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ACR
November 3rd, 2008, 02:16 PM
Ok, so there I was in Cozumel on a cattle dive drifting peacefully along looking at all the pretty fish, turtles and alike. I check my gauges as I am prone to doing from time to time and I notice that I'm nearing the pressure at which I would typically turn a dive... I like to leave a small safety margin such that if there's any oddness that happens I won't drown, typically this means being on the surface with about 500psi in an AL80.

So I signal to my Buddy that I'm low on air (the agreed upon turn signal) and he looks at me as if to say "***??" and signals that he'd prefer to give it a few more minutes. Now I'm the first to admit that I'm not the kind of guy that can breathe of an 80 all day long and still have gas for the next day of diving but give me a break, if someone calls a turn you turn and you don't give your buddy a hard time about it... maybe it's just me.

Next time I'm bringing along my own buddy.

Blackwood
November 3rd, 2008, 02:20 PM
if someone calls a turn you turn and you don't give your buddy a hard time about it... maybe it's just me.

It's not just you.



We may razz eachother about gas consumption now and again... on the surface. But during a dive, when anyone says it's over, it's over.

dkktsunami
November 3rd, 2008, 02:32 PM
Find a new buddy. Indicating low on air and turning a dive is not a request, it is a demand.

Guba
November 3rd, 2008, 02:49 PM
Okay, let's think about this...
Signalling that you are low on gas is stating a fact that is not in question. In other words, it's not like you can say, "You don't want to turn? Okay, well, we'll do it your way."
You don't have another practical option. Your partner should heed your judgement and turn, just as the dive should terminate for ANY reason provided by EITHER diver (I'm cold, my ears are having problems, or "I just don't feel comfortable and want to go up" are ALL valid reasons to turn the dive.) All your partner has lost is a few minutes underwater. He has to get over it and be a buddy.

tstormdiver
November 3rd, 2008, 02:52 PM
For me with an insta- buddy or any buddy,...... Any diver, can end any dive, at any time, for any reason, no questions asked. Make sure you clarify that with your buddy BEFORE the dive

StreetDoctor
November 3rd, 2008, 02:57 PM
Bad buddy.

J.R.
November 3rd, 2008, 03:03 PM
Bad buddy.

... no cookie!!!


tstormdiver wrote, "For me with an insta- buddy or any buddy,...... Any diver, can end any dive, at any time, for any reason, no questions asked. Make sure you clarify that with your buddy BEFORE the dive"

AMEN... and I'll add that, when I'm diving as a DM or as just yer' buddy I make it a practice to state PRECISELY what tstormdiver just said. A lot of times my buddy(s) may say, "Yea... we know that." To which I'll respond, "Well, I'm stating it anyway... as much for my benefit as for yours."

Time to find a new buddy...

ScubaSteve
November 3rd, 2008, 03:14 PM
What??? Are you selfish??? If he is not ready to turn then you do not turn. That simple. :D Of course this is a ridiculous scenario that should never have happened. You reach the turn pressure you turn. 'Nuff said. I say that guy deserves to be diving alone. The good thing is, you were in the right and hopefully you never have to dive with him again. It seems like a common sense thing....but as tstormdiver said....clear the air before the dive even if it should be known and clear. Now we all know.

So what happened after he said let's wait a bit? I hope you were already safely ascending after grabbing the guys fins and dragging him (:joke:)...seriously I hope he smartened up immediately and you surfaced with air to spare.

texdiveguy
November 3rd, 2008, 03:20 PM
There are certain underwater universal dive signals that are in the command category......'turn the dive' is one of them!

ACR
November 3rd, 2008, 03:34 PM
So what happened after he said let's wait a bit?

I convinced him to turn by signaling and then starting my accent... There was still plenty to see at the 15foot safety :)

don Francisco
November 3rd, 2008, 03:38 PM
There's a material difference between a buddy and someone who just happens to be in the water near you. You were diving with the latter.

Since you were drift diving in Coz. I assume that by turn the dive, you really mean end the dive, meaning begin the ascent to the surface. In either case, the turn or end the dive sign is a command not open to debate, and can only be considered a question if clearly signed as such.

