Ca't access my shears...????

[rcohn]

Spectre once bubbled...


That and back when diving was mostly a warm water sport. During dive briefings I give instructions on how to go about getting my weight belt off [double buckle as well as a thigh pocket threaded through]. The introduction to that lecture is always "If you feel you need to sentence me to death"....

I have no doubts that dropping a 20# belt at depth will result in my death.

And why should that kill you??? British submariners have demonstrated that ascent rates over 500 ft per minute can be done without embolism. It sounds like your skills need work.

Ralph

 

[tchil01]

Not only do I have my weight belt under my TP II, but my crotch strap goes over the belt. That's what saved me last weekend when the weight belt buckle snagged on some old fishing line and popped open. Now I'm sporting two buckels on my weight belt.

Ty

 

[Cave Diver]

rcohn once bubbled...


And why should that kill you??? British submariners have demonstrated that ascent rates over 500 ft per minute can be done without embolism. It sounds like your skills need work.

Ralph

Please state the source of your information so others can read about this firsthand.

 

[rcohn]

I'll need to look for the original reference, but here is some stuff from a quick search.

http://www.diodon349.com/Stories/General/forget_blow_and_go_and_good_bye_steike_hoods.htm

"Don't hold your breath - breath normally, relax, and enjoy the ride - it's going to be the best one you ever had," Sandoval said. Since the suits are inflated, sailors bob to the surface at a rate of about 725 feet per minute.

"It feels unnatural for a diver," said Hull Technician Second-Class Travis Swink, one of the instructors who tried out the suits in a 100-foot dive tower in Great Britain. "Our whole career we're taught to follow a certain feet-per-minute ascent rate, and with this thing you're just screaming to the surface."

http://www.bevs.org/diving/sett.htm

The serious purpose behind the SETT is to train and recertify our fleet of Submariners in their escape training. They perform three escapes, one from 10m, one from 18m and a final one from 30 meters. This ascent usually takes about 7 seconds !! Divers please note that this is not an acceptable ascent rate !!!

30 m in 7 seconds is 281 ft/ minute

http://www.divernet.com/technol/escap298.htm

http://www.mindspring.com/~divegeek/biblios/ascent.htm

That will do for now. I'm not suggesting it's easy to do these rates, it requires special training that only submariners have. However, with the drag of scuba gear our rates are slower. If you believe you are going to die, you probably will panic and die as a result. Relax, breath normally or exhale continuously, flare to slow the ascent and you should be ok.

Ralph

 

[rcohn]

A bit more.

No rate given here but i think most of us will realize that is is rather high when sealed in a inflated suit, much higher than when a weight belt is lost.
http://www.dnd.ca/menu/maple/vol_3/Vol3_32/navy_e.htm

The reliance on rescue depends on the ability of the crew to control the situation in the submarine, stabilize the environment in the escape compartment and await rescue. In the event that the crew cannot wait to be rescued-air is running out, for example-they will don their SEIEs and exit the submarine, one at a time, through the escape tower.
The SEIE provides buoyancy and breathing air during the escape sequence, and thermal protection on the surface. If the crew must leave the submarine immediately due to a sudden and uncontrollable situation, such as flooding, they will conduct RUSH escape by equalizing the compartment with the sea and then exit the submarine in rapid succession through the escape tower. Escape is possible down to a depth of 180 m.

In a non-RUSH escape sequence, the escaper dons an inner thermal suit over his normal clothing, then gets into the SEIE and pulls up a large waterproof zip that encloses him from head to toe. Upon entering the escape tower, he plugs the hose on the sleeve of his suit into a dry clean air supply from the Hood Inflation System, which provides air for breathing as well as to fill the integral stole, or life preserver, in the suit. The tower is then flooded up from sea, and as soon as the tower pressure equalizes with sea pressure, the upper lid automatically opens. With the hood of the suit filled with air, the escaper is positively buoyant, and automatically rises to the surface. The escaper continues to breathe normally all the way to the surface, with the excess air pressure within the suit automatically bleeding off through vents.

