Do mini/micro lift capacity 'wings' provide adequate 'insurance' against downdrafts ?

[ScubaSteve]

there is a difference between diving a bigger capacity wing and filling the wing with air needlessly, best to only fill the wing as much as needed for the situation.

Agreed but the fact is, if one is diving a large wing that will easily trap air (whether that be from taco'ing or because it is bungeed or simply because the diver does not know how to effectively vent the wing), then the diver will need weight to compensate. One does not need to put much air in an oversized wing in order to trap it so there is no "filling a wing with air needlessly" required. The "small" amount of air will provide the required buoyancy at depth but if it is "trapped", it makes for an exciting ascent, thus potentially leading the diver to simply throw on more lead.

Bhalah misread a previous post and made fun of the fact that the poster claimed you could drop weight by going to a smaller wing. I was simply pointing out that there can be truth to that.

It all boils down to selecting gear that is appropriate for the dive (that to me has a range and does not need anything silly like a different wing size for every dive).

[danvolker]

There are multiple threads on downwellings on the board over the past month or so. Based on the few postings of people who have actually been in them, the only thing that everyone seems to agree works is to swim horizontally until you are out of the current.

I believe that at least one person said filling their BCD and kicking didn't work for them. Several others noted that if you get out of a downwelling with a filled BCD you've just traded problems.

For downwellings on walls, swimming away from the wall seems to be the right thing to do.

If you were in a down current, and had fully inflated your bc, you would be doing this because you had been pulled deeper than 100 feet--and were concerned you might be headed for 200 and beyond....As you reach depths close to 200 feet, a fully inflated BC is easy to deal with, once you were out of the downcurrent....even though you would be ascending fast, at the 200 to 150 foot depth range, air in your lungs is NOT expanding so fast that this is any kind of issue for a thinking diver....This is nothing like the expansion that would occur from 60 feet to zero feet.
So in going from 200 or 150 to 100, the instant you are out of the down current, you can begin dumping, either partially or completely---a complete dump just takes a few seconds.....back in the early nineties, tech divers on air ( this was before helium was used ) the technique at the END of a 280 foot air dive ( with doubles) was to fully inflate the BC, and rocket to 100 feet..this was to remove an exponential decompression penalty which would otherwise occur from all the time going between 280 and 100 feet--in excess of the 25 minute bottom time.
In any event, this rocketing from 280 to 100 was actually fun, and it would be cancelled in an instant, by the complete dump--which the diver was PLANNING ON ....with finger on the trigger, and eye on the depth guage....

[cvchief]

given all of the people who came out of the woodwork to report how crazy the currents/downdrafts were that day, there's a reasonable chance a down current caused/contributed to a fatality. I think it's OK to try to learn from accidents, even if we don't have absolute proof of the cause. I'm giving you the benefit of a doubt by assuming you don't really mean a severe downdraft can't cause/aggravate a situation resulting in a fatality.

Well, if we aren't worried about causality, I have hear alot of reports of the taxis going to fast and creating problems lately. I guess by the same logic they might be responsible to? Do I believe a downdraft *could* create a problem for a diver? Yes. Did I hear ANYTHING about the loss being linked to a downdraft? No. The report stated she was last observed ascending, the exact opposite of getting pulled down. Clearly she had some issue that caused her to head to the surface. To believe a down-welling was involved, you have to disregard that fact and believe she got caught in a current that was no experience by the divers below her and then she was pulled down and around the group she just left and they remained down current free. Maybe we don't share the same definition of reasonable chance? I would say whatever caused her to start for the surface had a reasonable chance of being a large contributing factor to the incident. I would learn or have reinforced from the accident that ascending alone and being out of sight of the DM, your buddy and the boat is not a good idea.

[Mike]

I've read over and over again people saying if you fill your BCD in a down current that you are going to be in trouble after you get out of the current. Every BCD I've used 1) has a deflate button on the inflator hose, 2) expels air with a hard tug on the inflator hose, 3) has a dump cord at the bottom. Unless I'm knocked unconscious or my hands are paralyzed because of this down current I can't see any problem with inflating a BCD in a down current and not being able to quickly dump air when I want to.

Is a wing set up different then a BCD in regard to dumping air?

[nimoh]

I've read over and over again people saying if you fill your BCD in a down current that you are going to be in trouble after you get out of the current. Every BCD I've used 1) has a deflate button on the inflator hose, 2) expels air with a hard tug on the inflator hose, 3) has a dump cord at the bottom. Unless I'm knocked unconscious or my hands are paralyzed because of this down current I can't see any problem with inflating a BCD in a down current and not being able to quickly dump air when I want to.

Is a wing set up different then a BCD in regard to dumping air?

Can't say I can speak for all wings, but my Halcyon has a back dump, and a deflate button on the hose. Tugging on the hose does not dump air.

[cvchief]

I've read over and over again people saying if you fill your BCD in a down current that you are going to be in trouble after you get out of the current. Every BCD I've used 1) has a deflate button on the inflator hose, 2) expels air with a hard tug on the inflator hose, 3) has a dump cord at the bottom. Unless I'm knocked unconscious or my hands are paralyzed because of this down current I can't see any problem with inflating a BCD in a down current and not being able to quickly dump air when I want to.

Is a wing set up different then a BCD in regard to dumping air?

Well, maybe it is a caution for new divers? Freaked by being pulled down and slow to dump when they start up?

[Mike]

Well, maybe it is a caution for new divers? Freaked by being pulled down and slow to dump when they start up?

Boy, I think we could solve all these problems by just closing diving to any new divers.

[awap]

I don't have a BCD for insurance against down currents. My BCD floats my gear at the surface with or without me in it, and helps me achieve neutral buoyancy throughout the dive. Currents are best managed by avoiding them, seeking shielding from them, and/or swimming out of them.

If you are really interested in a device that will lift you out of currents, maybe you should start here: http://www.kval.com/news/business/In...139759913.html

[nimoh]

My preference would be to treat it as a rip current and try to swim out perpendicular, however if new divers are in an area prone to down currents, why not tether them to the surface?

[robint]

My preference would be to treat it as a rip current and try to swim out perpendicular, however if new divers are in an area prone to down currents, why not tether them to the surface?

Down currents are totally unpredictable - you cannot know when or where they will occur and how long they will last.
The problem with new divers and the UP-Down buttons on their BCs is that NEW divers tend to overuse them. Elevator to the surface is what they think it means, and that is so dangerous. I have even heard new divers refer to using that inflate button as how to reach the surface. In a downcurrent situation, a NEW diver is more likely to want to get to the surface as quickly as possible and not remember that they have to let air OUT as they go up, once released from the downcurrent. They panic, plain and simple, and their lack of experience can get them killed or severely injured by not letting air back out.

A diver with more experience will recognize that they are going too fast, but a NEW diver only wants to hit the surface. If you look at the statistics, the vast majority of diver deaths from over-expansion injuries are newbies.


robin