RDP vs eRDPml vs Dive Computer

[rhwestfall]

I wish your instrutor was reading this. Your questions are legit, and demonstrate much to the fact that you should be refunded your money spent on your certification.... what did they teach?

all the advice given here is something you should take to heart..... I'd suggest going back to the books, read what is there, and ask your instructor. He obviously hasn't earned the money you spent...

 

[boulderjohn]

I looked at a computer at a local dive shop that's only about $265. Is there a reason to get a fancier computer?

In my controversial opinion, 90% of divers will be just fine with the computer you saw. Those who really need more features don't really need the features in the fancy computers you looked at--they probably need features found in computers that are probably not sold by your shop, most of which cost far less than $1,800.

 

[TSandM]

Right now, Leisurepro is selling a 3 gauge console, with an Aladin Tec2g computer, a Uwatec compass, and a pressure gauge, for $250. The Tec2g, although discontinued, is a very nice, Nitrox capable computer, and the logging software for it is the best I've encountered anywhere. You do have to buy an infrared dongle to download it, but they're avalable from Amazon for about $30. The Tec2g has a backlight function and is fairly readable in sunlit water, which I think is mostly where you are going to dive, right?

You have a very good point, that if the dives are shallow and short enough, decompression is not going to be the limiting factor. In fact, for many newer divers, no matter WHAT the profile, gas is going to end the dive before NDLs do. However, this becomes less true with multiple dive days -- residual nitrogen can make even a dive of very moderate depth reach no-deco limits. Generally, the dive ops will plan for this (I've had, for example, a dive op in Hawaii tell us to "expect" a 20 minute dive on the second site, because that would put most folks close to deco) but as has already been mentioned, it is really pretty dubious practice to depend on someone else to evaluate the parameters of your dive and make sure they are "safe". Read the Near Misses section . . . there are lots of stories of behavior on the part of dive ops and dive guides that will raise your eyebrows. I remember reading a cheery account of a dive op in Mexico that took clients, on single aluminum 80's, to almost 200 feet -- and bragged about it here, and spent significant time trying to defend why it was a safe dive.

Your own computer is a very small investment, when you look at what dive travel and dive boats cost, and it allows you to be in control of your own safety, and set your own limits. It also allows you to log dives very easily, with a great deal of information. Being able to look at your profiles can be quite educational.

You are right that both the RDP and the multi-level dive evaluation can tell you a dive your computer approved is not acceptable. The lesson from this is that dive computers, while allowing you more dive time than the tables, are also pushing you much closer to no-deco limits. This is why the practice of "riding the computer" (running down the no deco time and moving up just fast enough to keep it above zero) is a high risk activity.

 

[DiveNav]

Hi Matt,
to learn more about how multilevel dives affect your nitrogen loading, I suggest you play with our dive planner divePAL. The basic version is free and allows you to plan, analyze and log single multilevel dives.
You can use it to enter your own multilevel dive profiles, or import any of the thousands of public logs already in our database.
If you want to plan series of multilevel dives and/or change the conservatism level, then you can upgared to the full version ($2.99).
Both versions can be equipped with model specific dive computers so you can see them in action during simulated dives.

Lastly, if you are interested in purchasing a dive computer, I suggest you take a look at our research tool and the related how to choose a dive computer -free - class

Alberto (aka eDiver)

 

[lowviz]

..//....The dive computer permitted the dive, but gave no dive groups....//.....

It did, but it didn't show you the dive group. What you are allowed to do on your next dive is the whole idea of dive group, your computer will show what you can do if you go into "diveplan" mode. Note that this will change as your surface interval increases.

I hope the manufacturers are listening. What is needed is a really basic NDL recreational dive computer that cuts through all the visual clutter and just gives you what you need to know at the moment in full screen BIG LETTERS.

How about cycling through "Depth", "Time Remaining", and a "Check Your Gas" reminder? Throw in a "Safety Stop" suggestion at the proper time and call it done.

 

[TMHeimer]

RDP: Square profiles. Enter pressure groups in log. Good if you are on the bottom most of the time. Pointless if you are down 90 feet for 5 minutes and the rest at 50'. As conservative as it gets.
Computer: Gives you (theoretically, mathematically) your remaining bottom time. As pointed out, not advisable to push the limits. Can't enter PGs in log because it's a multi level dive. Tables have PGs.
eRDPml: Interesting device. There are a few pros at our shop who own and haven't used them. The depths and routines are known. If you know said wreck is at 90' and you plan 25 minutes, with a 2nd dive to 50' after a 90 min. SI, I guess it's not really necessary to re-calcuate anything on the eRDPml.

