Brand new diver...buoyancy control issue or weight?

[hudson]

The air in your tank weighs about 6lbs. You need to be negative by at least 7lbs in the beginning of the dive to compensate for that.

I would add at least 4lbs and go from there.

(Also make sure you exhale fully)

 

[Mrs. H.]

Thanks for all the advice. I'm going to make sure I do a proper weight check with an almost empty cylinder when we go diving next time, and I'll check on the completely letting air of the BC thing as well.

 

[TSandM]

You can do the weight check at the beginning of the dive, with full tanks. Weight yourself neutral at the surface with full tanks, and then add the weight of the usable gas in the tank (for an Al80, that's about five pounds). Err on the side of being a couple of pounds heavy, if you're unsure or don't have weights in the precise amounts needed.

It's frustrating and makes your buoyancy job a bit more difficult to be overweighted, but you are much safer slightly (2 or 3 lbs) heavy than too light. Being too light makes the end of a dive a major PITA, too; takes the fun right out of it.

 

[reefugee]

TSandM hit it right on the head. Most aluminum tanks are 5 lbs lighter when completely empty vs when full. So take her advice - do a weight check at the beginning of a dive. For a beginner, I would add at least 8lbs (5lbs for an empty tank and another 3 lbs for a beginner). As you get more experienced, you will be able to shed the extra 3lbs. I can't believe how much weight I used to carry when I was a newbie (still consider myself a newbie). Good luck and have fun!

 

[hudson]

Easiest way to find the full/empty delta is to multiply the capacity of the tank by 0.075

So in the case of an AL80 which is 77.4cuft, you end up with 77.4*0.075=5.8lbs