Sharing air to extend bottom time

[TSandM]

If you aren't comfortable sharing gas, don't do it.

Don't share gas below the rock bottom for the dive. If you don't know what the rock bottom is, don't share gas to extend bottom time.

Don't share gas to extend bottom time if your equipment configuration does not permit swimming comfortably side-by-side while sharing gas.

But if you know what rock bottom is, have a gear configuration that permits easy gas-sharing, and you and your buddy are comfortable with a PLANNED and DISCUSSED period of gas-sharing to equalize consumption, I honestly see no significant risk involved at all, and I intend to continue doing this with my equally comfortable husband, when we do not have the option of using different sizes of tanks.

I am not going out and buying a $700 sidemount setup to avoid a bit of air-sharing.

 

[DevonDiver]

with all due respect i don't think sidemounting is for everyone, especially those of us that just wanna go on vacation, do 4-6 dives in a week and look at pretty fishies up to 60ft deep

That's kinda the point... there are divers who want to look at pretty fishies... but for longer than they can currently manage on a single tank.

Even for those with good air consumption - when using nitrox - gas supply is still going to be the critical issue:
NDL AIR @ 60ft/18m = 56 minutes.
NDL 36% @ 60ft/18m = 115 minutes.

Most noobies wouldn't get close to the air NDL before gas supply ended their dive. Most experienced divers wouldn't get close to the nitrox NDL before gas supply ended their dive.

IF people are suggesting the use of air-sharing to extend bottom time - then there is obviously an issue with insufficient gas supply to meet divers needs. No, not everyone - just for some. And for those 'some'... sidemount doubles is an easy, cost-effective and permanent solution.

It sucks to be the 'pariah' who causes every dive to end because of a high SAC. I know...because I was that person when I was a new diver. I have great sympathy for the 'air hogs' of this world... that athletes with big lung volumes, the guys with large builds or above-average muscle mass. With that sympathy in mind, I don't like to hear 'experienced divers' scoffing at their problem or recommending 'un-sanctioned' techniques that may not be optimal for their capability level. Heck... having to share air on a dive is hardly optimal for their enjoyment level either... or their sense of self-esteem.

Really... how does it make you feel to be the guy that relies on a 'hand-out' from your buddy, so that you don't foreshorten their dive?

How does it feel spend X% of your (paid for) dive tangled with your buddy at the end of a 36", or even 7', hose? Is that the "wonderful feeling of freedom" that we anticipate and should enjoy when scuba diving?

Look at my avatar pic.... that's me.... in rash guard and shorts.... on a 'recreational' dive....through a 'regular' dive center... floating weightless and having a wonderful time... with two AL80s sidemounted... all the gas I could ever need

i do have to ask though...lets assume the events i went through took place while i had a sidemount...what would be your recommendation in that case?

Not quite sure what you're asking? If you had sidemounted doubles, you wouldn't have been low-on-air in the first place. YOU wouldn't be the person worrying about air consumption any more...

I must have been asleep at the wheel........ When did side mount become a standard practice for rec divers? The last I looked, it seemed that the only guys that wouldn't die using it were a select few in cave country!

Over the last 24 months...it's gone 'mainstream'. PADI being the 'slow guy' only released their standardized recreational sidemount course earlier this year (although a distinctive has been around for longer).

The benefits of sidemount for rec divers is one of the key issues to have been identified by the agencies. They never took such actions with back-mounted doubles... but sidemount has certain advantages making it relevant for recreational diving - primarily the use of 'regular' cylinders at any dive center... easy of transport and ease of use.

This entire debate is about extending bottom time. Obviously, there are many demographics within the diving community that don't care about doing that... people who don't bother with any continued education... people that don't care about developing good skills... people that don't care about having 35 minute dives.

For the demographic that does care... there are better options that air-sharing...that are now commonly available...

For the average vacationing diver, to expect them to switch to side mount, just to avoid sharing air is beyond the realm of practicality.

Firstly... most vacation divers don't share air to extend bottom time. Let's not think that this is, in any way, a common or standard practice. Most people just suffer short dives.

Secondly... the course is available to Open Water divers...can be done in a weekend... less work involved than an AOW course....and it actually gives the diver a tangible benefit. It's new... so it isn't understood (yet)... but it's one of the fastest-growing interest areas in the diving community and, with the full support of multiple agencies, is going to be much more common-place.

