fresh /saltwater formula

[Thalassamania]

Salinity is usually considered to be 3.5%: Salinity

 

[spectrum]

WOW I must be really dense or am not expressing myself properly!

You're cool, my error.

As stated the suit delta by it's self is such a minority in your overall configuiration that it amounts to a rounding error in what you are already doing. The suit adjustment will be the same in any water with all else constatant. It is possible that it may prompt a borderline configuration to shift by an increment. More likely the lack of massive amounts of neoprene will will liberate you dive your lung volume more and reduce what you need.

The same logic applies to calculating SW weight from FW or the reverse.

Pete

 

[Charlie99]

Salinity is usually considered to be 3.5%: Salinity

What counts is DENSITY. Look at the 3rd paragraph of the wikipedia link you provided: "The density of seawater is between 1020 and 1030 kg·m-3".

Since adjustments to weighting rely upon DENSITY, not salinity, the recommendation to add lead weight equal to 2.5 to 3% of the total weight is correct. (3% rather than 2.7% because lead has specific gravity of 11)

Here is a plot of density vs. both temperature and salinity.

 

[LI Diver]

Thanks everyone, Wow I often wondered about the temp versus the density Charlie, and looking at the graph it looks substantial. Do I need to add considerable weight diving here in ny compared to tropical diving in the key's etc.. Lets just say there is a 15 degree difference and all else equal for arguments sake???

 

[Thalassamania]

Right you are.

 

[LI Diver]

who's right????

 

[Charlie99]

Thanks everyone, Wow I often wondered about the temp versus the density Charlie, and looking at the graph it looks substantial. Do I need to add considerable weight diving here in ny compared to tropical diving in the key's etc.. Lets just say there is a 15 degree difference and all else equal for arguments sake???

Let's say that you are a really, really hardy diver that uses the same wetsuit for 10C/50F and 25C/77F. In relatively salty seawater of 3.6% salt content, the density varies from 1.028 to 1.024kg/liter. 0.4% difference is just 1 pound for a diver with total dive weight of 250 pounds. The variation in fresh water density is about the same; perhaps a bit less over that specific temp range.

In real life, most divers will change exposure protection before density vs. temp effects become more than 1 pound.

 

[Thalassamania]

who's right????

Everyone's correct. I was typing in haste and just thinking about salinity, which was not really the question at hand. With respect to the specific density question Spectrum and Charlie are correct at 2.6%

 

[LI Diver]

Thanks Charlie, So basically insignificant for my uses. I'd like to try a shallow dive here with my 5 mil full at the time of the year when the water is the warmest (now) and we are having an exceptionally warm year from what I understand.I will most likely add a hood so for that alone I will probably have to add a couple lbs.

 

[Thalassamania]

Not insignificant. That's 2.6% of the mass of the water that you displace in full gear, not 2.6% of the lead that you currently carry.