Cressi Leonardo- Too conservative?

[lowviz]

Your two highlighted statements seem to be at odds with each other.

They most certainly are.

sarcastic - intent to offend
sardonic - disdainfully or skeptically humorous
ironic - attempt to amuse

I was trying for the last one.

The OP asked if anyone has had similar experiences to his, which are that his Leonardo is cutting his dives short compared to people he's diving with that have other computers. I gave links to reviews of various computers with actual repetitive dive data, that the OP can use to compare how different DCs behave. I've also taken exception to your implication that people who have a computer and want one that is less conservative are *ahem* uninformed. Is there really any more to say on any of that?

No, you have completely captured the subject.

My question about why anyone would want to buy a PDC for Rec diving that arbitrarily restricts their bottom time was based on several ideas that I believe are correct: One, all the computers in question are generally accepted as safe (regarding the algorithms they use).

Incorrect. Approximately 20% of the population have a PFO to some varying degree. Obesity is an issue, so is general unfitness, age, hydration...

Two, all the major manufacturers (of Rec computers) make (Rec) DCs with comparable feature sets. Thus, the implication (by me) that computers with more conservative bottom times are arbitrary

There is a bigger picture to look at. Some algorithms penalize you for saw tooth dives, others for slow ascent rates off the bottom, some give you a deep stop, others penalize you for it. All this just shows up as a prediction as to when to leave the bottom. You see this as arbitrary. In a way it is, but it is also nice to pick a DC that tends to suit you. I'd make different recommendations for a 20 y/o healthy athlete vs. a more typical vacation diving senior citizen.

- because others with less conservative BT are accepted as safe.

"safe" is a funny word when applied to the diving population at large. So, since they are all commercially available, none of them can hurt you if you follow them?

instead of telling people "I'm a lot more experienced than you and this is good enough for me, so you should accept it as good enough for you."

First, I never mentioned my level of experience or understanding. My opinion is that the Leonardo is a nicely designed computer that would be appropriate for MOST of the diving population that just want something to tell them when it is over.

And instead of snarkily deriding people who ask about computers with more liberal algorithms - especially when they have dive experience that has SHOWN them that what they are using is more conservative than what they want.

I offered an opinion that differs from yours, it was not a personal attack.

 

[stuartv]

all the computers in question are generally accepted as safe (regarding the algorithms they use).

Incorrect. Approximately 20% of the population have a PFO to some varying degree. Obesity is an issue, so is general unfitness, age, hydration...

Can you identify any specific examples of the computers in question that are not generally accepted as safe (regarding their algorithms)? If not, then can you elaborate on what is incorrect about my statement?

---------- Post added December 30th, 2014 at 12:25 PM ----------

There is a bigger picture to look at. Some algorithms penalize you for saw tooth dives, others for slow ascent rates off the bottom, some give you a deep stop, others penalize you for it. All this just shows up as a prediction as to when to leave the bottom. You see this as arbitrary. In a way it is, but it is also nice to pick a DC that tends to suit you. I'd make different recommendations for a 20 y/o healthy athlete vs. a more typical vacation diving senior citizen.

My apologies. I should not have said they are arbitrary. What I should have said that they are presumptuously conservative. They presume that your personal characteristics would not allow you to safely dive with a more liberal BT allowance.

 

[Freewillow]

I agree that it may end up beeing dangerous to select a computor that let you surface ahead of the other divers. In fact on my replacement computor, I have a conservative level of +2 - the safest option. ( Bühlmann G16 with 80/120% on desat/sat) . But I also agree that people should not "follow" stupidly their computors without understanding it.

This is why I believe that the Cressi Leonardo is not a good computor FOR MY STYLE OF DIVING.

What I do not understand is that the NDL does not increase significantly when you are going shallower ( see my explanations on page 1 of this post)

What I do not understand is that when I am in DECO mode @ 7 to 8 m (20/23 feet ) my Leonardo manages to add minutes to my DECO time while other computer start to shorten the DECO obligations.

What I do not like is that for your last DECO stop @ 3m (10 feet), the count down barelly starts if you are @ 4M or slightly bellow. When you are diving in a pass of an atoll and you are finishing your deco obligations in 3 to 5 feet waves, you do not want to stop at 10 feet but rather a bit lower.

These are the 3 main reasons, why I believe that the LEONARDO is not good for MY practice.

Now if you are diving and staying very far from any deco obligations, it is a greet computor. High visibility on numbers, cheap. One button programming for me is a nonsense but this is another story

 

[lowviz]

...people should not "follow" stupidly their computors without understanding it.

Yes, but stupidly following a conservative computer can work well for those who care nothing about computers or their algorithms, I can accept that viewpoint as valid also.

This is why I believe that the Cressi Leonardo is not a good computor FOR MY STYLE OF DIVING.

Quite possibly so if that is how you need/want to ascend. Pick another algorithm.

What I do not understand is that the NDL does not increase significantly when you are going shallower ( see my explanations on page 1 of this post)

Many DC's just attend to the dissolved gas phase in tissues. So the plan is to just ascend as far as possible before you bubble. This increases the gradient between the inert gas in your blood and the same gas in your lungs making gas elimination efficient.

The Leonardo 'models' a dual phase system. The two phases are the dissolved gas in your tissues AND stable microbubbles in the same tissues. Now we have a conflict. A rapid ascent causes microbubbles to grow, bad thing.

