BCD's

[Graham Bevan]

I am currently looking to purchase my first BCD. I am therefore mainly undertaking an information gathering exercise at present before deciding upon one to purchase.

I have looked at the Buddy range and note that they have an emergency air cylinder as one of their safety features, and which I like the idea of. I have not seen this feature on any of the BCD's I have seen, (not a exhaustive search at present mind). Are Buddy the only manufacturers which use this feature or are there any other makes/models which use this feature.

[john kendall]

I am currently looking to purchase my first BCD. I am therefore mainly undertaking an information gathering exercise at present before deciding upon one to purchase.

I have looked at the Buddy range and note that they have an emergency air cylinder as one of their safety features, and which I like the idea of. I have not seen this feature on any of the BCD's I have seen, (not a exhaustive search at present mind). Are Buddy the only manufacturers which use this feature or are there any other makes/models which use this feature.

AFAIK AP are the only people who put emergancy bottles on their Jackets. They are left over from before BCs had direct feed inflators. And IMHO are not required. Almost all the people I know with Buddy Jackets have removed them, and most of the ones I still see around at dive sites tend to be a really bad state. You have to look after it as thy corrode over time, and have to practise using one as they are not easy. You also gain the issue that if it starts leaking you can't tell if it is the Emergancy bottle or the Direct Feed that is causing the jacket to inflate by itself.

It is a feature that really is not required.

HTH
John

[Adrian Kelland]

Graham

These emergency cylinders are the cause of very different responses from divers. Some think them a good idea, some think they are bad, the nickname 'suicide bottle' should give you an idea here.

The main comment against them is that they could be accidently knocked on, leading rapidly to an out of control ascent. Not good. They also should be tested, just like any other scuba cylinder. How many are I don't know. I have left mine off my jacket this year, its getting very corroded. They certainly won't give you much air, and the method of breathing from them via the BCD is no longer taught.

I don't know of any other BCDs that have such cylinders, although there used to be BCDs with the soda-syphon type of CO2 cartridge. These were a one use emergency only peice of kit, which could not be controlled except by dumping air.

A BCD, like any other kit, should be purchased after consideration of what kind of diving you intend to do, and how you wish to progress. Unfortunately, the approach to kit purchase is not discussed often enough even in training. Certainly don't fall into the trap of buying what the guys around you have, just because they have it. Ask them why that BCD, Reg etc. can they give a reasoned answer. I know I could not with my first kit. I can now. Also don't buy into shop kit deals. You have to be comfortable with each piece of kit, not a cheap deal.

A good site to help you think about kit is Dominic Humphries, quoted in the Wing article in this months Dive mag. Link to the BCD part of his site is below.

Adrian

[PeteM]

A good site to help you think about kit is Dominic Humphries, quoted in the Wing article in this months Dive mag. Link to the BCD part of his site is below.

That's a good site, also have a look at this one
<a href="http://www.bitz.fsnet.co.uk/" >http://www.bitz.fsnet.co.uk/</a>

[Adrian Kelland]

:=A good site to help you think about kit is Dominic Humphries, quoted in the Wing article in this months Dive mag. Link to the BCD part of his site is below.

That's a good site, also have a look at this one
http://www.bitz.fsnet.co.uk/

Pete

Yep, forgot about that one, even though its one of my bookmarks. Comes from working off the top of my head.

Adrian

[edward haynes]

I dive with a Buddy, but have stopped fitting the bottle. There are so few people around now who where trained in its use. And NONE who are competent to rescue me using one.

I like buddy jackets, but save your money and don't buy a bottle if you don't have to.

Edward

[Phil Laughton]

:Another point to consider is how the BC will hold you on the surface. A fully inflated Buddy will hold you head up, where as some others will not. Some will through you onto your face. Not the best if you are unconscious.
Phil
=I am currently looking to purchase my first BCD. I am therefore mainly undertaking an information gathering exercise at present before deciding upon one to purchase.

I have looked at the Buddy range and note that they have an emergency air cylinder as one of their safety features, and which I like the idea of. I have not seen this feature on any of the BCD's I have seen, (not a exhaustive search at present mind). Are Buddy the only manufacturers which use this feature or are there any other makes/models which use this feature.

[Paul Oliver]

Hi

Got rid of mine years ago, but i tend to agree with those that keep it as "Another Option". Need to practice with it though.
Each to their own.

