Spare Air

[Cacia]

yea....but being the rocket scientist that I am, I avoid spare air from my ex.

yea, a little bored, my house is spotless.

I think I will put my spare air next to the fire estinguisher.

yes, I have learned a lot here. Everytime I see some rant against internet learning, I feel sorry for the person that they cannot discern who to listen to about what....must make life very difficult.

Lamont has definetly helped me understand how various compartments off gas in the context of ambient pressure, etc, etc. I think we should award him with his own forum where he could translate mathematical models into "where the rubber hits the road" and how this applies to your dive!

The only thing I disagree with him on, is I don't gobble up the DAN data the way he does. The stats they present are not confirmed in my years of diving and observing accidents and deaths in the anecdotal sense. Fairly egotistical to say this and I certainly don't have any better numbers...but I think the numbers they use are distorted. Several thoughts come to mind...One is that most accidents are multi-causal and multiple contributing factors don't translate well into the stats they use. It could be that we are looking at older data and the diving demographic has changed so much that poor fitness plays a bigger role than the data reflects since it was collected on younger divers. ?? Seems the aging baby boomer population and the disposable income they have to travel and buy equipment is bound to create a shift of some sort.

Worrying about spare air strikes me like the guy who smokes two packs a day concerned about his flight. I wish there was more emphasis on teaching divers how to prioritize and discern the risks they face and form a hierarchy of problem solving in their plans. I get frustrated hearing so much discussion about sac rates for example, and no discussion about current, ocean conditions etc. Sac rate and gas planning if you can't assess your probable exertion level, is a false security blanket, in my world.

The beauty of this board is that I can take a long view of a given issue and get advice and insight from a wide variety of divers, and ultimately be better equipped to make my own decisions. Of course, taking a snapshot in a given thread, if you take every post literally might be a mistake. I don't see many people doing that though. Most of the people on here a lot are processing and reflecting.

 

[BigTuna]

To the original question (if it this hasn't been done already in this looong thread)...

I calculated how much gas you need for a direct ascent to the surface at 30 fpm on a full SpareAir bottle. The answer depends on what you assume your SAC rate (surface air consumption rate--in cubic feet per minute) to be.

If I assume you are stressed and make the conventional assumption of 1.0 for your stressed SAC rate, then you could ascend from 54 feet with Spare Air's 3 cf of air (to be cautious, call it 50 feet). If I assume a more relaxed SAC rate of 0.8, you could ascend from 63 feet (call it 60).

If you were to start at 130 feet and make a 30 fpm ascent with a 3 min safety stop, you'd need 16 cf if you're stressed, way beyond what's in a SpareAir bottle.

You can extend these calculations to account for "sorting out time," deep stops, gas required at the surface, and optimistic assumptions about how much gas is in the cylinder. This lets you home in on how big your bailout cylinder needs to be for your kind of diving. For my own set of assumptions, it works out to 19 cf for dives to 80 feet, and 30 cf from there to 130 feet.

 

[TheRedHead]

yes, I have learned a lot here. Everytime I see some rant against internet learning, I feel sorry for the person that they cannot discern who to listen to about what....must make life very difficult.

Actually, I was thinking about classes more than the internet. I think Lamont mentioned Tech 1, but it could be any class that has a large component of stress where you have an instructor who can make a CF of a simple OOA drill. It's really more like learning the hard way in a controlled environment. You don't forget the lessons and it hits home as to why something should be done one way instead of another.

 

[lamont]

Actually, I was thinking about classes more than the internet. I think Lamont mentioned Tech 1, but it could be any class that has a large component of stress where you have an instructor who can make a CF of a simple OOA drill. It's really more like learning the hard way in a controlled environment. You don't forget the lessons and it hits home as to why something should be done one way instead of another.

The only unique thing about Tech 1 is that the instructors are trained to take a group of divers and stress the team until it breaks, and if the team breaks before the standards are reached the team fails. They'll teach you stuff during the class, but mostly you either bring a level of basic competency to the class or you don't pass. They will never have you demonstrate some skills, pat you on the back about how good of a diver you are, and then give you a card. I can't say the same thing consistenty for any other class or certifying agency, but there's individual instructors out there who will do the same thing.

