Feedback on recent two-tank and dive limits

[grantmac]

I loan my backup Perdix all the time, BECAUSE it's far easier to use and under than any of the "recreational" computers out there. It's a 30 second conversation at most.

 

[Belzelbub]

I loan my backup Perdix all the time, BECAUSE it's far easier to use and under than any of the "recreational" computers out there. It's a 30 second conversation at most.

Exactly. A few years back, I did a bit of an experiment with one of my dive buddies. I had read the Perdix manual, so wouldn't be a good test case. My buddy, at the time, had only seen the Perdix on my wrist, but had never even touched one.

He was using a Cressi Donatello (might be a Michaelangelo) computer. He was getting a bit frustrated with it, and asked me how difficult it was to change the gas mix. Rather than tell him, I just handed him my Perdix, and told him to see if he could figure it out. The only instructions I gave him was how to turn it on. Once the computer booted up, he pushed the buttons a few times and quickly got to the screen. Might have taken 1 minute total from me handing him the computer.

He bought a Perdix 2 a couple of weeks ago.

 

[boulderjohn]

He was using a Cressi Donatello (might be a Michaelangelo) computer. He was getting a bit frustrated with it, and asked me how difficult it was to change the gas mix. Rather than tell him, I just handed him my Perdix, and told him to see if he could figure it out. The only instructions I gave him was how to turn it on. Once the computer booted up, he pushed the buttons a few times and quickly got to the screen. Might have taken 1 minute total from me handing him the computer.

In contrast, ...

1. I dive annually with a friend who uses an Oceanic computer. She does not dive in between those trips. Every trip begins with her staring at the manual trying to figure out how to set the nitrox, even though she has owned the computer for a decade. If she were to ask me to do it, I wouldn't have a clue.

2. I was working with a number of different recreational students on different classes, and the ones not working with me on a particular dive would often just dive on their own. One time we surfaced at the end of the dive and one of the ones I was not then teaching said that his computer (Suunto) was acting funny during the ascent. When he described what it was doing, I realized he had gone into deco, and the computer was telling him to do deco stops. I immediately took him down to 20 feet, where I saw that the computer was in error mode--there was no way of knowing how long he had been in deco, what kind of stops he had missed, etc. We just stayed at 20 feet for 15 minutes, after which we surfaced, and I put him on oxygen for a while just to be safe.

 

[Belzelbub]

I realized he had gone into deco, and the computer was telling him to do deco stops. I immediately took him down to 20 feet, where I saw that the computer was in error mode--there was no way of knowing how long he had been in deco, what kind of stops he had missed, etc. We just stayed at 20 feet for 15 minutes, after which we surfaced, and I put him on oxygen for a while just to be safe.

Throughout this thread, OF has repeatedly claimed that computers running Buhlmann are no good for new divers, and that they may in fact be dangerous (based on poster’s opinion that Buhlmann with GFs are suitable only for tech).

That Suunto is what sounds dangerous. The new diver is the one that needs the most guidance. First, it actually went into deco, and the diver didn’t realize. Second, it locked completely preventing anyone from telling the severity.

Contrast that with my Perdix. I was diving with a friend, and working on freeing an anchor line. I handed him my knife, and after cutting it, handed it back. I resheathed it, and realized he was gone. The rest of us looked, but water was clear, so he could only have gone up. He was low on gas and made a direct ascent. He swaps to another tank and went back down to do a safety stop (though unnecessary). His wife was freaked out. I showed her the tissue loading graph on my computer, and explained what it was. She relaxed quite a bit, when she saw none of the bars were anywhere near the red.

 

[rongoodman]

The only time I ever missed any deco was on a back-up Shearwater while diving my Prism 2 rebreather--I hadn't set the set-point correctly on it. It spoke sternly to me, I realized what I had done wrong, and ignored it.

 

[old frogman]

Interesting flyfishing exercise so far.

Let' look at a scenario. You have a son or daughter somewhere between 16 and 18 years of age and they have just completed their basic open water course, and you are going to give them an entry level Shearwater Peregrine dive computer or one similar with Buhlman and GF algorithm. What precautions are you likely to take to make him or her safe when using this dive computer? Or are you just going to give him or her the dive computer and just say read the user manual and figure it out.

