And this is just the thing that so irritates me in these discussions. Do you equate recreational with an inability to learn? Any diver should learn to use their DC be it a Zoop or a Petrel.
Huh? What do you think you are doing with the Zoop?
Petrel
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Mostly people claim Suunto do not give such long NDL times as brand X. If that is true your point above would mean having a shorter dive (or longer deco) would make you 'feel like crap', unless the odd minute at 17m due to a Suunto deep stop is the culprit.
Dr. Lecter
Contributor
I would suggest they consider using their ability to search out, analyze, and apply new dive-related knowledge...but I suppose that'd be asking way too much.
What uncfnp said.
Every dive computer uses an algorithm/model that someone else thinks is safe. As far as I know, there is no evidence that any algorithm/model keeps divers safer than any other. I'll stick my neck out here and assert that, based on the available data, a Petrel running Buhlmann (with conservatively chosen GFs) or VPM cannot be shown to be any more safe or any less safe than a Suunto.
As far as conservatism settings, my guess (I don't know) is that Shearwater chose 40/85 as the Petrel's Rec Mode default setting because they believe it approximates the conservatism of other popular brands of recreational dive computers. But the Petrel does allow you, even in Rec mode, to choose a higher or lower conservatism, just like some other brands. In Rec mode, the Petrel works pretty much just like any other recreational dive computer.
My point is that it is a non trivial problem to figure out what is sensible GF or VPM number to use.
By using the rec mode on a Petrel or another fixed mode computer you are buying some expertise regarding what sensible means in the general population.
If we assume a 'recreational' diver is one who isn't doing deco dive (rather than the more conventional meaning of just wanting to have fun) then presumably they have not done a deco course. Thus what they know they will find from the Internet or maybe books and papers. If it was suggested that they use such knowledge to do deco dives then I think that would be shouted down by the SB convention against diving beyond your training.
Is setting the GF to 100/100 or using VPM 0 because they give the best NDL without having any training a good idea?
So you are against using any "fixed mode computer"?
No, I am very much in favour. This quote regarding using an algorithm deemed safe by someone else being a bad idea was Jim Lapenta's.
The vast majority of divers have no idea what the GF or VPM numbers mean or where a given set of numbers falls in risk terms absolutely or compared to some computer they may have experience of.
I agree, it is never trivial to use any DC you do not know how to use.
As to your question, and I hope someone with more knowledge about algorithms will jump in since I am just a receational diver..
A dive on air to 100 feet rough estimates
DSAT at 0 NDL 19 mins
PZ at 0 NDL 16 minutes
VBM at 0 will start to show mandatory stop at 17 minutes
Bulhmann at 100/100 will start showing mandatory stop at 17 minutes
PADI RDP NDL 20 minutes - thanks for reminding me about Padi Tbone 1004
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My apologies. I completely missed your use of quotation marks--I guess I'm accustomed to seeing the quote feature used. And now I see what you quoted from Jim's comment and how you ran with it. Sorry I wasted my time with this.
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sorry for this post, I'm at a conference so this is initially responding to post 31, and responding through the thread.
I don't have one, you will almost never see me recommend their gear. Their regulators come up on occasion because they're cheaper than their SP equivalents, but I can't think of anything else they have that is worth the money they charge. Their wing inner bladders are nice, but their plates are identical to the ones Scubapro sells minus a bit of extra polishing, webbing is webbing, and now that DRiS has knocked off the Eclipse 30 wing shape with theirs, it's tough to justify. Their gear is not over-engineered, it is just different. They wanted a fabric laminate for their bladder, that is literally the only noticeable difference that they have, it makes the wings more flexible and slightly lighter than the thick butyl rubber but comes at an extraordinary cost increase *material is about an order of magnitude more expensive* with negligible real benefit.
Regarding being harsh, yes I understand, the important part of it is that there is no difference in the needs of recreational and technical divers on a fundamental level. You want functional, high quality, simple, reliable, good value. Is it ridiculing if someone comes on here and asks for opinions on their gear when they come in with an overly expensive AI computer, split fins, jacket bc? Absolutely because if they had done their research they would have realized that you can purchase higher quality, more versatile, better gear for the same amount of money or less. Researching gear is great, I do it all the time to make sure that I make the best decision for me, unfortunately what people perceive as needs are usually ingrained on them by an instructor or dive shop who didn't know better. I have yet to see an argument for a stab jacket, a single argument where it makes sense, they are an inferior design, there is no debate on that unless you have a reason I haven't seen yet. There is no argument for split fins, they are literally useless, overpriced, and gimmicks.
