What pressure in deco bottles ???

richieoflynn · March 11th, 2008, 10:43 PM

Howdy folks,

Just a quick one, what pressure would you fill an ali 40 and ali 80 to so they float nicely up under your arm ? Obviously if you fill them to 200 bar then they're slightly negative and hang down a bit so would lets say 160 bar be about right ?

Would it be a standard GUE procedure to fill to this lower pressure or would you always fill to the normal working pressure of the cylinder ? Obviously you have to look at your deco and check whether or not you'll have enough gas but that aside, diving with a bottle tidy up under yor arm makes more sense yeah

Thanks,

Richie.

Cyrille · March 11th, 2008, 11:16 PM

Hi Richie,

Typically you can fill S40 and S80 up to 200 bars.

Provided you have a balanced rig, having 1 x S40 and 2 x S80 will not impair your buoyancy. Slightly negative when full, slightly positive when empty.

Therefore fill up to 200 bars if you can (i.e. having a booster for O2, etc).

What matters is to have sufficient gas for your deco...

Rock bottom time...

Kind regards.

Cyrille

**keri.lewis** · March 11th, 2008, 11:29 PM

Richie

As always, the answer is - it depends on what you are looking for...

If you take the "normal" buoyancy change of an AL80 +/-3lbs and add on the buoyancy of your reg, stage kit etc. then you are likely to find that the bottle is 4-5lbs negative when full or Air or nitrox (less with mix). now that's not a lot.. but it will hang down when you are hovering.

I take it from your post that you are looking to have the bottle neutral to positive so that it floats up to the armpit. It would not be significantly less drag-causing as long as the stage bottle is rigged so it hangs in a streamlined fashion.

The total buoyancy swing of 6lbs over 200 bar means that you would be in the 30-60 bar fill range. With a 40 - the reg has an even more pronounced effect and I am not sure of the benefit - but having a bottle so empty as to be neutral to positive means that it would be almost empty.

You'll see from other threads on the forum that for many people the main concern is for bottles that are too "floaty" at the end of the dive - rather than negative at the begining.

My experience is that the best thing is to fill them properly, and make sure they are correctly positioned and balanced in the stage kit so they drag as little as possible. You can always put a hand on them if you need to go through a small aperture.

**neilh** · March 11th, 2008, 11:29 PM

As Cyrille says I'd have thought the key is that you have enough gas for your plan. If you calculate what you need and an ali40 would cover it then it's going to be nicer to handle than a full ali80.

Also you might not want to throw away 40-50 bar of gas just to get the bottle riding nicely at first

lizardland · March 12th, 2008, 12:33 AM

For deco bottles the above is good advice. For penetration stage bottles, fill until they start creaking

*JohnKendall* · March 12th, 2008, 12:54 AM

Quote: (Originally Posted by lizardland)

For deco bottles the above is good advice. For penetration stage bottles, fill until they start creaking

Or just full them all up, and be glad to have the gas if you need it. It's much nicer to come up with a few bars unused than come up wishing you had a bit more.

J

se2schul · March 12th, 2008, 04:52 AM

If you really, really want lighter stage bottles, just put helium in them.
I think you'll find that as you dive stages more often that heavy stages of nitrox get easier and easier to carry.

Diving Dave · March 12th, 2008, 07:59 AM

Hey Richie,

I'm sure you already know this but I thought it might be worth a mention anyway. If you're using one bottle you can wrap the bottom snap under the hose covered bit on the rigging kit. This takes in some of the slack that's needed for multiple bottles and holds the bottle in a bit tighter to your body.

As for filling I'd just echo what's already been said. Fill em up.

How's the diving around your way? Really want to make it over to Ireland at some point!

Ali Fikree · March 12th, 2008, 10:11 AM

I boost my S40 to 250 bar except for O2 which I keep at 200 bar. If I am using an S80 for a 21m bottle, I add some helium which make it lighter. The mix is then 50/25-35.

A

richieoflynn · March 12th, 2008, 11:11 AM

Hi everyone,

Thanks for all the replies. Always good to hear your opinions. I have an 80 and was playing around with it but as it's full, I found it hangs a bit underneath me. Will try looping the bottom boltsnap to pull it in a bit tighter and see how that goes.

Diving Dave : The diving is really good around the south of Ireland. Anywhere out of Baltimore in West Cork can be really nice if the weather is good (Kowloon Bridge, U260). There's also a new guy over in Youghal, East Cork with a 13m hardboat with lift and compressor that does some really nice wreck diving, min. depth 30m up to 70 / 80m. Be sure to give me a shout if you ever make it over. He's a very nice guy to go out diving with. Youghal Dive Charters - Sea Hunter - Deep Sea Diving and Fishing - Youghal, Co. Cork, Ireland

Richie.

March 11th, 2008, 10:43 PM	#1 (permalink)
richieoflynn(Offline) New Member Join Date: May 2007 Location: Ireland Posts: 53	What pressure in deco bottles ??? Howdy folks, Just a quick one, what pressure would you fill an ali 40 and ali 80 to so they float nicely up under your arm ? Obviously if you fill them to 200 bar then they're slightly negative and hang down a bit so would lets say 160 bar be about right ? Would it be a standard GUE procedure to fill to this lower pressure or would you always fill to the normal working pressure of the cylinder ? Obviously you have to look at your deco and check whether or not you'll have enough gas but that aside, diving with a bottle tidy up under yor arm makes more sense yeah Thanks, Richie.

