 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| HomeArticlesDiving DestinationsLearning Scuba DivingMarine LifeMiscellaneousDiscussion GroupsGeneralScuba EquipmentScuba LocationsAustralian ScubaUK ScubaDirectoryScuba Clubs |
Scuba Forum / General / May 2006Article in March 2006 issue of Scuba Diving
Was wondering what opinions people had about the article in March 2006 issue of Scuba Diving, page 83, "The Final Ascent". The point the author makes is that "the trickiest part of your dive might come after the safety stop". Being a relative newbie I certainly have to defer to the author but there was a sense I had that there may have been a bit of overstating certain "potential" problems. Was wondering what you more experienced folks thought. Sy  SignaturePlease post and reply to sytech@yahoo.com > Was wondering what opinions people had about the article in March 2006 > issue of Scuba Diving, page 83, "The Final Ascent". [quoted text clipped - 7 lines] > > Sy biggest pressure change >> Was wondering what opinions people had about the article in March 2006 >> issue of Scuba Diving, page 83, "The Final Ascent". [quoted text clipped - 9 lines] >> > biggest pressure change Didn't see the article, but I can guess... When you ascend from, say, 99 fsw to 66 fsw the pressure change is from about 59 psi to about 44 psi, a one-quarter reduction which will result in a 25% expansion of the air in yer lungs. But when you ascend from, say, 33 fsw to the surface the pressure change is from about 29.4 psi to about 14.7 psi and the halving of pressure will double the volume of air in yer lungs in the same 33 feet of ascent. Just like English says. Most new divers lack the buoyancy control to make a very slow, controlled ascent from shallow depths (remember that the volume of air in yer BC also doubles from 33 fsw to the surface!) and risk all kinds of nastiness of the lungs and ears by popping to the surface. I start my safety stop at 20' and ascend about 3'/minute to 10'. From 10' it takes me about two minutes to reach the surface. Learn to do that and you will avoid lung expansion problems and greatly improve yer overall buoyancy control. m > I start my safety stop at 20' and ascend about 3'/minute to 10'. From > 10' it takes me about two minutes to reach the surface. Learn to do that > and you will avoid lung expansion problems and greatly improve yer > overall buoyancy control. And I thought I was slow! But I do basically the same as you Mike. I have been for years. > When you ascend from, say, 99 fsw to 66 fsw the pressure change > is from about 59 psi to about 44 psi, a one-quarter reduction [quoted text clipped - 4 lines] > halving of pressure will double the volume of air in yer lungs > in the same 33 feet of ascent. Good grief... isnt life so much easier with "1 bar every 10m", as opposed to "14.7psi every 33 ft"? Am sending an OW student down your way to Splashdown, btw. If someone is there, asking for you to learn more about DIR, blame me for that :) V. >>When you ascend from, say, 99 fsw to 66 fsw the pressure change >>is from about 59 psi to about 44 psi, a one-quarter reduction [quoted text clipped - 7 lines] > Good grief... isnt life so much easier with "1 bar every 10m", as > opposed to "14.7psi every 33 ft"? No. I can figger out in my head that it's 29.4 psi every 66 feet, but what the hell is it at 2 bar? This is America! Speak American! > Am sending an OW student down your way to Splashdown, btw. If someone > is there, asking for you to learn more about DIR, blame me for that :) I don't dive Splashdown any more. > No. I can figger out in my head that it's 29.4 psi every 66 > feet, but what the hell is it at 2 bar? Some comedian was going on about how single-minded the Chinese must be. His argument was that they *had* seen shovels and pitchforks and so, despite having realized the potential for a more effective eating utensil, the fact that they stuck with chopsticks implied a certain fixednes of purpose. The Chinese, OTOH, claim that learning to use chopsticks as a child helps develop not only physical dexterity but develops the brain (probably through better motor skill development). This is the scuba/US equivalent of chopsticks. My peanut brain cannot handle all that stuff. > I don't dive Splashdown any more. Going for those 30-diver cattleboats, are you? Easier to meet chicks there, though, I reckon.... my biggest complaint about diving with you and Lee those years back was that neither of you is a hot, large-breasted young lady... atleast, neither of you were back then. V. > Going for those 30-diver cattleboats, are you? Easier to meet chicks > there, though, I reckon.... Six pack. The Explorer, mostly my biggest complaint about diving with you > and Lee those years back was that neither of you is a hot, > large-breasted young lady... atleast, neither of you were back then. This is Boca Raton. I can easily have that fixed. > > No. I can figger out in my head that it's 29.4 psi every 66 > > feet, but what the hell is it at 2 bar? [quoted text clipped - 8 lines] > helps develop not only physical dexterity but develops the brain > (probably through better motor skill development). I did the exact same thing with video games. That being said, I use chopsticks when eating oriental food because it tastes better that way. :-) > I did the exact same thing with video games. I tried that line with my mum, and got cuffed upside the head for my attempts. > That being said, I use chopsticks when eating oriental food because it > tastes better that way. :-) Try using your chopsticks as a spear.... that bit of cultural sensitivity really goes over well. Bonus points for leaving them sticking in a bowl of sticky rice :) Spreading love