Buoyancy problem
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1bubbleoff
Contributor
Sandie-
Unless I miss my guess...your diving a 12 liter steel tank. That's basically by US standards..an 85cuft tank. I suspect..its a Faber (given your geographic location)...which is about a 6 pd swing. What is your height and weight if I may ask? I'd strongly suspect that 1) lowering the tank 1-2" may help by lowering the center of rotation...and 2) a 12 L tank on a smaller person often poses a challange in regards to negative weighting and achieving a neutral balance..heavy tank..add air to BCD to get neutral...change position...larger air bubble moves around, and it is harder to control. Make sense?
Ask your instructor to put you in a 10l tank..and INSIST...on a THOROUGH weight check. Don't be afraid to try different combinations of weights and tanks and tank/weight positions. This is what "dialing in" is all about...just have to spend some time and effort achieving the best combination FOR YOU.
Just my suggestion...have fun and welcome to a whole new WET world!!!
Bubs
Unless I miss my guess...your diving a 12 liter steel tank. That's basically by US standards..an 85cuft tank. I suspect..its a Faber (given your geographic location)...which is about a 6 pd swing. What is your height and weight if I may ask? I'd strongly suspect that 1) lowering the tank 1-2" may help by lowering the center of rotation...and 2) a 12 L tank on a smaller person often poses a challange in regards to negative weighting and achieving a neutral balance..heavy tank..add air to BCD to get neutral...change position...larger air bubble moves around, and it is harder to control. Make sense?
Ask your instructor to put you in a 10l tank..and INSIST...on a THOROUGH weight check. Don't be afraid to try different combinations of weights and tanks and tank/weight positions. This is what "dialing in" is all about...just have to spend some time and effort achieving the best combination FOR YOU.
Just my suggestion...have fun and welcome to a whole new WET world!!!
Bubs
OP
Sandie7
Registered
Hi Bubs,
I am 1.65m, 52 kilos. And yes, I did have a lot of trouble with the equipment at first, everything was too big and heavy. It is all being fixed, and everytime something is fixed I feel a lot better.
You are right, actually a 10 liter tank has already been thought for me, especially because it seems I always end classes with a lot of air - they say that when I calm down I will need even less, so a 10 liter tank will be more than enough.
Unfortunately lowering the tank, at least the tank I've been using, can't be done ... the strap is already at "the top", and even so last class my head was touching it when I was looking forward.
As for the weights, no doubt a lot has to be fixed too ...
Thank you for all advice, and thanks for the welcome
LowDrag
Contributor
If your tank is that far down and you are still touching your first stage with your head I would also be looking the BC. Something doesn't seem right there. It just seems to me that having your tank strap that high up to where it is near the curve of the tank is not a good thing. The first thing that comes to my mind is the band slipping and your tank falling then yanking your reg out of your mouth. I could be wrong but that is just my best guess.
1bubbleoff
Contributor
Oh Lordy..lol..your just alittle wisp of a gal!! Yup..smaller tank is DEFINITELY in order lol. Wonder if there's a LP50 hanging around?..
I really think..that in this case.."less is more". Lowdrag brings up a VERY good point...make sure your in a properly sized BCD..I suspect you should be in an XS...
I have to wonder given your statement..."the strap is already at "the top", and even so last class my head was touching it when I was looking forward. "... if your BCD is riding up on you. Try positioning your tank so that the top of the valve..is about level with the "collar" of your BCD...
And ask your instructor if it is possible to LOWER the tank cam band on the BCD...that will allow you to move the tank up and down to help balance you.
Best of luck!! Dive safe !
Bubs
I really think..that in this case.."less is more". Lowdrag brings up a VERY good point...make sure your in a properly sized BCD..I suspect you should be in an XS...
I have to wonder given your statement..."the strap is already at "the top", and even so last class my head was touching it when I was looking forward. "... if your BCD is riding up on you. Try positioning your tank so that the top of the valve..is about level with the "collar" of your BCD...
And ask your instructor if it is possible to LOWER the tank cam band on the BCD...that will allow you to move the tank up and down to help balance you.
Best of luck!! Dive safe !