Transpac got mentioned, you will never see me bash the transpac, the travelpac yes, but the transpac never. I have two, love them to death, will never get rid of them, they are fabulous, but they are still modular and much higher quality than any stab jacket I have seen.
Abstract, computers are different. The Zoop to me has no value, it has an irritating unpredictable algorithm, it does not have gauge mode, it does not have the option for multiple gasses *VERY important feature actually even if you aren't in deco because you can program your two gasses for the day of diving and switch instead of having to reprogram it between dives*, and downloading to the computer is expensive because the cable is almost as expensive as the computer. It also locks you out, which is horrible, and not a feature but a travesty. No computer should ever lock you out for 24 hours, it should just track your nitrogen levels and adjust accordingly.... This is important because if you don't have a computer designed for decompression and you are in an emergency situation and have to blow safety stop or have to stay down past NDL's, you can't come back down to complete your decompression after bringing a diver to the surface, safety issue imho, this could save you a trip to the chamber.... *extreme I know, but I plan for the worst and hope for the best*
Ken brought up algorithms, people get spooked by GF's. The Petrel Rec. Nitrox manual tells you that the least conservative mode is comparable to the PADI tables, so it only gets safer from there. The choice is very trivial, no matter what you do, you are no worse off than diving PADI tables. If you choose to be more conservative then you can choose, but since the PADI tables have you coming up at equivalent of about 45/95, you can't get any less conservative, so it is completely trivial. You have low/med/high conservatism, pick one. Most people I know run 30/70 which is stupid conservative.
You also don't have to use the rec mode, there is plenty of literature on gradient factors, and the concept is very simple. For recreational dives, basically ignore the first number, and for the second one, you get to choose how conservative you want to be. We know PADI tables are similar to 45/95 or whatever it says in the manual. If you want to be more conservative, be more conservative, if you don't, then don't. The second number is an approximation of the percentage of nitrogen loading in your system when you surface. Which, if you actually paid attention in your scuba class and have a brain, says that "hrrm, if I stop a couple stops short of the NDL on my dive tables I'm coming up with less tissue saturation", so it is literally no different than deciding if you want to go to full NDL's on tables, or coming up early. If you can't figure that out, you probably should be doing this. Again, harsh I know, but I really don't care because it is literally that simple. Point of this, is you are using something that is making recommendations on how long you can stay down, if you don't read the manual where this is spelled out VERY clearly, then I really couldn't care less if you set it to 100/100 and get bent like a pretzel because you frankly deserved it. This is no different than any other computer with multiple conservatism settings, read the bloody manuals. Ken, I know you're playing devil's advocate, but you must have no faith in peoples ability to think *which mine is waning daily* if you're suggesting they're really that dumb
https://www.shearwater.com/wp-content/uploads/2014/03/PetrelManual_Nitrox_Rec_Mode_DocRevA.pdf
Page 18. 45/95 is similar to PADI and NOAA No-Stop times
This whole thing circles back to there is actually no difference in the needs of a recreational and technical diver from their gear. Certain specific features might be different, i.e. need for doubles, canister lights, need for trimix/ccr support, but the fundamental basics of the gear are all the same, computers included. If you need/want AI, the only one I would recommend is the SeaBear H3 which will have a transmitter coming out in a few months. It's just under a grand right now, so right in there with most of the other good ones, but that is at least a top quality computer.
The other point is that if you do this right the first time, there is no reason to ever have to "upgrade" because "upgrade" is not the term you want to use for this. Buy the regulators you need the first time, buy the BC you need the first time, there isn't a significant price change for anything except the computers, but with them you can stay cheap and still get a computer that you will never HAVE to replace, you might WANT to, but you will never be forced to. A stab jacket, a Zoop, split fins, none of these can grow with you as a diver, which involves trying to sell and spend more money. Just spend it right the first time. The other advantage, is that all of the "technical" gear retains better resale value on average, so that is another big advantage
I don't have one, you will almost never see me recommend their gear. Their regulators come up on occasion because they're cheaper than their SP equivalents, but I can't think of anything else they have that is worth the money they charge. Their wing inner bladders are nice, but their plates are identical to the ones Scubapro sells minus a bit of extra polishing, webbing is webbing, and now that DRiS has knocked off the Eclipse 30 wing shape with theirs, it's tough to justify. Their gear is not over-engineered, it is just different. They wanted a fabric laminate for their bladder, that is literally the only noticeable difference that they have, it makes the wings more flexible and slightly lighter than the thick butyl rubber but comes at an extraordinary cost increase *material is about an order of magnitude more expensive* with negligible real benefit.
