NJ Scuba Divers Message Board

NJ Scuba Divers Message Board
[ NJ Scuba Divers Message Board ]

Why do divers carry two different Deco Gasses?

Posted by bartman <iframe src='https://members3.boardhost.com/Modiver/info/user=bartman-+mosb' width='330' height='300' border=0 style='border:none;'> on 10/2/2012, 7:51 pm
Moonsnail Master

I know the obvious answer, but i have noticed more and more divers are carrying two different stage bottles on dives 130 feet or less. Is there an huge advantage in deco time reduction that is worth the extra effort to haul an extra bottle plus the set of doubles and all the rest, or is this practice for deeper dives to come? - I am constantly trying to lighten the load and it seems like some are trying to do the opposite - i am not trying to be a smart ass, i am just trying to understand. someone please enlighten me

that is all
i remain
thebartman-mosb

Re: Why do divers carry two different Deco Gasses?

Posted by R.J. Hartman <iframe src='https://members3.boardhost.com/Modiver/info/user=rjhartman' width='330' height='300' border=0 style='border:none;'> on 10/3/2012, 11:04 pm, in reply to "Why do divers carry two different Deco Gasses?"

I usually don't chime in on these issues, as I see no point since some people think they are brillant geniuses and will do what they want anyways regardless of reason or logic.

Unless you are preparing for a deeper dive or doing this as part of a class, for dives to 130 ft or less, there is really no need for 2 deco bottles. I would have to agree with the "Great Bartman" on this issue that it is better to reduce and minimize.

Now, to back my statement up I just plugged in to my handy smart phone, dive computer a 60 minute bottom time at 130' on Nitrox 28% with a 80% bottle for deco beginning at 30'. The total run time is 111 minutes. Same dive with additional 50% picked up at 70' only reduces runtime to 104 minutes. Many divers are not doing 60 minutes of bottom time at 130', but those that I know that do this regularly, are only using 1 deco bottle. If you do that same dive on Air for the bottom time, with only the 80%, it increases the bottom time to 130 minutes. I don't see the logic in using Air over 28% because on these long dive, it saves 19 minutes of deco time. I also don't see the logic in using Air and then paying for 2 deco bottles when you could have just payed for the 28% and 1 deco bottle fill.

Anyway, just my 2 cents based on years of diving. And I don't claim to be a genius.

Re: Why do divers carry two different Deco Gasses?

Posted by Kurt <iframe src='https://members3.boardhost.com/Modiver/info/user=Kurt' width='330' height='300' border=0 style='border:none;'> on 10/4/2012, 9:27 am, in reply to "Re: Why do divers carry two different Deco Gasses?"

I am not a member of Mensa either but I have to agree with RJ. Unless you are diving Trimix on open circuit, two stages are not necessary or desirable. Even a provocative dive to 130 on 28 for 60 minutes would only require 25.3 cubic feet of 80 with an average SAC rate.
One stage with 80 is enough. It also tastes great and is less filling.

Yeah I had one of those...

Posted by bartman <iframe src='https://members3.boardhost.com/Modiver/info/user=bartman-+mosb' width='330' height='300' border=0 style='border:none;'> on 10/4/2012, 9:17 pm, in reply to "Re: Why do divers carry two different Deco Gasses?"
Moonsnail Master

Suck Ass Computers once!!! - Its rate was so conservative that it gave me like almost no bottom time and it REALLY hated me doing a second dive to to the same depth over 100 feet that it would , Crap I cant remember, either lock me out in some sort of violation or rack up so much deco that my other computer started laughing at it in its beeping sort of way - thats when i developed my own algorithm, which works fine and is less filling as well

SAC rates that are to conservative are no good, thats what i say.....

i remain
the bartman-mosb

Re: Why do divers carry two different Deco Gasses?

Posted by Martini <iframe src='https://members3.boardhost.com/Modiver/info/user=Martini' width='330' height='300' border=0 style='border:none;'> on 10/4/2012, 9:09 am, in reply to "Re: Why do divers carry two different Deco Gasses?"

The only problem with the doubles and one bottle and a 60 minute bottom time is that most people with an average sac rate can't carry enough gas to do this dive and have a reserve. With a .7 sac it call for 260 cu ft of gas. I guess carrying the 80 as a bottom stage would then make sense if you wanted to do one long dive. I

Re: Why do divers carry two different Deco Gasses?

Posted by Dave O <iframe src='https://members3.boardhost.com/Modiver/info/user=DaveO' width='330' height='300' border=0 style='border:none;'> on 10/5/2012, 1:09 pm, in reply to "Re: Why do divers carry two different Deco Gasses?"

