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gee
04-10-2009, 17:13
Last week I used steel tanks for the first time and never got my weight correct. I started out with 6 pounds and ended up with 4 but was still overweight (had to kick to stay level at the safety stop). If I dive with one again Iíll try 2 pounds or maybe none. So is this a common occurrence and how does one address ditching weight?

Rainer
04-10-2009, 17:16
Last week I used steel tanks for the first time and never got my weight correct. I started out with 6 pounds and ended up with 4 but was still overweight (had to kick to stay level at the safety stop). If I dive with one again Iíll try 2 pounds or maybe none. So is this a common occurrence and how does one address ditching weight?

What are you wearing for exposure protection? How positively buoyant is it? What kind of BC?

Gombessa
04-10-2009, 17:21
Last week I used steel tanks for the first time and never got my weight correct. I started out with 6 pounds and ended up with 4 but was still overweight (had to kick to stay level at the safety stop). If I dive with one again Iíll try 2 pounds or maybe none. So is this a common occurrence and how does one address ditching weight?

What's your weighting with AL tanks? If you are weighted correctly while using an AL80, you should require roughly 5lb less lead with a steel LP80.

Also, what kind of exposure protection are you wearing, and what other weights (or equipment configuration) are you using?

If you're neutral at your safety stop with no ditchable weight, that means you're positive on the surface at the end of your dive, and roughly 5-6lb negative at the beginning of the dive while on the surface. If you're wearing a wetsuit that provides ~10lb lift at the surface, you might be up to 15lb negative at the beginning of your dive at depth, which would be heavier than recommended.

clararhb
04-10-2009, 18:23
Most tank manufaturers have a chart of bouyancy for their tanks. If you know your weight for another tank using the same gear then use the chart to adjust. I was told that neoprene requires about 2 pounds per MM for a size large. This ought to get you in the ball park.
At least you were too heavy then not heavy enough.

mitsuguy
04-10-2009, 18:52
you may not need any weight whatsoever... if you are neutral with no weight, then I don't see anything wrong with it, so long as you are not overweighted without weight...

I typically only need 2-4 lbs when diving a 3 mil full suit and a steel HP80 tank in freshwater, I could even get away with no weight, but I was just a hair positive at the safety stop which makes it uncomfortable to end a dive...

gee
04-10-2009, 19:33
5 mm & beanie
SP Classic
A day earlier I used an AL tank & 12 pounds and was neutral at the SS.



Last week I used steel tanks for the first time and never got my weight correct. I started out with 6 pounds and up with 4 but was still overweight (had to kick to stay level at the safety stop). If I dive with one again Iíll try 2 pounds or maybe none. So is this a common occurrence and how does one address ditching weight?

What are you wearing for exposure protection? How positively buoyant is it? What kind of BC?

CompuDude
04-10-2009, 19:52
5 mm & beanie
SP Classic
A day earlier I used an AL tank & 12 pounds and was neutral at the SS.



Last week I used steel tanks for the first time and never got my weight correct. I started out with 6 pounds and up with 4 but was still overweight (had to kick to stay level at the safety stop). If I dive with one again I’ll try 2 pounds or maybe none. So is this a common occurrence and how does one address ditching weight?

What are you wearing for exposure protection? How positively buoyant is it? What kind of BC?

If nothing else changed, going from an Al.80 to an HP steel tank, you're likely to be able to drop about 6#, +/- 1 depending on the exact tank model in question. Bear in mind that the buoyancy at the safety stop should be neutral with a nearly empty tank. If you still have lots of gas in your tank, you'll be a few pounds heavier. An 80cf tank holds about 6# of gas. If you have more than half a tank left, you're looking at more than 3# heavy, compared to empty or nearly so. The dangerous bit is nearly OOA and underweighted, which is why you need to weight yourself for that worst case scenario.

RoyN
04-10-2009, 20:55
Just curious, what steel tank are you using?

rongoodman
04-10-2009, 20:58
Rather than kicking to hold your position, why didn't you just add some air to your wing/BC?

gee
04-10-2009, 23:26
It was from a dive op. It was a 120 cf.


