Question about “balanced rigs” and having all ballast unditchable

[2airishuman]

I too am a solo diver who places great faith in things like physics and accident reports.

It is my perception that few (if any) fatalities are averted by ditching weight. In fact, it is my perception that it is rare that any diver ditches weight intentionally in an actual emergency.

Here's why. The only circumstances where ditching weight is a wise choice is when a diver is at the surface and is having trouble staying there. Usually that happens with newly minted divers who are panicking, and they can't ditch weight any more effectively than they can inflate their BC. An experienced diver unable to stay at the surface has other things to try, and usually won't ditch because it's expensive and a hassle to replace integrated weight pouches.

I use a weight belt and typically carry some ditchable weight however it is under my crotch strap and won't come off in one motion the way I was taught. There are some dives where I am properly weighted without adding lead. I avoid configurations where I am overweighted without adding lead but if it is just by a pound or two I'll do it.

I don't believe that, in my particular situation, having ditchable weight contributes to safety.

 

[MichaelMc]

I actually started diving without ditchable weights before I became a tech diver. There are recreational BCDs with trim weight pockets that can be used to replace weight belts. The Scubapro Hydros is such a BCD. In terms of recreational diving, better trim leads me away from weight belts.

This is where I see the issue occurs. In a pure OW single tank NDL setting. Wanting better trim moves more of the weight away from the standard ditchable locations.

I very much like ditchable and on body, the original balanced, but if you want trimmed out as well you need any on rig weight rather high, like shoulder area, and that is not easy on most BCs.

 

[lowviz]

I too am a solo diver who places great faith in things like physics and accident reports.

It is my perception that few (if any) fatalities are averted by ditching weight. ...//...

Ah, a reasoned rebuttal from a highly qualified source.

I accept your stance on this.

But consider a progressive and incremental abandoning of core degrees of freedom in order to preserve life. I am most interested in your thinking. Can you elaborate on the 'spin down' towards meeting one's creator in person?

 

[CT-Rich]

I actually don't make the assumption that there will always be air in my tank. That is why I practice valve shut down when I practice switching to my pony.

Perhaps can convince @CT-Rich that a tank can fill with water.

That wasn’t an o-ring. And yes, you shut the tank down with a blown ring. That was a pretty impressive blowout. I thought it was interesting he was going to 180 fsw with a13 ft3 pony, at that depth it would’ve the equivalent of breathing off a spare air.

 

[Eric Sedletzky]

Look at the video of a first stage o ring failure. The diver shut down the tank when switching to his pony at 1:51. I believe the reason for shutting down is to prevent water displacing air in the tank thereby making the tank quite negatively bouyant. You are at liberty to believe that a tank will not fill with water if the tank O ring, tank overpressure disc, or regulator first stage o ring fail.

Was that Dumpster diver?
I saw “Fife” written on the SMB

 

[CWK]

That wasn’t an o-ring. And yes, you shut the tank down with a blown ring. That was a pretty impressive blowout. I thought it was interesting he was going to 180 fsw with a13 ft3 pony, at that depth it would’ve the equivalent of breathing off a spare air.

I thought that was a first stage o ring. It was certainly a first stage failure of some sort since the valve shut down sorted it out. If it had been a tank o ring or tank overpressure disc, I think the tank would probably have filled with water.

A spare air is 3 cu ft, so 13 cu ft has a little more gas.

 

[lowviz]

@Eric Sedletzky, Yes, I think so. I dive DD's SP Classic and @2airishuman is no stranger to him either. I also dive your old #10. She never looked better.

Times change on this board, we deal with it...

 

[CWK]

Was that Dumpster diver?
I saw “Fife” written on the SMB

Not certain but I think it was DD.

 

[CT-Rich]

I thought that was a first stage o ring. It was certainly a first stage failure of some sort since the valve shut down sorted it out. If it had been a tank o ring or tank overpressure disc, I think the tank would probably have filled with water.

A spare air is 3 cu ft, so 13 cu ft has a little more gas.

It looked to me like a large portion of the first stage blew off. I am not super familiar with the Zeagles, so I’m not sure what happened. I thought it was a component failure. If the burst disk went it would drain completely. It would take a loooong time to fill a tank, since an Al80 has valve opening the size of a coffee stirrer and air needs to escape through the same opening the burst disk is even smaller

A SpareAir holds 3 ft at the surface, the 13 ft tank has an effective volume 2.2 ft at 180 fsw.

 

[CWK]

It looked to me like a large portion of the first stage blew off. I am not super familiar with the Zeagles, so I’m not sure what happened. I thought it was a component failure. If the burst disk went it would drain completely. It would take a loooong time to fill a tank, since an Al80 has valve opening the size of a coffee stirrer and air needs to escape through the same opening the burst disk is even smaller

I had another look at the video. Yes, it does look like a portion of the first stage blew off.

A SpareAir holds 3 ft at the surface, the 13 ft tank has an effective volume 2.2 ft at 180 fsw.

I look at effective volume based on average depth since one would be heading to the surface, not staying at max depth. So given max depth of 60m, the 13 cu ft tank is effectively 3.25 cu ft based on an average depth of 30m.

Spare air is for recreational, so assuming 40m max depth, it would have effective volume of 1.0 cu ft based on an average depth of 20m.