Info Helium is expensive and deep air is not my thing. -Let's talk about "Big" dives.

[justinthedeeps]

This last point right here is what has me looking hard at CCR sooner than originally planned. I like to dive in places where bringing a whole truck full of tanks just isn't feasible.
Do I invest in a gas compressor (maybe) or consider CCR?

It only took my nearest shop to be 45 minutes away, for me to do every dive as CCR.
Even for only 15 metres. Everything is better diving on CCR anyway (with a good unit, training and maintenance). Consumables cost per hour can be less than $10/hr, which is the cost of one air fill.

Even now with a compressor, I still prefer the CCR for all dives, including shallower ones.

 

[Angelo Farina]

Any practice is better than no practice but I’m not sure it really prepares you for very deep dives, especially not on OC.

40 minutes bottom time on air at 40 meters and 2 deco gases is just a normal wreck dive here - jump off the boat, possibly solo, drifting deco under a DSMB… even though I would go for 50% and 100% at 6m, deco at 3 in the ocean might be a no no.

I think you would still need to dive a lot in the 60 - 80 meter range to stay marginally current for 100 m - as the bottom times become shorter and deco increasingly more committing. Not sure that’s achievable with current helium prices either, or what would be the point of OC helium at 100 meters . For CCR it doesn’t matter, you fill bailout once every few years.

Exactly. For us european CMAS divers, 40m in air with nitrox hanging at the deco bar is a fully recreational dive. We do it normally with a twin tank, perhaps carrying a pony "just for safety" if some penetration is planned. Some people, such as my wife, with a very low SAC, make this dive with a single large steel tank (15l at 232 bars).
Tech diving is below 50m and with multiple gas mixes.

 

[Alex Ouroboros]

This last point right here is what has me looking hard at CCR sooner than originally planned. I like to dive in places where bringing a whole truck full of tanks just isn't feasible.
Do I invest in a gas compressor (maybe) or consider CCR?

In honesty you can do what a lot of the uk folks do, sign up for a weekend of diving with the ccr, take the necessary bailouts, and either take another set of O2 and Dil for the rebreather or source a couple of 300bar full size cylinders and decant to top up back at the car at the end of each days diving,
If your diving fairly regularly you’ll soon be financially better off I promise you.

 

[SelfDiver]

Why are you assuming this does not include CCR?
- You should do the shallower practice dives on the CCR too.
- With bailout like you are going to 100m
- Entering and exiting the water with all the gear on your own.
- Sitting at 3-6 meters with the rebreather for 30 minutes
- and so on

But, this is not the rebreather forum and more importantly - I have not done the jump to CCR yet. (Does anyone have a spare $8k lying around?)
My math for CCR is 30 to 1
At $8,000-$10,000 (Unit + training) the number of big dives you would need to break even is about 30.
This comes out to a big dive every other week for a year.
I think CCR is the way to go for my future.
CCR can be a bit too much for some, especially if you do ~10 big dives a year. The hassle of flying with the unit and getting service and sorb when you land makes the logistics more complicated.

Units are getting more reliable. The systems are getting easier to use and maintain. I predict a future where CCR rental is as common as Twinsets and stages are today. Liveaboards will have units available for traveling divers.
But we are not there yet.

For now, us peasants are still using OC and rubbing sticks together to make fire
My opinion is that you can do the Non-Helium dives with the same configuration as big dives and it will make for a fun and higher quality experience when you do pay the big bucks for Trimix fills.

 

[SelfDiver]

Exactly. For us european CMAS divers, 40m in air with nitrox hanging at the deco bar is a fully recreational dive. We do it normally with a twin tank, perhaps carrying a pony "just for safety" if some penetration is planned. Some people, such as my wife, with a very low SAC, make this dive with a single large steel tank (15l at 232 bars).
Tech diving is below 50m and with multiple gas mixes.

