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All dives are deco dives, Jeffrey. The difference is I do not consider it mandatory enough to worry about it on a short dive like what I was desribing. If I were in overhead, or if it were a real deco dive, I would insuist on redundency. Jeffrey Swann wrote: > > Dear List, > George > Are you saying, that you get into deco time with a single tank. > This seems to throw away your teachings. > I mean, frankly where does recreational and tech diving separate. > I do alot of nitrox type diving. > That is 20 to 30 m wrecks, multilevel, etc. > I use a harness routinely now and practice redundancy. > This brings me to the point: > What is wrong with carrying a pony with a single. > I sling it across my waist, clipped up tight. > Reg clipped off, on the harness. > Back gas EAN 36. > Pony 25 cu ft EAN 50. (or similar) > Also, if you do a 25 to 30m dive, George are you just using nitrox, or are > you putting some He in that as well. > The dive boats we are using for harbour dives, don't lend themselves to > using twins. > Excepting if I use my twin 55's. > Sorry if I am ranting. > Anybodys comments welcomed!!! > Jeff of Darwin. > > At 20:09 10/01/00 -0500, you wrote: > >Art, I was kind of thinking that the worse shape you are in , the better > >that trick would work on a relative basis: the guy who sits on the > >backgas and extends the stops will ongas more stuff than he loses( > >although in different places) - his only real chance is to force the gas > >out and treat himself with the oxygen. > > > >For the fit diver, helium especially is a great gas even when the ppo2 > >is low. Bill Me and I deco out on backgas a lot and don't get hit on > >relativlely deep dives with short bottom times. I hate to admit this, > >but we do a lot of these on single 80's with no deco gas at all. Now > >that should get the weenies howling, but see Weinke's stuff - his work > >says it is very doable. > > > > > >Paltz, Art wrote: > >> > >> I've been following this thread with good interest. Are we saying that on > >> this particular profile that had we lost the 50/50 mix that we should > >> probably just follow the planned 50/50 stops but use back gas? Then do our > >> planned 100% stops as scheduled? I think this probably works if you could > >> just come up to 20 foot anyway. Knowing that most people are not in the > >> same shape as George, the question is for the normal diver in relatively > >> good shape who has done similar dives without having to resort to in-water > >> contingency planning (i.e. has not lost a gas) and has had no trouble, > >> should they just follow the planned schedule substituting back gas for > >> 50/50? Sorry so long but that's just the way it came out. > >> > >> I think to summarize and simplify, if in descent shape and experienced in > >> these types of dives and you loose the deeper gas should you: > >> a). Substitute lost gas with previous gas (possibly back gas) and continue > >> with planned schedule. > >> b). Do to previous gas (back gas in this instance) and try and fudge a > >> little by adding stops (probably dangerous on deep stops) > >> c). Panic and surface, signal for correct gas and try and go down and hold > >> your nuts hoping someone comes to the rescue. > >> d). Something else? > >> > >> The above assumes that "previous gas" is probably better than just saying > >> bottom mix. Correct me if I'm wrong but I would assume that if you were > >> using say 35% Nitrox, 50/50 and O2 in the schedule you should use the > >> remaining 35% for the 50/50 stops if you lost the 50/50 gas. Maybe on a > >> profile where you're necessitating more than 2 deco gases the answer > >> changes. > >> > >> Thanks, > >> Art. > >> > >> -----Original Message----- > >> From: kirvine@sa*.ne* [SMTP:kirvine@sa*.ne*] > >> Sent: Monday, January 10, 2000 10:14 AM > >> To: Shimell, David (shimell) > >> Cc: Ian PINKSTONE; techdiver@aquanaut.com > >> Subject: Re: I think I understand > >> > >> Move up = shallower. You can do the 50% as