Split from A&I Yukon thread: Gas Rules in OW Solo Dives

[WetDawg]

Are we really arguing about an idea as being too conservative?
Who really cares? Plan your own dive, dive your own plan.

At the end of the day, those who choose to dive solo, (SDI trained or not) are undertaking a uniquely personal activity that demands that they rely upon themselves wholly for survival. In this case the individual needs to take complete responsibility for planning and executing every aspect of their dive. As a solo diver you can plan and execute whatever profile using whatever gas management rules that you can cook up, that’s your call. The SDI manual gives you some basic tools that suggest being conservative is a good idea, however, we live in a free country.

You plan it, you dive it. One nice aspect of solo diving is that you come when you choose AND you don’t have to show your ending pressure to anyone.

 

[FritzCat66]

Keep in mind that most divers that take the Solo course are not really looking to go jump in the ocean and cruise around by themselves every dive. Most come to me after they have seen or had bad “insta-buddy” experience and realized that they need to be more self-reliant.

Yes, those guys, photographers, and spearos all seem to be the perfect candidates for a solo cert. That's certainly why I got mine (no instabuddies + photo).

For the actual class and dive work with my instructor, I remember lots of focus on gas planning, calculating RMV and rock-bottom times and so on, although I don't specifically remember rule-of-thirds taught as mandatory in Solo, but then again I was also taking Cavern about the same time, where that was definitely pounded in. Yes, the redundant air source type wasn't specified, but it was taught NOT to be part of the plan at all.

Regardless, in real-world application, solo diving purely open water, no-planned-deco, and mostly drift dives to boot, I do not follow the rule of thirds. I know, a shocker. :shocked2:

The way I see it: I've got 120cf in my main tank, 19cf in my bailout, and ten bazillion cf in my real reserve: the atmosphere. So if I use 100cf of my primary getting back to it, I'm still waaaaaay below using two thirds. :cool2:

 

[LeadTurn_SD]

:huh:

Could someone help me out with this statement?

While I've been given to understand the rule of thirds originated in cave diving, I've heard 'the rule' used in way too many other situations . . .

The "Rule of Thirds" predates scuba diving, by a long time

Mariners used it for determining how much bunker fuel oil, coal, etc., would be needed for a trip (one third out, one third back, one third for "bad weather" or other unexpected conditions); or if underway without a set destination (fishing, etc.), when to "turn back".

Best wishes.

 

[lobstah]

Are we really arguing about an idea as being too conservative?

I think argument is more along the lines of why is it relayed as a gospel, instead of method and reasoning being explained, so students can understand the limitations. I for one would be concerned about instilling "as long as I'm diving thirds I'm fine - my instructor said so" attitude which can be carried over to something where 1/3rds plan would be aggressive. In my opinion divers should own and understand the tools they use.

 

[Jax]

Good Lord, who is saying it was relayed as gospel? I sure as heck don't follow it like gospel?

 

[hudson]

And as it turns out, its successor (1/3 in 1/3 out 1/3 for emergencies) is mega aggressive given buddy diving (1/3 in, sharing gas at max penetration = 2/3 out. No contingency. Better be as fast getting out as you did getting in).

So, one should ask, who is the solo diver reserving that last 1/3 for? The imaginary buddy?

And why on earth is the gas in the pony ignored? The gas is there, right? It doesn't magically disappear when you have an emergency. This whole idea of "don't touch your pony" is for newbies so they don't drain both their backgas and their pony. If you are solo diving, hopefully you aren't a newbie anymore. Do tech divers ignore the gas in one of the tanks? You only need to make sure you always have enough gas in your pony to meet your rock-bottom, that's all.

Basically SDI then claims, if you are entangled or caught in a down current or whatever, you may need about HALF your backgas (you have more "emergency" gas than 1/3 available, since direct ascent is always an option and takes much less gas than getting back to your starting point) PLUS the gas in your pony, which is probably at least 1/4 your backgas. This adds up to MORE gas than you would use on the dive without any emergencies: (1/2+1/4)>2/3.

If you find yourself in such an "emergency", I think you have much bigger issues than the gas available to you. Here's a more sensible plan, IMHO:
1-Gas needed for bottom time (out+in)
2-Gas needed for rock bottom (ascent)
3-Gas needed for handling any reasonable emergencies (and hopefully you won't conclude it's 60CF+)

 

[Jax]

Jeez, Hudson, you can do anything your little heart desires!

Please don't dis the rest of us who like our ultra conservatism!

 

[Jax]

Are we really arguing about an idea as being too conservative?

Who really cares? Plan your own dive, dive your own plan.

Why yes, there seem to be some that are!

on diving your own plan! hbrother:

 

[Blackwood]

Are we really arguing about an idea as being too conservative?
Who really cares? Plan your own dive, dive your own plan.

What we're 'arguing about' is whether it makes any sense.

As lobstah suggested above, an arbitrary rule may be conservative in one application and aggressive in another. Without understanding the basis for the rule, it may be difficult to understand when that door swings.

 

[donhealy]

I say we all just snuba! That way we will never have to worry!!! Oh wait a minute, we may get the line snagged on something so let's also carry a mini tank. I believe in redundancy and prudence but we still have to have some fun down there.

Blackwood is correct. It all depends...... What type of diving, what depth, conditions, etc... 1/3 may be the best for one dive but 40 ft. under the dive boat in warm water, with no current, excellent vis and an emergency tank hung on the safety stop bar does not cry out for ascending with 1000psi. BTW, I dive with a steel 95 at 2500psi so that would be about 800psi.

In all seriousness, If I'm down at 100' I'm looking at my consumption and minutes remaining on my Cobra 3. I'm looking at NDL time, PO2 and where I am in relation to where I should be to surface. I could very well need to follow the 1/3 rule.