Recreational Trimix Diver course with Techs Mex Divers, Part I

[TSandM]

Reg, looking at your description of the dive you did and want to do again, I'd say that it's a perfect 25/25 dive, and you'd enjoy it a ton more on that mix. I've been VERY pleased with the difference even that much helium has made in my dives in the 120 range -- not so much, any more, while I'm down there, but my RECALL is so much clearer and fuller when the dive is over. Although I don't pay Canadian He prices, it's certainly well worth it to me to obtain the 25/25. (Although, I will admit, 25/25 gets you into deco fairly fast, and doing backgas deco in cold water VERY quickly makes accelerated decompression attractive, and then you end up in a tech class anyway.)

 

[rjack321]

Rumbo you are doing 1:4 RD profiles (300ft)??

Instead of blaming obtuse ICD principles you could also say that high N2 gases at depth (e.g. 70-120ft) don't really enhance total offgassing since the N2 loading in that range ends up being significant. N2 that you eventually have to eliminate later. Better to keep the low solubility He %age high. None of which is really relevant to the OP's 120ft, ~10min MDL dive.

So Rumbo following RBW's advice I take it you don't do backgas breaks, at e.g. the 30ft stop and every 10-15mins during the O2 time?

 

[rjack321]

Reg, looking at your description of the dive you did and want to do again, I'd say that it's a perfect 25/25 dive, and you'd enjoy it a ton more on that mix. I've been VERY pleased with the difference even that much helium has made in my dives in the 120 range -- not so much, any more, while I'm down there, but my RECALL is so much clearer and fuller when the dive is over. Although I don't pay Canadian He prices, it's certainly well worth it to me to obtain the 25/25. (Although, I will admit, 25/25 gets you into deco fairly fast, and doing backgas deco in cold water VERY quickly makes accelerated decompression attractive, and then you end up in a tech class anyway.)

Uhuh, and doubles are mighty attractive at 120ft in cold water too...

 

[Reg Braithwaite]

Reg, looking at your description of the dive you did and want to do again, I'd say that it's a perfect 25/25 dive, and you'd enjoy it a ton more on that mix.

Just out of curiosity, is 25/25 a DIR standard gas? Or is it a heresy expounded by the Fallen Archangel AG? I was under the impression that the "official" Recreational Triox gas was 30/30, which is fine for balmy caves with perfect viz, but I was hoping to be a little more conservative with my PPO₂ in Ontario conditions, so 25/25 has some attraction despite the possibility of it being a "stroke" gas... Sorry, I'm hijacking my own thread...

(Although, I will admit, 25/25 gets you into deco fairly fast, and doing backgas deco in cold water VERY quickly makes accelerated decompression attractive, and then you end up in a tech class anyway.)

Well, remember that the Forest City is a rare (for me, anyways) multi-level dive. It's lying on a slope, stern-down with the broken-up bow at 55', the stern rail at 135', and the mud at 150'. On a minimal deco dive you need only spend a few moments at the stern rail, I found the most amazing thing was actually looking up at the wreck from the bottom into the sunlight.

On a normal wreck "survey" you would perform a square profile, swimming the length of the wreck a few times. On this dive you simply rise slowly from stern to bow, stopping awhile at 108' to spend some time with the boilers. When you get to the bow, you may be pleasantly surprised by the average depth.

The next issue is the temperature. It's true, the stern is cold. But in good conditions there are two thermoclines present. You're doing minimum deco up above the second and then first thermocline, so as your deco progresses you move into warmer water. I strongly suspect I'll have invested in a suit inflation bottle before I do this dive on Trimix, of course.

Uhuh, and doubles are mighty attractive at 120ft in cold water too...

One of the reasons I have been able to purchase used gear at reasonable prices is the relentless drive for Ontario tech divers to upgrade their gear. My plan is to stay a few steps behind everyone, buying their cast-offs for cheap.

Please keep telling everyone they need doubles and rebreathers, and that they should sell their singles gear to me in order to finance it all. It's a great help!

 

[rjack321]

Just out of curiosity, is 25/25 a DIR standard gas? Or is it a heresy expounded by the Fallen Archangel AG? I was under the impression that the "official" Recreational Triox gas was 30/30, which is fine for balmy caves with perfect viz, but I was hoping to be a little more conservative with my PPO₂ in Ontario conditions, so 25/25 has some attraction despite the possibility of it being a "stroke" gas... Sorry, I'm hijacking my own thread...

30/30 is the GUE gas. Its now has a recommended MOD of 100ft. Its intended for use in (high flow) North FL caves were the He fraction keeps your CO2 under more control, moreso than to control N2 narcosis per se. The O2 is high to keep it a -20% EAD gas. Outside those conditions its utility is limited.

25/25 is a West Coast (California to BC) gas that is used in the 90-130ft range to minimize N2 narcosis and improve decompression while maintaining reasonable ppO2 levels. Hasn't caught on all that much elsewhere.

The next issue is the temperature. It's true, the stern is cold. But in good conditions there are two thermoclines present. You're doing minimum deco up above the second and then first thermocline, so as your deco progresses you move into warmer water. I strongly suspect I'll have invested in a suit inflation bottle before I do this dive on Trimix, of course.

regardless of thermocline, do NOT use He in your suit inflation. Even in 79f water it gets colds really fast.

One of the reasons I have been able to purchase used gear at reasonable prices is the relentless drive for Ontario tech divers to upgrade their gear. My plan is to stay a few steps behind everyone, buying their cast-offs for cheap.

Please keep telling everyone they need doubles and rebreathers, and that they should sell their singles gear to me in order to finance it all. It's a great help!

Doubles are not something you wanna just strap on and jump into 130ft with.

JTivat alluded to this way back on post #2... Do you think you're suitably trained for the conditions and equipment you'll encounter+need/use at home?

