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DIR Kit questions Agonising over what to buy, ask other divers what they have done and what they have found. Bought something great or new - tell us.
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April 13th, 2007, 12:12 PM
| #1 (permalink) |
| Custom User Title  Join Date: Nov 2005 Location: Denmark
Posts: 437
   | Why luxfer S080 doesn't work in open water Hi, I've been doing a few dives with a stage tank for use on the bottom to preserve what is in the doubles and I've noticed that the stage tank, a luxfer S080 get very light when it's almost empty espcially when diving trimix. A look at luxfers specification chart confirms that the tanks are 2kg positive when empty. Now this is GREAT for cave diving because you carry a lot of tanks and often only breathe them down to 2/3 so they're still near neutral. But in open water i often empty the tanks and then they get to be a pain, so I was thinking of switching to S80N they're a little heavy at the start of the dive but are neutral when you reach the end of the dive. What are your thoughts, should i just stop emptying the stages and rely on backgas or just add more weight so i can stay down with empty tanks? Cheers Jonas |
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April 13th, 2007, 12:17 PM
| #2 (permalink) |
| GUE  Join Date: May 2006 Location: London
Posts: 439
| Jonas, add another 1 kg v-weight to your rig to compensate. Also, if you're sending up a DSMB towards the end of your dive, then just clip the empty AL80 to the line and let it go up. Alternatively, you could nose-clip the empty to either your rear d-ring or to your waist d-ring (obviously, be careful not to let go prematurely). Best, John. Quote: (Originally Posted by jluttichau)  Hi, I've been doing a few dives with a stage tank for use on the bottom to preserve what is in the doubles and I've noticed that the stage tank, a luxfer S080 get very light when it's almost empty espcially when diving trimix. A look at luxfers specification chart confirms that the tanks are 2kg positive when empty. Now this is GREAT for cave diving because you carry a lot of tanks and often only breathe them down to 2/3 so they're still near neutral. But in open water i often empty the tanks and then they get to be a pain, so I was thinking of switching to S80N they're a little heavy at the start of the dive but are neutral when you reach the end of the dive. What are your thoughts, should i just stop emptying the stages and rely on backgas or just add more weight so i can stay down with empty tanks? Cheers Jonas |
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April 13th, 2007, 12:31 PM
| #3 (permalink) |
| Custom User Title Join Date: Nov 2005 Location: Denmark
Posts: 437
| Quote: (Originally Posted by JGrogan) Also, if you're sending up a DSMB towards the end of your dive, then just clip the empty AL80 to the line and let it go up. Yeah that was my plan to do that on this recent dive, but after fighting with the bottle for 5 minutes i gave up, I guess I just have to work up some experience with this configuration to make it go smoothly.Alternatively, you could nose-clip the empty to either your rear d-ring or to your waist d-ring (obviously, be careful not to let go prematurely). Cheers Jonas |
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April 13th, 2007, 12:34 PM
| #4 (permalink) |
| Towboy  Join Date: Nov 2006 Location: berlin, europe
Posts: 244
| Quote: (Originally Posted by jluttichau) Now this is GREAT for cave diving because you carry a lot of tanks and often only breathe them down to 2/3 so they're still near neutral. Quite common to breath bottomstages down in cavediving when doing a multi-stage dive.Also common to empty multiple halfempty stages, usually on short cavedives or openwater, socalled " reste-tauchen " with pidgeon english it could translate to "carryovers-diving" ? What John Grogan recommends, I may add 2kg for such dives, but recently I forgot about this ending up with four empty stages, it still was manageable, not comfortably, but it was. Sure makes sense to keep the idea of a balanced-rig well in sight. Dunno how much buyoyant it becomes, with valve and reg it may more like +0,5kg? HTH, Hoffi Last edited by nskdrs; April 13th, 2007 at 12:56 PM. Reason: usual typothingie |
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April 13th, 2007, 12:55 PM
| #5 (permalink) |
| Always lowering the tone  Join Date: Dec 2005 Location: Cardiff, UK
Posts: 340
| Quote: (Originally Posted by jluttichau) a luxfer S080 get very light when it's almost empty espcially when diving trimix. I don't suppose it matters whether it contained trimix or krypton once it's empty  Quote: (Originally Posted by jluttichau) A look at luxfers specification chart confirms that the tanks are 2kg positive when empty. I'm pretty sure they're only slightly bouyant once you've added a valve and regulator - not 2kg |
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April 13th, 2007, 12:58 PM
| #6 (permalink) |
| Custom User Title Join Date: Nov 2005 Location: Denmark
Posts: 437
| Quote: (Originally Posted by NickB) I don't suppose it matters whether it contained trimix or krypton once it's empty Well i wrote ALMOST empty.. and if it was krypton you wouldn't care if it was empty  Quote: (Originally Posted by NickB) I'm pretty sure they're only slightly bouyant once you've added a valve and regulator - not 2kg Probably not 2 kg and it also depends on salinity, but the point is that it's a pain to handle under water.Cheers Jonas |
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April 13th, 2007, 01:00 PM
| #7 (permalink) |
| andersbomholdt.dk  Join Date: Dec 2005 Location: Copenhagen, Denmark
Posts: 156
| Quote: (Originally Posted by JGrogan) add another 1 kg v-weight to your rig to compensate. Also, if you're sending up a DSMB towards the end of your dive, then just clip the empty AL80 to the line and let it go up. Seems to be the common solution, but why not use the S80N?Is it too heavy at the beginning at the dive? Cheers Anders |
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April 13th, 2007, 01:02 PM
| #8 (permalink) |
| Always lowering the tone Join Date: Dec 2005 Location: Cardiff, UK
Posts: 340
| Quote: (Originally Posted by jluttichau) Probably not 2 kg and it also depends on salinity, but the point is that it's a pain to handle under water. I guess I haven't breathed mine down below around 50 bar in the sea but I have breathed it down close to empty in a freshwater quarry just to get some idea of what the bouyancy characteristics were like. I have to say I didn't find it troublesome. I much prefer my old-style 7l Luxfer though :D See left <--- |
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April 13th, 2007, 01:07 PM
| #9 (permalink) |
| New Member  Join Date: Dec 2005 Location: Norway
Posts: 19
| Quote: (Originally Posted by jluttichau) Yeah that was my plan to do that on this recent dive, but after fighting with the bottle for 5 minutes i gave up, I guess I just have to work up some experience with this configuration to make it go smoothly. As you say it's just training. I never add weights when diving stages since you usually have quite a lot of back gas to compensate the positive bouyancy from the stage bottle.Cheers Jonas /Robert |
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April 13th, 2007, 01:18 PM
| #10 (permalink) |
| Doing It Caverkevin  Join Date: Nov 2005 Location: North Kackilackie
Posts: 360
| Quote: (Originally Posted by NickB) I don't suppose it matters whether it contained trimix or krypton once it's empty  Pretty much what I was thinking. Empty is empty, having a light gas to begin with does not make it even lighter when empty. Just what I am thinking but......... If you are having issues with buoyancy after losing say 2.5Kg of N2 based breathing gas from a stage. What is going to happen when you start breathing out some of the gas on your back? Before you start shopping for different cylinders, try this. When the cylinder start getting really light. Unclip it from your hip d-ring and clip it to your scooter d-ring. Then the bottle will float up on your side kinda where a full bottle would rest. Little trick I use for swimming through small caves where I don't want the empty stage bottles floating up and beating the hell out of the cave ceiling. Cheers!! Kevin |
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