Perdex/petrel w/ a suunto backup? Pointless?

[TT_Vert]

Yeah we don't have that EVER on boat dives. We're lucky to have 45 minutes. Which means when we do that I need to stay higher than everyone else to stay out of deco and usually off the reef which sucks. Everyone else has a ton on NDL time that don't use suuntos. Hence why it went away in favor of a Petrel2.

 

[KenGordon]

45 minutes is a rubbish surface interval. Find a different boat.

Actually, start doing 20 minutes of stops on the second dive and tell them your Suunto made you do it.

 

[scubadada]

45 minutes is a rubbish surface interval. Find a different boat.

Be practical, there are many areas where you will just not get an hour

 

[KenGordon]

Be practical, there are many areas where you will just not get an hour

Not in my experience. Where are these places and what is the reason?

 

[boulderjohn]

When I do recreational dives, I don't bother taking a Shearwater out of Tec mode, with a 50/80 GF. It will go into deco on a first dive before my buddy with a Suunto. The reverse will be true on the second dive.

Several years ago for reasons I don't recall, I was doing a sea level dive with a Shearwater and a Suunto Cobra as a backup/pressure gauge. On the first dive, I only paid attention to the Suunto for gas pressure. (I know, though, that it did not go into deco.) On the second dive, I thought about the Cobra and wondered when it was that I had used it last. I realized it was in the Denver area, and I realized I still had it set for high altitude. I took a look and, sure enough, it had me owing about 10 minutes of deco while the Shearwater was still within NDL.I let it go into error ode and was able to use it as a pressure gauge even though it was locked out of its computer functions.

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.

If you are doing a muilti-level dive with the Shearwater and it goes bad on you, the odds are you will not be able to use any tables because you will have exceeded them. I discovered that on my very first dive trip after certification. It was in Cozumel, and after a DM led multi-level dive, I tried to log the dive using tables. It wasn't even close. People saw me and laughed. They told me my tables would make a decent Frisbee. That remains the one and only time I have ever seen anyone try to use recreational dive tables to plan and measure dives (other than in an instructional setting) in my life.

 

[scubadada]

Not in my experience. Where are these places and what is the reason?

That's where our experience differs. Going back just 5 years, with the exception of the 3 liveaboards, all land-based operators I've used, rather frequently, or nearly always, had surface intervals of less than an hour. This includes 5 operators in SE Florida, 1 on Little Cayman, 2 on Grand Cayman, and 1 on Roatan. Sometimes the surface intervals were just a little short of an hour, sometimes more.

These were all designed as nonstop dives, on appropriate nitrox, at moderate depths. Most dives were designed to be an hour or so, some deeper dives, less. The SI of less than an hour does not interfere with the duration of the second dive in a pair. This can easily be checked with the planning function. There is always a midday break, generally about 2 hours.

I don't think my experience is unusual for Florida and the Caribbean

 

[KenGordon]

That's where our experience differs. Going back just 5 years, with the exception of the 3 liveaboards, all land-based operators I've used, rather frequently, or nearly always, had surface intervals of less than an hour. This includes 5 operators in SE Florida, 1 on Little Cayman, 2 on Grand Cayman, and 1 on Roatan. Sometimes the surface intervals were just a little short of an hour, sometimes more.

These were all designed as nonstop dives, on appropriate nitrox, at moderate depths. Most dives were designed to be an hour or so, some deeper dives, less. The SI of less than an hour does not interfere with the duration of the second dive in a pair. This can easily be checked with the planning function. There is always a midday break, generally about 2 hours.

I don't think my experience is unusual for Florida and the Caribbean

Reviewing my logs for Cozumel, where they try to do two morning dives and two afternoon dives, I find that once the SI was 48 minutes, the next shortest was 57, the rest over an hour - typically 1h15. For Indonesia and the Red Sea they were longer still.

A proper surface interval is very important. If the boat is rushing that, find another boat.

 

[uncfnp]

That's where our experience differs.

It also makes a difference when you are the first in and last out. One hour is not a magic number.

 

[scubadada]

Reviewing my logs for Cozumel, where they try to do two morning dives and two afternoon dives, I find that once the SI was 48 minutes, the next shortest was 57, the rest over an hour - typically 1h15. For Indonesia and the Red Sea they were longer still.

A proper surface interval is very important. If the boat is rushing that, find another boat.

Cozumel is an exception, not included in my last 5 years, SIs were quite long for me, so were the dives. My liveaboard SIs in the Red Sea were all over an hour. Have you dived in Florida or elsewhere in the Caribbean?

As @uncfnp alluded to. I have a relatively low RMV and try to be the 1st off and the last back on most dives. I hate to cut short my dives. That may contribute in a minor way to my SIs

 

[scrane]

I used a Suunto Goop as a backup to an Oceanic ProPlus 2. After two days it was spontaneously transformed into a depth gauge and remained so for two weeks of diving.