Question Redundancies

[grantmac]

You really shouldn't be making any dive decisions with RBT/GTR. You should have a rock bottom pressure and making decisions based on that.

 

[Belzelbub]

Not dive time... RBT - Remaining Bottom Time. That counter is based on air consumption and when the access to the air is lost... that timer more or less resets.

So yes.. the overall dive timer continues but the RBT gets flaky.

OK. That makes more sense. My Oceanic had something like that. I believe they called it DTR (Dive Time Remaining). It would display whichever was less between NDL and gas time remaining. I can't recall what would happen if Comms were lost. Current dive computer has separate counters. One for NDL, one for GTR. If Comms were lost for a significant time, I believe it will blank out the GTR, and replace with "wait" for a bit until it gets a feel for breathing rate.

It doesn't actually reset GTR, but if it was constantly losing Comms, then I could see that as annoying. It shouldn't constantly be losing comms, though.

 

[tursiops]

This post is a probably useless attempt to correct some misconceptions.
Never the less....

My wife struggled with this concept when she was a new diver. It seems that OW instructors are maybe putting a bit too much emphasis on safety stops, to the point where new divers think that they are required. They, absolutely, unequivocally, are not! They are highly recommended, but not required.

Depends on how you are diving and on the country you are in and your dive operator. For example, the PADI RDP table has mandatory safety stops if you got to 100 ft or are close to your NDL. Caymans used to require safety stops on all dives, but now it is just many Cayman operators that have you sign a waiver that says you WILL do a safety stop on every dive.

What happened to "Follow your smallest bubbles"?

A little research showed this was a terrible idea, and still is. Really small bubbles rise very slowly, much too slowly, some mm/s (i.e., maybe 1 ft/min). For reference, 30ft/min is 15cm/sec, and that is maybe a 2mm bubble, but it varries with temperature and viscosity. So, no you do NOT want to go up at the speed of your smallest bubbles, but maybe your 2mm bubbles is OK. Good luck with that.

And if you're within your NDL (this is a basic forum) a 15' stop is not mandatory.

Depends. See above.

The other was my Apple Watch where the Oceanic+ app decided to wet the bed. Apparently the issue I encountered is a very common issue that Oceanic has yet to really fix. Apple wants to point at Oceanic and Oceanic wants to point at Apple. I just wanted it to work.

You don't like technology. We get it. But the PPS transmitters were developed over 30 years ago; they just work. Much of the bad-mouthing of transmitters and AI has been for Suunto and ScubaPro transmitters. Details and facts mattere.

At least three times my scubapro G3 lost access to the transmitter.

See above.

I prefer the simplicity of the PPS version (Oceanic, Aqualung, Shearwater, Sherwood…) to some of the others. They turn on when pressure is detected, and turn off when it drops below 50psi. Other brands require pairing, selecting channels, go into sleep mode if not enough pressure change is detected. All of that adds complexity, and for what gain?

BullsEye.

Anyway, He said with confidence that one failure that has ended more dive trips than anything else in his experience was air-integrated computers

WHICH AI computers? I'll bet they were NOT PPS-based. Anyway, why would that end a dive trip? A single dive, yes, but not a dive trip. You replace the transmitter, or the battery, or put an SPG hose on....

Also... one of the nice "features" of a computer is the computed bottom time. Near as I can tell with most of the computers out there if they lose comms the bottom timer becomes useless per their instruction manuals.

See below. What is meant here is gas time remaining, maybe. Some comnputers look at gas time remaining and NDL, and display the smallest number...."BT remaining." BAD IDEA. Much better just to display both, since NDL is already being displayed, so you can see computed Gas Time Reamining and NDL, and easily see which is smaller.

So for right now... I am diving with my apple watch ultra2 w/Oceanic on my left hand, my G3 on my right and a console.

On your wrist is new, unproved, and somewhat unreliable technology. You are correct; don't trust it.

It does continue to count bottom time... but the timer restarts. I will try and find the section that explains it.

See below.

Not dive time... RBT - Remaining Bottom Time. That counter is based on air consumption and when the access to the air is lost... that timer more or less resets.

So yes.. the overall dive timer continues but the RBT gets flaky.

