100 size tanks?

[brsnow]

Is there some reason why we are not mentioning her name: Opal? I knew her briefly; she was for a time a DM/instructor at Blue Angel.

Wasn’t familiar with her name.

 

[scubadada]

From Dive Gear Express:

From Catalina, an AL100:

 

[brownie]

With planing you can do a lot with an 80
View attachment 710437View attachment 710438View attachment 710439
12 minutes on the San Francisco Maru. Would I prefer a 100, heck yea but …

Did that amazing dive 12 years ago. Just checked my logs: our nitrox was adjusted to 24 or 25%; we enjoyed 15 minutes on the deck of the San Francisco Maru before commencing a lengthy ascent and deco obligation. Stellar dive.

 

[cicopo]

As I mentioned earlier when I'm diving I'm normally photographing too & some of the photos I shoot are shared with an Eagle Ray research group using facial recognition on their spot patterns to monitor their travels. It seems it's illegal to tag them (not sure who's law that is) so this is what they do & that takes getting up above the Ray to get the perfect full wingspan shot. I can burn a lot of air doing that at times while at other times I just happen to be in the right place to drift as I shoot.
Re Opal I have a couple of photos from 2005 when she worked for Troy at Pelagic Ventures Diving

 

[tursiops]

A lot of responses on this thread have assumed that a 100 is a steel. It might be an AL, so all the talk of weight and buoyancy is confusing....and not what was asked.
The OP, paraphrasing, was simply asking why 80 cuft isn't enough gas to do a dive, and has concluded that it is not enough for new divers and photographers. [Apparently he has not experienced much diving outside of drifting along in Cozumel for an hour.]
At an average consumption of 0.5 cuft/min (see Scubadada's graph above) an 80 cuft tank (70 usable cuft) provides about 140 minutes of gas at the surface. For a one-hour dive that would allow an average depth of 2.33 atmospheres, or 45 ft. This calculation does NOT take into account any reserve in case your buddy needs gas from you. THIS is why many divers would like a larger tank, regardless of the buoyancy characteristics.

 

[tursiops]

The aluminum 100 will make you more buoyant as it goes below 1000 psi.

ALL tanks make you more buoyant as you use the air from them! Doesn't matter the tank's material or size.

 

[scubadada]

ALL tanks make you more buoyant as you use the air from them! Doesn't matter the tank's material or size.

The weight of the gas you breathe, for air 0.0765 lb/cu ft. About 5 lbs for an AL 80 3000 to 500 psi.

 

[BRT]

ALL tanks make you more buoyant as you use the air from them! Doesn't matter the tank's material or size.

I agree with you, but big tanks make you more buoyant as you empty them. An AL80 can't swing 6 lbs unless you are overfilling them. A steel 120 can swing 9 lb.

 

[brsnow]

A lot of responses on this thread have assumed that a 100 is a steel. It might be an AL, so all the talk of weight and buoyancy is confusing....and not what was asked.
The OP, paraphrasing, was simply asking why 80 cuft isn't enough gas to do a dive, and has concluded that it is not enough for new divers and photographers. [Apparently he has not experienced much diving outside of drifting along in Cozumel for an hour.]
At an average consumption of 0.5 cuft/min (see Scubadada's graph above) an 80 cuft tank (70 usable cuft) provides about 140 minutes of gas at the surface. For a one-hour dive that would allow an average depth of 2.33 atmospheres, or 45 ft. This calculation does NOT take into account any reserve in case your buddy needs gas from you. THIS is why many divers would like a larger tank, regardless of the buoyancy characteristics.

This is posted in the Cozumel section, but having lived abroad for a good stretch, the Red Sea and Pacific Ocean are where other dives have taken place for me.

 

[tursiops]

I agree with you, but big tanks make you more buoyant as you empty them. An AL80 can't swing 6 lbs unless you are overfilling them. A steel 120 can swing 9 lb.

Sure, the swing is larger with larger tanks. Duh.
But the typical statement is "AL's are terrible because you go positive at the end of the dive" is total BS. It's not the fault of the tank, it is the fault of the weighting at the beginning of the dive. That's what I was responding to.