Computers and backups - looking for pearls of wisdom from the more experienced

[nanohawk]

Yea the only way I would get 2 hours would be on a snorkel, at the surface. lol.

But staying shallow comes with better lighting and less air consumption. My typical dive is around 45 to 50 minutes from looking at my logs earlier today.

I picked up a used Perdix AI with transmitter today. I was going to buy new, but one popped up on SB at a reasonable price.

 

[KenGordon]

I think GF with Buhrmann ZHF16 has a better margin of safety. That's just my personal opinion, based on the limited research I've done. So that automagically rules Suunto out. They have an unpublished RGBM model. Whether it appears to yield the same NDL limits or not is really secondary IMHO.

Regular RGBM is published. However, Suunto RGBM is actually just a disolved gas model with some extra edge case handling for fast ascents and short SIs. You can use the Suunto planner to test how any dive you might do will turn out. The Eon series computers have several levels of conservatism and the Steel can do ZHL16 if that is what floats your boat.

I guess your limited research is reading FB and ScubaBoard and not actually getting in the water with people diving any of these computers. The internet likes to repeat stuff over and over, many of the people on here slagging off Suunto have not dived with Suunto computers.

All dive computers use simplistic mathematical models. They all come out pretty much the same. However some have nasty screens, some have nice screens, some have software written by professionals employed by companies selling computers for years, some Bluetooth, nicer buttons etc etc, they vary in price by 5 to 10 fold. There are a lot of factors which are important in choice of a dive computer. The algorithm is not the most important.

 

[Blackcrusader]

Yea the only way I would get 2 hours would be on a snorkel, at the surface. lol.
But staying shallow comes with better lighting and less air consumption. My typical dive is around 45 to 50 minutes from looking at my logs earlier today. I picked up a used Perdix AI with transmitter today. I was going to buy new, but one popped up on SB at a reasonable price.

This is from a 55 minute dive with max depth 20m or 65 feet. Average depth for the dive was 11.34m 37 feet. This is an AL 80 so I started with 200 bar which is around 2900 psi and I finished the dive with 140 bar or 2000 psi. I weigh 300 pounds so not a small fellow. Was a slow dive I was the last diver dawdling along I think I was in a trance lol Took several video and photos. I must say even I was shocked by my air consumption on this dive it was rather low. The DM who I dive with a lot was like this is nonsense to finish the dive with 140 bar we had other smaller divers finish the dive with 40 bar. You can upload your dive into to not only shearwater apps but this one as well is called diving log a free download.

Great you got a Perdix AI at a good price. I love mine.

 

[nanohawk]

Regular RGBM is published. However, Suunto RGBM is actually just a disolved gas model with some extra edge case handling for fast ascents and short SIs. You can use the Suunto planner to test how any dive you might do will turn out. The Eon series computers have several levels of conservatism and the Steel can do ZHL16 if that is what floats your boat.

I guess your limited research is reading FB and ScubaBoard and not actually getting in the water with people diving any of these computers. The internet likes to repeat stuff over and over, many of the people on here slagging off Suunto have not dived with Suunto computers.

Apparently reading isn't your strong suite. I watched a DAN hour long presentation from an Anaesthesiologist who is also a tech diver. I'm sure you know more than he does. He was citing research from the USNEDU and French Military dive programs. I'm sure you know more than them too. USNEDU (US Navy Experimental Dive Unit) did several hundred dives under controlled conditions. The data was pretty convincing. But please tell me about your opinion of my research. They (NEDU) stopped their study halfway through because the statistical data after 400 dives was that RGBM was bending their divers at a significantly higher rate than Buhrmann ZHF16. Yes it was deco diving and yes they were looking at RGBM+deep stops (Suunto default) vs Buhrmann ZHF16 +GF. The net result was that the RGBM+deep stops were unloading fast tissues while continuing to load slow tissues, resulting in DCS for the study participants at a higher rate then the Buhrmann ZHF16 +GF adherents.

Suunto does not publish their model from everything I've read.

As a recreational diver non-decompression diver I don't come close to pushing the limits of any model.

All dive computers use simplistic mathematical models. They all come out pretty much the same. However some have nasty screens, some have nice screens, some have software written by professionals employed by companies selling computers for years, some Bluetooth, nicer buttons etc etc, they vary in price by 5 to 10 fold. There are a lot of factors which are important in choice of a dive computer. The algorithm is not the most important.

Crap customer service and the need to send the computer back for battery changes also factored in to my decision. At any rate..... the decision was made and is done.

 

[Blackcrusader]

As a recreational diver non-decompression diver I don't come close to pushing the limits of any model.

