Tech1 Ratio Deco - Explained

[Mark Chase]

Originally Posted by GLOC

If you are on 32% (which GUE advocate) then the limit for 30m is 30mins and you can use plus or minus 5mins for 3m to about 21m and then it starts breaking down.

A rough and ready table is available here.

I am sure there is another one available from GUE which I will try and source now.

ATB

Mark Chase

[Mal Bridgeman]

Mark

The Ascent times on the 32% table looks different to what I was taught on my Fundies class.

We were taught 9m/min to half the average depth rounded to the next deepest depth cleanly divisible by 3 then 3m/min thereafter.

So from 21m Ascend to 12m at 9m/min so 1 min expired, 1 min to get to 9, 1 to 6 1 to 3 then 1 to the surface giving a total of 5 mins.

Is that what others who did the course recently do?

Mal

[neilh]

Originally Posted by Mal Bridgeman

We were taught 9m/min to half the average depth rounded to the next deepest depth cleanly divisible by 3 then 3m/min thereafter.

...

Is that what others who did the course recently do?

I actually go a bit more conservative:
9M/min to 50% depth, then
3M/min to 6M and 3 min stop @6 (clears computers and gives a bit of a break), then
1M/min to surface

Not everyone I dive with is using a gauge/timer hence the 3min stop.

[Garf]

Originally Posted by Mal Bridgeman

Mark

The Ascent times on the 32% table looks different to what I was taught on my Fundies class.

We were taught 9m/min to half the average depth rounded to the next deepest depth cleanly divisible by 3 then 3m/min thereafter.

So from 21m Ascend to 12m at 9m/min so 1 min expired, 1 min to get to 9, 1 to 6 1 to 3 then 1 to the surface giving a total of 5 mins.

Is that what others who did the course recently do?

Mal

That's what I was taught, but not what I do. I would slow the final portion of the ascent to 1M per minute from 6 metres, simply becuase this is what we do on every dive, regardless of what type of dive it is.

[Kev]

Thanks to Mal for pointing me at this thread. It is really very interesting.

I understand that this method seeks to control the gas mixes so that in a given range of exposures to depth and time the ratio calculations will work by approximating what your deco obligations will be.

I have two questions:

1. What underlying decompression model is this based on?

2. What are the results of using this method in practice and / or testing i.e. has it been used or tested widely without lots of people bending themselves silly?

Just for the sake of clarity I am not planning on doing any diving with mandatory stops anytime soon, I am just interested in the theory.