DIL, bail, and MOD

B

broncobowsher

Member
I have a JJ question, for those using DIL as bailout. PPO2 and MOD...

I'll start with I don't have a JJ, but know of them a little. I just have a rEvo and that is what I know about. The JJ can be different and was thinking about something the other day. I know one of the ways to configure them is with a lot of DIL and use that as the bail out as well. Just going off the O2 side of things at the moment, I know how I dive would be something like 14% O2 in the DIL but ~18% O2 in the bail out. I consider both to have a MOD of 200' (60m for most of the world). The lean DIL lets me flush the loop down if need be, the rich bail isn't too rich for starting an ascent. No hard overheads, caves, etc.

What do you do when you have only one gas? Is it optimized for DIL? Run it a bit rich so it can be a better bail out gas? I don't know anyone specifically that runs a JJ to ask. So I thought I would just ask.
 
Hi! this forum is unfortunately almost dead. Ask your question in the Scubaboard forum in the rebreatherdiving thread instead. You will most likely be berated and questioned and in the end you will have an answer faster than here :D
 
I know those places. I figured there were still a few friendly people around here. I'm in no hurry. Give this forum a chance to have one more breath in it. At least it isn't dead like rebreatherworld, filled with spam until it choked and died. If I eventually have to go there I will. Going for the low drama version here first.
 
broncobowsher said:
I know those places. I figured there were still a few friendly people around here. I'm in no hurry. Give this forum a chance to have one more breath in it. At least it isn't dead like rebreatherworld, filled with spam until it choked and died. If I eventually have to go there I will. Going for the low drama version here first.
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Hi guys a few of us who dont do facebook still check in here once in a while .I have recently seen an article on folks on 1 gas mixing it for onboard and bailout capabilities calling it " dillout" Ill see if i can find it ,it was interesting.
 
markdol1 said:
Hi guys a few of us who dont do facebook still check in here once in a while .I have recently seen an article on folks on 1 gas mixing it for onboard and bailout capabilities calling it " dillout" Ill see if i can find it ,it was interesting.
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also for 200 ft and under ill use a n 18/45 mix i dont see any reson to use a hypoxic mix and its still loww enough o2 for a dill flush.
 
I believe one of the thoughts for cave purposes was to run the dilout slightly "hot" (as far as dil goes), so if you have to bail way back in a cave, you're not racking up a lot more deco by bailing out. I think that also goes with the "shut down o2 feed and breathe down a hot loop" solution that is seen in some sidewinder divers (rather than dil flush, probably because a dil flush only gets you so far when your dil po2 is 1.1 or 1.2).

I'm not entirely sure how the JJ folks are doing it. I seem to remember seeing a GUE standard dil chart that was essentially the standard gasses, but shifted one depth down to get 1.0 ppo2 at depth. That would be less than ideal to bail to,

From a practical standpoint, constantly topping up dilout stages or doubles of trimix is a huge PITA, unless you have/are a shop with banked premix that just needs to be boosted. It also means you either 1) always do the same dives/depths, 2) have multiple dilout stages or racks, or 3) do a lot of dives with a mix you probably don't need.

Jim
 
I know just about everything done in caves is done just a little different. If that is the only reference material available, fine. I was hoping for more non-cave references. Just to better compare them to what I know with my rEvo.

But it does make sense to run the DIL a little hot so it isn't as horrible of a bail out.
 
Isn't diluent with a max PPO2 of 1.1 so you can bring down a high PPO2 and check the cells, whereas the bailout you'd typically want 1.4 which is above the 1.3, 1.2 you would run your unit at?

Practically this means your dil would be the next 'standard' gas down than the bailout. Or if using the bailout as offboard diluent, this would need to be brought down.