Suggestions for the future: pick your buddies more carefully, and get agreed on communication, estimated dive time, and what you'll both do if one needs to terminate the dive early, meaning way before the estimated time.

Also, you could work on your air management somewhat (though it has no bearing on your buddy's faiulure in this case). One thing I do is get my buddy to agree that whoever is first to half tank let the other know. This way, both of know fairly early what our relative air consumption is and we can sometimes modify the dive accordingly. For example the lower on air buddy can focus more on the reef tops, while the long on air buddy can prowl the bottom. The difference of 5-10 feet of depth will help both divers to equalize their air use and get the most out of the dive.

With good communication and cooperation 2 mis-matched divers can each enjoy their dives to the fullest, but if they don't plan to work together they might as well admit they're really diving solo.

sambolino44
November 3rd, 2008, 09:28 PM
This just reminds me of all the times I have failed to do a good job of talking this kind of stuff over with my insta-buddy. Fortunately it's always worked out so far, but mostly because of good luck. Every time I read something like this I vow to work harder to do a good pre-dive brief with my buddy, no matter who it is.

I have a checklist so I won't forget any gear; I think I'm going to work on a pre-dive brief checklist.

NudeDiver
November 3rd, 2008, 10:29 PM
Reach over and turn his air off and see if he is still interested in continuing the dive.

Rick Inman
November 3rd, 2008, 10:34 PM
People have died due to peer pressure and ego. Not immediately returning the thumb and ending the dive without question is a safety issue. And anyone who I see giving anyone else a hard time for turning a dive for any reason will not be my buddy.

diver 85
November 3rd, 2008, 10:43 PM
Ok, so there I was in Cozumel on a cattle dive drifting peacefully along looking at all the pretty fish, turtles and alike. I check my gauges as I am prone to doing from time to time and I notice that I'm nearing the pressure at which I would typically turn a dive... I like to leave a small safety margin such that if there's any oddness that happens I won't drown, typically this means being on the surface with about 500psi in an AL80.

So I signal to my Buddy that I'm low on air (the agreed upon turn signal) and he looks at me as if to say "***??" and signals that he'd prefer to give it a few more minutes. Now I'm the first to admit that I'm not the kind of guy that can breathe of an 80 all day long and still have gas for the next day of diving but give me a break, if someone calls a turn you turn and you don't give your buddy a hard time about it... maybe it's just me.

Next time I'm bringing along my own buddy.

OR, next time try Aldora, they dive HP 120's......make sure your buddy has one of their HP 80's---that ought to work......

vicdiver656
November 3rd, 2008, 10:45 PM
Ok, so there I was in Cozumel on a cattle dive drifting peacefully along looking at all the pretty fish, turtles and alike. I check my gauges as I am prone to doing from time to time and I notice that I'm nearing the pressure at which I would typically turn a dive... I like to leave a small safety margin such that if there's any oddness that happens I won't drown, typically this means being on the surface with about 500psi in an AL80.

So I signal to my Buddy that I'm low on air (the agreed upon turn signal) and he looks at me as if to say "***??" and signals that he'd prefer to give it a few more minutes. Now I'm the first to admit that I'm not the kind of guy that can breathe of an 80 all day long and still have gas for the next day of diving but give me a break, if someone calls a turn you turn and you don't give your buddy a hard time about it... maybe it's just me.

Next time I'm bringing along my own buddy.

That's not cool....
In many of the OW textbooks, there is the following statement: "ANY DIVER CAN TURN THE DIVE AT ANY TIME FOR ANY REASON."

I'd find another buddy. There is no way that he should say no to turning a dive just because he has a few more PSI left in his tank. It's like a doubles diver forcing singles divers to continue the dive even when they're getting low on air just because he has the extra air in his tank and wants to use it.

I'm sorry that you had a bad experience with your buddy.

