Not enough buoyancy

[Doppler]

I find a few of your comments on this thread- hard to reconcile- with my experience. You seem to indicate that BC failure is very rare, because you have not had one. Have you run out of air at depth? If not, then does that mean it is "nothing to worry about" either?

Not quite what I wrote... Failure of a buoyancy cell is rare. In the vast majority of cases, the damage is done pre-dive and will be caught if pre-dive checks are carried out. If pre-dive checks are part of one's dive prep, emergency bladder ruptures, and catastrophic wing failures move into the extremely rare category.

And no I have not run out of air at depth... and I do not "worry" about it because it is avoidable... totally avoidable. We plan contingencies of course, and I mentioned contingencies for the unlikely event of an "emergency bladder rupture."

The plastic elbow used by most manufacturers to connect the corrugated hose to the buoyancy cell is the weakest link in almost any piece of dive kit... I've canvased several manufacturers to replace it with something more robust. We might as a community do the same. It could help to eliminate a piece of crap kit. It can break. Dump valves are dodgy too. HOWEVER, losing a dump valve is not an emergency. I have conducted a complete dive with the dump valve removed... I am sure you could too without ill effects.

Your other comment about ballistic ascents if lead is dropped are even more off target. Dropping 6-8 or 10 lb of lead is not going to send anyone shooting to the surface, unless they fail to control their BC and their body position in the water. You are WRONG that dropping lead will cause an uncontrolled ascent.

I respectfully disagree. I have been wrong about many things, but I have seen many, many divers get into runaway ascents after dropping a weightbelt loaded with ten pounds of lead... or less... especially at the midpoint of their dive... or later. Mostly because they did not understand the principles of correct weighting, buoyancy shift and failed to control their BC and their body position.

In all your experience, you have never dropped a weight belt and ascended without one to see what happens? I make my kids do it on their 2nd or third openwater training dive!

No I have not. And I would not make openwater students do so either. If I taught openwater students, I would suggest that ballast be distributed only partly on their weightbelt... perhaps just that amount of ballast that compensates for buoyancy shift (the mass of the gas consumed on the dive). Dropping that would allow them to swim around unaffected perhaps. But that is not what is normally taught.

Speaking of weighting... which we are... much more common than rupturing buoyancy cells... which I will say again, I have never experienced and nor have any of the folks with whom I regularly dive... much more common is overweighting.

 

[Dnaber]

Thanks everyone for the replies. This thread was just to start people thinking about "What if's" and safety. Everyone have a safe and fun dive season.

 

[NAM001]

I found that on my last wing leak that i just swam on my side with the leak on the bottom. could still use the inflator and get partial use of hte wing so as not to become too heavy and get up to the pont that the suit expanded again.

 

[cool_hardware52]

The plastic elbow used by most manufacturers to connect the corrugated hose to the buoyancy cell is the weakest link in almost any piece of dive kit... I've canvased several manufacturers to replace it with something more robust. We might as a community do the same. It could help to eliminate a piece of crap kit.

Steve, we have been producing our own elbows for years, along with the rest of the wing fitting. I hated the brittle ABS elbows and fittings the industry uses.

We mold all of the rigid fitting parts from Acetal (Think Delrin, Delrin is the Trade name for Dupont's Acetal resin) We happen to use Celanese, not Dupont, but that is a minor point.


Good grief man if you need a better elbow ping me.

Tobin

 

[dumpsterDiver]

Not quite what I wrote... Failure of a buoyancy cell is rare. In the vast majority of cases, the damage is done pre-dive and will be caught if pre-dive checks are carried out. If pre-dive checks are part of one's dive prep, emergency bladder ruptures, and catastrophic wing failures move into the extremely rare category.

And no I have not run out of air at depth... and I do not "worry" about it because it is avoidable... totally avoidable. We plan contingencies of course, and I mentioned contingencies for the unlikely event of an "emergency bladder rupture."

The plastic elbow used by most manufacturers to connect the corrugated hose to the buoyancy cell is the weakest link in almost any piece of dive kit... I've canvased several manufacturers to replace it with something more robust. We might as a community do the same. It could help to eliminate a piece of crap kit. It can break. Dump valves are dodgy too. HOWEVER, losing a dump valve is not an emergency. I have conducted a complete dive with the dump valve removed... I am sure you could too without ill effects.




I respectfully disagree. I have been wrong about many things, but I have seen many, many divers get into runaway ascents after dropping a weightbelt loaded with ten pounds of lead... or less... especially at the midpoint of their dive... or later. Mostly because they did not understand the principles of correct weighting, buoyancy shift and failed to control their BC and their body position.



No I have not. And I would not make openwater students do so either. If I taught openwater students, I would suggest that ballast be distributed only partly on their weightbelt... perhaps just that amount of ballast that compensates for buoyancy shift (the mass of the gas consumed on the dive). Dropping that would allow them to swim around unaffected perhaps. But that is not what is normally taught.

Speaking of weighting... which we are... much more common than rupturing buoyancy cells... which I will say again, I have never experienced and nor have any of the folks with whom I regularly dive... much more common is overweighting.

I agree that Wing/BC failures should be relatively easy to avoid with good pre-dive checks, but running out of air should be entirely avoidable too, yet people still run out of air and get in trouble. I think it is safer/better to dive in a manner that will allow you to survive if you run out of air OR have a total BC failure. In a perfect worls, neither would occur, but my world isn't perfect.

I used to work as a DM/Guide and I saw many BC failures with recreational divers and recreational students.

