Why extra air when solo?

[doctormike]

If I have a 2nd stage free flow problem in warmer water, depending on depth and need/desire to do a safety stop

Assuming we are talking about recreational diving and not at trivial depths. For the purposes of general advice, I would just make my contingency plan such that I don't have to eliminate any other safety protocols in the event of a gear failure. People often bring this up in the context of the endless pony size discussions - they say "I always do a safety stop, but if I had an emergency I wouldn't do one". My response "why not just set yourself up so that if you have to ascend due to failure of your primary gas supply, you can still do the stop since you thought it was worth doing on all of your other dives?"

I would either switch to the octo on necklace under my chin and head skyward

The only use of an octo for a single tank diver is if there is a problem that only affects your primary regulator and doesn't involve a gas loss. That is - failing closed or lost mouthpiece. Failing open (i.e. unstoppable free flow) or hose leak means that the octo isn't going to be good for long, especially if it happens in the later part of the dive.

I appreciate your post as it made me think through my protocol again, and there is always occasion to reflect on this.

-Z

Now THAT is a thinking diver! I also really enjoy these discussions, and I often learn things from them.

 

[AfterDark]

Serious question: how significant is the extra drag your backup causes, and how big is the failure risk?

If I were to guess, my first answer would probably be "not at all significant"

I don't know what others do but my octo is tucked away behind me secured to my BP when I'm solo diving, as stated early there is a shut off on the 2nd. I did do the remove replace thing for awhile but got tired of it. I've notice no different between the 2 configurations in relation to drag felt.

As an aside but related to this discussion is a small incident that happened to me last Sunday.

I have always taken the opportunity of the annual VIP to change the O-rings on the valves, and the 5 year hydro to change the tank to valve O-ring also. This year I failed to do change to O-rings on my valves post VIP. While getting my gear together I attached the reg to the valve, turned on the valve, checked the pressure, tested both 2nd stages, shut the 2nd stages off, laid the tank down and started putting on my wet suit. When I had my farmer John pants about mid thigh the valve's O-ring blew out. I hopped and hobbled over to the tank and shut off the valve.

Lessons learned: shutting off ones air while gearing up may not always be the best idea, had I done that the O-ring would have almost certainly blown out during the dive.

STICK TO TIME HONORED MAINTAINCE PRACTICES. They work and in this case are cheap.

Oh yeah and I almost forgot my save a dive box that day too, spotted it at the last minute checking that I had everything.

I'd have to go way back to recall the last time this happened to me. I was probably still in my teen years.

 

[doctormike]

I'm not a solo diver... [but] I'm a DM that helps with OW courses

You ARE a solo diver. You just don't have the card yet.

 

[Zef]

Serious question: how significant is the extra drag your backup causes, and how big is the failure risk?

I think the constant prattle about "failure points" is way overblown. There seems to be an inordinate amount of concern about "extra failure points" used as a means to rationalize one's configuration over another....but there also seems to be acceptance or willful ignorance of similar failure points when it is convenient or deemed favorable regardless of reason.

The discussion of additional failure points should probably be split off into its own discussion:

Additional Failure points: A concern to take seriously or hyperbole.

-Z

 

[drbill]

I'll give you a good reason. I've dived solo most of my 57 years on SCUBA. One day I decided not to attach my pony to my main tank as I planned to go to just 40 fsw. However, a large bat ray caused me to descend to nearly 80 fsw as I filmed it. Then, suddenly, no air was flowing thru my reg. I made an emergency ascent from that depth. At first I thought the fill station had failed to fill my tank, but then remembered I had checked my air pressure as I walked to the sea. Turns out that a tiny piece of debris had fallen into my valve's dip or debris tube and clogged it. Only had that happen once in all my years, but it happened. The unexpected. If I had put my pony on before descending it would have been no problem.

 

[Zef]

I'll give you a good reason. I've dived solo most of my 57 years on SCUBA. One day I decided not to attach my pony to my main tank as I planned to go to just 40 fsw. However, a large bat ray caused me to descend to nearly 80 fsw as I filmed it. Then, suddenly, no air was flowing thru my reg. I made an emergency ascent from that depth. At first I thought the fill station had failed to fill my tank, but then remembered I had checked my air pressure as I walked to the sea. Turns out that a tiny piece of debris had fallen into my valve's dip or debris tube and clogged it. Only had that happen once in all my years, but it happened. The unexpected. If I had put my pony on before descending it would have been no problem.

Point of order: a large bat ray did not cause you to descend unless it was sporting a gun and pointed it at you and demanded you follow it...since you were filming you should be able to produce evidence of this if it were the case.


Happy Friday everyone!!!

-Z

 

[AfterDark]

I think the constant prattle about "failure points" is way overblown. There seems to be an inordinate amount of concern about "extra failure points" used as a means to rationalize one's configuration over another....but there also seems to be acceptance or willful ignorance of similar failure points when it is convenient or deemed favorable regardless of reason.

The discussion of additional failure points should probably be split off into its own discussion:

Additional Failure points: A concern to take seriously or hyperbole.

-Z

And/Or are failure points unavoidable?

Good point Zef, a octo 2nd stage is an acceptable/risk failure point when buddy diving but an unacceptable risk when solo diving with redundant air. Why? A failure point is a failure point whether your redundant air is your buddy or your pony. IMO the pony is a quicker option than is a buddy especially where vis is often less than 5'.
IMO it begs the question why an octo? Why not everyone carry/tote a pony all the time and make the buddies air secondary? IMO it may put more divers into more of a self-sufficient mindset.

 

[Fastmarc]

Point of order: a large bat ray did not cause you to descend unless it was sporting a gun and pointed it at you and demanded you follow it...since you were filming you should be able to produce evidence of this if it were the case.


Happy Friday everyone!!!

-Z

Why would the bat ray allow him to leave with evidence that will identify it? Come on, I know it's Friday, but it's still early...

 

[2airishuman]

Ok, I’ll bite. What’s the point of solo diving with a fully redundant gas supply and then putting two second stages on your back gas?

The main reason is standardization of kit since most people who dive with ponies don't use them on every dive.

 

[2airishuman]

OK, fair enough. As a solo diver, you bring a backup second stage so that you can continue to dive on your back gas in the specific case of your primary second stage failing closed.

That's a very unusual situation, and to me it's not worth adding the failure point just so that I could continue to dive (instead of ascending) if that happened. Far more common situations would be LP hose failure or an unrecoverable free flow, in which case the backup second stage on your back gas is not useful - you need to go to your alternate gas supply and ascend.

It's pretty unusual for a secondary 2nd stage or its hose to fail. I think the greater risk is that having a 3rd reg can contribute to diver confusion. There have been fatalities where someone has their air off and mixes up their pony and backgas regs, which is IMO the biggest risk of diving with a pony.

Anyway, these sorts of fiddly corner cases are one of the reasons I like to dive a twinset when I'm solo. It's a much better configuration than a single and a pony, simpler, safer, more redundant, more intuitive. The only real problems are that it's hard to rent twinsets and they are heavy and nondivisible. Although, the total weight of kit isn't much different when you compare a small twinset (2x50, 2x72, 2x80, etc) to a pony and single of comparable capacity.