Not to hijack the stage thread, what gas management do you prefer on multiple stage scooter dives? and why
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Not to hijack the stage thread, what gas management do you prefer on multiple stage scooter dives? and why
1/2+200, don't touch back gas. This way I can have 7 stages fail and still exit using back gas, or lose all of back gas in a ceiling bump and still exit using stages. Unless it's high flow and not very deep, I prefer to tow a scooter as well, swimming out racks up way more decompression than expected (up to 3x the deco on a deep dive), and often times you'll need more stages to exit than you can comfortably swim anyways.Quote:
Originally Posted by phillip1
For high flow caves like Ginnie/Manatee/Jackson Blue with a buddy who I know has practiced towing a diver, I'll use back gas, as I can swim out on equal gas to scooter in. To what degree depends on the buddy, current conditions (esp at JB with changing flow).
backgas in reserve, half plus 200 in stages, one or more tow scooters in nearly all cases.
safeties depending on what the cave is like and what we're doing
Backgas is not touched - just for reserve. Depending on situation and cave logistics, I will tow a spare scooter - everyone I dive with at that level knows how to properly tow a diver and has practiced it with me.
For a two stage dive, I'll breathe one stage going in and the 2nd coming out - again, never touch backgas.
For a three stage dive, I'll probably breathe one stage down, then drop the empty and one full. I'll proceed on the last stage and dive 1/2 plus 200, then turn dive. Never touch backgas.
Beyond that, I'm probably in a team dive mode doing exploration and there will be safety stages set and possible safety scooter set. Also, other stages to be used will be placed by support divers. Still, never touch backgas.
Nothing wrong with the half plus 200 method on stages, I just prefer the smoothness of breathing a stage down then turning or clipping off the empty, depending on how many stages I'm diving with. All this also assumes I'm never diving solo and I have a buddy who is proficient at sharing gas and towing a diver, and we've practiced it.
What size cylinders for back gas are you basing this on? I'm guessing you're assuming the scooter doesn't fail with the 7 stage failure. I'd venture to say if you have 7 stages fail your scooter will also likely fail and back gas will not be enough to get you out from the penetration you made with 7 stages. I always plan enough reserve to swim out regardless of anything else. Even with a tow scooter or buddy with a scooter. They only thing you can depend on is your own propulsion, and for some people even that's not true.Quote:
Originally Posted by jj1987
You can't always plan so swim out, your deco gas requirements would be completely absurd, especially on deeper dives. Take a tow scooter and a buddy.
1/2+200 results in using around 33.4 cu ft per stage. Overfilled 104's (3600) hold around 280cu ft So, that leaves us with 33.4*7 = 233.8 cu ft used going in with 7 stages, slightly more than an equal amount is reserved. I'm sure on any dive of this magnitude safety bottles would already be in the cave.Quote:
Originally Posted by RN
Swimming out just isn't an option in my opinion. There's the fatigue/cramps issue, the deco issue, nutrition/hydration planning for increased workload and time, etc.
Let's assume going into a 240ft deep cave with no flow until you reach the 5000ft mark. On a dpv we can cruise in and out at 150fpm, so we're looking at 33.3 minutes in and 33.3 minutes out, for a 67 minute dive time. Using 20/70/120 deco gases you're looking at 179min of deco on VPM. Now assuming you had to swim out (50fpm), that becomes 100 minutes just to exit, plus 33 minutes to enter, so deco becomes 358 minutes. Consider now that you're looking at 26 minutes of back gas deco up to 120 vs 13, so rock bottom doubles, sac rate is at least 20-40% higher, etc.
Even considering a .5 sac, which is very low for that amount of gear in an emergency, you're going to need 413cu ft of gas to get out plus rock bottom for the 180-120 deco. With a scooter that's 140 using the same SAC rate, and realistically a lower sac rate makes it even greater differential, with half the gas from 180-120 needed. I would say that gas isn't the answer, tow scooter is.
For Ginnie, sure, I'll swim out. For Eagles Nest, Morgan, Cream, etc, I'll take the 2nd scooter.
