I'm a newbie who tried a BP/W for the first time today...

[eelnoraa]

She also was just thinking that I may prefer an aluminum plate just based on my build and her experience with people of my size. She didn't recommend a 40lb wing at all though and said in her 8 years of diving with people using BP/W, only 1 person has ever needed one and he was a really big guy.

I don't see how human body size can play a role in plate material or wing lift. Plate material should be determine by the ballast you need. If you need a lot of ballast, SS plate help to remove some lead. Wing lift is largely a funciton of suit you use and amount of gas you are carrying. You yourself shouldn't play at role at all because your self buoyancy really don't change throughout the dive. Wing left or BC is there to compensate things that changes in buoyancy.

The thing that confuses me is if you were slightly negative at the surface, your negative buoyancy will only increase as you descend. If your wing is full at the surface, your wing cannot hold any more air so how can you have neutral buoyancy at depth. In theory, you will only continue to sink.

Not sure where you live but I would try a different BPW for comparison.

Why?? if he is in t-short, where can he lose buoyancy? If anything, he will gain buoyancy as his tank empties.

 

[eelnoraa]

I think Scubapro backplate itself is not outrageouly expansive. They are $160 on Amazon. Although it won't make practical difference, but Scubapro plates are very good quality. The plate finish, edge deburr are done much better than plate from DiveRite or DGX. Now, whether you want to pay for that is another story. But I do think if a product has better finish, more attention to detail, its manufacturing cost is higher, thus more expansive is not without reason.

Scubapro wing is a different story. I don't see its quality for design is any better, maybe even worse than other lower cost wing.

 

[dmaziuk]

Maybe saying the same thing but as you lose buoyancy, you are probably crawling on the bottom of the pool or kicking upward to stay off the bottom.

No. What I'm saying is if you're not wearing neoprene you have nothing that can just "lose buoyancy".

 

[SandyRobinson]

Why?? if he is in t-short, where can he lose buoyancy? If anything, he will gain buoyancy as his tank empties.

The diver has already lost buoyancy by being negative (albeit slightly) buoyant at the surface. As he descends, he will have to add air to his wing to keep from sinking more. If the wing is full and he trys to add air, it will leak out of the over pressure relief valve. You are not going to breathe enough air out of the tank in time to offset your descent.

 

[SandyRobinson]

No. What I'm saying is if you're not wearing neoprene you have nothing that can just "lose buoyancy".

Well it has been a while since I dove without at least minimal thermal protection.

 

[eelnoraa]

The diver has already lost buoyancy by being negative (albeit slightly) buoyant at the surface. As he descends, he will have to add air to his wing to keep from sinking more. If the wing is full and he trys to add air, it will leak out of the over pressure relief valve. You are not going to breathe enough air out of the tank in time to offset your descent.

Still, how does he get more negative? Wing is full, as long as he keeps the wing full, his over buoyancy won't change, which is a fixed negative value. Keep in mind, the assumption here is that there is no change in buoyancy due to exposure suit because he didn't use one. If he wear a wetsuit, then he will become more negative.

 

[SandyRobinson]

Still, how does he get more negative? Wing is full, as long as he keeps the wing full, his over buoyancy won't change, which is a fixed negative value. Keep in mind, the assumption here is that there is no change in buoyancy due to exposure suit because he didn't use one. If he wear a wetsuit, then he will become more negative.

My bad - see post 55

 

[jomaset]

a local shop that let me try out some gear in a pool today

I know this is an older post, but assuming it was some sort of "Demo Day," would it be incorrect to assume that maybe the wing had excess water in it? Assuming every dive will allow some water to enter the wing even under the best case scenario, many different people of differing skill levels using the same wing repeatedly could result in a waterlogged wing which would feel hard when filled to max pressure, but only having a percentage of the lift capacity. Just wondering. This explanation would validate everyone's facts/opinions from the student to the instructor as well as those of us who can't imagine how he could have been so negative.
Regardless, good luck to you on your quest for the right gear. You're in a great place for help and advice.

 

[Doby45]

Because water is neutral in water. As he added more air it would displace the neutral water from the wing with air from the inflator hose.

I know this is an older post, but assuming it was some sort of "Demo Day," would it be incorrect to assume that maybe the wing had excess water in it? Assuming every dive will allow some water to enter the wing even under the best case scenario, many different people of differing skill levels using the same wing repeatedly could result in a waterlogged wing which would feel hard when filled to max pressure, but only having a percentage of the lift capacity. Just wondering. This explanation would validate everyone's facts/opinions from the student to the instructor as well as those of us who can't imagine how he could have been so negative.
Regardless, good luck to you on your quest for the right gear. You're in a great place for help and advice.

 

[jomaset]

Ok, that makes sense. So as long as the power inflator is adding air (ie all is working as it should), a waterlogged bc is not a possibility. Not arguing, just trying to confirm my understanding.