If the hood is not inflated, or not fitted during RUSH escape, the escaper must exhale continuously as he ascends to get rid of the expanding air in his lungs. Once on the surface, the vents are shut, trapping the air in the suit and enabling the escaper to float

US Navy escape proceedures:
http://www.uboat.cz/down/zajm/salvage.pdf

WARNING
Failure to forcibly exhale during the entire ascent to the surface may cause an air embolism, resulting in
death.
15. Upon exiting the trunk, the escapees extend their hands above their heads and clasp their thumbs together
to help guide themselves to the surface and to avoid debris and other survivors. During the ascent, the escapees
should forcibly exhale to ensure that pressure does not build up in their lungs. The escapees can shout
”HO–HO–HO” as a way to continually exhale during the ascent.

http://www.netcomuk.co.uk/~lucyht/Lsac/clubmag/marapr02/letters.htm

The main piece of 'personal' equipment used during 'in water' escapes would be a Mk 10 escape suit. This is similar to a membrane drysuit with boots and cuff seals, but it has a built in buoyancy jacket and a plastic hood - and an inflatable personal liferaft strapped to your waist.

The more controlled of the 'in water' escape methods involves you donning the suit (including putting the hood on - a bit like putting a plastic bag over your head - which your Mum told you never to do!). Climbing into the escape tower where you connect a pipe from your buoyancy jacket to an air supply and you then breath the air escaping from the jacket. They would then pressurise the tower to equalise the pressure with the outside water, the escape hatch would open automatically and 70 lbs. of buoyancy would blast you to the surface. The pipe connecting you to the air supply would be pulled out as you left the chamber but air escaping from the jacket as it expanded would go into the hood and you would breath that (mainly of course breathing out as the pressure quickly reduces - don't want to escape from a submarine and die of a burst lung!). Time for ascent? Approx. 8 seconds from 30m! This method of escape is reliable and has even been tested down to depths of 180m! - But it is slow, only 1 person every 4 minutes.

The last method of escape is called the 'rush' escape. This would be used if the submarine was badly damaged and pressure was building up, or the atmosphere was getting uncontrollably foul and you had to get people out quickly. In this case the escape chamber (the room below the escape tower in which you had all congregated) would be flooded and pressure equalised with the water outside. You would be breathing off a regulator similar to a diving one (but without a purge button) the exhaust of which you use to inflate your buoyancy jacket. You move through the chamber swapping regulators as you go until you get close to the escape tower. The tower would be extended downwards by a canvas tube, and you would have to duck down (against the 70 lbs. of buoyancy) and then you should float up through the tower and out. This method can get a man out every 4 seconds - but for the guy at the far end of the queue? Nitrogen Narcosis, more chance of getting the Bends and if you were deep enough Oxygen Toxicity….

Ralph

 

[raxafarian]

I think exiting a sub after breathing air at atmospheric pressure (or pressurized air for a very short time...ie. as the escape chamber is pressurized) is quite a bit different than having been breathing compressed air while diving. Plus... they have a choice... try and get out and make it to the surface by the only means possible... or die. If their situation is stablized, they are going to wait for a rescue as long as possible... with locking out a last resort.

The only reason I can think of to drop a weight belt at depth is dealing with an unconscious diver, etc and I'm gonna miss a deco stop to get them to the surface ... then I'm thinking that's their best chance, and up they go... I'm not trained in such diving... just my best guess.

If you can't swim up for any reason, and I don't know of any reasons why you wouldn't be able to... why drop it all... take a weight pouch out... or take the belt off and take one weight off...

If you're at the surface... lost the boat... drifting out to sea.... and so on... sure, dump the belt... weights are cheap.

 

[raxafarian]

the navy doesn't to the actual ascent training anymore... they might talk about it in the classroom, but no more actual ascent training... and not for many years now.

 

[Scuba446]

Well,
I got it all worked out and now wear my weightbelt under my harness. It doesn't interfere with the harness at all.

 

[rcohn]

1. No one is recommending dumping the weight belt, the question is will you almost certainly die if it happens.

2. Whether it’s 1 second or many hours at depth, the risk of embolism is the same, which I assume (hope) is why Jeff thinks he will die.

3. Whether the US Navy still does the training is irrelevant, a rapid ascent is still possible. I believe the US Navy still carries escape gear and the British still do the training. Even it everyone immediately ceased all rapid escapes, thousands of training dives and a few actual escapes were done in the past.

It comes down to proper training and education, a subject on which many people on this board love to pontificate. Very rapid ascents are possible if you breathe normally or exhale continuously and relax. If you believe that you are going to die you will be in a panic, where the natural reaction is to hold your breath. If you panic and hold your breath, you will embolize and may die.


Ralph

 

[Scuba446]

Well I can't figure out WHY then these agencies are still teaching that skill - Emergency Dumping.

?