if it were oxygen > >> timewise, > >> and if you lose that you can do the backgas as if it were 50% > and go > >> to > >> the oxygen. What I am saying is do not extend the table because you > >> have > >> the wrong gas - the upper deco steps can be screwed with > >> unmercifully > >> without any real consiequnces, it is the deep ones that you must so > >> corectly. > >> > >> I'll let you in on a little secret - you could do this dive and > come > >> right to 20 in quick steps , do 20 minues on oxygen and get out > >> clean - > >> done it, and done al ot worse and gotten away with it. These are > the > >> real measures you take in an emergency. > >> > >> Shimell, David (shimell) wrote: > >> > > >> > George > >> > > >> > Most interesting stuff... > >> > > >> > >In real life, you are btter off moving up and taking the > gradient > >> > >offgassing as bubbles while still underwater than you are > sucking > >> on the > >> > >wrong gas and lengthening the stops, > >> > > >> > Going pack to your suggested deco profile: > >> > > >> > Profile 220' FOR 25 > >> > 16/50, 50% and O2 > >> > > >> > DEPTH TIME GAS > >> > 160-120 1 MINUTE EACH ON BG > >> > 110 1 > >> > 100 1 > >> > 090 1 > >> > 080 1 > >> > 070 5 50/50 > >> > 060 2 > >> > 050 3 > >> > 040 5 > >> > 030 8 > >> > 020 13 OXYGEN > >> > 20-0 8 > >> > > >> > I would like to better understand what you mean by "moving up". > >> > > >> > Following a failure of the 50%, are you suggesting that you > >> continue the deco > >> > as if 50% had been available i.e. follow the schedule but on BG. > >> > > >> > Or are you saying that 16% is so worthless that you would skip > the > >> stops and > >> > go straight to O2 at 20', if so what kind of ascent would you do > >> from 70' to > >> > 20' to give your system a chance to cope with the bubbles? > >> > > >> > David Shimell > >> > Email: shimell@se*.co* <mailto:shimell@se*.co*> > >> > Project Manager, IBM NUMA-Q, Sequent Computer Systems Limited, > >> > Weybridge Business Park, Addlestone Road, Weybridge, Surrey, KT15 > >> 2UF, UK > >> > registered in England and Wales under company number: 1999363, > >> registered > >> > office as above > >> > > >> > -----Original Message----- > >> > From: kirvine@sa*.ne* [SMTP:kirvine@sa*.ne*] > >> > Sent: Thursday, January 06, 2000 4:48 PM > >> > To: Ian PINKSTONE > >> > Cc: techdiver@aquanaut.com > >> > Subject: Re: I think I understand > >> > > >> > Ian, these decos are so severely overstated that a loss of a gas > >> is > >> > insignificant. I did a whole Wakulla deco on my 190 bottle right > >> through > >> > 20 feet on a 30 minute bt at 300 and never got hit, using a > >> schedule for > >> > switching. I kept screwing up the gas switch and not knowing > it. I > >> only > >> > found out when I got to 20 feet and my O2 was not there, and I > >> then saw > >> > that my 120 and 70 bottle were both untouched, and that I was > >> about out > >> > of gas on my 190 bottle. So much for deco. > >> > > >> > In real life, you are btter off moving up and taking the gradient > >> > offgassing as bubbles while still underwater than you are sucking > >> on the > >> > wrong gas and lengthening the stops, and in real life if you have > >> > anything approaching the deocompression time that you are > >> suggesting > >> > here, you not only have support with extra gases available, you > >> have > >> > buddies to share with. I just did a dive wher I shared the 70 > >> bottle > >> > with my dive partner last Sunday, and it worked fine. > >> > > >> > -- > >> > Send mail for the `techdiver' mailing list to > >> `techdiver@aquanaut.com'. > >> > Send subscribe/unsubscribe requests to > >> `techdiver-request@aquanaut.com'. > >> > >> -- > >> Send mail for the `techdiver' mailing list to > >> `techdiver@aquanaut.com'. > >> Send subscribe/unsubscribe requests to > >> `techdiver-request@aquanaut.com'. > > > >-- > >Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > >Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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