So the model enforces a strict ascent profile that is intended to both "crush" the inert gas out of microbubbles (and into the dissolved phase) at depth and allow for a good gradient to get rid of dissolved gas through the lungs.

So if you just want to ascend with the Haldanean gang, you most certainly will be penalized by RGBM.

These are the 3 main reasons, why I believe that the LEONARDO is not good for MY practice.

Yep, pick another algorithm. Can't fault your reasoning.

I like RGBM because I'm usually near deco or in light deco and I just feel better at the end of the day using RGBM. I can ascend on an anchor line and have great control over my ascent profile.

BTW, I just got a sweet deal from my LDS on a Cressi Giotto. I can't wait to try it in caves where one's ascent profiles are highly constrained by the cave.

One button programming for me is a nonsense but this is another story

I'll loan you my cold water Kevlar gloves for your multibutton DC...

 

[Freewillow]

@lowviz, did you EVER dived with a Cressi Leonardo? Are you sponsored by Cressi?

My impression is that you never did.

If this is the case, everything you have done on this post is "enculer les mouches". Sorry for my french, this is my mother tongue.

If you have dived 50+ times like I did and have not noticed anything wrong with it, then I apologize. :angel2:

FYI, I have been told by 2 dive operators, that the Cressi leonardo is about the "worse" dive computor you can have in the tuamotus, where you start the dive between 30 and 40 meters, and le coral tables are at 10+ meters.

FYI, I have an OSTC where there are 2 buttons, one on each side of the computor and I do not dive with gloves

 

[lowviz]

@lowviz, did you EVER dived with a Cressi Leonardo?

No, I have not. I have dived extensively with that same algorithm, including diving the very restrictive RGBM tables.

Are you sponsored by Cressi?

No, no interests in Cressi.

My impression is that you never did.

You are correct and it is my intention to never mislead. All of my discussions center on the algorithm, not the box it comes in.

If this is the case, everything you have done on this post is "enculer les mouches". Sorry for my french, this is my mother tongue.

No need to apologize, your insult was quite clear even with my limited French.

If you have dived 50+ times like I did and have not noticed anything wrong with it, then I apologize. :angel2:

There is nothing wrong with the algorithm, however, it does require more attention on the ascent.

FYI, I have been told by 2 dive operators, that the Cressi leonardo is about the "worse" dive computor you can have in the tuamotus, where you start the dive between 30 and 40 meters, and le coral tables are at 10+ meters.

If everyone were diving RGBM, would the operators have the same concern? RGBM + Haldane will indeed split divers apart on ascent.

FYI, I have an OSTC where there are 2 buttons, one on each side of the computor and I do not dive with gloves

My point being that it is nice to have a choice. There isn't anything out there that works best for everyone.

 

[Freewillow]

The proof is in the pudding.

You have never dived with a Leonardo and you indicate that I am wrong in saying that I do not like it. Amazing .

End of the story for me, I take this post off my reading list. Too many flies casualties

 

[lowviz]

You have never dived with a Leonardo and you indicate that I am wrong in saying that I do not like it. Amazing .

If you polish your reading skills a bit and go back a few posts, you may just see that I agree with the point that it may not be the best DC/algorithm for you.

So the Cressi Leonardo contains an entirely proprietary variant of the RGBM algorithm?

I'm out too. Pleasure to make your acquaintance.

 

[stuartv]

So the Cressi Leonardo contains an entirely proprietary variant of the RGBM algorithm?

Man, or men (ladies?), let's not get pissy.

I have not dived a Cressi DC at all. But, I am a software engineer in my professional life. And I find the above statement to be exceedingly naive.

Algorithms are typically defined in an academic paper or similar. And rarely by actual mathematicians. Thus, they are often not defined in such a rigorous way that there is no room for interpretation by an implementer who is implementing the algorithm in software. Furthermore, unless the algorithm is defined by a particular software implementation, it is likely that every implementation of the algorithm will be proprietary. Unless someone implements it and contributes it to the public domain.

I have not studied the RGBM algorithm, so everything I say about it is just based on speculation tempered by many years of software development experience.

Based on the OP, I would have to speculate that the Leonardo may possibly use a simplified implementation that still complies with the algorithm specs. For example, instead of doing updated calculations based on current depth, it could be taking the max depth and just using that while watching for a threshold value, like the safety stop depth.

Anyway, I'm not trying to say that I know how they implemented the algorithm. I'm just saying that reality is that they could have taken a shortcut or two to implement it. Shortcuts which would make it simpler and also safer - obviously at the expense of bottom time. And your insinuation that every implementation of the RGBM algorithm is exactly identical is, in my professional opinion, naive.

 

[lowviz]

Look, Wienke worked and LANL developing simulations for nuclear weapons. Get his book and read it, I'm on my fourth try. You are telling me that a Leonardo can't do the calcs??? NO **** SHERLOCK!!! But I won't accept that the Leonardo's model of the grand model causes deviations on the order of magnitude that incense freewillow.

You want naive? Try this:

Based on the OP, I would have to speculate that the Leonardo may possibly use a simplified implementation that still complies with the algorithm specs. For example, instead of doing updated calculations based on current depth, it could be taking the max depth and just using that while watching for a threshold value, like the safety stop depth.

So, so gone...