Tank bouyancy, help in comprehending

[Central Fla]

I apologize I didn't say what I meant, I wont be removing 13 pounds of lead but won't the combined effect of removed weight and less tank weight be 13 pounds ??

 

[The Kraken]

Nope.
Think about it this way . . . you're floating, neutrally buoyant at 15' with an aluminum 80. That 80 is trying to push you up toward the surface with a force of 4 pounds of positive buoyancy, so in order to counteract that force, you have to wear 4 pounds of lead.

Now all other things being equal, if you removed the tank from your body, that four pounds of lead would have to be dropped to keep you from sinking.

Now you strap on a steel tank. The steel tank is 3 pounds negative. So all other things remaining equal, you'll have to drop another 3 pounds of lead to remain neutrally buoyant.

So all in all, you've dropped 7 pounds of lead to remain neutrally buoyant with the steel tank.

the K

 

[D_B]

according to this chart ... http://www.techdivinglimited.com/pub/tanks.html

on land .. an al80 is 31lbs and the steel X7 80 is 28lbs ... 3lbs difference on land + your dropping 7lbs more lead = 10lbs less walking to the dive point

 

[DoItRite]

How can you say it does not look much different when it is nearly half a foot longer?

Heh...that's what she said.