CAT calculation for GUE Fundies

[johnkendall]

10 minute ascent from 100 fsw ?

When calculating minimum gas, Yes. It is calculated assuming that you will ascend no slower than 10' per min.
For a normal ascent, we would ascend at 30' per min to half max depth, and then 10' per min from there.

HTH
John

 

[mainedvr]

What ATA are you at the surface?

1 and 100' is 3ATA+1', I do understand ATA and all that I just noticed that the gas planning has changed slightly and was wondering why they added 1ATA to the 4ATA for the average ATA for figuring MG. I also see in the following pages I am reading when they do 60' its and average for calculation of 2ATA 3ATA for 60" +1ATA (3ATA+1/2).

Thanks for all the responses, it seems that they are adding the 1 ATA to do an average not conservetisim, at least from one of the post I have read'


Thanks again

 

[mainedvr]

When calculating minimum gas, Yes. It is calculated assuming that you will ascend no slower than 10' per min.
For a normal ascent, we would ascend at 30' per min to half max depth, and then 10' per min from there.

HTH
John

John that also brings up another thing I saw they calculated the ascent time from 100' at 11minutes 10'pm with 1min for getting set to accend. Not what I have seen likeyou posted 30'pm to half max depth then 10'pm to surface/

 

[johnkendall]

John that also brings up another thing I saw they calculated the ascent time from 100' at 11minutes 10'pm with 1min for getting set to accend. Not what I have seen likeyou posted 30'pm to half max depth then 10'pm to surface/

As I said above, the normal ascent is 30' per min to half and then 10' per min. But for Min Gas, we build in conservatism by assuming that the ascent might end up being slower. And yes, add at least 1 minute to the ascent time to allow for time to actually donate a reg and get ready to ascend.

 

[Rainer]

When calculating minimum gas, Yes. It is calculated assuming that you will ascend no slower than 10' per min.
For a normal ascent, we would ascend at 30' per min to half max depth, and then 10' per min from there.

So 55cf for min gas for a 100' dive (2*2.5*11)? That's certainly more conservative than when I took Fundies (>10 years ago now). We were taught to add 1min to sort the issue on the bottom, but then used the typical ascent rate rules for determining total ascent time. When did this change? Is GUE teaching the same at T1+ for min gas (i.e. 10'/min from the bottom to the gas switch)? That's *a lot* of gas.

Thanks!

 

[CptTightPants21]

So 55cf for min gas for a 100' dive (2*2.5*11)? That's certainly more conservative than when I took Fundies (>10 years ago now). We were taught to add 1min to sort the issue on the bottom, but then used the typical ascent rate rules for determining total ascent time. When did this change? Is GUE teaching the same at T1+ for min gas (i.e. 10'/min from the bottom to the gas switch)? That's *a lot* of gas.

Thanks!

Agreed. We had 40cuft of min gas for 100' 2 x 2.5 x 8 (1 min sort out, 2 min to ascend to 50, 5 min ascend to surface)

 

[guruboy]

I also see in the following pages I am reading when they do 60' its and average for calculation of 2ATA 3ATA for 60" +1ATA (3ATA+1/2).

Huh? Maybe you need to re-type that...

For 60', let's just call it 66' aka 3ATA. Average would be (3+1)/2 = 2 ATA average

Thanks for all the responses, it seems that they are adding the 1 ATA to do an average not conservetisim, at least from one of the post I have read'

You are calculating the average ATA for gas consumption purposes. It is not conservatism.

The average between two points (assuming a linear change) is (START + FINAL) / 2.

So with that assumption, ((ATA at Depth) + (1 ATA at Surface)) / 2 = ATA Average

 

[guruboy]

People seem to be confusing two ascent methods.

For a min gas calculation, you determine the ascent time by using 10fpm the entire way, with 1 minute added for "sorting things out" between the start of the incident and starting the ascent.

This is NOT the normal ascent profile.

 

[Rainer]

People seem to be confusing two ascent methods.

For a min gas calculation, you determine the ascent time by using 10fpm the entire way, with 1 minute added for "sorting things out" between the start of the incident and starting the ascent.

This is NOT the normal ascent profile.

This is not how it used to be taught. Hence my questions to John.

 

[johnkendall]

So 55cf for min gas for a 100' dive (2*2.5*11)? That's certainly more conservative than when I took Fundies (>10 years ago now). We were taught to add 1min to sort the issue on the bottom, but then used the typical ascent rate rules for determining total ascent time. When did this change? Is GUE teaching the same at T1+ for min gas (i.e. 10'/min from the bottom to the gas switch)? That's *a lot* of gas.

Thanks!

You'll have to forgive me a little as I tend to work in metric, but no.

2 x 0.75 x 2.5 x 11
Use normal SCR for this calculation, so it should come out similar to the old calculation.