Bail Out Bottle Size - Advance Open Water

[Bubbletrubble]

(3) Please state your total non emergency asending SAC from typical diving depth. (how much gas you need/consume in order to make it from the bottom to the surface safely)

This is a strange bit of info to request since, personally speaking, if I carried a bail-out bottle, I'd want it to have enough capacity for an emergency ascent from max depth, taking into consideration a "stressed" SAC rate. I am referring to an emergency ascent as a profile shaped to be 33 ft/min from max depth to surface including any planned deep stops and a safety stop.

SAC is Surface Air Consumption as you all know. SAC can be either rate or amount.

I am looking for AMOUNT - what it takes for you to get from depth to the surface safely.

Yes - the point of this thread is to find out if your bail-out bottle is enough to get you from depth to the surface safely. Hence the toward the spareair.

Units aside, it appears that you're trying to identify divers who have made foolish choices (with respect to bail-out bottle sizing). Or did I misunderstand something?

 

[UaVaj]

What a strange question! What are you going to do with the answers? Learn how to estimate your air consumption and then work out for yourself what size bail-out tank you need.

Reason for putting this thread up is. While gearing for a 110' dive. One of my newer diving buddy (who happens to caryy a spareair) questioned me as to why I carry such a big pony (3.9" diameter x 19.5" length). I try to explain to him that his spareair (1.5cf) was useless in a real emergency (his typical profile is 70'+) and suggest he get something similar. Of course he disregarded my recommendation.

My dive computer offers downloading of dive log onto the computer for analysis. I am able to analyzed my actual air consumption from multiple dives finding out exactly how much air I need to get me safely from depth to the surface. With that information - I purchased a bail-out bottle that meets such requirement.

What is the point of having a bail-out bottle if it is too small for the depth you are diving and is insufficent to actually bail you out safely?

Many divers do not have the luxury of a computer that allows them to download their "asending air comsumption" to help them choose their bail-out bottle.

Hopefully this thread will give them a base line.

 

[UaVaj]

This is a strange bit of info to request since, personally speaking, if I carried a bail-out bottle, I'd want it to have enough capacity for an emergency ascent from max depth, taking into consideration a "stressed" SAC rate.

Units aside, it appears that you're trying to identify divers who have made foolish choices (with respect to bail-out bottle sizing). Or did I misunderstand something?

with safety in mind and avoidance of dcs in mind.
if the bail-out bottle is not even enough for non emergency ascent (when a diver is not stress with a normal sac).
no way is the bail-out bottle enough for emergency ascent (when a diver is stress with a higher sac).

I simply want to point out that the gear (bail-out bottle) should match the duty (depth n sac).

some will take this thread as an attempt in identifing divers who made poor choices. some will take this thread as a warning and in so the will get the proper gear for the type of diving they do.

 

[down4fun]

When I dove open circuit AOW my depths were to 130ft and I would carry 19cuft pony. my sac is 0.4 and I can safely make a no deco ascent on a 19cuft from depth. Have i ever had to bailout due to an emergency...no but I have done so to practice.

On ccr I now dive deeper than the depths listed and carry 2 AL 80's. Again i have never had to bail due to a real emergency but have done bailout drills in class and out. In class I did a bailout drill from 250ft. I used 800# of a AL80 in bottom mix and #800 of deco gas to get to my 20ft stop where I then switched back to ccr. In this controlled setting my usage was 1/3 of what i was carrying this makes me pretty comfortable that in a real emergency i could get out of the water on what i carry. Not to mention that Tony and I do a combination team bailout. We each have enough to get out of the water on our own worst case scenario, but also plan that in a bailout ascent there would be only one of us bailing out and together we have way more than enough to get the other out of the water.

 

[MauiScubaSteve]

I'm pretty sure this thread should at least be in the Advanced Diver Forum, and it probably fits best in the general section of Tech.

 

[k ellis]

My typical in Ocean Depths usually range on the first dive 80 feet and 30 on dive 2. I have gone as deep as 105 feet but still to date I dont carry a pony.

As far as SAC rates I am not sure how you calculate it so I never really gave much thought to it myself.

As far as emergencies go I have not had any real in water emergencies to speak of that I could stop think things through and react in a positive manner. but it may be due to my normal diving being in Fresh water with a 60 foot max as a general rule of thumb also.

 

[peterbj7]

Many divers do not have the luxury of a computer that allows them to download their "asending air comsumption" to help them choose their bail-out bottle

You don't need that, and although I have computers that offer that information I never use it. You can work out your normal gas consumption by swimming at a constant depth for a reasonable period, such as 10 or 15 minutes. Measure tank pressure & time accurately at start and finish, and be sure to swim as you normally do. Knowing the capacity of your tank (tricky for people using the American system of measurement of tank volumes but still possible) you can then work out how much gas you used per minute at that depth, and hence how much you would have used at the surface. Do this several times and you should be able to come up with a reasonably precise measure of your surface-equivalent gas consumption. Then for any subsequent dive, pro-rate that to the depth that dive will be at (actually you'll do a separate calculation for each depth you'll be diving at, which can get quite tedious). Hence you have an estimate of your gas consumption for that later dive. Special allowance is made for deco/safety stop portions of the dive, and any portions where you may expect to be working hard - I'm not going to go into that here.

There are books that describe this process in more detail. It is a grave indictment of dive teaching standards that this isn't part of every dive course beyond the most basic.

 

[Blackwood]

I'm pretty sure this thread ... probably fits best in the general section of Tech.

... why? So the OP will get the answer "I don't use a pony bottle" from pretty much everyone?

As far as SAC rates I am not sure how you calculate it so I never really gave much thought to it myself.

Gas used / (time*averagepressure)

Knowing the capacity of your tank (tricky for people using the American system of measurement of tank volumes but still possible)

Wait, so L/BAR is straightforward but CF/PSI is esoteric?

Comeon. They're just different units which represent the same thing (the volume/pressure relationship).

When someone says "I understand this in metric units but not imperial," or "I understand this in imperial units but not metric," what I hear is "I don't really understand this at all."

 

[peterbj7]

Nothing at all to do with the units employed, but rather WHAT it is that is being measured. The American system measures how much air can be compressed into the tank, and given you know the pressure you have to know at what pressure the manufacturer measured that capacity before you can calculate how much air there is in it at any given time.

The world system measures the actual volume of the tank, the "water volume" if you like. If you know the pressure at any given time it is straightforward without any further information being required to calculate how much gas is in the tank.

Either of these could be measured in metric or imperial measures and there would be no effect on the logic. That's why I chose my words quite carefully, referring not to "American units" but to the "American system of measurement". Mistaking this for a units conflict really does show lack of understanding .

 

[Blackwood]

Technically, the American system represents how much gas will come out if emptied at 1atm.

But to the diver planning gas, volume/pressure is bulletproof.

I just think people sell themselves short when they focus on how something is being measured or quantified rather than gleaning usable information.