Changing tank size, what amount of weight?

[McKee Boykin]

I am changing from using an al 80 with 32#s of weight in saltwater, how much weight should I use for a steel 120hp in saltwater? steel hp149?

 

[Rainer]

Probably around 6#s (assuming those HPs end -2 which is about right for most of the newer ones).

Edit: Would be helpful if you listed WHICH HP cylinders you bought (make).

 

[Homunculus]

very easy calculations, if you know specs on all the cylinders involved. you need to figure out the difference of buoyancy between two tanks - Al and HP 120 or 149 (an empty tank buoyancy).

for fabers it's +0.65 (HP120) and +2.35 (HP149); assuming Al 80 is +4, then you need 3.35 or 1.65 lbs less lead.

 

[McKee Boykin]

Luxfer 80--Wothington XS120--Faber 149

 

[Rainer]

Moving to the 120 you can take off 6#. For the 149 you can take off 2#.

 

[McKee Boykin]

Thanks for the info.

 

[Homunculus]

if what i found is correct:
-7.3 lbs saltwater buoyancy (full) / -1.5 (empty) for Luxfer 80 cu. ft.
+2.35 for Fabers HP 149
-2 for Wothington XS120

then you need to add 3.85 lbs for 149 and remove 1/2 Lb for 120

 

[Rainer]

Not sure where you found the AL80 numbers. Nearly all AL80s end +4. Found the same for the other cylinders, though.

 

[Homunculus]

Moving to the 120 you can take off 6#. For the 149 you can take off 2#.

why? how did you do your calculations?

 

[Homunculus]

Not sure where you found the AL80 numbers. Nearly all AL80s end +4. Found the same for the other cylinders, though.

i got my Al 80 value from
http://www.huronscuba.com/equipment/scubaCylinderSpecification.html

oops, my bad. i did not read the right value, instead of empty, i got full buoyancy.

so, +4.4 for AL80
Rainer is correct, remove 2 for 149 and 6 for 120