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This may be a dumb ass question,or even asked before----
Is there a calculation to work out the bouyancy of body fat.
 

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loop14
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Yes. If you are a chuffer you need more lead!







or is it less lead? ;-)
 
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Nigel Hewitt
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This may be a dumb ass question,or even asked before----
Is there a calculation to work out the bouyancy of body fat.
Fat weighs 0.8Kg/litre so every extra 5Kg of fat contributes 1Kg of buoyancy.
Muscle is virtually neutral.

Is that what you wanted?
 

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Diving & deluded!!
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To be fair this is never something I'd thought to ask, and I've no doubt it makes a difference. My weight's been all over the place since I've started diving (and yes, I'm a girl. It happens!!).
 

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rEvolutionary Diving
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Depends how big it is, but it only really affects the placement of the pee valve ;)
And trim :)


Seriously though I float in fresh water at forehead level, I have more than my share of fat and I'm pretty negative. I also have a mate who's not got any fat that you can see and he pops about like a cork. I don't think bone will be negative so why don't I float well.

Do you think Sharon is feeding me mercury or lead?
 

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Body fat adds buoyancy. If you're a bigger person you need more lead. Also increased body fat leads to an increased risk of DCI. I' a lumpy fella myself :-(
 

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Nigel Hewitt
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What about bone?
So I went back to my wife's medical books and there's lots of stuff on 'Bone Density' but it's a special meaning of 'density'.

The best I can find in 'real physics numbers' is 1.6 to 1.9Kgs/litre where water is, of course, 1Kg/litre.
I'm not sure if the 1.6 figure is 'dry prepared' specimen and the 1.9 might be 'in vitro' to I'd tend to go with 2 ish.

Not many people grow much extra bone so it's probably not worth fussin' about. Fat on the other hand...
 

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Squidgey Member
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Tiz a question i have ponderd over from time to time.
Myself I am tall and thin with little to no fat and it realy pi$$es me off when only wearing a pair of shorts in the sea i still need 3Kg of lead to get my head under the water.:(
 

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Nigel Hewitt
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Myself I am tall and thin with little to no fat and it realy pi$$es me off when only wearing a pair of shorts in the sea i still need 3Kg of lead to get my head under the water.:(
That's right. People float.
Well they do until the pressure compresses them. I go negative at about 7 meters with a lung full of air wearing shorts, a low volume mask and a pair of fins.

The one big unpredictable in all this is a colon full of negative poo. However although a really good dump prior makes me feel more comfortable on a dive I'm not sure it's anything to do with my buoyancy... :)
 

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I am negatively buoyant when only wearing bathers. This caused great fun when told to do the floating exercise in my OW, as I went straight to the bottom of the pool and lay there. The instructor insisted that everyone is positively buoyant and that I was performing some sort of trick, I know that everyone else found it very entertaining, but there is no was that I would stuff a couple of kilos of lead up my arse just to get a cheap laugh.
 

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Squidgey Member
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That's right. People float.
Well they do until the pressure compresses them. I go negative at about 7 meters with a lung full of air wearing shorts, a low volume mask and a pair of fins.

The one big unpredictable in all this is a colon full of negative poo. However although a really good dump prior makes me feel more comfortable on a dive I'm not sure it's anything to do with my buoyancy... :)
Interesting. Are you saying that you are full of $hit???:D
 

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Devout Sceptic
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From personal experience I believe that there is a secondary consideration to carrying some extra blubber.

Last year I lost sufficient weight that I went from a large to a medium 5mm wetsuit. All my other kit was identical. I'm sure that affected my weighting as much as my lesser displacement did. There must be a significant difference in the buoyancy of the two suits. Small but significant.

Perhaps there is is similar consideration with dry suits?
 

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Doing it wrong since '94
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Interesting stuff. I am a right lard arse but I only need 1 lb in the pool to get comfortably negative and about 12lbs with full dry suit single 12 etc.
 

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I am negatively buoyant when only wearing bathers. This caused great fun when told to do the floating exercise in my OW,
I am slightly neg in trunks, I have to work really hard to float, the only way I can do it is to lie on my back taking Hugh breaths and pure focus otherwise down I go.
 

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A few years ago i lost about 2.5 stone working diving every day. My required weight diving didn't change at all.


...fast forward to this year and ive gained 2 stone in 3 months. Again though my lead requirements havent changed :)
 
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