Next step for longer bottom times on deep dives?

[wetb4igetinthewater]

But are you implying that anyone who doesn't dive Trimix at130 feet is ignorant? Hard to figure out the message, but that's what it sounds like...

No, I don't think they are necessarily ignorant. If they say they understand that they understand the increased risks with narcosis in an emergency situation when exceeding a density of 6.2 g/L and accept those risks, I'm good with that. I'm not good with people who dismiss the science. I have had a conversation with one individual who dismissed Dr. Mitchell as "just an occasional diver" who trusts the divers at his former dive center who "regularly" dive to 70 meters or more on air. A friend of mine in Europe is friends with a number of people who died diving that way. And they don't switch to trimix until 100 meters. Now obviously there is a big gap between 40 and 100 meters on air. However, the risks increase dramatically above a gas density of 6.2 g/L. That's ultimately my point. It does come down to risk assessment, and we all assume different levels of risk. But I'll never understand or respect those who dismiss science.

 

[jf3193]

Advanced nitrox/deco procedures. No need for trimix if you're already comfortable on those wrecks. If you plan on going past 130' regularly then mix may be something to consider after a while.

thanks! Most of the 'deep' stuff I do tends to be in the 90-110 range. Nothing that can't be done on a good EAN, but always wishing I had more, since I have really good air consumption, even at those depths.

 

[jf3193]

When do you start getting narced? I’d suggest considering Adv Nitrox/Helitrox with TDI. You don’t have to use helium, but it’s good to have the option if you want to. That combo gets you down to 150ft and 35% helium. Other SBers have been very bummed after the fact when they found out they could have added Helitrox and didn’t. They didn’t know about the option or instructors didn’t tell them about it. Helitrox takes the place of Deco Procedures. You still do the DP bookwork, but don’t get the cert. It shouldn’t be an extra dives (there’s one instructor on SB who takes extreme pride in going way beyond standards) and additional class fees shouldn’t be too much, plus gas costs. The Trimix book is the Helitrox text.

I don’t know where in the US you are, but even with helium being $4-5/cft in my area of the Great Lakes, I’m still doing Helitrox and will dive it when needed. Narcosis is a very personal thing and I’m in a bad way at 130ft. It’s as much as a safety factor for me, as being able to remember the deeper wrecks I’ll dive!

it usually kicks in around 110 for me so that I notice. Id still like to stay 'longer' in that 90-100 range than the EAN 30-32 allows.

 

[jf3193]

When do you start getting narced? I’d suggest considering Adv Nitrox/Helitrox with TDI. You don’t have to use helium, but it’s good to have the option if you want to. That combo gets you down to 150ft and 35% helium. Other SBers have been very bummed after the fact when they found out they could have added Helitrox and didn’t. They didn’t know about the option or instructors didn’t tell them about it. Helitrox takes the place of Deco Procedures. You still do the DP bookwork, but don’t get the cert. It shouldn’t be an extra dives (there’s one instructor on SB who takes extreme pride in going way beyond standards) and additional class fees shouldn’t be too much, plus gas costs. The Trimix book is the Helitrox text.

I don’t know where in the US you are, but even with helium being $4-5/cft in my area of the Great Lakes, I’m still doing Helitrox and will dive it when needed. Narcosis is a very personal thing and I’m in a bad way at 130ft. It’s as much as a safety factor for me, as being able to remember the deeper wrecks I’ll dive!

South Carolina. Looking to get into the North Carolina wrecks more frequently, which are often in that 90-120 range.

 

[jf3193]

I get it, the OP just wants to do this safely:

View attachment 654724

No hour or more DECO, no crazy depths...

We have some great wrecks here in and around the limits of recreational diving that you just can't get a nice dive on without doing a small bit of DECO. Learning to do it safe makes for some great experiences. I do an annual trip to some fantastic 1800's and early 1900's wrecks that include recreational divers. To watch them fixate on their DC, and race the clock to stay out of DECO is silly....

