Why the choice of oral inflate SMBs?

[LiteHedded]

maybe if you're filling a giant lift bag on the bottom or something, sure. I just don't see the advantage of trying to do it with a regulator purge or lp inflator on a regular dive. seems like a recipe for disaster. especially in conditions you're describing.
especially at the tech 2 level with an hour of deco waiting on you from 70' up

 

[PfcAJ]

maybe if you're filling a giant lift bag on the bottom or something, sure. I just don't see the advantage of trying to do it with a regulator purge or lp inflator on a regular dive. seems like a recipe for disaster. especially in conditions you're describing.
especially at the tech 2 level with an hour of deco waiting on you from 70' up

Not a fan of paralysis and chamber rides?

 

[MXGratefulDiver]

maybe if you're filling a giant lift bag on the bottom or something, sure. I just don't see the advantage of trying to do it with a regulator purge or lp inflator on a regular dive. seems like a recipe for disaster. especially in conditions you're describing.
especially at the tech 2 level with an hour of deco waiting on you from 70' up

Like anything else, you reduce the risks by practicing your technique in shallow water and no-deco conditions. By the time you're doing this in deeper water and/or with a deco obligation, you should have practiced it sufficiently to have the risks associated with that recipe down to an acceptable level ... they'll never be zero.

... Bob (Grateful Diver)

 

[Tortuga68]

The oral inflate technique is taught in Fundies because small bags are the easiest for novices to learn to deploy, and they are sufficient for the conditions in which novice divers ought to be diving. Small bags can be effectively and safely inflated orally, without the task-loading complications of disconnecting hoses or switching regulators

I don't see much difference between switching regs and removing & replacing your reg to perform oral inflation, in terms of task loading. For safety, switching regs would be safer IMO, since you're not exhaling most/all of your breath in between air sources, as you are with oral inflate.

 

[rjack321]

I don't see much difference between switching regs and removing & replacing your reg to perform oral inflation, in terms of task loading. For safety, switching regs would be safer IMO, since you're not exhaling most/all of your breath in between air sources, as you are with oral inflate.

The reg removal is not the dangerous part, its getting the deployed reg tangled in the straps of the bag. Hence the reason (in part) for the non-locking LP hose inflators on the halcyon bags.

For beginners the small SMBs are fine, orally inflated typically works best since its one less hose thing in your hands (spool, and smb alone, no hose or reg needed)

 

[LiteHedded]

Like anything else, you reduce the risks by practicing your technique in shallow water and no-deco conditions. By the time you're doing this in deeper water and/or with a deco obligation, you should have practiced it sufficiently to have the risks associated with that recipe down to an acceptable level ... they'll never be zero.

... Bob (Grateful Diver)

what's the advantage of trying to inflate your bag with a regulator purge? sure I can practice all kinds of circus tricks and get good at them but it doesn't seem like a great idea to me.

 

[TSandM]

I think the technique is used with lift bags, which have a large opening at the bottom and no attachment for a hose. The lift bags they use for the ghost fishing net removal projects are like that. The big risk of filling a bag that way is freeflow, but that's not terribly likely in LA, where they are doing the net projects. I'm sure the guys who are doing them in the Netherlands have to be pretty careful (and I know some groups use a stage bottle for filling, so if it freeflows the only problem is that you can't complete the project, not that someone runs low on gas.)

 

[LiteHedded]

I think the technique is used with lift bags, which have a large opening at the bottom and no attachment for a hose. The lift bags they use for the ghost fishing net removal projects are like that. The big risk of filling a bag that way is freeflow, but that's not terribly likely in LA, where they are doing the net projects. I'm sure the guys who are doing them in the Netherlands have to be pretty careful (and I know some groups use a stage bottle for filling, so if it freeflows the only problem is that you can't complete the project, not that someone runs low on gas.)

right. we're talking about two different things.
the instructors you spoke to allow that method to shoot SMB's midwater on deco in their tech classes? that's where i see the issue. of course if you're filling a huge bag on the bottom to lift something it's a different ball of wax

 

[dbulmer]

what's the advantage of trying to inflate your bag with a regulator purge? sure I can practice all kinds of circus tricks and get good at them but it doesn't seem like a great idea to me.

At depth it's easy !#

The risk as mentioned before is making sure that the reg does not get tangled in the webbing. I cut off the webbing on my blobs so the risk is reduced. Coldwater freeflows - well - you detune your regs, add a little gas as a test and then a bit more gas before releasing the blob.

The key as Bob said is to practice regularly in shallow water where it's easier to develop the skill. I use the reg purge primarily because of who I dive with ie team standardisation

On holiday I use an oral inflate because it's easier to use in warm water with less risk but in cold water I find it harder.

What exactly is it that does not seem a good idea?

 

[MXGratefulDiver]

what's the advantage of trying to inflate your bag with a regulator purge? sure I can practice all kinds of circus tricks and get good at them but it doesn't seem like a great idea to me.

... then don't do it ... seems a simple enough solution. I already explained the advantage. I'd rather hold that bag out at arm's length, where I can see what I'm doing, than have it in close to my face and gear where something I can't see could get entangled.

There's benefits and drawbacks either way ...

... Bob (Grateful Diver)

---------- Post added April 3rd, 2014 at 10:57 AM ----------

I think the technique is used with lift bags, which have a large opening at the bottom and no attachment for a hose. The lift bags they use for the ghost fishing net removal projects are like that. The big risk of filling a bag that way is freeflow, but that's not terribly likely in LA, where they are doing the net projects. I'm sure the guys who are doing them in the Netherlands have to be pretty careful (and I know some groups use a stage bottle for filling, so if it freeflows the only problem is that you can't complete the project, not that someone runs low on gas.)

Freeflow risk isn't as likely as some people make it out to be ... particularly if you're just partially filling a 40 lb bag with a 2-3 second shot of gas. By comparison, last winter when I built that reef, I was using the purge reg process (admittedly from a separate cylinder than the one I was breathing) to fill a 400 lb lift bag. I did that approximately 75 times over the course of 20+ dives, in 43 degree water, and not once did I experience a free flow. If I had it would be a simple matter to shut down the tank, wait a few seconds, and turn it back on again ... but I didn't even need to do that much.

I'll keep things out where I can see what I'm doing. No circus tricks needed ... just a little bit of common sense ...

... Bob (Grateful Diver)

---------- Post added April 3rd, 2014 at 10:58 AM ----------

right. we're talking about two different things.
the instructors you spoke to allow that method to shoot SMB's midwater on deco in their tech classes? that's where i see the issue. of course if you're filling a huge bag on the bottom to lift something it's a different ball of wax

In my experience it's a lot harder to control a huge bag to lift something off the bottom than it is to control your position in midwater while managing an SMB deployment.

... Bob (Grateful Diver)