It depends on the dive. Typically don't touch back gas, and use stages to 1/2+200 as others have suggested. If it's a longer dive (3000'+) or deeper dive (120'+) make sure to carry a spare scooter, and possibly go a little more conservative on the stages. On the exit, breathe stages until they're empty then switch; if a problem happens you can jettison the empty stages while keeping as much gas in reserve.
Work out your speed on a scooter then work it out swimming. With my Magnus the ratio is approx 3. Then plan gas accordingly.
Having a backup scooter obviously makes this unnecessary. All the other rules of thumb may or may not work.
An interesting aside is, should you plan for scooter failures AND needing a double reserve? If you do, you end up taking an awful lot of gas.
For instance ginnie would require me to have about 240 cu ft available and untouched between the Henkel and the exit. Going back to 5000 feet requires about 400. I happen to have that much on repeat dives (I prestage) but will go lighter than that on a single quick dive.
My advice - do the math ( arithmetic really). Don't trust rules of thumb like " don't touch back gas" this rule will sometimes leave you with too much gas, sometimes too little. If you are in a no flow cave with no backup scooter, have something powerful like a Magnus, and want to have double the gas necessary to exit, you should only use 1/7 of your gas. Yup, it's like being an intro diver all over again!
Most of the posts above do not achieve this.
I suspect one of the problems is, few people have realized that scoots like the Magnus seriously change the game. You need a LOT more reserve gas on a Magnus than on a uv26 or Gavin.
DO THE MATH!!!!!
A minor point, but you need more than 3x the gas in some cases, as your "rock bottom" requirements from back gas to get to the first deco bottle go up as well as the gas to exit.Quote:
Originally Posted by aainslie
I did the math, and I need the same amount of reserve gas to swim out from 3000ft on a Magnus, UV26, XKx or Gavin. ;)Quote:
Originally Posted by aainslie
Obviously he referenced a context other than the fixed distance context in your post, but it's fun to pull people's chains now and then. :DQuote:
Originally Posted by jj1987
In the technically absurd it could even be argued that a diver would actually need a bit more gas doing fixed 3,000' penetration on a Mako or Gavin than a Magnus, as the Magnus gets you to the scene of the max pentration failure (gas or scooter) a lot faster with more remaining gas at the time of the failure.
you can outrun your reserves pretty easily on that thing I would imagine. perhaps just not at ginnie :P
Now you're thinking like a rebreather diver. Which is probably the best way to plan for a single scooter failure.Quote:
Originally Posted by jj1987
Quote:
Originally Posted by jj1987
Wow.Quote:
Originally Posted by DA Aquamaster
While this didn't happen on a dive where my primary scooter failed, I did have the 2nd scooter fail. I don't count on it.Quote:
Originally Posted by jj1987
And for the record, I'm referring to relatively shallow dives in regards to gas management. Anything that's deep enough to require tons of gas really needs to be done on a rebreather. This way you only need to bring gas to get you out.
in a buddy team you'd need three scooter failures to start swimming.Quote:
Originally Posted by RN
on deeper stuff if 'rock bottom' becomes a concern take a deeper bottle. I know i would be blowing off those 'deep stops' if I had an issue without even thinking about it
Seems there some consistancy in general terms regarding complex scooter dive reserve gas planning. I must be old school, I always do the dive swimming first, track my gas consumption very closely and then decide just what risk level I'm willing to take when using a scooter(s). I did the math from a few recent dives, albeit in very shallow caves, and I still carry and drop move gas than any of these forumlas would indicate.
Since we're all posting our thoughts, I must assume we're all alive, so whatever our bailout strategy is, it's worked okay up until our most recent dive. The next dive could be different unfortunately.
What's been the real life experience out there, don't we all tend to hold the trigger down too long and have far less run time on the scooters than we calculated in the plan. The drag with doubles, 4, 5, 6 or 7 stages and one back up scooter, even with practice is an enormous drain on the batteries at any speed.
