Any “skinny” AL 100 manufacturers?

[DXHI]

Right now I’m diving with 14 lbs of lead. When I was in Belize and using my wetsuits I had to add an extra 4lbs

 

[rongoodman]

The 100’s have less buoyancy swing

Gas weighs just the same no matter what the tank is made of.

 

[Belzelbub]

We do a lot of spearfishing on scuba. Started with steel 100 and now use steel 120. One of my buddies is using steel 150!
The 100’s have less buoyancy swing and you don’t have to carry as much lead. What’s a negative on why to not use a steel 100?

To be accurate, the swing is actually greater with a steel 100 than an AL80.
Per this chart: SCUBA Cylinder Specifications – Huron Scuba, Snorkel & Adventure Travel Inc. PADI 5 star IDC in Ann Arbor, MI (Chart is older so doesn't have some of the newer tanks, but the idea is the same.)
AL 80s have a swing of around 5.8lbs.
Steel 100s have a swing of around 7.5 lbs.

The buoyancy swing comes from the weight of the gas. More gas equals more weight. The difference, however is that the AL 80s become positive as they are empty. Steels remain negative throughout. Though in most cases, we are only talking a pound or two.

Since steels remain negative, this means that you can carry a few pounds less weight.

I’m sure there are a lot of arguments on either side of the fence … but the biggest one they push is that in a pure SHTF moment every bit of positive buoyancy helps at the surface

That has to be one of the most ridiculous arguments I've heard of. If they are providing tanks free of charge, then they can have you using whatever they want. If using your own tanks, buy what makes sense for you.

Proof the Consumption hasn’t changed much since the first few drops… even on nice leisurely dives vs quick bounces with wrestling fish
View attachment 724986

Interesting. Seems your best SAC was on your first few dives, then it peaked and has been slowly reducing, but now appears to be pretty much flat.

How long are your dives typically?

 

[DXHI]

At 60 foot depth I can hit 40 minutes and that is stretching It …. A lot .. last “play dive” after I made my initial survey of the wreck I stayed in one area just trying to find nudibrsnchs or something else cool … and also really to see if I could stay down til I hit the NDL.. and that was 40 min

At 120 ..15 minutes

 

[lowwall]

I’m sure there are a lot of arguments on either side of the fence … but the biggest one they push is that in a pure SHTF moment every bit of positive buoyancy helps at the surface

That is pure idiocy. If you are weighted correctly, you will be exactly as buoyant at the surface no matter what tank you are using.

In a SHTF situation, you add air to the BC, wrap your inflated SMB around you and/or dump weights. This will give you 40-80 pounds of lift. Do they seriously think the 3 pounds of buoyancy you get with an empty AL tank is going to make a difference?

Get the HP100. If they are too stupid to let you dive with it, you are far better off somewhere else. Dumb is dangerous.

 

[boulderjohn]

The buoyancy swing comes from the weight of the gas. More gas equals more weight. The difference, however is that the AL 80s become positive as they are empty. Steels remain negative throughout. Though in most cases, we are only talking a pound or two.

Whether a tank is positive or negative before or after a dive makes no difference whatsoever. The buoyancy swing, which is caused solely by the loss of the weight of the gas, is all that matters.

Whether a tank is positive or negative at the end of the dive would only matter if the tank was the only thing determining buoyancy. It isn't. Your buoyancy is determined by your entire package--the tank, you, your thermal protection, your gear, and, of course, the lead you carry (if any). Because a steel tank has greater weight per volume than an aluminum tank, with an aluminum tank you need to carry more lead to make up for the weight difference. That is true throughout the dive.

In summary, if your total package weighs 260 pounds at the beginning of a dive and you use 6 pounds of air during the dive, your total package will weigh 254 pounds at the end of the dive, no matter what kind of tank you use. With an aluminum tank, that final weight will include the extra lead you needed to carry.

 

[Belzelbub]

In a SHTF situation, you add air to the BC, wrap your inflated SMB around you and/or dump weights. This will give you 40-80 pounds of lift. Do they seriously think the 3 pounds of buoyancy you get with an empty AL tank is going to make a difference?

I only came up with one possible reason for the buoyant AL tank being a benefit in a SHTF situation. And, it's really a stretch to get there. It would only come into play if the diver lost buoyancy and had a nearly empty tank. In this case, at the surface, dumping the weights would give a little buoyancy. As you said, it's only a couple pounds so not much, plus, that couple pounds is on the diver's back, so probably not the best spot.

Whether a tank is positive or negative before or after a dive makes no difference whatsoever. The buoyancy swing, which is caused solely by the loss of the weight of the gas, is all that matters.

Not sure if you are agreeing with me or not, I think you are because that's essentially what I said. The buoyancy swing comes from the amount of gas. Bigger tanks mean more buoyancy swing because they start with more gas. The positive buoyancy of an empty AL tank only really means that the diver needs to carry more weight IN their weight belt or integrated pockets.

 

[crofrog]

I'd put forward your divemaster, may not be a master of diving.

 

[Robert H. Diver]

I’m sure there are a lot of arguments on either side of the fence … but the biggest one they push is that in a pure SHTF moment every bit of positive buoyancy helps at the surface

If you are weighted properly it shouldn’t matter.

 

[boulderjohn]

I only came up with one possible reason for the buoyant AL tank being a benefit in a SHTF situation. And, it's really a stretch to get there. It would only come into play if the diver lost buoyancy and had a nearly empty tank. In this case, at the surface, dumping the weights would give a little buoyancy. As you said, it's only a couple pounds so not much, plus, that couple pounds is on the diver's back, so probably not the best spot.


Not sure if you are agreeing with me or not, I think you are because that's essentially what I said. The buoyancy swing comes from the amount of gas. Bigger tanks mean more buoyancy swing because they start with more gas. The positive buoyancy of an empty AL tank only really means that the diver needs to carry more weight IN their weight belt or integrated pockets.

This is what you wrote and to which I was responding:

"The difference, however is that the AL 80s become positive as they are empty. Steels remain negative throughout. Though in most cases, we are only talking a pound or two."​

As I wrote, that does not matter.