Quick "formula" for buoyancy?

I am new to diving and I was wondering if there is a quick formula to
roughly calculate the amount of weight that is needed for neutral
buoyancy in fresh water?

I know that I will need to experiment to fine tune it, but I am just
looking to for a good starting place. I will be using 1 steel tank
with a 7mm wetsuit.

Thanks in advance,

Kevin

Brokenbones wrote:
> I am new to diving and I was wondering if there is a quick formula to
> roughly calculate the amount of weight that is needed for neutral
> buoyancy in fresh water?
>
> I know that I will need to experiment to fine tune it, but I am just
> looking to for a good starting place. I will be using 1 steel tank
> with a 7mm wetsuit.

10kg. Finetune by adding or substracting until you feel comfortable.

/marcin

"Marcin Dobrucki" <Marcin.Dobrucki@TAKETHISAWAY.nokia.com> wrote in message
news:BJmVc.23232$g4.438162@news2.nokia.com...
> Brokenbones wrote:
> > I am new to diving and I was wondering if there is a quick formula to
> > roughly calculate the amount of weight that is needed for neutral
> > buoyancy in fresh water?
> >
> > I know that I will need to experiment to fine tune it, but I am just
> > looking to for a good starting place. I will be using 1 steel tank
> > with a 7mm wetsuit.
>
> 10kg. Finetune by adding or substracting until you feel comfortable.

That seems to be a lot of weight for fresh water and a steel tank, which is
negatively buoyant.

I usually start with 5% of my body weight and fine tune from there.

I currently weigh 190 lbs. (86kg) With an aluminum 80 in salt water I use 8
lbs (>4kg) with no neoprene. That will stay the same throughout the dive,
leaving me neutrally buoyant at 15 fsw (5m) with 500 psi (50 bar?) for my
safety stop.

Freshwater with a steel tank, I would wear no lead with no neoprene..

If you are wearing a 7 mm, it will compress at depth and therefore lose
buoyancy, which it will later regain as you surface.

YMMV


--
But then again, what do I know?

Lou Vallone

LouVallone@aol.com

http://members.aol.com/LouVallone

Get in a swimming pool and add and subtract weight until you are neutral.
If you have a full tank, add six more pounds after you are neutral.

Do you know how much weight you need in salt water? If so, take the
weight of the system (diver, tank, suit, lead, reg, knife, EVERYTHING),
multiply by .0256, and subtract that much.

--
Chuck Tribolet
triblet@garlic.com
http://www.almaden.ibm.com/cs/people/triblet

Silicon Valley: STILL the best day job in the world.


"Brokenbones" <nospam@sympatico.ca> wrote in message news:jkrbi0dnu8vsjdvbhd5pjp3ktugq9svksv@4ax.com...
> I am new to diving and I was wondering if there is a quick formula to
> roughly calculate the amount of weight that is needed for neutral
> buoyancy in fresh water?
>
> I know that I will need to experiment to fine tune it, but I am just
> looking to for a good starting place. I will be using 1 steel tank
> with a 7mm wetsuit.
>
> Thanks in advance,
>
> Kevin

Brokenbones wrote:
> I am new to diving and I was wondering if there is a quick formula to
> roughly calculate the amount of weight that is needed for neutral
> buoyancy in fresh water?
>
> I know that I will need to experiment to fine tune it, but I am just
> looking to for a good starting place. I will be using 1 steel tank
> with a 7mm wetsuit.
>
There are formulas that will get you started but you need to get in a pool.
Most of the time I look like I would float but in freshwater barely stay
awash when holding my breath.
I've had some really small people who needed far more weight than I did and
some huge people who used little.

As most people gain experience their weight needs drop and as your wetsuit
ages it will loose buoyancy.

I believe he said steel tank, not aluminum.

You need MORE weight in salt water, not less.

"Chuck Tribolet" <triblet@garlic.com> wrote in message
news:10id1rho450rb91@corp.supernews.com...
> Get in a swimming pool and add and subtract weight until you are neutral.
> If you have a full tank, add six more pounds after you are neutral.
>
> Do you know how much weight you need in salt water? If so, take the
> weight of the system (diver, tank, suit, lead, reg, knife, EVERYTHING),
> multiply by .0256, and subtract that much.
>
> --
> Chuck Tribolet
> triblet@garlic.com
> http://www.almaden.ibm.com/cs/people/triblet
>
> Silicon Valley: STILL the best day job in the world.
>
>
> "Brokenbones" <nospam@sympatico.ca> wrote in message
> news:jkrbi0dnu8vsjdvbhd5pjp3ktugq9svksv@4ax.com...
>> I am new to diving and I was wondering if there is a quick formula to
>> roughly calculate the amount of weight that is needed for neutral
>> buoyancy in fresh water?
>>
>> I know that I will need to experiment to fine tune it, but I am just
>> looking to for a good starting place. I will be using 1 steel tank
>> with a 7mm wetsuit.
>>
>> Thanks in advance,
>>
>> Kevin
>
>

In article <10id80s73ubqoeb@corp.supernews.com>, Rudy Benner
<bogus@address.com> wrote:

€ You need MORE weight in salt water, not less.