Taylor
vicdiver656

diverrex
November 4th, 2008, 02:05 AM
I quess I have a different take on this after having made two trips to Coz this year. The water is typically clear, 70+ viz, warm water, little surface chop, the diving is easy, you are usually in a group dive with a DM and a boat following at the surface. My buddy is my wife, she uses less air than me. When I get down to about 500 PSI I ascend by myself. She stays near the group and DM. I can still see the group below, they see me. I see the boat above, they see me. I do a safety stop then surface and the boat picks me up, no problems.

Now our typical California diving with maybe 20-40 viz and it's just my buddy and I, when one wants to surface the other does also. Different conditions, different actions. This weekend we did three boat dives. My insta buddy warned me he was a heavy breather. I had my HP 130 just in case I ended up with a very light breather. With the heavy breather I never used more than half a tank. No problem, I'll gladly pass up up some dive time to make sure my buddy is safe.

TSandM
November 4th, 2008, 02:34 AM
Diverrex, what happens if you are on ascent and you find out your gauge was wrong, and you're out of gas? I guess you CESA . . . I wouldn't like to be in that position, and if I were your wife, I'd feel HORRIBLY guilty if something happened to you because you were ascending alone.

To the OP: As so many have said, anybody can call a dive at any time, for any reason; a buddy who ignores the thumb is not really a buddy. But that as a given, it would help to review with your instabuddy what your signals and protocols would be. If you have agreed that either of you can thumb the dive, you might be more likely to get a positive response.

If I were on a Cozumel dive with an unknown buddy and got the thumb at 20 minutes or so, I have to admit I'd be irked . . . But I'd go. I might try to arrange not to do the next dive with the same buddy, but I am not going to be responsible for keeping someone underwater longer than they want to be there, whether the reason for leaving is gas, NDL, comfort, or something entirely other. But you cannot reasonably expect from your buddy something you have not discussed beforehand. What you might assume is normal buddy behavior, may not be at all for the person you got paired up with.

diverrex
November 4th, 2008, 02:51 AM
Diverrex, what happens if you are on ascent and you find out your gauge was wrong, and you're out of gas? I guess you CESA . . . I wouldn't like to be in that position, and if I were your wife, I'd feel HORRIBLY guilty if something happened to you because you were ascending alone.


TSandM - I respect your opinion more than about anyone else on this board. You make a valid point. And if I'm at 100 feet I definately agree. But if it's toward the end of a dive and we have multi-leveled up to 50 feet or less I am willing to trust my gauge or CESA if needed. But I'd never let my wife surface alone.

I consider the dive op we go with in Coz very high quality and safety minded, yet on many dives they would have divers ascend solo, once they dived with the diver a few days and were comfortable with their experienc level. I quess many disagree with that practice and I can understand that position. I have always ascended with my buddy when they want to go up first, but I am willing to ascend on my own.

Not to change the subject much but I do always dive with a buddy (except a few Coz ascents I guess). It always surprises me how many people dive solo in So Cal and without redundant air. I'm quessing the boat I was on this weekend had 6 solo divers out of the 30, none with redundant air, mostly photographers that want to be left alone.

don Francisco
November 4th, 2008, 06:05 AM
Diverrex, what happens if you are on ascent and you find out your gauge was wrong, and you're out of gas?

With all due respect, this is a highly unlikely situation, bordering on the "never happen".

Gauges are among our most reliable pieces of equipment, and the risk of one to being off 300-500psi at the low end of the scale is negligible, bordering on zero. I'm far more comfortable trusting my gauge than I am about most other things or people. If that weren't so, I'd replace it.

Those who aren's so sure about their gauges can test the low end readings once in a while by closing the tank valve and slowly breathing the air in the lines down to zero. The reg should start breathing harder as the gauge reads about 100psi and should deliver air until the gauge bottoms out.

MasterFritts
November 4th, 2008, 07:53 AM
I dunno, things can go wrong in anything you do (like hitting a bird in a single engine airplane during the night at 3,000 feet). Just ask good ole Murphy. They even named a law after him. The gauge thing is just one possibility, I am sure there are others.

To me you are in an alien environment for your body. You have a life support system keeping you alive. There are a lot of variables. Better safe than sorry or worse dead.

