No weights with steel tank unsafe?

[FredT]

Thalassamania has mentioned that type of foam before, I think.

So, Fred, are you thinking of making these?

I'll take on any project that meets 3 requirements.
1. I find it an interesting challenge.

2. I believe it can be manufactured in a way to make it cost effective for the diver(s) involved.

3. I can't come up with a better solution to the problem using "off the shelf" parts for less $s and equal reliability.

One problem with being an Ocean Engineer is the market is small enough nobody makes parts just for us. ( It may get even smaller if Obama kills the oil industry as he's threatening, NMF is already killing the fisheries industry by regulation based on junk science, and marine hard minerals recovery was already killed by both Carter and Clinton.) Because of the small market we learn quickly to "make do or make new." Make new is more fun for the engineer, make do is often much more cost effective even if it means designing and building a new housing rated for external pressure as well as internal.

This problem makes the grade on 1 and 2. The jury is still out on 3.

 

[halocline]

Hi guys.

I'm considering purchasing a tank rather than continuously renting partially because I just like to own all my own gear and because the Worthington 130's are really attractive to me being almost the same size as the AL80's yet a lot more air. However, I have a concern about the buoyancy.

I am one of those really negatively buoyant people. Even in my 3mm Pinnacle wetsuit 4lbs is more weight than I need (I'm slightly negatively buoyant without them). Currently in fresh water wearing a Scubapro hybrid shorts/longsleeeved shirt (1mm neoprene front/back) I dive with no weights at all as I honestly don't need it. Even with an AL80 <500psi, I am still negative.

I think the obvious answer here is to dive with AL80s in the cases that you do not need the additional gas, and consider just doubling AL80s or LP72s for the times you need more gas. It's not just a matter of being able to swim your rig to the surface, it's the fact that you don't want to be overweighted in the first place. Diving is more enjoyable when you're properly weighted. It's also more enjoyable when you're only carrying an appropriate tank for the dive you're doing. Needing a 130 for a single dive for me would imply something beyond recreational limits, unless you're an airhog. If you're thinking you'll get two dives on one tank, maybe you're right but then you could get 2 AL80s for the price of one HP130 and you'd have a more manageable tank on your back. There's a big difference between a 7.25" and 8" tank in terms of feel, at least there is to me.

You can also get larger AL tanks. I've used an AL100 and I did not like it, but it might be perfect for you.

 

[nwbobber]

I don't know about all this talk about ditching weight at depth. I would NEVER want to do that. It seems much more sensible to carry alternate bouyancy, as in a smb or lift bag so you can control your ascent. Dumping 20 lbs at 80 ft sounds like a wild ride, probably followed by a chamber ride, or worse.

 

[Indian Valley Scuba]

Hmmmm...keep in mind, drowning aside, that while there are about a thousand things you can do wrong while diving, there are three primary mistakes that can hurt or kill you.

1. Holding your breath
2. Ascending too quickly
3. Staying down too long

So with that in mind, dropping any significant amount of weight at any depth, and most critically in the shallowest depths, may certainly lead to fatal error #2, and while you are screaming to the surface and struggling to stop that, you are most likely committing error #1 also.

The bottom line - never drop your weights at depth. Get properly weighted and stay that way! If you feel a need to seed the sea with lead, only do it from the surface, never while under it.

And in case you were wondering, I like to believe the other 997 errors you can make while diving merely serve to provide comic relief to the others around you!

 

[rstofer]

It's very nice to talk about being properly weighted but the devil is in the details. If your wetsuit loses 20# of buoyancy at depth, by definition, you are 20# overweighted at that depth. There's nothing you can do about it, you are overweighted. Compound this with a tank that swings 8# and, by definition, you are 8# overweighted at the start of the dive. Again, nothing you can do about it.

Compensating for this weight swing is the function of the buoyancy compensator. As long as it works, all is well. The devil is in figuring out what to do when it doesn't.

Ditching weight to get to a point where you can swim off the bottom doesn't have to be an all or nothing operation. It is possible to open the weight pouches on your harness and take out a couple of shot bags. This probably doesn't work for integrated weight systems. It probably doesn't work all that well for harnesses either; but it's a thought.

The other devil is in how to rescue someone else who is similarly overweighted at the start of the dive. I don't think an SMB or lift bag is going to help. How do you manipulate your buoyancy, the victim's buoyancy (assume their bladder is hosed), hold the reg in their mouth, maintain control of their body and still mess with a bag?

I don't presume to have the answers. I have thought about the problem and come to the realization that sometimes bad things happen. But not being able to get positive at the surface without ditching the rig does not improve the odds.

