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Scuba Forum / General / September 2007Buoyancy problems at shallow depths
Well, I got enough decent equipment to dive in the pool, which is only 12 feet deep. When I was having buoyancy problems during my pool certification many of you told me my problems were due to the fact that I was too shallow. You were right, because as I moved to my OW certification, and got down around 30 feet, it was much easier to move up and down and around. In the pool sessions I was wearing 6 lbs of weight, and during exercises where we had to kneel on the bottom I had problems "sticking" to the bottom. During my OW certification my instructor started me with 6 and the second day went to 8. Once down I was able to swim all over the place with no air in my BC -- in around under and through lot's of obstacles. I'm now back in the pool with 8 lbs of weight, working on buoyancy and just swimming around down there. What I've been trying to do is stay in a lane and swim down to the deep end and back up to the shallow end, trying to stay a foot off the bottom the whole way. When swimming up I have to add air to my BC or don't rise to the occasion, as you might put it. When swimming towards the deep end I have to dump air or I can't get down. Still hard to hold that one foot distance all the way. I have been able to dial in just enough air in my BC to remain completely suspended between the top and bottom of the pool, which was very cool. Wondering if I should hold that and take it from there. So my question is, am I still dealing with the problems you described before because I'm not deep enough? During my OW cert I was very surprised I could go up, down and all around with an empty BC, yet in the pool a touch on either button has quite an effect on my buoyancy. Yet, the 8 lbs does allow me to sit, kneel, or whatever I want to do at the bottom and remain very stable and balanced. If it makes any difference I got a used steel tank (fully tested, inspected and stickered). The BC is in extremely good shape, valves work well and it holds air no problem. Nice, easy breathing regulator, but still needs to be serviced. Any comments? Questions? Tips? Thanks again. >(snip)> stable and balanced. If it makes any difference I got a used steel tank > (fully tested, inspected and stickered). Are you diving that steel tank on these pool sessions you are telling us about here? >>(snip)> stable and balanced. If it makes any difference I got a used >>steel [quoted text clipped - 3 lines] > Are you diving that steel tank on these pool sessions you are telling us > about here? Yes! I was told the only real difference it would make is 1. It won't hold as much air, and 2. A steel tank will hold it's buoyancy as it empties, whereas an aluminum tank will start to become more buoyant. Keep in mind the lowest I can go in the pool is 12 ft. If I plan a trip I will be renting a tank. >> Are you diving that steel tank on these pool sessions you are telling us >> about here? [quoted text clipped - 4 lines] > in mind the lowest I can go in the pool is 12 ft. If I plan a trip I will > be renting a tank. You need to find somebody else to talk to about these things. You're getting bad information. 1. Steel tanks are not normally the same buoyancy as aluminum ones. Mine are significant less buoyant. 2. All tanks, no matter what the material, change buoyancy exactly the same as you remove gas from them by breathing. Lee "Sheldon" <sheldon@XXXXXXXXsopris.net> pounded away at his keyboard resulting in: :Yes! I was told the only real difference it would make is 1. It won't hold :as much air, and 2. A steel tank will hold it's buoyancy as it empties, :whereas an aluminum tank will start to become more buoyant. Keep in mind :the lowest I can go in the pool is 12 ft. If I plan a trip I will be :renting a tank. The amount of air a tank holds depends on it's size, not the metal it's made of. Any tank will become less bouyant as you breathe air out of it. You are attempting something too precise to be realistic. Oour bouyancy changes everytime we inhale or exhale. Dan Bracuk Never use a big word when a diminutive one will do. > "Sheldon" <sheldon@XXXXXXXXsopris.net> pounded away at his keyboard > resulting in: [quoted text clipped - 7 lines] > it's made of. Any tank will become less bouyant as you breathe air > out of it. I think you meant "more" bouyant. > You are attempting something too precise to be realistic. Oour > bouyancy changes everytime we inhale or exhale. [quoted text clipped - 5 lines] > http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups > ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- "chilly" <slarson@shaw.canada> pounded away at his keyboard resulting in: :I think you meant "more" bouyant. So do I. Dan Bracuk Never use a big word when a diminutive one will do. > "chilly" <slarson@shaw.canada> pounded away at his keyboard resulting > in: [quoted text clipped - 4 lines] > > Dan Bracuk Also, the steel tank is only rated to 2200 compared to most aluminum tanks. And yes, it's a full size tank. > Also, the steel tank is only rated to 2200 compared to most aluminum > tanks. And yes, it's a full size tank. All tanks are full sized tanks. What's important is which full size they are. I have a couple of full sized 30 cubic foot tanks, a bunch of full sized 80 cubic foot tanks and a couple of full sized 100 foot tanks. Some people here have full sized tanks smaller and bitter still. In the US, tanks are identified by the amount of gas they hold at their rated pressure if the gas were expanded to 1 atmosphere pressure. An 80 cubic foot tanks rated for 2200 psi, holds the same amount as an 80 cubic foot tank rated for 3000 psi or one rated for 3500 psi. The buoyancy change per cubic foot of gas is also the same. Since you breathe volume, not psi, it's the change in volume that affects your buoyancy, even if the psi changes at a different rate. Lee > In the US, tanks are identified by the amount of gas they hold at their > rated pressure if the gas were expanded to 1 atmosphere pressure. An 80 > cubic foot tanks rated for 2200 psi, holds the same amount as an 80 cubic > foot tank rated for 3000 psi or one rated for 3500 psi. Not to complicate things, but I thought 80 cf tanks rated for 2,200 psi only hold the same amount as an 80 cubic tank rated for 3000 psi if they're pumped to 2,420 psi? >> Also, the steel tank is only rated to 2200 compared to most aluminum >> tanks. And yes, it's a full size tank. [quoted text clipped - 13 lines] > > Lee Now I'm confused. Are you telling me that an 80 cubic foot steel tank rated at 2200 holds the same amount of air as an aluminum 80 cubic foot tank rated at 3500 psi.? Or maybe a better way to put it is do they hold the same amount of breaths? I understand the "full size" thing. I should have been more specific. > Now I'm confused. Are you telling me that an 80 cubic foot steel tank rated > at 2200 holds the same amount of air as an aluminum 80 cubic foot tank rated > at 3500 psi.? Where do you find an aluminum 80 cf tank rated at 3500 psi? In rec.scuba, on Sun 09 Sep 2007 08:39:07p, Greg Mossman <mossman@qnet.com> wrote: > Where do you find an aluminum 80 cf tank rated at 3500 psi? The most I've seen is 3300 psi. Close, but not quite. I wouldn't be surprised if they weren't often filled to 3500 psi, but then again, so AL80s get filled to 3500 psi also. In rec.scuba, on Sun 09 Sep 2007 07:37:53p, "Sheldon" <sheldon@XXXXXXXXsopris.net> wrote: > Now I'm confused. Are you telling me that an 80 cubic foot steel tank > rated at 2200 holds the same amount of air as an aluminum 80 cubic > foot tank rated at 3500 psi.? Or maybe a better way to put it is do > they hold the same amount of breaths? If it is rated at 80 cu-ft, it hold 80 cu-ft regardless of what the rated pressure is for the tank. OK, I'm kind of glossing over the issue of some 80 cu-ft tanks not being really a full 80 cu-ft, but that's more of a deceptive advertising issue than anything else. The most common steel tank is a 72 cu-ft tank. They pretty damn close to neutral when empty, IIRC. Once you add a regulator to them, they're probably always negative. I don't have the figures in front of me at this time, but I'm sure someone will quickly correct me if I'm wrong. One advantage of the steel 72 cu-ft tanks is that since they are low