Just curious, what steel tank are you using?

gee
04-10-2009, 23:49
On a ss I would prefer to have more precise control over depth. I'm not sure I would have the same level of control by adding (then maybe venting) air. I should clarify that the kicking I mentioned was an occasional kick to maintain depth not a constant kick.


Rather than kicking to hold your position, why didn't you just add some air to your wing/BC?

navyhmc
04-11-2009, 00:22
Also, how much air did you still have in your tank? A 120 is only 2 lbs negative empty or 3lbs negative at 500 psi. I would also work to get your precision bouyancy to where you can remain relatively level without kicking at all. a little toot of air into your bc can help with that.

RoyN
04-11-2009, 15:20
Maybe try a smaller tank? A HP120 is like a giant missile tank.

gee
04-11-2009, 16:48
navyhmc,

I think you have given me some insight into the cause of overweighting at the end of the dive. I started the ss with 750 psi. Thanks


Also, how much air did you still have in your tank? A 120 is only 2 lbs negative empty or 3lbs negative at 500 psi. I would also work to get your precision bouyancy to where you can remain relatively level without kicking at all. a little toot of air into your bc can help with that.

gee
04-11-2009, 16:56
RoyN

I agree. For the first several minutes I felt like the 120 was shoving me around a little. This was the first time I have used a steel tank. The dm cautioned me that diving with one is different than with an AL80. I still have some adjusting to do!

Maybe try a smaller tank? A HP120 is like a giant missile tank.

RoyN
04-11-2009, 18:20
How about a steel 100 or 80 would be a good size.

clararhb
04-12-2009, 17:18
Worthingotn makes a LP77. It basically replaces an AL80 but it never goes positive. If I am thinking right it is 1#-.

cummings66
04-13-2009, 13:27
I dive double HP120's so I understand the weight swing, but it's nothing that can't be compensated for by adding air to the BC. If you don't change your depth you would never need to compensate by letting air out, and even if you do it's the same as an AL80. You just do it by feel, the same way you do the others.

I think you were psyched out by the DM at the start who told you that stuff. It's no different than any other cylinder out there except it's heavier. Once you account for the ~6lbs of change you're in the same boat. Now if you're a short guy I can see the trim being a major concern, but if you're 6' or have a long torso like me it's not a problem.

Assuming the cylinder fits you then the very first dive I made I'd drop 6 lbs of weight and go for it. Now of course a 120 is more negative at the start of a dive than the AL80 would be, ie 77 cf of air vs 120 cf of air, so you'd have more air in the BC at the start of a dive. You might also be heavier at the end of a dive if you still carried the same psi of air left because you'd have more air which means more weight. The solution is the same, add more air to the BC.

I think the DM did you a disservice.

Tully Mars
04-13-2009, 20:55
I think the DM did you a disservice.

I think so too.

I dive with extra weight all the time. Usually two 3lbs'ers. Turns out people come down here and think since they don't have thick wet suit they don't need any weight. If people have trouble descending it's nice to have a little weight to pass off to them.


Use your BC it'll work out fine.

gee
04-14-2009, 10:39
DM was helpful in all respects. I think this thread has taken a path I didn't expect. If I were to dive with a 120 cf steel tank again I may have to dive without weights to be properly weighted. My original intent was to try to discover how others handle diving without added weight to ditch in an emergency situation.


I dive double HP120's so I understand the weight swing, but it's nothing that can't be compensated for by adding air to the BC. If you don't change your depth you would never need to compensate by letting air out, and even if you do it's the same as an AL80. You just do it by feel, the same way you do the others.

I think you were psyched out by the DM at the start who told you that stuff. It's no different than any other cylinder out there except it's heavier. Once you account for the ~6lbs of change you're in the same boat. Now if you're a short guy I can see the trim being a major concern, but if you're 6' or have a long torso like me it's not a problem.

Assuming the cylinder fits you then the very first dive I made I'd drop 6 lbs of weight and go for it. Now of course a 120 is more negative at the start of a dive than the AL80 would be, ie 77 cf of air vs 120 cf of air, so you'd have more air in the BC at the start of a dive. You might also be heavier at the end of a dive if you still carried the same psi of air left because you'd have more air which means more weight.he solution is the same, add more air to the BC.