Regarding being harsh, yes I understand, the important part of it is that there is no difference in the needs of recreational and technical divers on a fundamental level. You want functional, high quality, simple, reliable, good value. Is it ridiculing if someone comes on here and asks for opinions on their gear when they come in with an overly expensive AI computer, split fins, jacket bc? Absolutely because if they had done their research they would have realized that you can purchase higher quality, more versatile, better gear for the same amount of money or less. Researching gear is great, I do it all the time to make sure that I make the best decision for me, unfortunately what people perceive as needs are usually ingrained on them by an instructor or dive shop who didn't know better. I have yet to see an argument for a stab jacket, a single argument where it makes sense, they are an inferior design, there is no debate on that unless you have a reason I haven't seen yet. There is no argument for split fins, they are literally useless, overpriced, and gimmicks.
Transpac got mentioned, you will never see me bash the transpac, the travelpac yes, but the transpac never. I have two, love them to death, will never get rid of them, they are fabulous, but they are still modular and much higher quality than any stab jacket I have seen.
Abstract, computers are different. The Zoop to me has no value, it has an irritating unpredictable algorithm, it does not have gauge mode, it does not have the option for multiple gasses *VERY important feature actually even if you aren't in deco because you can program your two gasses for the day of diving and switch instead of having to reprogram it between dives*, and downloading to the computer is expensive because the cable is almost as expensive as the computer. It also locks you out, which is horrible, and not a feature but a travesty. No computer should ever lock you out for 24 hours, it should just track your nitrogen levels and adjust accordingly.... This is important because if you don't have a computer designed for decompression and you are in an emergency situation and have to blow safety stop or have to stay down past NDL's, you can't come back down to complete your decompression after bringing a diver to the surface, safety issue imho, this could save you a trip to the chamber.... *extreme I know, but I plan for the worst and hope for the best*
Ken brought up algorithms, people get spooked by GF's. The Petrel Rec. Nitrox manual tells you that the least conservative mode is comparable to the PADI tables, so it only gets safer from there. The choice is very trivial, no matter what you do, you are no worse off than diving PADI tables. If you choose to be more conservative then you can choose, but since the PADI tables have you coming up at equivalent of about 45/95, you can't get any less conservative, so it is completely trivial. You have low/med/high conservatism, pick one. Most people I know run 30/70 which is stupid conservative.
You also don't have to use the rec mode, there is plenty of literature on gradient factors, and the concept is very simple. For recreational dives, basically ignore the first number, and for the second one, you get to choose how conservative you want to be. We know PADI tables are similar to 45/95 or whatever it says in the manual. If you want to be more conservative, be more conservative, if you don't, then don't. The second number is an approximation of the percentage of nitrogen loading in your system when you surface. Which, if you actually paid attention in your scuba class and have a brain, says that "hrrm, if I stop a couple stops short of the NDL on my dive tables I'm coming up with less tissue saturation", so it is literally no different than deciding if you want to go to full NDL's on tables, or coming up early. If you can't figure that out, you probably should be doing this. Again, harsh I know, but I really don't care because it is literally that simple. Point of this, is you are using something that is making recommendations on how long you can stay down, if you don't read the manual where this is spelled out VERY clearly, then I really couldn't care less if you set it to 100/100 and get bent like a pretzel because you frankly deserved it. This is no different than any other computer with multiple conservatism settings, read the bloody manuals. Ken, I know you're playing devil's advocate, but you must have no faith in peoples ability to think *which mine is waning daily* if you're suggesting they're really that dumb
https://www.shearwater.com/wp-content/uploads/2014/03/PetrelManual_Nitrox_Rec_Mode_DocRevA.pdf
Page 18. 45/95 is similar to PADI and NOAA No-Stop times
This whole thing circles back to there is actually no difference in the needs of a recreational and technical diver from their gear. Certain specific features might be different, i.e. need for doubles, canister lights, need for trimix/ccr support, but the fundamental basics of the gear are all the same, computers included. If you need/want AI, the only one I would recommend is the SeaBear H3 which will have a transmitter coming out in a few months. It's just under a grand right now, so right in there with most of the other good ones, but that is at least a top quality computer.
The other point is that if you do this right the first time, there is no reason to ever have to "upgrade" because "upgrade" is not the term you want to use for this. Buy the regulators you need the first time, buy the BC you need the first time, there isn't a significant price change for anything except the computers, but with them you can stay cheap and still get a computer that you will never HAVE to replace, you might WANT to, but you will never be forced to. A stab jacket, a Zoop, split fins, none of these can grow with you as a diver, which involves trying to sell and spend more money. Just spend it right the first time. The other advantage, is that all of the "technical" gear retains better resale value on average, so that is another big advantage
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