Backup computer for when your main fails while in diving trip ?

[FishWatcher747]

Every time I've been on a Caribbean recreational dive trip, I've watched dive teams dive VERY different profiles. On a wall dive, literally one person dives 45', the other dives 75' the whole dive. I don't agree it's good practice, but it appears to be very common.

I have witnessed this also. But the logical answer to this is not carry two computers. It is to carry a redundant gas source with an independent regulator.

If you have a buddy diving a different profile as you they are not your buddy. You are diving solo.

 

[MB NZ]

Apparently, you're in disagreement with yourself from a page ago then.

The answer is more nuanced. It depends on circumstances. An idealised view of buddy diving just doesn't translate to multi-dive, multi-day diving with one computer between a buddy pair. Even if they dive exactly the same profiles, it's not uncommon for one or the other diver to skip dives at different times. You can say this isn't buddy diving if you like. This may not apply to the OP, it's a broader observation.

 

[rob.mwpropane]

If one is following buddy diving teaching from OW for recreational NDL dives, diving different profiles to your buddy is not taught as a valid method of buddy diving.

How exactly is your buddy supposed to be your alternate air source if you are diving significantly different profiles to make a difference?

Sh!t happens... even more so underwater. If you're depending on your buddy as an alternate air source it's time to think a little more outside the box. Plan your dive better, don't run out of gas. If you run out of gas so much went wrong leading to that point.

I plan for a tank to go, a reg to go, a mask to go, a dc to go on every single dive. The level of comfort that comes with knowing that I can solve just about any problem underwater is worth it's weight in gold.

I do understand there are different levels of diving. I think a lot of us have had problems underwater and we see the value in redundancy and being prepared. I didn't spend $$$ to get somewhere to sit on the sidelines because I lost my buddy and my dc took a ****.

You and scubadada are using some story to counter what I said in response to the OPs question. Again, I'm talking about buddy diving and using the read-out from the buddy's computer for the rest of the day while bringing the spare.
Using the buddy's read out is not blind faith or guess work or unsafe in any way. If your buddy is 10m below you throughout most of the dive, it's not buddy diving.

Don't forget @RyanT he said it too

 

[berndo]

Even if they dive exactly the same profiles, it's not uncommon for one or the other diver to skip dives at different times. You can say this isn't buddy diving if you like. This may not apply to the OP, it's a broader observation.

Sigh, your keep making up stuff up in order to evade the point. So what If a buddy skips a dive, you're using the spare computer. You're following the computer that gives the more conservative numbers in a buddy team anyways. If my buddy drops below me I either follow or motion them to come up to my depth, eitherway, my profile will basically be the same as that of my buddy. Fishwatcher correctly pointed out why you should stay with your buddy.

 

[Mike_4635]

The reason I have two computers is on a Turks and Caicos live aboard my Datapro 3 when to deco on the third dive when I hit 15 feet. I had been well within NDL limits on the second dive and we had a 2 hour surface interval. The Datapro locked up for 24 hours. Lucky I had an OC1 DC I had also been using. The boat loaned me a SPG that day and another computer the next day.

 

[Bazzathemammoth]

So let me get this straight. According to most of the users in this thread giving advice, all rec divers should carry 2 computers on every dive on every trip and otherwise can't keep diving on that same trip safely? Really?

So for the OP it's not enough for them to bring one spare SW, they have BOTH have to have a spare SW and carry it on every dive? Accrding to Scubadada's logic they both need spare computers because the wife couldn't use the husbands spare computer if her's fails as the husbands spare SW doesn't have the exact same gas loading (which is not a thing)?

Isn’t that basically what the training material says? Ie if you want to use a fresh computer while multi day diving you need to not dive for 24 hours? If you don’t want to wait have a back up computer just in case?

 

[Lorenzoid]

I would be comfortable relying on my buddy's computer to finish up a day of diving together because our buddy procedures are to stick together like glue. We decide on a depth, and if we want to change the depth we signal each other. So I believe it would work okay for us--at least for the purpose of finishing diving for that day. Others may have different ideas of buddy procedures, and it may not work for them.

 

[harvalen]

Lastly, a recreational Suunto computer is going to **** it's pants if you dive a Shearwater, even with a gradient factor of 30/70.

I'm no fan of Suunto, but that's a bit of a hyperbole. I've done plenty of dives with one Buhlmann computer set to 50/70, one set to 60/85 plus a Suunto Vyper Air. The Suunto will give more time than GFHigh 85 Buhlmann on 30 m (100 ft) dives. If you're spending a lot of time in the 15-20 m range, then the Suunto will start being a bit more conservative than Buhlmann with GFHigh 85.

If you're doing surface intervals that are shorter than 2 hours, then the Suunto will be closer to the GFHigh 70 computer, while still giving slightly more time on deeper dives. On a LOBs that hasn't been a problem since surface interval has always been longer than 2 hours.

The main thing to look out for is the mandatory safety stops you can get if you get fast ascent warnings, since they can lock you out if you skip them. They're fairly easy to trigger if you move your arms too fast, but you can attach the Suunto to a D-ring if that's something you do.

The above is with default (least conservative) personal settings. If you pick the middle one, then it'll be closer to GFHigh 70, but that'll go down to ~55 if your surface interval is shorter than 2 hours. Which makes anything other than the least conservative setting mostly useless.

 

[Capt Jim Wyatt]

Really not necessary unless you're solo diving. Just follows the buddies computer on next dive of the day.

I consider this bad advice. Each diver should have their own way to determine NDL or Decompression requirements. This is pretty much an industry standard and has been for years.

 

[Capt Jim Wyatt]

My Primary computer for OC is a perdix, backup is a petrel. For CCR my primary computer is a NERD2, backup is my petrel.

I agree with many posters above that the backup computer should match the primary computer in terms of algorithm.

If I am teaching a tech class I require it.