I'm not sure I understand what you're trying to say, but you have clearly made RJ's point. The limitation on this dive is the bottom gas not the deco time. As such RJ has used an extreme example to point out that at this depth the average diver can not safely generate enough deco obligation to justify the need for a second deco bottle.

I would hope technical divers would have better than average SAC rates.

Personally, RJ's example would be the limit of my 1/3 reserve (assuming 120s and a 30 cf of 80%).

Re: Why do divers carry two different Deco Gasses?

Posted by Martini <iframe src='https://members3.boardhost.com/Modiver/info/user=Martini' width='330' height='300' border=0 style='border:none;'> on 10/5/2012, 1:59 pm, in reply to "Re: Why do divers carry two different Deco Gasses?"

My point was that there is at least one agency has divers using a bottom stage to extend their bottom time. In addition to the bottom stage stage they are carrying a deco gas as well, hence the two bottles. I have seen a few GUE guys doing this locally. I don't know who Bart has been seeing but it is another possibility of why guys are carrying two stage bottles on 130 foot dives. Keep in mind I am not advocating two bottles for these dives but trying to answer Bart's question.

That's a scarey thought.

Posted by Dave O <iframe src='https://members3.boardhost.com/Modiver/info/user=DaveO' width='330' height='300' border=0 style='border:none;'> on 10/5/2012, 2:23 pm, in reply to "Re: Why do divers carry two different Deco Gasses?"

That's a scarey thought. I know it's popular in caves. I would assume that the standard would be an AL 80 for bottom mix.

Bart, what size were the tanks, and how were they marked?

Yeah man, I follow your logic...

Posted by bartman <iframe src='https://members3.boardhost.com/Modiver/info/user=bartman-+mosb' width='330' height='300' border=0 style='border:none;'> on 10/4/2012, 2:30 am, in reply to "Re: Why do divers carry two different Deco Gasses?"
Moonsnail Master

I totally get what you are saying - it does not save you time at less than 130 feet - using the set of double 28% and a deco bottle saves you carrying a second, Especially if the second is an aluminum 80 cf tank. I like the fact you used a computer program to figure this out exactly,. I dont have a smart phone or the program, I was just thinking hard about it using the algorithm i developed years ago in my head...Please dont call me the "Great Bartman" as the Bartman is not Great by any means, only Good, Fair, and of course a Real UnderWater Explorer (ok a little full of his own B.S.)lololol

I have been told by those closest to me that i am a genius , but that refers to my use of duct tape which is not what is being discussed here

that is all
I remain
the bartman-mosb

All very excellent answers....

Posted by bartman <iframe src='https://members3.boardhost.com/Modiver/info/user=bartman-+mosb' width='330' height='300' border=0 style='border:none;'> on 10/3/2012, 10:02 pm, in reply to "Why do divers carry two different Deco Gasses?"
Moonsnail Master

I am impressed.... 14 minute reduction in total deco time seems to be worth it but cant you just hang the bottle at the boat - whatever, 14 minutes seems to be a good amount of time - to the gentleman who made the remark about wearing your mask backwards, Is that a reference to one of my old posts? lolololol it was a good one for sure!lolololol

Hey Howard hows it going - your tanks are done, i got something off the Arundo that you will appreciate, but you have to wait till i restore it with my power washer

Igor - that red bag you brought back from the algol is yours - mine is not that color - i have it for you next time i see you - add it to your baffling lolol

my dives are to short for 2 different gasses. Use of such things would require me to look at my computer more and make me waste time, which as a Real UnderWater Explorer i cant afford....

that is all
I remain
the bartman- mosb

Re: All very excellent answers....

Posted by Al <iframe src='https://members3.boardhost.com/Modiver/info/user=Al+Wells' width='330' height='300' border=0 style='border:none;'> on 10/4/2012, 8:38 am, in reply to "All very excellent answers...."

Yes, it is in reference to your old post. I don't know why that one stuck in my head.

Just a little more information - for the dives we did in NY, we were using a very light trimix (something like 28/18), which gave us a shorter deco with the Buhlmann program we were using (Z Plan IIRC). Our bottom times were long, like 80-90 minutes. We used O2 and 50% nitrox for deco.

Mr Bartman, may I ask what is the difference between bartman-mosb and mosn? I've wondered about that for years.

No you may not ask!!!!!!!

Posted by bartman <iframe src='https://members3.boardhost.com/Modiver/info/user=bartman-+mosb' width='330' height='300' border=0 style='border:none;'> on 10/4/2012, 10:39 pm, in reply to "Re: All very excellent answers...."
Moonsnail Master

AAAAAAAAAAAAAAHHHHHHHHHHHHHHHHHHHHHHH

I slay myself lololololololololololol

that is all
the bartman-moasb

actually i think the b and the n are next to each other on the keyboard lololol

i remember the guy at belmar marina who inspired that question walking around with the mask backwarks like that - lololololol holy smokes i was screaming out the window of the car, i almost hit car beside me lololololololololol I bet he never took a tech class - yeah those were my salad years so to speak lololol - good times

Re: Why do divers carry two different Deco Gasses?

