Weighting Difference

[Mr Carcharodon]

I am headed out for a warm water vacation in a few weeks and an trying to sort out if I will have enough ditchable weight with a 6 pound steel backplate or if I should get an aluminum backplate.

How much buoyancy difference is there between a 7 mm wet suit plus a 4 mm hooded vest (California diving); and a 3/2 mm wetsuit (Florida diving)? I wear a medium size wetsuit.

In California I need about 17 pounds of ballast total to stay neutral. But 6 pounds of that (the backplate) is non-ditchable. And I would like to have 4-6 pounds of ditchable weight so I could get neutral if I had an equipment failure with a nearly full tank of air.

Thanks for your suggestions.

 

[vondo]

I am headed out for a warm water vacation in a few weeks and an trying to sort out if I will have enough ditchable weight with a 6 pound steel backplate or if I should get an aluminum backplate.

How much buoyancy difference is there between a 7 mm wet suit plus a 4 mm hooded vest (California diving); and a 3/2 mm wetsuit (Florida diving)? I wear a medium size wetsuit.

In California I need about 17 pounds of ballast total to stay neutral. But 6 pounds of that (the backplate) is non-ditchable. And I would like to have 4-6 pounds of ditchable weight so I could get neutral if I had an equipment failure with a nearly full tank of air.

Thanks for your suggestions.

One thing I was just reading: Neoprene has 2-3 lbs of bouyancy for every pound of neoprene. So, you could weigh it. The best way, though, is to fill a tub with water and see how much lead it takes to sink each of your suits.

 

[TimAZ]

One thing I was just reading: Neoprene has 2-3 lbs of bouyancy for every pound of neoprene. So, you could weigh it. The best way, though, is to fill a tub with water and see how much lead it takes to sink each of your suits.

Have to convert for the difference between fresh and saltwater though. Anyone remember the formula/values?:06:

 

[vondo]

Have to convert for the difference between fresh and saltwater though. Anyone remember the formula/values?:06:

I don't think you do. The total volume of the diver+suit system will be (basically) the same and the sw/fw difference comes from the weight of the water displaced by the whole system. I assume the cold water setup is also in salt.

Think of it another way. Sinking the suit, with its very small displacement, in fresh or salt isn't really going to matter much.

 

[ronbeau]

Have to convert for the difference between fresh and saltwater though. Anyone remember the formula/values?:06:

Salt water is approximately 2.5% more buoyant than fresh water.

Multiply by 1.025.

 

[Mr Carcharodon]

Have to convert for the difference between fresh and saltwater though. Anyone remember the formula/values?:06:

I think the formula is 2.5% of the total weight of the system. So if I just did the wet suit 2.5% of a heavy wet suit is still just a fraction of a pound. So you are probably right that checking the wetsuit in a swimming pool would be close enough.

I was estimating based on thickness that there would be a 8 to 10 pound difference in buoyancy. At the high end that does not leave much ditchable weight with a steel backplate.

 

[Charlie99]

Don't forget to take into account any difference in buoyancy of the tanks you use in California vs. whatever you will be using on vacation in Florida. If you are going from a steel tank to an AL80, that may be enough added buoyancy that you will have sufficient ditchable weight.