It's also a very good course - and answers many of the common criticisms of weak diving training that we encounter here on Scubaboard. There's a strong emphasis on buoyancy, weighting, trim and propulsion. Frog kick, helicopter turn and back-kick are taught as standard. Long-hose air sharing is taught as standard. Proper trim and precision buoyancy are performance requirements. (more in common with 'fundies', than OW/AOW).

An open-water diver can buy a BCD like the Hollis SMS100 - easy to use and familiar to jacket-BCD users.... similar price range to 'decent' jacket BCDs on the market - and they have the option/capability to approach any dive from either back-mount single or sidemount. They use 'regular' rental cylinders - no special requirements.

I would love to switch my BP/W to side mount instead of using doubles.

That's what I did - it cost me less than $200 to convert an existing BP/W into a nice sidemount rig. I had too buy a few things... an OMS sidemount adapter, a soft-backplate (not needed for ow, but better for penetrations), a length of bungee, an old car tire inner-tube, 4 bolt-snaps and 2 cam-bands. Hey presto!

See my 'Frankenstein Project' in the sidemount forum

I kind of like having the long hose when I am diving anywhere where I may need to have my OOA buddy may need air until they are securely on the boarding ladder

Long hose is standard on the PADI recreational and technical sidemount courses.

 

[BluewaterSail]

Mr Devon Diver,

Is there an advantage to sidemount vs standard backmount with a slung al80 stage?

 

[Peter Guy]

Andy, Super, et al -- As I wrote earlier, YOU all have convinced me that my prior few times of doing this were evil, wrong and never to be repeated -- NEVER, Ever -- (what never, no never, what never, well.......) Your overwhelming logic that air sharing for THE PURPOSE OF EXTENDING BT is wrong, wrong, wrong is just too much to be refuted.

I'm just glad you ALL agree that air sharing for the purpose of PRACTICING air sharing is a good thing. BUT, here's one of my problems, WHAT IF my beloved wife and I decide to do an air sharing drill whilst on a dive, would that mean I shouldn't use up all the available gas (see lecture on gas management for that definition) once the drill is over? Or should we never practice air sharing at any point except the end of the dive when we are both getting down to our reserves (rock bottom) and thus slightly increase our risk if something went wrong with the air share (for example, freezing the 1st stage resulting in a free flow, which has happened to us).

I'm just a little bit confused.

And Andy, the PROPER response is NOT to go sidemount (what a bastardization of something designed for a totally different purpose) but, to the contrary, merely sling a stage. Now, of course, the vast majority of the vacation divers y'all see can't do either of those, but what the hell, they are more convoluted than merely "borrowing a cup of air" and thus are highly unlikely to confuse anyone!

[Hmmm, where is that, are you guys nuts or what, icon?]

 

[DevonDiver]

... if you know what rock bottom is, have a gear configuration that permits easy gas-sharing, and you and your buddy are comfortable with a PLANNED and DISCUSSED period of gas-sharing to equalize consumption, I honestly see no significant risk involved at all, and I intend to continue doing this with my equally comfortable husband, when we do not have the option of using different sizes of tanks.

This may be perfect for you... but in the context of other comments on this thread (not made by yourself) the 'requirements' for air-sharing to extend bottom time start to look very irrelevant to 99% of divers.

That's why I think other solutions are more optimal... because a diver can enroll on a weekend class... gain the capability to extend dives...and a lot more besides.

I am not going out and buying a $700 sidemount setup to avoid a bit of air-sharing.

Because you've already equipped with doubles and made significant expenditure. For a diver who needs the capability of doubles, having not yet made any expenditure... or even a diver who's not yet invested in a single-tank set-up... then it's entirely more cost-effective.

That said, you wouldn't 'just' be getting longer recreational bottom time whilst avoiding 'a bit of air-sharing'. You'd get the capability to travel light and conduct extensive recreational or technical dives without the need to source back-mounted doubles (so, any beach shack dive op would do). As a caver... that'd open up a new world of opportunity..especially remote area diving.

Also, cheapest 'off-the-shelf' sidemount rig is circa $500... you don't need to buy a Razor or UTD, any more than you 'need' to buy Halcyon for backmount. Prices are dropping, as this goes more mainstream.

---------- Post added ----------

I'm just glad you ALL agree that air sharing for the purpose of PRACTICING air sharing is a good thing.

That's where you are failing to see the differentiation.

Divers aren't taught to practice 'air-sharing'. They are taught to practice 'air-sharing ASCENTS'. A specific, step-by-step emergency drill.