I know when my wife's knee gets better from surgery I will be dragging her up to 15 feet with me. :)

UnderSeaBumbleBee
November 4th, 2008, 08:14 AM
I quess I have a different take on this after having made two trips to Coz this year. The water is typically clear, 70+ viz, warm water, little surface chop, the diving is easy, you are usually in a group dive with a DM and a boat following at the surface. My buddy is my wife, she uses less air than me. When I get down to about 500 PSI I ascend by myself. She stays near the group and DM. I can still see the group below, they see me. I see the boat above, they see me. I do a safety stop then surface and the boat picks me up, no problems.




With all due respect, this is a highly unlikely situation, bordering on the "never happen".

Gauges are among our most reliable pieces of equipment, and the risk of one to being off 300-500psi at the low end of the scale is negligible, bordering on zero. I'm far more comfortable trusting my gauge than I am about most other things or people. If that weren't so, I'd replace it.

Those who aren's so sure about their gauges can test the low end readings once in a while by closing the tank valve and slowly breathing the air in the lines down to zero. The reg should start breathing harder as the gauge reads about 100psi and should deliver air until the gauge bottoms out.


What if your wife had a stroke or other medical event? How would you feel watching her struggle from 70' above with no way to help her? What if the other divers did not notice as she was not their buddy?

People can seem healthy and then have a medical event. Board member Littlejohn, just had an event, went for a couple of dives, got back on the boat and the events that ended his life a few days later began. Had he been in the water a few more minutes, those events would have started under water and he would have needed a buddy to help get him out of the water for the best chance of survival.

I am pretty healthy, go for my physical and have all the blood work an other good stuff done. About a year ago, I had a visual migraine (sp?) Never had one before or since that I know of. All of the sudden I could not see clearly and the objects that I was looking at began to wave and wiggle and the colors were not what they should have been. I was filling out a report and knew in my mind what it should look like. I became sick just trying to see. No head ache by the way while this was going on. I felt fine. Had I been under water it would have been difficult for me to see to read my gauges and get to the surface without help.

It was a very upsetting experience for me. We can all have a medical event without warning. My visual event lasted for about 10 minutes and then has never happened again. 10 minutes of that underwater would have seemed like forever and if I had been on my own in the water who knows what would have happened.

ScubaSteve
November 4th, 2008, 09:27 AM
.......What you might assume is normal buddy behavior, may not be at all for the person you got paired up with.


This I believe is not a fair statement. I may be wrong (and I will admit if I am :D) but I shudder to think that anybody out there diving with somebody else but would ignore a start ascent sign. What I think is even scarier....that someone would consider that acceptable because it was not discussed ahead of time....scary. So would they also ignore an OOA sign because it was not discussed. This is where I may vary from some.....it has been said....certain signals, if done clearly, should never be ignored or questioned. Calling the dive is one of them.

Unless you tell the person ahead of time you are on your own, I believe you are buddy diving and it should be treated as such. I like that you (Lynne) would end the dive with your buddy because it was call (irked or not) and would just try to find another for the second dive. That is an appropriate way of handling in my opinion.

ScubaSteve
November 4th, 2008, 09:32 AM
With all due respect, this is a highly unlikely situation, bordering on the "never happen".

Gauges are among our most reliable pieces of equipment, and the risk of one to being off 300-500psi at the low end of the scale is negligible, bordering on zero.........


You might possibly want to call this statement into questioning. I will try to remember who it was and where the thread is (I am drawing a blank...hopefully someone else will recall it) but a well respected member of SB has personal experience of what exactly "acceptable tolerance" is to a computer/gauge manufacturer. This is not my personal experience however I DO have a computer, a tank checker guage and a buddy's console, all with a spread os 250psi from high to low....all different manufacturers but do you think you get to choose which one is accurate before the dive? I am personally going with the conservative one....that way I can dive again.

BDSC
November 4th, 2008, 10:00 AM
I quess I have a different take on this after having made two trips to Coz this year. The water is typically clear, 70+ viz, warm water, little surface chop, the diving is easy, you are usually in a group dive with a DM and a boat following at the surface. My buddy is my wife, she uses less air than me. When I get down to about 500 PSI I ascend by myself. She stays near the group and DM. I can still see the group below, they see me. I see the boat above, they see me. I do a safety stop then surface and the boat picks me up, no problems.