I think I'll stick to knowing exactly how much gas I really need to ge the hell out of Dodge and live to post another day. Diving in more shallow caves as we have in Mexico is also a good idea, which I realize isn't something your Florida guys can do.
swimming there first isn't always an option. it goes without saying tracking your burn time under load is critically importantQuote:
Originally Posted by donlabbruzzo
I once talked with a cave diver that claimed (and he was being serious) he could out swim divers on a uv-26. This was his justification for not planning on extra gas for a scooter failure.
That diver was full of sheet!Quote:
Originally Posted by adam0321
Wow. That is about as good as listening to one diver tell another diver on a dive boat that he didn't need as much weight because he was diving air and not nitrox.Quote:
Originally Posted by Dsix36
If you really think so then I challenge you to show me one diver (Yes, only one is needed) that can out swim a UV-26 scooter when fully geared up for a cave dive. If you can, then I will publicly apoligize to the poster. If not, then you will kindly STFU.Quote:
Originally Posted by Sabado
You're talkin all wrong, see...it's the wrong tone.Quote:
Originally Posted by Dsix36
I didn't consider that option until I had already let my little fingers do their worst. Kinda like running my mouth without thinkin' first (not that I have ever done that).Quote:
Originally Posted by Sabado
Nah it's good. I got a kick out of it. My last post was supposed to be in Christopher Walken's voice.Quote:
Originally Posted by Dsix36
The amount of safety gas should equal the amount needed to swim out from the point of max penetration. Just as Ainslee said. Buddy or back up scooter make it even safer.
Scootering into Manatee w/2 stages is about the same speed as swimming out with 2 stages for me. Just an example of gas planning, not a broad brush approach for every cave.
For those that say they dont touch back gas, does that mean that you only go in 1/3 (or even 1/2) of an 80? Or am I misunderstanding that?
Bob
Not sure but are saying that I need to STFU? I never said I believed the diver making such claims. I think we all know that Phelps could not out swim a scooter. It was placed to be more of a joke than anything.Quote:
Originally Posted by Dsix36
half plus 200 on stagesQuote:
Originally Posted by floridabob
I think a joke was made that some were taking as serious and not sensing sarcasm.Quote:
Originally Posted by adam0321
No, No, No!! I was not typing at you, but rather Sabado. We already got it worked out. I took his post the wrong way and jumped all over him.Quote:
Originally Posted by adam0321
We need to develop sarcastic font. :smt102
I also wrote my little joke in there because if it was not a member who is as well known as Philip asking about multiple stage scooter dives they would probably be told to simply take a class. If this was a new member asking about this kind of dive planning it might be interpreted as trying to attain lessons on line about this type of diving. Now in the OP's case I think we all know this to not be the situation.
Dive physics can be very confusing.Quote:
Originally Posted by Sabado
Not to re-rail the thread, but...
When you stage scooter, you dive an 80 to half less 200 psi? Save the back gas for reserve? The dive would then be 1700 psi from an 80?
What the hell am I missing, gotta be something.
Cause the math would make better sense to dive 1/6ths of a set of double 104s...Assuming they are overfilled.
Like I said, what am I missing?
Bob
I re read the posts again saying they don't touch back gas just use the stages.
I don't get it. Why stage? I'm simply looking at the gas math side of this. Your double stage dive would be approximately 90 cubes of gas if you saved your back gas for reserve.
So, 250ish cubes in reserve on your back and another 90 in the stages?
Because you can't share stages and you typically leave them behind. Gas 2000' away isn't going to do you any good. Having a large reserve on your back gives you flexibility in the form of time to deal with delays, equipment problems, low vis, etc. Nothing is a rush because you have plenty of gas to play with.
And it would be 1300psi from an al80, not 1700psi. You'd drop it at 1700psi.
Think of it this way, for any given dive you're going to select a gas rule (thirds, fourths, fifths,etc) that makes sense based on conditions (flow, number of teammates, spare scooters, etc.). You're going to stick to that gas rule, but by maintaing your reserves with you.