Dive Safe

Paul

[Chris Cherrington]

I am currently looking to purchase my first BCD. I am therefore mainly undertaking an information gathering exercise

I agree with all the comments about the buddy range - ditch the little bottle. Sucapro used to do a similar jacket if I remember right.

My advise would be to buy something cheap -secondhand perhaps and then dive for a year or two. If you start thinking about technical diving most BCDs don't have D rings and you will be looking at a wing type device. I bought an old secondhand BCD five years ago and still use it. If you wear a drysuit that is an adequate redundant BCD. Save your money!!

[Tony Dwyer]

Way back when, several manufactures fitted inflation cylinders. I have an old Dive Systems 2000 (bought 1989 and not used for a while) that used to have one. Caused a major flap at San Francisco airport in 1991, because I forgot to take it off the jacket (ho hum).

My Buddy Commando (also 1989 vintage and still in use) used to have one, but I got rid of the thing a long time ago.

The old idea that you could use the thing to breathe from the jacket was bordering on suicide, hence the nickname (suicide bottle). In my opinion it should only have ever been used for inflation on the surface.

There is a risk that the cylinder could get turned at depth, small risk I agree, but enough to scare the bejessus out of me when someone actually did it to me in the pool. The cylinder came off the BC after that.

Save your money, don't buy the inflation cylinder. Buy a BC that suits your needs.

[Andy Nye]

Stick a small lenght of hose on it,,, ideal for filling lift bags, Dsmbs ;-)


Andy

[aquabin]

Stick a small lenght of hose on it,,, ideal for filling lift bags, Dsmbs ;-)


Andy

Is it the same one as AP use for their self inflating DSMB?
Matt

[PeteM]

Is it the same one as AP use for their self inflating DSMB?

No its 0.4L , DSMB bottles are either 0.1 or 0.2

[Gordon Archer]

I am currently looking to purchase my first BCD. I am therefore mainly undertaking an information gathering exercise at present before deciding upon one to purchase.

I have looked at the Buddy range and note that they have an emergency air cylinder as one of their safety features, and which I like the idea of. I have not seen this feature on any of the BCD's I have seen, (not a exhaustive search at present mind). Are Buddy the only manufacturers which use this feature or are there any other makes/models which use this feature.

Hi
I dive a Buddy profile that gives you all the controls at the front. I also have the small emergency air cylinder and still train, test, and use it.
It is a very useful piece of equipment, but like most pieces of equipment must be maintained and training in its use undertaken.
It is like previous post's have stated a throwback to the ABLJ days on which I initially trained.
Because of that training and the equipment migration to the Buddy profile I have maintained my skills, and teach new divers with this equipment in its use & deployment.
But to all the knockers of this piece of equipment I would ask if they have ever tried to gain bouyancy with a free flowing system. The emergency cylinder is the only truly independant source of bouyancy when the rest of your supply is compromised by a free flow. (Remember every day at Stoney during the winter free flows are to be seen).

[john kendall]

But to all the knockers of this piece of equipment I would ask if they have ever tried to gain bouyancy with a free flowing system. The emergency cylinder is the only truly independant source of bouyancy when the rest of your supply is compromised by a free flow. (Remember every day at Stoney during the winter free flows are to be seen).


Rubbish is it. Let me see, other ways of gaining bouyancy, well even with a freeflow you can still inflate. Or you could fin upwards, well you are neutral aren't you, a little upwards motion and you are bouyant. Or if you are using a twin-set (Which I know the original poster isn't) you can use your drysuit which is attached to the other reg, or to an Argon bottle. Or you can orally inflate if you really have to.

Having an HP system connected to your BC is a good way go making sure that you will have an uncontrollable bouyant ascent at some time. All it takes is for the valve to be knocked on a bit, and it will take you longer than you think to work out that it is the "Magic Motorcycle" doing the inflation, not your Direct Feed.

There are often different ways of doing things, you need to pick the one that gives the most while causing least problems.

John

[Andy Nye]

Sending a dead diver to the surface from depth in an OOA situ.

[Gordon Archer]

Rubbish is it. Let me see, other ways of gaining bouyancy, well even with a freeflow you can still inflate.


Have you tried this, Air will take the path of least resistance and that will be the free flow direction, so the direct feed is compromised. Try it next time you are in the pool.

Or you could fin upwards, well you are neutral aren't you, a little upwards motion and you are bouyant.