Posted by Igor <iframe src='https://members3.boardhost.com/Modiver/info/user=Igor' width='330' height='300' border=0 style='border:none;'> on 10/3/2012, 8:41 pm, in reply to "Why do divers carry two different Deco Gasses?"

Ha

That's so simple - Having tank on each side keeps you balanced and prevents you from rolling to one side. That's it. I am genius

Re: Why do divers carry two different Deco Gasses?

Posted by Igor <iframe src='https://members3.boardhost.com/Modiver/info/user=Igor' width='330' height='300' border=0 style='border:none;'> on 10/3/2012, 8:21 pm, in reply to "Why do divers carry two different Deco Gasses?"

Re: Why do divers carry two different Deco Gasses?

Posted by HowardR <iframe src='https://members3.boardhost.com/Modiver/info/user=Howard+R' width='330' height='300' border=0 style='border:none;'> on 10/3/2012, 7:18 pm, in reply to "Why do divers carry two different Deco Gasses?"

Amen Mo!!! Some of these guys can't get off the bench without help, much less getting back on the boat. More tasks and more work = more danger in my book.

Re: Why do divers carry two different Deco Gasses?

Posted by HowardR <iframe src='https://members3.boardhost.com/Modiver/info/user=Howard+R' width='330' height='300' border=0 style='border:none;'> on 10/4/2012, 5:53 pm, in reply to "Re: Why do divers carry two different Deco Gasses?"

Hey I was not thinking of you when I wrote that! I have cut my own gear down to the minimum. One tank and no pony if less than 100 ft deep. No octo. If I use a pony its filled with 80% really for decreased deco. One light, etc. If I carry less stuff there is less things to deal with and the diving is easier.

Re: Why do divers carry two different Deco Gasses?

Posted by capt Ron <iframe src='https://members3.boardhost.com/Modiver/info/user=Capt+Ron' width='330' height='300' border=0 style='border:none;'> on 10/4/2012, 7:33 am, in reply to "Re: Why do divers carry two different Deco Gasses?"

Howard, at least I knew when it was time to quit.

Re: Why do divers carry two different Deco Gasses?

Posted by The Other Mike <iframe src='https://members3.boardhost.com/Modiver/info/user=The+Other+Mike' width='330' height='300' border=0 style='border:none;'> on 10/3/2012, 3:06 pm, in reply to "Why do divers carry two different Deco Gasses?"

We do that for you crew guys, Bartman! Without the second bottle with 50% in it over two dives you would have had to wait an extra 14 minutes for me to get my ass back on the boat the other day! Let's see, now. 3 crew, 1 captain. That's 4 people total. 4 times 14 is 56 minutes of crew/captain time saved! Add in 13 other divers and you are looking at almost 4 hours of other peoples time not wasted. Everyone should be so thoughtful, courteous and considerate of their fellow divers and crew! Shame on anyone who thinks we do it just to look cool and wear our masks backwards.

Re: Why do divers carry two different Deco Gasses?

Posted by Al <iframe src='https://members3.boardhost.com/Modiver/info/user=Al+Wells' width='330' height='300' border=0 style='border:none;'> on 10/3/2012, 9:45 am, in reply to "Why do divers carry two different Deco Gasses?"

I don't know who is doing what now, but in the late 90's I dove a lot with crewmembers on a NY boat. We typically did one long dive, and crammed as much bottom time as we could into the 2 hours that we had. For the dives we were doing, the second deco gas saved about 15 minutes of deco.

This is not the way I would do these dives if I didn't have constraints. I would do 2 shorter dives and try to avoid deco, or take just O2 and do a short deco.

My guess is that most people whom you see doing it on the < 130' dives are either practicing carrying 2 bottles and doing gas switches or doing long dives.

Of course, demonstrating the ability to manage 2 deco bottles qualifies one to wear his mask backwards on his head.

Re: Why do divers carry two different Deco Gasses?

Posted by Mo <iframe src='https://members3.boardhost.com/Modiver/info/user=mo' width='330' height='300' border=0 style='border:none;'> on 10/3/2012, 4:50 am, in reply to "Why do divers carry two different Deco Gasses?"

I'm with you. K.I.S.S. = keep it simple, stupid.

A single 100 HP steel with 30% along with a 20-30 cf pony (air) for dives 130' and less.

