Weights adjustment when switching to an HP Steel Tank

[Capt.JimDavis]

How to adjust the weights with a steel tank?
During my OW certification course I was wearing 36lbs with Al80.
I am 240lbs. and diving with a 7 mil wetsuit.
I am thinking to buy an HP100 and buoyancy specs indicates as;
Full: -10lbs
Empty: -2,5lbs.

So, does it mean I can drop 10 lbs of weight at the beginning of the dive and expect the similar results like when I was diving with 36lbs weight +Al80? (with a little better result at the end of the dive because of the -2,5 lbs compare to positive buoyancy of the Al80)
:blinking:

 

[RJP]

How to adjust the weights with a steel tank?
During my OW certification course I was wearing 36lbs with Al80.
I am 240lbs. and diving with a 7 mil wetsuit.
I am thinking to buy an HP100 and buoyancy specs indicates as;
Full: -10lbs
Empty: -2,5lbs.

So, does it mean I can drop 10 lbs of weight at the beginning of the dive and expect the similar results like when I was diving with 36lbs weight +Al80? (with a little better result at the end of the dive because of the -2,5 lbs compare to positive buoyancy of the Al80)
:blinking:

Depends on exactly which AL80 tank you're talking about, but the "lead" difference will be closer to 5lbs. For instance a Catalina 80 is +2.8lbs buoyant empty, so that's a net difference of 5.3lbs vs the HP100 you cite above.

Assuming your weighting is correct with the AL80, all you need to do is subtract the "empty buoyancy" of the AL80 from the "empty buoyancy" of the Steel to tell you how much you can drop (-2.5lbs minus 2.8lbs = -5.3lbs)

 

[dwaters]

Depends on exactly which AL80 tank you're talking about, but the "lead" difference will be closer to 5lbs. For instance a Catalina 80 is +2.8lbs buoyant empty, so that's a net difference of 5.3lbs vs the HP100 you cite above.

Assuming your weighting is correct with the AL80, all you need to do is subtract the "empty buoyancy" of the AL80 from the "empty buoyancy" of the Steel to tell you how much you can drop (-2.5lbs minus 2.8lbs = -5.3lbs)

I agree with above... I'm just over your wieght and dropped 6 lbs of lead when I bought my steel 100HP after 20 dives on AL80 here is So.Cal diving wet in a 7mm full suit and built in Biopreme(tm) In the course of few years and 100+ dive later I was able to drop another 6 lbs. If I am forced to rent a AL80, I still have to add 5 lbs to make it work.

 

[BonaireDan]

Agree also. Drop 6 pounds and check it out. I dive OW with steel HP100 and in 7mm use 14 pounds. I weigh 200 pounds. In 3mm I have been able to get down with no weight if I am feeling good, rested, not rushed, not teaching, etc.

 

[HowardE]

I would agree with 6 Lbs to start.

 

[diver 85]

If I were you, I'd go with a 120 steel---even more wt to drop(38 is ALOT of baggage to carry around on a belt or in a BC)--& more air on your back, either of both is a plus..

 

[MaxBottomtime]

Scuba Cylinder Specifications from Tech Diving Limited - 928-855-9400
Once you get more dives under your belt you will be able to drop some lead as well. I'm around 240# and wear 18# with a drysuit and 14# in a wetsuit.

 

[BuoyantC]

I dropped 6# switching from an AL80 to an HP80. It's a nice compact, handy size tank.

 

[rstofer]

As indicated above, dropping 6# is appropriate.

Are you sure you aren't overweighted? If we were to look at the PADI recommendations for starting weight, it would be 24# (10% of body weight) + 3 to 5#. Somewhere around 30#. I'm a little iffy on just what tank they consider with their recommendation but since they are oriented toward resort diving, I would guess the Al 80. So, worst case 24# + 5# - 6# => 23# total with the HP 100. And that would be on the high end of the range.

It sometimes happens that it is difficult to vent all of the air at the surface. As a result, you wind up carrying more weight than necessary. Have your buddy watch your BC as you descend from the surface to see if all of the air is out.

There's another school of thought that says you can make your safety stop just based on wetsuit compression. The normal buoyancy test is to make a stop at 15' with an empty BC and a nearly empty tank. This alternate approach says set yourself eyeball level at the surface with a FULL tank and empty BC. Your tank will lose about 8# (max) by the end of the dive but your wetsuit will lose at least 8# of buoyancy at 15 feet and, in fact, will have at least 8# less buoyancy at the surface after the dive because the cells are still compressed.

The effect of this alternative approach is to lose lead in the amount of the air in the tank - another 8#. It is also true that you will have to swim down the first few feet because you won't sink with a full tank. Still, getting rid of more weight is a good goal to have.

There are those that suggest that this is a more advanced technique. If your dive is not deep enough to compress the suit, you might be somewhat buoyant between 15' and the surface.

You might try to slowly drop weight over a series of dives. You are probably 5# too heavy (at least) plus the potential to drop another 8#. Is 13# worth considering? Not including the tank swap.

Richard

 

[cmburch]

When I went from Al80 to HP100, the drop was about 5lbs for me.

The HP100 is an ideal size for hiking the cliffs of Big Sur, Sonoma and Mendocino. It is the same diameter as an Al80, a little shorter, and about the same empty weight.

A heavier larger capacity tank may be better for boat dives or easy access dives, but a buddy may also need to have a larger tank. The diver with the higher capacity will not use up the air when surfacing with a buddy using an Al80.

I started with a 7mm Farmer John and used ankle weights to get some weight off my belt. I went to a one piece wetsuit and dropped more weight off my belt. I switched from a BC to a stainless steel backplate with STA and dropped more weight from my belt.

I also have two HP130's. One for me and one for my buddy.