Spare Air

[RJP]

Reminds me of a recent thread about what type of writing instruments people used to make notes underwater. Me? I use one of these...

They are made from a cellulo-organic material which is known for its depth compensating properties. Specially designed, these precision writing instruments are of hexagonal cross-section in order to accommodate divers wearing a range of gloves. The active ingredient in the instrument is a polymorph of elemental carbon, specially imported from the country of New Hampshire. Each instrument is coated with a patented substance known as "yellow paint" to allow the instrument to double as a signaling device - either at depth or at the surface. You'll notice that image I've posted above is a purpose-built piece of tech gear; easily identified by the lack of several failure points that are commonly seen in recreation pencils:

Plus, you'll also notice the model I use has no wireless transmitter, no switches to fail, etc.

Now, you may say "But Ray, isn't a pencil a life support system?" And of course you'd be right to ask that question. You'd sound like a bit of an alarmist nut, but you'd be right. Either way, I do worry about redundancy for anything that holds my life in its hands (if it had hands) so I always carry an appropriate backup...

Some folks may opt to carry a SparePencil^TM...

but I believe that something that was originally designed to carry just enough graphite to enable helicopter pilots to write "Oh sh-t!" before drowning has no place in tec diving! That's why in cases where you REALLY need redundancy many recreational divers opt to sling one of THESE as backup...

On the other hand, hard-core tec people like myself will often "dive doubles"...

which are perfect as this configuration allows you to completely isolate one pencil in the event of a "catastrophic" failure...

:shocked2:

 

[goonsquad]

Do you really think you are the first person to show up on this board looking for detailed information on the Spare Air? Are you looking for some kind of credit for this unique degree of inquisitiveness?

The Spare Air has been discussed endlessly and in excruciating detail. All you have to do is read and learn.



As to the rest of your post..sorry but you even know the proper questions to ask. Vast ignorance is showing.

Just keep things basic for a while.

Actually, all i am asking for is useful information. Some have been more than happy to reply with useful information. Others, well not so much...
I don't know about others, but when I am ignorant of something I ask questions. You can call me ignorant all you want, I completely agree. If I wasn't ignorant and I had the answers I wouldn't have asked the question.

 

[LeadTurn_SD]

RJP,

I hope you own stock in keyboard and computer monitor companies.... I just sprayed coffee on both after reading your post, and you owe me a replacement dude.

[grumbling while I look for paper towels]



Best wishes.

 

[Tanked]

:caveman:

 

[friscuba]

It doesn't require that much more math actually but... assuming you are at your ndl and you run out of gas and ascend at the prescribed rate of 30 ft/min (wouldn't be great to just rush to the surface) At 60 ft(2.81 ATA)with the 3 or 6 cuft spare air:

So a minute at depth to figure out your problem, signal your buddy, get situated and start ascending you need 2.81 cuft of gas (remember you're stressed out 1 cuft SAC).

To go from 60ft to 15 ft a distance of 45 ft, which will take you 1:30. You need 3.18 cuft of gas.

For your 3 minute saftey stop you need 4.36 cuft of gas (5 cuft of gas or so to get to the surface).

So... you need 10.99 or 11 cuft of gas to get to the surface, assuming you follow the rules correctly. If using the 3cuft spare air you drown as well as the 6 cuft. Thus my comment that it's nothing more than a CESA aide.

Oh, and in an ideal world friscuba, people would plan their dives properly, and follow safe buddy practices, then I would agree backup air sources wouldn't be needed.

To play a little devil's advocate.... the example you gave just stated you'd need a certain amount of air assuming "you are at your ndl and you run out of gas". Is it a coincidence you weren't paying attention to your NDL and just happened to run out of air at the minute you hit it, or was the dive planned to max out your NDL time? I would think use of an emergency air soruce would only occurr due to accident, and be highly unlikely to occur right at the moment you max your NDL. I dove with a guy who always planned on running out of air at 15-20 feet and doing a CESA every dive (I wasn't aware of his plan, found out when I saw him swimming to the surface), I've heard of others that drain their tank and use their pony every dive, either seems like a bad move to me. In an unplanned emergency I'm good with making it to the surface, air to spare would be nice, but planning to max out my NDL just isn't in the plan for me.

 

[elmer fudd]

It doesn't require that much more math actually but... assuming you are at your ndl and you run out of gas and ascend at the prescribed rate of 30 ft/min (wouldn't be great to just rush to the surface) At 60 ft(2.81 ATA)with the 3 or 6 cuft spare air:

So a minute at depth to figure out your problem, signal your buddy, get situated and start ascending you need 2.81 cuft of gas (remember you're stressed out 1 cuft SAC).

To go from 60ft to 15 ft a distance of 45 ft, which will take you 1:30. You need 3.18 cuft of gas.

For your 3 minute saftey stop you need 4.36 cuft of gas (5 cuft of gas or so to get to the surface).

