Best Mix VS Standard Gasses (split from a GUE fundies course report)

[stuartv]

Hey @_Ralph

My specific question was about a specific scenario (diving in NC) and what a GUE diver would use.

A diver from PADI, et al, with a Nitrox card would take the banked EAN30 and go dive (to as deep as 120'). That is the VAST majority of the actual diving out of Morehead City and Beaufort.

I keep asking because, until @laikabear chimed in, it seemed like nobody would give a straight, simple answer to my (pretty) simple question. You yourself did not answer my actual question at all.

Why did it come up (this time)? Because in the original thread a (apparently) GUE instructor included an off-the-cuff comment that arguing against Standard Gases was dumb. I'm paraphrasing because I don't remember the exact quote and I'm too lazy to go look it up. That is how it translated (to me, anyway). Also, another (apparently) GUE diver chimed in and asserted that in a NC-style scenario, divers using Standard Gases would be able to dive when a Best Mix diver wouldn't (in some specific outcomes of the aforementioned scenario).

When people post statements like that, it makes me want to dig in and have a discussion to seek out the real truth of those statements.

So far, it seems to me that it's not dumb at all for recreational sport divers to NOT limit themselves to Standard Gases.

And, it seems that, in reality, Best Mix divers would NEVER be at a disadvantage (I mean, they/we CAN use Standard Gases if we want, so how could we be at a disadvantage?). And, in some situations (e.g. the reality of NC diving - and other places), the guys limited to Standard Gases would be the ones actually at a disadvantage. Those guys can use TX30/30 and potentially be using some very expensive gas for an 80' dive. Or they can use EAN32 and potentially not dive or be limited in what they can go and see during their dive. Neither seems like as good a choice (to ME) as just taking EAN30 and enjoying whatever dive site the boat is able to take you to (and without spending a fortune on helium).

 

[PullYourselfTogetherMan]

Not all dives are GUE dives, and just having Fubdamentals doesn’t make one a GUE diver ....
_R

Out of curiosity, what would you say makes a diver a GUE diver?

 

[_Ralph]

So EAN30 is what is available? Stick it in a tank and let’s dive!

If that wasn’t allowed, JJ can have all my cards back!

Standard gas/best mix is a topic akin to religion.

They both get the job done, both sides get a great nights sleep and both think the other guys wrong

I prefer standard gases, the GUE gases are thought out (~1.2MOD, <4ATA END, easily mixed from banked EAN32*except 30/30*) and fit my diving with GUE and the TDI/NSS/IANTD certs that I hold.

For me, grab the gas for the depth of the dive, bailout/deco as required and look at stuff, come back up and have a laugh.

It all comes back down the the what if’s. Both sides and wrong and both sides are right. Standard gas and best mix, if a site is shallower/deeper than expected, both strategies suffer based on the same metrics. And why would one base the other on separate metrics?

_R

 

[rjack321]

EAN30 is basically NC standard mix. If I were diving OC I'd just use it and not agonize over getting helium. For those dives I probably would think twice about diving air dil at 120ft in current though. Its pretty dense for those conditions.

Sadly those charters are blown out so often I am reluctant to fly out there to get skunked

 

[johnkendall]

Hey @_Ralph

My specific question was about a specific scenario (diving in NC) and what a GUE diver would use.

A diver from PADI, et al, with a Nitrox card would take the banked EAN30 and go dive (to as deep as 120'). That is the VAST majority of the actual diving out of Morehead City and Beaufort.

I keep asking because, until @laikabear chimed in, it seemed like nobody would give a straight, simple answer to my (pretty) simple question. You yourself did not answer my actual question at all.

Why did it come up (this time)? Because in the original thread a (apparently) GUE instructor included an off-the-cuff comment that arguing against Standard Gases was dumb. I'm paraphrasing because I don't remember the exact quote and I'm too lazy to go look it up. That is how it translated (to me, anyway). Also, another (apparently) GUE diver chimed in and asserted that in a NC-style scenario, divers using Standard Gases would be able to dive when a Best Mix diver wouldn't (in some specific outcomes of the aforementioned scenario).

When people post statements like that, it makes me want to dig in and have a discussion to seek out the real truth of those statements.

So far, it seems to me that it's not dumb at all for recreational sport divers to NOT limit themselves to Standard Gases.