pressure, you're more likely to be able to get a full fill (if not even more than 'full') than is likely to happen with an AL80. One issue that might want to be aware of though is that if you turn the dive at 500 psi, you're leaving a higher percentage of air in your tank with the steel 72 than you are with the AL80. With 500 psi left in a steel 72, you've got 16.7 cu-ft (assuming a 2150 psi pressure rating). With 500 psi left in an AL80, you've got 13.3 cu-ft (assuming a 3000 psi pressure rating). To end up with the equivalent 13.3 cu-ft left in a steel 72 tank, you should adjust your turning point psi to approximately 400 psi. The steel 72s seem to last a long time. You would be hard pressed to find a 35 year old aluminum tank still in service, but 35 year old steel tanks are still rather common. New steel tanks might cost a bit more than their aluminum counterparts, but once you factor in the cost of the more expensive VIP+ inspections for the aluminum tanks, the steel tanks will pay for themselves within 15 years, IIRC. 30 years down the road, you're steel tank is still good, whereas I'm not so certain about a 30 year old aluminum tank. I own aluminums and steels, so I dont' think that I'm overly biased one way or the other. > In rec.scuba, on Sun 09 Sep 2007 07:37:53p, "Sheldon" > <sheldon@XXXXXXXXsopris.net> wrote: [quoted text clipped - 38 lines] > tank. I own aluminums and steels, so I dont' think that I'm overly biased > one way or the other. I may have a handle on this now. The last time I dove in the crater I was using aluminum tanks. According to the info I just researched on the Net, you need more weight when diving with an aluminum tank than a steel tank, especially towards the end of your dive as aluminum tanks become more buoyant when they empty. Steel tanks remain less buoyant. So, on my last certification dive I added weight to 8 lbs and was fine. Now, using a steel tank, I assumed I should use 8 lbs, but with this new information, and my experience along with your advice, I need to trim back to 6 lbs and actually test it in the water. As my instructor was teaching me in the crater, I need to swim down, not get dragged down by extra weight or use my bc to control all my buoyancy.. As I get deeper and things compress, I'll naturally lose buoyancy. Excuse me for wanting to understand everything down to the last molecule of knowledge, but I learn best when I understand how things work. Thanks again. [some previous parts of this thread deleted for brevity] > I may have a handle on this now. The last time I dove in the crater > I was [quoted text clipped - 3 lines] > tanks become more > buoyant when they empty. Steel tanks remain less buoyant. Actually that is not absolutely correct. 100 CuFt of air weighs around 8.25 pounds at Standard temperature and pressure (20 deg C and Sea Level air pressure) If your cylinder holds 80 CuFt multiply the above number by 0.8. The important point of all of this for me is that you get more buoyant during a dive, no matter what sort of kit you are using. (Well maybe not as much with a rebreather since you only actually use the oxygen and the CO2 gets chemically absorbed. But this is rec.scuba in any case.) The method of getting neutral at the surface at the start of a dive simply does not work in the long run. Worse still, the time when it is most likely to let you down is when you are trying to hold a safety stop at the end of a dive. It's better to go into the water with a nearly empty cylinder (I'd do it on something around the 50 bar mark. (750 psi more or less) Once you are in the water at a depth around 3 - 5 metres empty your BC and then try to fin pivot. Remove lead until you do fin pivot or hover. Make a note of the kit you were using and the lead you used. If you change kit, do it again, otherwise you should be right for future times when you are using your own kit.) By the way, this is one of the best reasons for owning your own dive kit. (IMHO, of course.) This is heaps easier in metric. We measure our cylinder volume in litres and pressure in bar (1 bar = (more or less) one ATA atmosphere absolute pressure) And air has a mass of 1.3 grams per litre. Too bad the US never got around to implementing the line in the Constitution that called for the creation of a decimal system of weights and measures. (And no, that is not intended as flame-bait I live in Melbourne, Victoria, Australia, but I am both a US citizen and an Aussie.) I studied the US Constitution in High School in Lancaster, PA. And, as far as the cylinder discussions go, we seem to get much higher pressure kit here. My preferred pair of manifolded twins run at 300 bar - about 4500psi - and my LDS fills them to full pressure. My other steel cylinders are rated at 3500psi and I've got a couple of Aluminium cylinders that are *only* rated at about 3100psi. > So, on my last certification dive I added weight to 8 lbs and was > fine. Now, using a steel tank, I assumed I should use 8 lbs, but [quoted text clipped - 3 lines] > teaching me in the crater, I need to swim down, not get dragged down > by extra weight Yes, there is some truth in this, particularly in shallow water. If you need to put gas in your BC to get neutral at 6-9 ft then you are likely to find maintaining neutral buoyancy more difficult. To explain, I'm going to use metric units just because they're simpler. This is doing some rounding, but for the discussion I am using the assumption that 10 metres salt water is equivalent to one atmosphere of pressure. (It actually is close enough that this stuff works near enough for practical purposes.) If you are at 10 metres and have 10 litres of gas in a BC and you move down to 12 metres you will then have 9.1 litres in the BC. If you moved up to 8 metres you'd have 11.1 litres. If you are at 20 metres and have 10 litres of gas in a BC and you move down to 22 metres you will then have 9.4 litres in the BC. If you moved up to 18 metres you'd have 10.7 litres. Think of a litre as having about 2.2 pounds of lift (it's really 2.24 but that sort of precision is not worth the trouble.) The important point is that there is not a lot of change with a 2 metre (around 6'8") depth change. BUT, let's look at 3 metres. BC with 10 litres at 3 metres - move to 5 metres - 8.6 litres and if you moved from 3 metres to 1 metre there would be 11.8 litres in the BC, an additional lift of nearly 4 pounds -- it's enough to force you to the surface, particularly since you'd have 13 litres of gas in the BC at the surface - about 7 pounds of extra lift. The less gas you need in the BC, particularly in shallow water, the less trouble you will have holding your depth. > or use my bc to control all my buoyancy.. As I get deeper and > things compress, I'll naturally lose buoyancy. > > Excuse me for wanting to understand everything down to the last > molecule of knowledge, but I learn best when I understand how things > work. It took me a longish time to get my head around this stuff. The simplest thing to do would be to make a graph of pressure versus volume in a spreadsheet program and look how much more rapidly it changes in the first 10 metres (33 feet) compared to the latter 33 foot changes. For what it is worth, that's also why ascending the last 5 metres of a dive should be the slowest part of the ascent. If you can take a minute or more for this last little bit, you will be diving safer. Think of it as taking the top of a soft drink bottle and doing it slowly as opposed to opening it quickly - which way do you see more bubbles? Since this can be a contentious issue, I won't be surprised to see some disagreement with my comments. But, as they say, YMMV. Good luck with the diving. -Don > Actually that is not absolutely correct. 100 CuFt of air weighs > around 8.25 pounds at Standard temperature and pressure (20 deg C > and Sea Level air pressure) If your cylinder holds 80 CuFt multiply > the above number by 0.8. See how things can get confused? 