March 11th, 2008, 11:16 PM	#2 (permalink)
Cyrille(Offline) New Member Join Date: Apr 2006 Location: Ijsselstein, The Netherlands Posts: 112	Hi Richie, Typically you can fill S40 and S80 up to 200 bars. Provided you have a balanced rig, having 1 x S40 and 2 x S80 will not impair your buoyancy. Slightly negative when full, slightly positive when empty. Therefore fill up to 200 bars if you can (i.e. having a booster for O2, etc). What matters is to have sufficient gas for your deco... Rock bottom time... Kind regards. Cyrille __________________ "Scuba diversdescend to look around themselves, freedivers descend to look within themselves."

March 11th, 2008, 11:29 PM	#3 (permalink)
keri.lewis(Offline) Back in the water.. Join Date: Nov 2007 Location: Hampshire Posts: 407	Richie As always, the answer is - it depends on what you are looking for... If you take the "normal" buoyancy change of an AL80 +/-3lbs and add on the buoyancy of your reg, stage kit etc. then you are likely to find that the bottle is 4-5lbs negative when full or Air or nitrox (less with mix). now that's not a lot.. but it will hang down when you are hovering. I take it from your post that you are looking to have the bottle neutral to positive so that it floats up to the armpit. It would not be significantly less drag-causing as long as the stage bottle is rigged so it hangs in a streamlined fashion. The total buoyancy swing of 6lbs over 200 bar means that you would be in the 30-60 bar fill range. With a 40 - the reg has an even more pronounced effect and I am not sure of the benefit - but having a bottle so empty as to be neutral to positive means that it would be almost empty. You'll see from other threads on the forum that for many people the main concern is for bottles that are too "floaty" at the end of the dive - rather than negative at the begining. My experience is that the best thing is to fill them properly, and make sure they are correctly positioned and balanced in the stage kit so they drag as little as possible. You can always put a hand on them if you need to go through a small aperture. __________________ Even a "bad" day diving beats a day in the office... Keri The more I learn.. the more ignorant I realise I am..

March 11th, 2008, 11:29 PM	#4 (permalink)
neilh(Offline) Haemoglobin on the bus... Join Date: Nov 2005 Location: Barnsley, UK Posts: 1,900	As Cyrille says I'd have thought the key is that you have enough gas for your plan. If you calculate what you need and an ali40 would cover it then it's going to be nicer to handle than a full ali80. Also you might not want to throw away 40-50 bar of gas just to get the bottle riding nicely at first Last edited by neilh; March 11th, 2008 at 11:31 PM.

March 12th, 2008, 12:33 AM	#5 (permalink)
lizardland(Offline) LCS Join Date: Nov 2005 Location: Evidently Chickentown Posts: 595	For deco bottles the above is good advice. For penetration stage bottles, fill until they start creaking __________________ Can you imagine drifting along in the sea with your mouth open and a load of f***ing plankton going in? You'd like it, would you? www.westons-cider.co.uk The Lot isn't the only place to dive: http://www.lulu.com/content/613554

March 12th, 2008, 12:54 AM	#6 (permalink)
JohnKendall(Offline) GUE Instructor/DIRX Moderator Join Date: Nov 2005 Location: Cambridge, UK Posts: 1,102	Quote: (Originally Posted by lizardland) For deco bottles the above is good advice. For penetration stage bottles, fill until they start creaking Or just full them all up, and be glad to have the gas if you need it. It's much nicer to come up with a few bars unused than come up wishing you had a bit more. J __________________ John Kendall http://www.guetraining.com/ GUE Instruction, Santi and Halcyon Equipment NEW - Online Santi Shop

March 12th, 2008, 04:52 AM	#7 (permalink)
se2schul(Offline) New Member Join Date: Mar 2007 Location: Ottawa, Canada Posts: 70	If you really, really want lighter stage bottles, just put helium in them. I think you'll find that as you dive stages more often that heavy stages of nitrox get easier and easier to carry.

March 12th, 2008, 07:59 AM	#8 (permalink)
Diving Dave(Offline) New Member Join Date: Oct 2006 Location: Muscat, Oman Posts: 116	Hey Richie, I'm sure you already know this but I thought it might be worth a mention anyway. If you're using one bottle you can wrap the bottom snap under the hose covered bit on the rigging kit. This takes in some of the slack that's needed for multiple bottles and holds the bottle in a bit tighter to your body. As for filling I'd just echo what's already been said. Fill em up. How's the diving around your way? Really want to make it over to Ireland at some point! __________________ Dave

March 12th, 2008, 10:11 AM	#9 (permalink)
Ali Fikree(Offline) New Member Join Date: Dec 2005 Location: Dubai Posts: 465	I boost my S40 to 250 bar except for O2 which I keep at 200 bar. If I am using an S80 for a 21m bottle, I add some helium which make it lighter. The mix is then 50/25-35. A __________________ Four wheels move the body, two wheels move the soul

March 12th, 2008, 11:11 AM	#10 (permalink)
richieoflynn(Offline) New Member Join Date: May 2007 Location: Ireland Posts: 53	Hi everyone, Thanks for all the replies. Always good to hear your opinions. I have an 80 and was playing around with it but as it's full, I found it hangs a bit underneath me. Will try looping the bottom boltsnap to pull it in a bit tighter and see how that goes. Diving Dave : The diving is really good around the south of Ireland. Anywhere out of Baltimore in West Cork can be really nice if the weather is good (Kowloon Bridge, U260). There's also a new guy over in Youghal, East Cork with a 13m hardboat with lift and compressor that does some really nice wreck diving, min. depth 30m up to 70 / 80m. Be sure to give me a shout if you ever make it over. He's a very nice guy to go out diving with. Youghal Dive Charters - Sea Hunter - Deep Sea Diving and Fishing - Youghal, Co. Cork, Ireland Richie.