Redundancy on twin sets.

[Caveeagle]

Thanks Caveegle

I was in a bit of a rush when I added the link yestaerday.. anyway, frog kick has a pretty decent guide for getting set up.

I will say that I am not a huge fan of hose routing they show in some pics. I don't like hoses to make a near 90* bend right off the 1stage. Most, or many modern 1 stages now have a 5th LP port and turret. For example, You can run your BC inflator from the 5th port on the primary (right side)first stage nearly straight over to the BC inflator. I also find the inflator hose provided with most wings is too long. A shorter 20" inflator hose makes for better routing (with my regs and size).

 

[teknitroxdiver]

Like this:

Instead of this:

 

[rhwestfall]

Here in our cold waters many of us don't subscribe to the "cross" of ds/lpi. In a help situation, it prevents you from being able to manage stress on the stage (breathing & inflation) as the second is being used by the other diver...

Whatever you choose, know what you dive....

YMMV

 

[stuartv]

It doesn't but it is recommended since you
Can only depend on yourself if you free flow or if a failure happens you can shut of one first stage and switch to the other
It's all about redundancy

I still don't see what a free flow or other failure of the tanks/valves/regs has to do with having a Hogarthian BCD. Nor how a Hogarthian rig is required or even recommended for solo diving. A normal integrated BCD, with a single tank and a pony bottle is a perfectly acceptable rig for diving solo.

There is nothing redundant about having a Hogarthian BCD. A Hogarthian BCD is so simple and robust, it really does not need redundancy. I.e. There is no need for a redundant waist buckle, or redundant D-rings, or redundant webbing.

In other words, you said:

...it's only safer if ... your rig is setup hogarthian style

and I think you are just muddying the waters, throwing in terminology that has nothing to do with this thread, possibly confusing things in the OP's mind or the minds of others who may read this thread later.

Your rig could have quick release buckles or padding or extra D-rings or any number of things that would make it non-Hogarthian and yet still be just as safe for diving solo with back mount doubles.

 

[RainPilot]

Hogarthian AFAIK describes more than just a harness and wing. It also includes things like the long hose, bungeed necklace etc.

I believe the intention was to describe the reg and hose setup.

 

[Littlerayray]

Having both your regs on seperate posted and separate stages is safer then having everything on one it would be the same as having a pony bottle if you shut the valve off on one reg you can still draw air from the other also you can shut off one reg and still use the air from both tanks or isolate you tanks in case of a catastrophic failure

 

[RainPilot]

I believe that having a manifold is a good idea if you really need to preserve gas in the event of a regulator failure. However if you don’t need that and are diving in a way where you can always come up on what’s left in one tank, then there is an argument in favour of independent doubles, keeping tanks balanced with switches between primary and backup regs.

That removes the (small) chance of a manifold failure which has the potential to lose all your gas.

 

[stuartv]

Here in our cold waters many of us don't subscribe to the "cross" of ds/lpi. In a help situation, it prevents you from being able to manage stress on the stage (breathing & inflation) as the second is being used by the other diver...

Whatever you choose, know what you dive....

YMMV

I'm not sure whether you are trying to support or give a contrasting point of view to the previous post(s).

What exactly do you mean by the "cross" of DS/LPI? I run my doubles just as shown in the top picture that @teknitroxdiver posted. Wing inflator comes across behind my neck, over my left shoulder and down my front. DS inflator comes down behind my left shoulder and around my chest. Is that what you mean by crossing? That the LPI is crossing from right post to left side of body?

Do you recommend having the wing inflator come off the left post and the DS inflator come from the right post?

Your concern is that, in a OOA situation, you would have the wing inflator coming from the same 1st stage as the reg that the "other" diver is breathing from? So, if you add air to your wing at the same time the other diving is inhaling, you could cause the 1st stage to freeze?

The concern I would have is that having the DS inflator come from the right post would mean that it is connected to the same swivel turret as the long hose. I don't see a way to do that where both hoses route well in both the normal positions and in a OOA situation, where the long hose is donated and the turret is swiveled to direct the long hose over your right shoulder, instead of under your right arm.

Also, it seems like, generally, if you get into a "situation", first, you would presumably be neutral or very close to it at the time. So, you probably wouldn't need to be adding air to your wing. So, the concern of adding air while the other diver is inhaling seems pretty low risk. Also, if you're really worried about that, you could just add a little air to your drysuit, instead. I mean, in that scenario, you shouldn't be needing to add much air to either, right?

I know I don't have the same kind of cold water experience that you do, so I'm really not trying to argue with you. Just thinking out loud, so to speak, as I try to understand all the subtleties of what you're talking about.

 

[barth]

I believe that having a manifold is a good idea if you really need to preserve gas in the event of a regulator failure. However if you don’t need that and are diving in a way where you can always come up on what’s left in one tank, then there is an argument in favour of independent doubles, keeping tanks balanced with switches between primary and backup regs.

That removes the (small) chance of a manifold failure which has the potential to lose all your gas.

It is not possible to lose all your gas because one manifold failure.

If you think it is possible, please describe in details which o-ring or whatever should fail to lose all your gas.

 

[RainPilot]

Is it not possible for the manifold valve knob to fail? Like I said, a small chance but I don’t use the word impossible when it comes to failure modes.

I am on the phone now so searching the Board is challenging but I seem to recall threads where people have broken manifolds on wrecks caves etc.