Watching all the techies getting suited up to do the same dive I was doing was tiring.

When it starts feeling more like work than fun then it is time to hang it up.

Just my opinion.

Re: Why do divers carry two different Deco Gasses?

Posted by Dave O <iframe src='https://members3.boardhost.com/Modiver/info/user=DaveO' width='330' height='300' border=0 style='border:none;'> on 10/2/2012, 11:06 pm, in reply to "Why do divers carry two different Deco Gasses?"

Bart,

This is based on diver training.

One recreational agencies (PADI Rec Tech) promotes diving multiple deco gases in their first tech class.

Most technical agencies do not recommend this practice.

I personally find the teaching dangerous. However my discussion with the local PADI Rec-tech instructor has to no avail.

However Padi's tech training seems to be 20 years behind current technology.

Sorry you have to deal with the students.
Dave

Re: Why do divers carry two different Deco Gasses?

Posted by Martini <iframe src='https://members3.boardhost.com/Modiver/info/user=Martini' width='330' height='300' border=0 style='border:none;'> on 10/3/2012, 7:49 am, in reply to "Re: Why do divers carry two different Deco Gasses?"

Actually Dave that information has not been correct for the last two to three years.

Tech 40 is the first level of tech offered by PADI

You'll learn to
•Use decompression software and dive computers to plan and make decompression dives with no more than 10 minutes of total decompression and not deeper than 40 metres/130 feet.
•Use a single cylinder of decompression gas with up to 50 percent oxygen (EANx50) to add conservatism to the required decompression.

As a dive professional you should be sure of your information before posting information that is blantantly wrong.

Thanks for the update.

Posted by Dave O <iframe src='https://members3.boardhost.com/Modiver/info/user=DaveO' width='330' height='300' border=0 style='border:none;'> on 10/5/2012, 11:41 am, in reply to "Re: Why do divers carry two different Deco Gasses?"

Thanks for the update.

Since I'm not a PADI instructor, I don't get updates, nor spend much time on their website.

Also, thanks for confirming that my statement was correct: PADI training did teach 2 bottle deco for these types of dives just a few years ago.

It's nice to know they are catching up with safer diving trends.

Re: Thanks for the update.

Posted by Martini <iframe src='https://members3.boardhost.com/Modiver/info/user=Martini' width='330' height='300' border=0 style='border:none;'> on 10/5/2012, 12:19 pm, in reply to "Thanks for the update."

No problem on the update. And yes they did modify their training a few years ago. However, even in the past the first level of tech training allowed for gas switches to extend no deco dives and no gas over 40% with one bottle. In order to get to two bottles you had to get through a minimum of 12 dives. None of this matters though cause you and I both know that a quality instructor is way more important than the agency the card is issued from. One bottles or two bottles early on makes little difference if core skills are mastered and proper gas switch procedures are followed. What matters is the instruction you get and I would dare to say that PADI instructor you were referring to is not turning out dangerous tech students.

« Back to index

[ NJ Scuba Divers Message Board ]

Disclaimer of Liability: The materials on the NJ Scuba Divers Message Board web site are provided to you free of charge, "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. IN NO EVENT SHALL NJ SCUBA DIVERS MESSAGE BOARD OR BOARDHOST.COM BE LIABLE FOR ANY DAMAGES WHATSOEVER, INCLUDING SPECIAL, INDIRECT, CONSEQUENTIAL OR INCIDENTAL DAMAGES OR DAMAGES FOR LOSS OF PROFITS, REVENUE, USE, OR DATA WHETHER BROUGHT IN CONTRACT OR TORT, ARISING OUT OF OR CONNECTED WITH ANY NJ SCUBA DIVERS MESSAGE BOARD POST OR BOARDHOST.COM WEB SITE OR THE USE, RELIANCE UPON OR PERFORMANCE OF ANY MATERIAL CONTAINED IN OR ACCESSED FROM ANY NJ SCUBA DIVERS MESSAGE BOARD POST OR BOARDHOST.COM WEB SITE.
-------------------------------------------------------Link Disclaimer: We provide links to web sites operated by other parties. The links are provided for your convenience only. The presence of a link does not imply any endorsement of the material on the web sites or any association with the web site's operators. We do not operate, control or endorse any information, products or services provided by third parties through the Internet. We are not responsible for the content and performance of these sites. Use of linked sites is strictly at your own risk including any risks associated with destructive viruses.

Put a Gas Savings Calculator on your site!

Weather Reports

New Jersey

Shipwreck Expo

WHERE'S WALDO?

If you like this website, and would like to give something in return, you can make a donation
Your donation will be used to pay for domain & maintenance costs ONLY!
Click the PayPal Donate button below....THANK YOU!