Depending on others to plan: Of course really a bad idea. I can see how problems can EASILY happen when doing multiple dives over multiple days. I've only done this once. I would imagine a case where an instructor just said "OK, time for the Deep Adventure dive of AOW, let's go" (without sitting down with the students to write out a dive plan) would be in a situation where there are only 4 dives over 2 days and all is known--a common occurrence up North. I've witnessed this while taking courses in both NS and in FL. Sometimes there was a brief verbal mention of depths and SIs.

 

[freewillie]

Wanting to stay with tables and wheels is like staying with rotary land line telephones. You like them as a student because that's what they teach you as part of the basics. The only reason is so that you have an understanding of what the computer is doing when you are diving. Try using your chart for even single dive with multiple depth levels and not necessarily making deepest dive first with each subsequent depth little higher going up. Try all different depths randomly.

The computer is like smart phones. Once you get used to them you can't imagine life without one. And you won't even care how tables work after that.

As for practicality, calculate at least $15/day x # days dived then you can see if cost of purchase is worth it for you. Keep in mind every computer is little different so each time you rent one you have to learn how to use it. Convenience factor alone is worth the money. I rented a computer once and assumed it was on water activation like every other time I rented from the LDS. Got under water to find it wasn't water activated and since I had started my dive would start under water. I had to call that dive. Went to different LDS and had them set the water activation before even left store. Got under water to find it was set for metric readings. Got meters and bar instead ft and psi.

After that went online and bought my own computer. Look not only for sales but open box demos and close outs. Got Aeris XR1 for $125 open box. Normally about $265 new. You can also ask LDS if they will sell you one out of their rentals.

 

[freewillie]

PS forgot to add hope you don't have to call a dive due to rental malfunction or that they didn't have one. How much better would it have been to spend even modest $ on basic computer than call a dive on a dive vacation?

 

[Quero]

I wish your instrutor was reading this. Your questions are legit, and demonstrate much to the fact that you should be refunded your money spent on your certification.... what did they teach? ...ask your instructor. He obviously hasn't earned the money you spent...

I think you're wrong here and doing an injustice to both Matt and his instructor. From what I've seen of Matt's previous posts, it's simply the case that he's well and truly hooked by diving, has a meticulous approach to his new hobby, and is open to input. His instructor, having demonstrated dive planning three different ways, seems to have done a fairly thorough job in laying the foundation for Matt's questions, which Matt poses here, looking for guidance. Matt correctly observes that many divers are rather cavalier in practice about dive planning but draws a faulty conclusion from this observation, the faultiness of which was pointed out to him and accepted by him.

For Matt: There's not much to add to the advice you've been given. But if you find the dive computer hard to read, get one with a big display. The Suunto Zoop has a pretty big face and is simple; I've got several of the big square Uwatecs that I love because of the large display. Of course there's a reason they call the Zoop a "hockey puck" design since there's nothing elegant about it, and wearing the Uwatec is like having a small brick strapped to your arm, but it is what it is. The stylish watch-type computers are harder to read.

 

[Ste Wart]

For Matt: There's not much to add to the advice you've been given. But if you find the dive computer hard to read, get one with a big display. The Suunto Zoop has a pretty big face and is simple; I've got several of the big square Uwatecs that I love because of the large display. Of course there's a reason they call the Zoop a "hockey puck" design since there's nothing elegant about it, and wearing the Uwatec is like having a small brick strapped to your arm, but it is what it is. The stylish watch-type computers are harder to read.

Quero has a good point about the watch-style computers. They are all smaller & harder to read, also they are roughly double the price of comparable "hockey puck" computers. For example my Suunto Vytec does exactly the same thing as the Sunnto Stinger (a bit dated now I realise).

And the thing is do you really want your dive computer on your arm for dinner parties? When I first started dating another instructor, she used to make me take my Suunto Mosquito off before we went out in the evening with the phrase "everyone knows you're a diver!". Which is true I guess.

More importantly you're walking around with an expensive piece of dive equipment strapped to your arm 24/7, so it's liable to encounter all manner of damage from daily use.

My Advice: Get a "hockey puck" computer, keep it safe, use it for diving!