Diving without a computer?

[WillAbbott]

I bought a wrist mount bottom timer this weekend (I still want to get a wrist mount nitrox computer, but that's a different story)

What I would like to do, is start diving as IF I don't have a computer (which I do, because I have an air integrated computer and no SPG) So I'm wondering, how does one dive recreational like without using a computer? Do I plan a max depth and see what the NDL is, and then dive that plan, regardless? With many of the dives we do, it's possible to be either at 50-60 feet, or clear down to 70-80 on the same site, just due to tidal changes, or where on the wall you dive and see things.

I'm also thinking about possibly diving with the rule of thirds... I'm thinking with using an AL80 and the rule of thirds, I should have turn pressures which come closer to NDL limits... whearas running down to 1000psi before turning (our normal plan) I can easily go over the table limits, though the computer says I'm fine.

I do carry my tables with me on every dive now in my dive rite thight pocket. But curious as to what the recomended proceedure is... for refrence I have the PADI tables, the RDP, EAN 32, EAN 36, EAD, and o2 exposure, as well as a MOD table all together as my "tables" on each dive.

My best plan so far, is to plan a max depth, and then write on my wrist slate, the max depth and NDL, then a few depths above, so for an 80' dive, I will have the NDL info for 50-80 feet in 10 feet increments, so should we only make it to 50' I know I have more time... and of course switch to diving thirds.

My only major issue is how this will shorten the dives... I estimate at least a 10-15min shorter durration dive than normal, but then again that should still be very enjoyable dives.


Thanks for the input

 

[Uncle Pug]

TIP:
Try shorter posts with a single subject.

 

[WillAbbott]

TIP:
Try shorter posts with a single subject.

Fixed

 

[Uncle Pug]

First... Looking at your SPG every 5 minutes. Try to guess what it will read before you look. Don't mess yourself up by looking at it in 3 minutes and then 8 minutes and then 2 minutes. Every 5 minutes.

Second... plan your dive and dive your plan. <--- that is a period!

Third... your dive should be planned using the appropriate table (air/nitrox) as a square profile dive, that is max depth/time and stay within the NDL.

Fourth... if you have gas left (and you should plan your dive so that you have a third left) spend a minute or so at 30' and then move on up to 20' and spend a few minutes poking aroung there (you will be following the bottom so there should be stuff to see) and then move on up to 10 and spend as much time as you like (without draining your tank too low of course) and then make a very sloooow ascent from there to the surface.

Check you computer... I'll bet it is in the green.

 

[WillAbbott]

First... Looking at your SPG every 5 minutes. Try to guess what it will read before you look. Don't mess yourself up by looking at it in 3 minutes and then 8 minutes and then 2 minutes. Every 5 minutes.

Second... plan your dive and dive your plan. <--- that is a period!

Third... your dive should be planned using the appropriate table (air/nitrox) as a square profile dive, that is max depth/time and stay within the NDL.

Fourth... if you have gas left (and you should plan your dive so that you have a third left) spend a minute or so at 30' and then move on up to 20' and spend a few minutes poking aroung there (you will be following the bottom so there should be stuff to see) and then move on up to 10 and spend as much time as you like (without draining your tank too low of course) and then make a very sloooow ascent from there to the surface.

Check you computer... I'll bet it is in the green.

Up to the rescue once more

I'll give it a go.

Of course my computer is always in the green anyways, since we typically spend so little time at the actual max depth, and much more above it, as well as about 1/3 of the dive in the 20 foot range (typical procedure has been, at 1000 pounds we turn around to the exit point, and ascend to 20-30 feet to proceed to the exit, which typically turns into at least 10mins at 20feet)

I've never had it say I exceeded an NDL as I've never been at a max depth long enough.

Also, do you go with what PADI says (and I'm sure other agencies) as the Bottom time (counted against NDL) is from descent, while at depth, until ascending to the 30' mark? at 30, 20, and 10, the time no longer counts against your NDL? I'm assuming you do, as that's still pretty conservative, as one should be offgasing at that point.


So next dive I'll plan the dive, probably make the plan on my slate for at least 4 max depths, and then not exceed the absolute max, but should I only hit 50' with 80 max planned I have the NDL for 50 handy (without digging the tables out) I'll figure out my thirds as of starting pressure - 200psi (absoulte never touch pressure) at 1/3 turn the dive, at 2/3's be at 10' or at the surface.

Sound right?

 

[DennisS]

Fixed

"and PADI says I have to use a snorkel while teaching"

Are you an instructor?

 

[jplacson]

Well, the PADI way is to plan your dive, and dive your plan. This means no changes in your actual dive. AFAIK, DIR guys dive without a computer. I know they have a technique for computing NDL on-the-fly. Regardless of the profile, I know they can compute their NDL to within a minute of a computer (depends which computer you're comparing them to though) and can handle multi-levels dives on-the-fly as well.

I'm not really sure how they do it...I haven't taken my DIR-F class yet. But I know they always say that the best computer is the one between your ears. So I'm pretty eager to learn how they do it.