Diving two different computers - got "Suunto'd" - and a whale shark

[Lizard Leg]

I would like to get the boards thoughts on this. My wife and I both dive Shearwater Perdix, 40/85 GF. We did some diving this weekend and wore our old Suunto Zoop’s as backups – just in case something happened to the Perdix as we’re in the habit of doing now.

First dive, USS Oriskany, MOD 126, planned max 110, actual max 107. Perdix had us at NDL 2 when we started up the line, the Zoop had us at NDL 4. I just happened to glance at the Zoop when we hit the line.

Nice, long SI and back in the water with almost the same exact MOD, plan and depths. Back at the line with the Perdix showing NDL 2, started up up and it switched to NDL 1 – still no issues just cutting it close (come on guys, a whale shark was involved and we were heading up). A few minutes later, Perdix NDL showing was showing something like 30 minutes or longer as we did our deep stop. All is right with the world, and did I mention the whale shark?

Got to 20 and started our safety stop. When the stop was over, happened to glance over at the Suunto at about 15 feet and WTH? Ceiling and stop. Wife’s was showing the same. Plenty of gas, so we cleared it and went up.

We did 14 dives in the Flower Gardens to almost the same depths although a little shallower and it never gave us an obligation. This weekend in Pensacola, 3 out of 6 dives where the Perdix had us in the clear with no issues, the Suunto had us with a stop. 2 of the dives were less than 85’ on 32%.

We know the DM’s and captains fairly well, and because we did clear the Suunto's, they just laughed it off and said we got "Suunto’d".

I’m not spending another $1,600 on backup computers right now. House remodel, etc. so not really in the budget. Other than having a stop, what are the communities thoughts on diving two computers that are a little out of whack, when the opportunity isn’t there to have them match? We’re doing Cozumel for the first time in October and I doubt those DM’s would be as forgiving if this happened there

By the way, did I mention the whale shark?

 

[Bigeclipse]

I would like to get the boards thoughts on this. My wife and I both dive Shearwater Perdix, 40/85 GF. We did some diving this weekend and wore our old Suunto Zoop’s as backups – just in case something happened to the Perdix as we’re in the habit of doing now.



We know the DM’s and captains fairly well, and because we did clear the Suunto's, they just laughed it off and said we got "Suunto’d".

I’m not spending another $1,600 on backup computers right now. House remodel, etc. so not really in the budget. Other than having a stop, what are the communities thoughts on diving two computers that are a little out of whack, when the opportunity isn’t there to have them match? We’re doing Cozumel for the first time in October and I doubt those DM’s would be as forgiving if this happened there

By the way, did I mention the whale shark?

I would follow whichever computer gives you requirements to get out of the water first (has the shortest NDL time). The problem is they run two different algorithms. I also own a Perdix and my backup is a GEO 2.0. The GEO will give me more NDL time than the Perdix on the first dive but all subsequent dives during the day will have less. Because of this I dive the GEO 2.0 in gauge mode. If my Perdix craps out, I will switch the GEO 2.0 into dive mode. In your situation, unless you have the newest line of Zoops, you cannot select gauge mode so your only option is to either leave the zoop on the boat or to follow whichever computer makes you get out of the water first...which for dive 1 will be the Perdix, and then all subsequent dives will be the Zoop.

 

[uncfnp]

First of all. Congrats on the whale shark. Its still on my bucket list.

FWIW I dive a Petrel and a Cressi. The Cressi has a similar algorithm and the same reputation as the Suunto. For health reasons I dive very consevatively. With the Petrel set for VBM + 5 and the Cressi at SF 0 they match up pretty well for 2 dives a day.

The down side to diving two mismatched computere is exactly what you experienced, the possibility for needing to clear deco on the more conservative backup computer or have it default/lock out. Not an issue if you are willing to accept this limitation.