Bubs
keala11
New
I am just asking about buoyancy period. I wear a 1 mm with boots and hood and use 8 lbs while diving in cancun / cozumel. I sink to the bottom and have to put back in 2 pumps of air. Sometimes I find my on he ocean floor with my finger pushing up. THat tells me I'm too heavy. Well at the end of the dive when I have about 1200 less in the tank my ass is in the air. No matter how hard I try to stay vertical or horizontal.
Questions --would a weight belt help? Would dropping another 2 pounds when I use this wetsuit help?
Any suggestions appreciated
Thank you tj
Sent from my iPhone using Tapatalk
Ok, think about what's neg and what's positive on what you're wearing.
Your suit is probably about 2 lbs positive,+ boots etc, another 2 lbs.
Your tank (al 80) will be about 3-4 lbs positive at the end of the dive.
So, you need around 8 lbs. confirm this buy doing a buoyancy check.
The 3-4 lbs worth of air will be used during the dive so you have to add air to the bcd (2 blasts....) to "compensate" for this.
Ensure that your bcd is empty at the end of the dive, watch your breathing at the end. Could be just you're anxiety at the end of the dive keeping large breaths of air in your lungs.
Sent from my iPhone using Tapatalk
Your suit is probably about 2 lbs positive,+ boots etc, another 2 lbs.
Your tank (al 80) will be about 3-4 lbs positive at the end of the dive.
So, you need around 8 lbs. confirm this buy doing a buoyancy check.
The 3-4 lbs worth of air will be used during the dive so you have to add air to the bcd (2 blasts....) to "compensate" for this.
Ensure that your bcd is empty at the end of the dive, watch your breathing at the end. Could be just you're anxiety at the end of the dive keeping large breaths of air in your lungs.
Sent from my iPhone using Tapatalk
keala, I hear your question very often from novice divers.
Let's address the idea that finding yourself discreetly pushing up off the bottom means that you are "too heavy". What it really means is that you are not neutral -- in that sense, at that moment, you are "heavy", but you may or may not be overweighted. Weighting is calibrated to ensure that you can remain underwater when you have used all the gas from your tank that you intend to use. At the beginning of the dive, when the tank is full, you will necessarily be a few pounds negative, because of the weight of the gas in the tank that you haven't used yet. This is one of the reasons we use BCs, is so that we can weight ourselves to be able to float effortlessly at any point in the dive. That will require some air in the BC at the beginning, which you will gradually vent as the dive progresses, until you have little or none at your safety stop.
At the beginning of the dive, you will have to add enough air to the BC to compensate for the extra weight you are carrying. If you don't add enough, you will gradually drift downward, which is sort of what you are describing. Putting a little bit more air in will prevent that need to push off the bottom. But there is a problem with that, for many novice divers, and here it is: If you are not horizontal -- if your feet are below you -- you will be pushing yourself upward each time you kick. To avoid going steadily shallower, you WILL have to keep yourself somewhat negative, to counter that pushing force. That means that, each time you STOP kicking, you will sink. If you put enough air in to be neutral, you can't hold your depth while swimming; if you balance the sinking tendency with your kicking, you cannot hover.
I initially thought you were probably overweighted, but I thought it through again. If you are using a standard BC, which is likely to be a couple of pounds positive, and an aluminum tank, which is 4 pounds positive when empty, you probably need somewhere around 6 pounds of lead, and two more or less doesn't make enough difference to worry about.
But the butt-light problem is an inherent issue with aluminum tanks. They barely sink when they are full, and as they empty, they not only become positive, but they float valve-down. You can actually see that in your photo -- see how the tank has lifted off your body at the bottom? The only way to solve this is to set yourself up to be a bit foot-heavy at the beginning of the dive. That, you can counter by moving the air in your BC to the bottom, or if you are using negative fins, bending your knees. When you are at the end of the dive and the BC is empty, you cannot compensate by moving gas around -- but if you have negative fins, stretching your legs out will help. Adding additional weight that you don't need is not a good answer, although moving the weight you DO need lower on your body is definitely a useful strategy. When I was recently diving in the Philippines, using Al80s, I was putting a couple of pounds of lead in my dry suit pockets to avoid the face-plant problem at the end of the dive
Let's address the idea that finding yourself discreetly pushing up off the bottom means that you are "too heavy". What it really means is that you are not neutral -- in that sense, at that moment, you are "heavy", but you may or may not be overweighted. Weighting is calibrated to ensure that you can remain underwater when you have used all the gas from your tank that you intend to use. At the beginning of the dive, when the tank is full, you will necessarily be a few pounds negative, because of the weight of the gas in the tank that you haven't used yet. This is one of the reasons we use BCs, is so that we can weight ourselves to be able to float effortlessly at any point in the dive. That will require some air in the BC at the beginning, which you will gradually vent as the dive progresses, until you have little or none at your safety stop.