[snicker]

There's one on every boat...

There is no formula. There is only proper weighting.

--
"We're going to rush the hijackers."
-Jeremy Glick, aboard United Airlines flight 93, September 11, 2001

Kit up with all YOUR standard open-water gear and get in a swimming pool,
preferably with cylinder(s) that are only a little above reserve pressure
(50 BAR / 750psi).

Start with a relatively low amount of lead (say 5Kg/11Lb) and than add
1Kg/2Lb) at a time, until you can stay under the water with a normally full
lung of air (I don't mean a huge busta-lung intake) and BCD/wing empty. A
mate on the pool-side handing you one 1Kg/2Lb weight at a time is a bonus.

That will then be the basis of your fresh-water weighting. Because
salt-water is denser than fresh water, giving MORE buoyancy, you will need
to add a little extra lead to stay down when sea diving. Normally, for an
average diver about 2Kg is sufficient.

If however you do the above with full cylinder(s), you will need to ADD
extra weight, otherwise, as the cylinders are used up during the dive and
become lighter, you will become too buoyant and not be able to stay down.
One way to calculate this amount is to weigh your cylinder when empty an
then again full (a good set of bathroom scales works Ok for this). The
difference in weight is how much you will need to add if you do this test
with a full cylinder. This difference between empty and full weight is the
same, irrespective of whether the cylinder(s) are in water or not.

TonyH.

"Brokenbones" <nospam@sympatico.ca> wrote in message
news:jkrbi0dnu8vsjdvbhd5pjp3ktugq9svksv@4ax.com...
> I am new to diving and I was wondering if there is a quick formula to
> roughly calculate the amount of weight that is needed for neutral
> buoyancy in fresh water?
>
> I know that I will need to experiment to fine tune it, but I am just
> looking to for a good starting place. I will be using 1 steel tank
> with a 7mm wetsuit.
>
> Thanks in advance,
>
> Kevin

Normal saltwater is .0256 more dense than fresh water. THAT formula works like
gangbusters to check out gear in freshwater (a swimming pool, for example), and
then go to saltwater and be right on. (The Red Sea is a bit denser than "normal"
saltwater).

I agree that formulas like "10% of body weight + five pounds" are bullshit. That would
have had me underweighted by about six pounds in my old wetsuit (three 7mm layers),
by about two pounds in my drysuit today, and overweighted a buddy of mine who dives
a single 7mm layer by about 5 pounds. The only formula is to get in the water and get
it right.

--
Chuck Tribolet
triblet@garlic.com
http://www.almaden.ibm.com/cs/people/triblet

Silicon Valley: STILL the best day job in the world.


"Jammer Six" <jammer@invalid.oz.net> wrote in message news:cg6gdn$1kb$0$216.39.146.232@theriver.com...
> In article <10id80s73ubqoeb@corp.supernews.com>, Rudy Benner
> <bogus@address.com> wrote:
>
> ? You need MORE weight in salt water, not less.
>
> [snicker]
>
> There's one on every boat...
>
> There is no formula. There is only proper weighting.
>
> --
> "We're going to rush the hijackers."
> -Jeremy Glick, aboard United Airlines flight 93, September 11, 2001

On Mon, 23 Aug 2004 15:46:14 -0700, "Chuck Tribolet"
<triblet@garlic.com> wrote:

>Normal saltwater is .0256 more dense than fresh water. THAT formula works like
>gangbusters to check out gear in freshwater (a swimming pool, for example), and
>then go to saltwater and be right on. (The Red Sea is a bit denser than "normal"
>saltwater).

The problem is you get guys who insist that you add that 2.6% to the
ballast only and not the entire weight of the diver and rig.

Okay, so if the tank is neutral when empty, there's no reason I need
to wear it when I step on the scale geared up, right? :)



--- Rich
http://richlockyer.tripod.com/