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MxDiver
08-19-2007, 14:04
This commentary has come up a couple of times on other threads, so I like to know how some of you feel about this. In an exclusively recreational scenario, if your computer malfunctions do you consider your buddy’s computer a backup?

I think if is a single dive or the first one in a series (by first I mean the very first one of the diving trip, if over several days, not of the day) it could be ok. Other ways I don’t think it is.

ScubaToys Larry
08-19-2007, 14:28
It depends if you mean backup or back-up. If my computer goes out, and I don't have a backup, I am budding up, and then going up. I will hang with my buddy to make a nice slow ascent, then a good long safety stop, then to the surface.

That is my procedure - but I've never had to use it... never had a computer go out at depth.

MxDiver
08-19-2007, 16:47
I meant backup, it's been edited.

Suther2136
08-19-2007, 18:00
I gotta go with Larry. If your AI computer goes bye bye you have no tank pressure, time to go up.

BuzzGA
08-19-2007, 18:23
I might use a buddy's computer to double check a max depth (even though I have a computer I still wear a watch as a back up for time) but if I don't know how much air I have its to the surface I go

cummings66
08-19-2007, 18:52
I would refer to his for depth and time data, and the safety stop. It would not be my backup however because like todays dive I was 10 feet lower than my buddy because I had a 7mm on and he had a 3mm on. I was below the thermocline and he was above it. Quite a different dive profile.

Zenagirl
08-19-2007, 19:50
I agree, my buddy's computer is only a "backup" in the sense that it'll help make sure I get to the surface slowly enough. Also because I always dive with the same buddy, I know that I usually have at least 200psi more in my tank than him, so as long as he has enough air to do a long safety stop (we like to do 5 min stops), I know I have plenty as well.

Buoyant1
08-19-2007, 20:32
I'm not AI, so I'm not dependant on the computer for pressure etc... I can still use my buddies as a timer, and rely upon my gauge for depth...since I always back up with tables, I can keep diving.

deepdiver47
08-19-2007, 21:32
I always have my own backup computer as I dive with a Vyper and a Mosquito. Always think that you are solo diver.
I do 16-18 dives per week (when I dive that is) so I need to have my own backup based on a repetitive dive scenario

plot
08-19-2007, 21:40
purely recreational diving, i goto the surface if computer malfunctions. i'm not holding hands with my buddy the entire time so our dive profiles can be considerably different

Xspect
08-19-2007, 22:15
I'm using my buddies. since I mostly dive with my wife. But If I dove with someone else I would head for the surface

cummings66
08-19-2007, 22:21
since I always back up with tables, I can keep diving.

You may be able to do that right now, but as you dive and become better you will discover it's entirely possible for you to have bottom times on the computer that CAN NOT be done on a table. I do it quite often.

Now a wheel might be able to save your diving, but there is no way you can back a computer up by using square tables. Not if you have good air consumption rates and take advantage of them. If you look at the 4 dives profiles I posted in the Nitrox thread you'll see that by tables not only did I exceed my O2 clock by I think 25% I absolutely blew the tables out of the water so far the plastic card melted from the heat and if it could have talked it would have called for a chamber ride. 101 feet feet for 49 minutes is not on any table you can find. Without a computer to do the multilevel dive, or a wheel to plan the depths around that dive by itself would have been enough to send me home. It was 34% Nitrox if I recall correctly so the EAD would have been less, but still not on a table. The EAD is 86 feet, the tables turn black at 25 minutes. Lets see, 49 - 25 = 24 minutes longer than the tables allow. The tables say to stay at the safety stop for 15 minutes and then quit diving for 24 hours. That's why I say tables can not back a computer up. If you dive and use a wheel, and you keep track of your average depths on a slate, and you then use the wheel to figure your pressure groups you might. But to be honest, the only place I've seen a wheel has been hanging on a wall somewhere. Not one diver I've ever met carries the wheel and uses it. Not one. That's the only table close to a dive computer.

I hope you realize that if you use a computer you can do the same dive safely, but there is no square table around that will say it's OK to go diving again. Only the wheel could let you dive again after that dive profile. Yes, it was safe according to the wheel, but not per the RDP.

subsur
08-20-2007, 11:27
the "textbook" answer is NO, you should either have yourown computer or use tables and never rely on your buddy. however, the reality is often different. as long as you have your own SPG and have very similar dive profile as your buddy (meaning sticking together), i see nothing wrong with using his/her computer. assumption is of course that the computer is reliable and you use your common sense as well (in case computer malfunctions).

CompuDude
08-20-2007, 15:02
The textbook answer is indeed no.

The real world, as always, is more complicated, and depends on the exact circumstances.

If a computer dies during a dive, it's time to thumb the dive, unless you happen to have a spare computer on your person or your dive times are still within table limits and you have a way of tracking time, depth and pressure.

