Woefully inadequate HP80'S

[Chilly_Diver]

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.

I think an LP85 would be a great choice. With a normal fill, you are guaranteed to get 85 cuft. With a Florida fill, you are looking at almost as much gas as the aforementioned cylinders in a much lighter and smaller package.

 

[dvrdv]

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 2airishuman I really appreciate your informative reply I'll definitely take these things into consideration
Thanks again!

 

[dvrdv]

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

Makes a lot of sense Bob I appreciate it!

 

[dvrdv]

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.

I think I'm liking being limited by NDL'S and not gas supply better. What's that old saying "It's better to have and not need than to need and not have......?
Thank you sir

 

[RyanT]

I hope to very soon be in a situation where I'll be able dive FL wrecks on a weekly basis.

Very jealous!!! I dove the Gulf out of Pensacola for many years and I miss it a lot. I would caution on the LP 85. It's a great tank and indeed will hold a lot of gas if you get an overfill. Unless you know your shop will overfill it though, you could be stuck with a tank holding only marginally more gas than the HP 80. The HP 100s are not noticeably larger than the LP 85s. I've had no trouble getting 3500 psi fills in Pensacola on HP tanks. Of course the HP 117s & 120s will hold even more.

 

[dvrdv]

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.

Ouch! lol
yeah one my main reasons to purchase the hp80 was the price. Lesson learned!
thank you sir!

 

[tbone1004]

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.

that I do. Definitely not my idea, but a good rule of thumb for making sure you are going to be OK when single tank diving

 

[BRT]

Only if they're filled to their rated pressure. Lots of shops won't do it, they think it will blow up or something. Also the highest rated fill pressure drops off after a few years due to supposed weakening of the tank.

Fill pressure drops off on HP80's? This is new!

 

[Bob DBF]

yeah one my main reasons to purchase the hp80 was the price. Lesson learned!

That's the reason I pick up most of my tanks, better to have too many than not enough, and I haven't lost money, so far, when I do sell. Can't have too many tanks, up to a point, and I've almost reached mine. There are a couple of tanks that I would pick up at the right price, because of like rather than need.

I keep my 5 favorites in hydro, and the rest wander in and out of hydro as I need them.



Bob

 

[tursiops]

Fill pressure drops off on HP80's? This is new!

More likely wrong than new....