It does have something to do with reserve but there is more...
O-ring just got schooled on this very subject.
I wonder if he will share?
Who Wears A Snorkel When Diving ?
- Thread starter DiveTub
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O-ring just got schooled on this very subject.
I wonder if he will share?
otter-cat
Guest
If you are diving in areas with good vis, I can understand using a snorkel, so you can enjoy your surface time more, and maybe scout out a good location to descend. Where I live, the visibility is generally low enough that I can't see the bottom unless I'm 3 feet from it, so I don't use the snorkel much. I have one, and I wear it sometimes, but it's mostly a pain in the a**. I feel confident enough that if I am at the surface I will be able to breathe (EVEN in choppy seas, and the seas DO get quite choppy offshore here) that I think the nuisance of the snorkel outweighs the benefit. However, for those who are less comfortable being thrown around by the waves, I can see where carrying the snorkel might be more worthwhile. If you find yourself surfacing to unpleasant conditions, having the snorkel can make things a little easier, which is why telling a panicked diver to use their snorkel sometimes helps to calm them down.
So where bouts are you diving there otter-cat...
I just got back from a conference at Canon Beach and stopped by the dive shop in Seaside to ask where they were diving... the first word out of the shop keeper's mouth was "Seattle" followed by "and Hood Canal"
JimC
Contributor
Enough air to get you and your buddy to the surface, from 130 feet in a non-deco openwater dive?
Good answer Jim....
However... while in principle that is right in specifics it is wrong.
How much gas would it take for you and your buddy to make a safe, controlled ascent at ~33 fpm doing either a safey stop of 3 minutes at 15' or minimum deco of 1 minute at 30'/20'/10' from:
66 fsw
99 fsw
132 fsw
You will need to know your SAC & your buddy's SAC.
You specify the tank you are using... it makes a difference.
dvleemin
Contributor
So a 132 fsw, you'll be down 7 mins (132/33 + 3 min safety stop).
Lets assume an SAC of 1.0ft/min
That means you need 7 cubic feet air
So for an AL80 that means about 263 PSI is needed.
So for you and your buddy to reach the surface from 132 fsw, you need ~500psi.
*******
I think all of the above is wrong however. You would need a mathematical formula to calculate how much air you use at each depth. The above does not take this into account.
****************
Any comments on the above though?
Darryl
But you do need to take into account greater air consumption at greater depths.
1) One way to this is to figure your reserve (we call it rock bottom) at the 66' depth. That is three ATA. Figure it your transit time from 66' to 33' all at 3ATA for a safety factor. Then figure your time from 33' to the surface at 2ATA for an additional safety factor.
2) Next figure the amount necessary to go from 99' (4ATA) to 66'... figure it all at 4ATA and you have fudged in a safety factor.
3) Next figure the amount necessary to go from 132' (5ATA) to 99'... figure that all at 5ATA and you have an additional safety factor.
Reserve from 132' would be the 66' reserve plus the extra from step 2 and step 3.
I would have three different rock bottom (reserve figures) for planned depths in these ranges.... easy to remember... if you figure them ahead of time.
btw you SAC of 1 might be too high but then in an emergency air sharing ascent it might not be too high at all
So how do you explain metric spg's having the "low on air" mark at 50bar (735psi)?
My guess is that mathematics were never used, who ever established 500psi and/or 50bar thought they were nice round numbers.
My guess is that mathematics were never used, who ever established 500psi and/or 50bar thought they were nice round numbers.
slichti
Guest
I find it hard to use a snorkel with a 7ft hose... It would get caught unwraping it for an out of air diver.
--Steven.
--Steven.
Steve,
Just make sure you have it when you show up for rescue class. We will use it to make our masks leak and to bang ourselves in the side of the head. And of course the snorkel will provide that little bit of extra drag that the rest of our kit fails to provide.
Cave diving rule #six - If you break the first five, don't let them find you with your snorkel on.
Mike
Just make sure you have it when you show up for rescue class. We will use it to make our masks leak and to bang ourselves in the side of the head. And of course the snorkel will provide that little bit of extra drag that the rest of our kit fails to provide.
Cave diving rule #six - If you break the first five, don't let them find you with your snorkel on.
Mike
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