Some people use air for their diluent and then use offboard diluent (from the bailout) for the bottom phase. This means the wing's filled with cheap gas and the expensive gas is limited to the loop when deep. (Have heard of this with Revo divers)
 
Wibble said:
Isn't diluent with a max PPO2 of 1.1 so you can bring down a high PPO2 and check the cells, whereas the bailout you'd typically want 1.4 which is above the 1.3, 1.2 you would run your unit at?
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Maxing-out the PO2 of deep bailout isn't necessarily the best idea. If you've bailed-out due to a serious hypercapnia issue, you run the risk of driving-up the CNS with too much O2 in the bailout gas and ending-up in the shit. Trust me, I've survived an ox-tox that came on almost an hour after bailing-out due to a CO2 issue.

Clearly, in open-water it may be possible to head-up quickly and thereby rapidly reduce the PO2 but if you had to get out of a cave or wreck before ascending, the CNS could be shooting-up.

My deep bailout is to allow me to instantly breathe easily, so I want shitloads of helium. I'll worry about the oxygen (and therefore deco) when I'm shallow and relatively safe.
 
For open water I carry a rich bailout, optimised for Deco (ps. It will be 1.6ppO2 at my planned max depth).

They are few circumstances where I can't begin an accent immediately so getting onto a rich mix and ascending is preferable, for me.
 
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scubascooby said:
For open water I carry a rich bailout, optimised for Deco (ps. It will be 1.6ppO2 at my planned max depth).

They are few circumstances where I can't begin an accent immediately so getting onto a rich mix and ascending is preferable, for me.
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That is how I was taught and what I practice as well. My bailout is completely separate from my DIL. Makes it easy to run two different PPO2s and MOD.

I'm trying to figure what people do that run diluent as the bail out, typical of a JJ setup. Not so much the Helium side of it, crank it up and breath easy. A good bail out is a high PPO2 which makes really hot DIL, a DIL that is lean enough makes a crap bail out. What is preferred, or what is the balance point in between? Not being trained on one and the logic, looking for those that have. Don't have a local connection to personally ask either.
 
the different DIL and Bailout PO2 is, IMHO, a classic case of not seeing the wood for the trees. The difference is inert gas uptake between 10 and 12% at 10bar (90m/300ft) is 2%... yet for PO2 is 20%. If you really believe that 2% more inert gas makes a difference in your deco I think you need to relax a bit and dive more ... ;)
 
Bobjr said:
the different DIL and Bailout PO2 is, IMHO, a classic case of not seeing the wood for the trees. The difference is inert gas uptake between 10 and 12% at 10bar (90m/300ft) is 2%... yet for PO2 is 20%. If you really believe that 2% more inert gas makes a difference in your deco I think you need to relax a bit and dive more ... ;)
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I will admit I was looking at it from an O2 side of things. I had not thought of it from the inert side of things. Gives me something to think of.
 
Excellent question, perhaps a reminder why the stock JJ-CCR and its kin are designed the way they are, and why the mainstream (e.g. TDI) standards are the way they are.

In short, diluent and bailout are carried and optimised for completely separate purposes, and for multiple reasons it is not optimal to use a lone gas supply or mix as both diluent and bailout.

First off, the stock JJ-CCR carries ~3 litres of diluent and you carry your bailouts as offboard cylinders, just like everyone else.

Niche organisations that try to reinvent diving in their own image--such as claiming that you need to carry a monolithic 14 litre twinset of dilout on your back for all dives--will not have a technically valid answer to your question, nor will they be carrying a gas that is optimal for both diluent and bailout. They will also be stuck donning a 60kg / 130+ lb rig for every kind of dive, rather than a 30 to 40kg one + bailouts tailored to each situation, and they will be stuck with the same giant supply of a single mix of expensive trimix diluent, rather than being able to swap out and re-blend small cylinders of different diluents with quickness and ease.

I have a BOV on my JJ-CCR and I plumb it into my large, adequate, optimal offboard bailout cylinder(s) at max pO2 of ~1.4 via a high flow quick disconnect. Tests out well to 90 metres (full bailout drill). Meanwhile my adequate, optimal diluent, which has a lower amount of oxygen in it that is idealised for diluent purposes at max pO2 of 1.0 to 1.1, is in a 3 litre on the back. Sometimes there is an additional 3 litre cylinder of fill gas (e.g. air) used for an independent (and cheap) wing or suit inflate.

