What SAC-rate are you planning for from bailout to first stop?

SAC estimate when bailing

  • Same as nominal, <20 lpm

    Votes: 4 5.9%

  • Moderatly elevateted, 20-30 lpm

    Votes: 22 32.4%

  • Elevated, 30-40 lpm

    Votes: 27 39.7%

  • Greatly elevated, >40 lpm

    Votes: 15 22.1%
  • Total voters
    68
Mr Walker

Mr Walker

Relax /Frankie
I believe I'm responsible for derailing another good thread with this issue. My apologies to Jeppe for that.

However it would be intresting to know how you plan for bailout. Personally I use MultiDeco to calculate this first stage - from bailout to first stop. I've set it to reasonable (in my view) 40 lpm.

If you use other means or methods for calculating your gas comsumption during this first stage please give a comment on that.

For those of you who are not yet metric;
20 l = 0,71 cuft
30 l = 1,06 cuft
40 l = 1,41 cuft

/nils
 
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Actual figures during course dives has showed that I have a SAC/RMV of 25 lpm when bailing out. So that is what I use + I use thirds as extra padding.
 
I plan for 30 lpm and then 15 for deco. I always dive with a buddy (wife - may/may not be a good thing) so *should* have more gas available if I need it.
 
I have had to bail out and my SAC then was 18 lpm. But I know that if I ever one day have a Co2 hit then my SAC will most probably go out of the roof. So I tend to settle for 45 lpm

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I put greatly elevated but my SAC is 12-15 so 25 as i plan is greatly elevated.

My deco SAC is usualy arround 10


HOWEVER

My bailout plan will allow for 100GF low so i can blow all deep stops and get shallow fast if I need to save gas.

So on a 30min @ 60m dive, rather than stop at 33m as I would need to on a 35/85GF I would ascend imediatly and as fast as I could cope with to 18m on a 100GF


Gas volume safety is not just in SAC

ATB

Mark
 
Mark is correct, its not just about SAC.

In fact, the question of what volume calculation from the bottom could be considered a moot point for ocean diving.

Most dives will require not as much gas as many would think to get you to the next gas switch, or up to the 'proper stops.' If you get off the bottom expeditiously without fiddle faffing, and then do a proper fast bailout of around say 15 - 18m per minute, then how long will it take you to go 3 to 5 ATA vertically? Even if you add in time for opening valves, deploying regs etc, you should be talking about 5 or 6 minutes max. Just about any tank you were thinking of taking should hold at least twice as much as you need.

More important IMO is how close is your buddy and are they looking out for you? (Will they notice you have bailed out? Don't want to waste precious minutes flashing your torch wildly to get their attention)

More important IMO is your ascent rate and being comfortable and proficient at stopping when you get to the switch and being able to manage your buoyancy whilst doing it. Many of my students are surprised that it took LESS dumping of gas than they thought and more finning to achieve an ascent rate of over even 10m per minute.

I guess the million dollar question is hypercapnia and / or panic and what effect that will have on breathing rate. I think its important to have a baseline first as to how much you would use with a normal SAC, and then take it from there, rather than taking acres and acres of gas and not really understanding how much you would normally need.

That becomes even more useful when calculating bailout in a cave or wreck penetration, where there will be a linear bailout before you can come up for deco
 
I don't know all this lpm crap, I use cfpm for my figures. I had an instructor have the brain cells to monitor my gas usage during a co2 event and I still use that figure for my deep bailout as a minimum - .78cfpm.
 
DSix36 said:
I don't know all this lpm crap, I use cfpm for my figures. I had an instructor have the brain cells to monitor my gas usage during a co2 event and I still use that figure for my deep bailout as a minimum - .78cfpm.
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dear lord thank you... :)
 
I plan for 30 and didn't think that'd give me enough gas. But just planned on cutting my deco back if no buddy gas access.
 
alexasigno said:
.78cf is 22L. That seems crazy low especially for a CO2 hit, or was that your average over the whole dive?
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I never said it was a full on co2 hit. It was a co2 event. If it were any worse than it was, there is no way that I would have been able to get a bailout reg in my gobb. I had to concentrate and time the swap out since I refused to stop breathing during it. The .78cf is the rate that I sucked my alum40 dry before switching to my second tank.

My resting sac is .4 and my normal easy swim sac is .5

I still plan for minimum of 1.5 x my sac rate of .5 for all gasses and will often pad out the bottom mix even more depending on the dive perimeters.
 
Anyone tried this mythical fast ascent, anyone tried it without a reference. With some of the ascent rates quoted, you'll be needing to hit the brakes at 20 or deeper if you want any chance of stopping at 6, if you keep control at all. Shoot up from 60, blow it and end up on the surface coughing up a lung, no thanks. I plan for a steady ascent.







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GaryL said:
Anyone tried this mythical fast ascent, anyone tried it without a reference. With some of the ascent rates quoted, you'll be needing to hit the brakes at 20 or deeper if you want any chance of stopping at 6, if you keep control at all. Shoot up from 60, blow it and end up on the surface coughing up a lung, no thanks. I plan for a steady ascent.







Sent from my ivory tower using Tapatalk
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Let me clarify, its not bolting all the way to the surface or shallow stops:) Just to your next gas switch, which will be 21m or deeper on anything with mix. Another reason why I use 50% for deco.
 
