Quick Disconnect on Octo / SafeSecond reg?

[MaxTorque]

Ok, one of those "how long is a piece of string" type questions where there is probably no right/wrong but lots of shades of grey, type questions.

For cold water diving i was planning in using a full face mask (usual caveats apply, this is not a thread about FFM vs halfmask+reg btw!!) and for convience that FFM has a lockable Quick disconnect in the IP hose that runs to it. this allows:

1) the (bulky) mask to travel and be packed seperately to the reg set and gauges
2) the mask to be donned/doffed without the scuba unit, or vise versa,
3) allows the scuba unit to be taken off with the mask still on on the surface if necessary or for egress etc(using the surface BV if floating around)

As a result of the FFM, the conventional safe second/octo is on a longer (1.5m) hose, in a recreatonal type position and used with a secondary donate airshare system. Careful hose routing and management stops it flaping round the place.

So (finally) to the question:

Given the presence of the QD on the FFM, does it make any sense to have a matching QD on the octo/safesecond?

My thoughts so far:

Positives:
1) Would allow me (theoretically) to swap to the left post backup 1st stage whilst still wearing the FFM, potentially avoiding a bailout into my spare half mask
2) Would allow me to buddy airshare with a FFM buddy if they have the same QD on their FFM, again without mask removal

Negatives:
1) More potential failure points
2) Potential for inadvertant disconnection (QD's are locking type however)
3) Any QD swap in bulky gloves could be actually quite difficult in reality, especially with cold a hands and other events
4) adds weight to the rig (not much compared to the weight of the unit) and to the safesecond (potentially less comfortable to keep in mouth, whereas the FFM needs a bit of negative buoyancy to offset it's greater air volume)


What do people think? It feels to me a bit like the major positives would be so unlikely to occur, and occur without any of the negatives that this is not actually good idea?

 

[grantctobin]

Why is this in the technical diver forum?

 

[MaxTorque]

Er, because it's a fairly technical question, outside of Rec diving (Twinsets, FFM etc?)

if it's in the wrong place, the mods can happily move it to anywhere they see fit


(or does mentioning a fully face mask in a technical forum mean instant death??? lol)

 

[kensuf]

No, don't do it.

First off, just because someone else has a QD, that doesn't necessarily mean theirs is going to mate with your QD. I've seen multiple QD's that were machined just slightly different (typically a longer nipple on the male side) that couldn't connect, a friend of mine nearly drowned as a result of this.

Second - if I understand correctly, your thought process is if there's a problem with the second stage on your FFM, by having a matching QD you can unplug your primary and plumb in a secondary and go about your way. If I also understand correctly, the reasoning behind doing this is because you're worried about doing a mask swap.

1. There's only one real diving emergency, out of air, everything else is a problem.
2. When you need air, you need it NOW. There's zero time to be fumbling around unplumbing / replumbing QD's.
3. If bailing out to a mask is a serious concern for you, then I would take that to mean you are not really comfortable in the water. Instead of trying to come up exotic (and possibly dangerous) solutions to simple problems, why not spend time working on your comfort level in the water? Practice doing mask swaps, breathing without a mask, etc.

Best of luck to you.

 

[MaxTorque]

All valid points, however i have no issue bailing into a half+reg, and that would always be my first choice (and is something i practice a lot, and ensure any buddies are aware of before the dive to ensure THEY understand the differences in the buddy share situation.

No, the idea came simply as a way to add more potential options in any given situation, even if that option was not the first option so to speak. My concern is certainly similar to yours, in that what situtation would actually warrant such a swap (QD to QD) and how practical would that swap actually be, especially in thick gloves, where im (mostly) certain that doing a mask swap is more easily achievable than a QD swap, despite the temporary loss of sight during that process.

It may be that a gas switch block allowing a "seamless" swap between the different posts on my manifolded twinset is actually a much better idea, allowing the FFM to draw gas from either side?

 

[grantctobin]

All valid points, however i have no issue bailing into a half+reg, and that would always be my first choice (and is something i practice a lot, and ensure any buddies are aware of before the dive to ensure THEY understand the differences in the buddy share situation.

No, the idea came simply as a way to add more potential options in any given situation, even if that option was not the first option so to speak. My concern is certainly similar to yours, in that what situtation would actually warrant such a swap (QD to QD) and how practical would that swap actually be, especially in thick gloves, where im (mostly) certain that doing a mask swap is more easily achievable than a QD swap, despite the temporary loss of sight during that process.

It may be that a gas switch block allowing a "seamless" swap between the different posts on my manifolded twinset is actually a much better idea, allowing the FFM to draw gas from either side?

A switch block is at least as bad an idea as what you outlined in the first post, if not far worse. Also, a manifolded twin set is already drawing gas from each tank.

Why do you feel the need for a FFM?

 

[MaxTorque]

see first post please regarding discussion of half vs FFM - we can do that on a different thread if necessary ;-)


Why is a GSB so bad?

a manifolded twinset has two posts that can independantly draw gas from either tank, but each 1st stage attached to those posts can only draw gas from their own post, so a failure in a 1st stage means the second stage attached to that 1st becomes potentially un-useable. This is especially the case for a run-away IP situation in the 1st that then blows the 2nd into freeflow as the IP climbs! Ok, a freeflow in an FFM is (slightly) easier to deal with than with a std reg, but the ability to shut down the post, and swap to the backup post, but stay in the FFM could (note could, not would, or will) be a usefull capability, as long as the positives significantly outweight the negatives for that capability

 

[davehicks]

I use an omni-swivel high flow QD for my off board gas on my rebreather. If installed, used, and maintained properly these are robust and will not disconnect in an unplanned manner. They are not so easy to connect to a pressurized line with heavy gloves on. I always depressurize first.

However, I've had three of these Quick Disconnects fail in about 1,000 dives.

1. Jammed and stuck
2. Fell apart after sticking
3. Would not pass gas once connected

I always carry a spare QD now. I have gotten more diligent about disassembling and cleaning them on a yearly basis.

 

[rjack321]

It may be that a gas switch block allowing a "seamless" swap between the different posts on my manifolded twinset is actually a much better idea, allowing the FFM to draw gas from either side?

And your plan when the switch block or the hose from the block to the FFM fails?

There is a reason the left post is completely separate from the right on a twinset with an isolator in between. You are negating the whole point by plumbing both sides into a switch block. And seem to really want to make this complicated with 3+ different ways to get gas.

If the FFM fails you take it off and switch to an alternate - that's it, period, you're done

 

[MaxTorque]

I use an omni-swivel high flow QD for my off board gas on my rebreather. If installed, used, and maintained properly these are robust and will not disconnect in an unplanned manner. They are not so easy to connect to a pressurized line with heavy gloves on. I always depressurize first.

However, I've had three of these Quick Disconnects fail in about 1,000 dives.

1. Jammed and stuck
2. Fell apart after sticking
3. Would not pass gas once connected

I always carry a spare QD now. I have gotten more diligent about disassembling and cleaning them on a yearly basis.

Yes, i carry spares of this part for this very reason, and indeed a regular service and refresh is a very good idea, esp in a saltwater environment.

I also take you point and agree about the IP pressure connect loading/force on the QD, which are significant, and i could see that making an u/w swap difficult, espically in gloves and when otherwise task loaded