You would hope so, but not if the free flow was to hit during the decent this would present a slightly different problem and this does happen.

Or if you are using a twin-set (Which I know the original poster isn't) you can use your drysuit which is attached to the other reg,


Only if the other reg is independant and not manifolded as so often twin sets are.

or to an Argon bottle.


There is no difference here to having a small emergency bottle on you BCD, so are you now agreeing that its a good piece of equipment to have?

Having an HP system connected to your BC is a good way go making sure that you will have an uncontrollable bouyant ascent at some time.


Isn't that why we all train constantly to recognise the feeling of bouyancy and what is happening before we get an out of control situation.

All it takes is for the valve to be knocked on a bit, and it will take you longer than you think to work out that it is the "Magic Motorcycle" doing the inflation, not your Direct Feed.


Why should that happen any more that the direct feed being trapped on or stuck open when operated. Which I have seen happen quite often.

There are often different ways of doing things, you need to pick the one that gives the most while causing least problems.


Agreed! that is why I recommend the buddy profile, it has all the controls in front where the diver is in control.
And isn't that answering the original post on the equipment and the emergency cylinder as requested.

[PeteM]

:=Or if you are using a twin-set (Which I know the original poster isn't) you can use your drysuit which is attached to the other reg,
:=
:=
Only if the other reg is independant and not manifolded as so often twin sets are.

Sorry - but that is complete rubbish.

A manifolded twin set has two independant regs, assuming my primary starts to freeflow my secondary will continue to get gas at bottle pressure (and vice vica), which ever bouyancy source is attached to the non free flowing reg will continue to work fine as long as it still has gas available which you make sure happens by doing a shut down

Pete

[Gordon Archer]

:=:=Or if you are using a twin-set (Which I know the original poster isn't) you can use your drysuit which is attached to the other reg,
:=:=
:=:=
:=Only if the other reg is independant and not manifolded as so often twin sets are.

Sorry - but that is complete rubbish.

A manifolded twin set has two independant regs, assuming my primary starts to freeflow my secondary will continue to get gas at bottle pressure (and vice vica), which ever bouyancy source is attached to the non free flowing reg will continue to work fine as long as it still has gas available which you make sure happens by doing a shut down

Pete

Before we start shouting rubbish at each other your suggestion need some further explination. If you have two regs attached to a manifolded system you are really taking air from different ends of the same air resevoir.
In such a situation any air loss from the system has to effect this resevoir. The only reason that the non free flowing regulator would continue to function is because the time taken to dissipate the pressure in the resevoir.
As you said you would have to do a shut down of the free flowing side. So what time do you have before the freeflow dissipates the pressure available?
Of course this is depenant on the current pressure available at the time of the free flow.
So how indepandant are they truly?

[Adrian Kelland]

As you said you would have to do a shut down of the free flowing side. So what time do you have before the freeflow dissipates the pressure available?
Of course this is depenant on the current pressure available at the time of the free flow.
So how indepandant are they truly?

Gordon

You might find the article below useful regarding importance of shutdown time v cylinder size v available pressure.

Adrian

[Vic]

&gt; If you have two regs attached to a manifolded system you are
&gt; really taking air from different ends of the same air
&gt; resevoir.

You've missed a very important part - the regs are connected to the reservoir via a tiny orifice.

&gt; In such a situation any air loss from the system has to
&gt; effect this resevoir.

Not substantially. Although your IP might drop during a free-flow, the effect on tank/manifold pressure as a result of this will be immeasurably small. Only as the cylinder empties does the pressure drop.

The end result is that the second reg - the one that isn't freeflowing - sees no measurable change in supply pressure. So it's unaffected.

&gt; The only reason that the non free flowing regulator would
&gt; continue to function is because the time taken to dissipate
&gt; the pressure in the resevoir.

Are you claiming that the manifold is some sort of reserve, or have you just admitted that the second reg will only stop working once the cylidners are empty?

&gt; As you said you would have to do a shut down of the free
&gt; flowing side. So what time do you have before the freeflow
&gt; dissipates the pressure available?

Plenty. Even with a full-on flow, a set of twin 12s doesn't empty in a heartbeat.

&gt; Of course this is depenant on the current pressure available
&gt; at the time of the free flow.

