Buddies kept grabbing/pulling me to ascend faster than computer said was safe

[chrisch]

..... I doubt if the buddy realized the initial problem the op had with operating her BCD and the very conservative ascent rates mandated by the op's computer. ...

There was no issue operating the BC simply that she had been told something that wasn't true. This does not fill me with confidence in respect of the people around her. Why do you say the computer has a very conservative rate of ascent? I am unaware of any computer manufacturer (ScubaPro in this case) that aims for anything other that profiles that are safe and likely to be as safe as possible for the widest range of divers. To do otherwise is to invite litigation after all. If too slow an ascent is problematical the computer would not mandate it. The objective fact that the computer showed a violation is the only objective fact there is as far as I can see. The rest is mainly conjecture on our part.

 

[EFX]

You don't need calculations to understand the overall point.

Well, apparently the poster didn't get the point that some slower tissues can on-gass when you ascend. He thought all tissues should off-gass. This concept is not intuitive. After reading what others had said he didn't believe them and asked for the math. So, I gave him an example that included the math.

The statement that there is on-gassing during the ascent is - at a pedantic level - true of every dive you make.

Not true. Depends on the dive profile.

 

[chrisch]

Well, apparently the poster didn't get the point that some slower tissues can on-gass when you ascend. He thought all tissues should off-gass. This concept is not intuitive. After reading what others had said he didn't believe them and asked for the math. So, I gave him an example that included the math...

Neat. You got it wrong though didn't you?

 

[Basking Ridge Diver]

Neat. You got it wrong though didn't you?

Said the Kettle to the Pot.... Go back and read the top section of Post 166.

 

[chrisch]

Said the Kettle to the Pot.... Go back and read the top section of Post 166.

I cannot see any erroneous calculations in that post. But you have made my point well - thank you. Even if you understand the mathematical model that is a decompression algorithm it is easy to get it wrong. (We are human after all not computers) I have tried to demonstrate as best I can that the maths is not needed. Perhaps I didn't get that point over clearly enough. I am now waiting for someone to rip ScubaPro to shreds for their preferred ascent rates.......

 

[Kharon]

I am unaware of any computer manufacturer (ScubaPro in this case) that aims for anything other that profiles that are safe and likely to be as safe as possible for the widest range of divers. To do otherwise is to invite litigation after all. If too slow an ascent is problematical the computer would not mandate it. The objective fact that the computer showed a violation is the only objective fact there is as far as I can see. The rest is mainly conjecture on our part.

+1. Also, does any computer vary from the rate of 30'/min?????? Every computer manual I've looked at states an ascent violation at more than 30'/min for a stated period of time. Seems a standard. Don't see how any computer could be considered "conservative" on ascent rate.

 

[nimoh]

I cannot see any erroneous calculations in that post. But you have made my point well - thank you. Even if you understand the mathematical model that is a decompression algorithm it is easy to get it wrong. (We are human after all not computers) I have tried to demonstrate as best I can that the maths is not needed. Perhaps I didn't get that point over clearly enough. I am now waiting for someone to rip ScubaPro to shreds for their preferred ascent rates.......

you should read it again. In particular, read boulderjohn's response.

 

[chrisch]

+1. Also, does any computer vary from the rate of 30'/min?????? Every computer manual I've looked at states an ascent violation at more than 30'/min for a stated period of time. Seems a standard. Don't see how any computer could be considered "conservative" on ascent rate.

The OP uses a Galileo Luna. This model employs a variable ascent rate. This ranges between 7 and 20 m/min (which is 21-60 feet/min) the ascent violation warning occurs at 110% of ascent rate.

The manual is here: http://www.scubapro.com/media/101606/galileo_luna_eng.pdf

Page 41 is the one to read. The max depth of the dive was 90 feet and the computer allows an ascent rate of 43 feet per minute at the start of that ascent. Not even remotely "conservative" indeed faster than the 30'/min we sem all to have agreed upon.

As the diver ascends the speed is decreased until it slows to 21'/min for the last part of the dive. This is in keeping with the best thinking available to the best of my knowledge. From deep (over 50m) come up faster to prevent the on-gassing being discussed. (Not at 90 feet) Slow the rate as you ascend.

This computer model is designed for advanced deep diving well beyond the scope of the OP. The ascent rate part of it's algorithm is very much IMPO "good enough" to be followed by a person at AOW level without too much worrying about it's ability to get them to the surface unbent.

---------- Post added May 7th, 2015 at 02:57 PM ----------

you should read it again.... .

Why? has it been edited? There are no deco gas algorithm calculations in it.

 

[Basking Ridge Diver]

Why? has it been edited? There are no deco gas algorithm calculations in it.

You are correct there are no calculations there - you have the concept wrong...

Read his response and if needed I will explain how half times work... hint hint...

 

[redacted]

+1. Also, does any computer vary from the rate of 30'/min?????? Every computer manual I've looked at states an ascent violation at more than 30'/min for a stated period of time. Seems a standard. Don't see how any computer could be considered "conservative" on ascent rate.

My older computer (Oceanic Data Plus) uses a constant ascent rate limit of 60 ft/min. My VEO 200 uses 60 ft/min below 60 ft depth and 30 ft/min above 60 ft.

So, my VEO200 is more conservative on ascent rate than my Data Plus. And a LUNA is more conservative than my Data Plus throughout the recreational diving range of 0 to 130 ft. My Data Plus is more conservative than the LUNA at some depths greater than 130 ft.

Apparently there is no DCS incident data that suggests that any of these computers is unsafe.