Shoulder pull dump needed in OW?

[LG Diver]

Hi All,

I’ll apologize in advance- I’m going to try to keep this brief but no guarantees. I’m a new diver (21 dives, just got my PADI rescue diver cert) and I’m researching my first equipment purchases. I plan to move on to do my MSD cert and eventually get into tech diving, so I want to buy gear that will carry over. I dive mostly in Monterey, CA. I’m currently diving in a rental 7mm farmer john, though I’m planning to get a drysuit when the budget permits, though this may be a while. I’ve settled on a bp/w setup but have a couple of questions about weights and shoulder pull dump as they specifically relate to diving wet in cold water in an open water environment. In the rescue diver course the instructor made a comment at one point that if a diver were to lose a weight belt and end up in an uncontrolled ascent, if not caught quickly the air in the BCD would be expanding so fast that you couldn’t possibly dump it from one vent fast enough- you might be able to if you used the shoulder dump and bottom dump simultaneously. This made me wonder if I need a shoulder dump if I’m diving with a large amount of ditchable weight in a thick wetsuit (if, for example, I were to accidentally lose a 20 lb weight belt), or in general to be able to react to an emergency situation more effectively (such as using the shoulder dump to quickly get away from a panicked diver on the surface as practiced in class). All of this leaves me with three possible scenarios in my mind:

1) wear all required weight as non-ditchable weight and go with an elbow only on the wing. In case of wing failure I’d be relying on an SMB for redundant buoyancy.
2) Wear enough ditchable weight to make the rig swimmable in the event of a wing failure. Install a shoulder dump on the wing as a precaution in the event of an accidental loss of ditchable weight.
3) Don’t sweat it- use ditchable weight and just go with the elbow and don’t worry so much about it.

I’m calling on the collective wisdom to tell me if this is something I should be worrying about or if I’ve overblown it in my head. I realize that this isn’t DIR compliant but that’s not my primary concern at the moment (though I have the “DIR fundamentals” and “Dress for Success” books and would like to comply as much as possible as I buy gear).

For reference, my calculations show that with a SS backplate and heave STA (like the Hammerhead cold water setup or Halcyon Eclipse with weighted STA) I’d still need ~20 pounds of weight with an Al 80 and 19 cu ft pony. If the weight belt were ditched at depth with full tanks this would leave me about 10 pounds negative at the bottom, so that’s about the amount of ditchable weight I’d need. (FYI- calculations attached, also show alternate tank configs being considered)

Thanks for the help,
John

 

[SDAnderson]

4) (a) Always wear enough ditchable weight to get yourself slightly positive from any depth that you might find yourself. Statistics indicate that, in the event of an emergency, you won't remember to use it but it's nice to have.
(b) Ditchable weight should come in small (five pound) increments and if you need more than ten pounds the chances are nearly 100% that you’re overweighted.
(c) Never plan on dropping your weightbelt from depth, lest you end up imitating a Polaris missile.
(d) Skip the shoulder pull-dump, they cause as more trouble than they solve and the inflator will deflate the wing, also.
(e) If you’re properly trimmed out (as well as weighted) you’ll be able to position yourself horizontal in the water (slowing your ascent) and use both the upper and lower dumps.
(f) Always carry an alternate lift device – a dry suit is great but a big enough smb will work just dandy.

I'm not a DIR diver, either, but Jablonski's books are a great resource and make an excellent starting point - before you decide to start overhauling his suggestions, consider whether or not you think someone with only 21 dives has enough experience and knowledge to know what they're talking about.

 

[LG Diver]

I agree that I'm not in a position to be telling anyone much of anything about diving. What I'm wondering about is the applicability of certain DIR configurations in situations that they were not originally intended for. This may be a gross misstatement, and I apologize if it is, but the impression I've gotten is that DIR's roots are in cave diving. Therefore, a wing vent configuration that may be applicable to diving in caves (little risk of a runaway ascent) in a drysuit in steel doubles (very little if no ditchable weight) may not be applicable to diving cold open water in a wetsuit with an Al 80. Again, looking to poll the collective wisdom, not suggest that my way is better. Regarding your other comments:

a) Do I need to be able to ditch enough to be positive, or just negative enough that I can still swim it up to a depth where my wetsuit regains some buoyancy?