 

[Reg Braithwaite]

Doubles are not something you wanna just strap on and jump into 130ft with.

Somehow I am not making myself clear. I do not dive in doubles, nor will I dive in doubles in the foreseeable future. What I do is buy singles gear from people who upgrade to doubles themselves. There will probably be an upgrade to Y Valves between here and August, but that is a story for another paycheque or two.

Do you think you're suitably trained for the conditions and equipment you'll encounter+need/use at home?

What I think is that this particular course is only a very small, almost inconsequential part of a training progression I have mapped out for myself. I will be back in Tobermory the first week in August. A lot of things have happened as part of my training progression since I was there last August, and a lot of things will happen between now and this August.

This course has almost zero contribution to skills even if my home waters resembled the training conditions. I can't lay my hands on the exact wording, but I believe that IANTD explicitly says that the course does not train you to dive at depth, it trains you to dive Trimix to whatever depth you are already trained to dive. Likewise, Oliver was up front that the two dives are "experience" dives, much like the oft-maligned experience dives in the PADI AOW program. They are not skills development dives.

Oliver did not promise to teach me OOG swimming, or air sharing ascents, or deploying a bag and line, or making one minute stops. He promised to fail me if I failed to show up and demonstrate them. Now, I am not saying that I showed up ready to dive the Forest City to my satisfaction, there is lots more training and instruction to take place between now and then. But I am saying that I do not think this course did anything to give me skills I need to execute this dive safely with the equipment I have selected.

The only contribution to my ability that I think this course will provide is to give me a clearer head at depth which might make me better able to use the skills I acquire through other means. So it is part of my program, but hardly a foundation or even a critical mechanism. As it happens, it was convenient to do this course on my holiday.

I also considered some in-water training with German or Zero Gravity, however I discarded this idea for two reasons: First, I think I would get more benefit practicing skills in my dry suit, hood, gloves, and so forth. Second, the season does not really get going up here until the May 24 week-end (hardy ice divers excepted, of course). So if I went and took Cavern or GUE-F in Mexico, I wouldn't get a chance to reinforce what I learned for another two months.

Under the circumstances, I elected to get the math-y stuff done in Mexico and I will work on personal skills up here this Summer.

I hope this allays your concern that I might think a Recreational Trimix card is a ticket to dive deep, cold, and silty

 

[TSandM]

Richard's a worry-wart.

From reading your posts for over a year, I'm not real worried about you throwing yourself into something you shouldn't be doing. Still, his point about redundancy below 100 feet is worth mulling over, especially if you don't have a strong team to dive with (and I don't know if you do or not). GUE teaches Rec Triox in a single tank, still, so even those guys think that some of these shallow mix dives are reasonable to do without doubles. An H valve might be a reasonable compromise. Tank neck o-rings don't fail during a dive very often, and everything about diving is risk assessment and risk acceptance.

 

[rjack321]

Personally I would skip the Y-valve. At least around here, they have pretty much fallen out of favor as not particluarly valuable, although they are better than H valves (with goofy orientation of the knobs IMO).

So I'm guessing this is "just" a card to get you some He in your mix and your buddies will be diving single tanks of nitrox?

(I had a better discussion of who you were going to use this gas etc. at home with your existing buddies but lost it and I'm not all that keen on retyping it)

 

[rjack321]

Richard's a worry-wart.

From reading your posts for over a year, I'm not real worried about you throwing yourself into something you shouldn't be doing. Still, his point about redundancy below 100 feet is worth mulling over, especially if you don't have a strong team to dive with (and I don't know if you do or not). GUE teaches Rec Triox in a single tank, still, so even those guys think that some of these shallow mix dives are reasonable to do without doubles. An H valve might be a reasonable compromise. Tank neck o-rings don't fail during a dive very often, and everything about diving is risk assessment and risk acceptance.

I guess so. I dive to 100ft-ish on singles. And I don't fault anyone else for doing so. I am more curious how this "no skill-required card" is going to fit into dives/buddies/plans at home. e.g. the 21/35 diving buddies.

 

[Reg Braithwaite]

Personally I would skip the Y-valve. At least around here, they have pretty much fallen out of favor as not particluarly valuable, although they are better than H valves (with goofy orientation of the knobs IMO).

Thanks for the tip, although (restart hijack mode) I have no interest in going below the second thermocline without a redundant first stage. Let's first establish that I am not doing true overhead diving. I can live with the necessity of breathing buddy's gas if my neck o-ring fails. What I can not live with is the following scenario: My buddy comes to me for gas. I donate the long hose and switch to my backup. Under the additional flow caused by two people breathing under stress in the cold, my first stage starts free-flowing. Now we have a problem.

I know that planning for two failures is considered paranoid. However, the possibility of two failures is only remote if the two are statistically orthogonal. In the case where I have a single regulator and I am the donor in cold water, the possibility of two failures is no longer insignificant. Then you get into a discussion about doubles, and the usual rationalization is "If you're going to dive doubles eventually any ways, you might as well start now."

For reasons that aren't particularly relevant to a Rec. Trimix trip report, I am not going to dive doubles eventually any ways, so I have decided to be that guy diving Y valves this season. It solves the problem of donating in cold water, which is about being a good buddy.

So I'm guessing this is "just" a card to get you some He in your mix and your buddies will be diving single tanks of nitrox?

(I had a better discussion of who you were going to use this gas etc. at home with your existing buddies but lost it and I'm not all that keen on retyping it)

I don't want to get into a discussion about what other people are going to dive. I've talked to people about this dive, I've had expressions of interest in doing a minimal deco dive on this wreck, but nobody has plunked down money to reserve a seat on the boat yet, much less analyzed gas with me. We'll see what they do when the time comes.

For now, this is a tool in my tool box.