Soft weights write up (with pictures)

[FrogManMike]

By subtracting the weight of the water displaced by the sand or lead.

Sand only weighs about 1.92x as much as water of the same volume. When you put it under water, you subtract off the weight of the water it displaces (1.0), leaving only 0.92x/1.92x = 48% of the above-water weight to affect your overall underwater buoyancy.

Lead weight about 11.3x as much as water of the same volume. When you put it under water, you subtract off the weight of the water it displaces (1.0), leaving 10.3x/11.3x = 91% of the above-water weight to affect you overall underwater buoyancy.

10# * 91%/48% = 19#

As far as adding water to your sand (or lead) packets: if you are sealing them water tight, it helps to have the water in the packets displace the air, thereby avoiding buoyancy owing to air in the packets. However, that is no more effective than using cloth packet material that just lets the water flow in when you submerge.

If you only need a few pounds (diving without a wetsuit, or maybe in a 3/2 shorty, or in fresh water with a shorty), the sand will work just fine.

I use a 3MM shorty in salt water also and the sand works just fine there as well and I use 23 to 29 lbs of ballast depending on whether it is fresh or salt water.

 

[ept44]

wow thanks wjrussel for this amazing idea