caseybird
Contributor
Storm As to the big debate over the air sharing that seems to be running parallel to this one:
PADI Holds The New World's Record for Fastest OW Class
- Thread starter Web Monkey
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
Storm
Contributor
caseybird:
Agreed.
Just making an observation about human nature. There appears something in our genetic make up, or possibily and deep seeded underlying instinct, that attracts our attention to what could be considered "out of the ordinary"
Just witness a fire scene or traffic accident. They command an almost unnatural presence that causes people to gravitate to them. This is what I am referring to.'
This natural curiosity combined with an inate desire to help each other could lead to divers trying to "get involved". I'm not sayng it right. As to top side explanations. yes they would alleviate this problem, but how many dives sites have you been to where there were multiple boats on tethered to the maker or standiong off nearby?
Anyway, it doesn't matter what we on the board say, some will continue this practice so at least having this discussion will help me to rememebr that I could see this on a dive. So I'll file this in the brain bucket for future situational recognition.
Cheers!
caseybird
Contributor
Storm:
There's nothing wrong with checking if you see something out of line. I've never met a diver that resented it. A simple exchange of the "OK" sign should do the trick.
good diving,
OP
- Messages
- 6,921
- Reaction score
- 25
- # of dives
- I just don't log dives
vkalia:
Almost any dive shop on the planet can get bigger tanks with a little advance notice. If your shop can't, it's got problems.
vkalia:
Divers with poor gas management tend to do just fine, until they don't, at which point they show up in "Accidents and Incidents" or PADI's "Don't Dive Like This Dead Guy" magazine column.
You can ridicule "rule of thirds" all you like, but it works very well in a lot of situations. The bad part is that you tend to return to the boat a little sooner. The good part is that when the **** hits the fan, it becomes a problem-solving exercise, not a panic attack. I'll take that tradeoff any day of the week.
Storm
Contributor
caseybird:
This was what I was saying. Not only are we taught this, but it's also human nature
Web Monkey:
Ah, another magical extrapolation and yet more weird logic.
It is a real shame those dive shops I have visited in Thailand, Indonesia, Zanzibar, Mozambique, Guam and Maldives dont listen to me (or you).
Yep. Sure death.
I didnt ridicule the rule of thirds - I pointed that it is overkill for OW diving.
Sure - sharing air in a controlled situation, with ample air in the receiver's tank, is asking for death. But at the same time, divers are expected to magically be very comfortable sharing air when the compost does hit the fan. That makes a *LOT* of sense.
Thanks a lot for the discussion, or lack thereof, Terry. It stops here on my part - you can have the last repartee.
Vandit
Web Monkey,
I'd like to go back to my example which wasn't responded to. It closely parallels the case of hoover and sipper but is mr doubles with mrs single instead.
I dive 2xLP80's, my partner dives an LP104. We have similar RMV's (around .4 cfm when comfy). During the swim out along the bottom to the dive site I let her breath off my long hose in 20' of water for around 15 minutes. At this point I have appx 140 cf remaining in my tanks and she has appx 100 cf in her tank.
We do our dive and when she hits her ending pressure I have about 30cf / 500 psi more than her. Out LP tanks are full at 2640, so if we use thirds that puts us at 1760 -- that's 70 cf remaning in her tank, pretty silly for a non overhead NDL dive in 60'-70'. Let's use a more thought out emergency ascent plan:
Acent to 15', 2 minutes, average pressure during ascent 3.5 ata = 7 (time * pressure)
Safety stop at 15', 3 minutes, pressure appx 1.5 ata = 4.5
Ascent to surface, 1 minute, average pressure 1.25 = 1.25
Total: 12.75 average pressure * time
Let's assume we're both panicked out of our little brains and breathing at 1cfm each, both off a single tank -- that means we need 2cfm * 12.75, or something around 26 cubic feet of gas.
Ok, so we know that when the compost hits the fan we want to have at least 26 cf left in the tank. On the smaller tank (the single LP104) that's 660 psi. Let's err on the side of caution and start our return at 1000 psi with the agreement that by 800 psi we'd like to be in 30' or shallower. This is reasonably conservative and give us a much more flexible dive than straight rule of 3rds (about 25 minutes more dive time).
The total profile is around 1hr at 60' on 36%.
So let me ask you - what don't you like about this dive plan? How is my partner breathing my emergency gas if my turn pressure remains fixed (at 1000 psi or 3rds or whatever)? How is this going to "kill someone"? How do you view this as being different/similar to the case where mr good rmv donates to mr bad rmv at the start of a dive?