Tech 1 instructors will not overly harass you, they try to make situations realistic (helping the occasional line to become tanged in a manifold or whatever -- usually they don't have to though), and mostly they just step back and exploit a weakness here or there to generate clusters. If you don't open any windows for them to exploit, the class gets a lot more routine. Going into it, most recreational divers really can't handle more than one thing going wrong at a time, and usually they do things which tends to increase the chances of generating multiple failures.

GUE does not own a patent on the process, but they do consistently train their instructors to teach this way.

 

[Rev. Blade]

Is a Spare Air better than a pony rig? Not in my opinion... if you have a pony rig along. My point is, that some people feel they should have a backup gas supply, but leave it behind, because it's a bother. My SA is in a pocket sewn to my BC. If I'm diving without it, I still have a neon yellow pocket sewn to my BC saying, "I left my Spare Air on the surface." I suspect there are some people who have posted against a SA that do not dive with an independent gas system (on every dive) ...perhaps even to include diving without a buddy.

If all the agencies used to teach ascent rates of 60 feet per second, does it now mean that you are guarenteed to died a horrible death if you try it now that they all teach 30 fpm (at least near the surface)? I'd guess there were a number of incidents at 60 fpm, but that does not mean you'd be safer to stay under water (without air) than to ascend quickly.

I've seen a couple people suggest that if you carry a spare air, you could run out of air twice. I disagree strongly. You might run out of air once, but it will be several seconds after the catastophe hit. If you run out of gas on your SA, you better already be working on your CESA! It's only 3 feet of air! It's not even as much gas as a J-valve held back. Nobody smart plans to make an ascent on a spare air.

I carry one of only 3 spare airs that I've seen in the water. The other two were owned by SCUBA instructors.

To use an analogy, a spare air is a bit like a motorcycle helmet. Does a helmet protect a motorcyclist? Certainly not to the point that they don't get hurt. If you want to be almost injury free in a motorcycle accident, be in the car they hit (or in the car that hits them). Lots of motorcyclists say that a helmet encourages reckless riding. To some degree, it's true. So, do motorcycle helmets increase overall injuries, but reduce the head trauma in any given accident? Perhaps yes. My helmet argument may not have any real bearing, but I certainly don't agree that no safety measure is better than a weak one.

Other people have compared a spare air to a BB gun in a bear attack. I'd equate it to a .22 pistol. Still not the device for hunting bears, but if you were out hiking, and a bear attacked, would you rather have a .22 or your fingers? Can you make a bear angrier with a .22? Obviously! Can you kill a bear with a .22? Yes. People are easier to kill than bears, but here's an interesting statistic... more people have died from .22 caliber injuries than any other single calliber... including wartime firearm deaths! On one hand, that reinforces the arguments against the spare air.... Idiots think a .22 is not dangerous, so they are not careful with them. That's a receipe for disaster. Similarly, if you believe a spare air will save you from planning your dive, you could end up dead.

People give me a hard time about always having a flashlight with me. (Above and below water.) When it's suddenly dark, they all want me to help. If I'm underwater, and suddenly had no air in my main tank, I'd sure like to know I had 15 - 30 seconds to get to more air. I try to treat my 3 cu. feet of air as no air, but if the fat's in the fire, I'll be happy to have that, instead of your pony that's on the boat (or home) because it wasn't going to be needed for this dive.

 

[Kaufdropp]

Does anyone think it is a bad idea to buy a spare air from leisurepro?

 

[TheRedHead]

Does anyone think it is a bad idea to buy a spare air from leisurepro?

Nice troll for only 15 posts.

 

[loosebits]

Nice troll for only 15 posts.

How about this: Why doesn't PADI offer a spare air speciality?

 

[TheRedHead]

How about this: Why doesn't PADI offer a spare air speciality?

Funny you should mention that. I was reading the UK divernet forums yesterday and they were calling for pony bottle training to be introduced in BOW class.

 

[JungleJoe]

My instructor said point blank, spare air = bad news.. pony's are the only method to go. I see the points of having something vs nothing. but i'll stick with clipping on my pony when I dive in situations that warrant it. Or if I am diving with someone else, then the pony comes along, since I have no control over how they breath and what sort of trouble they could cause.

Spare Air's get good money on ebay, sell yers and get a nice pony, then a nice used reg.