and peace the world over, Brother Vandit > Bonus points for leaving them > sticking in a bowl of sticky rice :) Something about them doing that as an offering to the dead, at a grave, or something like that from what I remember... Telling them that you're just trying to get better reception on the TV doesn't quite go over that well... mike gray a écrit : > > Good grief... isnt life so much easier with "1 bar every 10m", as > > opposed to "14.7psi every 33 ft"? [quoted text clipped - 3 lines] > > This is America! Speak American! Tell that to the NASA engeeners about Mars Climate Orbiter ... ;-) Benoît, who use Metric system ... > mike gray a écrit : > > [quoted text clipped - 9 lines] > > Benoît, who use Metric system ... There were lots of other problems on that mission, besides just the units. IEEE Spectrum had a nice article on it a few years back Dennis >> When you ascend from, say, 99 fsw to 66 fsw the pressure change >> is from about 59 psi to about 44 psi, a one-quarter reduction [quoted text clipped - 7 lines] >Good grief... isnt life so much easier with "1 bar every 10m", as >opposed to "14.7psi every 33 ft"? Hell, on 6th Street here in Austin it seems like there's a bar every 10 feet. >Am sending an OW student down your way to Splashdown, btw. If someone >is there, asking for you to learn more about DIR, blame me for that :) > >V. Signaturedillon I didn't climb to the top of the food chain to become a vegetarian. > >> When you ascend from, say, 99 fsw to 66 fsw the pressure change > >> is from about 59 psi to about 44 psi, a one-quarter reduction [quoted text clipped - 10 lines] > Hell, on 6th Street here in Austin it seems like there's a bar every > 10 feet. That translates to 1 bar every 3 meters which is high for scuba purposes, but just about right for a college town. >> Was wondering what opinions people had about the article in March 2006 >> issue of Scuba Diving, page 83, "The Final Ascent". [quoted text clipped - 9 lines] >> > biggest pressure change Biggest PERCENTAGE pressure change. Pressure change, in absolute ATM, is same from 100 to 85 as it is from 15 to 0 fsw. According to the BASOD agency, you should bolt as quick as possible from your last safety stop to the boat deck, so you'll be the first grabbing a beer from the cooler. > The point the author makes is that "the trickiest part of your dive > might come after the safety stop". Being a relative newbie I > certainly have to defer to the author but there was a sense I had that > there may have been a bit of overstating certain "potential" problems. > Was wondering what you more experienced folks thought. The closer you get to the surface, the greater the volume change for each incremental change in pressure. You are at your greatest risk of embolism as you approach the surface, i. e. after your safety stop. Lee <sytech@yahoo.com> pounded away at his keyboard resulting in: :Was wondering what opinions people had about the article in March 2006 :issue of Scuba Diving, page 83, "The Final Ascent". [quoted text clipped - 5 lines] : :Was wondering what you more experienced folks thought. I didn't read the article. If the author said words to the effect of "the reason the final 15 or so ft of your ascent is riskiest is because that is when the air in your body expands by the greatest percentage", I agree. Dan Bracuk If we don't succeed, we run the risk of failure. <sytech@yahoo.com> pounded away at his keyboard resulting in: :Was wondering what opinions people had about the article in March 2006 :issue of Scuba Diving, page 83, "The Final Ascent". [quoted text clipped - 5 lines] : :Was wondering what you more experienced folks thought. Now that you have heard so many people say almost the same thing, what was the part in the article that you considered overstated. Remember, most of us didn't read it. Dan Bracuk If we don't succeed, we run the risk of failure. Dan, I don't have the article handy but it just "seemed" that maybe the author's emphasis on "theroretical" problems might have been overstated but I've heard enough here to get the point. Towards the end of the article the author advocated that because of all these" theoretical" problems that could develop, it's probably not a good idea for many people to board the boat with all that heavy gear on because the effort required could excerbate any nitrogen retension issues that may be at play. Any thoughts on that? Sy > Towards the end of the article the author advocated that because of all > these" theoretical" problems that could develop, it's probably not a [quoted text clipped - 3 lines] > > Any thoughts on that? Strenuous exercise is believed to exacerbate the potential for DCS problems. I guess it all depends on your nitrogen status at the time and how strenuous a climb back on to the boat is for you. By the way, retention isn't the issue. Release is. Lee sytech@yahoo.com pounded away at his keyboard resulting in: :Towards the end of the article the author advocated that because of all :these" theoretical" problems that could develop, it's probably not a [quoted text clipped - 3 lines] : :Any thoughts on that? That's overstated to say the least. Coming out of the water with or with your rig depends largely on the boat. In the case of a zodiac, you pretty well have to doff your rig or you simply won't be able to pull yourself up. It's hard enough as it is without gear. At the other extreme, are liveaboard with very nice ladders at the back. In these cases, doffing your gear in the water takes more energy than climbing the ladder with it on. Dan Bracuk If we don't succeed, we run the risk of failure. >Dan, > [quoted text clipped - 11 lines] > >Sy Sy, First off .. the most important rule in scuba diving