Aluminum 80s versus larger steel tanks

[nodakdive]

Personally, I don't dislike big tanks, but I don't really want one for the same reason I don't want to dive with a laser printer, an abacus or a guitar. I don't need them. To the point that more is better, a 120 cubic foot tank would be as useful for most of my diving in Cozumel as a 300 cubic foot tank would be. Would there be a time and a place for a bigger tank for me? Sure, but rarely. I dive a Mosquito and put 4 to 5 hours of bottom time in a day. That suits me just fine.

To be clear, I don't pass judgement on those that want big tanks. For some people, it's the perfect answer for how they want to dive and that's cool. Same with Scubaclub or big resorts down south. You wouldn't ever catch me at one of those places (knock on wood), but it's what some prefer and there's nothing wrong with that.

-Blair

 

[Dave Dillehay]

Dear Nodakdive,


It is not just the added safety of having more air in an emergency, but the buoyancy characteristics are much better. When full the High Pressure 120s (much different than low pressure 120s) are much heavier than an aluminum 80 and getting down with little weight is a snap. Then when empty they are also NEVER positively buoyant like an aluminum 80. Most divers drop 4 lbs of lead.

For the record, they cost me three times as much as aluminum tanks would and we have to be much more careful with them. I wouldn't be doing so if there were not significant advantages.

Dave Dillehay
Aldora Divers

 

[nimoh]

if you strap the extra 4 lbs of lead to the tank, it won't be positive at the end of the dive, and you are still dropping 4 lbs out of your weight belt.

 

[Dave Dillehay]

Perhaps you missed the point that when full the 120 can help you get down very fast, and in our current prone waters that is frequently a benefit.

Dave Dillehay

PS I have never seen a diver with 4 lbs stuck on an aluminum 80

 

[mikeycanuk]

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. I remember a lot of dives on the Brac that were 40mins or less. It seemed before we knew it there was the boat, 35mins into the dive??? I can think of another op who juggled cruise shippers with island tours/snorkels, no way they wanted you out there for longer than necessary. Hmmm now I get why Coz is such a favorite dive destination.

 

[nimoh]

Perhaps you missed the point that when full the 120 can help you get down very fast, and in our current prone waters that is frequently a benefit.

Dave Dillehay

PS I have never seen a diver with 4 lbs stuck on an aluminum 80

well, if you have never seen it then it must not be possible

Need to get down in a hurry? add a few pounds to a weight belt, or better yet, swim down. My point is only that there is nothing wrong with using an AL80 assuming it holds enough gas for the dive. It can be trimmed out in a variety of ways.

 

[Christi]

Christi, you offered. And if the intention of my original question wasn't clear to you, sorry about that. My response post was a bit more detailed as to what I meant by what kind of " profiles are you people diving" to get 90 minute dives. Apparently, it was necessary to spell it out. Your efforts were wasted, perhaps even deliberately obtuse.

Perhaps I'd best ask for average depth, though now I'm asking others.

No - my answer is clearly understood to those who are familiar with Cozumel diving and who are familiar with a multi-level computer dive. Without plugging a computer in or using the antiquated wheel I can't tell you how many minutes were spent at each depth you "required" that I answer. So no, my efforts were not wasted on the majority of the people posting in this thread. And I offered to post some profile samplings after someone asked - and that's exactly what I did - sorry I don't have as much time on my hands as some around here do. I'm sure there are several who appreciate the profiles I posted as an idea of what kind of bt's people can get with 80's here without having a sense of entitlement. And those who are regular divers know what a multi-level computer dive implies - they don't need a depth by depth breakdown. The average depth depends on each site and at what depth the highlights of that particular dive are - each site is profiled to maximize features of the site and to maximize bottom time safely - so no, average depth is not 15 or 20 or 30 feet.

Mike, exactly - do we have to go through that again? YOU like the bigger tanks, and SOMe people like the bigger tanks - but not everybody does and not everybody needs or cares about the extra air. When you're doing the same profiles on AL 80's (because we do all follow the same general profiles for any given dive sites) and are plenty happy getting 60 - 70 minutes (still coming up with a very prudent reserve of 700-1000psi) vs 80 - 90 that's a personal preference - alot of people get cold and bored and don't WANT to do longer dives than that.

