A DIR spin on an old question

[Web Monkey]

Again, I'm not diving to air on 130. I did once and won't do it again. You really do not get what I was asking.

You're looking for a hardware solution to a human problem.

You want to be "safe" or at least "safer" when diving with insta-buddies. In this case, a pony is better than nothing, but is certainly not enough. It's like saying "My car doesn't have an air-bag, can I use a throw-pillow instead?". Well, sure you can. It's better than nothing, just not a lot better.

There is no hardware that will accomplish what you're looking for.

Terry

 

[Adobo]

The thing is, even if you are able to solve the gas redundancy problem, you still wouldn't have all the things that a good teammate brings to the table.

Some examples:
- if you get tangle in some fishing line or kelp, will that pony bottle be able to help you?
- if you are not sure about the navigation back to your exit point, does the pony bottle know how to read the compass?
- do pony bottles know how to spot gear problems such as a wing that has sprouted a leak? do pony bottles know what properly routed hoses look like? Can a pony bottle help you untangle hoses?

If you follow some simple rules, your chances of needing that redundant gas is virtually zero. Whereas a good team mate will play a critical role in every dive to proactively avoid problems or address minor issues before they escalate into big problems. (They haven't invented a pony bottle that does that, have they?)

Ok, so DIR divers don't dive with ponies, that I know.

Nevertheless, I've seen people on this board recommending to have air in a slung pony, even if the back-gas is Nitrox. I've been thinking about this for awhile, and I've never quite understood why if my buddy and I are breathing Nitrox I should put a less "efficient" gas in the slung bottle.

Is there any real reason to not put the same mix in the pony bottle and the back-gas?

Just to clarify to make this easier: 1) I'm not trying to accelerate deco on the safety stop 2) it is just for reserve on dives with questionable/insta buddies 3) I haven't dived with the tank yet as I haven't set it up to sling yet & 4) I'll be getting my Nitrox cert soon, I'm diving air now

So where's the DIR spin? Well, to be honest, I'm not looking for the exact DIR answer, but I'm looking for the advice of DIR-minded divers.

 

[Dtaine]

Well I'll say thanks to everyone, perhaps I should have posted elsewhere but what's done is done. I'm working on the buddy issue, I'll probably be doing a few dives with deepstops once I get back to Miami after the holidays, and I'm working on setting up dives with others as well. For the insta-buddy dives, the non-DIR ones, I'll use air for now and 32% after I get the nitrox cert; for the dives with DIR trained buddies obviously I won't need it, but it should work good later as a stage/deco bottle once I'm at the level to use it for that purpose.

 

[Tortuga68]

So, Mr. best mix, riddle me this: What would the best mix be for a 30 foot dive? And since this is the DIR forum don't say air

Why would I say air is best mix for a 30 foot dive anyway?? 'Best mix' = the mix that gives the desired PP02 limit at the maximum depth planned for the dive, so the answer to your question would depend on the desired PP02 for that dive

The OP I was responding to suggested using a particular mix and then staying shallower than the limit of that gas; therefore, it's not the 'best mix' for that dive by any definition of best mix that I've heard; if you have a different defintion, please feel free to share it rather than posting subjective math questions

I don't get what your point is, or why you chose to ask the question in that manner

IMHO anyone that has done a nitrox course (intro or advanced) should be familiar with the formula for calculating best mix, it isn't something I made up just to start an argument with you


Blackwood, I'd be interested to hear why 'best mix' doesn't apply to DIR?

 

[coldsmoke]

Blackwood, I'd be interested to hear why 'best mix' doesn't apply to DIR?

Best mix doesn't apply to DIR because the benefits of standard gasses out weigh the benefits of best mix.

Hunter

 

[b1gcountry]

The concept of "Best Mix" does have a definition. Even if you don't proscribe to it's use, you can benefit from understanding the benefits and drawbacks. Using "Best mixes" is not DIR, but understanding "Best Mix" is very DIR.

Tom

 

[Blackwood]

Blackwood, I'd be interested to hear why 'best mix' doesn't apply to DIR?

Because "best mix" as it is commonly understood (and as you mentioned above) calls for a different gas for each planned maximum depth, the goal being to dive with the absolute highest "allowable" oxygen content.

The DIR methodology calls for a specific set of gases for specific ranges of depth. We won't use different gases for 70 or 80 or 90 feet. We'll use 32%.

Standard gases allow us to really get to know our profiles since they're similar for each and every dive (the only decompression variables in a given depth range are time and average depth, not the gas).

Further, we consider oxygen to be a narcotic gas, and thus it's not necessarily in our best interest to spike it even to the max allowable PO₂. That clarity of mind may cost a little extra deco, but that's a small price to pay.

 

[lamont]

this is getting a little bit off topic....

i can split this out if we really need to do best mix vs. standard gases again...

 

[Rainer]

Please move this thread.

 

[Dtaine]

this is getting a little bit off topic....

i can split this out if we really need to do best mix vs. standard gases again...

Please move this thread.

Rather than moving it, which if not edited would certainly cause confusion in whatever forum it's moved to, I would think splitting it and then closing the one thread off, leaving the "best mix vs. standard gases" part open might be best.

Do what you think is best Lamont.