I'd like to go back to my example which wasn't responded to. It closely parallels the case of hoover and sipper but is mr doubles with mrs single instead.
I dive 2xLP80's, my partner dives an LP104. We have similar RMV's (around .4 cfm when comfy). During the swim out along the bottom to the dive site I let her breath off my long hose in 20' of water for around 15 minutes. At this point I have appx 140 cf remaining in my tanks and she has appx 100 cf in her tank.
We do our dive and when she hits her ending pressure I have about 30cf / 500 psi more than her. Out LP tanks are full at 2640, so if we use thirds that puts us at 1760 -- that's 70 cf remaning in her tank, pretty silly for a non overhead NDL dive in 60'-70'. Let's use a more thought out emergency ascent plan:
Acent to 15', 2 minutes, average pressure during ascent 3.5 ata = 7 (time * pressure)
Safety stop at 15', 3 minutes, pressure appx 1.5 ata = 4.5
Ascent to surface, 1 minute, average pressure 1.25 = 1.25
Total: 12.75 average pressure * time
Let's assume we're both panicked out of our little brains and breathing at 1cfm each, both off a single tank -- that means we need 2cfm * 12.75, or something around 26 cubic feet of gas.
Ok, so we know that when the compost hits the fan we want to have at least 26 cf left in the tank. On the smaller tank (the single LP104) that's 660 psi. Let's err on the side of caution and start our return at 1000 psi with the agreement that by 800 psi we'd like to be in 30' or shallower. This is reasonably conservative and give us a much more flexible dive than straight rule of 3rds (about 25 minutes more dive time).
The total profile is around 1hr at 60' on 36%.
So let me ask you - what don't you like about this dive plan? How is my partner breathing my emergency gas if my turn pressure remains fixed (at 1000 psi or 3rds or whatever)? How is this going to "kill someone"? How do you view this as being different/similar to the case where mr good rmv donates to mr bad rmv at the start of a dive?
Air sharing...
Provided both divers reserve an adequate bailout/rockbottom or whatever you want to call it, I don't see any problem with sharing air in nonemergency situations. How is it different from just practicing air sharing? We do it all the time mostly clowning around and practicing but each still reserves enough that the dive could be ended with each diver on their own tank or both on one. If other divers freak because they never saw such a thing then it's time they get up to speed and the experience will probably do them good.
Dive training...
Some of you instructors keep quoting standards but I wonder how well you've read them. It's not a matter of what skills have been dropped from training but which ones were never required in the first place. A few examples...gas management, finning technique, static and dynamic trim, buddy skills during a real dive and usually no skills are taught off the bottom other than a silly one minute hover in any convoluted position.
Further, standards (such as PADI's) do not require that a student do a good job of diving during the OW dives. Standards allow them to pass if they pretty much wallow around in the bottom through the whole 20 minute dive. All they need to do is pull off doing the silly skills on their knees and they're home free. Savy shops that certify lots of divers are very good at knowing exactly what they aren't required to do and not doing it. Diving is taught as though the bc was just invented and not fully integrated into training yet.
Taking it a step further, none of this stuff is taught or required to be demonstrated even at the DM or instructor level. With so many of the instructors being fast trackers put out by the same system, they often have the very same skill deficiencies.
Want proof? Don't look at the death toll because most people can drop down, crawl around the bottom for a while and climb back out without getting killed and they can do it with no training at all. Survival alone is not proof of good training unless you compare it to a control group who gets killed without that same training. LOL. The exhibition of good skills in the water by new divers is proof of good training but you don't see much of that do you? Instead (as an example) look at the number of divers who come on this board looking for help trying to figure out how to weight themselves properly. If real control in the water was being taught such questions wouldn't be asked. The weighting thing is just one example but there are many others. Shoot folks just look at divers in the water.
You can argue that enough is taught to keep most divers alive but that's about all. At the very least it sure makes a mess out of our dive sites and at worst it does get a few folks killed. I know I've done my share with inwater rescues and directing traffic for ambulances at local dive sites. If that's what we're after then I guess we have it.
Provided both divers reserve an adequate bailout/rockbottom or whatever you want to call it, I don't see any problem with sharing air in nonemergency situations. How is it different from just practicing air sharing? We do it all the time mostly clowning around and practicing but each still reserves enough that the dive could be ended with each diver on their own tank or both on one. If other divers freak because they never saw such a thing then it's time they get up to speed and the experience will probably do them good.
