Discrepancy in Subsurface and MultiDeco ZHL-C

[SeanW]

Greetings all,

I apologize if this has been talked about before. Has anyone noticed a large discrepancy in the dive plan when using multi deco and subsurface? An example: ZHL-C GF 60/80, 150 feet for 30 minutes on 21/35 w/ 50% deco gas.

Multideco run time: 69 minutes
Subsurface run time: 85 minutes

Both are configured the same based on my checks. Same descent, ascent, gas switch depth, gf, etc.

 

[Sebek]

Greetings all,

I apologize if this has been talked about before. Has anyone noticed a large discrepancy in the dive plan when using multi deco and subsurface? An example: ZHL-C GF 60/80, 150 feet for 30 minutes on 21/35 w/ 50% deco gas.

Multideco run time: 69 minutes
Subsurface run time: 85 minutes

Both are configured the same based on my checks. Same descent, ascent, gas switch depth, gf, etc.

For me MultiDeco says 90 minutes:

Des 150 - 2 21/35 - -
Lvl 150 27 30 21/35 1.14 86
Asc 70 - 33 21/35 - -
Asc 60 - 33 50 - -
Stp 60 0:24 34 50 1.38 26
Stp 50 3:00 37 50 1.24 19
Stp 40 3:00 40 50 1.09 13
Stp 30 3:00 43 50 0.94 7
Stp 20 27 70 50 0.79 0
Sfc - - 90 50 - -

Can you post the generated plan/settings?

 

[Sebek]

For me MultiDeco says 90 minutes:

Des 150 - 2 21/35 - -
Lvl 150 27 30 21/35 1.14 86
Asc 70 - 33 21/35 - -
Asc 60 - 33 50 - -
Stp 60 0:24 34 50 1.38 26
Stp 50 3:00 37 50 1.24 19
Stp 40 3:00 40 50 1.09 13
Stp 30 3:00 43 50 0.94 7
Stp 20 27 70 50 0.79 0
Sfc - - 90 50 - -

Can you post the generated plan/settings?

This plan is wrong though, because I switched from metric to imperial, but it still assumed 1 unit per minute ascent from the last stop... In any case, all I'm saying is that the settings matter a lot

 

[tursiops]

Greetings all,

I apologize if this has been talked about before. Has anyone noticed a large discrepancy in the dive plan when using multi deco and subsurface? An example: ZHL-C GF 60/80, 150 feet for 30 minutes on 21/35 w/ 50% deco gas.

Multideco run time: 69 minutes
Subsurface run time: 85 minutes

Both are configured the same based on my checks. Same descent, ascent, gas switch depth, gf, etc.

Did you match your descent and ascent rates, and actual time at 150 ft?
Did you match the depth at which you switch to 50%?

I get nowhere near 85 mins on Subsurface, much less in fact.

You can choose 16B or 16 C in MultiDeco; what is Subsurface using?

 

[SeanW]

Here are the settings and plan for MultiDeco

 

[SeanW]

And here is the settings and plan for Subsurface

 

[SeanW]

Hopefully this is a clearer image for subsurface.

 

[dmaziuk]

If I'm reading this right, you have a 1-minute stop at 70' and do you gas switch there in SS profile? As opposed to no-stop, just the gas switch "on the way" to the 60' stop in MD? I've no idea how much they should diverge from then on, but it will add up.

 

[dmaziuk]

PS @atdotde might be interested

 

[SeanW]

Update,

Not exactly sure what changed but when I opened up subsurface again today, it’s reading the same as MultiDeco. 68 minutes for both. Didn’t change anything