100 cubic feet of gas, when contained in a scuba cylinder, weight the same no matter what the ambient pressure or temperature is. > The important point of all of this for me is that you get more > buoyant during a dive, no matter what sort of kit you are using. Yep. > (Well maybe not as much with a rebreather since you only actually > use the oxygen and the CO2 gets chemically absorbed. Don't go there. He needs to understand open circuit first. > This is heaps easier in metric. We measure our cylinder volume in > litres and pressure in bar (1 bar = (more or less) one ATA atmosphere > absolute pressure). It is not easier in metric. In our system, an 80 cubic foot tank, at its rated pressure, holds 80 cubic feet of gas. How many liters are in an 11 liter tank at its rated pressure? The close relationship between depth and BAR is easier, but that's a different issue. By the way, 14.5 psi (BAR) versus 14.7 psi, is enough of a difference to matter when you're talking hundreds of BAR. Discussing them like they are the same is a convenience much like assuming a meter is about the same as a yard. It's fine as long as you know it's not quite true. >In metric, the size of the And air has a mass of 1.3 grams per litre. That's a different use of liter and does not translate to the way liter is used when describing the tank. The weight of gas in a 11 liter tank is much different when filled to 232 BAR than it is when filled to 300 BAR. In rec.scuba, on Sun 09 Sep 2007 11:30:48p, Don Gingrich <gingrich@gmail.com> wrote: > And, as far as the cylinder discussions go, we seem to get > much higher pressure kit here. My preferred pair of manifolded > twins run at 300 bar - about 4500psi - and my LDS fills them > to full pressure. My other steel cylinders are rated at 3500psi > and I've got a couple of Aluminium cylinders that are *only* > rated at about 3100psi. Not quite. 1 bar = 14.5037738 psi 300 bar = 4351.13214 psi > 1 bar = 14.5037738 psi > 300 bar = 4351.13214 psi I think we can safely round that to 14.5 and 4,350 psi. In rec.scuba, on Mon 10 Sep 2007 08:10:25a, "Lee Bell" <pleebell@bellsouth.net> wrote: > I think we can safely round that to 14.5 and 4,350 psi. Agreed. I definitely would not round it to 4500 psi like Don had suggested though. > I may have a handle on this now. The last time I dove in the crater I was > using aluminum tanks. According to the info I just researched on the Net, > you need more weight when diving with an aluminum tank than a steel tank, > especially towards the end of your dive as aluminum tanks become more > buoyant when they empty. Steel tanks remain less buoyant. No. The change in buoyancy, which is what you care about, is the same for an aluminum tank and a steel tank for the same volume of gas used. Note that's volume, not pressure. The change in buoyancy is a direct result of the gas you are no longer carrying. If you started the dive dead neutral (assumes there is such a thing) and you used 5 lbs (approximately the weight of gas in an 80 foot tank) your buoyancy would change by 5 lbs, no matter what size the tank is, no matter what the rated pressure is. > So, on my last certification dive I added weight to 8 lbs and was fine. > Now, using a steel tank, I assumed I should use 8 lbs, but with this new > information, and my experience along with your advice, I need to trim back > to 6 lbs and actually test it in the water. If 8 lbs was actually correct for the aluminum tank in fresh water, then it's quite easy to adjust for the different tank. Look up the buoyancy of each tank when empty and adjust by the difference. It's a little more complex if the size of the tank changes as well. Then you also have to account for the different weight of gas as the tank goes from full to empty. For example, my 100 cubic foot tanks experience more of a buoyancy shift from full to empty than my 80, 40, or 30 cubic foot tanks do. > As my instructor was teaching me in the crater, I need to swim down, not > get dragged down by extra weight or use my bc to control all my buoyancy. There's no such rule. In fact, you should pretty much always be able to descend simply by exhaling, even at the end of the dive. You should be noticably heavy at the beginning of the dive, near neutral at the end. < As I get deeper and things compress, I'll naturally lose buoyancy. This is true if you're wearing a wetsuit and if you start the dive with gas in your BCD or drysuit. If you don't use thermal protection and you don't start out with gas in your BCD, your buoyancy won't change enough to notice as you descend. There's nothing to compress. > Excuse me for wanting to understand everything down to the last molecule > of knowledge, but I learn best when I understand how things work. Not necessary. Not only do we agree with your desire to understand, we find that your current level of understanding is not yet where it should be, let alone down to the last molecule. We're not particularly impressed with the knowledge your training failed to provide. > Thanks again. Thanks for giving us the opportunity to discuss these things. It's why most of us are here. It gives us a chance to share things about a sport we really love and, at the same time, remind ourselves of things we haven't thought about much for a long time. Lee >> I may have a handle on this now. The last time I dove in the crater I >> was using aluminum tanks. According to the info I just researched on the [quoted text clipped - 53 lines] > > Lee Thanks, Lee, and everybody. So now my question is, is all this learned by experience or by using mathematical formulas? Seems to me if I rent most of my equipment when I travel, I have to have all the information on the tank I can get, then start figuring how much weight I need using mathematical formulas. On the other hand, if an instructor is along for the ride, I can tell them my experiences on the first dive and then adjust for the next dives. I can tell if I comfortable or not and how easy it is to maneuver up and down with a minimum of bc activity. Once I hit that comfort level I know that's my starting point for my next dive or vacation. For whatever reason my last instructor, when he saw me rising to the top all the time, came over and squeezed all the air out of my bc (and he was a big guy) and then the next day added two more lbs to my weight. All I know is I was a lot more comfortable in the water and it was easier to maneuver around. Only filled my bc at the surface, but my emergency ascent drill took some above average kicking to get to the surface and grab enough air to inflate my bc orally. > Thanks, Lee, and everybody. So now my question is, is all this learned by > experience or by using mathematical formulas? Most divers learned to dive one way all the time. They learned buoyancy control, if they learned it at all, by experience with that equipment. Not everybody learns what you're learning now. When divers change something, that's when they're most likely to start questioning their buoyancy and, eventually figure out how to adjust for changes. It's usually done by education guesswork. There are formulas for weighting, but they tend to get you in the ballpark at best. As time goes by, you'll learn a few things, more or less in order. First, you'll learn that you want to get your buoyancy correct. You've already done that. Next, you'll figure out what's right under one set of conditions, with one equipment configuration. Over time, you'll learn what it takes to adjust to different conditions, fresh versus salt water and even more and less dense salt water. The density of seawater is not the same everywhere. You'll also learn how to adjust for changes in your own equipment, just as I have. Some examples for me include 4 lbs for my 3mm wetsuit, 2 lbs if I go from my steel 100 cubic foot tanks to my neutrally buoyant 80s and another 4 if I go to a standard 80. It sounds like a lot of calculation, but pretty much anyone can add 4 to 2 to 4 and come up with 10. Learning what will affect your buoyancy and how much it will affect it by is the trick. Doing the math is a snap. > Seems to me if I rent most of my equipment when I travel, I have to have > all > the information on the tank I can get, then start figuring how much weight > I need using mathematical formulas. Not really. There are only so many tank types incommon use. You're most likely to get a standard 80 pretty much anyplace in the US, the Bahamas and the Carribean unless you make a point of asking for something else. Standard 80s are, well, standard. Thermal protection will vary by more, but it won't take long before you know how much weight to use for the kind of thermal protection you most often use. > On the other hand, if an instructor is along for the ride, I can tell them > my > experiences on the first dive and then adjust for the next dives. Or you can learn it for yourself. By the way, you are planning on paying this instructor that happens to be along, right? If not, how long do you think he's going to provide you with the services he gets paid for, for free? Lee >> Thanks, Lee, and everybody. So now my question is, is all this learned >> by experience or by using mathematical formulas? [quoted text clipped - 46 lines] > > Lee I get it. Each variable gets a weight assigned to it, and experience tells you what that weight should be. After awhile all you have to do is add up the variables to get the right weight. I think what throws me off is lifting that tank and coming to grips with the fact that the tank is buoyant, even though before I started diving I would have guessed jumping in the water with that tank alone would take me right to the bottom. In rec.scuba, on Mon 10 Sep 2007 09:19:02p, "Sheldon" <sheldon@XXXXXXXXsopris.net> wrote: > I get it. Each variable gets a weight assigned to it, and experience > tells you what that weight should be. After awhile all you have to do [quoted text clipped - 3 lines] > guessed jumping in the water with that tank alone would take me right > to the bottom. Next time you get through diving and you have a nearly empty tank, take the regulator off of it and you'll see how well it floats. A standard AL80 will weigh about 31.7 lbs. The air space in the tank (approximately 0.392 cu-ft) gives you 23.6 lbs of buoyancy (assuming 62.42718356 lbs per cu-ft of water and an AL80 actually only holding 77 cu- ft of air). AL80 tanks have a wall thickness of approximately 1/2 inch and a length of approximately 26 inches. This makes up for the rest of the buoyancy and results in appoximately 4 lbs of positive buoyancy when the tank is empty. Perhaps someone with a micrometer and a tank that has been cut open can give a more accurate measurement of the wall thickness of an AL80. One thing that you need to remember is that the buoyancy of an object is equal to the weight of the object minus the weight of the water that would be displaced by the object. This is also why we use denser materials for our weight belts (i.e. lead) since the weight of the water displaced is minimized. As such, 10 lbs of lead works better on your weight belt than 10 lbs of wood. > I get it. Each variable gets a weight assigned to it, and experience > tells you what that weight should be. After awhile all you have to do is > add up the variables to get the right weight. I think what throws me off > is lifting that tank and coming to grips with the fact that the tank is > buoyant, even though before I started diving I would have guessed jumping > in the water with that tank alone would take me right to the bottom. You're really close. Your guess that your tank is negative at the beginning of the dive is pretty accurate. I don't know of any metal tanks that are buoyant when full. Here's the scoop, more or less. Don't take my word for it, look it up with Google. My list is incomplete: - Standard 80s are slightly negative at the beginning of the dive and roughly 4 lbs positive when empty. Most divers never completely empty them. The rated pressure for these tanks is 3,000 psi. I used to wear 4 lbs when diving these tanks. Now I wear 6. My body's buoyancy has increased over the years. I'm more buoyant (fat) than I used to be. - Catalina and Luxfer both make aluminum 80s that are neutral when empty. They're about 5 lbs negative when full. The rated pressure for these tanks is 3,300 psi. I used to wear no weight with these tanks. These days I wear a couple of pounds for the same reasons sited above. - Steel tanks vary in buoyancy. My high pressure steel 100s look about the same size as an 80, but hold more. They're a pound or two negative when empty and 6 or 7 lbs negative when full. They're the only tanks I use that I generally add gas to my BCD (wing) at the beginning of a dive. By mid dive, I've let all the gas out of my bcd. I usually don't add any back until I'm on the surface. I use no weight with these tanks. Lee (snip)> > < As I get deeper and things compress, I'll naturally lose buoyancy. > > This is true if you're wearing a wetsuit and if you start the dive with gas > in your BCD or drysuit. If you don't use thermal protection and you don't > start out with gas in your BCD, your buoyancy won't change enough to notice > as you descend. There's nothing to compress. I think he meant that as he goes deeper and the pressure of the water being greater, he may need to compensate by adding air to his BCD. > > Excuse me for wanting to understand everything down to the last molecule > > of knowledge, but I learn best when I understand how things work. [quoted text clipped - 3 lines] > alone down to the last molecule. We're not particularly impressed with the > knowledge your training failed to provide. I'm not particularly unimpressed with it either. He needs to dive now to apply what he learned and see it in real time. > > Thanks again. > > Thanks for giving us the opportunity to discuss these things. It's why most > of us are here. It gives us a chance to share things about a sport we really > love and, at the same time, remind ourselves of things we haven't thought > about much for a long time. Yeah, baby!! >> This is true if you're wearing a wetsuit and if you start the dive with >> gas [quoted text clipped - 3 lines] >> notice >> as you descend. There's nothing to compress. > I think he meant that as he goes deeper and the pressure of the water > being > greater, he may need to compensate by adding air to his BCD. I'm sure he did. What I meant is that if you don't have any gas in your bcd, and you're not wearing any thermal protection, there's nothing external to compress. If nothing compresses, there's no change in buoyancy to compensate for. Lee <clipped> >> We're not particularly impressed with the >> knowledge your training failed to provide. > > I'm not particularly unimpressed with it either. He needs to dive now to > apply what he learned and see it in real time. I was well trained with regard to increases and decreases in buoyancy as pressure increases and decreases. I was trained how to figure out what your weight should be (inhale/exhale at the surface). However, what I've found is that when actually applied things tend to be off a bit, especially for a novice. I may be making up for lack of breath control with weight, and next time in the pool will empty my tank enough to do a check at the surface. I guess what I'm trying to gain from "your" experience (the entire group) is what are the symptoms of being overweighted or underweighted, aside from the obvious. My instructor at the shop has to rebuilt my regulator so I stopped by today and swapped weights going back to 6 lbs to allow for the steel tank. I'll know more when they reopen the pool in a week and I can get back in. But, you are all right in that I really need to get my butt into open water again to gain more experience in everything. You were all correct when you said to get your card and "then" learn how to dive. I learned enough to be comfortable and calm in the water, how to setup and breakdown my gear and enough stuff to get my a.s out of most binds I might get into. Right now I need a lot more experience in the water, but learning from others with experience certainly can't hurt, and that's why I'm here. You guys helped me a lot before I got certified and you are still helping me and pointing me towards places on the Internet I wouldn't have thought of. There's really no substitute for experience, but I can't thank you all enough for sharing yours with me. Sheldon > I guess what I'm trying to gain from "your" experience (the entire group) > is what are the symptoms of being overweighted or underweighted, aside > from the obvious. We don't have a problem with your side of this, at least I don't. You had one bad experience and came back to try again. You worked your way though things that go way beyond what most of us had to do to learn to dive. You've shown a continued interest, a good attitude toward learning and continue to pursue knowledge. That ain't bad. The training you got, however, was lacking in a number of fundamental elements and in some relatively small ways, appears to have provided incorrect information. That's not your fault