Dive training...
Some of you instructors keep quoting standards but I wonder how well you've read them. It's not a matter of what skills have been dropped from training but which ones were never required in the first place. A few examples...gas management, finning technique, static and dynamic trim, buddy skills during a real dive and usually no skills are taught off the bottom other than a silly one minute hover in any convoluted position.
Further, standards (such as PADI's) do not require that a student do a good job of diving during the OW dives. Standards allow them to pass if they pretty much wallow around in the bottom through the whole 20 minute dive. All they need to do is pull off doing the silly skills on their knees and they're home free. Savy shops that certify lots of divers are very good at knowing exactly what they aren't required to do and not doing it. Diving is taught as though the bc was just invented and not fully integrated into training yet.
Taking it a step further, none of this stuff is taught or required to be demonstrated even at the DM or instructor level. With so many of the instructors being fast trackers put out by the same system, they often have the very same skill deficiencies.
Want proof? Don't look at the death toll because most people can drop down, crawl around the bottom for a while and climb back out without getting killed and they can do it with no training at all. Survival alone is not proof of good training unless you compare it to a control group who gets killed without that same training. LOL. The exhibition of good skills in the water by new divers is proof of good training but you don't see much of that do you? Instead (as an example) look at the number of divers who come on this board looking for help trying to figure out how to weight themselves properly. If real control in the water was being taught such questions wouldn't be asked. The weighting thing is just one example but there are many others. Shoot folks just look at divers in the water.
You can argue that enough is taught to keep most divers alive but that's about all. At the very least it sure makes a mess out of our dive sites and at worst it does get a few folks killed. I know I've done my share with inwater rescues and directing traffic for ambulances at local dive sites. If that's what we're after then I guess we have it.
OP
- Messages
- 6,921
- Reaction score
- 25
- # of dives
- I just don't log dives
The original example assumed equal size tanks for both divers.
If the doner has a much larger tank than the hoover, it's a different story (although I'd probably still not do it in front of students)
Terry
If the doner has a much larger tank than the hoover, it's a different story (although I'd probably still not do it in front of students)
Terry
Atticus:
Web Monkey, thank you for the response.
Can you help me understand what the difference is between the two scenarios? In one case I have a larger tank and in the other case I have a better RMV. In either case I'm keeping the save reserve in cubic feet for emergencies.
If the goal is to have a given bottom time and a sufficient reserve when that bottom time is up, why does it matter how we get there?
Mike - you make some very good points about comfort/ability in the water vs. skill demonstration. How would you suggest an agency word their standards such that an instructor following that agencies rules would "have to" produce better divers? I think a lot of recreational instructors believe they are following their agencies standards and feel they are wrong if they require more (specifically I'm referring to some of the PADI threads discussing instructor reprimands for not granting certification despite a student having done the required skill demonstrations). Please don't take this as a PADI bash - that is simply the most direct example I could think of.
I pretty much only teach private classes now after a couple of years of doing the C-card mill thing. With my classes now I keep diving with the students after they've finished their skill demonstrations. In many cases they've met the requirements for higher level certifications before they start diving on their own. This happens because the people I train become my friends and dive partners and we end up enjoying the hobby together. This isn't the kind of thing you can put into a standards document though.
Can you help me understand what the difference is between the two scenarios? In one case I have a larger tank and in the other case I have a better RMV. In either case I'm keeping the save reserve in cubic feet for emergencies.
If the goal is to have a given bottom time and a sufficient reserve when that bottom time is up, why does it matter how we get there?
Mike - you make some very good points about comfort/ability in the water vs. skill demonstration. How would you suggest an agency word their standards such that an instructor following that agencies rules would "have to" produce better divers? I think a lot of recreational instructors believe they are following their agencies standards and feel they are wrong if they require more (specifically I'm referring to some of the PADI threads discussing instructor reprimands for not granting certification despite a student having done the required skill demonstrations). Please don't take this as a PADI bash - that is simply the most direct example I could think of.
I pretty much only teach private classes now after a couple of years of doing the C-card mill thing. With my classes now I keep diving with the students after they've finished their skill demonstrations. In many cases they've met the requirements for higher level certifications before they start diving on their own. This happens because the people I train become my friends and dive partners and we end up enjoying the hobby together. This isn't the kind of thing you can put into a standards document though.
Similar threads
