Buoyancy check - Is this a better way?

NJdiver85 · Sep 13, 2005

In order to get appropriately weighted, the common directive is to use a tank with approx 500 PSI of air in it, and determine how much weight you need such that you can just sink below the surface with your bc fully deflated. The problem with this, which I see all the time, is that because you can only do this buoyancy check at the end of a dive, that first dive amounts to alot of guess work. Isn't a better procedure something like this: With a FULL tank of air, determine how much weight is necessary such that you just sink below the surface with your BC fully deflated. Once that weight amount is determined, add to that an amount to compensate for the bouyancy swing in the tank as it goes from full to 500 PSI. For an AL80, that should be close to 5 pounds.

Spoon · Sep 13, 2005

if you do that procedure relying on your full tank to determine your weighting then you will only find out , based on my exp that at the end of the dive you will either be underweighted or perfectly weighted. i prefer being overweighted in the beginning and judging my weighting at the end of the dive, if i dont flop to the surface and fight myself to stay down then im fine if im not then im underweighted. dont rush it it took me over 20 dives to get my weight right and just last week i shed another 2 lbs. trial and error , dont sweat it. good luck

NJdiver85 · Sep 13, 2005

Spoon:
if you do that procedure relying on your full tank to determine your weighting then you will only find out , based on my exp that at the end of the dive you will either be underweighted or perfectly weighted. i prefer being overweighted in the beginning and judging my weighting at the end of the dive, if i dont flop to the surface and fight myself to stay down then im fine if im not then im underweighted. dont rush it it took me over 20 dives to get my weight right and just last week i shed another 2 lbs. trial and error , dont sweat it. good luck

Well maybe one could modify the rule such that you add the tank swing amount PLUS 1-2 pounds. Overall, it just seems that this methodology would avoid lots of trial and error and is easier since you are starting with a full tank which is what you have before starting a dive. At least you could get the correct weighting to within 1 or 2 pounds at the start of your first dive. With respect to myself, I have over 200 dives logged and excellent buoyancy. But I see many new divers each week on dive charters that don't know their correct weighting requirements.

Spoon · Sep 13, 2005

tbg:
Well maybe one could modify the rule such that you add the tank swing amount PLUS 1-2 pounds. Overall, it just seems that this methodology would avoid lots of trial and error and is easier since you are starting with a full tank which is what you have before starting a dive. At least you could get the correct weighting to within 1 or 2 pounds at the start of your first dive. With respect to myself, I have over 200 dives logged and excellent buoyancy. But I see many new divers each week on dive charters that don't know their correct weighting requirements.

well you could do that if you wanted. i myself think that my buoyancy is perfect but who knows, maybe if i attempted shaving an extra couple of lbs maybe i would even improve. as far as i am concerned i am having to inflate my bc less now with the reduction in 2 lbs and i have also noticed a fraction of an increase in my air consumption. but for what its worth you can modify the original weighting rule, add 2 lbs til you sink slightly and observe your weighting towards the end of the dive with a near empty tank. whatever works . but you are correct i do in fact see a lot of over weighted, underweighted divers being taught the floating rule with the full tank.

countryboy · Sep 13, 2005

What you stated should be close... to start with.

Neutral at the beginning of the dive (empty BC), add weight to compensate for the air you will consume (figure you will consume all the air).. Add 1 -2 lbs "extra"... if you are not too sure...

Perform check at end of dive.
Perform check at the end of every dive... You will be surprised how quicky you will start to need less weight... (not you per se, but you know what I mean)..

I think Rick had a contribution to a thread where he explains the measuring of each piece of gear, and created a table. This would be preferable, although with newer people, your ballpark figure will give a good starting point.. especially if they rent gear.

Spoon · Sep 13, 2005

countryboy:
What you stated should be close... to start with.

Neutral at the beginning of the dive (empty BC), add weight to compensate for the air you will consume (figure you will consume all the air).. Add 1 -2 lbs "extra"... if you are not too sure...

Perform check at end of dive.
Perform check at the end of every dive... You will be surprised how quicky you will start to need less weight... (not you per se, but you know what I mean)..

I think Rick had a contribution to a thread where he explains the measuring of each piece of gear, and created a table. This would be preferable, although with newer people, your ballpark figure will give a good starting point.. especially if they rent gear.

do you have a link to that table? id love to check that out?

BrianS · Sep 13, 2005

http://www.scubaboard.com/showthread.php?t=111907

countryboy · Sep 13, 2005

Thanks for posting the link to the thread... it's post #9...

DavidHickey · Sep 13, 2005

http://dive.scubadiving.com/html/200105buoyancycalc_chart.html

Not sure if I did this right but here is a link to a Weight Calculator I found awhile back. I've never tried it so not sure how good it is. If the link does not come thru and your interested let me know and I will email it

all4scuba05 · Sep 13, 2005

does it make a difference that my body weight fluctuates daily as much as 3lbs?...and I don't mean after a bowel movement

Buoyancy check - Is this a better way?

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