Originally posted by wackodacko
sorry.. i dont understand.. only 50lbs will be positively bouyant and the rest is what? my body weighs 150..
Well, _you_ way 150 lbs on land, but that doesn't mean you'll be 150 lbs negative in water. Most likely with a wetsuit you'll need weight to make yourself negatively bouyant so you can sink.
Now your thinking "why would I ever need 50 lbs of lift?". Well, when you start getting into multiple tank rigs, where the difference between an empty tank and a full tank is 5-7 lbs, and you've got 4 tanks, that's 20-28 lbs you need to compensate for so you won't be positively bouyant at the end of the dive. In other words, to start the dive you _have_ to at least as negative as difference between a full tank and an empty tank.
There are other things that will make you more negatively bouyant at depth. Wetsuit 'squeeze' is another one. If you have a 2 peice 7 mil suit, it's not going to be 7 mil thick at 99 feet, since the air in the suit will compress, thus making it lose some of it's bouyancy. e.g. if you have a wetsuit that is 20 lb positive, and you take it down to where it sqeezes 50%, it's now 10 lb positive. So take that wetsuit with the above tank specs, and your looking at 30-38 lbs negative at depth with full tanks.
The lift of your BC needs to be able to take care of those differences.
Now to step back... for a basic recreational diver, you probably don't need to worry about the lift capacity of your BC.