Chris Brown said:
Let me clarify, its not bolting all the way to the surface or shallow stops:) Just to your next gas switch, which will be 21m or deeper on anything with mix. Another reason why I use 50% for deco.
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I get that Chris. It was more a generalized statement that while it's all well and good planning a fast ascent (to next gas switch), I think the reality may well be far different during an arse clenching moment. I'm not convinced I could ascend much faster than 10m/min and still maintain buoyancy control when all's well, let alone when crap and fan collide.
 
I hear ya, and its a valid point.

If you do Mod2 with Peter Sotis in FL, you will learn TTS planning and fast bailout ascents. He will actually get you to bailout from 60m in the ocean, do a gas switch at 21 and then simulate a low deco gas scenario where you have to switch tanks with a buddy.

Here in the UK, theres no way I would do that now even in a quarry. In fact, I can't do skills deeper than 30m for standards anyway. I have found that bigger drysuits (especially neo) and bigger undersuits and more lead / weight is often meaning a challenge on buoyancy shallow. Especially on bailout where some units may have solenoid firing and all your tins are empty:) In the tropics, with a lighter dry suit and a more natural buoyancy (as opposed to being very buoyant and heavily weighted down) its not as big an issue.

For me - Im getting either rec / wreck divers and / or OC tech divers who have spent their entire career being told slow and steady on ascent. (DAN studies show an average 15 foot per min ascent IIRC), so its more about introducing them to the concept of getting off the bottom and not fiddle gaffing:) For most, they have never finned up before.

Its a bit like old OC trimix, where you have to get people to understand that a slow ascent to switches can equal more deco and not enough gas and a blown out plan.
 
Chris Brown said:
I hear ya, and its a valid point.

If you do Mod2 with Peter Sotis in FL, you will learn TTS planning and fast bailout ascents. He will actually get you to bailout from 60m in the ocean, do a gas switch at 21 and then simulate a low deco gas scenario where you have to switch tanks with a buddy.

Here in the UK, theres no way I would do that now even in a quarry. In fact, I can't do skills deeper than 30m for standards anyway. I have found that bigger drysuits (especially neo) and bigger undersuits and more lead / weight is often meaning a challenge on buoyancy shallow. Especially on bailout where some units may have solenoid firing and all your tins are empty:) In the tropics, with a lighter dry suit and a more natural buoyancy (as opposed to being very buoyant and heavily weighted down) its not as big an issue.

For me - Im getting either rec / wreck divers and / or OC tech divers who have spent their entire career being told slow and steady on ascent. (DAN studies show an average 15 foot per min ascent IIRC), so its more about introducing them to the concept of getting off the bottom and not fiddle gaffing:) For most, they have never finned up before.

Its a bit like old OC trimix, where you have to get people to understand that a slow ascent to switches can equal more deco and not enough gas and a blown out plan.
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You need to man up Chris - heavy drysuits and cold water are easy especially in a quarry :D :D :D

Graham
 
LOL, Im talking about my students.

But yes, I need to man up on the cold - or go to the Red Sea. That sounds better!
 
GaryL said:
Anyone tried this mythical fast ascent, anyone tried it without a reference. With some of the ascent rates quoted, you'll be needing to hit the brakes at 20 or deeper if you want any chance of stopping at 6, if you keep control at all. Shoot up from 60, blow it and end up on the surface coughing up a lung, no thanks. I plan for a steady ascent.









Sent from my ivory tower using Tapatalk
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I have done a fast ascent from 403' to 200' and by fast, I mean 100+fpm. I started dumping my wing at 230' and blew by my stop by 20'. I had to invert and kick to maintain control as I finished dumping my wing. It is very doable with practice and knowledge. It feels completely like a runaway ascent and that you are out of control when you first try it, so thank that as fair warning if you are foolish enough to do what I do.
 
Chris Brown said:
I hear ya, and its a valid point.

If you do Mod2 with Peter Sotis in FL, you will learn TTS planning and fast bailout ascents. He will actually get you to bailout from 60m in the ocean, do a gas switch at 21 and then simulate a low deco gas scenario where you have to switch tanks with a buddy.

Here in the UK, theres no way I would do that now even in a quarry. In fact, I can't do skills deeper than 30m for standards anyway. I have found that bigger drysuits (especially neo) and bigger undersuits and more lead / weight is often meaning a challenge on buoyancy shallow. Especially on bailout where some units may have solenoid firing and all your tins are empty:) In the tropics, with a lighter dry suit and a more natural buoyancy (as opposed to being very buoyant and heavily weighted down) its not as big an issue.

For me - Im getting either rec / wreck divers and / or OC tech divers who have spent their entire career being told slow and steady on ascent. (DAN studies show an average 15 foot per min ascent IIRC), so its more about introducing them to the concept of getting off the bottom and not fiddle gaffing:) For most, they have never finned up before.

Its a bit like old OC trimix, where you have to get people to understand that a slow ascent to switches can equal more deco and not enough gas and a blown out plan.
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Tis a balance. Get up quickly enough to limit excessive deco obligations, but not too fast that you blow a red light and slam the wall. Difficult to achieve espec as we do it so little.
 
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