Perdex/petrel w/ a suunto backup? Pointless?

[TT_Vert]

Thanks much guys. Appreciate the wisdom.

 

[buddhasummer]

I could be mistaken but my understanding is you can only make a Suunto more conservative from it's already conservative default setting, you cannot make it more liberal.

 

[Jack Hammer]

I use a Suunto Gekko as a backup to my Petrel for tech and cave dives. Once "locked" out it is still fully functional as a bottom timer and records dive info which you can look at to plan your next dives.

 

[JohnnyC]

Set the Suunto to gauge mode, carry tables for backup, and if the Shearwater ever craps out, run your backup tables with your bottom timer'd Suunto.

Trying to use the Suunto in its dive mode will cause issues with repetitive dives sooner or later.

 

[KenGordon]

Dive the Shearwater but do the Suunto's stops. You get to pretend to be doing no stop dives but reduce your chances of getting bent by a bit of shallow offgasing.

I did two years of CCR using a Suunto as a backup to a Petrel. It is not a problem.

 

[Scared Silly]

I use a planning tool to generate contingency dive plans and write them onto wet notes. Shorter and longer dives than the intended profile. If my computer dies I use my back up on gauge mode to carry out the contingency plan (custom cut tables)

Ditto ... no need for a backup computer. FWIW I use Suunto D3 for my backup gauge.

I could be mistaken but my understanding is you can only make a Suunto more conservative from it's already conservative default setting, you cannot make it more liberal.

Depends on the model. For some 10 years now there has been an option for full or attenuated (50%) RGBM. Here is an old thread from 2009: Has anyone dove with the Suunto Attenuated (50%) RGBM engaged?

 

[TT_Vert]

So when in Error state it will still work in gauge mode? I thought it was completely useless then?

Dave

 

[AJ]

As I rcorrectly emember my D4i did not do anything until cleared after a lock up.

 

[muzikbiz22]

Spent a week of diving in Grand Cayman in June, here's what I know;

Me - Perdix, Rec Mode, Medium, 31/32% Nitrox (depending on analyser)
Buddy - D4i, A0, P0, 31/32% Nitrox (depending on analyser)
2 to 4 dives a day, Nitrox all week, 31/32% Nitrox
Average dive Time - 1 hour'ish
Same profiles together every dive. Combination, Deep, Reef, Wreck, etc.
3 minute safety stops every dive
Scientific Findings - "Gee whiz, our computers aren't that far off from each other with NDL's, Tissue Bar Graphs, etc. That's interesting".
No spreadsheet or Hard Data to provide. With that said, I dive all the time here in SoCal. I'm going to dive my Perdix and Vyper together a dozen times or so, and see what comes of it. Perhaps a spreadsheet is in my future.

I find it interesting the "dog pile" of opinions set forth without most knowing what type of diving the OP does/did, gas mix, etc. Just the usual "Suunto sucks, and you're a sub human if you use". I think the OP mentioned later in the thread "rec diving".

 

[TT_Vert]

Please let me know what you find. I frequently compare my old suunto vyper w/ the dive ops/guides computer and without fail they have 10+ minutes more NDL than I ever do on the same dive. I've had over 20 minutes difference before. If anything given they probably dive every day they should have LESS NDL than me given an equal dive based on residual nitrogen. It's always the same story from them, "suunto's limit diving" I've heard this no less than 20 times from both other divers and dive ops. Not to mention my experience when I do 2-4 dives per day on a boat. When I do my dive plan for next dive and compare my NDL w/ other divers who went down with me, came up w/ me and were at the same depth as me I usually need a SI 20-30 minutes longer than most to get the same NDL at a given depth. So that means I stay up higher off the reef or we all wait longer.

I don't think this reputation of the suunto algorithm has come out of thin air. Most of the people commenting have probably been the other divers on the boat waiting for the suunto diver (me) to offgas enough to do the next dive. I can't tell you how many times I Just jumped in and modified my dive profile not to go into deco just so everyone else didn't have to wait another 20+ minutes baking on deck.

When I was doing a bunch of shore diving in Bonaire it was fine as I didn't hold anyone back and I could just get back into the truck, grab lunch and find another dive spot. In that situation it is fine but when you are on a short dive boat trip the suunto will hold you back if your SAC is good and you do many dives in a day. It is a fact.