Buoyancy of fat?

[jeraldjcook]

I've been looking at buying my first tanks and everyone seems to say buy steel tanks since you can take lead off your belt. I'm sure we would all like to wear less lead. That being said, how would losing 10 lbs of fat (about what I would like to lose) change your buoyancy? Since fat is less dense than water, each extra pound you carry around means you need to carry a little more lead. Do you think losing 10 lbs of fat mean you could take 2 lbs off your belt? I tried searching and couldn't come up with anything. Anyone know the relative weight of fat in comparison to water?

 

[Charlie99]

I don't have the references at my fingertips, but IIRC fat is around 0.93 specific gravity. In other words, you lose one pound of bouyancy for approximately every 14 pounds of fat you lose. (I vaguely remember a variety of numbers for sp g of fat, and they were all between 0.9 and 0.95 -- in other words 1 pound of buoyancy for every 10 to 20 pounds of fat).

Of course, if you are losing weight because you are exercising, then in addition to losing fat, you are gaining muscle. So now you need to go find the specific gravity of muscle. It is about 1.06, so you get more negative by 1 pound of buoyancy for every 16 pounds or so of muscle that you add.

Or to put it another way, converting 15 pounds of fat into 15 pounds of muscle (keeping same body weight) will reduce your buoyancy by about 2 pounds.

 

[RICHinNC]

Not sure how fat works into the equation. I am definitely "cuddly" and my son in law is too. He floats like a dang cork....I sink like a rock. He uses 25 lbs in the ocean....I use 8 and I am over weighted. Go figure.

 

[Bill51]

I don't have the references at my fingertips, but IIRC fat is around 0.93 specific gravity. In other words, you lose one pound of bouyancy for approximately every 14 pounds of fat you lose. (I vaguely remember a variety of numbers for sp g of fat, and they were all between 0.9 and 0.95 -- in other words 1 pound of buoyancy for every 10 to 20 pounds of fat).

Of course, if you are losing weight because you are exercising, then in addition to losing fat, you are gaining muscle. So now you need to go find the specific gravity of muscle. It is about 1.06, so you get more negative by 1 pound of buoyancy for every 16 pounds or so of muscle that you add.

Or to put it another way, converting 15 pounds of fat into 15 pounds of muscle (keeping same body weight) will reduce your buoyancy by about 2 pounds.

Not that I know how accurate they are but the old numbers I have for specific gravity of body mass was fat was between .7 to .9, muscle was 1.08, and bone 1.9, so your estimate might be a little low.

 

[rookers]

Suppose you have an outboard motor weighing 300Lbs and displacing 2cf of seawater, how big a bag of fat would you need to make it slightly positively buoyant?

 

[Nautical Dreamer]

Take a look at this thread
http://www.scubaboard.com/showthread.php?t=151366&highlight=lead+lipids

 

[WarrenZ]

I know as I am losing weight I am using less weight but I also use less weight than my sister who is in better shape. I don’t think that there is any good formula that will help you just experimentation.

Loose all of the weight you feel comfortable with it will not only help to take lead off but it wont hurt your general health and air consumption rate.

My advice is try loosing some and see if you like the benefits you get.

 

[jeffrey-c]

I like to think of mine as "non-ditchable buoyancy"

 

[Nautical Dreamer]

Body shape has just as much effect on boyancy as does its density.

 

[MXGratefulDiver]

My fat body sinks like a rock ... go figure ...

... Bob (Grateful Diver)