Newbie Monterey weighting question

[Hinalo]

Thank you all so much. This is incredibly useful. I'm off to do Chuck's executive summary.

 

[paulwlee]

ADD the weight of the gas in the tank, not subtract. And a full AL80 has closer to
6 pounds of air.

Duh. Thanks Chuck for correcting that mistake.
Yes. ADD.

As for the 6lbs, yes, the tank does hold 6lbs of air, but if you plan on not going below 500psi, then it will be 5lbs. Since your lungs swing several pounds in terms of buoyancy, if you ever need to suck your tanks dry you will still be comfortably able to maintain neutral buoyancy if you are weighted to be neutral with a neutral lung volume at 500psi. There's also the question of what "neutral lung volume" is, as it's really a range..

Hmm.. there, I did it again, getting all verbose, I need to learn to be concise like Chuck..

 

[egdiver]

Aint science dandy ! or
With a full tank and an empty BC, ajust your weight so you float at head height holding a normal breath, add the weight of the air in your tank in lead (or a small volkswagen) ... for an AL 80 it's almost 6 lbs.
At the end of the dive with 800 lbs of air left you should neutral at 15 - 20 ft
for comfy safety stop... results will vary !

 

[Chuck Tribolet]

That's all fine and dandy IF you have access to salt water and a collection of weights
on the wet side of the beach. A fair number of folks can scrounge access to fresh water
and a collection of weights. And you don't blow off a dive in Monterey. And results
don't vary -- it's high school physics.

Aint science dandy ! or
With a full tank and an empty BC, ajust your weight so you float at head height holding a normal breath, add the weight of the air in your tank in lead (or a small volkswagen) ... for an AL 80 it's almost 6 lbs.
At the end of the dive with 800 lbs of air left you should neutral at 15 - 20 ft
for comfy safety stop... results will vary !

 

[zf2nt]

Aint science dandy ! or
With a full tank and an empty BC, ajust your weight so you float at head height holding a normal breath, add the weight of the air in your tank in lead (or a small volkswagen) ... for an AL 80 it's almost 6 lbs.
At the end of the dive with 800 lbs of air left you should neutral at 15 - 20 ft
for comfy safety stop... results will vary !

Because of the risk of surfacing in the middle of kelp, I believe CA divers should weight themselves to be neutral on the surface when their cylinder has only 500 psi of air. Since the buoyancy swing between maximal exhalation and maximal inhalation is on the order of 8 pounds for a typical adult male, weighting this way gives you the ability to go several pounds negative by strongly exhaling and then descend feet first if you need to swim under the kelp bed to reach a clear area. This is distinctly different weighting from what we recommend for tropical waters, which is to be able to stay down 15' on a near empty tank.

 

[egdiver]

That's all fine and dandy IF you have access to salt water and a collection of weights
on the wet side of the beach. A fair number of folks can scrounge access to fresh water
and a collection of weights. And you don't blow off a dive in Monterey. And results
don't vary -- it's high school physics.

It's OK Chuck !

There are several ways of achieving the end result, Fine tuning your attitude in the water is a variable that relates to each indivigual and different applications... In the end I am sure that everyone agrees that having the correct amount of weight allows for less effort and gas consumption as well as controlled and safe acents !
Happy diving,

Shaka...

 

[paulwlee]

gives you the ability to go several pounds negative by strongly exhaling and then descend feet first if you need to swim under the kelp bed to reach a clear area. This is distinctly different weighting from what we recommend for tropical waters, which is to be able to stay down 15' on a near empty tank.

You don't need to become several pounds negative to descend, but you do have a good point here as the buoyancy change between 15' and the surface is a lot more for divers with thick wet suits, maybe as much as several pounds, perhaps more than can be comfortably compensated by lung volume for some people.

BTW, this reminds me, for divers with shell drysuits, depth doesn't matter, as there is no buoyancy change with depth. (although the OP did say he was wearing a wetsuit..)

 

[mtbrider]

2.56% for typical sea water. Some almost enclosed systems (most notably the Red Sea)
are a bit denser. That .06% is about a pound and a half of lead.

Maybe if you are the Incredible Hulk. I'm guessing that should be about 0.15 lb of lead difference with 0.06 % change.

Chuck, do you know of any web sites with data on the salinity of the world's oceans?

 

[Chuck Tribolet]

Maybe if you are the Incredible Hulk. I'm guessing that should be about 0.15 lb of lead difference with 0.06 % change.

Chuck, do you know of any web sites with data on the salinity of the world's oceans?

Yep, I slipped a decimal point. But we might as well keep it as accurate as possible.

Try Googling

ocean salinity "Red Sea"

I think you'll find it.

 

[mtbrider]

Google is your friend. :14:

I found a chart of the world's salinity, it's kinda cool.
ftp://ftp.nodc.noaa.gov/pub/WOA05F/salinity/PDF/s_0_0_1.pdf

Can't really convers PSS to fresh vs salt water weight because of other dissolved solids.

Sorry for the thread hijack. :blinking: