DIR- Generic dual bladder wings...

[tursiops]

Historical note: I believe the original "prohibition" of "dual BDCs" is from the days when one actually wore two wings, one on top of he other. This is NOT the same in terms of drag or usage as a dual-bladder wing! Since the language and descriptors have changed, maybe the prohibitions ought to be brought up-to-date as well.

 

[PfcAJ]

Historical note: I believe the original "prohibition" of "dual BDCs" is from the days when one actually wore two wings, one on top of he other. This is NOT the same in terms of drag or usage as a dual-bladder wing! Since the language and descriptors have changed, maybe the prohibitions ought to be brought up-to-date as well.

An update to prohibit dual bladder wings as well as stacking wings.

Sounds good to me.

 

[bakodiver391]

Sure, but for 1000s of technical dives I'm surprised you to understand that swinging from neg too positive on a tank doesn't actually matter, for that matter some steel LP85's and HP133's do the same thing and there are some AL80s that end neutral to negative...

As I alluded to in saying that the buoyancy is in the bottom third of the tank, it is the change in longitudinal TRIM that I can't stand in ali tanks. There is a lot of metal in the dome and neck of an ali 80, much more so than a steel tank where the wall thickness is the same all over, and the neck is thin. An empty ali tank is buoyant in the base, an empty LP85 does not change trim. This change in TRIM could be deadly in a challenging penetration. My mentors had 15,000 dives, and I've never seen them dive with ali tanks.
My first several sets of doubles were ali, and I tried to like them. i even cast an hourglass shaped weight to fit between the tanks at the base, which fixed the trim problem, but begs the question" why bother to weigh these tanks down with a non-ditchable weight so that they perform like steel tanks, when the solution is to dive steel tanks?"

 

[inquis]

An empty ali tank is buoyant in the base, an empty LP85 does not change trim.

I can put lead on the tail of an AL tank to keep it from floating butt up on its own. Is there a difference in "trim" from an LP85 then?

I can also move that lead from the tank to somewhere on my person. Are things suddenly "broken" because the tank would float butt up on its own? Of course not, because it's the mass & volume distributions of the entire system that count (not an isolated tank on its own).

In other words, trim depends on the individual configuration. It's quite possible to have stable trim throughout a dive with an AL80 tank.

 

[crofrog]

An empty ali tank is buoyant in the base,

Are you talking about luxfer 80 or s80 or metal impact or Catalina s80 or C80? For the steel tanks are you talking about oms 85s, one of the 13 flavors of Faber 85s, or one of the Pst variants.


All of those above tanks have different trim and bouyancy characteristics. You dive the gear the gear doesn’t dive you.

As for the numbers of dives you or your mentors is an irrelevant appeal to authority, you’re demonstrating that you don’t fully understand the variables in the system.

 

[boriss]

I can put lead on the tail of an AL tank to keep it from floating butt up on its own. Is there a difference in "trim" from an LP85 then?

I can also move that lead from the tank to somewhere on my person. Are things suddenly "broken" because the tank would float butt up on its own? Of course not, because it's the mass & volume distributions of the entire system that count (not an isolated tank on its own).

In other words, trim depends on the individual configuration. It's quite possible to have stable trim throughout a dive with an AL80 tank.

You can certainly add weight to the bottom of the tank... or you can just get LP85's? Get the best tool for the job when there's a choice, no?

Comparison of what I was considering:

 

[bakodiver391]

Are you talking about luxfer 80 or s80 or metal impact or Catalina s80 or C80? For the steel tanks are you talking about oms 85s, one of the 13 flavors of Faber 85s, or one of the Pst variants.


All of those above tanks have different trim and bouyancy characteristics. You dive the gear the gear doesn’t dive you.

As for the numbers of dives you or your mentors is an irrelevant appeal to authority, you’re demonstrating that you don’t fully understand the variables in the system.

If your dive numbers are accurate, you're demonstrating that you drank the koolaid but don't know what's in it. The greatest names in diving are all wrong and you're right. Got it. Good luck in your diving career with an attitude like that. Signing off.

 

[PfcAJ]

If your dive numbers are accurate, you're demonstrating that you drank the koolaid but don't know what's in it. The greatest names in diving are all wrong and you're right. Got it. Good luck in your diving career with an attitude like that. Signing off.

I’ve got a “few” dives and I agree with crofrog.

Al80s, lp120s, and everything in between. It doesn’t matter. I dive the gear and I’m in control.

 

[inquis]

You can certainly add weight to the bottom of the tank... or you can just get LP85's? Get the best tool for the job when there's a choice, no?

My point was not to suggest one put lead on an AL tank. It was to illustrate the fallacy of thinking about the trim of a free-floating tank. "Best" depends on a lot of things, and AL80s have their place.

 

[bakodiver391]

Me and John Chatterton rocking LP85's in wetsuits, me with my bungied double bladder wing. The horror!, the horror!