And, it seems that, in reality, Best Mix divers would NEVER be at a disadvantage (I mean, they/we CAN use Standard Gases if we want, so how could we be at a disadvantage?). And, in some situations (e.g. the reality of NC diving - and other places), the guys limited to Standard Gases would be the ones actually at a disadvantage. Those guys can use TX30/30 and potentially be using some very expensive gas for an 80' dive. Or they can use EAN32 and potentially not dive or be limited in what they can go and see during their dive. Neither seems like as good a choice (to ME) as just taking EAN30 and enjoying whatever dive site the boat is able to take you to (and without spending a fortune on helium).

I'll bite again. You have manufactured a borderline case where you have specifically picked a depth between gases on the atandard gas list. Of course it's not going to be optimal.
However, if a fundies grad is sticking to their training then they're not diving to 120ft anyway, as the GUE limit without helium is 100ft, and they're not qualified to use helium.
It's just like a PADI diver that doesn't have a qualification for below 100ft.

I said that arguing against standard gases showed a potential attitude problem (as that was the question asked originally), you've not done anything in this thread to convince me otherwise, and you didn't like my answers to PMs. I'm not sure what you want us to answer here. If I was diving in that situation, I'd either take gas suitable for 120ft, or I'd tell the boat I wanted a max of 100ft. It's something I would sort out in advance of paying any money. It happens all over the world that the fall back option is shallower, but I've never been anywhere where the fall back is a deeper dive.

 

[JohnnyC]

The thing with best mix is that it's only best mix for a specific depth. If plans change, that mix may no longer be optimal.

Standard gases are rarely ever the most optimal for each scenario, however they are good enough for a broad range of scenarios that the other benefits outweigh the marginal loss in optimization.

Obviously there are situations where using something other than standard gases works better. If your diving scenario fits within those situations, great. If it doesn't, best mix covers a wider variety of scenarios safely. Using single use case scenarios to try and disprove a much wider data set is the wrong way to go about it.

I think a lot of times we get hung up on trying to eek out the very last bit of performance, we want the longest NDL, we want the optimal PO2, etc. When situations allow, it's great to be able to accomplish that. However when situations don't allow, accepting something other than the most optimal often pays in other ways.

That NC diving specifically benefits going off standard gases shouldn't be seen as a condemnation of standard gases. Standard gases shouldn't be seen as a definitive condemnation of best mix. Standard gases are generally easier to acquire worldwide than best mix, and they cover a much wider range of potential scenarios. It's two different definitions of optimal, and neither one is more or less "right" than the other. It's just two ways to skin a cat, both have their pros and cons.

 

[stuartv]

So EAN30 is what is available? Stick it in a tank and let’s dive!

If that wasn’t allowed, JJ can have all my cards back!

Standard gas/best mix is a topic akin to religion.

They both get the job done, both sides get a great nights sleep and both think the other guys wrong

I prefer standard gases, the GUE gases are thought out (~1.2MOD, <4ATA END, easily mixed from banked EAN32*except 30/30*) and fit my diving with GUE and the TDI/NSS/IANTD certs that I hold.

For me, grab the gas for the depth of the dive, bailout/deco as required and look at stuff, come back up and have a laugh.

On that, we are definitely in agreement!

It all comes back down the the what if’s. Both sides and wrong and both sides are right. Standard gas and best mix, if a site is shallower/deeper than expected, both strategies suffer based on the same metrics. And why would one base the other on separate metrics?

_R

To me, shallower/deeper than EXPECTED is not a factor. If you end up with a depth deeper than you expected, you didn't plan your dive properly. Or you are doing exploration diving....

The issue is when you know what to expect - you know what the possibilities are. So, you prepare for the deepest site that is on the list of possibilities.

And that is where a limited selection of gases is not as good as an unlimited selection of gases. I don't really see how anyone can dispute that. Limits are more restrictive than no limits. Seems pretty simple, to me.

If GUE Diver and BM Diver are on the same boat, going to a site that is 120' and knowing that conditions COULD cause them to divert to an 80' site, the BM Diver is going to have EAN30 and the GUE Diver is going to have TX30/30(? if he can get it). I'm calling that Advantage BM Diver. You may feel that Helium is a requirement for a 120' dive. In that case, BM Diver can certainly use that - so no disadvantage for the BM Diver. In that case, they are equal.

