minimum surface interval

[ItsBruce]

Ditto for all the above, but I'll add: Depending on where you are located, I'd even be willing to sit down with you and the tables and walk you through their use until you can do your own calculations. ... And, if not me, then probably someone near you...

 

[tedtim]

You could also send a PM to Larry (username = Scubatoys) and ask him about table tutor software if you want a tool to help you through this and provide opportunity for practice.

 

[fisherdvm]

Each table is set up differently, so you would have to ask someone familiar with NAUI. Most OW books will walk you through at least one example. But I can't walk you through yours without seeing and understanding the layout of the NAUI tables.

 

[miketsp]

my question is what would the minimum surface interval required to avoid stage decompression after a dive to 70 feet of freshwater for 35 mins, followed by a dive to 55 feet of fresh water for 23 minutes be
gotcrypt

As the question is worded it depends on how much air you have available in your main cylinder(s).
Or did you mean to ask "to avoid obligatory decompression stops"?

Whatever, if you're qualified, this is not a question you should be having to ask.

 

[scubatoys]

my question is what would the minimum surface interval required to avoid stage decompression after a dive to 70 feet of freshwater for 35 mins, followed by a dive to 55 feet of fresh water for 23 minutes be
gotcrypt

Here is a link to that Computerized Table Tutor they were talking about: http://www.scubatoys.com/store/detail.asp?PRODUCT_ID=TableTutor

And here is a quick screen grab I did of the problem you're working on:

So the first part is easy... look at the red arrows, and it explains it in the box down to the bottom right. Your first dive of 70 for 35 minutes would make you a G diver. Now the question is if you want to do a 55 foot dive (which we know we'll have to round up to 60) and you want to do it for 23 minutes... how long must you wait?

Ok, I circled the area we want to look at in blue on the table. In the 60 column, go over from the G and you will see 2 numbers - a black 44 over a red 11. That means you have 44 minutes of residual nitrogen in your body... so you are only allowed to stay for 11 minutes. But we want to stay for 23 right? So moving up, if I got down to an F, I could stay for 19... still not enough. So go up a bit more an we see if we became an E diver, we could stay for 25 minutes. Bingo... We must wait long enough to be an E diver.

So now in the surface interval chart (#2) if you follow the G down from the first question and the E over... you get a box with 2 numbers 1:59 and 1:16. So to do your second dive, you would at least have to wait 1 hour and 16 minutes, as that would take a G diver down to pressure group E, who would be allowed to do a 60 foot dive for 25 minutes...

I hope that makes sense, and if you download the software, PM us the shareware number, we unlock it for free for ScubaBoard members, and it will do millions of table questions, including missing surface interval questions, and explain the solutions for each one, drawn out on the table - and in a profile.

Best of luck and congrats on getting certified! Let me know if I can ever help!

 

[MXGratefulDiver]

Ditto for all the above, but I'll add: Depending on where you are located, I'd even be willing to sit down with you and the tables and walk you through their use until you can do your own calculations. ... And, if not me, then probably someone near you...

Likewise ... since you declined to state where you're from, if you're anywhere near the Seattle area I'd be happy to spend some time going through this stuff with you.

Although some of the responses appear to be less than helpful, I think everyone has your best interest at heart ... it's important to grasp the concepts behind residual nitrogen. This is best done in an interactive setting with someone who can explain the tables clearly and can walk you through a few scenarios. Knowing the right answer in one particular situation really won't help you understand how it all works.

... Bob (Grateful Diver)

 

[SteveAD]

One more voice to say that even the seemingly unhelpful voices are speaking with your best interests in mind. This forum is largely for divers to share ideas helpful to fine tune our skills, but even those of us (many) who are qualified to teach, would not try to do so online.

 

[Crazy Fingers]

d00d, just by a computer and let it figure it out

tables r 4 loosers

(I am feeling really silly today.)

 

[String]

Incidentally dont worry about "fresh" and "salt" for tables questions.

Given your depth gauge in reality reads pressure NOT absolute depth the tables are identical for both.

 

[Benny-c]

This is actually something so fundamental you really need to ask your instructor if you didn't "get it" yet. The internet is great for certain things, but actual scuba lessons covering the same stuff everyone learns for OW isn't one of them. Really, people aren't being unhelpful, you just really need to get this stuff one on one from a qualified instructor.

Hear Hear!!