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**freedivernd** · 11-10-2008, 05:10 PM,

o.k., you all know I don't scuba much but I'm thinking I might go scuba diving ... maybe once, this winter. salt water.. maybe...
anyway.. can anyone tell me how much lead is needed to offset a steel or aluminum tank and bc.. I don't know.. maybe the standard rental size at most dive shops around the carribean what ever that may be. Tell me salt water or fresh. I've a pretty good idea what I would use in fresh water.. but can't remember what I used the last time in the salt.. no clue. I do know it wasn't quite enough as I had to swim a bit at the deco stop to stay down.

I know, I know.. that's a pretty general question but I'm only looking for a somewhat general answer. just curious about offsetting the tank and bc. any ideas (don't say stick to freediving or any other smart remarks please.. I know you're all nice people!)

Fred

Mr.Pitbull · 11-10-2008, 06:08 PM,

General answer:

Average height & weight, Aluminum 80, Jacket style BC, . 7 mil wet suit, fresh water = 24lbs lead

Average height & weight, Aluminum 80, Jacket style BC, 5 mil wet suit, fresh water = 20lbs lead

Average height & weight, Aluminum 80, Jacket style BC, 3 mil shorty, fresh water = 16lbs lead

Average height & weight, Aluminum 80, Jacket style BC, 3 mil shorty, salt water = 18lbs lead

Hope that helps Fred

arcFlash · (This post was last modified: 11-11-2008, 09:20 AM by arcFlash.)

For us of less average weight...(mostly gristle and sinew)

Aluminum 80, Jacket style BC, 3 mil shorty, salt water = 5lbs lead

Aluminum 80, AL Back Plate and wing, 5 mil wet suit, fresh water = 8lbs lead

For reference. When I snorkel in the ocean I can hover at 12 feet without weight so it's a huge range.

I'm 5'11" and 150 maybe 145.

**freedivernd** · 11-11-2008, 09:58 AM,

good answers and they do help a bit.. but I was wondering specifically (gee, I thought I said generally Wink

) if anyone knew what was needed to just offset, say, the tank. or to offset just the b.c. if anything. If a person put the tank in the water with 500psi left and wanted it somewhat neutral or slightly negative at -15'.. what would you need to strap on the the thing?

arcFlash · 11-11-2008, 11:06 AM,

Sorry, I've never measured that but the charts say +3.4 lbs @500 psi for Luxfer (I would subtract for Reg weight)

You could always ask to use your dive shops pool for 10 minutes and add 3%.

mcdiver · 11-12-2008, 10:23 PM,

A big factor that determines how much weight you need is the BC that you use. I was using a SeaQuest BC and could not figure out why I was not able to stay down as compared to my DiveRite BC with aluminum backplate.

I went to the pool and put weights into each BC to see how much weight it actually took to get the BC to submerge. The SeaQuest with my "built in" surface marker took 6 pounds while my DiveRite with aluminum backplate took just 1 pound. No wonder I had a hard time getting and staying down with the SeaQuest, that's a difference of 5 pounds, holy cow.

Average height and weight is to vague, you have to take into consideration your body composition or body fat and how relaxed you are in the water. For me, with a 7mm wetsuit and my DiveRite backplate with 80 cubic foot tank, I require 12 pounds in freshwater. With a 3mm shorty, I do not need any weight in freshwater, but need 2 pounds in saltwater. I am 5'9" and weight 195 pounds.

nellamit · 11-12-2008, 10:49 PM,

That would stand to reason. The aluminum backplate probably weighs about 3 lbs, plus the heavy steel buckles and hardware that are probably installed on the harness. In reality, the differance is likely less than 1 lb.

**freedivernd** · 11-13-2008, 12:23 PM,

Yeah, I know exactly what I need for lead while freediving with 1.5mil, 3mil, 5mil, 8mil suits.. that's why I was only asking what was needed to offset the tank and the b.c... the only 2 things that would change other than the regs.

Interesting that your b.c. needed 6 lbs to sink.. so maybe around 4 or so at -15'?
Fred

mcdiver · 11-13-2008, 08:04 PM,

I am sure that the surface marker (which attaches to the dump-valve) didn't help, but it is what it is.

Yes, the aluminum backplate does weight a couple pounds, but the SeaQuest BC, or pretty much any jack-style BC, does initself, remain quite positively buoyant. The backplate rigs are just so streamlined that there is not a lot of drag in the water.

But anyway, back to the initial question, how much weight you need to submerge does in fact depend on what style of BC you choose to use.

Seal · 11-30-2008, 06:00 PM,

Fred whatever you are diving with free diving I would add about 4# to offset the tank assuming there is no current. Then I would add about 2 to three more pounds.