Dive buddy for air? No thanks.

[rstofer]

Great thought-provoking thread.. thanks everyone.
How many breaths can you get from a 3.0 Spare Air unit if you are OOA at 100 feet and begin a safe ascent (at or slower than 60 ft/min) ?

(Just curious... I would always swim towards a buddy first)

At 100', assuming a SAC rate of 1 cf/min (high for a calm diver, perhaps very low for an OOA diver) you would be consuming 4 cf/min. So, the tank would last less than 45 seconds.

There might be a breathing strategy that would allow you to get to the surface with this tank. I'm not sure it would be 'safe'.

You better hope your buddy if VERY close. It's a long way up...

Richard

 

[String]

Anyone who is 100' away from you is not your buddy. He or she is merely a person you are diving with.

I see a lot of this abroad.

"Wheres his buddy...Oh he's over there...."

A lot of technical courses have a simple skill you remove your reg (and often your mask but that isnt the issue here) and have to swim along a line 10-15m to a buddy where you grap their long hose for air, refit mask then reset.

THAT skill makes you really appreciate just how little distance you want between you and your buddy underwater. It feels a long way. Now imagine you weren't prepared, had empty lungs, tried to breathe and got nothing. Your buddy is 15ft away with his back turned momentarily. You need to get to him and possibly chase him to get attention. That 15ft can seem like 150. You might not make it.

No matter what the visibility if you are going to blindly rely on a buddy for gas he has to be just about within arms reach or at worst 1-2 seconds away at all times. Wander any further than that and you can guarantee the time you need them will be the time they're out of reach.

In a way low vis diving makes this situation a little less bad as they CANT be more than 5-6ft away from you.

 

[String]

At 100', assuming a SAC rate of 1 cf/min (high for a calm diver, perhaps very low for an OOA diver) you would be consuming 4 cf/min. So, the tank would last less than 45 seconds.
Richard

I did this chart a while ago but its relevant here. Its in metric but uses standard rates. It assumes an SAC of 25 litres/minute which is what agencies teach to use for a NORMAL dive planning. Not a stressed rate, normal:

That is how long at that depth various common bailout options will last a dive assuming a 25SLM rate. Yes you'll be ascending but this is a decent base. Also remember when stressed the SAC can easily be double or more so you may want to halve the times listed. If i get bored later i'll do one based on ascent times from depths and how much gas that would use out of each.

 

[MXGratefulDiver]

Research suggests that on average 17 repetitions of air sharing are required to have 90% confidence that students will actually be able to do it.

I suspect the research probably added (or meant to) those three important words.

I've known students who could do something with complete confidence after having seen it demonstrated and practiced it a couple times.

And I've known students who can watch multiple demonstrations and do it dozens of times, and still lack any confidence at all in their ability to do it without supervision.

Most divers are somewhere between those two extremes ...

... Bob (Grateful Diver)

 

[simcoediver]

I see a lot of this abroad.

"Wheres his buddy...Oh he's over there...."

A lot of technical courses have a simple skill you remove your reg (and often your mask but that isnt the issue here) and have to swim along a line 10-15m to a buddy where you grap their long hose for air, refit mask then reset.

THAT skill makes you really appreciate just how little distance you want between you and your buddy underwater. It feels a long way. Now imagine you weren't prepared, had empty lungs, tried to breathe and got nothing. Your buddy is 15ft away with his back turned momentarily. You need to get to him and possibly chase him to get attention. That 15ft can seem like 150. You might not make it.

No matter what the visibility if you are going to blindly rely on a buddy for gas he has to be just about within arms reach or at worst 1-2 seconds away at all times. Wander any further than that and you can guarantee the time you need them will be the time they're out of reach.

In a way low vis diving makes this situation a little less bad as they CANT be more than 5-6ft away from you.

Thats completly true, there is a big difference between having a lung full of air and having no air in your lungs, you might not last 5 seconds before having to suck in water. You wont make it 20 feet.I,ll stick with my pony thanks.

 

[Thalassamania]

I suspect the research probably added (or meant to) those three important words.

I've known students who could do something with complete confidence after having seen it demonstrated and practiced it a couple times.

And I've known students who can watch multiple demonstrations and do it dozens of times, and still lack any confidence at all in their ability to do it without supervision.

Most divers are somewhere between those two extremes ...

... Bob (Grateful Diver)

Actually I should not have said, "on average" that does great violence to the statistics. I should have left it at, "17 repetitions are required to have 90% confidence that the skill will be performed properly."

That means that some people will get it the first time out (very, very few) and that 10% will still not have it down pat after 17 trials.

 

[LeadTurn_SD]

<Hijack>
I would argue the opposite. That BECAUSE of the "excellent viz" there is MORE chance of EFFECTIVE buddy separation. I contend that "excellent viz" is a double-edged sword -- yes, you can see your buddy from 100 feet away -- BUT, that means you might BE 100 feet away and that is a LONG way if you need your buddy or she needs you!

I've found there is more "effective separation" in tropical diving than in the muck here in Puget Sound.

You 100% right of course Peter. I should have said it is easier to maintain contact with a buddy here in Hawaii than in the PNW or NE.