As for diving in Cozumel and having the backup go into deco, I had just this situation. For the type of dive profile typical for Coz, the Suunto will likely clear during the "shallow" portion of the dive and safety stop. I guess it depends on the dive op but no one checked my computers at any point during the week and my guess is that diving a Perdix and a backup most dive ops will assume you know what you are doing.

 

[MaxE]

What was your rate of ascent? The Suunto's are very sensitive to sudden movement even moving your arm up too fast and will add a minute stop for a fast ascent rate "violation" it shows up as a 10ft ceiling. I have had this happen hanging on the line with moderate chop the boat moves the line moves you move

 

[Lizard Leg]

What was your rate of ascent? The Suunto's are very sensitive to sudden movement even moving your arm up too fast and will add a minute stop for a fast ascent rate "violation" it shows up as a 10ft ceiling. I have had this happen hanging on the line with moderate chop the boat moves the line moves you move

Not real sure, but I did haul ass off the line at 56' to head back out to the whale shark as it made its pass. I never varied more than +/- 2' the entire time, but I was moving pretty fast. With the camera rig, it's possible I moved it too fast.

 

[victorzamora]

Yup, the only two options are as above. Dive just the Perdix or always dive the computer that's telling you to ascend. Waiting for the Suunto to clear or bending it and ignoring it are variants of the same two options. One option would be to talk to the boat captain in Coz and give him a head's up. Just remember that if you leave your Suunto on the boat and the Perdix craps out, ascend with your wife and add a couple minutes to the stop....then stay dry for a while (12-24 hours depending on who you ask) and then dive the Suunto. Your Suunto won't know anything about your RNT. I've heard stories of people switching computers during their SI for longer NDLs....don't be that guy.

Bigeclipse: Not directly to the OP, but the Geo2 has a Pelagic Z+ option that is based on the Buhlmann your Perdix is running. While not identical, it'll act much more like the Perdix in terms of shortening repeat dives. The RGBM-based Suuntos (and Mares and other bubble models) tend to shorten NDLs after short SIs, reverse-profiles, and sawtooth profiles much more so than Buhlmann-based dissolved gas models while providing more liberal first-dive NDLs.

 

[fmerkel]

Suunto are widely known to be conservative, especially if you ascend too fast, and on multiple dives. My wire routinely sets hers at 26% and dives it on air to sort of match up with my Aladin 2G.....that's for a single dive.

At God's Pocket this spring she ended up borrowing a Petral she got so frustrated with it messing with our dives. At one point she had 12" of deco, I had 12" of NDL. I had a Suunto Favor (air only) I carry as a backup and seldom even look at. It's just there if I need it. I bent the sh!t out of it 2x in a week. Took 39 hours to clear the first time.

So, what you saw is entirely normal for Suunto vs. many other computers. Choose your own risk profile.

 

[Lizard Leg]

If we had not worn the Zoop, we would never have known, and since we weren't really looking at them, I'm not sure how close they were to the Perdix when they bent. We're not talking anything major here. I think the worst was 12 minutes.

I find it strange that 14 dives in the Flower Gardens and not one issue, even diving to NDL limits on the Perdix. Shallower profiles this weekend and we bent them.

 

[fmerkel]

You paid attention to them and dove as you needed to not bend them.

I switched my Aladin from L0 (least conservative) to L1 on a dive, wife was still on L0. On a shore profile we do a lot I came up in the shallows with 4" deco and she wondered why I didn't go in when she did. I knew I didn't have to clear the computer, but I dutifully stayed and did so.
I was amazed at the difference between L0 and L1.

 

[Lizard Leg]

You paid attention to them and dove as you needed to not bend them.

I switched my Aladin from L0 (least conservative) to L1 on a dive, wife was still on L0. On a shore profile we do a lot I came up in the shallows with 4" deco and she wondered why I didn't go in when she did. I knew I didn't have to clear the computer, but I dutifully stayed and did so.

We had the gas, we had the time, there was no reason NOT to stay there and clear them. Plus, I'm underwater making bubbles. It's all good.