WHAT IF my beloved wife and I decide to do an air sharing drill whilst on a dive,

What 'air-sharing drill'? As an instructor, you teach (and were taught to teach) an OOA drill. Nothing more, nothing less.

would that mean I shouldn't use up all the available gas once the drill is over?

If you're talking official 'drills and skills'.... then you (as a PADI instructor) would/should ask PADI that question. We both know what the answer would be....

I'm just a little bit confused.

No...you're not. What you've been taught just doesn't 'fit' with what you want to do. It's hard to rationalize that, without accepting that you wouldn't be sanctioned by the agency you teach for.

And Andy, the PROPER response is NOT to go sidemount (what a bastardization of something designed for a totally different purpose)

That's as pathetic as arguing that BP&W isn't suitable for open-water divers, because it's a 'bastardization of something designed for a totally different purpose'.

You know it....

but, to the contrary, merely sling a stage.

Nope... show me a recreational course that teaches 'slinging a stage' for increased bottom time.

Peter... your knowledge is out-of-date... not blameworthy, because sidemount is a 'new thing'.... but it is mainstream now... and it is supported by multiple agencies for the purposes of recreational diving... with the stated benefit of extending bottom time, amongst other things.

Besides sidemount, there is no other sanctioned, formalized and supported by training method for recreational divers to extend bottom time (gas supply), except for 'use a bigger single tank'.

 

[TSandM]

I spent a week at a resort in north Vancouver Island with Curt Bowen of Advanced Diver Magazine (along with a half dozen other people). Curt was diving sidemount, and he managed it quite neatly with double Al80s. I absolutely LOVE diving double Al80's in warm water (although without the manifold and bands, the weighting issues make me a bit dubious).

But honestly, we're just talking about your average recreational reef dive, where Peter will hit gas reliably, every dive, before I do. Both of us have gas consumption lower than most people's, but his is higher than mine. We spend five or ten minutes, usually in the first third or so of the dive, sharing gas . . . that way, we'll hit rock bottom at roughly the same time. We don't do it in high current. We don't do it on technical or cave dives. We do it where it's easy and simple. It buys us maybe five, ten minutes more dive time. We like doing it. We would never have gotten to see the whale off Lanai if we hadn't bought those extra minutes . . .

 

[DevonDiver]

Mr Devon Diver,

Is there an advantage to sidemount vs standard backmount with a slung al80 stage?

Trim, control and comfort primarily. Sidemount feels very nice in the water, it 'doesn't feel like diving double' - slinging a single AL80 is abominable in comparison.

It's a much more stable 'platform'.

Streamlining - properly trimmed sidemount tanks are parallel with your body - sheltered beneath armpits. There's also less 'wobble' with sidemount - they are more snug and secure. A stage dangles below - reducing stability, risking entanglement and stopping you getting close to the bottom (i.e. photographers).

Without experiencing the difference, it's hard to appreciate the nuances between staging and sidemounting. Those nuances make a world of difference though.

I absolutely LOVE diving double Al80's in warm water..

So did I, in backmount. Even more so, now they are sidemounted. It's a very sweet way to dive.

What's best is the fact that I now get to dive doubles wherever, whenever.... so that's every dive.

...although without the manifold and bands, the weighting issues make me a bit dubious

My weighting shift was 4lbs. Diving in rash guard and x-shorts... Backmount in Ali BP and Al80s needed 2lbs of weight. Sidemount in soft backplate and AL80s needs 6lbs (2x 1lbs trim on shoulders/2x 2lbs rear).

But honestly, we're just talking about your average recreational reef dive

Understood. I love the feeling of sidemount. It's really no more 'hassle' than a single tank dive...and I feel more comfortable and stable on the dive. I'd hate being 'shackled' to another diver for any duration on the dive.

You and Peter are a well-established buddy pair. Can you imagine using 'air-share for extended bottom time' with an insta-buddy on holiday?

Air consumption and supply is the 'issue', not the nature of the dive. In that respect, I don't see a difference between rec or tec or cave. I get to do enormous photo dives in the shallows, especially with nitrox.

As a DM/Guide/Instructor, I have a substantial amount of gas to cover all contingencies - there's a thread active at the moment about a customer who went into deco and OOA... and the DM didn't have sufficient gas to share-air to support the customer's deco. Doubles cover even rare contingencies like that.