At the beginning of the dive, you will have to add enough air to the BC to compensate for the extra weight you are carrying. If you don't add enough, you will gradually drift downward, which is sort of what you are describing. Putting a little bit more air in will prevent that need to push off the bottom. But there is a problem with that, for many novice divers, and here it is: If you are not horizontal -- if your feet are below you -- you will be pushing yourself upward each time you kick. To avoid going steadily shallower, you WILL have to keep yourself somewhat negative, to counter that pushing force. That means that, each time you STOP kicking, you will sink. If you put enough air in to be neutral, you can't hold your depth while swimming; if you balance the sinking tendency with your kicking, you cannot hover.
I initially thought you were probably overweighted, but I thought it through again. If you are using a standard BC, which is likely to be a couple of pounds positive, and an aluminum tank, which is 4 pounds positive when empty, you probably need somewhere around 6 pounds of lead, and two more or less doesn't make enough difference to worry about.
But the butt-light problem is an inherent issue with aluminum tanks. They barely sink when they are full, and as they empty, they not only become positive, but they float valve-down. You can actually see that in your photo -- see how the tank has lifted off your body at the bottom? The only way to solve this is to set yourself up to be a bit foot-heavy at the beginning of the dive. That, you can counter by moving the air in your BC to the bottom, or if you are using negative fins, bending your knees. When you are at the end of the dive and the BC is empty, you cannot compensate by moving gas around -- but if you have negative fins, stretching your legs out will help. Adding additional weight that you don't need is not a good answer, although moving the weight you DO need lower on your body is definitely a useful strategy. When I was recently diving in the Philippines, using Al80s, I was putting a couple of pounds of lead in my dry suit pockets to avoid the face-plant problem at the end of the dive
Brewone0to
Contributor
Couldn't have said it better than TSandM's post.
Thought this could help anyone rethinking sizes and weight,and
weight swing characteristics of various tanks from full to empty.
Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan
Thought this could help anyone rethinking sizes and weight,and
weight swing characteristics of various tanks from full to empty.
Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan
Sandie, you will probably never be capable of doing the 'buddha" pose with your current setup. As far as your ears go, I believe Sand Man hit it right on the money. Anyway, your issue with the pose is strictly based off of weight. I have the same issue whenever a student of mine asks for me to 'do the pose', even though I don't teach neutral buoyancy that way. If I'm in a shorty with an AL 80 in fresh water, I'm perfectly content diving without weight (and can perform the maneuver without any problem). I normally dive with a steel 130, meaning I could actually get away with adding styrofoam to my rig and I'd still be good. Nonetheless, in order for me to look like buddha using my steel 130, I need to place ~8 pounds of lead on my front side (positioned low) in order to counteract the effect of the tank on my back. While this allows the maneuver to be completed without flipping on my back, it's horrible in practice. The only reason I would dive with 8 extra pounds is in the event one of my students didn't have enough... I'd be able to donate a few pounds while still being able to achieve neutral buoyancy.
Sounds to me that the only way you'll be able to complete this 'skill' is by doing the same- adding weight when you really shouldn't. Alternatively, try finding an aluminum tank- I'm willing to bet you'll find much more enjoyment out of that compared over weighting. Lastly, you could always try doing the maneuver upside down... that's the only way I can do the skill with a steel tank while not carrying extra weight. It's also quite fun to do when performing a deco (or safety) stop. You'll get quite a few interesting looks...
Sounds to me that the only way you'll be able to complete this 'skill' is by doing the same- adding weight when you really shouldn't. Alternatively, try finding an aluminum tank- I'm willing to bet you'll find much more enjoyment out of that compared over weighting. Lastly, you could always try doing the maneuver upside down... that's the only way I can do the skill with a steel tank while not carrying extra weight. It's also quite fun to do when performing a deco (or safety) stop. You'll get quite a few interesting looks...
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