Quote:
Originally Posted by floridabob
Scooter while breathing the stage down to 1700 psi, turn the dive and continue breathing the stage. You would exit the cave with 400 psi left in the stage. You would have full steel cylinders on your back or side. Diving 1/6ths of a set of 104s cave filled will give you about 15 cf more to use on the dive (penetration and exit), but it will also decrease your reserves by 95 cf. In a cave that averages 90 ffw depth, I can easily scooter over 7000 feet. I would need just over 200 cf of gas to swim out from 7000 feet. That would only leave me an additional 30 cf of gas after scootering in and swimming out. Add a stage and my penetration is limited to just over 5000 feet and I still have 55 cf in my 80 and 285 cf in my 104s to swim out and I only need 146 cf to swim out. So I come out with almost 200 cf of gas left over.Quote:
Originally Posted by floridabob
From my understanding, the math gets 'complicated' by the increased number of variables introduced. The biggest of these is the fact that it takes a lot more gas to get out than to get in if you go in on a scooter and it fails at max penetration. The simple part is that gas planning boils down to a simple fundamental; how much gas will it take to get out?Quote:
Originally Posted by floridabob
Right now, for me, being new to scootering, my SAC is about the same swimming or scootering. But, on the scooter, I am covering almost 4x the distance. My plan needs to compensate for that. If my buddy is in a similar state, I need to compensate for that. If I want to bring my failed scooter out, I need to compensate for that. If (when) I get to a point that my scooter SAC is much lower than my swim SAC (please say it will be so ;-) ) then I'll need to compensate for that.
After the gas volume, all you have to do is figure out the best risk management for where it'll get carried. I don't SM yet, either, but I understand that you breath so much from one side and switch to the other. Some have mentioned to me that this keeps you balanced. I sometimes have three stages on one side and seem (all my buddies can remain quiet here) to pretty much keep my balance. I figure a more fundamental reason is to 'balance' the gas so if a regulator goes, you don't wind up with a light tank/working reg ; heavy tank/failed reg.
For the record, I intend to take a class in both to accelerate my learning curve.
for you 'swim out' guys are you still taking 40 cuft bottles of o2? or are you taking more deco gas as well?
Balancing gas is more for balancing reserves than balancing the weight of the gas. There are situations in which if you don't manage your gas properly in sidemount and you lost the use on one cylinder you could find yourself without enough gas in the other cylinder.Quote:
Originally Posted by scububa
Taking enough gas to decompress should I have to swim out.Quote:
Originally Posted by LiteHedded
Ok. I get all the numbers. That was my point. I was trying to understand what you guys are proposing for gas reserve rules. Quite frankly, I find it hard to believe that you would, on a single stage scooter dive, dive only 1300 psi in penetration on an 80. Leaving all back gas for reserve. I gotta call BS on that, first point.
RN, as usual, gets it. We just differ on the approach explanation/understanding, but we are aligned.
I propose that you need your gas plus your buddy's gas at the point of max penetration in reserve. Additional gas would be great...but...
You have to know what it takes to exit, swimming, for your dive. Thats your reserve. Then you address your buddy's.
Or not
Sorry, poor joke.
Dive solo. :)
I do that all the time.Quote:
Originally Posted by floridabob
In Jackson Blue it gets me to p4,000', for a total run time of about an hour. My girlfriend likes me to limit my solo dives to the main line, and under an hour. It makes for a nice dive.
I, too, do dives like that. I am surprised that, with buddies, people only dive that same dive as a rule.
And my point isnt that it isnt or shouldnt be done just that I am not sure I think most people plan a dive that way in a team. I have seen, with great frequency, divers at Ginnie dive to the Hinkle (or the bypass), with scooters and a stage. Drop the stage and scooters there and then switch to back gas and keep going. However far they go is past what most here are proposing.
To be fair, SAC is a variable that pushes numbers one way or another.
Whatever you guys do or not impacts me very little. And I'm not really concerned about it, just surprised to hear most people say that diving 1300p from an 80 is their normal dive with a scooter with a buddy. And a back up scooter, too, for that matter.
I've scootered to the Henkel three times, each time with a buddy or two, and each time I breathed a stage only.
