Aluminum 80s versus larger steel tanks

[drbill]

When I used HP120s I could do 2-3 nice dives off a single fill (which was charged at the same rate as filling an Al 80) or I could do one rather deep (up to 200 ft) dive with it. Unfortunately steel and my local diving practices didn't get along very well so I now dive neutral buoyancy Al 80s which can still give me two decent (40 min) dives or one nice long one (75-90 min) at reasonably shallow depths.

 

[old gaffer]

This question is for Dave D. If everyone surfaces together you must have several divers surfacing with quite a bit of that 120 remaining. To truly get full benefit of diving an op that uses 120's sending divers up individually to me makes more sense. If I had better sac rates then everyone else and came up with the group with a bunch of air remaining I might as well dive with an op that uses al80's and sends divers up individually.

tom

 

[Pelagicsal]

It has been implied that the ops that use steel tanks give them to everyone. And that women get steel 100s, regardless of their SAC (which is NOT always better than men.)

Judging from my experience, initially men are given 120s and women 100s. If either needs or wishes to change to the other size tank, that is managed as soon as possible. Certainly SAC rate is a determining factor in tank selection.

 

[drrich2]

I don't really understand the hype with the whole 120cf tanks, to me they are a crutch for inexperienced divers in a place where 80cf tanks will give you 70min bottom times. Just my .02

If that's true, I don't understand why no one ever tells a petite woman that 80 cf AL's are a crutch for inexperienced small divers who ought to get 70 min. bottom times out of an AL 63.

 

[jd950]

Amazing to see a multi-page argument about tank capacities. Its' nice to have options and an op than can offer higher-cap tanks offers an option. I don't really care if it is a crutch for someone. Dive vacations are expensive and I imagine everyone wants to maximize their time in the water. I am not going to begrudge dive time to someone because they aren't "skilled" at gas management or if their body size or whatever makes them suck down air faster. For me, I like larger tanks for four reasons:

1. I don't dive enough and on most any dive trip, I suck down my air pretty fast on the first couple of dives. Then I get settled in and my SAC improves. It's nice to have the extra gas on that first day.

2. I take pictures. That means I sometimes fight the current, sometimes need to spend a bit more time a slightly greater depth than some in the group. I use breathing to adjust my position in the water a lot, and sometimes have to get into weird positions to get a shot without touching anything. All of those things cause an increase in gas consumption. I have never measured the difference but I know my air consumption when taking a lot of photos is significantly worse than when I am not. A bigger tank lets me still have a long dive and if I am using a larger tank than others, then I am unlikely to affect anyone else's dive time with my own gas consumption.

3. In some cases the dive is over when the first person in a group runs low on air. I am rarely the first one to run low, and I appreciate it if whoever has the worst gas consumption in the group is using the biggest tank possible.

4. Sometimes crap happens. I have been on dives where the DM had us spend what I felt was an unreasonable time fighting current while he tried to spear a lionfish. I have been on dives where someone had a problem and the DM had everyone hang out while he tried to fix a problem or some buddy team ascended to get picked up before the rest of us could resume the dive. I have been on dives where we didn't get dropped in the right spot and had to travel some distance to get to where we wanted to start the dive. Having extra air just serves to make any of those kinds of things less important.

Finally, even if everyone is using big tanks, the dive is likely to be of respectable length even if some folks are gas hogs. Maybe some folks will come up with a lot of air, but hopefully it is still a decent length dive. I have been on dives where everyone had to descend and ascend as a group and the first person to run low on an AL80 ran low after about 30-40 minutes. That just sucks when you have over half your tank left and you have only five days of diving before you have to go home.

 

[Mike]

My first question was what profiles are you people doing in order to get→ 90 ← minute dives. Profiles provided had total depths of 70-75.

Second question was average depth instead of "profile". You seem to have plenty of time to write insults and attempts at condescension but not the answer I've asked for. So be it. I shall draw my own conclusions in that regard.

As it happens, I dive with a computer, the vast majority of my dives are multi-level, and while I'm familiar with Cozumel diving it has been years since I've been there.

If you are only speaking to regulars that dive in Cozumel, so be it.

Let's say I didn't bother to ask in the first place, shall we. I'd prefer not to play your childish game any further.

There isn't anybody in Cozumel routinely doing 90 minute dives with AL 80's on a typical Cozumel dive site & profile, period. Nada. The average dive in Cozumel is well under 60 minutes.

And the major resistance to extending dive times is right here:

I would love to see the HP tanks in other Caribbean locals. However I just made the realization that a lot of dive ops don't want to be out that long on the water.

 

[Skittl1321]

The average dive in Cozumel is well under 60 minutes.

Well under?
I guess I find this hard to believe, because I was a freaked out newbie (seriously- day 1, the DM stopped her briefing to make sure I was okay) on my first ocean dives, and over 11 dives, my average was 53 minutes. Yes- under 60; but not well under. Some of the other divers would be down for 20 or minutes longer than I was. Even if you take the 76 minutes at Columbia Shallows out of the equation, my average time was 51 minutes.

So, maybe I'm average and not an outlier- but I have to think if I can take "freaked out" out of the equation, the times would improve, so I would think my dive times are lower than average, and they are already getting pretty close to an hour. I would have guessed the average Cozumel dive (taking into account deeper and shallower dives) is 60 minutes. But maybe not since some ops might just set a 45 minute time limit to fit their schedule.

I do think the 90 minute dives on AL80s are rare, and shallow though.

 

[Mike]

Well under?

Well under, just under, a little, a lot, short of, less than... substitute whichever description you would like, don't stress over it.

---------- Post added May 9th, 2014 at 02:14 PM ----------

I do think the 90 minute dives on AL80s are rare, and shallow though.

just rare? quite rare, really rare, rarely rare, sometimes rare, a little rare, majorly rare, somewhat rare, medium rare....

 

[cvchief]

There isn't anybody in Cozumel routinely doing 90 minute dives with AL 80's on a typical Cozumel dive site & profile, period. Nada. The average dive in Cozumel is well under 60 minutes.

Under 60 minutes? I call BS:

 

[Mike]

Under 60 minutes? I call BS:

View attachment 183746

Whatever.

When you compile all dives for every dive operation in Cozumel and post the results let me know, until then I'm happy for your dive times.