Weights between fresh and salt water

[cfelliot]

Is there a general rule or ratio for weights between fresh and salt water? I just bought my own equipment and am going to do a checkout dive in the local pool before our trip to Hawaii this spring. I’d like to use this time to get things set up as best as possible.

 

[peter_dorset]

Is there a general rule or ratio for weights between fresh and salt water?

According to PADI this is what you are looking for:

Amount of Weight to Add (Fresh Water to Salt Water) Subtract (SaltWater to Fresh

Body Weight
45 - 56 kg/100 - 125 lb. .............. 2 kg/4 lb.
57 - 70 kg/126 - 155 lb. .............. 2.3 kg/5 lb.
71 - 85 kg/156 - 186 lb. .............. 3 kg/6 lb.
86 - 99 kg/187 - 217 lb. .............. 3.2 kg/7 lb.

I keep this table in my log book.

Dont forget that the bigest change can be from your exposure protection example I use 7mm semi dry in the UK (salt water) and use about 11kg. In Egypt I use about 2k since I am using a 1mm suit. Thinner the suit the less weight is required.

Worth also remembering to streamline your kit. So you have no loose hoses dangling nice tight package. It’s amazing how much drag a dangling Octopus give and how it can affect your air consumption not to mention the damage it can cause

Enjoy your holiday

Peter

 

[FredT]

Some very basic physics is involved here.

If you are properly weighted to neutral in either fresh or salt with an empty BC, weigh yourself and all the gear you wear. The weight of water that gear displaces changes by a ratio of about 62.4/64.2 between fresh and salt water. When you finish running the numbers it's necessary to add or subtract lead in the amountof ~0.029 times the weight of you and all your gear to adjust the buoyancy.

lf going from salt to fresh remove lead.
If going from fresh to salt add lead.

Just WHERE you should add the lead is a factor of your individual trim. Your trim will change a bit based on your body configuration and gear component buoyancy characteristics.

FT

 

[cfelliot]

Fred,

Thanks, your reply was exactly what I was looking for.

Chuck