Free SSI Science of Diving Specialty

[Ben_3]

Comparing those two agency's tables is interesting.

 

[loosenit2]

So... I misplaced my good laminated copy of the SSI tables, so I just reprinted... And my printer is low on color ink apparently. Still usable, but looks ridiculous.
PADI;
View attachment 580839 View attachment 580840
SSI;
View attachment 580841 View attachment 580842
Simple version: slight layout change, SSI uses fewer pressure groups, is slightly more conservative on NDL times, and does longer emergency deco stops if you screw it up.
Complicated version: i don't know enough about the assumptions/models either agency used to answer that!

Respectfully
James

I had never looked at the tables side by side before but was doing so as you posted. I notice several other differences besides the ones you posted.

In addition to being more conservative (ie. PADI allows 10 min NDL at 130 ft whereas SSI only allows 5 min) the SSI tables give NDL limits at shallower depths. The PADI tables start at 35ft whereas the SSI tables start at 10 and move up in 5 ft increments up to 40 ft.

As you point out, SSI uses fewer pressure groups that are more narrowly grouped in the PADI tables vs the SSI tables. PADI uses A-Z PGs wheras SSI only goes to K. This allows someone using the PADI tables to be more precise in their SI calculations for repetitive diving. For example using PADI tables if a diver ends a dive in PG B it takes :48 min to get to A, in SSI it requires 3:21. In PADI a diver ending at K and wanting to get to C waits :55min, in SSI it takes 4:20

DSAT developed the PADI dive tables in 1988 to support recreational diving wheras SSI continues to base their tables off the U.S. Navy dive tables. I have read, but do not know for sure, that DSAT used the 60min tissue compartment as the controlling compartment for their table, which would allow for more repetitive dive dive time with shorter Surface Intervals; this would seem to match the audience they were catering too as recreational divers want to get more dives in with shorter SIs than a navy diver would (as gas supply is more likely the controlling factor).

All this leads to one somewhat obvious conclusion, don't switch between the dive tables in the same 24 hour period, like the ghostbusters said, crossing the streams is dangerous, never cross the streams.

 

[James79]

I had never looked at the tables side by side before but was doing so as you posted. I notice several other differences besides the ones you posted.

In addition to being more conservative (ie. PADI allows 10 min NDL at 130 ft whereas SSI only allows 5 min) the SSI tables give NDL limits at shallower depths. The PADI tables start at 35ft whereas the SSI tables start at 10 and move up in 5 ft increments up to 40 ft.

As you point out, SSI uses fewer pressure groups that are more narrowly grouped in the PADI tables vs the SSI tables. PADI uses A-Z PGs wheras SSI only goes to K. This allows someone using the PADI tables to be more precise in their SI calculations for repetitive diving. For example using PADI tables if a diver ends a dive in PG B it takes :48 min to get to A, in SSI it requires 3:21. In PADI a diver ending at K and wanting to get to C waits :55min, in SSI it takes 4:20

DSAT developed the PADI dive tables in 1988 to support recreational diving wheras SSI continues to base their tables off the U.S. Navy dive tables. I have read, but do not know for sure, that DSAT used the 60min tissue compartment as the controlling compartment for their table, which would allow for more repetitive dive dive time with shorter Surface Intervals; this would seem to match the audience they were catering too as recreational divers want to get more dives in with shorter SIs than a navy diver would (as gas supply is more likely the controlling factor).

All this leads to one somewhat obvious conclusion, don't switch between the dive tables in the same 24 hour period, like the ghostbusters said, crossing the streams is dangerous, never cross the streams.

I had heard much the same, but can't remember the references off the top of my head... I also seem to recall that part f the DSAT thought process was that Recreational divers would be doing as long of dives as the Navy, so would not be likely to saturate the longer half-time compartments. Therefore a shorter time compartment making reasonably safe sense as the control for purely recreational tables.
Turns out I'm no mathematician, and people have used both tables successfully for a long time. Like you said, just don't switch tables until fully off-gassed or you are inviting trouble.

My advice is always worth what you paid for it though, so there is that.

Respectfully,

James

 

[Angelo Farina]

I was grown up with US Navy tables, which are very strict on multiple dives per day. De facto they allow only for up to a second dive per day, with a long surface interval and with strong reduction of available time for the second dive.
When I was first introduced to Padi dive tables for repetitive dives (or the famigerate Padi Wheel), I was shocked seeing they are much more tolerant, allowing for even 4 dives per day, with limited surface intervals and long bottom times.
I did never consider them safe, and I always try to avoid to make multiple dives: for me it is better to make just one dive per day, but very good, instead of 3 or 4, but so-so...

 

[scubadada]

In my first diving period, from 1970-1980, I did a couple hundred dives using USN tables. These were mostly one dive per day, quite a few two per day, only a few at three per day.

Jump ahead to my second diving period, 1997 to the present. I initially did about 40 dives using PADI tables. Since 2002, I've done a little over 1850 dives using a primary computer running DSAT. Many of these dives have been 3, 4, and occasionally 5 dives per day. For what it's worth, I'm alive and kicking, waiting impatiently to get back in the water.

@Angelo Farina, I would hardly describe the PADI Wheel as famigerate. I skipped from PADI tables directly to DSAT computer

 

[saxman242]

At @Sloeber 's request, the original post has been edited. Looks like the specialty is now being offered at half off rather than free due to some pushback.

 

[scubadada]

At @Sloeber 's request, the original post has been edited. Looks like the specialty is now being offered at half off rather than free due to some pushback.

That's too bad, I just messaged Henry today, oh well.

 

[Angelo Farina]

@Angelo Farina, I would hardly describe the PADI Wheel as famigerate. I skipped from PADI tables directly to DSAT computer

Sorry, probably not the most correct term. What about "misterious"? I never understood how the Padi Wheel works...
I agree that a good computer is the definitive solution for multiple dives, or dives with variable-depth profile.

 

[scubadada]

Sorry, probably not the most correct term. What about "misterious"? I never understood how the Padi Wheel works...
I agree that a good computer is the definitive solution for multiple dives, or dives with variable-depth profile.

Famigerate is usually defined as notorious or infamous, some people probably do think of it that way. It certainly is a mystery to me, never used the wheel or the PADI calculator

 

[Sloeber]

That's too bad, I just messaged Henry today, oh well.

I can honor the Nitrox for you no worries. Some SSI shops were getting upset with the attention this thread was getting so SSI requested me to remove the pricing. But I'll still honor it for you. what was your name on the email you sent?