I've shared a computer before, when I managed to forget my computer at home. Was it smart? Not really. In that case, however, it was an easy recreational dive where you needed a shovel to dig deeper than 45 feet, so I could have just as easily dove tables, since at the depths we spent most of our time, there's no way we could have passed the NDLs with the one tank we had. For multiple dives, however, I opted to pass that day.

Multiple and deep dives are where sharing computers can get you into real trouble. Single shallow dives, well, again, you may as well dive tables, so it doesn't really matter as much as long as you can track time and depth (and air pressure).

cgvmer
08-20-2007, 15:13
If you have a pressure gauge, a timer and depth guage yes...otherwise no.

Buoyant1
08-20-2007, 19:55
purely recreational diving, i goto the surface if computer malfunctions. i'm not holding hands with my buddy the entire time so our dive profiles can be considerably different


I agree with that...our depths are always a bit different at the end of a dive...he tends to hang at the bottom, I'm usually slightly above, and our average depth is always a few feet different.

Quote:
Originally Posted by Buoyant1 http://forum.scubatoys.com/images/buttons/viewpost.gif (http://forum.scubatoys.com/showthread.php?p=28988#post28988)
since I always back up with tables, I can keep diving.

You may be able to do that right now, but as you dive and become better you will discover it's entirely possible for you to have bottom times on the computer that CAN NOT be done on a table. I do it quite often.

Now a wheel might be able to save your diving, but there is no way you can back a computer up by using square tables. Not if you have good air consumption rates and take advantage of them. If you look at the 4 dives profiles I posted in the Nitrox thread you'll see that by tables not only did I exceed my O2 clock by I think 25% I absolutely blew the tables out of the water so far the plastic card melted from the heat and if it could have talked it would have called for a chamber ride. 101 feet feet for 49 minutes is not on any table you can find. Without a computer to do the multilevel dive, or a wheel to plan the depths around that dive by itself would have been enough to send me home. It was 34% Nitrox if I recall correctly so the EAD would have been less, but still not on a table. The EAD is 86 feet, the tables turn black at 25 minutes. Lets see, 49 - 25 = 24 minutes longer than the tables allow. The tables say to stay at the safety stop for 15 minutes and then quit diving for 24 hours. That's why I say tables can not back a computer up. If you dive and use a wheel, and you keep track of your average depths on a slate, and you then use the wheel to figure your pressure groups you might. But to be honest, the only place I've seen a wheel has been hanging on a wall somewhere. Not one diver I've ever met carries the wheel and uses it. Not one. That's the only table close to a dive computer.

I hope you realize that if you use a computer you can do the same dive safely, but there is no square table around that will say it's OK to go diving again. Only the wheel could let you dive again after that dive profile. Yes, it was safe according to the wheel, but not per the RDP.



I've only gone slightly into deco (no more than two minutes) using an entirely square profile twice, If it's something over the top, I would call dive number two in a heartbeat. In my regular quarry, I can almost tell you my multi-level profile because I've been through the area so many times...

My regular buddy is going for DM next year, and he HAS to learn the wheel...that's going to be fun!

coral-hugger
08-27-2007, 22:02
You may be able to do that right now, but as you dive and become better you will discover it's entirely possible for you to have bottom times on the computer that CAN NOT be done on a table. I do it quite often.

Now a wheel might be able to save your diving, but there is no way you can back a computer up by using square tables. Not if you have good air consumption rates and take advantage of them. If you look at the 4 dives profiles I posted in the Nitrox thread you'll see that by tables not only did I exceed my O2 clock by I think 25% I absolutely blew the tables out of the water so far the plastic card melted from the heat and if it could have talked it would have called for a chamber ride. 101 feet feet for 49 minutes is not on any table you can find. Without a computer to do the multilevel dive, or a wheel to plan the depths around that dive by itself would have been enough to send me home. It was 34% Nitrox if I recall correctly so the EAD would have been less, but still not on a table. The EAD is 86 feet, the tables turn black at 25 minutes. Lets see, 49 - 25 = 24 minutes longer than the tables allow. The tables say to stay at the safety stop for 15 minutes and then quit diving for 24 hours. That's why I say tables can not back a computer up. If you dive and use a wheel, and you keep track of your average depths on a slate, and you then use the wheel to figure your pressure groups you might. But to be honest, the only place I've seen a wheel has been hanging on a wall somewhere. Not one diver I've ever met carries the wheel and uses it. Not one. That's the only table close to a dive computer.

I hope you realize that if you use a computer you can do the same dive safely, but there is no square table around that will say it's OK to go diving again. Only the wheel could let you dive again after that dive profile. Yes, it was safe according to the wheel, but not per the RDP.


My regular buddy is going for DM next year, and he HAS to learn the wheel...that's going to be fun!Maybe it's just me, but the wheel actually seems easier for all but the simplest single dive case. Less fiddling around ... it's all right there. I wish they would teach that as an option in the PADI OW instead of the RDP table. And of course the wheel is better for complex cases and potentially more accurate.