Given decent gas-management skills, this isn't an issue. If you've not got enough gas to get out of the water with enough to spare, you've no business being there. The rules get slightly more complicated as the stop lengths increase, but this is basic reserve management that we teach at entry-level...

&gt; So how indepandant are they truly?

They're not independents, they're manifolded. But the supply pressure at each port is suitably independent for the system to function as Pete stated above.

HTH, HAND, etc.

Vic.

[Adrian Kelland]

Your arguements against a manifold only apply to incompentent users and Darwin is going to get them anyway

Trouble is, he doesn't get them all, and then they breed :-)

Adrian

edit: looks like the original post was deleted while i replied :-(

[PeteM]

Given decent gas-management skills, this isn't an issue. If you've not got enough gas to get out of the water with enough to spare, you've no business being there. The rules get slightly more complicated as the stop lengths increase, but this is basic reserve management that we teach at entry-level...

I would also add to that if you can not do adequately fast shutdowns with your configuration you have no business being there

Pete

[Vic]

&gt;&gt; or to an Argon bottle.
&gt;&gt;
&gt; There is no difference here to having a small emergency
&gt; bottle on you BCD

There is an enormous difference (two, actually).

Firstly, the Buddy bottle is 400ml - not an awful lot of excess should something go wrong (total free volume of 80l if it's full). My Argon bottle is nearly 4 times that much.

But - *far* more importantly - an Ar bottle is connected via a regulator and an inflator valve. This makes addition *significantly* easier to control, and accidental inflation almost impossible. And if they system should fail, it's trivial to disable it. Try doing that with a crack bottle...

Vic.

[Gordon Archer]

:=As you said you would have to do a shut down of the free flowing side. So what time do you have before the freeflow dissipates the pressure available?
:=Of course this is depenant on the current pressure available at the time of the free flow.
:=So how indepandant are they truly?

Gordon

You might find the article below useful regarding importance of shutdown time v cylinder size v available pressure.

Adrian

Thanks Adrian this was a useful site, it tends to support what I am trying to say.

[Gordon Archer]

You've missed a very important part - the regs are connected to the reservoir via a tiny orifice.

You are correct, but this will still have an effect on the system, far more than you think.

In such a situation any air loss from the system has to
effect this resevoir.

Even with a full-on flow, a set of twin 12s doesn't empty in a heartbeat.
Of course this is depenant on the current pressure available
at the time of the free flow.

About 35 secs max if you go by the link below.
How long do you take to shut down, have you practiced this?

They're not independents, they're manifolded. But the supply pressure at each port is suitably independent for the system to function as Pete stated above.

As above please visit the link below.

[Vic]

&gt; this will still have an effect on the system, far more than
&gt; you think.

No, this just isn't true.

In the event of a free-flowing regulator, the reg on the other post is able to supply breathing gas. This is well-documented - that's how people survive these situations.

If the IP on hte non-freeflowing reg is stable enough to allow thesecond stage to function, it's sure as hell able to inflate a wing or drysuit.

&gt; About 35 secs max if you go by the link below.

I'd be suspicious of such a claim.

Take a twinset into the garage, without regulators, and open up the valves. See how long it takes to empty. That's about as fast as you'll ever get gas out of those valves[1]. I rarely dump cylinders any more, but I really don't think my twins would empty in 35 seconds...

&gt; How long do you take to shut down, have you practiced this?

About 3 seconds last time I tried it (on an assessed dive). I dont dive OC any more, so it's no longer relevant to me.

&gt; As above please visit the link below.

I'll visit your link, but what you report of it so far is at odds with my first-hand experience.

Nevertheless, your point about a freeflowing reg removing its pair's ability to provide a buoyancy source is palpable nonsense. I do hope you'll retract the claim.

Vic.


Oops! Forgot the footnote!

[1] It is theoretically possible to produce a tuned exhaust system that will enable the truly committed to empty a cylinder more rapidly than just opening it up to the atmosphere, but since this is a control experiment, and the system in question is nothing like such an exhaust, I think it's perfectly safe to ignore it.

[Adrian Kelland]

:=Even with a full-on flow, a set of twin 12s doesn't empty in a heartbeat.
Of course this is depenant on the current pressure available
at the time of the free flow.
:=
About 35 secs max if you go by the link below.
How long do you take to shut down, have you practiced this?

Gordon

I think the article is poorly laid out, but I could not find that figure in regard to emptying cylinders.

