Dual bladder BCD 60 or 94 lb lift which one ?

[vinegarbiscuit]

DSS makes a very nice 38 lb doubles wing, which is in the 35 lb neighborhood, right? It's absolutely great. It provides me with enough lift to dive double Al80s while wearing a wetsuit (not my fave tanks, but when in Mexico...), but it's not outrageously huge. Having used a borrowed 60 lb wing with that same Al80 set-up, as well as with double steel 100s, I found the 'taco' effect to be a PITA. There's a lot of air sloshing around in a 60 lb wing, which moreover isn't instinctively easy to vent the first few times you dive it. It's certainly not impossible to accomodate - I eventually got used to it - but why make things harder than they have to be?

I found selytch's buoyancy calculator to be pretty handy (I think he/she revised it subsequently in that thread, so as an aside to the OP: do be sure to read all the way through it, if you haven't already done so), and it was a great graphic representation on how different gear configurations (exposure suit, tank selection, additional bottles) will affect wing lift requirements. Tobin of DSS (cool_hardware52) might also weigh in here - since he handles questions like the OP's on a daily basis, I'm sure his input will be extremely valuable.

 

[Jim Lapenta]

HOG also makes a 38 lb wing. It is designed for small to medium doubles. Dbl 40's, 72's, al 80's. I don't have on in stick right now but I have had some interest in an intro to doubles workshop I have been comtemplating so I may get one in for students to use with my 72's.

If you want to go with a 90lb wing that is up to you. One thing that is well known though is that OMS service has a reputation for sucking big time. Plenty of posts on here to that effect. If I had to go for a dual bladder wing ( no idea why that would ever happen a lift bag on the bottom of the plate, or in my pocket is more convenient and cheaper) I'd look at a Dive Rite Rec EXP or Classic EXP. They used to make what they called a Super Wing that was a double bladder. It was huge.

 

[Tortuga68]

These threads always go the same way: people post who have never used a bungeed wing regurgitating stuff they read on the internet - some of which is true & some of which isn't

Incidentally, how do dual bladder wings work? Does a 90# wing consist of two 45# bladders, or are the primary and redundant bladder each capable of 90#?

They're redundant bladders; so both bladders have the same lift ie 94# or 60# depending on the model

If you tear a wing, hydrostatic pressure will force air up and out, but you can position yourself such that it has no path to do so. This is sometimes demonstrated in tech courses by the instructor removing a student's rear dump. A wing with shock cord constraining its shape will in theory dump until the bungees are no longer loaded regardless of orientation

In theory... why don't you ask NetDoc, he's actually had a puncture in one

In selecting wings, I have to ask myself a question: on a dive where I need so much lift that the wing needs to be mechanically constrained, how much of it can I afford to lose in a failure?

As above, you're not losing any lift, since you have a redundant bladder

As vinegarbiscuit noted above, a 60# non-bungee wing (Halcyon Evolve for eg) will taco and have a lot of air shift. I know, I own one of them too

 

[Tortuga68]

HOG also makes a 38 lb wing. It is designed for small to medium doubles. Dbl 40's, 72's, al 80's. I don't have on in stick right now but I have had some interest in an intro to doubles workshop I have been comtemplating so I may get one in for students to use with my 72's.

If you want to go with a 90lb wing that is up to you. One thing that is well known though is that OMS service has a reputation for sucking big time. Plenty of posts on here to that effect. If I had to go for a dual bladder wing ( no idea why that would ever happen a lift bag on the bottom of the plate, or in my pocket is more convenient and cheaper) I'd look at a Dive Rite Rec EXP or Classic EXP. They used to make what they called a Super Wing that was a double bladder. It was huge.

Doing deco with a working wing is a lot easier than using a liftbag IMO

About the required lift, it's always brought up that "you only need X lift" for doubles with X being anywhere between 18 and 35# (diving wet/alloy tanks). My question is, since that's all you need, where are all the <38# doubles wings?

 

[fjpatrum]

Doing deco with a working wing is a lot easier than using a liftbag IMO

About the required lift, it's always brought up that "you only need X lift" for doubles with X being anywhere between 18 and 35# (diving wet/alloy tanks). My question is, since that's all you need, where are all the <38# doubles wings?

I actually asked the same question in some thread when I was trying to find a <20# wing since all I hear is "you don't need anywhere near that much lift" and similar statements. Tobin basically said that manufacturers are behind the curve with respect to wing size but there are more and more making smaller wings every year. That makes sense from typical marketing trends so I suspect we'll see a few more ~35# doubles capable wings in the next year or two.

 

[Doc Harry]

Since you asked....

1. Friends don't let friends buy anything OMS. If I won't let my friends buy OMS, then I certainly would not either. Their equipment is questionable in terms of engineering, and their customer service is downright abysmal. You might as well throw your OMS wing in the garbage is something goes wrong. I've not been able to get OMS to do any warranty repairs for me.

2. I dive twin steel 130s and only use a 55# wing. Why not use a 94# if you can? Dynamic instability, that's why.

3. There's no need for a dual bladder. It just makes it complicated, expensive, and there's more to go wrong. A 94# wing is ridiculous enough, but then add dual bladder.... JEEZ!

 

[Blackwood]

They're redundant bladders; so both bladders have the same lift ie 94# or 60# depending on the model

Thanks.

In theory... why don't you ask NetDoc, he's actually had a puncture in one

Is his single anecdote read on the internet okay to regurgitate, but a different single anecdote read on the internet is not? Eh, screw being argumentative. I'm of the opinion that there are useful things to be learned on the internet, just have to take what you read with a grain of salt and apply sense.

If I am squeezing my wing and open the dump valve, some air is going to come out. Bungees will do the same thing, until they are unloaded, or unless the wing wasn't full enough to load them in the first place.

When his punctured wing, were the bungees preloaded?

As above, you're not losing any lift, since you have a redundant bladder

That bit wasn't directed only at redundant wings; it was a general statement about buoyancy selection. I have redundant buoyancy in the form of a drysuit and/or bags.




... and why is this thread in Basic? Dives necessitating 94# of lift (or even 60#) are anything but.

 

[Tortuga68]

Why not use a 94# if you can? Dynamic instability, that's why

lol

There's no need for a dual bladder. It just makes it complicated, expensive, and there's more to go wrong

Not everyone dives dry. It's not complicated, it's not expensive and if "there's more to go wrong" was an argument then we wouldn't use redundant anything

Is his single anecdote read on the internet okay to regurgitate, but a different single anecdote read on the internet is not? Eh, screw being argumentative. I'm of the opinion that there are useful things to be learned on the internet, just have to take what you read with a grain of salt and apply sense

I wasn't regurgitating anything - I told you Pete had actual experience on the matter, and that you should ask him what actually happened, as opposed to what might happen "in theory"

 

[Blackwood]

I wasn't regurgitating anything - I told you Pete had actual experience on the matter, and that you should ask him what actually happened, as opposed to what might happen "in theory"

You misunderstand, I wasn't suggesting you were. I'm saying that - to me - his experience is just as anecdotal as the other one.

I also fully accept that my understanding and thus reasoning may be incorrect. Do bungees not compress the wing?

 

[Centrals]

I have been using OMS 60lbs bungee twin bladder for several yrs without any problem so far. The water in SE Asia is pretty warm most of the time and dry suit is NEVER an option.