Just got back from an amazing dive trip to "Wreck Country" USA Pensacola, FL. The wreck diving, as is most diving in Northern FL, was incredible. However, the performance of my personally owned HP80 singles was not. The reasons for purchasing an HP80 firstly, I was convinced these tanks have the same volume or capacity of gas as an AL80. Second, I could have the excellent buoyancy characteristics of the steel tanks at a lower price and drop some lead. Don't get me wrong, the HP80'S are great for training and practice inland in a spring, but for the gas demands and slightly more "stressful" conditions of the deeper wrecks in the Gulf my little HP80'S were woefully inadequate. I've been looking around for LP95 or 108's because I've heard more dive shops prefer filling these and the obvious increase in gas volume. Are there any "old salts" out there that can offer an opinion on the most advantageous single cylinder size and type to use for "real Florida wreck diving" ? All opinions are welcome and appreciated....
Woefully inadequate HP80'S
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"Real Florida wreck diving," can mean a lot of different things. For example, are you talking about a penetration dive at 200' on the Oriskany involving lots of deco, or a non-penetration, dive within NDL limits to 115' on the Avocet? If it's the former, then yes, even a set of doubled up 80s is likely to be insufficient. On the other hand, dives within NDLs are completely doable on a single steel 80 for many people. It really just depends on your own sac rate. It sounds like you just need more gas. As for tanks, I don't think your dive shop is going to "prefer" to fill one tank over the other, as long as the tanks are in hydro/vis. The larger LP tanks are fine, but unless you really need a lot more gas, you might just consider just getting a couple of HP 100s. They are really nice tanks will give you a decent boost in gas over your 80s.
Also, it just occurred to me that @tbone1004 often advocates taking 1 cf of gas per foot of depth you are diving. For a diver with a good SAC and diving in open water within the NDLs, thats probably overkill. But...carrying more gas is always a good thing so I like this rule of thumb.
bamafan
Contributor
If you are bigger I doubt you would notice much difference in wearing a lp95 vs 104. I personally like lp 120's / lp 130's for single tank diving. With cave fills you can do 2 dives on one tank or 1 long dive. Generally with the larger tanks you will be limited by NDL limits vs gas.
Bob DBF
Contributor
80 cuft is 80 cuft, nothing inadequate about the tank itself. Now if it not enough gas for your dive plan, that is another issue altogether. I have tanks from 72's to 120's I just pick the one that works for the dive.
If you can handle the tank, a 120 works well for dives plans that needs a lot of gas, or ones that don't thus giving you a larger reserve, or a second shallower dive. I dive wet in cold water, so I use a smaller tank because I can warm back up on the SI. With a 120 I can get too cold to warm up properly during the SI, and have to cut short the second because I get too cold.
Bob
If you can handle the tank, a 120 works well for dives plans that needs a lot of gas, or ones that don't thus giving you a larger reserve, or a second shallower dive. I dive wet in cold water, so I use a smaller tank because I can warm back up on the SI. With a 120 I can get too cold to warm up properly during the SI, and have to cut short the second because I get too cold.
Bob
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Sometimes the fill you get makes a difference. I frequently dive in SE Florida and fills for AL80s average about 3200 psi, or a bit over 82 cf of gas. If a HP80 was filled to just 3200 psi, you would only have a little over 74 cf of gas. A fill to 3442 psi will give you the entire 80 cf
Our club has a bunch of steel 10l cylinders. These are similar to your steel 80cuft cylinder. Mostly they get used by small women or in the pool. They are easier to handle and with a low SAC (typical of small women) they are ok. Care must be taken if the buddy has a moderate SAC.
However for more normal users of gas they are not so useful. A 12 (100) or a 15 (120) is much more common.
2airishuman
Contributor
They do. In fact, they typically hold a little more, 80 cf vs. 77 cf on an AL80.
Sure. I'm assuming that you're asking about singles on recreational (no-deco) dives.
New cylinders --> Choose an HP100, HP117, HP120, or HP130. I would guess based on your post that HP100 will still be too small, see "capacity notes" below. Of these, HP100 and HP120 are 7.25" diameter, same as AL80s and HP80s, while the others are 8" diameter. HP120s are long and work out well for fairly tall people, if you are not especially tall, you will prefer an HP117 which will give you the same capacity in a cylinder with less length.
Used cylinders --> Also consider the LP95s or LP108s you mention if you can get them at a good price for their condition.
In addition, there are HP149s out there (new and used) and LP120s (used only), which are widely considered too large and too heavy for routine use, but which a handful of relatively large, athletic divers prefer. They are 8" diameter and the same length as HP120s.
Capacity notes
It would help to know your SAC or at least your approximate height and weight.
In very general terms, for air dives within recreational limits, an HP100 will provide sufficient gas and substantial reserves for most people. For shallow dives, most people can easily get an hour out of an HP100. For deeper dives, following the usual pattern of a two-tank dive with an hour surface interval, NDLs will be limiting on the second dive, for most people and most profiles.
If you are diving nitrox then gas capacity, not NDLs, will limit the duration of deeper dives, especially if you are only making 1-2 dives a day, and larger cylinders will allow you to dive longer.
Among HP117, HP120, and HP130 cylinders, the difference in capacity isn't especially significant, and you would want to choose cylinders that fit your body shape and are practical for you to handle topside.
Stages and doubles
Even on a no-deco dive, some people bring a stage bottle. There are various strategies for using it. You can use it as a reserve and reduce the amount of reserve (and therefore increase the gas available for the planned portion of your dive) in your back gas. You can also plan to use the stage bottle towards the beginning of the dive and switch to your back gas as appropriate. Usually an AL40 or AL80 is used for this purpose.
Some people (including me) use doubles for certain no-deco dives, for reasons of capacity, redundancy, or both.
Thanks RyanT
I should have been more specific yes I was referring to non-penetration dives on singles within NDL'S. Much like the Avocet and like the Oriskany, even PeteTide. MOD@95'fsw to 130'fsw. It could be I'm a complete airhog and just need more gas. I do a lot of training and practice in a high altitude natural spring which doesn't even touch the stress factors involved with doing a boat dive 20 miles offshore in the Gulf. I hope to very soon be in a situation where I'll be able dive FL wrecks on a weekly basis.Thanks for taking the time to reply!
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