You wrote your happy spot is 20 - 45 feet. For that GF on your DC is never an issue and as you wrote no deco diving. So any dive computer with Buhrmann ZHF16 +GF adherents for you is fine. Plus you wrote your average dive times are 45 - 50 minutes which are not long dive times. So are you doing dives to 100 feet? Even if you are you are not pushing things when staying within NDL as most people do not stay at one or 2 minutes to NDL on a very slow ascent anyway. A lot of recreational divers need to ascend so they have enough air to finish a one hour dive as many vacation divers may only do 10 - 20 dives a year so their gas consumption is not something they are too concerned about. Deco diving is also recreational diving and you never know that over time you may want to take a TDI advanced nitrox and deco course so you have a great DC for that. At the shallow depths you dive I would be surprised if you are using nitrox.

Of course any backup to your DC is using the PADI RDP tables and planning using that if you have to. You do not need to rely on a computer as a backup when you can just use the RDP. Personally I do not know any recreational diver that gas plans non deco dives and that includes instructors who also teach technical dives. As others have written as you have no deco obligation you can end any dive without a safety stop. DCS risk is pretty minimal.

 

[scubadada]

@nanohawk

You should be more circumspect in your posts without a full understanding of what you are referring to. The NEDU study had nothing to do with comparing Buhlmann to RGBM. Again, I think you are in over your head with regard to your comments. I would suggest taking a step back and improving your knowledge base.

Apparently reading isn't your strong suite. I watched a DAN hour long presentation from an Anaesthesiologist who is also a tech diver. I'm sure you know more than he does. He was citing research from the USNEDU and French Military dive programs. I'm sure you know more than them too. USNEDU (US Navy Experimental Dive Unit) did several hundred dives under controlled conditions. The data was pretty convincing. But please tell me about your opinion of my research. They (NEDU) stopped their study halfway through because the statistical data after 400 dives was that RGBM was bending their divers at a significantly higher rate than Buhrmann ZHF16. Yes it was deco diving and yes they were looking at RGBM+deep stops (Suunto default) vs Buhrmann ZHF16 +GF. The net result was that the RGBM+deep stops were unloading fast tissues while continuing to load slow tissues, resulting in DCS for the study participants at a higher rate then the Buhrmann ZHF16 +GF adherents.

Suunto does not publish their model from everything I've read.

As a recreational diver non-decompression diver I don't come close to pushing the limits of any model.


Crap customer service and the need to send the computer back for battery changes also factored in to my decision. At any rate..... the decision was made and is done.

 

[nanohawk]

I guess your limited research is reading FB and ScubaBoard and not actually getting in the water with people diving any of these computers. The internet likes to repeat stuff over and over, many of the people on here slagging off Suunto have not dived with Suunto computers.

I shouldn't have to justify why I prefer one brand of equipment over another. Nor were his comments constructive or anything other than a very weak attack on my not wanting to use a Suunto computer.

If you want to change my opinion, offer some facts or point me to where I can find them. Tell me about your experiences. Tell me what your opinion is and why. Each of us should make our own decisions about the level of risk, conservatism, or dive model that we want to use.

I wholeheartedly agree with you that decompression diving is not my area of expertise. It's not even something I'm interested in at this point. I do think that Dr. Mitchell had some very good data, however it's a 6 year old talk and there may be more developments since then. His talk was sufficient to answer my questions about the differences in the models. I came away from it actually understanding what gradient factors were.

I decided to return the Suunto EON Core for a number of reasons including a reputation for poor customer service, a sealed battery design, some interface things I did not like, and an unpublished model. If other people are happy with their gear, great. I don't want to use it as a DC. That's my decision.

Shearwater on the other hand has a reputation for stellar customer service and I like their design philosophy. I'm confident I can find the battery for a Perdix AI anywhere should I need one. I initially did look at Shearwater, but the Suunto looked like it would be easier to read and was a little bit cheaper. I've since concluded I will have to have reader type lenses in my dive mask anyway, so that advantage is gone.

You wrote your happy spot is 20 - 45 feet. For that GF on your DC is never an issue and as you wrote no deco diving. So any dive computer with Buhrmann ZHF16 +GF adherents for you is fine.

Correct, but I like Shearwater's hardware, so that's what I chose.

Plus you wrote your average dive times are 45 - 50 minutes which are not long dive times. So are you doing dives to 100 feet?

If there is a reason to, yes. But I generally find more interesting things in shallower water where the light is better. As I like doing UW photography that works well. As a bonus, gas consumption is better in shallower water.