Richard

 

[Jrock1062]

The other devil is in how to rescue someone else who is similarly overweighted at the start of the dive. I don't think an SMB or lift bag is going to help. How do you manipulate your buoyancy, the victim's buoyancy (assume their bladder is hosed), hold the reg in their mouth, maintain control of their body and still mess with a bag?

I don't presume to have the answers. I have thought about the problem and come to the realization that sometimes bad things happen. But not being able to get positive at the surface without ditching the rig does not improve the odds.

Richard

You’re making the assumption that both you and your dive buddy will have wing failure during the same dive. If your buddy’s wing fails use yours and if yours fails use his. An SMB will help you lift yourself in the event of your wing failure. It will not help both of you although if there are two wing failures and your buddy is unconscious things would be dicey at best

 

[DeepSeaExplorer]

I didn't read all the posts, so maybe this has been mentioned. Separate from a wing failure, I simply would not want to be swimming around with a bunch of air in the wing trying to stay neutral with an unnecessarily heavy tank. That's a lot of drag for no reason. I have no issue with not having ditchable weight because I don't use any on any of my rigs; however, with the exception of my cave rig, I'm close to neutral. I think the AL80 is the way to go for you with your buoyancy characteristics, especially since it doesn't appear that you need the extra volume of steel tanks. The tank should fit the type of diving you do and AL80 seems to be perfect fit in this case.

 

[syntaxerrorsix]

It's very nice to talk about being properly weighted but the devil is in the details. If your wetsuit loses 20# of buoyancy at depth, by definition, you are 20# overweighted at that depth. There's nothing you can do about it, you are overweighted. Compound this with a tank that swings 8# and, by definition, you are 8# overweighted at the start of the dive. Again, nothing you can do about it.

Compensating for this weight swing is the function of the buoyancy compensator. As long as it works, all is well. The devil is in figuring out what to do when it doesn't.

Ditching weight to get to a point where you can swim off the bottom doesn't have to be an all or nothing operation. It is possible to open the weight pouches on your harness and take out a couple of shot bags. This probably doesn't work for integrated weight systems. It probably doesn't work all that well for harnesses either; but it's a thought.

The other devil is in how to rescue someone else who is similarly overweighted at the start of the dive. I don't think an SMB or lift bag is going to help. How do you manipulate your buoyancy, the victim's buoyancy (assume their bladder is hosed), hold the reg in their mouth, maintain control of their body and still mess with a bag?

I don't presume to have the answers. I have thought about the problem and come to the realization that sometimes bad things happen. But not being able to get positive at the surface without ditching the rig does not improve the odds.

Richard

I don't believe I have ever met a wetsuit that loses 20# buoyancy at depth.

 

[heavyjeffd]

I didn't read all the posts, so maybe this has been mentioned. Separate from a wing failure, I simply would not want to be swimming around with a bunch of air in the wing trying to stay neutral with an unnecessarily heavy tank. That's a lot of drag for no reason. I have no issue with not having ditchable weight because I don't use any on any of my rigs; however, with the exception of my cave rig, I'm close to neutral. I think the AL80 is the way to go for you with your buoyancy characteristics, especially since it doesn't appear that you need the extra volume of steel tanks. The tank should fit the type of diving you do and AL80 seems to be perfect fit in this case.

Thank you, excellent post. I greatly appreciate the feedback.

 

[FredT]

Actually if he is negative anyway, ditching the rig is not much help. I dove "naturally negative" for a couple decades. IF you can keep moving that is not too much of a problem because you can plane up. If however you have to stop for any reason it gets to be a real hassle. My personal solution involved getting married, eating regular and adding some body fat to get to neutral (I'm more than a bit over neutral now. )

The key to this whole thing is how much positive buoyancy adder does he have to have to float just HIM. Once that is established a correct answer, again for HIM, can be developed. That answer may be adaptable for other warm water gym addicts, or not.

As an example if it takes 6 pounds (3/4gallon of air or a gallon and a half of syntactic) to just float heavyjeffd adding a bit to deal with the tank and other rigging is not an issue. If he's only a pint of air negative that wouldn't be an optimal or cost effective solution. Heavyjeffd has reported a relatively unusual situation. Even with the necessary exposure suit for his area he is negative at the surface.

Adding lead or flotation just to add it is not a reasonable thing to do, and having dumpable weights when diving with a relative incompressible exposure suit in warm water is not anywhere near the necessity it is when diving a 7 mil farmer john in cold water. A small lift bag hooked to the crotch strap or shoulder d-rings will hold a diver at the surface just fine, it's getting him there that is the problem. I know of at least one drowned diver that died because she simply couldn't get there.

OTOH one of the best divers I've ever met never routinely used a BC. He and his rig are neutral in warm water with no rubber, so no lead or flotation is necessary FOR HIM.