Water as weight rather than lead?

[cool_hardware52]

I've often thought of depleted uranium for weights. I've dealt with that stuff and GEEEEZ is it heavy (dense). The problem is cutting the stuff. There really isn't a radioactivity problem, hence "depleted". A couple of pieces about the size of 2 "D" cell batteries would give you about 10 pounds of weight.

Depleted uranium has about twice the density of lead.

Boy you aren't kidding. Years ago, (durring a previous lifetime) I helped to build the gun range where they test fired the ammo for the A10. 30MM DU rounds. Well over 1000lbs per cuft. As I remember these rounds were about the size of "D" cells........

My guess is that quick trip to certain colorful middle eastern locales could yeild plenty of "D" cell hunks ready to use.


Tobin

 

[glbirch]

I've often thought of depleted uranium for weights. I've dealt with that stuff and GEEEEZ is it heavy (dense). The problem is cutting the stuff. There really isn't a radioactivity problem, hence "depleted". A couple of pieces about the size of 2 "D" cell batteries would give you about 10 pounds of weight.

Depleted uranium has about twice the density of lead.

'Depleted' means less radio-active than pre-processed ore, as there is less U235 in depleted uranium, but it is still slightly radio-active, with a really long half-life. IIRC the majority of radiation is alpha particles, which means you could have a problem if you inhaled/ingested/absorbed the stuff, but it's pretty safe to handle. Gets used as airplane ballast, radiation shielding, and in military grade weaponry.

So, a backplate of DU would weigh out around 15 lbs, and would stop anything short of an artillery round.

 

[glbirch]

Boy you aren't kidding. Years ago, (durring a previous lifetime) I helped to build the gun range where they test fired the ammo for the A10. 30MM DU rounds. Well over 1000lbs per cuft. As I remember these rounds were about the size of "D" cells........

My guess is that quick trip to certain colorful middle eastern locales could yeild plenty of "D" cell hunks ready to use.


Tobin

Why make a trip? I think the US Government gives the stuff away...

 

[Charlie99]

Overall though, the head of an old politician might work best. Most dense thing I can think of.

They must be the ones that need negatively buoyant Jetfins on their feet to balance things out

OTOH, airheads like me need a few pounds up high for trim.

 

[dweeb]

What really confuses things is that submarines take on water in order to become less bouyant and therefore "dive".

No, they ALLOW water to force AIR out of their ballast tanks.

Look, it's simple. Go review Module 1 of the PADI OW text.

 

[Charlie99]

If I replace my 10 pounds of lead with gold, how much less weight do I have to carry on the weightbelt?

Since lead has is 11.3g/cm3, in 4C fresh water (1.0g/cm3) 10 pounds of it will displace 10/11.3=0.88 pounds of water. In other words, 10 pounds of lead are 9.1 pounds negatively buoyant.

10 pounds of Osmium, at 22.5 specific density only displaces 0.44 pounds of water and delivers 9.6 pounds of negative buoyancy. So using even osmium as a replacement for lead only would allow me to drop about .44 pounds from a 10 pound lead weightbelt.

Platinum (21.4g/cm3) and gold (19.3g/cm3) are both much denser than uranium (18.7) and mecury (13.6).

As the saying goes, "Only strokes worry about costs", but I'll pick the inferior but cheaper solution in this case.

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The same diminishing returns apply to the choice of gas for filling a lift bag, since any gas is light compared to water.

 

[Diver0001]

And what happens if you change the volume of the flexible object with water instead of air?

You wouldn't get very far with that. The amount of positive buoyancy you create depends on the mass of the water displaced and both the volume and the mass of the object displacing the water.

This much should be clear.

If you use water to fill a BCD then you're displacing a certain volume of water (indeed increasing the volume of the diver) but you've taken on a mass of water equal to the volume you have displaced (increasing diver mass). Since you've done both, increasing both volume and mass with the same liquid you're immersed in, then your buoyancy won't change.

I hope that sounded logical.

The reason air works to create positive buoyancy is taht you displace a volume of water with something much lighter than water. My original comment assumed you were increasing the volume of the flexible container with air.

R..

 

[glbirch]

Since lead has is 11.3g/cm3, in 4C fresh water (1.0g/cm3) 10 pounds of it will displace 10/11.3=0.88 pounds of water. In other words, 10 pounds of lead are 9.1 pounds negatively buoyant.

10 pounds of Osmium, at 22.5 specific density only displaces 0.44 pounds of water and delivers 9.6 pounds of negative buoyancy. So using even osmium as a replacement for lead only would allow me to drop about .44 pounds from a 10 pound lead weightbelt.

Platinum (21.4g/cm3) and gold (19.3g/cm3) are both much denser than uranium (18.7) and mecury (13.6).

As the saying goes, "Only strokes worry about costs", but I'll pick the inferior but cheaper solution in this case.

19.3 (gold) vs 18.7 (uranium) is about a 3% difference? Pretty close in my books, especially given the respective costs.

The savings in my mind wouldn't be the amount of weight required (if you need 20 bls of weight, you need 20lbs of weight no matter what it's made of, with some minor variation as you've shown) but the size of the weights. Cutting the volume almost in half could increase comfort and reduce drag for those who require significant weight.

 

[wedivebc]

Since lead has is 11.3g/cm3, in 4C fresh water (1.0g/cm3) 10 pounds of it will displace 10/11.3=0.88 pounds of water. In other words, 10 pounds of lead are 9.1 pounds negatively buoyant.

10 pounds of Osmium, at 22.5 specific density only displaces 0.44 pounds of water and delivers 9.6 pounds of negative buoyancy. So using even osmium as a replacement for lead only would allow me to drop about .44 pounds from a 10 pound lead weightbelt.

Platinum (21.4g/cm3) and gold (19.3g/cm3) are both much denser than uranium (18.7) and mecury (13.6).

As the saying goes, "Only strokes worry about costs", but I'll pick the inferior but cheaper solution in this case.

-------------------

The same diminishing returns apply to the choice of gas for filling a lift bag, since any gas is light compared to water.

Are you suggesting to truly "do it right" one would need to use plantinum weights?

 

[The Kraken]

Originally Posted by Charlie99
If I replace my 10 pounds of lead with gold, how much less weight do I have to carry on the weightbelt?

On today's market? About $63,040.00.