If GUE Diver and BM Diver are both on a boat going to a site that is 80', knowing that conditions COULD cause them to divert to a 40' site, the BM Diver might choose EAN36. The GUE Diver will have EAN32. It seems clear to me that the BM Diver has an advantage there.

So, sometimes the Best Mix Diver has an advantage. But, the BM Diver NEVER has a disadvantage (because, if the GUE Diver's gas choice is actually preferable, the Best Mix Diver can use it, too).


Personally, I don't care what you dive. If we dive together, I have no problem using a Standard Gas, if that's what you want.

What I DO care about is the divers who come along and read threads like this - the ones who don't really know which way is up when it comes to Standard Gases and Best Mix. When those divers read a statement, posted by "an Instructor", that implies that there is no rational debate against Standard Gases being best, and they read a statement from an experienced diver that says that using Best Mix means you might sometimes be stuck sitting on the boat while the Standard Gas people are on the bottom, I want those divers to read the counterpoint to those statements.

There ARE valid points against always sticking to Standard Gases. There is NO reason that Best Mix divers should ever be sitting on the boat while the Standard Gas divers are diving. The posts that suggest otherwise are simply false.

In my opinion.

 

[_Ralph]

@stuartv so why the different metric against standard gas?

It doesn’t matter between standard gas and best mix, if you’re dropped on a site that’s deeper than the gas you brought?

I can actually think of a few places where your statement would be false above.

Say a 36m/120ft dive plan. You pad in some contingency, so 39m/130ft and bring EAN25. I’d bring 21/35. Moment of sometime before splashing, we end up wanting to check out something that’s at 150ft/45m for a duration (ship feature, critter, mermaid, Spanish gold). My gas would let me, but you’d violate yours (keeping the metrics as close as possible 1.2MOD)

I’m not saying for or against, rather just playing devils advocate against your last two pragraphs. I too want the reader, any reader to have the full story from both sides...


Additionally,
What’s YOUR downside to diving a helium mix shallower? You haven’t explained it. Why in your example above, is the 30/30 diver the lame duck?

I routinely will dive 30/30 shallow on dives due to requiring the helium. Dives where there is current, lots of task loading and hopefully completing a goal. Would EAN36 or leaner be a suitable gas for the depth (alone)? Sure, but it probably won’t be enjoyable to get the same result out of the dive.

_R

 

[stuartv]

I'll bite again. You have manufactured a borderline case where you have specifically picked a depth between gases on the atandard gas list. Of course it's not going to be optimal.
However, if a fundies grad is sticking to their training then they're not diving to 120ft anyway, as the GUE limit without helium is 100ft, and they're not qualified to use helium.
It's just like a PADI diver that doesn't have a qualification for below 100ft.

I said that arguing against standard gases showed a potential attitude problem (as that was the question asked originally), you've not done anything in this thread to convince me otherwise, and you didn't like my answers to PMs. I'm not sure what you want us to answer here. If I was diving in that situation, I'd either take gas suitable for 120ft, or I'd tell the boat I wanted a max of 100ft. It's something I would sort out in advance of paying any money. It happens all over the world that the fall back option is shallower, but I've never been anywhere where the fall back is a deeper dive.

I would respectfully suggest that examples that always fit within one row of the Standard Gas chart are where examples are being manufactured.

The NC case is not some made-up theoretical thing.

In NC, lots of people want to go to the U-352. That dive is about 110'. It would not be unheard of at all for the boat to aim to go there, find out that conditions are bad there and go to, for example, the Atlas, which is 125 to the very bottom.

They can do that because everybody goes out prepared for the deepest option that is on the menu - and the Atlas is probably the deepest option on the rec boat charter menu. So, you may not have been anywhere with a fallback that is deeper, but that doesn't mean it doesn't happen.

Also, if you assume the fallback sites will always be shallower, then Best Mix will always be better - except in the case where the Best Mix works out to be the same as the Standard Gas for the planned site - in which case they are, well, the same. It was another GUE diver who originally asserted that Best Mix would potentially leave you sitting on the boat while the SG dives were diving at a (deeper) alternate site.