GREAT that you and many others like the larger tanks - but not everyone has the same preferences so why are you trying to force yours on to others? Live and let live!

Bigger is not always better!

 

[Lorenzoid]

Glad to see this thread was split off, as this issue interests me. Please excuse me for this relatively novice question, but I didn't see the answer here, at least in so many words.

So in my training I have been led to believe that wetsuit divers should be cautious about using big steel tanks (e.g., 120 cf) because a BC failure could potentially leave one unable to ascend with all that weight strapped to their backs. Now, it occurs to me that while this may be true for the typical cold/temperate regions in which one might want to use a big steel tank plus lots of lead to sink that 7 mm wetsuit, perhaps it is not true for Cozumel diving because one would not be wearing such a thick wetsuit as to need much weight in addition to the tank itself. If I've got it right, a steel 120 is something like 11 lbs. negative when full, so one should have little difficulty ascending from depth with that if a BC failure were to occur at the beginning of a dive, especially if any remaining weight is made ditchable. Do I have it right?

It has only been in the last day since seeing this thread that I have given the issue of steel v. aluminum tanks further thought. Until now, I just accepted it as conventional wisdom that big steel tanks are best left for the drysuit divers.


On the issue of bottom time, I'm all in favor of carrying extra gas for a safety margin. However, I can think of two reasons why this might not be an issue for me in Cozumel. First, since it's drift diving, and I don't have a need to return to any particular point, it seems to me that I could just ascend if there's some sort of emergency--why might I need the gas reserve? Second--and here's the "your mileage may vary"--my wife and I are DONE after an hour in the water in our 3 mm suits. We're getting chilly and itching to get topside by that point. You people with fish genes are welcome to dive your 90 minutes or whatever.

 

[Midge907]

I understand this benefit, and I have a set of HP100 tanks for diving dry for much of the same reason, however how do you handle someone who would be way over weighted with the HP120 you offer? When I show up in Cozumel I dive with 2 lbs, and thats just for the added comfort on the safety stop. This is with a 2/3mm full suit. An HP100 tank nocks 7 lbs off my belt if finishing dive with 800psi, I have a feeling I would be about that much heavier with a HP120 with 500 psi? Just a thought as it has actually been a concern of mine, and a question in my head. I almost booked a dive on the east side with you on my last trip, then decided not to contact you since I was worried about being so overweighted. In reality I could of just put on my 5mm suit that I brought with me for the Cenotes, and would of bridged that gap a little more as its about 6 lbs more bouyant. Just a thought. Was surprised to see when I popped on here that their was a new thread made from this with me as the OP, wasn't expecting to start such a heated subject, but I do think its been a good one.

Dear Nodakdive,


It is not just the added safety of having more air in an emergency, but the buoyancy characteristics are much better. When full the High Pressure 120s (much different than low pressure 120s) are much heavier than an aluminum 80 and getting down with little weight is a snap. Then when empty they are also NEVER positively buoyant like an aluminum 80. Most divers drop 4 lbs of lead.

For the record, they cost me three times as much as aluminum tanks would and we have to be much more careful with them. I wouldn't be doing so if there were not significant advantages.

Dave Dillehay
Aldora Divers

 

[1erCRU]

My only complaint about 120s is the amount of gas still in the tank when surfacing, it's just not right ending even a long dive with 1500psi. :grinjester:

With a finite supply of breathing gas, I'm sure everyone will agree more is better. You really don't know when you might actually need it. I've been in a number of situations where my extra gas has helped to resolve or minimize a problem.

I love not wearing any lead when diving with a 120. Aldora uses the right style of steel tank, distributes the weight along your axis more evenly than the steel HP 12L (120s) used in the French islands, which is about the only other place in the Carib you will commonly encounter steel tanks. Those are short and very negative, concentrating their weight right below your shoulders, a real struggle to keep from rolling.