In fact, I'd venture a guess that 97 of my last 100 cave dives I haven't breathed backgas.
Think my point is still being lost. What one diver does/does not isnt my point. In fact, polar opposite. I find it hard to believe MOST people are doing what youre doing as a RULE with buddies and a back up scooter. Which is what they said they were doing.
I'm fine if they are, just wouldnt have thunk it.
For me personally, I like to be in the water. I shoot for a 90 minute run time most dives. Plan gas/location/time around that. I prefer a 120 minute dive even more.
But that's me...If I'm driving 3 hours and $55 in gas then I'm going to be in the water.
I don't think most people do that. I think most people don't really understand how to plan scooter dives and if they were to have an issue during the dive would likely be very close to empty when they hit the cavern...if they hit the cavern. One of the things I try to do with my DPV students is a stage dive with back or side gas being reserve gas only. I don't get to do it with all classes since different things dictate different classes, but we at least discuss it every class.
I don't do a lot of ginnie springs/Jackson blue diving where almost anything will work.
My scooter dives are multi stage multi scooter affairs and I don't touch backgas.
Ginnie springs is a different beast.
I can see a certain advantage in terms of convenience to the practice of not touchging back gas. For example, with 230 cu ft of primary gas, you could dive 3 stages to half plus 200 (using a total of 100 cu ft of gas for penetration) and then still have the full 230 cu ft of primary gas in reserve, leaving you twice your penetration gas to exit on the scooter in the event you "lost" the gas in all three stages (not likely), or a bit more than three times your penetration gas to exit in the event your scooter dies.Quote:
Originally Posted by floridabob
Which is to say that it may or may not be enough reserve for a 3 stage dive, but you would probably not have to worry too much about calculating the actual reserve requirements on a 1 or 2 stage dive, at least at reasonable nitrox depths where the deco obligation from swimming out would not be a major factor.
----
But in general I agree with you. Our purpose in taking a cave DPV course was to extend the area of cave we can explore, in more or less the same manner we've done before. In the near term this means scootering to the points we used to swim to on thirds, and then continue swimming from that point, turning the dive so as to arrive back at the scooter with, at a minimum, the amount of gas needed to swim out. In that regard, if we use a third or half of a stage scootering to that point, the gas left in the stage is just extra reserve on top of the reserve we have already calculated and included in our primary tanks.
Now, we could do the same dive using multiple stages to 1/2 plus 200 and keep all the reserve in back gas, but the reserve would be over kill on what are still fairly short p. dives and we'd end up swimming multiple stages for most of the dive, rather than just during the scooter phase of the dive. It's not a big difference if you scooter the whole dive, but it makes a difference if you swim the middle bits of the dive.
In doing dives where all of it on the trigger just to get more trigger time for Marci, we noted that the dives were pretty short, 45-60 minutes, versus 2 to 2.5 hours for our average swim only dives, given the need to maintain a greater gas reserve in the event of a scooter failure and with resepct to the limits of the battery.
what he's saying here is valid. all dives are not created equal and you just need to think it through. shallow dives where you're dropping the scooter and swimming are obviously going to play out a little differently than a deep multistage exploration dive where the gas really is for solving problems more than swimming out of the cave.Quote:
Originally Posted by DA Aquamaster
there isn't really a one size fits all rule of thumb for this stuff but when in doubt, more gas on my back always gives me warm n fuzzies
Very true. Ginnie and Jackson get different rules than other places I scooter. However, rather than multi stage multi scooter, a rebreather is my choice tool. Still have enough gas to get out and deco should I have to bail out, but I just don't have to concern myself too much with my penetration gas since it's a fraction of what I would need on OC.Quote:
Originally Posted by LiteHedded
well that's certainly another topic worth discussing :)Quote:
Originally Posted by RN
like where does the line with regards to risk/reward fall when it comes to big open circuit dives vs bringing a rebreather into the picture.