Now our typical California diving with maybe 20-40 viz and it's just my buddy and I, when one wants to surface the other does also. Different conditions, different actions. This weekend we did three boat dives. My insta buddy warned me he was a heavy breather. I had my HP 130 just in case I ended up with a very light breather. With the heavy breather I never used more than half a tank. No problem, I'll gladly pass up up some dive time to make sure my buddy is safe.

My buddy and I do the very same thing when we are in Cozumel. The conditions are usually just what you have described. Toward the end of the dive we are generally in 50 ft or so of water. So if one of us decided to go up and the other is not ready, we go up and the other stays with the group. We have been diving together for years and have no problem with this approach.

In other locations where the boat is tied up, we will go in one direction and then turn the dive together. When we get back to the boat we may go up together or one of us may swim around under the boat while the other surfaces. It just all depends on the situation.

BDSC

ScubaSteve
November 4th, 2008, 10:18 AM
......I can still see the group below, they see me.........

So the group below you is swimming on their back watching you? Why pay the money to be in Coz then? I can swim upside down here....


......I see the boat above, they see me.........

I call this one a bad name.....The boat can see your bubbles. Any time I have been in Coz, the water has been FAR from smooth as glass. This is what would be required for a boat to monitor your progress with a visual of your actual person. What good is this anyways? When they see your bubbles stop coming, are they going to hope you float to the surface or sink to the DM? You never mentioned launching an SMB? All of my Coz diving has been drift diving where the boat goes off a short distance and comes to the area of the SMB when the divers surface. In this, there is no way they could monitor your progress beneath the surface. I guess your dives were run differently.

I have been sent up on my own in Coz and did it, but to say that it is OK because everybody is watching you.....sounds like a big stretch to me.

BEM
November 4th, 2008, 10:20 AM
BDSC - If you or your buddy go up and the other stays with the group - has someone from the group agreed (before the dive) to be the new buddy?

BDSC
November 4th, 2008, 10:25 AM
BDSC - If you or your buddy go up and the other stays with the group - has someone from the group agreed (before the dive) to be the new buddy?

Nope. I guess you could say at that point we are buddyless. But depending on the circumstances, I don't have a problem with that. I have taken a number of trips to Bonaire and from time to time I will do a solo dive off the house reef. I have always felt safe and confident in doing so.

BDSC

Ruminari
November 4th, 2008, 10:31 AM
Ok so after quickly reading over a fair share of the post. I was just wondering a few things.

1. How deep was the dive?

2. Was it a follow the leader (DM) type of dive?

3. How long was the dive?

scubadiver888
November 4th, 2008, 10:41 AM
Ok, so there I was in Cozumel on a cattle dive drifting peacefully along looking at all the pretty fish, turtles and alike. I check my gauges as I am prone to doing from time to time and I notice that I'm nearing the pressure at which I would typically turn a dive... I like to leave a small safety margin such that if there's any oddness that happens I won't drown, typically this means being on the surface with about 500psi in an AL80.

So I signal to my Buddy that I'm low on air (the agreed upon turn signal) and he looks at me as if to say "***??" and signals that he'd prefer to give it a few more minutes. Now I'm the first to admit that I'm not the kind of guy that can breathe of an 80 all day long and still have gas for the next day of diving but give me a break, if someone calls a turn you turn and you don't give your buddy a hard time about it... maybe it's just me.

Next time I'm bringing along my own buddy.

This is why I chat up divers and find someone I know is not going to complain if we have to call the dive early. On an AL80 I usually have to surface due to nitrogen loading rather than running out of air but I'll leave everyone with the impression I'm average with air and will probably be the last guy down and the first guy up.

Another option is always stay a little more shallow than your dive buddy. I used to do this before I got better with my air. Just staying 10' above them will give you a considerable air savings.

Rick Inman
November 4th, 2008, 10:45 AM
Another option is always stay a little more shallow than your dive buddy.
Keeping together and aware of your buddy's location is the most difficult if he/she is above you.