and, without experience, you had no way to know. We know. Keep on asking your questions. You're learning and we're enjoying being able to help. > . . . and enough stuff to get my a.s out of most binds I might get into. Probably not, but you're moving in the right direction. > There's really no substitute for experience, but I can't thank you all > enough for sharing yours with me. You just did. You're welcome. > Now I'm confused. Are you telling me that an 80 cubic foot steel tank > rated at 2200 holds the same amount of air as an aluminum 80 cubic foot > tank rated at 3500 psi.? Or maybe a better way to put it is do they hold > the same amount of breaths? I understand the "full size" thing. I should > have been more specific. Specific wasn't important as long as you weren't confused. You apparently are. Yes, I'm telling you that an 80 cubic foot tank holds 80 cubic feet of gas no matter what the pressure. A high pressure 80 will have a smaller internal volume than a low pressure 80, but both will hold the same amount of gas, the same number of breaths and will change in buoyancy by the same amount as you take each breath. That's why they're both called 80 cubic foot tanks. The system is different in Europe, so be careful when you hear tank sizes expressed in liters. That normally refers to the internal volume of the bank, not how much gas is in it at it rated pressure. You'll also hear them talk about pressure in BAR which is close, but not quite the same as atmospheres. One BAR is 14.5 psi (approximately). One ATA is 14.7 psi. Their system is handy though since one BAR is also approximately equal to 10 meters of depth. Lee > Well, I got enough decent equipment to dive in the pool, which is only 12 > feet deep. When I was having buoyancy problems during my pool certification [quoted text clipped - 33 lines] > > Thanks again. Percentage volume change vs depth is greater as you get closer to the surface. Troubles with buoyancy close to the surface are a sign of too much air in yer BC, a result of being overweighted. esg >> Well, I got enough decent equipment to dive in the pool, which is only 12 >> feet deep. When I was having buoyancy problems during my pool [quoted text clipped - 40 lines] > > esg Thanks. So, you think I should swap the weights for 6 lbs? That's easy to do. I'm sure the guy will let me try both. I also guess I should test my boyancy at the surface (lungs full/lungs empty) and see which is closest to the basic settings. Also, do I need to adjust my weights depending on my planned dive when I get away from the pool? > Thanks. > [quoted text clipped - 5 lines] > Also, do I need to adjust my weights depending on my planned dive when I get > away from the pool? You should set your weight to whatever keeps you neutral at about 15 ft on a near empty tank. Lot of factors affect your bouyancy. Fresh water or saltwater? Thickness of wetsuit? Drysuit? Steel or aluminum tanks? Your body composition? >> Thanks. >> [quoted text clipped - 10 lines] > saltwater? Thickness of wetsuit? Drysuit? Steel or aluminum tanks? > Your body composition? So, it sounds like I need to find a weight that works at 12 to zero feet. I understand the rest. I think I'll bring 6 lbs with me when I go back to the pool and try both 6 and 8. The other poster may have been right. While I can kick to the top hard and get there with an empty bc, I need quite a bit of air in my bc to get off the bottom slowly with 8, and dumping air -- using the dump valve -- sends me right to the bottom of the pool fast. I figure I should be able to kneel on the bottom and be stable with an empty bc, but get off the bottom and still swim around without adding much air. I'm just using the pool to practice in and have some fun. Otherwise, I'm very comfortable in the water and at depth. I wish the pool was deeper. :-) I was reading about OW certification, and it seems if the instructor has a lot of confidence in you much of your second day, and especially your fourth dive, is pretty much for fun, which is exactly what we did. My instructor had all the final paperwork done at the end of the first day, or so he told me. So I feel pretty confident -- at least for a novice. Like I said: When I was in that crater I was able to go everywhere with an empty bc, but I was also much deeper than 12 feet. As a novice I assume on vacation the divemaster makes a good guess at how much weight you need and then you can adjust from there. "Sheldon" <sheldon@XXXXXXXXsopris.net> pounded away at his keyboard resulting in: :Like I said: When I was in that crater I was able to go everywhere with an :empty bc, but I was also much deeper than 12 feet. As a novice I assume on :vacation the divemaster makes a good guess at how much weight you need and :then you can adjust from there. Bad assumption. If you don't tell him, he'll have to guess but it won't necessarily be a good one. Dan Bracuk Never use a big word when a diminutive one will do. > "Sheldon" <sheldon@XXXXXXXXsopris.net> pounded away at his keyboard > resulting in: [quoted text clipped - 11 lines] > > Dan Bracuk I assume you're right. I'm a big boy now and will have to figure these things out on my own. But, a little help from your friends never hurts. :-) >>> As a novice I assume on vacation the divemaster makes a good guess at >>> how much weight you need and then you can adjust from there. >> Bad assumption. If you don't tell him, he'll have to guess but it >> won't necessarily be a good one. > I assume you're right. I'm a big boy now and will have to figure these > things out on my own. But, a little help from your friends never hurts. > :-) Help from your friends is fine as long as you don't count on it. Self responsibility is the rule, not the exception. The DM is not your friend. He's just doing his job and you are not his only priority. You are your only priority. Lee > So, it sounds like I need to find a weight that works at 12 to zero feet. > I understand the rest. I think I'll bring 6 lbs with me when I go back to [quoted text clipped - 5 lines] > stable with an empty bc, but get off the bottom and still swim around > without adding much air. It does sound like you're a bit overweighted. Personally, I shoot for neutral buoyancy just below the surface with about 500 psi left in the tank. I don't want to do a buoyant ascent from any depth. In order to get right with about 500 psi remaining, you're going to be a bit heavy for the rest of the dive. There's no help for it. That's what BCs are for. If you're just right, you probably won't be all that stable kneeling on the bottom. You're going to be just barely in contact with the bottom. Any movement will shift you from the bottom, as will inhaling deeply. That's what neutral buoyancy is all about. Those of us that dive where the bottom is full of living things not only don't worry about kneeling on it, we make a significant effort to avoid contact with it at all. It's the ecologically friendly thing to do. Your training was done on the bottom only to make it easier for you to concentrate on the single skill without worryng about buoyancy and other things at the same time. You were almost certainly over weighted at that time, intentionally. > Like I said: When I was in that crater I was able to go everywhere with > an empty bc, but I was also much deeper than 12 feet. As a novice I > assume on vacation the divemaster makes a good guess at how much weight > you need and then you can adjust from there. Nope. You make the good guess and adjust on each dive until you have it right. You're a certified diver now. You no longer either need, or should, depend on the DM to do it for you. You'll probably guess wrong if you're in salt water, but you should be able to get close enough. It's better to be a bit heavy than a bit light. Lee >> So, it sounds like I need to find a weight that works at 12 to zero feet. >> I understand the rest. I think I'll bring 6 lbs with me when I go back [quoted text clipped - 35 lines] > > Lee Thanks for the advice. Yeah, I guess I have to learn to do things for myself now. My first saltwater dive should be interesting. :-) Based on past experience, at least in the pool, I should probably be at 6 lbs since I did have trouble anchoring myself to the bottom with 6. In the crater we were not allowed to touch bottom. It stirs up too much silt and destroys visibility for