desert your buddy pressure survey

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Originally Posted by aainslie

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Originally Posted by Jason B.

I realize this is a few days old but thought I'd throw in what I was taught (as it appears everyone does it differently).

If the separation occurs on the penetration side of the dive, I was taught to take the gas used and add it to my original thirds. This becomes your new turn pressure. So if you go in with 3600 and your original thirds was 1200 and you used 500psi to penetrate up to the point that your buddy goes missing, your turn becomes 500 (gas used) + 1200 (original thirds) to give a new turn of 1700psi.

If the separation occurs on the exit side, I was taught that you need a gentlemen's agreement prior to the dive that says you are allowed to use your buddies 1/3 to search for him.

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That's a nice but wildly conservative rule. A better one mught be to just double the gas used so far and go with that. So if you've dropped from 3600 to 3000, your exit should be at 2 x 600, i.e. 1200.

Even that only works on the way IN. Let's say on the way OUT you're 700 ft from the end and your buddy is gone. You're WAY past thirds - let's say you're down to 1500 psi left. Do you leave immediately?

These simple rules don't really work that well IMHO. You need some idea of the flow, viz and depth, and your gas usage per 100 feet in that flow/viz/depth. In a high flow cave at 60 ft I'd go down to 500 psi in that situation. In a low flow cave at 100 ft, maybe 700 psi or so. If it's a creepy little Cindy cave, perhaps 1000. Basically I think one has to have the nous in an emergency to realize that the TRUE lowest pressure is that they're willing to accept.

Lee and Rich, my thought would be to know what twice one's required gas is - and THEN make a decision about eating into that reserve. It would take a pretty cold blooded diver to exit without eating at least somewhat into that reserve. But I don't think I'd ever have the guts to use the entire reserve - maybe half of it.

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Well there you go....that's why I think it's important to know your cave. Progressive penetration and check on each dive (especially those creepy little caves I like so much) what it takes on exit. Many creepy tunnels are less than 300' from exit and in a silt out (happens often) take more time than you would think. There is no pat answer here, except maybe be comfortable with what you got before spending the excess.

Once again, good luck ya'll. Hopefully no one ever again will have to test their own theories. Yup. Maybe there will be world peace too. :?


Angie

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Originally Posted by Angie Reim

Didn't fetus lungs Gary do a Grand Traverse at Peacock once (deliberately skip breathing)? He did it on like 1/2 the usual gas or something. Gary tell us again.

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Nothing that exciting but I did test some theories on wing re-breathing vs efficient breathing on some dives way back and found exagerating proper breathing technique to be preferable. I'm sure in need I could go to full skip breathing and get even more gas extension and just live with whatever headache came from it - just depending on what needed to be accomplished and with how much availiable air.

On the other hand cold and or stress might limit the usefulness in many cases (I've been on a dive where I was so cold I used nearly double the air to exit and nearly used my entire reserve).

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Originally Posted by http://cavediver.net/phpbb2/viewtopic.php?p=7964#7964

I actually gave the wing breathing a try. After throughly cleaning my wing I went diving and gave it a try. I attempted a one breath to every 2 from the wing but found it hard to get water free air breathing from the wing and I still had to clear the reg each switch as well. It took some attention to do and distracted me from even swimming properly or watching where I should be going.

I have thought of a few ways to improve my first attempt but overall I concluded that unless I was going to sit still in one place and do nothing but pay attention to rebreathing the wing I could extend my air better by skip breathing, efficient swimming and paying attention to the cave.

Long, deep, slow breaths with an extended pause after each inhalation followed by a full exhale could extend most people's air by 50-100%.

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Originally Posted by Gary

After throughly cleaning my wing ...

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:?:

I thoroughly clean my wing after every dive trip. Maybe that's why my ten-year-old wing looks like new. ;-)

Well if you do as you were trained and not go past your 3rds then you will more than likely survive. I was trained to cover light look for buddies light if you don't see him then look for you turn pressure from start of dive not recalculate your 3rds because you could do this or spend more air looking then find them on the way out and he be out or close to and he might be stressed and breath twice his normal A.C.R. and you will need all you have to exit safely. I was trained to never go past my 3rds ever no matter what. I was trained also to do the search hit my turn pressure leave my slate with a note that I have exited the cave along with a backup light turned on clipped to the line in case his light is out and he needs it or he might see the light and come back to it. I know you said you had a deco or stage involved well then you need to do a 3rds cal. from that tank then if you have extra time from that point of course I would use it.