In fairness to very deep divers, yes I notice it seems necessary and wise to put multiple large cylinders of diluent on your rig, but in my [limited] experience it should not generally be seen as a universal or optimal replacement for offboard bailouts--as clever or convenient as that sounds for people trying to paste CCRs onto their own existing special ideas about how there is only one way to dive with an OC twinset.
 
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bubblemonkey said:
Excellent question, perhaps a reminder why the stock JJ-CCR and its kin are designed the way they are, and why the mainstream (e.g. TDI) standards are the way they are.

In short, diluent and bailout are carried and optimised for completely separate purposes, and for multiple reasons it is not optimal to use a lone gas supply or mix as both diluent and bailout.

First off, the stock JJ-CCR carries ~3 litres of diluent and you carry your bailouts as offboard cylinders, just like everyone else.

Niche organisations that try to reinvent diving in their own image--such as claiming that you need to carry a monolithic 14 litre twinset of dilout on your back for all dives--will not have a technically valid answer to your question, nor will they be carrying a gas that is optimal for both diluent and bailout. They will also be stuck donning a 60kg / 130+ lb rig for every kind of dive, rather than a 30 to 40kg one + bailouts tailored to each situation, and they will be stuck with the same giant supply of a single mix of expensive trimix diluent, rather than being able to swap out and re-blend small cylinders of different diluents with quickness and ease.

I have a BOV on my JJ-CCR and I plumb it into my large, adequate, optimal offboard bailout cylinder(s) at max pO2 of ~1.4 via a high flow quick disconnect. Tests out well to 90 metres (full bailout drill). Meanwhile my adequate, optimal diluent, which has a lower amount of oxygen in it that is idealised for diluent purposes at max pO2 of 1.0 to 1.1, is in a 3 litre on the back. Sometimes there is an additional 3 litre cylinder of fill gas (e.g. air) used for an independent (and cheap) wing or suit inflate.

In fairness to very deep divers, yes I notice it seems necessary and wise to put multiple large cylinders of diluent on your rig, but in my [limited] experience it should not generally be seen as a universal or optimal replacement for offboard bailouts--as clever or convenient as that sounds for people trying to paste CCRs onto their own existing special ideas about how there is only one way to dive with an OC twinset.
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Yawn ... are you really so insecure about your diving (probably due to your lack of experience) that you have to attack another configuration?

Good luck doing a dil flush at 90m with a 3L, you keep smashing those v-shaped profiles mate
 
Bobjr said:
Yawn ... are you really so insecure about your diving (probably due to your lack of experience) that you have to attack another configuration?

Good luck doing a dil flush at 90m with a 3L, you keep smashing those v-shaped profiles mate
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I'm just trying to answer a question addressed to "JJ folks" that is pretty simple to answer correctly if you clarify that it is not designed to be dived in 14 litre dilout mode for every single dive.

But if you want to make this about me (flattered!) then if my first flush at depth doesn't work (yes a 3 litre is sufficient for that) and the loop is still unsafe to breathe then I'm bailing out to a BOV connected to a full sized offboard gas dedicated to that purpose. That gas could also be plugged into the diluent MAV for additional flushing, if returning to the loop is advisable. Additional bailout cylinders are carried as needed for the dive plan. Wing buoyancy is coming from a separate wing fill cylinder of compressed air for trimix dives (since JJ-CCRs are easy to config in several different ways).

I'm not sure I understand why you think bottom time has anything to do with diluent capacity?

Far into a cave it is a reasonable idea to carry a lot of bailout (as dilout) on the space available on the back of the JJ-CCR, which I imagine is one reason why some folks do it that way. But evidently the fervent expansion of this niche movement into general open water diving is confusing people as to how the JJ-CCR is actually designed (i.e. for versatility)
 
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