The line starts with the signature line on your credit card slip.Quote:
Originally Posted by LiteHedded
With the bad 'luck' rebreather divers had last year, good question.Quote:
Originally Posted by LiteHedded
Medicals, bro, medicals.
As Obi Wan would say "In my experience, there's no such thing as luck."
you mean all the heart attacks?Quote:
Originally Posted by SuPrBuGmAn
True. For me it's the diffference between 2 stages or 3. I don't mind carrying 2 stages but 3 is a PIA. Easier to add the rebreather than it is to add a 3rd stage.Quote:
Originally Posted by LiteHedded
Helium is the equalizer when it comes to stages. If they're heavy nitrox stages, they're miserable.
Agreed. With helium the third and fourth stages are no big deal
Yeah, rebreathers are heartattacky, according to 2011Quote:
Originally Posted by LiteHedded
That's not entirely true, as there are some other variables involved. First, it's largely a matter of what middle aged guys want to spend their disposable income on. 20 something year old strippers are probably just as heart attacky as rebreathers. And second, it's also easier for EMS to get to the nudy bar, so there are fewer fatalities with strippers.
In this day and age, there's still more middle aged guys spending their money on OC tech gear than rebreathers.
In this day and age, there's still more middle aged guys diving their OC gear for tech dives, than rebreathers.
In 2011 more guys were dying while diving on rebreathers than on OC, while on their tech dives.
In 2011, atleast two of the rebreather divers who died weren't middle aged, while on a tech dive.
20 year old strippers that are heartattacky, are probably doing copious amounts of blow, which I don't think is the problem for rebreather divers, middleaged or not...
It's a problem for some...
Touche'
...but I don't think it(blow) had a factor in any tech diving deaths from last year.
The problem with heart attacky 20 year old strippers is not a reference to strippers doing blow, it's the reference to the old guys doing the strippers and thus inducing heart attacks in the old guys.
All ya all need to spend time somewhere other than in church to fully appreciate the nature of the problem, them old guys is facing.
I am a middle age guy who was dating a 20-something stripper and I can say that heart attacks are very possible. Thank God I grew up and found a good Catholic girl to marry.Quote:
Originally Posted by DA Aquamaster
Not using sidemount(backgas) gas is quite possibly not an option. In my case that's pretty much all the time and I imagine also with what Philip is doing. I take a backup scooter, dive thirds or less of stages and push them forward as much as is possible or comfortable. I don't necessarily plan that one scooter (assuming one fails) needs to get me all the way back to my entry point.
Sounds like you are not using much out of the stages and instead using backgas?Quote:
Originally Posted by alanf
If there's enough room to scooter there's enough room to use the stages and reserve the backgas IMO. Having empty backgas and 2/3rds of a bunch of stages would be a sucky way to exit.
No I am scootering to as close as I can to where I am exploring in sidemount gear, and I believe Phillip is doing the same. Sometime scooters are for transport not just for the ride, and because of this require a different kind of gas management.Quote:
Originally Posted by rjack
20 year old stripper!? Bring on the heart attack.
I wouldn't breathe the SM tanks on the way in on the scooter. I would still use down to 1/2+200 (1700psi) on the stages and then do the penetration swimming on backgas. If you are doing 1/3rds of backgas (which is really aggressive IMO) I would bring a safety bottle instead of breathing a little bit less out of multiple stages.Quote:
Originally Posted by alanf
rjack, thats what I've done on a few exploration dives where we scootered then swam (not to thirds, though). Diving over safeties gives you a lot more options.
Yes alot more options than diving 1/3rds of stages. That's only 300psi more per stage, 7.5cf or so more than using them down to 1700psi and then exhausting them (and discarding them if need be) on the exit. I'd rather have a full safety to compensate for all sorts of lost gas contingencies than having an extra 300psi scattered around in 10 different stages.Quote:
Originally Posted by PfcAJ
Helium is a lot cheaper with a rebreather, though. So if I'm breathing helium it's very likely through a loop.Quote:
Originally Posted by PfcAJ
Cost isn't really a factor for me when it comes to planning exploration dives. If I can't afford it, I just wait a while. Nbd.