For the cost of back-mount single + pony set-up, you can just use sidemount. It's cheaper than backmount double, because you've got no bands or manifold to buy. No heavy rig to carry around. Some of the sidemount rigs pack into a bag smaller than a laptop bag... so you can carry-on an entire kit, suitable for tech, in your hand luggage. I travel a lot for diving, often using public buses... my entire rig, including regs, fits into a 30litre daypack.... that is NICE. You can obtain tanks from any dive op in the world.

2x AL80 for 2 dives - no added logistics.

First (deeper) dive... use a full 1500psi per tank - give you 3000psi of USEABLE gas (you still have 1500psi reserve per tank). Rock bottom is virtually inconsequential. That's a 1/6th increase in gas supply.

Second (shallower) dive... you have 1500psi per tank...the same gas volume as you'd normally get from a single AL80 at 3000psi. Of course, you get more if you haven't used a full 1500psi from each tank on the first dive! Balancing tanks to preserve a rock-bottom is easy - one tank/one rock bottom for you and your buddy.

Diving single tank, you reserve at least 500psi per dive (1/6th of your total gas).
Diving sidemount, you reserve at least 500psi for the end of a series of dives... less gas 'goes home' at the end of the day.

If cylinder supply isn't a problem - you have the option to change both tanks each dive...using 'rule of thirds'... and still not cry about short dives.

If air consumption isn't a problem (experienced + shallow dives) it's entirely feasible to get 3+ dives out of a pair of AL80... without detriment to redundancy or rock bottom.

Of course, if logistics permit.. for a single tank dive, you could have a lot of fun with 2x AL40 or AL60..

 

[SeaCobra]

I just feel that this over-complicates a dive without any real reward.

 

[dumpsterDiver]

...If air consumption isn't a problem (experienced + shallow dives) it's entirely feasible to get 3+ dives out of a pair of AL80... without detriment to redundancy or rock bottom.

Of course, if logistics permit.. for a single tank dive, you could have a lot of fun with 2x AL40 or AL60..

Of course it might be a lot easier to carry a small pony and use an equalizer whip on the boat to get three dives out of two tanks.. and the diver would not have to drag around two big tanks for the whole dive....Right? or is THAT not allowed as well because PADI doesn't teach it as a specialty?

 

[t4e]

It sucks to be the 'pariah' who causes every dive to end because of a high SAC. I know...because I was that person when I was a new diver. I have great sympathy for the 'air hogs' of this world... that athletes with big lung volumes, the guys with large builds or above-average muscle mass. With that sympathy in mind, I don't like to hear 'experienced divers' scoffing at their problem or recommending 'un-sanctioned' techniques that may not be optimal for their capability level. Heck... having to share air on a dive is hardly optimal for their enjoyment level either... or their sense of self-esteem.

Really... how does it make you feel to be the guy that relies on a 'hand-out' from your buddy, so that you don't foreshorten their dive?

How does it feel spend X% of your (paid for) dive tangled with your buddy at the end of a 36", or even 7', hose? Is that the "wonderful feeling of freedom" that we anticipate and should enjoy when scuba diving?

tbh for now, at my level (10 dives) i am not feeling any remorse for having a high SAC
why?..first because my husband is at about the same level as me, we ended each dive with pretty much the same amount of air left
second, because since we are aware of our limitations we chose to hire a private guide
third, because for now we are content with getting a 40-45 minute dive at 50-60ft on one regular 80 tank

as for how it feels to dive tangled with my buddy, i said it before in this thread, if it wasn't for the fact that this was a drastic deviation from the dive plan and my mind was racing to figure out what is going on since my husband was at about the same air level as me, slightly higher, and what the next step will be, i was actually quite comfortable
having said that we have no intention of making a habit of air sharing to extend the dive as part of any dive plan in the future

Not quite sure what you're asking? If you had sidemounted doubles, you wouldn't have been low-on-air in the first place. YOU wouldn't be the person worrying about air consumption any more...

so it wouldn't be me worrying about air consumption, would be someone else and they will end my dive
the way i see it is that a sidemount would work if everyone else in the group would be aware of their air consumption and have a sidemount too, which is very unlikely in a bigger group

so my question was what would be the dive plan in this case?
no matter how many tanks you haul around they will run out eventually so at what air level should we start the ascent?

i just don't see how it would have worked out any better in the scenario we were in, where the major problem was the deviation from the dive plan, we were supposed to start the ascent
the DM could have decided to share air in that situation too

i hope this makes sense