Failure points vs redundancy

[tursiops]

I carry a small light on all dives, even if I have no use for it, because I want it in case I am lost at sea and the search continues into the night. The cost and complexity of tucking a small light into the harness is minimal and for me, it has the right risk/reward ratio.

Great attitude!

 

[boulderjohn]

You use redundancies for situations that are potentially deadly. For contingencies that are inconvenient, then you should think hard if it is worth the trouble and/or added complexity.

For example, I generally always carry two cutting devices. The added clutter, complexity and expense of a second cheap knife on my harness (that is not THAT easy to access) is inconsequential.

But I remember a solo dive where I did not have a back up knife and a large fish wrapped me up (in 300 lb fishing line) and tied me to a shipwreck (after it knocked my mask off and regulator out of my mouth) and then I dropped the knife to the ocean floor below. I recovered the reg, reset the mask, vowed to always carry a second knife (if I lived) and then worked on the line and weaseled my way out of it and was on my way.

I have had my mask knocked off against my will so few times, that I have never taken a spare; but for a long time I dove with a marine radio in a canister, which was far more expensive and bulky than a mask, because for the dives I was doing at that time, the radio seemed like a good redundant rescue device (on top of a couple smb's).

I carry a small light on all dives, even if I have no use for it, because I want it in case I am lost at sea and the search continues into the night. The cost and complexity of tucking a small light into the harness is minimal and for me, it has the right risk/reward ratio.

Reading between the lines, I infer that you advocate using your brain to figure out what you need and don't need, depending upon the dive situation. That makes sense to me.

 

[Alekseolsen]

You can not continue that dive because you have no way of verifying that the spg actually works. You haven't looked at it in 150 dives, who knows if it's accurate.

Spg stays in the save a trip kit.

Not that hard to test? Necklace reg in month, close left post, breathe down reg, check SPG reads zero, open left post, SPG reads expected value --> WIN?

 

[Whitrzac]

Not that hard to test? Necklace reg in month, close left post, breathe down reg, check SPG reads zero, open left post, SPG reads expected value --> WIN?

All to avoid calling <1:500 dives?
I've had more SPG failures in 500 dives than transmitter failures.
And I dont even use SPGs on most of my dives...

 

[Alekseolsen]

All to avoid calling <1:500 dives?
I've had more SPG failures in 500 dives than transmitter failures.
And I dont even use SPGs on most of my dives...

No opinion on SPG vs AI (I only have SPG's), was just pointing out that checking out if the SPG is working should be trivial.
That said I never had an SPG fail in my 400 or so dives.

 

[NW Dive Dawg]

Need also to consider the impact of a failure, which depends on the kind of diving.

Bingo! For example, as a solo diver.... and in my opinion... the option of having a fully redundant gas delivery option outweighs the added or potential mechanical failure points of having that extra equipment.

 

[boulderjohn]

I've had more SPG failures in 500 dives than transmitter failures.

Wow! You must use some really bad SPGs.

I have never used a transmitter myself, but I have used many SPGs. On an OC technical dive, in fact, I might have a half dozen working on one dive alone, so my total SPG experience is many multiples of yours.

I have never had an SPG failure. I have occasionally had a spool give off champagne bubbles, but that's about it. I have never had any diver I have been with have an SPG failure, and again, I am talking many multiples of yours.

 

[grantctobin]

I might have a half dozen working on one dive alone, so my total SPG experience is many multiples of yours.

Might consider what kind of dives he’s doing before suggesting that. I don’t think he and I have done a dive with less than four each and that’s on the low end…

 

[tursiops]

Wow! You must use some really bad SPGs.

I have never used a transmitter myself, but I have used many SPGs. On an OC technical dive, in fact, I might have a half dozen working on one dive alone, so my total SPG experience is many multiples of yours.

I have never had an SPG failure. I have occasionally had a spool give off champagne bubbles, but that's about it. I have never had any diver I have been with have an SPG failure, and again, I am talking many multiples of yours.

And I've been using a transmitter (the venerable MH8A) or may 2-3 at a time for sidemount for a decade now (maybe 1500 dives) with no failures. Some dive buddies have had failures, but those were the early SWIFTs, or they didn't change their battery when they should have, or they were Suuntos. In that time, my wife has had the HP hose to her SPG split open, and I've had several SPGs that no longer return to zero when unpressurized.

 

[MB NZ]

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