Ascending without a dive computer

[Schwob]

Disclaimer:
This is unecessary, and may not make sense to many, but it gives me odd additional peace of mind:

I have knots in my dsmb line on a reel every 10 feet (1 knot at 10', 2 at 20' etc. ), cause they.were free to put in when I checked if the line was actually tied to the reel. Just so if my computer fails completely and my spare if diving solo or my buddy's if buddy diving, or when I find myself completely dumbfounded for whatever unlikely reason, I could navigate verticallt by counting seconds and knots at any speed I wanted to, even in pitch black muddy dark. Do I or anybody need that? Unlikely. Do I mind having that? No, not at all, to the extent I even practiced from shallower depth. Why not...

My reel probably now has 80 or so feet on it only, 60 marked, but even if I had a lights and computers out incident (I don't see how) at 130' (and I won't be there by myself in muddy dark in the first place) I would take my chances by putting a puff n the dsmb and letting it go, when / if my ascent from 130' to 80' was a bit accelerated... (a smaller relative pressure differential than from 30 tp 0) I can then park there and go as slow as I want from there while reeling in.

 

[JackD342]

A couple of conversion errors here.18m does not approximate either 30ft or 100ft. Try 60ft. (59, actually)
PADI teaching is no faster than 60ft/min, or a foot per second. Many/most computers use half that rate, either for the full ascent, or for the shallower portion. So, about 1ft/2sec. Definitely go slower than your bubbles, but do not assume you can go as fast as your bubbles. They are probably heading up faster than 60ft/sec.

With practice you will usually be able to easily head up slower than either rate - with visual and/or tactile reference. But if you don't have those, you really need either a computer, or a watch + gauge. If you are diving tables and not just following a dive leaders plan, you need a watch in addition to the gauge anyway.

 

[Diver0001]

Hi guys

With sadly being only an occasional scuba diving the extent of my information equipment is only a Citizen Promaster Diver AY5000-05L, instrument console depth gauge and a PADI eRDP. As a result, without owning a dive computer, gauging a safe ascent rate of 18m/30ft per minute accurately is pretty hard without having some sort of visual indicator of depth other than the depth gauge on your instrument module/console. So with this in mind is the "never ascend faster than your smallest bubbles" adage a safe rule to live by? Swimming up with slightly negative buoyancy to better control your ascent rate is a safe method to use but a visual comparison by way of the bubbles is surely an immediate reference rather than trying to gauge the 18m/30ft per minute (equating to 1.5m/5s or 2.5ft/5s which is probably easier to estimate?) rate? Any thoughts, opinions, recommendations, etc, about this would be appreciated. Many thanks

2 things

1) the current best practice for ascent rates is 10m / min. All computers that I know of are set to that. 18m/min is just too fast

2) It's actually *very* easy to gauge a 10m/min ascent rate with just a depth gauge and a clock. How you do it is as follows. Starting at a given depth, look at your clock before you leave that depth. Then make your way to the depth 10m shallower at a rate that feels right and then look at the clock again. If 1 minute has not yet passed then remain at that depth until the 1 min point before ascending any further. If the 1 minute mark has passed then roll through the stop and ascend the next 10m. Doing this may allow for parts of the ascent to be faster or slower than 10m/min but over the whole ascent it will be right on the mark.

R..

 

[boulderjohn]

PADI teaching is no faster than 60ft/min, or a foot per second. Many/most computers use half that rate, either for the full ascent, or for the shallower portion.

1) the current best practice for ascent rates is 10m / min. All computers that I know of are set to that. 18m/min is just too fast

There is no contradiction here.

The PADI RDP was based upon the standard ascent rate when it was created--60 FPM. All their research was based on that ascent rate, and the table they created was based on that ascent rate. That means they cannot change that recommendation when you are using the tables, because the numbers on those tables would no longer be valid.

That is not what the computer version of their course says, though. There they tell divers to ascend at the rate called for by the computer algorithm they are using, which as Diver0001 says, is almost certainly going to be 30 FPM.

Your ascent rate depends upon the system you are using to control your dives.

 

[JackD342]

Yep, I should have include "with RDP" in my post. My bad.
I have actually been going out of my way lately to be sure my students understand the difference between the two methods, and don't pick and choose which rule they like. It is far too easy for that 60ft/min to stick in your head as a universal rule. More important is the time to fly after diving. With RDP after a single dive / single day it is 12 hours, multi dive multi day is 18 hours. But with a computer almost for sure it is 24. Don't use a computer to dive a profile series that wouldn't be allowed by the RDP, and then cut your time short based on the RDP rule. Usually that means no, you can't do that third dive, after lunch, on the day before you fly.

 

[Steve_C]

Of course he can dive without a computer using tables. It is just that if I were to run across him looking for a buddy on a dive boat I would not buddy with him. Using tables on the typical multilevel dives I do would cut my dive in half. No thanks. Since we ascend up a anchor line. Just go up a bit. Stop and look at some fishies. Go up a bit. Watch some more fishies. Repeat. Beats watching bubbles.

 

[Bob DBF]

Definitely go slower than your bubbles, but do not assume you can go as fast as your bubbles

Slower than the smallest bubbles, as it gets bigger find another small bubble. This done properly is approximately 60'/min. A depth gauge and watch is better but with a computer gone bad it's not likely you have either.

As @boulderjohn pointed out, PADI tables, and the Navy tables I used back in the day, use a 60'/min ascent rate, however the computers algorithm use 30'/min. This would mean that using the smallest bubble method would be ascending much faster than your computer would safely allow.

Personally I would not have an issue with 60'/min if my computer crashed unless I was close to NDL. In which case I would try to come up slower, hard enough for me with a computer, and hang at the safety stop longer, as judging water 10 to 20 feet deep is easier than an ascent rate.


Bob

 

[MaxBottomtime]

I made several hundred dives before I got my first dive computer. I've never been bent yet.

 

[boulderjohn]

I made several hundred dives before I got my first dive computer. I've never been bent yet.

There is no question that using tables is a very safe way to dive. People are writing as if simple safety were the only factor involved. If you want nothing but safety, stay in bed. I guarantee you will not get bent.

The reasons for using computers instead of tables involve things like the ability to do multi-level dives, adjust dive plans on the fly, etc.

 

[Chris Richardson]

Thanks for the input guys. I'm presuming, too, that the 3min @ 5m/16ft deco stop does completely purge the system of residual nitrogen so even if using the 'smallest bubble' ascent method you are still safe?