So... you need 10.99 or 11 cuft of gas to get to the surface, assuming you follow the rules correctly. If using the 3cuft spare air you drown as well as the 6 cuft. Thus my comment that it's nothing more than a CESA aide.

Oh, and in an ideal world friscuba, people would plan their dives properly, and follow safe buddy practices, then I would agree backup air sources wouldn't be needed.

Of course ascending at the proper rate with all stops included is best, but it seems to me that you're overlooking the fact that ascending 60' in 60 seconds beats the bejesus out of a sprint to the surface on whatever air you may or may not have in your lungs and hoping you make it there alive.

If you were to end up bent after a too quick ascent on a SpareAir, then just imagine how much more bent you'd be after a balls to the wall CESA.

 

[BarrelRoll]

I actually LOVED my Spare Air until I had my BP/W pierced by a pointed dive knife.

 

[UCFKnightDiver]

Thanks Dr. Wu, but as I read through the posts (here and in the searched threads) all I find is anecdotal evidence and piss poor attitudes to back up the reasons people actually dislike SA.

Other people seem to see it as a tool with limited use. That I can completely accept. Piss poor attitudes toward something just comes across as piss poor attitude.

I'm not looking for an answer like "its great, go get one" to justify something. I was looking for a justified stance as to why a rec. diver not doing anything complex or overly deep would not benefit from having a limited use tool that could get them to the surface. I would think a case of the bends would be better than a case of the drowns...Perhaps you're a dive god who will never have a problem or be separated from their dive buddy, but things happen. Sometimes you can plan a dive but not dive the plan.

Again, thanks for your insightful post.

Personally I'd rather have neither case...

 

[UCFKnightDiver]

Reminds me of a recent thread about what type of writing instruments people used to make notes underwater. Me? I use one of these...

They are made from a cellulo-organic material which is known for its depth compensating properties. Specially designed, these precision writing instruments are of hexagonal cross-section in order to accommodate divers wearing a range of gloves. The active ingredient in the instrument is a polymorph of elemental carbon, specially imported from the country of New Hampshire. Each instrument is coated with a patented substance known as "yellow paint" to allow the instrument to double as a signaling device - either at depth or at the surface. You'll notice that image I've posted above is a purpose-built piece of tech gear; easily identified by the lack of several failure points that are commonly seen in recreation pencils:

Plus, you'll also notice the model I use has no wireless transmitter, no switches to fail, etc.

Now, you may say "But Ray, isn't a pencil a life support system?" And of course you'd be right to ask that question. You'd sound like a bit of an alarmist nut, but you'd be right. Either way, I do worry about redundancy for anything that holds my life in its hands (if it had hands) so I always carry an appropriate backup...

Some folks may opt to carry a SparePencil^TM...

but I believe that something that was originally designed to carry just enough graphite to enable helicopter pilots to write "Oh sh-t!" before drowning has no place in tec diving! That's why in cases where you REALLY need redundancy many recreational divers opt to sling one of THESE as backup...

On the other hand, hard-core tec people like myself will often "dive doubles"...

which are perfect as this configuration allows you to completely isolate one pencil in the event of a "catastrophic" failure...

:shocked2:

You know, for me pencil's tend to crack and break after multiple dives... I like to go with those one's that have a bunch of pre aranged "pencil heads" in the body of the pencil and they come out as they get dulled to be replaced by another, it's in between a mechanical pencil and a real pencil I guess, but they're plastic not wood.

 

[UCFKnightDiver]

To play a little devil's advocate.... the example you gave just stated you'd need a certain amount of air assuming "you are at your ndl and you run out of gas". Is it a coincidence you weren't paying attention to your NDL and just happened to run out of air at the minute you hit it, or was the dive planned to max out your NDL time? I would think use of an emergency air soruce would only occurr due to accident, and be highly unlikely to occur right at the moment you max your NDL. I dove with a guy who always planned on running out of air at 15-20 feet and doing a CESA every dive (I wasn't aware of his plan, found out when I saw him swimming to the surface), I've heard of others that drain their tank and use their pony every dive, either seems like a bad move to me. In an unplanned emergency I'm good with making it to the surface, air to spare would be nice, but planning to max out my NDL just isn't in the plan for me.

Ok, you're close to your ndl, and yes it is possible, if someone wasn't watching their gas properly etc.

Of course ascending at the proper rate with all stops included is best, but it seems to me that you're overlooking the fact that ascending 60' in 60 seconds beats the bejesus out of a sprint to the surface on whatever air you may or may not have in your lungs and hoping you make it there alive.

If you were to end up bent after a too quick ascent on a SpareAir, then just imagine how much more bent you'd be after a balls to the wall CESA.

I'm simply planning a rock bottom scenario, sure if a spare air is all you have by all means use it, but if you're looking at something to go out and buy I wouldn't recommend it. Buy a pony instead, it's only a little bit more if any and will give you quite a bit more gas, that way you don't need to do any kind of CESA/quick ascent at all.