So far no one has answered this simple scenario question which is designed to test my point of view. All I have seen so far is various persons kicking the can down the road, going off on different tangents extolling the virtue of the Peregrine or the value of GUE basic recreational dive course.

I agree the Peregrine and Buhlmann GF is a great unit. But should it be in the hands of the newly certified recreational diver, as per the scenario question.

From the lack of a decisive answer so far, my only conclusion is that you guys are unsure and have doubts about this computer and others with the Buhlmann GF algorithm. Absence of a clear decisive answer speaks very loudly.

For those that may be confused there are two possible answers:
a. Yes, with additional precautions to make him or her safe with the dive computer.
b. Yes, just give him or her the dive computer and just say read the user manual and figure it out.

 

[Blackcrusader]

So far no one has answered this simple scenario question which is designed to test my point of view.

We have answered you in our posts in this thread. Even a diver starting out doing an OW course should use a dive computer such as the Peregrine with GF settings. Although most new divers just choose a DC for being the cheapest and end up with RGBM Suunto which takes more to learn how to use properly, 4 buttons to push vs two on the Peregrine. Peregrine features much easier to use and learn. RGBM and GF factors are just features the DC's use. So are the settings for conservative to lesser conservative.

You claim new divers should use tables but they are not taught anymore. Good instructors will know both RGBM and GF dive computers and default NDL settings. You need to keep up with the times. You conlusions that we are unsure that a new diver should be using a DC with GF is your delusion not ours.

Your point of view is that new divers are too inept to be able to learn about the DC they use and be told to RTFM and ask questions about the settings on the DC they use. What you should focus on is why new divers do not do so and perhaps why in this day and age there are not more classes on dive computers for newer divers.

The OP admitted he did not know what settings the Peregrine was using. IF he was using a Suunto with RGBM he would still have not known what settings the DC was using. This was simply a diver who used a DC he did not even understand what settings it had. This is a failure of the diver not the result of the dive computer being too complicated.

Also you have shown in your posts you don't even know how Shearwaters with Buhlmann / GF settings work. You make false claims about them. So anyone reading your posts on Shearwaters using GF should just ignore you.

I've met many newly certified divers with Peregrines. They love the simplicity of the Peregrine for NDL diving. So simple to use, much easier than a Suunto. Yes they do need to read the manuals to fully understand the DC. You should stop posting that new divers cannot learn and understand their DC's that use GF. That is simply wrong of you to assume so.

Even as an experienced diver I found my Suunto a PITA to use. 4 stiff buttons, a cover screen I would have to remove to clean as it would gunk up, difficult to see on low vis or night dives.

Shearwater DC's I would recommend to any diver. A good dive buddy of mine, very experienced, was using Oceanics for a very long time. Several years ago in Bali his Oceanis were acting up and one flooded. Lucky he had a backup. Anyway he got some envy when he would see my Perdix digital display so bought one. Then we spent an hour with his new Perdix, did a firmware upgrade then he set it up as he wanted. He said so simple to choose screen colours and what he wanted on his Perdix.

 

[inquis]

So far no one has answered this simple scenario question which is designed to test my point of view.

Answered 2 posts after your question. BTW, you didn't answer this:

Do you understand that class covers computer use?

That newly certified diver will be pretty safe, as 1) they've been trained to look for the NDL number on a computer and 2) the default settings are fine. It's really not hard to shallow up when the displayed remaining NDL gets low. Zero understanding of GFs required.

 

[inquis]

@old frogman, we get that you like tables. Would you not agree that there is no practical difference between:

• Looking at a table to get an "ascent number" then monitoring a number on a watch until it gets close to that number
• Monitoring a number on a computer (i.e., the displayed NDL) until it gets close to 0

Neither of these require understanding of the underlying algorithm. All either requires is sufficient attention.

 

[JMarc]

a. Yes, with additional precautions to make him or her safe with the dive computer.

That's my answer. With the important additional note that's the additional precautions would be the same as for any computer, whatever the underlying deco model, whatever the interface and that I find the interface of the Peregrine less susceptible of confusion than the one some other computers marketed at beginners.