Aluminum to Steel Buoyancy Question

[mweitz]

So, I ordered a pair of E7-120's. They will replace my "Neutrally" buoyant AL80's (Luxfer S80N). Here are the specs:

S80N Buoyancy Empty .05, Full -5.75
E7-120 buoyancy Empty -1.3 Full -10.3

So, I figure I'll drop 2 lb from what I'm using now? I'll be 3 lb more "negative" at the start of the dive, and about 1 or 2 lb more negative at the end of the dive. Is this correct or am I missing something?

The E7-120 lists a 3/4-14 thread, and the S80N lists a .750-14 NPSM M25 x 2.0. I assume those are the same?

Thanks,

Mark

 

[teknitroxdiver]

Yes, all new tank threads are the same as far as I know. Only old tanks could be different.

You'll be almost 5 pounds heavier at the start, which doesn't matter anyway. At the end of the dive, you will be 1.35 pounds negative (If you S80N figures are right as being .05 lb positive when empty), so 2 pounds might be too much. Try it dropping 2 first, and if you're light only drop 1.

 

[donacheson]

So, I ordered a pair of E7-120's. They will replace my "Neutrally" buoyant AL80's (Luxfer S80N). Here are the specs:

S80N Buoyancy Empty .05, Full -5.75
E7-120 buoyancy Empty -1.3 Full -10.3

So, I figure I'll drop 2 lb from what I'm using now? I'll be 3 lb more "negative" at the start of the dive, and about 1 or 2 lb more negative at the end of the dive. Is this correct or am I missing something? ...

If it's doubles you're diving, your tanks will be 2x1.35 = 2.7 pounds heavier empty, so dropping 2 or 3 pounds of lead seems to be in order. If singles, drop about 1 pound of lead.

 

[scubasean]

nm

 

[mweitz]

Starting with em as singles. May convert them to doubles in a year or two.

I'll start with 2 lb less since I am already negative on my safety stops ....

Thanks,

Mark