Bill, we're all using and mix-matching the incorrect terminology here.
There is dry weight, and weight as in bouyancy.
Generally speaking, you can take off dry weight (lead) when switching from a stock BC to a Bp/W. This is because a stock BC is more positively buoyant than a Bp/W; due to fabric retention of air. Less fabric, less retention of positive bouyancy.
When switching from Al 80 tanks to St 80 tanks, you get to take 5lbs of dry weight off. Because Al 80's are 5lbs positively buoyant at 500psi, where as St 80's don't have this problem. So, sorry, I forgot to mention that in my original post. Even though both Al 80's and St 80s are 30lbs dry empty weight. You will wear 5lbs of dry lead for the Al 80.
However, with Al 63's and Al 50's, they only get (at most) +1lbs positive at the end, so generally you do not have to add extra weight for compensate for those Al tanks.
We cannot tell you how much dry weight you will get to drop if you switch to a Bp/W. It greatly varies; and honestly I think the majority of answers to that question are skewed here on scubaboard. Because I see more new divers posting their change over, and they might have been overweighted in the first place. That's just my speculation because most of my friends and I (differing body types and weight) only had to drop 5lbs at most when we made our switch.
Also, some BC models are just more buoyant than others. You may already be using a BC that's just not very buoyant by design.
Bottom line: way too many factors to give you an honest answer.
So there's really no set answer, as much as it's painful to not know. If you can get your hands on a Bp/W to borrow out for several dives, that will help out a lot.
I know Seven Seas rents out Scuba Pro Litehawks, which are very close to a Bp/W in terms of minimum fabric. In fact other than the Zeagle Express Tec, I think it's the closest thing to a Bp/W without being one that you could try.
There is dry weight, and weight as in bouyancy.
Generally speaking, you can take off dry weight (lead) when switching from a stock BC to a Bp/W. This is because a stock BC is more positively buoyant than a Bp/W; due to fabric retention of air. Less fabric, less retention of positive bouyancy.
When switching from Al 80 tanks to St 80 tanks, you get to take 5lbs of dry weight off. Because Al 80's are 5lbs positively buoyant at 500psi, where as St 80's don't have this problem. So, sorry, I forgot to mention that in my original post. Even though both Al 80's and St 80s are 30lbs dry empty weight. You will wear 5lbs of dry lead for the Al 80.
However, with Al 63's and Al 50's, they only get (at most) +1lbs positive at the end, so generally you do not have to add extra weight for compensate for those Al tanks.
We cannot tell you how much dry weight you will get to drop if you switch to a Bp/W. It greatly varies; and honestly I think the majority of answers to that question are skewed here on scubaboard. Because I see more new divers posting their change over, and they might have been overweighted in the first place. That's just my speculation because most of my friends and I (differing body types and weight) only had to drop 5lbs at most when we made our switch.
Also, some BC models are just more buoyant than others. You may already be using a BC that's just not very buoyant by design.
Bottom line: way too many factors to give you an honest answer.
So there's really no set answer, as much as it's painful to not know. If you can get your hands on a Bp/W to borrow out for several dives, that will help out a lot.
I know Seven Seas rents out Scuba Pro Litehawks, which are very close to a Bp/W in terms of minimum fabric. In fact other than the Zeagle Express Tec, I think it's the closest thing to a Bp/W without being one that you could try.