everyone. > Thanks for the advice. Yeah, I guess I have to learn to do things for > myself now. My first saltwater dive should be interesting. :-) Based on > past experience, at least in the pool, I should probably be at 6 lbs since > I did have trouble anchoring myself to the bottom with 6. In the crater > we were not allowed to touch bottom. It stirs up too much silt and > destroys visibility for everyone. Huh. What agency trained you again? BTW, I usually dive about two pounds heavy, for ease and convenience. Being "perfectly" weighted is a matter of perspective. Many people here seem to have a goal of carrying the absolute minimum weight possible, and if it works for them, fine. But I don't see any particular advantage to it. Two pounds gives me a better sink rate, and more control at 15 ft, especially if I'm with students, or in heavy seas. In fact, when I'm with students, I usually carry an extra 2 and 3 pounder, for the instructor to dole out. > Thanks for the advice. Yeah, I guess I have to learn to do things for > myself now. My first saltwater dive should be interesting. :-) Based on > past experience, at least in the pool, I should probably be at 6 lbs since > I did have trouble anchoring myself to the bottom with 6. In the crater > we were not allowed to touch bottom. It stirs up too much silt and > destroys visibility for everyone. Try not to get hung up on thinking in terms of a specific weight. Find something that is as right as possible with specific equipment, in specific conditions and adjust for changes in equipment and conditions. For example, I know what the right weight for salt water, is for the equipment I normally use including a 6 lb stainless backplate, a tank that is slightly negative when empty, and no thermal protection. It does not matter what that weight is. What does matter is what I do if I change something. Here's some examples: If I use a standard 80 cubic foot tank, I need to add about 5 lbs because that's the difference in buoyancy due to the tank. If I use my 3mm wetsuit, I need to add about 4 lbs because that's the difference in buoyancy due to my wetsuit. If I were to use a thicker wetsuit or a drysuit, I would need to add more because their change in buoyancy is greater. If I dive in fresh water, I need to adjust the other way since fresh water is less dense than salt water. Lee >> Thanks for the advice. Yeah, I guess I have to learn to do things for >> myself now. My first saltwater dive should be interesting. :-) Based on [quoted text clipped - 22 lines] > > Lee Makes sense to me. > So, it sounds like I need to find a weight that works at 12 to zero feet. I > understand the rest. I think I'll bring 6 lbs with me when I go back to the [quoted text clipped - 4 lines] > figure I should be able to kneel on the bottom and be stable with an empty > bc, but get off the bottom and still swim around without adding much air. I'm thinking it is your steel tank that's helping to send you to the bottom so fast. I don't do pool dives, but when I'm at 15' on an ascent, I don't have any air in my BC and I can breathe myself up, no kicking involved. I guess what I'm trying to say is that all this pool practice you are doing with the steel tank, isn't really helping you establish what weighting you are going to need on your next open water dive. And none of that even addresses the aspect of fresh water vs salt water. (snip) >>>Thanks. >>> [quoted text clipped - 19 lines] > figure I should be able to kneel on the bottom and be stable with an empty > bc, but get off the bottom and still swim around without adding much air. It is really quite easy to determine your buoyancy. Your OW instructor should have gone over this. Whatever your configuration, with a near empty tank, an empty BC you should float just about mask level in the water. You shouldn't sink to the bottom and you shouldn't be floating on the surface. If you change anything that would affect your buoyancy, such exposure protection, or tank style, you will need to re-check your buoyancy. > Like I said: When I was in that crater I was able to go everywhere with an > empty bc, but I was also much deeper than 12 feet. As a novice I assume on > vacation the divemaster makes a good guess at how much weight you need and > then you can adjust from there. I would not make that assumption. If you are uncertain, you might ask the divemaster for assistance. >>>>Thanks. >>>> [quoted text clipped - 37 lines] > I would not make that assumption. If you are uncertain, you might ask the > divemaster for assistance. You are correct, and I do understand how to measure buoyancy by taking a breath and floating at the surface. I was just having so much fun I kinda forgot to check it. I did check my air a lot, however. :-) nitespark <nitespark@cox.net> pounded away at his keyboard resulting in: :It is really quite easy to determine your buoyancy. Your OW instructor :should have gone over this. Whatever your configuration, with a near :empty tank, an empty BC you should float just about mask level in the :water. You shouldn't sink to the bottom and you shouldn't be floating :on the surface. Codswallop. First of all, this mask level stuff is too precise. What if you just float to your chin. Secondly, with a near empty tank, you want the least amount of weight that will cause you to sink when you exhale. Keep it simple. Dan Bracuk Never use a big word when a diminutive one will do. > nitespark <nitespark@cox.net> pounded away at his keyboard resulting > in: [quoted text clipped - 14 lines] > > Dan Bracuk As they say, KISS. :-) I'd think you could go crazy trying to get this exact. And what if you had something heavy for lunch? > > nitespark <nitespark@cox.net> pounded away at his keyboard resulting > > in: [quoted text clipped - 17 lines] > As they say, KISS. :-) I'd think you could go crazy trying to get this > exact. And what if you had something heavy for lunch? "Note to self, always hit the banos before dive." ;^) > nitespark <nitespark@cox.net> pounded away at his keyboard resulting > in: [quoted text clipped - 12 lines] > Secondly, with a near empty tank, you want the least amount of weight > that will cause you to sink when you exhale. Keep it simple. Sheldon is a new diver, probably just recently completed is OW. I was just telling him the procedure PADI outlines which is probably similar or the same as other agencies. >> First of all, this mask level stuff is too precise. What if you just >> float to your chin. >> >> Secondly, with a near empty tank, you want the least amount of weight >> that will cause you to sink when you exhale. Keep it simple. > Sheldon is a new diver, probably just recently completed is OW. > I was just telling him the procedure PADI outlines which is probably > similar or the same as other agencies. As I recall, Sheldon's new certification is from PADI, suggesting that your method is not what PADI outlines, at least not for him. We're trying to help Sheldon improve from whatever it was he got, or didn't get, from his instructor. Without judging anyone, or their advice, mine pretty much agrees with Dan's. The easiest way I know to get your buoyancy right is to determine how much weight just allows you to sink when you exhale with a nearly empty tank. Since Sheldon's swimming around a pool occasionally, presumably independently, it's pretty easy for him to do. At the end of one of his swims, with somewhere around 500 psi in his tank, he can exhaust all the gas from his BCD and experiment until he has it right. That gives him a starting point from which to adjust as he changes equipment and conditions. I did this long ago behind my own boat, taking or placing weights on my the dive platform until I had something I liked. Later, I adjusted as necessary for changes in my body's buoyancy (I got fatter and more buoyant) and my preference to be neutral nearer the middle of my dive (I prefer to minimize the gas in my wing during the dive, choosing to make small adjustments by changing breathing patterns rather than by changing weight or gas in my wing). Lee >>>First of all, this mask level stuff is too precise. What if you just >>>float to your chin. [quoted text clipped - 10 lines] > Sheldon improve from whatever it was he got, or didn't get, from his > instructor. From page 95 of my OW student manual- "1-Enter the water with all your equipment on and your estimated weight requirement. 