I think the DM did you a disservice.

Rainer
04-14-2009, 10:43
DM was helpful in all respects. I think this thread has taken a path I didn't expect. If I were to dive with a 120 cf steel tank again I may have to dive without weights to be properly weighted. My original intent was to try to discover how others handle diving without added weight to ditch in an emergency situation.


We either find ways not to be over-weighted, live with being over-weighted, or don't dive.

Personally, I try to determine my weighting needs before getting in the water. That's just me, though.

UCFKnightDiver
04-14-2009, 11:01
live with the fact of being over weighted and do notthing, kick your rig up (I can do this with one fin and double LP85's), shoot a lift bag and climb up, ride your buddy up, get a drysuit, get a double bladder wing...

theres lots of solutions to it. In my opinion dropping weights should be the absolute last ditch effort, dropping weights will very often result in an uncontrolled ascent which is not a great thing.

cummings66
04-14-2009, 12:21
DM was helpful in all respects. I think this thread has taken a path I didn't expect. If I were to dive with a 120 cf steel tank again I may have to dive without weights to be properly weighted. My original intent was to try to discover how others handle diving without added weight to ditch in an emergency situation.


I think it's a non issue when it comes to ditching weights, you don't really need that ability if you're properly weighted in the first place.

However, what I meant by the DM comment was it sounded to me like he psyched you out by telling you how different the cylinder would be. It's not different, that's the point. Diving it is the same as diving any other cylinder. You have the amount of air which adds more weight and gives you a weight swing, that's it. So what if you have a few more lbs weight swing? Easily handled. You have the fact that at the end of a dive it's probably -2 lbs or so vs the +4 or so for an AL80, again no big deal because if you weight yourself correctly you still end up neutral.

So the only issues with a 120 are it's longer, and the weight swing is greater than an AL80 which is well within the capability of any BC you'd be using to handle. A short person might find their trim being wrong now, but that's the only possible issue.

The DM did not point out that, instead the DM made it appear like this would be some monster out to get you, it's not. The DM IMO did you a disservice by not pointing out the obvious. I'm sure he didn't want to tell a diver with 1000 dives that it's no big deal and candy coated it, and that is what I think the disservice was. He should have been upfront and told you it's no big deal for a diver of your experience. Then you would have just removed a few lbs of lead and not thought a second thing about it and had fun without kicking during the SS. Instead you were worrying about ditching lead, being properly weighted, etc. That's why he was not helpful, IMO.

A 120 is not a big deal, it's not any harder than any other cylinder out there to dive with and the DM indicated otherwise, that's where I think it went south at.

As to dealing with having no ditchable weight, if you're balanced don't sweat it. We're all somewhat negative at the start of a dive. Air weighs .08 lbs per cubic foot, that means your HP120 is 3.4 lbs more negative than you'd be on the AL80 because it has that much extra air. So the DM who knew that made it seem difficult, he made a big deal out of 3 lbs extra air. He should have just pointed out correctly IMO that it's no big deal. It's only 3 lbs more negative than your AL80 is at the start of a dive and that amount is not a problem.

This is what the DM didn't say.

So here's the deal, -1.3 lbs empty for a PST 120 and +4.4 lbs empty for a Luxfer 80. The difference is 5.7 lbs so you can remove 6 lbs from your belt and you are now identical at the end of a dive compared to the Luxfer 80. At the start of a dive you are 3.4 lbs heavier than you are with the Luxfer 80 because you have abt 43 cf more air but your BC will handle an extra 3 lbs at any point.

Reference the specs here;
http://www.huronscuba.com/equipment/scubaCylinderSpecification.html

UCFKnightDiver
04-14-2009, 13:09
not to be disrespectful or anything but I just noticed on your profile you say you have 500-1000 dives. At that many dives you dont know the solution/solutions to this problem?

clararhb
04-14-2009, 13:44
One bad thing about a forum. You can be what you want to be and nobody knows the difference.

cummings66
04-14-2009, 16:53
Be nice, many divers just dive and have fun without thinking about the mechanics of it. I'm sure Gee is one of those divers who goes out and has a blast diving here there and elsewhere. You can amass a lot of dives and not even know how a cylinder works or why it gets lighter at the end of a dive, or you might assume it's a huge difference in weight when in reality it's hardly any difference.

