Is Open Circuit Trimix dying a slow death?

[doctormike]

Logistics plays a part too, in that you can easily do multiple dives on CCR with a set of resources you can take with you without having to visit a fill station, and 1 dil mix will cover a multitude of depths/dives subject to it's MOD under CCR gas planning.

Yes, exactly. Leaving aside the other reasons for going CCR, it's great for tech divers in urban areas without cars (I live in NYC and dive with a lot of those people).

Two 3L bottles fit in a messenger bag, you can get all of your gas for a weekend of diving using mass transit, with the fills being done while you go for coffee (I just did that yesterday).

As opposed to filling two sets of doubles and a few deco bottles, which you will have to get to the fill station by car, and then make another trip to pick them up once they are done.

You don't have to worry so much about what is in your tanks in terms of planning. If you put a lot of expensive trimix in a set of doubles and your deep dive gets blown out, you aren't going to want to waste it on a shallow consolation dive.

And finally, you are much more likely to use some helium on mid range dives, giving you a bit of a narcosis advantage. If you bank a light mix for your dil, you might as well use it for all of your dives, it's not that much more expensive than air.

 

[Marie13]

This has been interesting. I’m doing Helitrox with AN/DP next summer.

 

[rddvet]

This has been interesting. I’m doing Helitrox with AN/DP next summer.

Helitrox of is still a worthwhile class. One pro is when you move to a ccr you can start off with helium dil. My wife and I were prepped to go full trimix of. Bought extra doubles, extra stages, and deco bottles all in prep for future trimix diving. We ended up going ccr and all the extra bottles have sat unused.

 

[PfcAJ]

Yes, and I think its bad for diver development.

I strongly believe that people need experience and comfort diving deep on OC. A rebreather failure is not the time to figure out that you don't have strong OC skills.

 

[Marie13]

Helitrox of is still a worthwhile class. One pro is when you move to a ccr you can start off with helium dil. My wife and I were prepped to go full trimix of. Bought extra doubles, extra stages, and deco bottles all in prep for future trimix diving. We ended up going ccr and all the extra bottles have sat unused.

No CCR for me, unless I had a major change of mind. I like simple and low maintenance. RB are definitely NOT that. Plus the cost is ridiculous. I’m also not OCD enough for CCR.

 

[formernuke]

The less frequent trips for air fills would be cool but that price tag wow.

 

[Marie13]

The less frequent trips for air fills would be cool but that price tag wow.

Even at $3-$4K for a used unit, it’s still too much, plus all the other reasons for not doing one (mentioned in my previous post).

 

[JonG1]

Base cost on my SH KISS was £1500 needed lungs, cells etc but was diveable for less than £2k

 

[TrimixToo]

No CCR for me, unless I had a major change of mind. I like simple and low maintenance. RB are definitely NOT that. Plus the cost is ridiculous. I’m also not OCD enough for CCR.

There is
(edit) I'd started to say that technical diving already requires a fair bit of OCD, then decided I didn't want to get in to the OCD spectrum, and closed the tab. Afterward, I responded to Michael, and this popped up somehow or another...

Assume that your regular OC Trimix dive runs 150 minutes surface to surface with a max depth of 90M and you do it 2x per month.Your gas costs are going to be running $400-500 per month.
If you get your first rebreather used for $4000 to $5000 and invest $1000 in good training you'll have your money back within a year. Even if you buy new, you're ROI should be in the black after less than 2 years and your gas costs per dive end up running less than $15-20 per dive.

Michael
If you do what I did, which is buy used, buddy up with a rebreather diver and spend 30-40 hrs learning how to dive the RB properly before you take a course, you'll be able to learn a lot more when you finally take the course. Not recommended by any RB instructor but it worked well for me (I did already have O2 and PSCR RB experience).

The cost structure is a lot different if you mix your own. $250 still buys me a T of 5.0 He, and O2 is relatively cheap. 200'/90M twice a month is a couple of 18/38 fills. I'm not staying there for 45-50 minutes on OC, though. There is a limit to how many bottom gas tanks I want to swim around with, and the lost gas requirements are likewise more than I want to manage. For two dives to that depth for 30 minutes or so, with about 90-minute run times, I'll surface with thirds, using about 60 cu ft of He. That's nearly five fills from a T. Let's add in the cost of O2 for deco and just round it to about $60/dive, or nearer $120/month.

Also, from what I have heard asking around, getting from zero to Advanced Trimix on CCR costs closer to $4K than $1K. But even at $1K, the ROI is a bit different for those of us equipped to blend our own gasses. $6K buys a lot of He, even now...

All that said, I dive with a bunch of CCR divers. I am completely sold on their advantages. Were I 10 years younger, a CCR would be a no-brainer. At my age, I have to question two things. The first is how long the rest of my technical diving career will last. (Not everyone is named "Tom Mount.") The second is what percentage of it I want to spend building RB hours to get back to hypoxic trimix qualification on a CCR.

So far, that equation does not close for me.

 

[rjack321]

Yes, and I think its bad for diver development.

I strongly believe that people need experience and comfort diving deep on OC. A rebreather failure is not the time to figure out that you don't have strong OC skills.

I 100% agree that the people with no deep OC experience getting into CCR trimix are a mess. I have seen them and they rarely have their head wrapped around what they are doing (or should be doing).

But...
How deep is deep enough? And how many dives? How many years?

OC trimix is never going to "die", people will quite doing the dives frequently or with high helium mixes. But they will occasionally be bailing out forever