Here's a question to ponder: if you are doing a dive at 66', how much gas/time will you save by being 10' shallower?

ScubaSteve
November 4th, 2008, 10:50 AM
........On an AL80 I usually have to surface due to nitrogen loading rather than running out of air..........

How does this work? A computer is built on algorithms that determine how much nitrogen has been absorbed into the system and what should have been passed from your system based on the depth and duration (and O2 content of course) of your dive profile. Unless you have more repetitive dives than the group, I do not see how you would have to call a dive due to reaching or approaching your NDL.....the only thing that I can think of that would get you there quicker is a more conservative computer (like mine...a Suunto) but this is minutes not tens of minutes and it is a cumulative effect not immediate. I do agre with you though....talk to people up front and determine which diver best suits your ideal profile for a dive buddy. Sometimes this will work because of the number of solo divers and sometimes it will not. Bottom line is, make sure the pre dive discussion is complete and happens, and make sure the DM knows what your plans are.

scubadiver888
November 4th, 2008, 10:54 AM
TSandM - I respect your opinion more than about anyone else on this board. You make a valid point. And if I'm at 100 feet I definately agree. But if it's toward the end of a dive and we have multi-leveled up to 50 feet or less I am willing to trust my gauge or CESA if needed. But I'd never let my wife surface alone.


This is selfish. Think about why you will not let your wife surface alone. I would guess you would feel horrible if something happened to her. Don't you think she would feel the same way if something happened to you? What is good for the goose is good for the gander.



I consider the dive op we go with in Coz very high quality and safety minded, yet on many dives they would have divers ascend solo, once they dived with the diver a few days and were comfortable with their experienc level. I quess many disagree with that practice and I can understand that position. I have always ascended with my buddy when they want to go up first, but I am willing to ascend on my own.


You sign a piece of paper that says the dive op is not responsible for most things and that diving is inherently dangerous. If you are diving 2 to 4 times a day, every day and nothing happens you start to become complacent. I dove with an operator in Aruba in December '06 then again in April '07 (4 months apart). The first dive was like your dive operator in Coz. In April they were more stricked. Turns out someone got hurt in February.

BDSC
November 4th, 2008, 11:00 AM
Keeping together and aware of your buddy's location is the most difficult if he/she is above you.

Here's a question to ponder: if you are doing a dive at 66', how much gas/time will you save by being 10' shallower?

OK. I tried to calculate this out. Not sure if I did it right but here goes.

Lets assume that at 66ft you will get 50 minutes of bottom time. I am just using this number because I have to use some number. If all conditions were the same but you were diving at 56ft, I calculate that you would get 58 minutes or an extra 8 minues.

BDSC

scubadiver888
November 4th, 2008, 11:07 AM
Keeping together and aware of your buddy's location is the most difficult if he/she is above you.

Here's a question to ponder: if you are doing a dive at 66', how much gas/time will you save by being 10' shallower?

If I'm diving at home or not on a cattle run I am usually right beside my buddy and within 3' (if I know them well I stay within 6"). If I have a good buddy on a cattle run I dive properly. If I have an insta-buddy and he is not paying attention to me I'll do the 10' above. Usually on these sort of lead dives we are above 60'. The viz also has to be 70'+.

I would never dive below 60' with an insta-buddy that I was not sure of.

When I first started diving, the group at 60' and me at 50' saved enough that I didn't have to be the first person up.

This is a temporary solution. My ultimate solution was to get better at gas usage.

BDSC
November 4th, 2008, 11:08 AM
OK. I tried to calculate this out. Not sure if I did it right but here goes.

Lets assume that at 66ft you will get 50 minutes of bottom time. I am just using this number because I have to use some number. If all conditions were the same but you were diving at 56ft, I calculate that you would get 58 minutes or an extra 8 minues.