Of course, have I ever used it on a non-training dive, no. But my comp hasn't failed yet ... :smiley23:

tnfireman
08-28-2007, 05:24
If my computer stops, my dive is done.

deepdiver47
08-28-2007, 07:00
If you are going to go on a weeks worth of trips from which you are doing 3-4 dives per day you need a backup computer. I can't remember the last time I went diving using the table. I trust my computers with my life. They both need to have the same algorithm as well. That is to say you need two Suuntos :)

Jamesmb
08-28-2007, 07:12
I hate to admit this, but I would say the past year since I have been back into diving, I have more times then not dived using my buddys computer. I did not have a watch but have a depth gauge and SPG. I always stayed shallower then him. I breathe a 80 down much faster then he does, so when we lose each other, which in some lakes we often do, I come up earlier then him. I do not press the no decos limits by any strech, and much of the diving if alone is about 30 feet so time is not a issue. Never do reptetive dives in a day so I do not have to worry about that.

Charlotte Smith
08-28-2007, 09:55
I am going to the surface with my buddy and making a trip to the lds and going back down.......

finflippers
08-28-2007, 13:30
I hate to admit this, but I would say the past year since I have been back into diving, I have more times then not dived using my buddys computer. I did not have a watch but have a depth gauge and SPG. I always stayed shallower then him. I breathe a 80 down much faster then he does, so when we lose each other, which in some lakes we often do, I come up earlier then him. I do not press the no decos limits by any strech, and much of the diving if alone is about 30 feet so time is not a issue. Never do reptetive dives in a day so I do not have to worry about that.

I never let my computer go out of the green and stay deeper then him on the whole dive.

Jamesmb
08-28-2007, 14:08
I hate to admit this, but I would say the past year since I have been back into diving, I have more times then not dived using my buddys computer. I did not have a watch but have a depth gauge and SPG. I always stayed shallower then him. I breathe a 80 down much faster then he does, so when we lose each other, which in some lakes we often do, I come up earlier then him. I do not press the no decos limits by any strech, and much of the diving if alone is about 30 feet so time is not a issue. Never do reptetive dives in a day so I do not have to worry about that.

I never let my computer go out of the green and stay deeper then him on the whole dive.

To let everybody know, we (I had same brand and model), use(d) a Sherwood Source Dive Computer.

TxHockeyGuy
08-28-2007, 14:12
Several others have stated this, but I thought I'd add my own real world example.

The text book answer as already stated is you never dive your buddy's computer.

Now for the real world example. On my first post certification dive I was with a buddy who had an air integrated computer die on him and he had no SPG. We decided not to surface at that time and here's why. We had both been monitoring each other's air supply the entire time so we knew that I was going through my air much more quickly than he was. We were also only down at 35 ft so NDL was not even entering into the equation. We continued the dive until I was around 750 PSI at which point we surfaced. If I recall he had about 1300-1400 PSI left when we checked with an SPG at the surface, which was what we figured he would have.

Some might consider what we did unsafe, and that's fine, you're welcome to your opinion. We however used the information available to us, added a margin of error, and figured out at what point we needed to surface. So can you dive your buddy's computer? Well yes you can, but you have to be really careful about doing it and you need to know some information going into the dive and not just, don't let the number hit zero.

chinacat46
08-28-2007, 18:46
I dive two computers so if one goes out I still have one. I use two Suuntos the vyper and the gekko. I've never had one go out but if I'm on a long trip I'm not taking the chance of missing some dives cause of no computer. I won't dive my buddys.

CompuDude
08-28-2007, 19:45
Several others have stated this, but I thought I'd add my own real world example.

The text book answer as already stated is you never dive your buddy's computer.

Now for the real world example. On my first post certification dive I was with a buddy who had an air integrated computer die on him and he had no SPG. We decided not to surface at that time and here's why. We had both been monitoring each other's air supply the entire time so we knew that I was going through my air much more quickly than he was. We were also only down at 35 ft so NDL was not even entering into the equation. We continued the dive until I was around 750 PSI at which point we surfaced. If I recall he had about 1300-1400 PSI left when we checked with an SPG at the surface, which was what we figured he would have.

Some might consider what we did unsafe, and that's fine, you're welcome to your opinion. We however used the information available to us, added a margin of error, and figured out at what point we needed to surface. So can you dive your buddy's computer? Well yes you can, but you have to be really careful about doing it and you need to know some information going into the dive and not just, don't let the number hit zero.
I think the bigger issue is repetitive dives. That's a case of continuing an existing dive, and using your head and knowledge to consider the variables and make an informed decision you both were comfortable with. That's different from choosing to go in knowing there is only one computer between you... or choosing to go BACK after you two finished your first dive (the one where the computer died).