Quick weight question

[rogersab1223]

I dive in board shorts and rash guard in the carribbean with 8 lbs and in 7mm in a fresh water quarry I use 18 lbs.

I'm diving off morehead city (saltwater) in a new 3mm wetsuit.

What weight should I start with?

 

[guruboy]

IIRC, it's about 2lb/mm (add or remove) and salt/fresh is about 4lb (add/remove)

 

[dfx]

As a purely academic exercise, assuming your total weight (yourself + all your gear incl a full AL80 but without any weights) is 200 lbs, and that your current weighting makes you neutral with an empty tank, we have...

Subtracting the weight change of the tank of 5 lbs, you'd produce 203 lbs of buoyancy in salt water with your rash guard. Therefore in fresh water, you'd produce 198 lbs of buoyancy. You would only need 3 lbs of weight with the same gear.

With your 7 mm, (neglecting the weight of the suit) you'd produce 213 lbs of buoyancy. In salt water, that equals 218 lbs of buoyancy. You'd need 23 lbs of weight with the same gear.

So in salt water, between 0 and 7 mm wetsuit, you have a difference of 15 lbs in weights. That comes out as around 2.1 lbs per mm of wetsuit. So with a 3 mm, you'd need 6-7 lbs of extra weight, making it 14-15 lbs.

Yeah I was bored...

 

[rogersab1223]

Wow... Thanks!

 

[Steve_C]

Are the tanks the same?

In the carib you are most likely diving an AL80 unless you bring your own.

Along the NC coast be it Morehead or Wilmington or Hatteras, when folks rent a tank they often rent larger tanks like 100 or 120 in AL or Steel since the dives are usually a bit deeper. They also usually rent nitrox.

Personally I rent/use AL80s most of the time in the Keys and dive my own HP steel 100s in NC. I am typical in that regard.

 

[spectrum]

They also usually rent nitrox.

That just sounds wrong, but I know what you mean.

 

[DivemasterDennis]

I like dfx analysis. I would suggest the same, but get there differently. I also presume all other gear, including type and size of tank, is the same.
DivemasterDennis