Once I was helping with some people doing an openwater dive to 300 ft (on air) and as I checked the world record holder's BC (out of habit) she somewhat objected to me messing with her gear before a big dive-- until I showed her that her OP relief valve cap was half unscrewed. When a BC will experience total failure due to something as simple as a cap that loosens up "by itself".. I think it is important to check the gear AND devise a good plan B. If the dump valve is at the top of the BC... you will have a problem if you want to add air to it.

As for ditching lead.. as far as I know none of the training agencies would condone an instructor directing a student to ditch lead and then practice a buoyant ascent. Too much liability to allow that. However that doesn't prevent me from doing it with my kids... I want them to know what will happen if they drop (or accidentally lose) a small weight belt at depth. The answer is: NOT MUCH..

This video, at t = 2 minutes shows my daughter dropping her belt and ascending with my help on her third time ever using scuba gear. Learning to flare out and flip over is an important skill in my book.


[video]https://youtu.be/NmeQmWZ_tzY?list=PLjC5PqdqiSg6JnRCYiwj8AIwwCxmy9mj w[/video]

 

[eelnoraa]

I have also seen one catastrophic BC/Wing failure close up. It was in a channel island live about. One of the divers pulled out his shoulder dump. He managed it nicely and ended the dive. So to me, it is not so rare. And I am prepared for it.

 

[Akimbo]

Steve, we have been producing our own elbows for years, along with the rest of the wing fitting. I hated the brittle ABS elbows and fittings the industry uses.

We mold all of the rigid fitting parts from Acetal (Think Delrin, Delrin is the Trade name for Dupont's Acetal resin) We happen to use Celanese, not Dupont, but that is a minor point.


Good grief man if you need a better elbow ping me.

Tobin

I imagine a lot of us would be interested in your improved BC elbow. Have you considered adding it to your Website for online orders?

 

[cool_hardware52]

I imagine a lot of us would be interested in your improved BC elbow. Have you considered adding it to your Website for online orders?

No, and I doubt we will. The CS burden is too high for ~$10 paart.

Is the "standard" size?

Will it fit my 20 year old Zundap dulap bc?

What exactly are the dimensions?

Can you provide me a cad drawing?, I prefer **.sat?

Can you send me pics of your elbow installed on my bc? 4-10 views should be enough

Can you guarantee me that it will fit all wings / bcs / known to have been produced by XX company since the beginning of time?

What are your return policies on these $10 parts after I try to force it to fit my XX BC?

Are they available in other colors, sizes, shapes, textures, lengths, bore diameters?

Will they fit the hose on my antique, imported, left handed, double hose, prototype safety sausages?

How much for a custom colored one?

You really need to start over. With my 12 dives I know your elbow is all wrong and should inside out and upside down with an extra doohicky.

Do you include a detailed installation manual and a 24 hour help line?

Etc. etc. etc.

Akimbo, If you need one ping me too.



Tobin

 

[gcarter]

The couple of catastrophic BC failures I've seen reported have been the same failure -- corrugated hose pulls off the connection to the air bladder, and all of those were BCs with pull dumps.

I didn't, in a quick search, find the buoyancy characteristics for a Faber HP117, but some of the Faber tanks can be 7 pounds or so negative when empty, or about 15 pounds negative for your tank when full. You will lose very little buoyancy from wetsuit compression with a 2 mil shortie, so I think 20 lbs is probably a liberal estimate of how negative you could be, at the beginning of your dive, should your hose pull off. I know I can swim up 10 lbs without too much stress; I've seen video of a friend swimming 25 pounds off the bottom of the pool. It's a chore, honestly, and maintaining your buoyancy at the surface would be very fatiguing. If I were you (and assuming these are the very negative Faber tanks) I'd consider something else for diving wet.

Most of the seriously negative steels are "medium" pressure 3180+ or 3000+ tanks.

Very few (maybe none) 3442 tanks are more than -1 to -2lbs. empty.

Tobin

Blue Steel Scuba - Cylinder Specs

The Faber 117, which I have, is essentially neutral empty according to this data.

 

[TONY CHANEY]

I agree that Wing/BC failures should be relatively easy to avoid with good pre-dive checks, but running out of air should be entirely avoidable too, yet people still run out of air and get in trouble. I think it is safer/better to dive in a manner that will allow you to survive if you run out of air OR have a total BC failure. In a perfect worls, neither would occur, but my world isn't perfect.

I used to work as a DM/Guide and I saw many BC failures with recreational divers and recreational students.

Once I was helping with some people doing an openwater dive to 300 ft (on air) and as I checked the world record holder's BC (out of habit) she somewhat objected to me messing with her gear before a big dive-- until I showed her that her OP relief valve cap was half unscrewed. When a BC will experience total failure due to something as simple as a cap that loosens up "by itself".. I think it is important to check the gear AND devise a good plan B. If the dump valve is at the top of the BC... you will have a problem if you want to add air to it.

As for ditching lead.. as far as I know none of the training agencies would condone an instructor directing a student to ditch lead and then practice a buoyant ascent. Too much liability to allow that. However that doesn't prevent me from doing it with my kids... I want them to know what will happen if they drop (or accidentally lose) a small weight belt at depth. The answer is: NOT MUCH..

This video, at t = 2 minutes shows my daughter dropping her belt and ascending with my help on her third time ever using scuba gear. Learning to flare out and flip over is an important skill in my book.


[video]https://youtu.be/NmeQmWZ_tzY?list=PLjC5PqdqiSg6JnRCYiwj8AIwwCxmy9mj w[/video]

I too have done hundreds of DM / safety diver dives and have only seen one BC failure. A new DR out of the box and it leaked in Cow. We got out OK without complications. I have well over 800 dives without a single failure.

300 feet on air...I will not even address that one.