2-Keep your regulator in your mouth and staying at the surface, deflate your BCD and hold a normal breath. Be ready to kick or hold onto something in case you got too much weight. 3-You should float at eye level. If not, add or subtract weight until you do. You can hold weights while you figure out how much you need, then adjust your weight system. 4-As a final check, exhale. You'll begin to slowly descend if you're properly weighted. 5-If you you're using a full cylinder, now add a small amount of weight (usually about 2kg/5lb) Why? Remember, air has weight (thats why it causes pressure.) As you use up the air in your tank, the tank gets lighter. Using a single cyclinder, adding about 2kg/5lb compensates so that you have about the proper weight at the end of your dive with a near empty cylinder." > 4-As a final check, exhale. You'll begin to slowly descend if you're > properly weighted. This is where Dan started. > 5-If you you're using a full cylinder, now add a small amount of weight > (usually about 2kg/5lb) Why? Remember, air has weight (thats why it > causes pressure.) As you use up the air in your tank, the tank gets > lighter. Using a single cyclinder, adding about 2kg/5lb compensates so > that you have about the proper weight at the end of your dive with a near > empty cylinder." Not a bad addition. Of course the recommended method does not address compression of thermal protection or gas in the BCD. nitespark <nitespark@cox.net> pounded away at his keyboard resulting in: : From page 95 of my OW student manual- : [quoted text clipped - 14 lines] :that you have about the proper weight at the end of your dive with a :near empty cylinder." Here is the version for certified divers who don't have the option of getting in and out of the water lots of times with different amounts of weights. 1. Guess how much weight you will need and add about 5 llbs. This is the current weight. 2. Go for a dive. 3. At the end of your dive, get to the surface and then do a sink test. Deflate your bc and exhale. Do you sink? If no, add a pound to the current weight, if yes, subtract a pound. Repeat Steps 2 and 3 with the revised current weight. Once you have subtracted a pound on one dive and then put it back on the next, or vice versa, you have the correct weight. Dan Bracuk Never use a big word when a diminutive one will do. > nitespark <nitespark@cox.net> pounded away at his keyboard resulting > in: [quoted text clipped - 35 lines] > > Dan Bracuk My tank will be almost empty on my next venture into the pool. I'll borrow some weights and try to zero it in on my next "dive." BTW, do both weights have to be equal and split on either side? In other words to get to 6 lbs do I have to have 3 lbs on each side of my belt, and if I decide to go to 5 lbs can I wear 3 on one side and two on the other? > My tank will be almost empty on my next venture into the pool. I'll > borrow some weights and try to zero it in on my next "dive." BTW, do both > weights have to be equal and split on either side? In other words to get > to 6 lbs do I have to have 3 lbs on each side of my belt, and if I decide > to go to 5 lbs can I wear 3 on one side and two on the other? For now, you're working on discovering what the right amount of weight is. Where it's located is another issue, usually referred to as trim. The short answer to your question is that the more symetrical you are, including all sources of positive and negative buoyuancy, the better your trim will be. On the other hand, a pound difference on one side or the other, isn't going to be a particularly noticable thing. Three on one side and two on the other is fine. Lee >> My tank will be almost empty on my next venture into the pool. I'll >> borrow some weights and try to zero it in on my next "dive." BTW, do [quoted text clipped - 11 lines] > > Lee Thanks >>nitespark <nitespark@cox.net> pounded away at his keyboard resulting >>in: [quoted text clipped - 41 lines] > do I have to have 3 lbs on each side of my belt, and if I decide to go to 5 > lbs can I wear 3 on one side and two on the other? Works much better if evenly distributed otherwise you will be fighting constantly to keep from rolling on your side. Remember, the heaviest part will be trying to pull you down. 1 lb of weight won't make much difference. [PADI procedure and discussion deleted] >> Dan Bracuk > [quoted text clipped - 4 lines] > belt, and if I decide to go to 5 lbs can I wear 3 on one side and > two on the other? This is a different problem -- trim. Within reason, it helps to balance things. But don't stress to the point of obsession. A difference of up to a couple of pounds between sides should be simple to compensate. If (when) you get your personal kit, *then* tune it right in. In the meantime, the reality is that with rental kit the goal is generally "near enough is good enough", except that if you will be doing dives with recommended safety stops, you need to be able to hold the stop comfortably. Some of the stuff I've done DM'ing for courses has involved off-centre weighting up to 8-10 lbs to one side or the other. This starts to get difficult to manage, when it is combined with being overweighted by 16 pounds, more or less. (extra weight to hand to students who need it - weights to hold hoops on the bottom for a peak performance buoyancy dive.) My buoyancy was anything but peak. ;-) Just my $0.02 -Don > My tank will be almost empty on my next venture into the pool. I'll borrow > some weights and try to zero it in on my next "dive." BTW, do both weights > have to be equal and split on either side? In other words to get to 6 lbs > do I have to have 3 lbs on each side of my belt, and if I decide to go to 5 > lbs can I wear 3 on one side and two on the other? As you get better, you'll want to try to position your weights / bouyancy devices evenly around your body. Some people find that they need to wear a pound or so around each ankle to help them maintain the proper orientation in the water. Others find that it works best to keep all of the weight on their belt (area). Personally, I have the bulk of my weight in two pouches on my tank bands. I put it there because it helps to countract the "forward" push of my BCD at the surface. I also keep a pound or two in the "quick release" pockets of my BCD. That way, if I have to jettison weight, I only lose a couple of pounds and that should be enough to make me positively bouyant but not so much that I skyrocket to the surface. Don't worry too much about the weight placement until you figure out how much you really need. Then, you can experiment with different placements to figure out what works the best for you. > > My tank will be almost empty on my next venture into the pool. I'll > borrow [quoted text clipped - 9 lines] > pound or so around each ankle to help them maintain the proper orientation > in the water. I strongly discourage putting weights on your ankles. (snip) >>>My tank will be almost empty on my next venture into the pool. I'll >> [quoted text clipped - 27 lines] > > (snip) Ankle weights are not that bad. Much depends on your individual buoyancy. I know some very experienced divers that wear them with their drysuits. I have also seen some divers using ankle weights with shorty wetsuits. After you have mastered the basics, whatever works best for you beyond that is personal preference. > Ankle weights are not that bad. Much depends on your individual > buoyancy. I know some very experienced divers that wear them with their > drysuits. I have also seen some divers using ankle weights with shorty > wetsuits. After you have mastered the basics, whatever works best for > you beyond that is personal preference. How's about a weighted hood for those of us who are light-headed? >>Ankle weights are not that bad. Much depends on your individual >>buoyancy. I know some very experienced divers that wear them with their [quoted text clipped - 3 lines] > > How's about a weighted hood for those of us who are light-headed? If its a lead lined hood, probably made in China. >> Ankle weights are not that bad. Much depends on your individual >> buoyancy. I know some very experienced divers that wear them with their [quoted text clipped - 3 lines] > >How's about a weighted hood for those of us who are light-headed? The alternative is a good butt-wing. JF > >>>My tank will be almost