BDSC

After looking at this again, I think you would only get 56 minutes and not 58. So an extra 6 minutes.

scubadiver888
November 4th, 2008, 11:12 AM
How does this work? A computer is built on algorithms that determine how much nitrogen has been absorbed into the system and what should have been passed from your system based on the depth and duration (and O2 content of course) of your dive profile. Unless you have more repetitive dives than the group, I do not see how you would have to call a dive due to reaching or approaching your NDL.....the only thing that I can think of that would get you there quicker is a more conservative computer (like mine...a Suunto) but this is minutes not tens of minutes and it is a cumulative effect not immediate. I do agre with you though....talk to people up front and determine which diver best suits your ideal profile for a dive buddy. Sometimes this will work because of the number of solo divers and sometimes it will not. Bottom line is, make sure the pre dive discussion is complete and happens, and make sure the DM knows what your plans are.

I was saying that NOW I end a dive because I approach my NDL. I used to run out of air and have to call the dive early (30 minutes for a 50' dive for example). NOW I almost never call a dive due to air.

I have noticed however that I hit approach NDL before most other people on a dive. Either they are going into deco or my computer is more conservative.

ScubaSteve
November 4th, 2008, 11:20 AM
I was saying that NOW I end a dive because I approach my NDL. I used to run out of air and have to call the dive early (30 minutes for a 50' dive for example). NOW I almost never call a dive due to air.

I have noticed however that I hit approach NDL before most other people on a dive. Either they are going into deco or my computer is more conservative.


OK thanks for the clarification....that makes more sense.

Rick Inman
November 4th, 2008, 12:11 PM
After looking at this again, I think you would only get 56 minutes and not 58. So an extra 6 minutes.
Well, it depends on your sac.

Let's say you breathe a .8 sac. At 66', that would be 2.4cf of gas consumed per min.

At 55' (10' shallower) that would be 2.14cf of gas per min.

At 66' for 30 mins you would breathe 72cf of gas. At 55' you would breathe 64cf of gas. So on this dive, the 10' saves you 8cf of gas, or, approximately 3 mins. A lower sac means less savings.

BDSC
November 4th, 2008, 12:21 PM
Well, it depends on your sac.

Let's say you breathe a .8 sac. At 66', that would be 2.4cf of gas consumed per min.

At 55' (10' shallower) that would be 2.14cf of gas per min.

At 66' for 30 mins you would breathe 72cf of gas. At 55' you would breathe 64cf of gas. So on this dive, the 10' saves you 8cf of gas, or, approximately 3 mins. A lower sac means less savings.

Hey Rick, I'm having a hard time putting faith in your numbers if 55' is 10' less than
66ft. :D

don Francisco
November 4th, 2008, 12:53 PM
Originally Posted by don Francisco
With all due respect, this is a highly unlikely situation, bordering on the "never happen".

Gauges are among our most reliable pieces of equipment, and the risk of one to being off 300-500psi at the low end of the scale is negligible, bordering on zero.........


You might possibly want to call this statement into questioning. I will try to remember who it was and where the thread is (I am drawing a blank...hopefully someone else will recall it) but a well respected member of SB has personal experience of what exactly "acceptable tolerance" is to a computer/gauge manufacturer. This is not my personal experience however I DO have a computer, a tank checker guage and a buddy's console, all with a spread os 250psi from high to low....all different manufacturers but do you think you get to choose which one is accurate before the dive? I am personally going with the conservative one....that way I can dive again.

I stand by my original statement. While gauges have tolerances in their readings and can vary from one another within those tolerances, they should be accurate within 100psi at the critical low end of the range. I also went further in my post offering a simple method for checking the accuracy at that end of the scale.

There are lots of things we have to accept in life, unreliable or inaccurate gauges aren't one of them. If you don't trust your gauge replace it.

psychocabbage
November 4th, 2008, 04:02 PM
Hmmmm.. in Cozumel, when drift diving with the group, when I am done if no one is around me or they are too far, I will call it and head up on my own.. Boat always gets me.. Big sausage helps.. haha

Guess I just dont worry that much and am usually watching the action below me as I drift up.

I went from being 1st up last year to being in the average group that comes up.. My wife (life buddy) doesnt use air.. she seems to be a fish so I dont bring her up with me on the first few dives as she can stay down there forever with her super low sac rate.. To keep her closer to my no fly time, mid week I will bring her up with me..


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