Question Redundancies

[went_postal]

Summary of prior threads:

• Modern transmitters are very reliable (moreso than SPGs in my case)
• Redundant pressure devices MAY allow you to continue the dive (however long that might be), but some failures mandate ending the dive (e.g., blown HP hose).
• If you have two devices, but rely on the most limiting, do you really have 2? Will you actually continue if that one fails?
• Having a spare SPG or transmitter in the SaveADive kit to swap between dives is smart.

In a recreational setting, a second computer is effectively insurance against sitting out a day from a multi-day trip. (You have to reset your tissues before a loaner/rental computer will make sense.) In rare cases of diving square profiles you could run tables with a depth gauge & console SPG (and timer), but that doesn't work well for the multi-level dives that are typical these days.

Personally, I run a transmitter with a spare SPG on the boat. I trust my Shearwater transmitter more than my SPG, and it also won't be misleading. (Some SPG failures will cause it to indicate more gas than is actually present.) I have 2 computers since I do technical diving, so bringing two on a multi-day recreational trip is an easy call for me.

My intent (for the moment) is to run my ScubaPro G3 and Apple Watch w/Oceanic+ App at the same time... I also have a console with the SPG and depth.

The G3 has the transmitter for air. So far my experience (limited) is that the Oceanic App and the G2 / G3 have been consistent for depth and whatnot.

 

[went_postal]

I have an SPG as well as an air-integrated computer on my wrist. I do have a much more conservative backup computer that I carry on some dives, but not all the time.

EDIT. My SPG was part of a console that had my conservative computer (not integrated) and a compass. I took apart that console and kept the SPG attached.

Part of my thinking (and I could be wrong) is just to have analog gauges in addition to the computers. I've seen digital consoles and I dunno... just having worked in the electronics/computer industry for 30+ years I don't know that I want to bet my life on them solely.

 

[Eric Sedletzky]

Part of my thinking (and I could be wrong) is just to have analog gauges in addition to the computers. I've seen digital consoles and I dunno... just having worked in the electronics/computer industry for 30+ years I don't know that I want to bet my life on them solely.

Just use a standard glass and brass 1-1/2" SPG clipped off on your left hip D-ring.
Get a wrist computer either with a built in compass, or a separate compass next to your computer. I put stuff my left wrist.
Use a 22" hose back up second stage bungeed under your chin and use a 40" length hose on your primary run under your arm with a 70 or 90 degree swivel.
Get a Scubapro MK25 with a G260 primary and an R195 for your bungeed backup.
Get a back plate and wing.
Do all this and you'll never have to reconfigure your setup or re-buy any of this stuff again.

 

[OTF]

Agree with the above.

If you want a reliable system with good redundancy look at how tech and cave divers dive, even in their recreational configurations. Basically, the "GUE/Hogarthian" setup with or without minor variations. Simple configurations with tried and true gear. It is the result of a lot of very smart people putting a lot of time into thinking about these things and analyzing lessons written in blood.

The best thing for true redundancy when the urine hits the space heater and your regs start blowing bubbles is a fully redundant dive system whether that's doubles, sidemount, a pony bottle, or a Y-valve with two regs on your single tank. When redundancy is called for in recreational diving I personally opt for a regular single tank on my back plus a slung (not backmounted) pony bottle.

Any of the simple brass-and-glass made-in-Italy gauges are good and come from the same factory. Piranha Dive MFG has the best price I've seen on them.

Sometimes but not always I will add a transmitter. It's convenient to only glance at one thing and the data can be cool but it's not necessary. Remember that the more things you add the more things can go wrong, so it's a fine balance. Not that adding a transmitter is a liability, but it is a couple more orings and a battery that can die. More stuff doesn't always mean more reliable - like if you were to dive two second stages plus an air2 you're just increasing the likelyhood of a reg (probably the air2) having a problem. That's why nobody does it. Simple reliable regs are good, the air2 is a cool concept but not known for simplicity or reliability.

 

[inquis]

just having worked in the electronics/computer industry for 30+ years I don't know that I want to bet my life on them solely.

If your computer or transmitter fails on an NDL dive, you're not going to die -- just end the dive.

 

[OTF]

If your computer or transmitter fails on an NDL dive, you're not going to die -- just end the dive.

This is important to consider when thinking about redundancies and contingency plans. Go over your gear piece by piece. Think about what can fail, how it can fail (failure modes), and how you would react to each failure. What just ends a dive? What can be managed underwater, and how? What is an immediate life threat? Then practice these failures and your reactions over and over in a safe environment.

 

[johndiver999]

Part of my thinking (and I could be wrong) is just to have analog gauges in addition to the computers. I've seen digital consoles and I dunno... just having worked in the electronics/computer industry for 30+ years I don't know that I want to bet my life on them solely.

For recreational diving, you should be able to survive the failure of ANY piece of gear. If you are not reasonably confident that this is true with your particular set of equipment, then you need additional training and/or a change in your configuration. This is not a flippant comment, it really should be a guiding principle in your diving as you move forward.

I pretty much always carry a pony bottle and a single, console mounted dive computer, compass and mechanical pressure gauge. I also wear a watch.

I've had my computer become unusable many times while diving. For recreational diving, this is more of an inconvenience than a significant danger. I think it makes more sense to concentrate any redundancy efforts towards risks that present significant dangers - such as air supply and a means of establishing buoyancy - those can kill you, not a loss of data.

 

[bradlw]

I ditched my console a long time ago in favor of a small "brass and glass" SPG and a wrist mounted computer.

I can remember at least three different dives when either my own or a dive buddy's computer failed, so my kit evolved to have two wrist-mounted devices. My computer and either a bottom timer or a computer (yeah, timer is obsolete nowadays but I still have mine and I like the simplicity of it)
I have some rollable plastic dive tables for air, EAN32 and EAN36 that I used to dive with always so that if I have to revert to the timer I would be able to figure out at least roughly how I'm doing.

As for other backups.
I dive with a line cutter z-knife + emt shears
I dive with a spare mask in a pocket
and on anything deeper than say around about 35-40ft I want my pony bottle
and I don't have my kit put back together yet, but for boat diving I plan on getting some sort of PLB or ELT + a signal mirror to back up my DSMB
and my DSMB has lift capacity and is my back-up for a failed BC (at least for some scenarios)
for night diving I always carried two lights

 

[jadairiii]

As other posters have related, if you are on a multi-day trip/vacation, nice to have a back up computer. That said, for the typical "day of diving", a simple brass/glass spg, and a automatic, self-winding mechanical watch (Seiko) on my wrist. You will always know your max depth (since this is a new diver forum), you could dive all day with just an spg, a watch and plastic tables.

They are hard to find now by Uwatec used to make a simple depth/BT, makes a nice backup.

 

[Eric Sedletzky]

"you could dive all day with just an spg, a watch and plastic tables."

Don't forget the depth gauge.