Yet another weight calculation question

[Painter]

I decided to try and work with OBC again. This time I started with a 0 value for personal buoyancy, which gave me a suggested lead value of 16lbs. On my last dives 12lbs was just about right, so I adjusted the personal buoyancy value until I was given a result of 12lbs.

I'll be doing my next dives in March with a new wetsuit so I will be very interested to see how OBC's suggested weight (20lbs in a new 5mil fullsuit) matches reality.

 

[KenGordon]

I am deeply sceptical about any mathematical approach to determining weighting without actually getting wet. Given you are in NY State I assume you are not going to get in the sea locally, but can you get in a pool? If so you can do a proper weight check adding and removing weight a little at a time.

A proper weight check is done at last stop depth, so ideally 3m, and is about only just being able to stay down with a nearly empty cylinder. It certainly does not involve being at the surface with some random part of the top of your head exposed.

Once you have a pool, fresh water, weight add 3% of your total weight, I expect of everything you took in the water. That weight was the weigh of displaced fresh water, the sea water will be 3% denser.

You will always be overweighted on a real dive. You will have more gas and if wearing a wetsuit it will be more compressed than when you did the weight check. Being a couple of kg over is not at all the end of the world, obviously though you don’t want to be both over weight because of gas and wetsuits compression and a couple more on top as eventually it will impact on your control.