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