Even if you are you are not pushing things when staying within NDL as most people do not stay at one or 2 minutes to NDL on a very slow ascent anyway. A lot of recreational divers need to ascend so they have enough air to finish a one hour dive as many vacation divers may only do 10 - 20 dives a year so their gas consumption is not something they are too concerned about. Deco diving is also recreational diving and you never know that over time you may want to take a TDI advanced nitrox and deco course so you have a great DC for that. At the shallow depths you dive I would be surprised if you are using nitrox.

Yes, normally I don't ride the NDL limits. I generally dive Nitrox if it's available. Yes, the Perdix is compatible with more advanced activities if I decide that I ever want to do those.

Of course any backup to your DC is using the PADI RDP tables and planning using that if you have to. You do not need to rely on a computer as a backup when you can just use the RDP. Personally I do not know any recreational diver that gas plans non deco dives and that includes instructors who also teach technical dives. As others have written as you have no deco obligation you can end any dive without a safety stop. DCS risk is pretty minimal.

I prefer not to dive tables. Computers are more convenient. I do carry my RDP cards with my dive log though.

 

[Blackcrusader]

If there is a reason to, yes. But I generally find more interesting things in shallower water where the light is better. As I like doing UW photography that works well. As a bonus, gas consumption is better in shallower water. I prefer not to dive tables. Computers are more convenient. I do carry my RDP cards with my dive log though.

I don't find the light is better in shallow water on my night dives lol. Also many reefs have overhangs and coral platforms where critters are underneath in dark places, morays tend to stay in dark cavities if they are not swimming elsewhere so being shallow only helps where direct sunlight is available. I don't bring my RDP with me and my dive log is simply my Perdix. It has all the information I need post dive.

The seahorse shots I posted were at 26m depth and I only found the pair of them from ascending from a 34m depth wreck dive up a grassy and sandy sloping sea floor. So yes sometimes really interesting things can be found at depth. Often pigmy shrimp are seen at depths of 100 feet or deeper. As I got older with vision issues I decided to get tri-focul ocular lenses and cataract surgery done. Perfect vision for the rest of my life now. Perdix makes it easy to see with it's large screen which I one of the reasons I bought it as I do not wear a watch so the Teric was not for me.

 

[Blackcrusader]

Yea the only way I would get 2 hours would be on a snorkel, at the surface. lol.

Well maybe after a 7 year break from diving you need to take a refresher course or refresher dives for sure with a DM or instructor.
It's good you want to learn about GF factors and such but regular diving would be of more benefit. As you are going to be getting back into diving and also doing photography at the same time it is easy to get distracted.

 

[nanohawk]

I don't find the light is better in shallow water on my night dives lol.

Well clearly if there is no light at the surface there will be none in shallow water. LOL. Lots of neat things come out at night.

The seahorse shots I posted were at 26m depth and I only found the pair of them from ascending from a 34m depth wreck dive up a grassy and sandy sloping sea floor. So yes sometimes really interesting things can be found at depth. Often pigmy shrimp are seen at depths of 100 feet or deeper. As I got older with vision issues I decided to get tri-focul ocular lenses and cataract surgery done. Perfect vision for the rest of my life now. Perdix makes it easy to see with it's large screen which I one of the reasons I bought it as I do not wear a watch so the Teric was not for me.

Yea I went and looked up the trifocal cataracts after I read about your having them done. It's on my radar but I'm waiting to see where my vision stabilizes. Only had to start wearing glasses a few years ago and I'm due for an adjustment again this year.

Well maybe after a 7 year break from diving you need to take a refresher course or refresher dives for sure with a DM or instructor.

I'm waiting on my regulators to be rebuilt. You are 100% correct that refresher dives are in order. I'd rather break in my gear in my pool or in the local mudpuddle than on a trip. The guy rebuilding my gear is also an instructor and is probably who will do my refresher dives, but if not it will be the LDS owner who also happens to the be the instructor who taught me to dive.

He (the guy who taught me to dive) had nothing nice to say about Suunto. He discouraged me from even looking at them saying they were too conservative. At the time I didn't get what he was talking about, but after studying it I get it and he was right. He is only doing his dive shop part time right now and doesn't rep shearwater or Suunto or I would have supported him.

It's good you want to learn about GF factors and such but regular diving would be of more benefit.

My foray in to GF was to understand the conceptual differences between the models and what the gradient factors really meant.

As you are going to be getting back into diving and also doing photography at the same time it is easy to get distracted.

I think I'll be fine, but thanks. I did quite a bit of training which isn't in my dive count. I felt like OW and AOW were not nearly sufficient to be a competent diver. I usually only dive my AOW card but I carry a bunch of other certs. I'll do enough local dives to feel comfortable in the water again. We do have a little bit of clear water in Texas, but none of it is what I would call "convenient." It's all relatively cold by my standards.