Also, I had no problem with your answers in PM. I just thought our discussion was done. I wasn't going to change your mind. You were not convincing me that what you said about Standard Gases is valid. The point in continuing the conversation here in a public forum was to air both sides fully, for the benefit of anyone who may come along and read this later.

As far as I can tell, for NC diving, EAN30 (a non-Standard Gas) is better, easier, and less expensive than using the prescribed GUE gas.

As far as I can tell, if I were going (on a recreational charter boat) out of Key Largo, the target site might be 90 feet (a Molasses Reef drift), with an alternate of 40 feet (a non-drift dive at a shallower spot on Molasses). EAN36 is a better choice there than the GUE Standard Gas (EAN32).

It seems to me that, for recreational sport diving, the examples of when a Best Mix approach yields better results for the diver might significantly outnumber the examples where they are equal. And there is never a time when limiting to a Standard Gas is actually better - because if it's better, the Best Mix diver can use it, too.

As for not being sure what I want you to answer, well, I don't know how many more different ways I can say "if you strictly adhere to GUE training, what gas would you bring on the boat on a NC chart boat (parameters previously given)?"

I think it is settled that you would bring TX30/30 or EAN32. I don't think I'm asking anything else for you to answer...? Unless you can explain how either of those would be better than bringing EAN30 (given the previously described, real, actually-how-it-is, parameters).

 

[stuartv]

The thing with best mix is that it's only best mix for a specific depth. If plans change, that mix may no longer be optimal.

Right... That's why your pre-dive planning would include assessment of contingencies and your best mix selection would be whatever will work for the worst-case scenario.

I'm starting to get the impression that the real GUE protocol is not "GUE always uses Standard Gases". It is starting to sound like the protocol is "GUE has a list of default gases. We will use those unless there is some good reason to use something different."

@stuartv so why the different metric against standard gas?

It doesn’t matter between standard gas and best mix, if you’re dropped on a site that’s deeper than the gas you brought?

I can actually think of a few places where your statement would be false above.

Say a 36m/120ft dive plan. You pad in some contingency, so 39m/130ft and bring EAN25. I’d bring 21/35. Moment of sometime before splashing, we end up wanting to check out something that’s at 150ft/45m for a duration (ship feature, critter, mermaid, Spanish gold). My gas would let me, but you’d violate yours (keeping the metrics as close as possible 1.2MOD)

I’m not saying for or against, rather just playing devils advocate against your last two pragraphs. I too want the reader, any reader to have the full story from both sides...


Additionally,
What’s YOUR downside to diving a helium mix shallower? You haven’t explained it. Why in your example above, is the 30/30 diver the lame duck?

I routinely will dive 30/30 shallow on dives due to requiring the helium. Dives where there is current, lots of task loading and hopefully completing a goal. Would EAN36 or leaner be a suitable gas for the depth (alone)? Sure, but it probably won’t be enjoyable to get the same result out of the dive.

_R

If we're diving together, why would you plan for the possibility of 150' while I only allowed for 130 in my plan? Personally, I would never do that. If we're diving together, I would use the same gas as you. In that scenario, I might request EAN25, but if you say you really want 21/35, then I'd dive that, too. I'm easy.

And, during our planning if we decide that there is some chance we might want to go to 150', then sure, I'd pick a gas for that. But, if we know that the bottom is 125' at the deepest site on our list of "even possibles", then I would vote for something like EAN30. If we (keyword: we) plan for a max of 130 and we get out and find there's a spot that we'd like to check out that's 150, well, too bad for today! Plan for it and come back another time.

If we're going out on a commercial charter boat, I'm going to ask ahead of time "what is the max depth you'll take us to?" I'll choose my gas accordingly (most likely being to use whatever they bank). If they take us out and end up taking us somewhere deeper than what they told me ahead of time and I can't dive, then I'm going to have words with that charter operator (and a refund).

The downside to 30/30 for a recreational reef dive at 80' is simply cost. I would feel like it was a good chunk of money spent for no practical benefit. But, I was stipulating common, ordinary rec charter boat dives. I interpret those as "easy dives". If you want to change the parameters to include work and task-loading, then my choice of gas might change. (though I really cannot see myself ever using He for an OC dive to less than 100'. If it's that shallow and that much work that I would think I needed helium, I probably don't want to do that dive anyway.)