Is a computer actually necessary?

[cwinston]

So apparently I am showing off my newness to this sport with my previous posts, but I am rather confused now so please set me straight.

I just finshed a SDI OW course and throught the entire course I was instructed that to avoid over expansion injuries a maximum safe ascent rate was 30 fpm. Combined with the fact that the computers used in the class sounded alarms at 33 fpm also review of the manuals of the computer further reinforced this. So if the bubbles are floating at twice the maximum safe ascent rate how can you use this as an example.

As for using my ears for a guage, personally this is completely out of the question as during ascent my ears equalize so well I can't tell I'm going up, same thing for when I'm in a plane.

As far as using a bottom timer with an ascent rate, Personally I would assune this is an electronic device and as such I would concider it in the same catagory as a computer and prone to the same kind of failure issues.

I know I will probably take a lot of heat for this post, but please help clarify. Is the maximum safe ascent rate 60 fpm or 30fpm and if the popular concensus is 60 I would be interested in hearing your opinions as to why the computer is programmed with a rate that is colse to 50% of the acepted norm.

 

[Uncle Pug]

cwinston once bubbled...
I know I will probably take a lot of heat for this post, but please help clarify. Is the maximum safe ascent rate 60 fpm or 30fpm and if the popular concensus is 60 I would be interested in hearing your opinions as to why the computer is programmed with a rate that is colse to 50% of the acepted norm.

Excellent question.

The old standard rate of ascent used to be 60 fpm and divers followed a bubble the size of a pea (until it got too big and then they picked another one.)

That more folks didn't get hurt tells you something. However, it is better to ascend at 30 fpm and that is the accepted standard today... and pea sized bubbles more far faster than that.

But a much better way is to slow the ascent even more as you approach the surface... with the last 20' very slow and the last 10' even slower. I will sometimes take the last ten feet and 10 fpm.

Computers are of no help in this regard. To manage and ever slowing ascent you need the stuff.

 

[kwesler]

I fall into the "computers are not necessary, and not recommended until you don't need them" camp BUT...

Why use a fancy computer as a bottom timer UP? I know a lot of other divers do this also. Why not use a bottom timer? Is it due to the much smaller size of the computer? It doesn't log anything in guage mode, does it?

Ken

 

[kwesler]

I do not mean "fancy" as in any way a negative on those computers-I assume you guys are using the Suuntos, and they ARE fancy in the "whiz-bang" sense...

Ken

 

[Uncle Pug]

kwesler once bubbled...
Why use a fancy computer as a bottom timer UP?

Certainly not because it is smaller!!! With my old eyes smaller isn't better.

It is because in gauge mode I can turn the center section into a count up timer. Time for stops is important to me but also for timing my ascent rate. And yes, it does record the profile for download even in gauge mode.

Say... all of you who are interested in this stuff might want to read (and please respond with questions or comments too) a thread I have going on our local board. It is about how Tech diving tactics can be used in recreational diving. Tomorrow I am going to introduce the last installment:
computerless multilevel diving.
Click on the link and join the discussion.

 

[Northeastwrecks]

bertschb once bubbled...


Sheesh! Get over it folks. Nobody had to sell me on the idea of buying a computer. Just like digital cameras, cell phones, GPS receivers, etc - they sell themselves. I like gadgets. I like flexibility in my dive profiles. I don't like screwing with dive tables and I have the money. I bought a computer.

I dove for many years before the dive computer was invented and had a blast. I just MUCH prefer using one than not.

Do you use an abacus instead of a calculator?

Dive computer = optional but cool gadget

Like you, I love gadgets. But not for diving.

I find that I've got plenty of flexibility in my diving using custom cu tables. I'm cutting a new set for this weekend. Reasonably square profile on a low relief u-boat. I'll have everything I need on a set of wet notes, with a backup set in a different pocket.

Money has nothing to do with it. I used a computer until I bought the doubles, deco bottles, extra regs, safety gear, planning software, etc...

For me, its the fact that I like to plan my dives in advance. By reviewing the plan and committing to it with my buddy before the dive, we are able to plan contingencies, turn points, and bail out options.

I also find that my situational awareness is heightened during this type of dive. I'm more aware of where I am compared to where I should be on the dive than I am when I switch from gauge to computer modes.

There is at least one thread where a diver using a computer managed to kick into a serious unplanned deco obligation by following the computer's NDL timer. While I will admit that this may have been a case of user error, that is exceptionally unlikely to happen with a bottom timer and a custom cut table.

UP's remarks regarding the timer on the Stinger is one of the biggest reasons I use a computer instead of a watch. Plus, I enjoy the download feature. I print out my profiles and include them in my log. That's fun.

 

[Diver0001]

Uncle Pug once bubbled...

I don't just use a straight average to figure out my computerless multilevel dives.

I go slower and slower toward the surface the closer I get. You can do this with an infinitely variable ascent rate or with discreet stops of increasing duration.

This is what I do... well at least most of the time.

UP, a quick question. I've seen your method but I have a couple of questions.

Do you apply this same technique for minor deco dives? It's pretty clear that you can (at least on gut feeling) but I wonder if you have any experience with it in practice that you can share.

And what do you do with the portion of the dive between 2 and 3 ata? If you just follow the rule the way it's written you could get the impression that you could make a 60min (or maybe 70min) 60ft dive and surface directly because you didn't go over 3ata.

R..

 

[Bryan@Vintage Double Hose]

I buy every little item that goes with my computer, digital camera palm pilot, nextel phone etc etc. I waste countless hours figuring out all the ways that these devices make my life easier and more efficient! LOL ! I love messing with them.

When it comes to diving I am a minimalist!!! Dive computers are great but absolutely not necessary or mandatory.
Learn your table back to front!! When you are bored make up imaginary repetative dive scenarios. Check your work against the tables and do this over and over again. It's kinda like doing math on paper as opposed to a calculator.
IMHO.....Buy a dive computer when YOU feel that it would benefit your diving experience.

 

[GDI]

:doctor:
Computers allow you to make adjustments to your dive plan should you violate the original plan. (If you are not diving with a dive plan and just blindly follow the computer then IMO you are not a good diver and are a risk to yourself and others). The computer should be used in conjunction with dive tables. A good depth gauge, watch and spg may not be as acurate as a computer but will not necessarily put a good diver at risk who makes and follows a dive plan. An advantage of a computer is that it will provide you with current up to the minute easy to read status during your dive. You can multilevel just as easy with a depth gauge

Plan your dive and dive your plan

 

[Uncle Pug]

Diver0001 once bubbled...
And what do you do with the portion of the dive between 2 and 3 ata? If you just follow the rule the way it's written you could get the impression that you could make a 60min (or maybe 70min) 60ft dive and surface directly because you didn't go over 3ata.

I always do multilevel dives... even when diving off of a boat anchored in 60' of water. I don't ascend directly to the surface. Since every dive is really a deco dive... I add in deco stops... and for a 60' dive for 70 minutes we are not talking about anything more than a minute each at 30',20',10'... the same thing can be accomplished with an ever slowing ascent and taking the last 15' at 5fpm. But then I'm using nitrox on those dives. Best not do 70 minutes at 60' on air.

What I do isn't a *rule* to *follow*... it is a guidline that I use to deal with dives that have a deeper portion. The principle is to spend time shallow to make up for time spent deeper.