Dropping a weight pocket on a line—dumb idea?

[Eric Sedletzky]

@Eric Sedletzky I lived in Marin for many years, got certified in Novato. Do you go Ab diving? I read it was closed this year. How do the kelp forests look to you?

Did you get certified at the Pinnacles? owned by Joe Ford.
He closed that shop down. John his long time employee and right hand man left to buy Marin Diving Center.
I got certified through the Pinnacles in Novato in 1998. I sat in that classroom and used that same pool, small world.

I was a huge ab diver for years. The last few years I tapered off though. I never was able to get a 10”, biggest I ever found was a 9-7/8”.
Ab diving is closed this year, and we figure it will be closed for quite sometime if not indefinitely. The kelp is way down, almost non existent. I do fun dives with Seals Water Sports in Santa Rosa now. It also used to be a Pinnacles owned by Joe. Joe sold it to Scott and Scott renamed it Seal’s. We do abalone feeding and urchin harvest and relocation dives. We’re trying to do what we can to save what abs are left and to give the kelp a fighting chance against voracious grazing urchins.

 

[Diving Dubai]

When you think about BCD failure, it's best to analyse what failure possibilities there are:

Off the top of my head there would be a tear or an inflator run away or the worst (IMO) would be the inflator hose detaching.

An inflator runaway is no biggy - it's taught during OW and its happened to me.

A tear, again no biggy, I tore my wing on the first day of a 3 dive trip, I could still dive it, the tear was only an annoyance at the surface when I couldn't fully inflate - Even with a Steel HP120 I had enough buoyancy.

So with these failures you can continue the dive or surface in a controlled manner. With the inflator hose becoming detached even at depth unless you're carrying a massive amount of weight you should be able to swim up and let suit expansion assist

SMB use ... not convinced. the OPV is at the bottom, so unless its full or you invert the smb during the ascent to vent.. it's not going to end well.

A lift bag would be a better option, but how many people always carry one - or indeed can bring a load to the surface with one without getting a runaway?

Personally I'd use my buddy to assist rather than dropping weights or only drop weights as a final last measure.

Just my 2bar

 

[Storker]

I've experienced two BCD "failures". Both of them were rather moderate, it was just the shoulder dump that leaked. And we were in drysuits, so we had redundant buoyancy.

On one occasion (my BCD, gently sloping bottom close to shore so worst case I'd have to walk up out of the water, hard bottom at 18-20m), I was quite comfortable to continue the dive and fix the issue during the SI. On the other occasion (buddy's BCD, wall dive, boat entry, no hard bottom above 80-100m) I thumbed the dive as soon as we discovered the issue.

It's all about the specific situation.

 

[dmaziuk]

SMB use ... not convinced. the OPV is at the bottom, so unless its full or you invert the smb during the ascent to vent.. it's not going to end well.

Uhmm... if it's not full, then there's no overpressure, is there?

 

[northernone]

SMB use ... not convinced. the OPV is at the bottom, so unless its full or you invert the smb during the ascent to vent.. it's not going to end well.

When I drill (play) for this contingency I knot the smb into a slender 10l bag (depending on the lift needed) which is easy to vent on ascent and works nicely without the risk of becoming runaway with excessive lift potential. Holding it one hand on the tail and the other on the vent it works comfortably as supplementary lift with a couple practice dives while venting regularly on ascent.

I believe most people who suggest an smb mean to shoot the smb and use the ascent line to drag themselves to the surface, not actually riding the smb up like a trim pillow.

 

[Storker]

Uhmm... if it's not full, then there's no overpressure, is there?

I don't believe that the issue is overpressure. Ever tried to use a bag for buoyancy? Even if it has a dump valve at the top, it's pretty darned difficult to avoid that it just corks. I use a large, old dSMB to provide buoyancy to my catch bag when I have a decent amount of scallops, but it's a major PITA to try to do anything except just sending it to the surface by itself.

 

[JamesBon92007]

Let's talk about the most common method of doing a weight check. You get in water too deep to stand, dump all the air out of your BCD, and hold a normal (not big) breath. You should float at eye level. If you exhale, you should sink. With that in mind, a recreational, single tank diver should have no trouble staying at the surface without air in the BCD, unless that diver is significantly overweighted.
.

I assume this is done at the beginning of the dive, with a single tank, right? If so, is this assuming a five pound shift in buoyancy (i.e. AL80)? Presumably this will make a diver neutral, or very slightly negative, at 15 feet at the end of the dive with 500 psi left in the tank?

 

[dmaziuk]

I don't believe that the issue is overpressure. Ever tried to use a bag for buoyancy? Even if it has a dump valve at the top, it's pretty darned difficult to avoid that it just corks. I use a large, old dSMB to provide buoyancy to my catch bag when I have a decent amount of scallops, but it's a major PITA to try to do anything except just sending it to the surface by itself.

Ah, OK. I guess I was thinking more of letting it go and pulling myself up by the line. I can see how continuing a dive with a bag for BCD could be... challenging.

 

[Diving Dubai]

I assume this is done at the beginning of the dive, with a single tank, right? If so, is this assuming a five pound shift in buoyancy (i.e. AL80)? Presumably this will make a diver neutral, or very slightly negative, at 15 feet at the end of the dive with 500 psi left in the tank?

John has quoted the PADI spec. I teach this with an empty (50bar) to float at the waterline. With a full cylinder, I teach that your head just goes below the water before you exhale and thus you being in the ball park for a SS being neutral at 500/50

 

[JamesBon92007]

I don't believe that the issue is overpressure. Ever tried to use a bag for buoyancy? Even if it has a dump valve at the top, it's pretty darned difficult to avoid that it just corks. I use a large, old dSMB to provide buoyancy to my catch bag when I have a decent amount of scallops, but it's a major PITA to try to do anything except just sending it to the surface by itself.

What I had in my mind would be that, for example, the BC has failed and the diver is having difficulty maintaining a 15 foot safety stop and is finning furiously and takes out the lift bag and fills it just to the point that it provides enough lift to be neutral or very close to that. If the failure occurred at depth then some kind of control over the air volume in the lift bag would, of course, be needed. I have not actually tried it but I'm thinking that tilting or squeezing the bag to let some air out shouldn't be too difficult. The SMB I have has a dump valve so if it was used for an emergency buoyancy device it should be fairly simple to adjust the amount of lift while surfacing. I would think the same would hold true for a "bottom fill" type SMB which, I assume, is open at the bottom. I doubt that these techniques are taught in basic scuba classes and the obvious choice would be to dump weight. But, for some reason, it seems that when divers are in trouble they seem to be reluctant to do this, judging from incident reports where divers are found with their weights still intact.