Thats really what I was trying to find the solution for, I guess I just wrote it out incorrectly. Im still wanting to stay in 'recreational range' just extend my bottom time somehow.

 

[Marie13]

it usually kicks in around 110 for me so that I notice. Id still like to stay 'longer' in that 90-100 range than the EAN 30-32 allows.

Mine kicks in about 115-120'. You're going to need deco training to stay longer at those depths.

 

[Blackfrogfeet]

I think if you can easily do the same dive on OC a rebreather is not the right tool for the job. It’s a lot harder to get hypoxic, hyperoxic, or hypercapnic on OC than it is on CCR.

Also, at those depths CCR and OC will have very similar decompression obligations,

I see guys say that a lot but isn't that mentality a little bit of a hold over from the days where CCRs were a lot less reliable, a lot higher risk, and the only people using them were doing exploration dives?

In my neck of the woods, I see CCR guys doing rec profiles and basic tec profiles (40-50m with 30-40min deco) all the time. Of course those dives could be done on OC very easily. I see guys diving CCRs on 15m/60 minute rec dives a lot, but they need to be doing those dives with their CCR so they can maintain proficiency so that when they go do a 75m dive, their skills are sharp.

I'm going CCR very soon, and the primary driver for that is Helium, but I fully intend to dive my rebreather on most of my rec dives as well to get hours on the unit, and avoid maintaining unnecessary sets of doubles and regs that I won't need because I'll have a CCR. And even on rec dives, 5lb of sorb is cheaper than a doubles nitrox fill ($35) so it will save me a lot in the long run.

 

[ginti]

One thing I have learned in my own professional training is to respect experts and listen to their recommendations. When it comes to decompression science, I absolutely will follow whatever @Dr Simon Mitchell recommends.

Like it or not, the more "scientific" approach is not to follow one person's recommendations. Instead, follow the entire scientific community. A single individual, even if very knowledgeable, can make mistakes. The entire community too, but it's more unlikely.

Should be a regular occurrence but when we hear of them it's normally unhealthy, overweight, inexperienced AND unlucky divers that have isses. Gas choice is rarely if ever mentioned unless its an idiot doing a 300' dive on an Al80 of air.

The fact that it is not mentioned doesn't mean that it didn't play a role. Maybe all of these people would be alive if they were breathing trimix; who knows? The only thing that we know for sure is that the scientific community recommends avoiding narcosis. And scientists of today know more than you, more than me, and more than the people who made reports on the deaths you mentioned.

In this case though, since the far majority of the dives we're discussing are done on air or nitrox and historically have been, the " deviants " are those who seem to lack the intellectual abilities at depth to dive like the rest of the world and need helium to do so. No shame but I certainly would be thumping my chest about this inability.

Did you ever think that these dives have been historically done in air/nitrox just because 20-30-40 years ago scientists knew less than today, and were giving recommendations according to their more limited knowledge? And that limited technology also played a role in those choices?

 

[Wibble]

Good evening gang.
Im researching the idea of stepping up into the tech world. Ive done several deep wrecks over the years, and I'm often wishing I had more bottom time 90-130 ft range eats up NDL even on Nitrox.
what would be a good starting point to get more bottom time out of this dive range? I often dive the Spiegel grove and the Duane down in the keys, and I want to get into the North Carolina wrecks, but id love to figure out what step I need to have better bottom time. I have good air consumption, but still can't win that fight against NDL, even on Nitrox.
Id love to be able to truly explore, staying down 45+ on these dives at this range. I see several options for classes that are 'tech', but not sure where to start. PADI certified, but TDI or other outfits are just as open to me.

any thoughts?

Rebreather.

Large entry cost in terms of finance and commitment -- think motorcycle. Once over that, it's amazing, cheap to run and flexible.

Failing that it's a twinset, stages and learning decompression procedures.

Other agencies factor in your future, not PADI.

 

[happy-diver]

Id still like to stay 'longer' in that 90-100 range than the EAN 30-32 allows.

Well, dive 36