New Kid's Questions #5 - How much lead to add

[ZenDiver.3D]

gosh I thought the rule of thumb was 2kg as long as you are kitted up identically --shows what I know

2 kilos is right at 4.4lbs. I start there and do a buoyancy check. Usually they need to add 2 to 3 kilos. So, not much difference there. And a new diver tends to hold air and will go down in that weight after the first few sets of dives and they relax.
OP. Take your pool weight. Then add 5 - 6 pounds, (for me- 2 -3 kilos), and do a buoyancy check. Every diver is a bit different ad nmay take less, exactly that or a bit more. This is why you start lighter and do your check. It is better, in the end, than saving the time and overweighting..........

 

[Rick Murchison]

So...
215 - your weight
40 - tank & reg (standard AL80 at 500 psi + average reg)
8 - generic BC
7 - generic 3/5 wetsuit
10 - fresh water lead you're already carrying
about 280 - total fresh water weight
280X.025=7 pounds (approximately) added to get the same buoyancy in salt water as you're accustomed to in fresh water.
But...
I recommend that rather than varying the baseline air in your BC when you change what you wear, you take the time in the pool to make up a chart of the weight and buoyancy of you, and of each piece of your gear. Then you need only algebraically add your buoyancy numbers for you and the gear you're planning to wear to get your buoyancy/weighting perfect for each and every dive. For salt water add up the weights from the chart and add 2.5%.

Rick

I average 215 lbs body weight. I am a warm water wuss, so if I wear a suit, it's a 5/3 full. My cert dives carried 12 lbs of lead. I dropped 2 and have been diving with 10 since. If I wear my suit, I don't add much air to the bc. If I dive in my shorts, I add a little more to the bc. Not sure that will work for everybody, but it works for me.

Assuming you will be diving salt water with exactly the same equipment and exposure protection that you were using in the pool, you add 2.5% of the total weight of you and your gear. This is usually in the range of five pounds or so.

 

[Lenaxia]

I'm wondering if anyone else has tried this:

Gear up for a pool such that you are slightly overweight, get in the pool and dump all air and try to shake out any residual.

Drop weights one at a time until you are neutrally buoyant. From that you can determine your buoyant force as it should be your starting weight minus whatever you dropped.
From there you can calculate your liquid displacement as (Neutral Weight)/(density of pool water).

Taking your liquid displacement, and multiplying that by the density of seawater should give you the ideal weight to dive at. Theoretically.

I couldn't repress the nerd in me.

 

[Rick Murchison]

...Drop weights one at a time until you are neutrally buoyant...

It's a bit easier than that... just tie a bunch one pounders on a string about 6 inches apart. Hold onto the string and pick up enough weights to get neutral. Or, you can start on the bottom and see how many weights come off the bottom 'til you stop rising. Either way, the weights off the bottom add up to your ideal weighting for neutral.

Rick