Shearwater with Suunto RGBM backup.

[drainaps]

A backup computer only needs to "match up" with your primary only to the extent that you don't Lock Out the backup due to deco violations, etc. For most people it's probably better not to pay too much attention to the backup while actually diving to avoid confusion or distractions. I've often kept a back in a pocket and only looked at it between dives to ensure all is well.

If something happens to your primary and it's out of action you can safely switch to the backup know that it's been keeping track of your repetitive dive history and will be a valid source for your remaining dives.

This. As far as you're within NDL, and you always dive both, you'll not lock the Suunto and it can be used as a backup. In case of failure of your primary, just use your backup and follow it.

Also said, do NOT start cross checking both during a dive. As when driving with 2 GPS, you'll end up lost or on a dirt road to nowhere. Not a bad idea what has been ssu, put it in a pocket and forget about it until it was time to use it to get you out of the water.

Another option (that I use when I do Rec), is use a normal watch as a dive timer. In case of failure of your primary, it will still help you time your safety stop and call the dive, or, for the more adventurous, continue the dive with a timer and tables.

 

[dmaziuk]

This. As far as you're within NDL, and you always dive both, you'll not lock the Suunto and it can be used as a backup.

Have you actually tried that on a week-long dive trip? An RGBM backup and non-RGBM primary? Or you just imagine a Suunto will not lock up?

 

[drainaps]

Have you actually tried that on a week-long dive trip? An RGBM backup and non-RGBM primary? Or you just imagine a Suunto will not lock up?

I have! I had a D6i that is now my daughter's computer, and was a REC backup for some time. In my experience, Suunto will NEVER back Shearwater in Tec conditions (I posted about that a few months back, it will lock fast ) but can reasonably do so in NDL.

As said in another post, I used the intermediate Rec GF setting for the Shearwater.

I fully agree though that it's not a good idea to run side-by-side 2 computers with different decompression algorithms, hence the example I gave about driving with 2 different GPS systems and ending in a dirt road.

If your experience in REC is different I'd love to hear more about it.

 

[dmaziuk]

If your experience in REC is different I'd love to hear more about it.

No first hand experience. But from diving an RGBM computer I do know RGBM cares a lot repetitive dives and short SIs, and from playing with the code for ZH-L I know that it cares nothing about any of those things. So the only way I'd use an RGBM backup to ZH-L primary on a multi-day trip is in gauge mode. It's the only way to be sure.

 

[drainaps]

No first hand experience. But from diving an RGBM computer I do know RGBM cares a lot repetitive dives and short SIs, and from playing with the code for ZH-L I know that it cares nothing about any of those things. So the only way I'd use an RGBM backup to ZH-L primary on a multi-day trip is in gauge mode. It's the only way to be sure.

To your very valid points, I'm assuming the OP is conducting a reasonable diving scheme as most of us do when doing Rec: 2-4 dives a day, 16-20 meters average depth per dive, generous surface intervals that are going to be dictated by your dive center du jour, and no substantial change in gasses through the day.

To your point, I'd never do it if I was doing 6 dives a day with 40 minute intervals, one of them in the 40 meters range, and moving from Nx 36 to air and back through the day. Hope this clarifies my point.

 

[KenGordon]

I have done a week in the Red Sea with four dives a day using a Helo2 as backup to a Petrel on a JJ. My buddy had a Vyper, and a twinset.

We did get a minute on stops on one dive. Weirdly, if you stop for stops the computer does not bend.

 

[Saboteur]

I'm thinking about joining the cult of shearwater (probably a Perdix AI) so well represented on these boards. I currently have a Suunto Zoop Novo which I hope (assuming it is repaired by Huish) to use as a backup computer. My buddy dives with the same Suunto, so I have some inertia there. I'm currently not really pushing the NDL on the Suunto, at least not when diving EAN32. Is it plausible to adjust the Shearwater to roughly match the Suunto? Will the default rec mode be in the ballpark, or while I have to tune it more? Am I missing something obvious? I was using an old (Air only) Suunto Favor as a backup, and I did find that a bit annoying (i.e. with the backup going into Deco from time to time).

Another option is a Suunto Eon Core. I've only seen the Perdix AI in person, but I somewhat prefer the default EON display from the pictures. It's also on sale a few hundred bucks cheaper with a transmitter. (CAD $1329 at aquarius in Toronto). I have read lots of anti-Suunto here, but my 20 years experience with them has been mostly OK.

I have no plans to tec dive, and almost exclusively dive in warm water on liveaboards.

Apart from aligning the SW settings to roughly parallel your Suunto, consider this when choosing a new computer. Suunto’s DM5 software which is needed to customize the Eon Core is notoriously flawed and many users report problems on PC’s and Macs. I have two Suunto’s and have no complaints with the computers. I dive EAN32 all time, no more than 3 dives a day and am usually forced to have “shortish” SI’s by the dive OP’s and my dives are satisfactory and don’t seem unnecessarily short from NDL perspective. I like the Core’s form factor and was looking at it as an upgrade for the brightly coloured interface but the DM5 issue stops me from pulling the trigger. I can’t get it to run on any desktop I own. It’s too bad as the Core has been on sale everywhere lately.

 

[Glenn Williams]

As a previous poster said the most conservative computer will control your dive. In the case your discussing the suunto would be the more conservative of the two. Should not be an issue as someone else stated as long as you do the “deep” stops. If your looking at an Eon core or steel and deep stops are turned on there will be stops that seem crazy. For example coming up from around 106 feet the eon will want you to stop at 100 feet for like 20 seconds then around 75 feet another short stop again at 50 until the 15 foot stop for 3 minutes. At least mine did with it set to the most aggressive setting.

There is no issues hearing or seeing the Suunto telling you to stop and do your obligatory wait. If you decide not to the suunto will get you to the surface then lock out for 48 hours. I have never had a lockout as its pretty easy to follow the computer but if you do get locked out your using your backup.

My setup is the Eon Core with an aqualung i300c as backup. The aqualung stayed with me and was happy with everything and let me know about the 15 foot 3 minute mark. Was nowhere near the suunto on stops etc.

I just purchased a Shearwater Perdix ai and will continue to use the i300c as my backup.

I don’t think that your going to be able to get both computers to be in sync as they are on different programs but you probably can get close. I like my Eon core a lot but I can’t wait to dive my Perdix.

If you are able to get both computers to get close let us know what settings you used etc.


Wish you well on your purchase

Glenn

 

[d^2b]

Apart from aligning the SW settings to roughly parallel your Suunto, consider this when choosing a new computer. Suunto’s DM5 software which is needed to customize the Eon Core is notoriously flawed and many users report problems on PC’s and Macs..

I use Subsurface on Linux. One of the subsurface devs is quite pro eon, so I had the impression subsurface could do the necessary customisations. Definitely something to check before pulling the trigger.

 

[Diving Dubai]

Have you actually tried that on a week-long dive trip? An RGBM backup and non-RGBM primary? Or you just imagine a Suunto will not lock up?

I have

Just done one. An extreme current, expedition. I was using an Eon and a Perdix, the guide, a massively experienced tech and cave diver was using a Zoop

We were all on air because of the risky nature of the dives

I ran 40/85 and -1 on my Eon, she was running conservative too. Our NDLs were approx 6min apart, she was the first to get to 5min which was the minimum for head room on the ascents

On a couple of dives we needed to bin the safety stop

No computers were bent - although some of us divers are a bit broken after the week