empty on my next venture into the pool. I'll > >> [quoted text clipped - 29 lines] > > > Ankle weights are not that bad. I believe he should be learning to dive without weights on his ankles. My feet seemed to be floating up when I first started out. I tried it with ankle weights, which certainly fixed the immediate problem. However, they weren't necessary because I gave them up almost immediately and learned to dive without them. Now my feet are up because I put them up, inasmuch as, my fins are generally in the frogkick or ready to helicopter position. Regardless, don't need them at all to flutter kick either. If a new diver starts out depending on them, he will learn on them and then become a more experienced diver that you see around with ankle weights. >Much depends on your individual > buoyancy. I know some very experienced divers that wear them with their > drysuits. I have also seen some divers using ankle weights with shorty > wetsuits. After you have mastered the basics, whatever works best for > you beyond that is personal preference. >>>>>My tank will be almost empty on my next venture into the pool. I'll >>>> [quoted text clipped - 53 lines] >>wetsuits. After you have mastered the basics, whatever works best for >>you beyond that is personal preference. Which is why I qualified it with the last sentence. After mastering the basics, fine tune it. Some people use ankle weights for that, others don't. Just sounded like you were making a blanket condemnation of ankle weights. >> I strongly discourage putting weights on your ankles. >> Ankle weights are not that bad. I've never used ankle weights, or needed to, so I can't argue this one much either way. The one thing I can add, however, is an observation that a substantial majority of those we see with buoyancy and trim problems are finning the entire time to keep their feet up, not to keep them down. We just had a discussion on the Disney video regarding how few of the divers looked like they knew what they were doing. Virtually all of them we identified as novices, were diving feet down. Lee >>>I strongly discourage putting weights on your ankles. > [quoted text clipped - 10 lines] > > Lee Usually, they're feet down because they're overweighted and trying to stay off the bottom. Ankle weights help keep yer feet down even when yer properly weighted. Although "swim-diving" has been de rigeur for about 70 years now, there's still a lot of folks that like to feel the coral under their feet. esg > Although "swim-diving" has been de rigeur for about 70 years now, > there's still a lot of folks that like to feel the coral under their feet. Hopefully the fire coral >> >>>My tank will be almost empty on my next venture into the pool. I'll >> >> [quoted text clipped - 34 lines] > > I believe he should be learning to dive without weights on his ankles. It's easier to learn to dive horizontal than vertical. Leg weights are excellent training tools, and make very utilitarian trim weights later. > My feet seemed to be floating up when I first started out. I tried it > with [quoted text clipped - 11 lines] >> wetsuits. After you have mastered the basics, whatever works best for >> you beyond that is personal preference. >> > My tank will be almost empty on my next venture into the pool. I'll >> borrow [quoted text clipped - 15 lines] > > I strongly discourage putting weights on your ankles. Sounds like something the Mob would do. :-) >> My tank will be almost empty on my next venture into the pool. I'll > borrow [quoted text clipped - 24 lines] > really need. Then, you can experiment with different placements to figure > out what works the best for you. Not sure about the ankle weights, but being able to drop a few lbs without losing all your weights sounds like a good idea. > >> My tank will be almost empty on my next venture into the pool. I'll > > borrow [quoted text clipped - 27 lines] > Not sure about the ankle weights, but being able to drop a few lbs without > losing all your weights sounds like a good idea. I don't use them now and, for that matter, I haven't ever used them. I've heard about it though (my instructor may have mentioned in passing that some people use them). >> >> My tank will be almost empty on my next venture into the pool. I'll >> > borrow [quoted text clipped - 41 lines] > some > people use them). Not sure about ankle weights, but after reading the post about splitting weights, it might not be a bad idea to wear half your weights on a belt and the other half in your bc pockets. > >> >> My tank will be almost empty on my next venture into the pool. I'll > >> > borrow [quoted text clipped - 45 lines] > weights, it might not be a bad idea to wear half your weights on a belt and > the other half in your bc pockets. Like I said before: Step 1: Figure out how much you need. Step 2: Figure out where to put it based on your needs > > >> >> My tank will be almost empty on my next venture into the pool. I'll > > >> > borrow [quoted text clipped - 55 lines] > Step 1: Figure out how much you need. > Step 2: Figure out where to put it based on your needs Step 3: Go diving and keep practicing till you get it right gc >> "Sheldon" <shel...@XXXXXXXXsopris.net> wrote in message >> > >> >> My tank will be almost empty on my next venture into the pool. >> > >> >> I'll [quoted text clipped - 71 lines] > > Step 3: Go diving and keep practicing till you get it right He is. In rec.scuba, on Thu 13 Sep 2007 09:20:10a, "Chris Guynn" <chris.guynn@gamil.com> wrote: > Like I said before: > Step 1: Figure out how much you need. > Step 2: Figure out where to put it based on your needs There's weight that you need for ballast and their's ditchable weight that you need to assist in an emergency ascent. Most people just put all the weight on a weight belt. Some of us take some of the weight off of the weight belt and add it to our rig by using a metal (stainless steel or aluminum) backplate. Some add a bit more in the form of a V-weight put between the tanks in a doubles setup. Some strap a normal weight onto their tank with a cam strap. Some put a flat weight in the tank boot (if it has one). Some people thread a couple of normal weights on their shoulder straps. I've even seen people tie / wire in weights to holes around the perimeter of their backplate. Any of them will probably work. I tend to use a combination of a stainless steel backplate and a weight belt, but if I was diving wet in very cold water, I might consider adding weight to my rig instead of just to my waist. If I was to need to adjust my head trim down a bit, perhaps putting a pound or two on each shoulder underneath the chest D-ring might help. I haven't had a desire to dive in that cold of water yet, so I have not had a need to find out if it makes a difference. Of course, a lot of the buoyancy problems that we are talking about often disappear if you just dive in water warm enough that you don't need a wetsuit. Things were so much simpler back in the old days when we just had straps going directly from the tank to our shoulders. > There's weight that you need for ballast and their's ditchable weight that > you need to assist in an emergency ascent. Most people just put all the [quoted text clipped - 6 lines] > shoulder straps. I've even seen people tie / wire in weights to holes > around the perimeter of their backplate. Any of them will probably work. You must dive with a lot of weirdos. The vast majority of people I see diving who aren't using weight belts simply stick the weights in pockets in their weight-integrated BCs. No cam straps, wires, or even backplates required. > Things were so much simpler back in the old days when we > just had straps going directly from the tank to our shoulders. Yep, and breathing directly from the tank valve can eliminate regulator failure. Much simpler. In rec.scuba, on Thu 13 Sep 2007 10:22:37a, Greg Mossman <mossman@qnet.com> wrote: > You must dive with a lot of weirdos. The vast majority of people I > see diving who aren't using weight belts simply stick the weights in > pockets in their weight-integrated BCs. No cam straps, wires, or even > backplates required. I suspect that most of the people I know don't use weight-integrated BCs, although I have seen those who use jacket style BCs add a couple of pounds in each pocket in add |
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