Nathan Doty:
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.
Nathan Doty:
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.