I recently purchased a Dive Rite Travel EXP. Dive Rite states that the wing has 25# of lift in freshwater. I was wondering what the lift would be in saltwater? I figured 4-6# greater lift in salt water?? Anyone know how to figure this out? Thanks in advance.
bc lift
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The buoyancy of a given volume is directly related to the mass of the liquid. Fresh water weights 62.3 Lbs/Ft³ (rounded) at sea level at 32° F/0° C. The average weight of sea water, which varies due to salinity and other contaminants, is 64.1 Lbs/Ft³ (I know, most calculations round to 64 Lbs).
Therefore, on average, salt water is heavier by ~2.9%. Your 25 Lb displacement in fresh water becomes 25.725 Lbs in sea water.
Therefore, on average, salt water is heavier by ~2.9%. Your 25 Lb displacement in fresh water becomes 25.725 Lbs in sea water.
Thanks for the reply. I was just looking at the DR site and it states:"Recently, Dive Rite issued new lift capacities for their wings based on CE tests that use displacement volume in fresh water, and our website reflects these new more conservative lift values. In other documentation, you may see other lift rating values, but the wings have not changed... just the method used to perform the tests. Most other brands express lift in terms of saltwater, but the difference in lift between fresh and salt water is significant; a wing that has 45 lbs of lift in fresh water will have 51 lbs of lift in saltwater."
So you can see why I was thinking 4-6 lbs greater in SW vs. FW. It's similar I guess to the amount of weight needed in fresh vs salt: I use 10 lbs in salt and 6 lbs in fresh when using the same equipment and exposure suit. I wonder how DR arrived at their conclusions that the difference is "significant", whereas your calculation increases the lift by less than a pound? I follow the logic of your calculations but am still a bit confused by the discrepancy.
So you can see why I was thinking 4-6 lbs greater in SW vs. FW. It's similar I guess to the amount of weight needed in fresh vs salt: I use 10 lbs in salt and 6 lbs in fresh when using the same equipment and exposure suit. I wonder how DR arrived at their conclusions that the difference is "significant", whereas your calculation increases the lift by less than a pound? I follow the logic of your calculations but am still a bit confused by the discrepancy.
Perhaps physics is underemphasized in the marketing curriculum? 
Here are some links:
Archimedes' principle - Wikipedia, the free encyclopedia
How much does sea water weigh per cubic foot
Note that there is some wiggle room in the average weight of fresh water, but it is usually between 62.3 and 62.4 Lbs/Ft³.
Here are some links:
Archimedes' principle - Wikipedia, the free encyclopedia
How much does sea water weigh per cubic foot
Note that there is some wiggle room in the average weight of fresh water, but it is usually between 62.3 and 62.4 Lbs/Ft³.
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