A dive number does not indicate knowledge or skills, only that you've done those dives. You can do a thousand dives to 15 feet repairing pools and have absolutely no skills at all because all you ever did was look for a leak, and that's a skill you'd have nailed. But take you to 100 feet in a dark quarry and it's a whole nother game.

The only assumption I make about a diver is that they enjoy doing it and so I'm sure Gee has had a blast doing his dives. I envy the fun he's had.

Now if Gee said he's a DM I'd question him for the obvious lack of knowledge that cert should bring with it, but he didn't say he's a DM and so I think Gee is a typical recreational diver having fun. As far as I know he's OW certified only, and I know that level doesn't even cover the details mentioned in this thread. AOW doesn't even cover it, I don't recall a course that told me the weight of air per CF. OW was just return to the surface with 500psi, get neutral with that amount of air. The cylinder used is almost always an AL80. Gear beyond that often gets tossed into the technical arena and not covered. I won't nail him for having problems because it's most likely he was never told, most of us are not. He's out there having fun and I wish I had as much as he has had. Odd's are he's a pretty fair diver to boot, you can't get that many dives and not have some good skills. It doesn't mean he'd know why something didn't work and he's shown curiosity about the "why" which I commend.

People often look at steel cylinders with a bit of mysticism and somehow think they're special. They not, but they are different in some subtle ways, and in other respects they are no different. They hold air, have a weight swing, rust easier if the coating is damaged, and typically are near neutral or slight negative when empty compared to many AL cylinders. There is nothing magic about them, just another cylinder and that's where I think some OW courses go wrong. They show you various gear types and gloss over them, or make it seem like there's something special about it. Take drysuits for example.

Tully Mars
04-14-2009, 19:08
Be nice, many divers just dive and have fun without thinking about the mechanics of it. I'm sure Gee is one of those divers who goes out and has a blast diving here there and elsewhere. You can amass a lot of dives and not even know how a cylinder works or why it gets lighter at the end of a dive, or you might assume it's a huge difference in weight when in reality it's hardly any difference.

Yep, I dove for years in the same 45-55 ft of water in and around Tillamook Bay Or. Filling my own tanks at the fire dept. I volunteered at. Even after 200-300 dives If you'd have asked me about doubles or any mix other then compressed air you'd have got a blank stare in response.

clararhb
04-14-2009, 21:10
People often look at steel cylinders with a bit of mysticism and somehow think they're special. They not, but they are different in some subtle ways, and in other respects they are no different. They hold air, have a weight swing, rust easier if the coating is damaged, and typically are near neutral or slight negative when empty compared to many AL cylinders. There is nothing magic about them, just another cylinder and that's where I think some OW courses go wrong.

I remember when I asked about steels in my OW course. Man you would have thought that I asked about Satan himself or they were voodoo. It was not a pretty sight. So needless to say I won't be buying a steel tank from my LDS.
Love the story that buddy told me. He went into the LDS to get a VIP done and they OWNER and INSTRUCTOR told him that he could do a VIP on a steel cylinder because he didn't have the proper o-ring. He proceeded to tell him about the difference in the neck.

UCFKnightDiver
04-14-2009, 21:48
well there are some of the older steel tanks that have a different thread size than the standard 3/4in thread

gee
04-14-2009, 22:52
Agreed it is the absolute last ditch effort. But, there are scenerios where you need that as an option. And thanks for those creative suggestions.

And as far as my diving experience goes, cummings explains it as well as is needed. I looked at your profile and realized, not to be disrespectful either as I just find it amusing, that I have gear older than you!:smiley36:


live with the fact of being over weighted and do notthing, kick your rig up (I can do this with one fin and double LP85's), shoot a lift bag and climb up, ride your buddy up, get a drysuit, get a double bladder wing...

theres lots of solutions to it. In my opinion dropping weights should be the absolute last ditch effort, dropping weights will very often result in an uncontrolled ascent which is not a great thing.

