Comparative SMB Performance Following Free Ascent

[flots am]

Inflating the bag using a regulator second stage to 4-5' was not difficult, however as the bag became longer on top, it tended to flop over more, and became harder to control. Diver 1 attempted to keep the bag lifted straight-up out of the water, by holding it underwater while at the surface. This could be done, but required an expenditure of effort and periodic breaks. (Note that it is not at all difficult to fully inflate the same SMB from depth and hold it vertically during a free ascent -- the difficulty arose because it was hard to maintain downward tension on the SMB once at the surface.)

Not related directly to the outcome of this incident, but I have a large SMB and if I need to leave it inflated on the surface, pull a weight pouch and clip it to the bottom. The bag will stand up on it's own after that.

It also lets you easily top off the air in the bag, since you no longer need to wrestle with it. I also bring a Tektite 2-c-cell strobe that will clip off to the SMB's top loop in case night "happens"

The difference between "paranoid" and "prudent" is only visible in hindsight.

flots.

 

[djcheburashka]

Yeah I usually don't dive with lead, I never dive with removable lead, and from the size of this bag and the force I had to exert to keep it upright I think it would take about 10 lbs.

 

[flots am]

Yeah I usually don't dive with lead, I never dive with removable lead, and from the size of this bag and the force I had to exert to keep it upright I think it would take about 10 lbs.

Might be something to consider.

Your life might someday depend on being able to be visible. Could you hold the bag up all day/night?

 

[djcheburashka]

Not a chance, but I have to think there are better options than a bag + 10lbs of lead whose only purpose is to anchor the bag.

My belief at this point is that the big yellow xs scuba bag can be seen for miles. The solas tape makes me confident that if there was an actual search party they'd find me pretty quickly. At night, or of its a hot drop, I'll either carry a second bag, or a nautilus lifeline. I'm not a huge fan of the lifeline because I suspect that if I ever had to use it, that would be the day I discover the battery now only holds 1/50th a charge...

I wonder how large, statistically, the "boat doesn't see bag, diver spends x hours in water or floats off to drown" risk actually is. How often has this happened? At all in recent years?

 

[WarrenZ]

Why not clip bag off to waist strap or chest during to keep it with you and upright?

 

[djcheburashka]

This is starting to veer off-topic but, that wouldn't keep it upright. It has to be held 8" or so under the surface to stand fully upright, and that's (rough estimate) 10lbs of negative force. If you're floating on the surface with your wing inflated enough to keep you there, you don't have 10lbs of negative buoyancy to spare.

 

[Peter69_56]

Most Tech divers would have both Orange and Yellow SMB, orange for normal use and yellow to signal a gas issue during deco. Good to know though that the Orange is best at night. Anyone used reflective tape on them, something I have been thinking of doing.

My yellow also has a small 2" plastic slate for writing the issue if during deco.

I also find if you don't quite fill them fully they are easier to hold down in the water to stay upright. If they are totally full and tight they fall over more easily

 

[djcheburashka]

Grrr... The yellow/orange rule is a British or European practice. It isn't standard for tech divers generally.

I didn't say that orange was superior to yellow at night. The issue was that the thicker material on the higher quality smb didn't pass the light as well as the thinner material on the cruddy one. And a small one is easier to manipulate.

As for leaving it partially deflated, the smaller the inflated portion the easier it will be to control but all other things being equal having a longer floppy part underwater doesn't change anything.

 

[Peter69_56]

Grrr... The yellow/orange rule is a British or European practice. It isn't standard for tech divers generally.

I didn't say that orange was superior to yellow at night. The issue was that the thicker material on the higher quality smb didn't pass the light as well as the thinner material on the cruddy one. And a small one is easier to manipulate.

As for leaving it partially deflated, the smaller the inflated portion the easier it will be to control but all other things being equal having a longer floppy part underwater doesn't change anything.

Everywhere I have been to date, they understand and use the Orange/yellow in tech although it wasn't in my TDI (US) training. Is this another "Not in the US or dominions" thing, like K valve?

Also (from experience) the bit not inflated (not longer part), helps stabilise it by acting like a rudder of sorts or counter weight. It only has to be 3-4 inches (5-10%) and you pull down and it easily stays up with little effort and the remaining 90% is filled tight and stays erect. If its fully inflated tight, it falls over and a big effort to get any part of it in the water and more effort to keep it there, so I would suggest respectfully, that (from experience) it changes it a lot.

 

[djcheburashka]

Well, in the US we say yellow/orange is an only-UK thing. As for the bottom of the SMB, really depends on the size, no?