Yes. Exactly my point.
40 meters is a regular dive.
Do it in the same gear configuration as a big technical dive.
Carry two AL80s in addition to your back gas. This will make you used to the weight and trim
Breathe for a long time off your deco/pony/stage regulator.
You are already going in the water, why not practice for the harder dives?

 

[Still Kicking]

Yes. Exactly my point.
40 meters is a regular dive.
Do it in the same gear configuration as a big technical dive.
Carry two AL80s in addition to your back gas. This will make you used to the weight and trim
Breathe for a long time off your deco/pony/stage regulator.
You are already going in the water, why not practice for the harder dives?

Yes - follow the military doctrine: Train as you fight.

 

[rjack321]

Helium prices have gone up, way up.
Here are some things we can do with Nitrox to practice for the BIG dive.

What is a BIG dive? A big dive involves decompression, multiple tanks, multiple mixes or complicated logistics.
Doing an S-drill and SMB launch is nice practice but that is different than being in the water for more than 2 hours with multiple tanks.

Plan a dive to 40 meters on Air with 40 minutes bottom time.
Total Dive time is 100 minutes with ~35 minutes spent with deco 50% between 6-3meters.
This is an affordable dive with 4 X AL80 tanks. Even renting a twinset should be doable.
You will struggle at 80 meters with a team If you can't plan and execute this dive.
The gear configuration is similar to a Trimix dive to 100 meters.

The shallower deco dives on Nitrox are a cheaper way to achieve mastery in the process and procedures needed for big dives.
The depth is only one aspect of big dives. The real hindrance is logistics.
- How do you enter the water with 4 tanks?
- Do you need a safety/helper diver?
- Twinset or sidemount?
- Drysuit?
- DPV to get to the dive site?
- Staging deco or carry with you? leaving bottles along the way forces you return to the same spot for ascent or incur a penalty.
- Deep wrecks? Wall dive? are you comfortable navigating at 100 meters?
- Are you comfortable sitting at 3 meters for 30 minutes with your deco regulator?
The answers are easier to figure out at 40 meters than at 100 meters.
The Tech course or certification is not sufficient to be comfortable with all the logistics involved.
I am not casually doing dives to 100 meters with 2 hours of deco on a daily basis.
The practice is good for me. I can run drills while sitting at 3 meters for 30 minutes.

These cheaper dives also allow you to be a safety/helper diver for others who are doing expensive dives.
Agree to carry tanks, in and out of the water for eachother.
Agree to meet the divers at 40m and help in the ascent in case they need it.

Do the shallow dives like they are big Trimix dives and practice for when you finally get some cash for Helium.

Honestly I mostly see a giant mess of cylinders here and zero thoughts about any kind of video or mentor feedback. So knock yourself out, but you are mostly giving yourself a false sense of confidence that your bottle rotations actually are clean and you could in theory deal with an emergency midwater etc.

I mean right off the bat I can say you aren't going to be doing a 100m OC dive on 4x 80s anywhere North of FL and that would be iffy too.

 

[ofg-1]

 

[divezonescuba]

On OC, you can save quite a bit of helium costs if you use a travel gas and a low O2 tank for your first deco gas switch.

X21 or x20/20 as the travel gas and x32 as the low O2 deco gas is commonly used in Egypt for example to save on helium on over 180 foot deep dives.

On shallower dives the x32 is used as both a travel and low O2 deco gas to save a little helium on dives less than 180 feet like the blue hole arch.

Some instructors there actually do that dive on x21 as the bottom gas as TDI allows 180 feet. Not necessarily a good idea and I would not do it, but it is done there.

 

[justinthedeeps]

Speaking as someone who has gone to 60 metres on air and appreciated that experiment, even with a single tank, I would never do this again on purpose. The air narc is quite strong.

TDI is phasing this out before long ? "Extended Range (air)?" Or will it continue?

It is now possible for someone to go into fully tech-capable rebreathers without ever needing to buy, carry, or touch a twinset. Interesting.