b) currently carrying 34 pounds of lead in a rental BC with a 7mm farmer john and an Al 80 and 19 cu ft pony. I may be overweighted by ~5 lbs max, but there's no way I'd get neutral with 10 pounds in this environment, unless you're talking about making more weight non-ditchable (like a steel tank instead of Al).

c) doesn't this contradict a?

d) This is the heart of the question- yes, an inflator can let air out, but can it let air out faster than the air is expanding in an uncontrolled ascent? My instructor didn't seem to think so.

e) agreed

f) agree- and I carry a 35# Carter with a 150' spool, though I'm probably just as likely to kill myself as save myself with it until I get a little practice deploying it a depth.

Thanks again for the information.

 

[redacted]

Get a good wt belt with a good closure mechanism so that the chance of accidental loss is minimized by quality gear. Put it on before you donn the BP so the crouch strap will catch the belt if quality gear fails. I rigged a safety QD between my wt belt and my BC to hold the belt if a long drop from a large boat caused the buckle to fail (at the surface). The failure never occurred and I didn't bother moving that rig to my BP.

And if still in doubt, a pull dump should cost about $25. It can be converted to an elbow for about $10.

Go with the elbow. If you do lose bouyancy control at depth you will probably naturally assume a head down position as you try to swim it down. So you will need to dump from a rear dump valve anyway.

 

[JimC]

What problem are you trying to solve?
-Accidental belt loss.
See above post.

-Uncontrolled accent though neglect to controll boyancy.
Fix glareing skill issue by mastering boyancy.

b) currently carrying 34 pounds of lead in a rental BC with a 7mm farmer john and an Al 80 and 19 cu ft pony. I may be overweighted by ~5 lbs max, but there's no way I'd get neutral with 10 pounds in this environment, unless you're talking about making more weight non-ditchable (like a steel tank instead of Al).

34# is overweighted unless your a mutant. I hope your in salt water because it its fresh your massivly overweighted - even if you are a mutant.

 

[LG Diver]

What problem are you trying to solve?
-Accidental belt loss.
See above post.

Accidental weight loss- not sure yet if I'm going to carry the weight on a belt or an integrated system like the Halcyon ACB, or the DUI Weight and Trim II.

-Uncontrolled accent though neglect to controll boyancy.
Fix glareing skill issue by mastering boyancy.

I feel comfortable enough at this point that if the weight stays where it's supposed to I'm not going to get stupid enough that I can't correct the situation before getting out of control

34# is overweighted unless your a mutant. I hope your in salt water because it its fresh your massivly overweighted - even if you are a mutant.

Genetic status notwithstanding I may be a little bit overweighted (maybe 4-5 pounds), but judging by what I see others wearing (including instructors and DM's) in similar configs, I don't think I'm grossly overweighted. Yes, saltwater, 50 deg F, 2-piece 7mm wetsuit, 5mm gloves, hood, boots.

In any case, based on the responses it sounds like I'm overthinking this, and I should just go with the elbow and not sweat it. Thanks all.

 

[The Kraken]

JimC,
Depending upon one's physical size, 34# may not be overweighted.
In salt water, wearing a 7mm fj/j, hood, gloves diving a Zeagle "Tech" B/C on an AL80 tank, it takes me 22# to be neutral on my safety stop.

Now I'm 5'8" tall and weigh 175#. And I can assure you that I'm not overweighted at the end of the dive.

the K

 

[radinator]

I've been diving for 10 years (wetsuit and single tank), and never used a shoulder pull dump. I had one on my Balance BC, I just never developed the habit. In fact, for a class I was in I tried it recently for kicks and found that it had stuck together some time ago, I had to work to get it free that first time. I tried it once, but didn't see the point.

My normal rig (for the past year) is BP/W with no sholder dump. Perhaps the transition was made easier by the fact that I'd never used the sholder dump anyway. Perhaps not.

 

[terrasmak]

Whether or not you have air in your wing you will rocket to the surface if you lose you weight belt , especially with that much weight. shoulder dump willnot help , also you can only use one dump at a time

 

[mlloyd]

Use the weight belt, simple and effective. I would not recommend the Halcyon ACB solution.