UCFKnightDiver
04-14-2009, 23:06
Im glad for you I have some gear thats a bit older than me too :smiley2: Im not sure where age factors into this, when I know some of the solutions to your questions.....

gee
04-14-2009, 23:15
You found me out! Iíve been very fortunate to dive recreationally in a lot of places, mostly in the Caribbean and the South Pacific but Iíve never experienced a dark quarry at 100 feet! I am quite content to drop down on a reef below the boat and just take it all in!

If tank info was in my OW or AOW class Iíve forgotten all of it. But then, that was in 1981!

Thanks for your very rational and reasonable inputs


Be nice, many divers just dive and have fun without thinking about the mechanics of it. I'm sure Gee is one of those divers who goes out and has a blast diving here there and elsewhere. You can amass a lot of dives and not even know how a cylinder works or why it gets lighter at the end of a dive, or you might assume it's a huge difference in weight when in reality it's hardly any difference.

A dive number does not indicate knowledge or skills, only that you've done those dives. You can do a thousand dives to 15 feet repairing pools and have absolutely no skills at all because all you ever did was look for a leak, and that's a skill you'd have nailed. But take you to 100 feet in a dark quarry and it's a whole nother game.

The only assumption I make about a diver is that they enjoy doing it and so I'm sure Gee has had a blast doing his dives. I envy the fun he's had.

Now if Gee said he's a DM I'd question him for the obvious lack of knowledge that cert should bring with it, but he didn't say he's a DM and so I think Gee is a typical recreational diver having fun. As far as I know he's OW certified only, and I know that level doesn't even cover the details mentioned in this thread. AOW doesn't even cover it, I don't recall a course that told me the weight of air per CF. OW was just return to the surface with 500psi, get neutral with that amount of air. The cylinder used is almost always an AL80. Gear beyond that often gets tossed into the technical arena and not covered. I won't nail him for having problems because it's most likely he was never told, most of us are not. He's out there having fun and I wish I had as much as he has had. Odd's are he's a pretty fair diver to boot, you can't get that many dives and not have some good skills. It doesn't mean he'd know why something didn't work and he's shown curiosity about the "why" which I commend.

People often look at steel cylinders with a bit of mysticism and somehow think they're special. They not, but they are different in some subtle ways, and in other respects they are no different. They hold air, have a weight swing, rust easier if the coating is damaged, and typically are near neutral or slight negative when empty compared to many AL cylinders. There is nothing magic about them, just another cylinder and that's where I think some OW courses go wrong. They show you various gear types and gloss over them, or make it seem like there's something special about it. Take drysuits for example.

cummings66
04-15-2009, 07:14
You found me out! Iíve been very fortunate to dive recreationally in a lot of places, mostly in the Caribbean and the South Pacific

I figured something like that, and as I said I envy that. All I dive are dark and cold places in the midwest. But it's still fun and I like you enjoy the dives I do get to participate in.

As they say, keep on trucking.

Tully Mars
04-15-2009, 10:42
This thread's taken an odd turn. Glad to see it back on track.

I think it's kind of strange logic to think I've been diving for "X" years, I know A,B,C and D. Member "Y's' been diving "X+" years why doesn't he know B&D? Everyone experience in life is different. That's the great thing about forums like these- you can get info from people who do know the answer to "B&D" or even "A&C" if needed.

gee
05-01-2009, 22:10
Agreed. The diversity of the experiences that the members freely share through this forum provide me with a wealth of information that I don't think I could get in my lifetime. For that, I am truly grateful.
This thread's taken an odd turn. Glad to see it back on track.

I think it's kind of strange logic to think I've been diving for "X" years, I know A,B,C and D. Member "Y's' been diving "X+" years why doesn't he know B&D? Everyone experience in life is different. That's the great thing about forums like these- you can get info from people who do know the answer to "B&D" or even "A&C" if needed.