"That timer more or less resets" is highly unlikely. The ScubaPro RBT is a terrible idea anyway. Don't use it.

 

[AsherN]

I would agree that buying into a single ecosystem was a concern. The FPFL does seem to be a benefit and I agree.. the shops will charge for labor... they just don't charge for the replacement parts (if needed).

Some of the challenges I've seen when buying local is a lot of shops don't tend to carry a plethora of brands. I like the HOG/Edge stuff... but the only shop in town that sells it is not super reliable.

The shop I work with the most is a ScubaPro shop.

The advice is always to buy stuff you can get serviced locally. Preferably by from your LDS. You want them to stay in business.

 

[AsherN]

Not dive time... RBT - Remaining Bottom Time. That counter is based on air consumption and when the access to the air is lost... that timer more or less resets.

So yes.. the overall dive timer continues but the RBT gets flaky.

RBT/GTR is a nice display. But never rely on it. The only time I'd pay real attention to it is if ever get close to TTS. You could be fine and then have to fin against a current. That will drop your GTR.

You dive what you are comfortable with. But transmitters are a lot more reliable than they used to be. Simple instructions like have the transmitter on the same side as the computer helps. Putting the transmitter on a short (5-6") hose helps eliminate your neck from line of sight. And generally, a transmitter will fail completely. It's a piece of electronics. It's on or off. As others have said a SPG can fail by not showing pressure properly. And if you a) don't have a handle on your air consumption, and b) don't look at the SPG regularly, it may suddenly show more air than you really have. If you really want redundancy for gas, get a j-valve. They were foolproof. Can't breathe? pull the rod and you have 500-600 PSI left, time to go up.

 

[Subcooled]

So to ME... it seems like a 2 gauge console is sort of a no-brainer.
I did get a computer with air integration but I still also ordered the console.
Am I overreacting?

Anything else anyone carries "backups" for?

What I would recommend is
1. two sources of breathing gas
2. two means of regaining neutral buoyancy (don't sink!)
3. two means of reaching the surface (lines, ropes, bottom crawling, compasses, optimal weighting, droppable weights, ...)
4. two means of doing mandatory decompression stops, if that's a thing for you

Some things can just be memorized - like the worst case decompression schedule.

 

[EFX]

What I would recommend is
1. two sources of breathing gas
2. two means of regaining neutral buoyancy (don't sink!)
3. two means of reaching the surface (lines, ropes, bottom crawling, compasses, optimal weighting, droppable weights, ...)
4. two means of doing mandatory decompression stops, if that's a thing for you

Some things can just be memorized - like the worst case decompression schedule.

I would modify the above table keeping in mind it is for new divers and want-to-be divers.

1. Two sources of gas. Your own tank with equipment in good working order and your buddies gas. Practice good buddy techniques and stay close enough to your buddy to be able to swim to him to get gas if needed.
2. Get properly weighted so in the case of a failed BCD or wing you can swim up to the surface. As a side issue get in proper trim.
3. See #2 and asking your buddy to help you get to the surface.
4. Forget deco diving. You're not qualified. It's more important to get experience and thereby getting comfortable under water. Always do safety stops at 15 ft for 3+ minutes even for shallow dives. This gives you practice for those mandatory deco stops should you ever become qualified to do them.

 

[Jai Bar]

Yes, you are overreacting. Having too much extra "redundant" gear can pose problems as well: not only bulkier and heavier, but if you already have pockets full with extra redundant stuff and also clip things on the various- extra redundant- drings so one looks like a diving Christmas Tree, then you are risking hazards, entanglement (let me guess- extra redundant cutting devices) and also task load. Imagine you really need one of these items in emergency, open the pockets and all the stuff (yeah, clipped, secured) bursts out and now you have to fumble to find it...

Also, having two conputers, for example, as an engineer you will find yourself puzzled as to which one you should believe...

It is ok to have spares and redundancies, but really take what you need. There is a huge difference between a Solo, Cave or tech diver vs. recreational going for a fun dive. Don't overdo redundancies, you are supposed to be able to finish a recreational dive without mask, computer, pressure gauge, or even without air, and you are probably aware that the vast majority if recreational divers don't go around with doubles, pony or even some tiny spare air bottles- they rely on buddy as redundant air supply and it is ok.