2x7l at 100 bar would take 40 seconds to drain at 35l/sec, which is above the drain rates quoted.

There is a 35seconds mentioneed, which was the additional length of time to shutdown before having independant twins became an advantage over manifolded. That was with twin 12.2. The time is only 14 secs for the 2x7 though. And you 'buy' yourself alot of time to sort things once you have closed the isolator.

Adrian

[John Kendall]

:=Or if you are using a twin-set (Which I know the original poster isn't) you can use your drysuit which is attached to the other reg,
:=
:=
Only if the other reg is independant and not manifolded as so often twin sets are.

Others have already covered this.


:=or to an Argon bottle.
:=
:=
There is no difference here to having a small emergency bottle on you BCD, so are you now agreeing that its a good piece of equipment to have?

No, An argon bottle is connected to a LPI via a reg, this reduces significantly the speed that air will get into the system.

:=Having an HP system connected to your BC is a good way go making sure that you will have an uncontrollable bouyant ascent at some time.
:=
:=
Isn't that why we all train constantly to recognise the feeling of bouyancy and what is happening before we get an out of control situation.

Yeah, but which system is causing the inflation, is it your LPI or the crack bottle, if it is the crack bottle then by the time you have pulled the Direct feed from the inflator, then you will still be ascending, Maybe you will have time to check the Crack bottle then, but probably not.

:=All it takes is for the valve to be knocked on a bit, and it will take you longer than you think to work out that it is the "Magic Motorcycle" doing the inflation, not your Direct Feed.
:=
:=
Why should that happen any more that the direct feed being trapped on or stuck open when operated. Which I have seen happen quite often.

Yes, they get stuck on, so you pull the Direct feed off the inflator. If you feel any excess bouyancy on your BC that you have not caused, this should be your first instinct. Having 2 places where air is injected is like having parellel circuit breakers on an electrical circuit, you turn one off and get electrocuted because the other is on.

:=There are often different ways of doing things, you need to pick the one that gives the most while causing least problems.
:=
:=
Agreed! that is why I recommend the buddy profile, it has all the controls in front where the diver is in control.

On the other hand, if you don't have the bottle, then it doesn't matter what jacket you have, all the others have very similar controls, and only 1 way air will get into the system, so only 1 place that problems can occur which can make you bouyant when you don't want.

And isn't that answering the original post on the equipment and the emergency cylinder as requested.

Indeed, I did that up there ^ somewhere near the beginning of the thread.

See ya
John

[iainmsmith]

:=
:=You've missed a very important part - the regs are connected to the reservoir via a tiny orifice.
:=
You are correct, but this will still have an effect on the system, far more than you think.
:=
In such a situation any air loss from the system has to
effect this resevoir.

Yes...but it doesn't affect the reservoir pressure to the extent that the pressure drop has any significant effect on the performance of the seperate system attached to said reservoir.

:=Even with a full-on flow, a set of twin 12s doesn't empty in a heartbeat.
Of course this is depenant on the current pressure available
at the time of the free flow.
:=
About 35 secs max if you go by the link below.

Before citing anything in defence of an unsupportable position, it helps if one actually understands what is being said in the article. Go away and read the article. When you understand what it says, we will be happy to accept your apologies for being a complete muppet.

The claim in the article is that if it takes a diver
with twin 12.2L cylinders 15s to close his manifold, he has a further 35s to close the offending valve before losing so much gas that he would have been better off with independant cylinders.

The article says _nothing_ about time to empty the cylinder.

Having spent a considerable length of time dumping gas from twinsets (and other sizes of cylinders) the time taken to dump the contents of even a relatively empty cylinder (eg 100bar in a 7L) through a fully open valve is in the order of minutes, not seconds.

How long do you take to shut down, have you practiced this?

Three valve shut down in less than 25s.

And you?

:=They're not independents, they're manifolded. But the supply pressure at each port is suitably independent for the system to function as Pete stated above.
:=
As above please visit the link below.

May I suggest you take your own advice and this time read what it says, not what you wish it had said.

Regards,

Iain

[dave covey]

Caused a major flap at San Francisco airport in 1991, because I forgot to take it off the jacket (ho hum).

...I flew halfway round the world with a Parachute as hand baggage. My route took me over Jalalabad.....on Sep 10 2001!!

(imagine explaining THAT if I tried it the following day!)


Off topic, but I couldn't resist a "cove anecdote" lol