is breathe continuosly and Never hold your breath. After your saftey stop ... ascend slowly ... if your going faster then your bubbles ..slow down ... this is not a race ... when you reach the surface ... inflate and relax ... don't stress . ... PADI / MSDT kind regards & best fishes > First off .. the most important rule in scuba diving is breathe > continuosly and Never hold your breath. Never? How else do you hold perfectly still to take a photo? > After your saftey stop ... ascend slowly ... if your going faster then > your > bubbles ..slow down ... this is not > a race ... when you reach the surface ... inflate and relax ... don't > stress . Why not stress? On the surface is where you're most likely to get bitten by a shark, run over by a boat, or entangled in a mass of jellies or bluebottles. >> First off .. the most important rule in scuba diving is breathe >> continuosly and Never hold your breath. [quoted text clipped - 10 lines] >a shark, run over by a boat, or entangled in a mass of jellies or >bluebottles. NOT TRUE. I was a good six inches underwater when I ran into the jelly. Signaturedillon I didn't climb to the top of the food chain to become a vegetartian. >Dan, > >I don't have the article handy but it just "seemed" that maybe the >author's emphasis on "theroretical" problems might have been overstated >but I've heard enough here to get the point. I want to live in Theory. Everything works in Theory. >Towards the end of the article the author advocated that because of all >these" theoretical" problems that could develop, it's probably not a >good idea for many people to board the boat with all that heavy gear on >because the effort required could excerbate any nitrogen retension >issues that may be at play. The amount of exertion is minimal. I wouldn't do those 100 pushups immediately aftwards, but climbing out of the water certainly won't do anything to most people who were at least a little concious of their nitrogen loading. And the others are going to get hit one way or another anyways. >Any thoughts on that? Be aware of your nitrogen. As a newbie, I'd recommend diving well within the tables. More room for error when you do screw up, and you will. >Sy Signaturedillon I didn't climb to the top of the food chain to become a vegetartian. > Was wondering what opinions people had about the article in March 2006 > issue of Scuba Diving, page 83, "The Final Ascent". [quoted text clipped - 10 lines] > -- > Please post and reply to sytech@yahoo.com I didn't read the article but I do know that it is easier to get hit in the head by the boat at 5 feet than at 50.... OW! Theoretically all dive have almost all dives have a degree of nitroigen supersaturation. With any degree of supersaturation there is always a risk of bubble nucleation. The dive tables are based on what chance there is of a large bubble nucleation. Being on safe time does not mean no bend. However in safe time means the risk of nucleation of a bubble and the size of the bubble are PROBABLY within an acceptable limit. One of the biggest risks to bubble nucleation is a fall or bump after getting out of the water. Think of the bang on the side of a bottle of coke. The effect of a bend depends where the bubble forms. In muscle tissue leave it any decompression risks the bubble moving to a more sensitive area. Better to be live with a small numb dead spot of muscle than a cerebal bend. Bob M >One of the biggest risks to bubble nucleation is a fall or bump after >getting out of the water. Think of the bang on the side of a bottle of >coke. sh.t! I never thought of that. Not much chance of avoiding that on a thirty or more mile return to port in rough water. > The point the author makes is that "the trickiest part of your dive > might come after the safety stop". In theory yes - as the biggest pressure gradient occurs in the shallowest few meters. That being said, I dont think too many people are getting bent coming up a bit too fast from 5m to the surface.. not on a single tank rec dive, anyway. So calling it the "trickiest part of the dive" is, IMO, overstating it - atleast by implication. Vandit >> The point the author makes is that "the trickiest part of your dive >> might come after the safety stop". [quoted text clipped - 4 lines] > That being said, I dont think too many people are getting bent coming > up a bit too fast from 5m to the surface.. to me, bent is a long term effect. the short fast ascent will not produce N2 effects, but rather pressure effects,like pnemothorax, Respiratory barotrauma, Air Embolism, Mediastinal Emphysema, > Vandit > the short fast ascent will not produce N2 effects, > but rather pressure effects,like pnemothorax, > Respiratory barotrauma, Air Embolism, Mediastinal Emphysema, Again, I agree with the theoretical risk. I simply dont see people coming up so fast from their safety stop that they risk barotrauma. Even from 5m, you'd have to hurtle like mad for this to happen. So possible - yes. Likely - no. For me, this falls in the category of "dont climb onto the boat with your own tanks" or whatever... the theory is fine, but odds of anyone staying within their NDLs on a single tank and pretzeling themselves doing this are probably lower than the odds of being molested by an amorous dolphin. I guess my problem is not so much in the concept being pointed out - I actually make it a point to tell my OW students to come up slowly in the last 5m (used to be on the old PADI OW exams as well - not in the newer editions, though) - but in the way it *appears* to have been presented (keep in mind, I havent read the article - if it is balanced piece, mea culpa and apologies). Vandit |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.