Shearwater with Suunto RGBM backup.

[d^2b]

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.

 

[Fastmarc]

The Suunto will likely be close to the Rec low conservative settings of GF 45/95. Well, that's the case for my Mares RGBM. If you had them both, using their dive planning could guide you, at least where the 1st dive is concerned. For multiple dives... ¯\_(ツ)_/¯

 

[uncfnp]

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.

Its two very different algorithms and as such impossible to match, especially on repetitive dives where the differences can be noticeable.

For my SW and Cressi combo, a GF high of 80 will mostly match but after several dives the Cressi RGBM may hit deco if I am not watchful. For the SW to pretty much always be the lead computer for NDL I dive GF high of 70, specifically 50/70.

 

[scubadada]

The Shearwater rec default of 40/85 (medium conservatism) would likely be a reasonable start at a match for Suunto RGBM. It may be a little more conservative on the first dive, it may become a bit more liberal on repetitive dives. Experience will allow you to fine tune. Unless you are willing to satisfy deco obligations, the more conservative computer will control your dive.

The Eon Core (Fused RGBM) has a considerably wider range of performance than the Zoop and can be quite liberal. An intermediate setting could likely be found to match your Zoop. @Diving Dubai has considerable experience with Eon Steel as well as a Shearwater and could likely answer additional questions.

Best of luck in your purchase

 

[Fastmarc]

I should clarify that in my case using the planning modes, setting the Perdix to 45/95 matches the NDL bottom times of the Mares RGBM. I haven't experienced yet how it will play out during an actual dive which will be multilevel.
As others have said above on multiple dives I would expect them to very different.

 

[scubadada]

Its two very different algorithms and as such impossible to match, especially on repetitive dives where the differences can be noticeable.

For my SW and Cressi combo, a GF high of 80 will mostly match but after several dives the Cressi RGBM may hit deco if I am not watchful. For the SW to pretty much always be the lead computer for NDL I dive GF high of 70, specifically 50/80.

@uncfnp is absolutely correct. I dived a Dive Rite Nitek Q for 3 years in backup of an Oceanic VT3 running DSAT, in an attempt to learn Buhlmann ZH-L16C with GF. My conclusion was that it was impossible to get the two algorithms to match closely for all dives. I learned many of the variables that caused divergence and could largely account for them. I grew weary of adjusting the GFs of the Nitek Q for each dive, so settled on a very good single fit, a GF high of 95. I simply dived the more conservative computer for no stop diving or satisfied the deco obligation on one or both computers for light deco. I now dive a Teric with the VT3 and successfully follow the same strategy.

 

[scubadada]

I should clarify that in my case using the planning modes, setting the Perdix to 45/95 matches the NDL bottom times of the Mares RGBM. I haven't experienced yet how it will play out during an actual dive which will be multilevel.
As others have said above on multiple dives I would expect them to very different.

@Fastmarc raises an important point. First, clean dive NDLs reflect only one aspect of a decompression algorithm's performance. It gives no insight into the performance for repetitive dives, where the SI, depth, and profile may all change. By using the planning function between dives and paying attention during subsequent dives, you can learn a great deal

 

[davehicks]

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.

One other good use case for a backup [but not for multi day diving] is to track a Buddy's approximate dive profile. I often dive a rebreather, and will set my Backup computer to my Open Circuit buddy's mix. This way I can be sure we are well within a safe profile for the buddy using a different, more conservative setup.

 

[d^2b]

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.

Right. And given my pretty conservative (on an individual dive, anyway) diving habits, it's probably not going to be a problem (the suunto might get low on on NDL, but even going into deco seems unlikely to me).

 

[Glenndini]

I have dived that combination of computers. Unless you have the Perdix set to a GFhi of about 95 it will have shorter NDL than the Zoop on at least the first dive.
After the first dive it becomes a bit of a lottery. On subsequent dives the Zoop will shorten NDL times by an unknown factor (due to proprietary algorithm) for short SI, ascent rate violations on first dive and possibly other unknown factors. I have found Suunto RGBM not too bad if you don't annoy with fast ascents and short SIs.
They will never match up for multiple dives.