It is human nature to get complacent in conditions that are perceived as "safe". Many people get far more comfortable in a tropical setting than they would in a low viz situation, and separation will increase.

I guess what I really meant was "lost buddy", which I personally define as any distance greater than you could reach them quickly to solve an OOA emergency... I'm uncomfortable with separations any greater than one or two body-lengths, and am happiest with arm-length separations.

Thanks.

 

[NudeDiver]

I did this chart a while ago but its relevant here.

Would you mind sending me that spreadsheet? If not - please PM and I'll send you my e-mail address.

Thanks!
nd

 

[TSandM]

Yes, I think I've posted before about Peter's and my arguments about buddy separation, and the little experiment I did in Maui. I exhaled and swam about 25 feet to Peter, discovering I not only had to swim across but also UP (as I was negative with no air in my lungs) and got his attention and a regulator. I was VERY air hungry by the time I had gas. It was extremely clear to me that I did not want to have to swim that far for air in a real emergency, not at all.

In Puget Sound, a quick waggle of my light will have my buddies instantly at my side with gas. In Maui, I have no effective way to get Peter's attention, other than to touch him, or to hope he happens to glance my way at the right moment. I stay closer to him in clear water than I do in Puget Soup.

 

[bowlofpetunias]

Thanks for an interesting thread. Anything that makes you think is worthwhile and I appreciate the obvious wisdom and experience of a number of those who have posted here. Having read the entire thread I will try not to be repetitive except for point (a &e). A number of points have been very well made already.

(a) Some people are trained and equipped to be solo divers. I don't question their choices the more power to them as long as they really are equipped and trained properly. I suspect if a solo diver came across me in an OOA situation they wouldn't pass by my available air supply. Even if I wasn't their buddy at the beginning of their dive I would be at the end of it! I carry an alternate air source for my buddy, myself and the same dive same ocean diver. I am not a DIR diver but I sure see the sense of having consistency of gear!

(b) When I worked in the ambulance service I dealt with a lot of medical emergencies. Not one of them got up in the morning and thought.... "Today would be a good day to have a heart attack, pre hospital sudden cardiac arrest, spontaneous pneumothorax, (insert emergency of your choice here)." No matter how healthy we may think we are... s*&% happens. Spare air has no value in any of these situations but a buddy may mean the difference between life and death. This may be a bit off topic for some but I just can't separate OOA and other emergencies.

(c) Yes most OOA emergencies are diver errors but not all! I would suggest that divers who are likely to run OOA by lack of attention are just as likely to be careless about their spare air ie, didn't fill it, didn't check it, didn't bring it! Divers that run OOA through poor planning or for want of a better term overconfidence are likely to build that spare air into their dive plan as well with predictable results. Oh yes someone already said Don't try to solve skill/training problems with more equipment!

(d) OOA does happen from equipment failure. Even well serviced equipment can have a HP hose blow..... sounds like an explosion underwater... and boy does the tank empty fast! That is one time you will get your dive buddy's attention quickly with no effort on your part! ! I would suggest this would be a good time for a donation on a long hose.

(e) Peter you are so right. Can't let this one go.

Someone here suggested "shopping for an instructor" what a great idea. Right or wrong I do not want an instructor with 200 dives it is my life and I get to make that choice! I know you can have an instructor with 2000 dives who has poor presentation skills but that instructor is more likely to be able to save their student's life if things go bad. Inexperienced instructors in the pool sessions I can buy.... sorry not in Mother Ocean.... she holds too many surprises! If your daughter was trying to land a dc9 on fire on a icy runway would you really want her to be with someone who has little real life experience?

I am an instructor and very well qualified. I am good at it according to employers evaluations and feedback from clients. If you give me a lesson plan on most things I could probably present it and students not pick up that it wasn't my normal topic. I teach a life skill every day, I teach people how to deal with panic, agitated bystanders and life threatening emergencies. I AM NOT A GOOD/EXPERIENCED ENOUGH DIVER TO TEACH SCUBA! It has nothing to do with instructing skills it has everything to do with the responsibility of bringing every student out of every dive safe, happy, confident in performing skills necessary to survive in an environment we weren't meant to be in!

(f) Instructors should not assess their own students? Who should? In my preferred industry of instruction (basic first aid through to advanced life support courses) I have seen this done in two countries. News flash.... it didn't work in either!

For a while we taught our class then another instructor/assessor had to do the assessment. You went off and often assessed their class.... see a problem already????? If I fail his students and make him look bad .... he fails my students and makes me look bad (justified or not)! He hasn't seen student X for the last number of days and seen them perform everything beautifully only to crash and burn because he was so traumatized by exams/tests in the past that he went into meltdown mode! I have seen that so often.... heck I'd rather have a real bleeding wound to deal with than someone standing over me with a clipboard making notes!

I've also dealt with the "Independent Assessors" hired and paid by the governing body who wrote the classes. Expensive, time consuming and inconsistent. Some liked to be liked... easy markers.... some liked certain instructors... didn't fail their student, some liked certain companies... didn't fail their employees..... some just like the power to fail anyone they could for any excuse they could and they weren't even consistent with themselves in the same class.