Mailing List Archive Mailing List Archive
Sean, Good point on the deco at 10. I call it a 10 ft stop but is in reality a 15 ft stop. And you just never know. I suppose I can find an O2 meter that would read higher than 100%........ Steve -----Original Message----- From: Sean M. Cary [mailto:SMCARY@mi*.co*] Sent: Thursday, June 10, 1999 7:40 AM To: Shimell, David (shimell); Steve Hogan Cc: techdiver@aquanaut.com Subject: Re: Re Last Stop Depth Well, unless he's using over 100% 02, then ANY stop at 10' would be a waste. I think Bill Stone was able to get more then 100% in a tank, but it requied so much cake eating , that no mere ahh mortal could redo the fill! Sean -----Original Message----- From: Shimell, David (shimell) <shimell@se*.co*> To: Sean M. Cary <SMCARY@MI*.CO*>; Steve Hogan <Steve.Hogan@tr*.co*> Cc: techdiver@aquanaut.com <techdiver@aquanaut.com> Date: Thursday, June 10, 1999 7:05 AM Subject: RE: Re Last Stop Depth >Sean > >Weird, I would have thought everyone did their O2 stops at 6m/20'. However, >I don't think Steve actually mentioned which gasses he was using for this >"real mix" dive. Hopefully he was using the "proper" ones so your point >would be valid. > >David Shimell >Project Manager, Sequent Computer Systems Ltd., Sandton, South Africa. >Email: shimell@se*.co* <mailto:shimell@se*.co*> > >-----Original Message----- >From: Sean M. Cary [SMTP:SMCARY@MI*.CO*] >Sent: Wednesday, June 09, 1999 11:16 PM >To: Steve Hogan; shimell@se*.co* >Cc: techdiver@aquanaut.com >Subject: Re: Re Last Stop Depth > >Why do a 10' stop when the PO2 of 100% is lower then 1.6? I make my last >stop 20fsw. > >Sean > > >-----Original Message----- >From: Steve Hogan <Steve.Hogan@tr*.co*> >To: shimell@se*.co* <shimell@se*.co*> >Cc: techdiver@aquanaut.com <techdiver@aquanaut.com> >Date: Wednesday, June 09, 1999 4:40 PM >Subject: RE: Re Last Stop Depth > > >>David, >> >> >>>Occasionally, I do a multi-level, bimble-around-the-place dive and dive an >>>air computer but deco on O2. I'm comfortable to leave the computer on the >>>line or bend it when I've done sufficient deco. Note: this is based on >>rules >>>of thumb which allow me to do sufficient deco. >> >>I have done many dives using mix (usually 18/40) with 50/50 deco gas >>and an air computer. Like you I am just wandering around and I use the >>air computer as a guide for the deco. I have found that the air only >>schedule >>is longer than a mix schedule with deep stops and deco gas. There are a few >>rules >>though. 1. Do the deep stops. 2. Use the deco gas (50/50) for all depths >>shallower >>than 70 ft. 3. perform the dive like a multilevel dive (no sawtooth stuff) >>This is only for some dives where a set of tables is not really >>necessary (like wnadering around on a reef where the bottom is known but is >>highly variable) >> >>Do not misunderstand me, when on a real mix dive (when I expect that the >>stops will be greater than 10-20 ft) then the dive is planned and executed >>on >>tables (and I bend my poor computer....backup depth gauge/timer. On a dive >>I did Sunday the computer informed me that I needed to stay at 20 ft while >>on my 10 ft (table) stop and will finally clear 60 hrs after getting out of >>the water.... I am glad it is not adaptive...<grin> It still indicated 37 >>min >>of deco left when I got out of the water) >> >>Steve >> >> >> >>David Shimell >>Project Manager, Sequent Computer Systems Ltd., Sandton, South Africa. >>Email: shimell@se*.co* <mailto:shimell@se*.co*> >> >>-----Original Message----- >>From: David Reinhard [SMTP:reinhard@oc*.co*.au*] >>Sent: Wednesday, June 09, 1999 5:51 AM >>To: techdiver@aquanaut.com >>Subject: Re Last Stop Depth >> >>Thanks to all who have contributed to my knowledge with your replies. >>Unfortunately there are too many replies for me to respond personally to >>all of you >> A number of you have pointed out that air is a poor choice for >>decompression. I fully agree, and it is not my practice to do so. It was >>remiss of me not to point that out in my original post. Below is my reply >>to David Shimell which I had intended to go to the list but I think may >>have only gone to his personal email address. >> >>At 01:19 07-06-99 -0700, you wrote: >>>David >>> >>>The reason there is a significant difference between a last stop at 6 vs. >3 >>>is that you are doing the deco on air which is a poor choice. >> >>In reality I don't do my deco on air. I was just running hypothetical >>profiles to see the effect of different stop depths. While I naturally >>expected a difference it was the magnitude of the difference that surprised >>me. While the pressure difference between 3m and 6m is not insignificant I >>was particularly surprised that 1m could make such a big difference. >> You are quite right, of course. Deco should be done on an >>appropriate >>nitrox mix and/or pure o2. But being very cautious I still deco to the air >>schedule and take the safety benefit rather than do accelerated deco. So by >>choosing 6m rather than 3m I have been spending a lot of extra time in the >>water. However due to the large ocean swells we often encounter where we >>are diving it may at times still be appropriate to go for the 6m stop. >> >>Thanks for your comments, Dave. >> >> I also received the following comment which I am particularly interested >>in:- >> >>(quote) >>"If you have done sufficient deco, then spending further time in the water >>is >>increasing your risk. OK, this risk is small but never-the-less a risk and >>it bites some people. Doing excessive deco is therefore not adding >safety." >> >>Do others concur with this idea? As I said above I deco on nitrox but >>operate on an air schedule. In effect this would constitute "excessive >>deco" for the gas I am using. So is there a problem with this practice? >>Does doing extra deco increase or decrease your risk? If you are going to >>increase your deco at what point should you do it, eg only on the last >>stop? Come to think of it Pyle stops are in effect increased deco beyond >>that required by the tables. One of the thoughts I have had about this is >>what actually constitutes "excess" deco. Given the variability in deco >>tables what constitutes the "right amount" of deco on one table could >>constitute "too much" deco on another table. Given that we don't really >>know what the "right amount" of deco actually is for any particular >>individual on a particular dive profile how can we hope to know what is >>"too much" deco. (The only definition of "right amount" of deco I can think >>of is that amount which leaves you unbent after a dive - but you don't >>really know that until after the dive, since tables are merely a hopeful >>guideline which fortunately are right most of the time). >> >> In reality I would be very surprised if a small variation in stop >>depth >>made a large practical difference to the decompressing diver. If this were >>the case I am sure we would have a lot more bent divers (hmmm... on the >>other hand we do have a number of divers that get bent while apparently >>following the tables... I wonder...). As has been pointed out the use of >>nitrox/o2 for deco significantly reduces the differences I observed, so it >>is even less of a problem to deco diving than it would initially seem. >> >> It has also been mentioned that Zplan adjusts all stop depths if you >>change the last stop depth. I had noticed this and have found it >>inconvenient compared to other software that keeps the same standard stop >>depths and only adjusts the last stop. I guess I didn't consider the >>possible effect of this change on the total deco time. I noticed another >>post on this list about a new shareware deco program that does not do this, >>so I would be interested in having a look at that program when it is >>available. >> >> >>Thanks to all, regards, Dave. >>-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- >>Ocean Internet - "The Quality ISP" >>http://www.ocean.com.au/info.html >> >>-- >>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'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]