Mass confusion about computers????

[kelemvor]

Some operators appear to use shorter SI's as a way to limit bottom time … shorter dive times and shorter trips. I make it known I require at least a 1 hour SI when I book my dives.

I'm happy to start gearing up at 45 minutes but I hit the water after an hour.

I've been on boats with mandatory surface intervals. Frustrating as can be for those of us who don't want to do the SI. Unless you're diving tables, the need for SI is a highly variable thing. Plenty of dives I've been able to swap and re-drop.

 

[dmaziuk]

In CR we did "45 minutes before gearing up" SIs and the op only ran morning dives -- you could do 3 tanks before lunch for extra $$s, but it was mostly 2. On Roatan or Bonaire we normally do 3-4 tanks/day rather than 2-3. They were also "squar-er" profiles with safety stops in mid-water, as opposed to breathing the tanks down at the top of the wall like you can do on Caribbean reefs.

So I think my Cressi was showing me overall shorter NDLs on that trip than it does in the Caribbean, and that's with fewer total dives and less overall bottom time. Who knows if it was SIs or profiles or what. It hasn't counted me down to where I'd need to cut my bottom time, so, meh. What do I care if the number it shows is 45 or 25 if I wasn't planning to spend 20 minutes at this depth in the first place.

 

[KeithG]

If they are giving you an hour in the water per dive, and they are shallow reefs, even on air a half hour SI will not limit your bottom time.

I have been on some shallow wrecks 50-60 ft where the air divers were told to take an hour SI but the nitrox divers often did 30 minutes or so with no loss of NDL (well not much loss). But you could take an hour on nitrox if you wanted.

If you are doing a shorter SI than Suuntos mandatory 60 minues then your Zoop will be penalizing you by reducing your NDL on your subsequent dives.

 

[scubadada]

The topic of deco algorithms is often contentious on SB. It is quite common for posters to support their personal choices. The OP found the Mares RGBM algorithm to be overly conservative for his use and is seeking alternatives. There is objectve data to support that there are significant differences between the available options.

 

[stuartv]

It hasn't counted me down to where I'd need to cut my bottom time, so, meh. What do I care if the number it shows is 45 or 25 if I wasn't planning to spend 20 minutes at this depth in the first place.

Are you saying that you always end your dive because you get low on gas (or bored) before you run out of NDL?

 

[tridacna]

Hi @Eric Sedletzky

There are less choices than you would think. See So what's the word on the $195 Aqua Lung i-100 ?, post #28 for links to ScubaLab testing, repetitive dives, data also referenced by @arew+4 above. The most popular computer brands are listed below, with my classification of their decompression algorithm as liberal, moderate, or conservative. Any errors are all my own :

Aqua Lung manufactured by OEM Pelagic Pressure Systems owned by Aqua Lung, runs PZ+, moderate

Atomic runs Atomic RGBM, liberal

Cressi runs Cressi RGBM, conservative

Genesis manufactured by PPS, runs DSAT, liberal

Mares runs Mares RGBM, conservative

Oceanic manufactured by PPS, runs both DSAT and PZ+, liberal and moderate

Scubapro runs Buhlmann ZH-L8 ADT MB or 16 ADT MB, moderate

Shearwater runs Buhlmann ZH-L16C with preset or custom GFs, variable from conservative to liberal

Sherwood manufactured by PPS, runs DSAT, liberal

Suunto runs Suunto RGBM, conservative (Eon Steel and Core run Fused RGBM, can be liberal)

Tusa manufactured by PPS, runs PZ+, moderate

Garmin, Ratio, and Divesoft run Buhlmann with preset and/or custom GFs, imagine they are variable conservative to liberal, don't know much about them

Minor correction: I think that the Suunto DX runs fused RGBM. CMIIW.

 

[scubadada]

Minor correction: I think that the Suunto DX runs fused RGBM. CMIIW.

Thanks, no problem, I don't follow Suunto, would never consider buying one.

 

[scubadada]

Are you saying that you always end your dive because you get low on gas (or bored) before you run out of NDL?

That's always been my impression too.

 

[dmaziuk]

Are you saying that you always end your dive because you get low on gas (or bored) before you run out of NDL?

I've seen my NDL go down to 5 minutes or so at the bottom on El Aquila. Granted, that's 10 minutes less than PADI table single dive to that depth, but that was after a few days of diving already, so not entirely unexpected. All the groupers were above the deck anyway, it's just garden eels at the bottom and I've seen those before. I guess qualifies as "bored". But we usually stay shallower. On really shallow ones you never run out of either gas or NDL, I guess they qualify for "bored" too.

If you go to a "concierge dive" place with no shore diving to speak of, like Roatan, and on a package deal, then the schedule is set for you. On our own we tend to work out the schedule for the day, and I am most definitely not a morning person, esp. on vacation -- so if you don't start at 6 am, and want to mostly digest your lunch before you hit the water again, and want to visit 3-4 sites that day, you end up not going over an hour/tank.

Low on gas happened, too: my BH and our DM were frolicking with a turtle for like 10 minutes.

So yeah: I end my dives because my sac needs a tuck and my cylinder is really tiny.

 

[scubadada]

Every dive has some limit, operator duration, gas, NDL. I want as long a dive time as I can get. My RMV is good, I'll take a liberal deco algorithm.