Safely diving with heavy tanks

[helodriver87]

A Faber HP100 is almost twice as negative as a 72. That'll knock OP's average weight needed to zero. That's a well balanced rig, but once your head is above water, it gets more negative. I'd rather just float on an SMB than dump my rig, but that's your choice.

 

[Diver-Drex]

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The buoyancy characteristics of AL100s are the same as several of the hp100s. The steels are smaller and significantly lighter. Even the PST hp120, 20% more gas, are lighter and are slightly more negative.

Other than it being your only alternative to a AL80, the AL100 isn’t a good option. Certainly not compared to buying a steel.

 

[helodriver87]

t is NOT trained in OW or AOW either. Not needed.

If all we needed to know was taught in OW and AOW, most of us would be in serious trouble.

 

[helodriver87]

Go nuts. There are some instructions included along with common tank buoyancy info at the bottom. It's designed with salt water in mind. I think you'll find that most steel tank divers are more negative than they think at the surface at the start of a dive.

 

[melanie.]

I honestly didn't know this would be a divisive topic and in appreciate all the input. Im not concerned about getting up, I swim up fully deflated as is, only add air for the safety stop. Im concerned about staying floating if im negative, tired. And then stressed and have a slow boat although ultimately I'd rather pay someone to retrieve my rig from the bottom than be recovered myself I'd still prefer to have neither happen.

With 72s my bottom and air matches, but I'm at ow depth. I want deeper and longer, there's a bunch of wrecks I want but can't get to until I go advanced. I don't want advanced until I go nitrox and have more gas to take advantage of it.

Any concerns about cave sets are non existant because that's not going to happen but wreck penetration is on my list, which I know is similar.

I carry a small smb already, that could help. I have a BIG one, but it's a hose inflate and I don't usually take it.

Im diving palm beach on the 24th, I'll try minimizing as much as I can at the end so I have a solid number to base the math from. Then I'll try I'll try to find somewhere that rents the tanks im after and see if the math plays out.

It's probably something I'll get past in time but even a 2lb safety net would make me feel better.

Although to be fair my thyroid is all out of whack, so I'm probably floatier than usual

It really shouldnt be such a controversial issue... please take a very good look at how almost everyone is agreeing there are options to proceed safely. Choose what works for you.

Good on you for thinking ahead, and realizing that you will outgrow your current tank needs and your air consumption will continue to improve. If you can rent an hp100 do it. Or just buy lol I'm telling you best life ever. I doubled up a set, but still keep some as singles because I would rather dive steel any day than al80s.

And on a last note. Remember you can always ditch a tank instead of your rig if you are at the surface. No reason you wouldnt keep bc and disconnect reg and drop tank. It's cheaper then your life.

Happy diving

 

[chillyinCanada]

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[Colliam7]

I honestly didn't know this would be a divisive topic

It is not necessarily a divisive topic, but it is one about which divers hold some strong opinions, primarily reflecting their personal cylinder preferences. So, you may be seeing some of those preferences emerge in the responses, rather than addressing the specific question you asked.

I interpret your question to be focused on weight at the surface, primarily after a dive, but really at any point after you enter the water.

Im concerned about staying floating if im negative, tired. And then stressed and have a slow boat

although ultimately I'd rather pay someone to retrieve my rig from the bottom than be recovered myself I'd still prefer to have neither happen.

If you move from a ‘neutrally buoyant when empty’ steel 72, to a larger cylinder, can you maintain the ability to float at the surface (even if you have to ditch weights)? And, what cylinder would allow you to do this?

Your question is a reasonable one, and one that many SB users probably ask but are reluctant to post. So, thank you for doing so.

You are currently diving a cylinder that is essentially neutrally buoyant when empty, and 5.4 lbs negatively buoyant when full (2475 psi). I don’t know what you use as your ‘end of dive’ pressure (500 psi? 400 psi? 300 psi?), but I will use 500 psi for the sake of discussion.

At present, if you are weighted for neutral buoyancy at 500 psi, in a rash guard (essentially no positive buoyancy from your exposure suit), then you are starting your dives negatively buoyant by ~4.6 lbs. If you are wearing the 6 lbs of weight you refer to, you can drop weight and become positively buoyant, underwater AND at the surface, if necessary, with a full cylinder. What would it take to put yourself in the same position with a larger cylinder?

Looking at bigger cylinders – also an implied part of your question, and using the Huron Scuba data (SCUBA Cylinder Specifications – Huron Scuba, Snorkel & Adventure Travel Inc. PADI 5 star IDC in Ann Arbor, MI) simply as an arbitrary reference point, you could go to a Luxfer AL100 (neutrally buoyant when empty), or a Catalina AL100 (-0.4 lbs when empty). If you go to a HP100, you could accomplish your goal with a PST E7-100 (-1 lb when empty), or even a PST E7-120 (neutral when empty), but not necessarily with a Faber HP100 (-7.6 lb when empty).

Now, in the case of each of these cylinder options, you will be starting your dive even more negatively buoyant than you are now with your steel 72 and 6lbs of weight (you will have more weight from the additional gas). With the steels (E7-100 or E7-120) you would probably not need to carry quite as much weight (the PST E7-100 is -1 lb when empty vs neutrally buoyant as the steel 72 is) but you would not be impossibly negative either. In the worst case scenario, dropping weight at depth would aid you in getting to the surface if needed, and certainly staying positively buoyant on the surface after ascent. So, given what you have said about your current weighting needs, you do have the option of going to a bigger cylinder (AL or steel), without needing to put yourself in an excessively negatively buoyant configuration.

You also received a number of suggests for supplemental buoyancy (e.g. lift bag, safety sausage), which is a reasonable idea. To those I would add the consideration of moving to a positively buoyant exposure suit (e.g. a full 3mm suit) which would give you the specific benefit you are looking for at the surface.

 

[SWiggs]

In a similar situation as the OP, is there a master list of tanks and buoyancy characteristics? I've seen some here and there but yall are on point with the knowledge. Thank you for that. Good luck bud, we have a similar situation, both weighting and diving goals.

 

[melanie.]

In a similar situation as the OP, is there a master list of tanks and buoyancy characteristics? I've seen some here and there but yall are on point with the knowledge. Thank you for that. Good luck bud, we have a similar situation, both weighting and diving goals.

This is what I use

SCUBA Cylinder Specifications – Huron Scuba, Snorkel & Adventure Travel Inc. PADI 5 star IDC in Ann Arbor, MI

 

[helodriver87]

Huron Scuba Tank Chart. Just Google that. It's not exhaustive, but it's a good starting point. You can also typically search for the specific tank you're interested in. Most online stores include that info in the specs.