RDP wheel, a dying art?

[Scuba_Steve]

The students like it [wheel] and yes we show the advantages of using various dive computers but for $45 you extend your bottom time using the multilevel formula. And besides most college students don't have the extra cash to drop on new gear and computers.

Jim
Louisiana

This is yet another reason I forgot to mention, to use GUE's methodology. You don't require a computer (But yes, a bottom timer). Also, as The Kracken had mentioned, you're not going to need his calculator either. It's about as inexpensive and quick as you're apt to get, and that's a big plus in my cheque book. (Apologies for the Canadian spelling.)

It's worth checking out, Macgyver2258. Talk to MHK, (Michael Kane), or better yet, do a search.

Steve

 

[DA Aquamaster]

When I took my AOW in the spring of 1986, the Wheel was just being developed and was featured at DEMA that springe. At that time PADI was still using their version of the US Navy table and was also developing their newer RDP tables based on doppler ultrasound studies. The Wheel was an outgrowth of these tables but with more conservative limits for repetetive diving. The Wheel does allow planning in 5' increments but actually has some additional rounding built in in recognition of the fact that multilevel profiles are more likely be dove much closer to the limits.

In the same way, every dive with a dive compter to the NDL is in effect a square profile. This is the major reason that computers tend to have much more conservsative limits than tables. The yellow zone found on many computers also offers a means for the diver to add some conservatism. With computers or multi-level tables, you have more conservative limits if diving to a constant depth, but the advantages of getting credit for time spend shallower than the max depth on multi-level dives makes up for this and allows more bottom time on those dives.

I don't buy the argument that PADI's cost would go up if they used the wheel in their OW / AOW courses. It was developed in the mid 80's and has been around for nearly 20 years. PADI should have long since recovered their development costs selling them at $45 a pop and the additional cost of manufacturing the wheel compared to a conventional tables cannot be that great. It would cost PADI very little to use and supply them in their courses and it could be used to a major selling point for the course as it offers improved quality and the flexibilty of multilevel dives to OW and AOW divers who would not get that in competing agency courses.

The Wheel, like any other air table, can be used with nitrox as long as it is combined with an EAD conversion forumla or table. This can be an asset to a new nitrox diver who does not yet have a nitrox computer and wants to make multi-level nitrox dives.

But despite it's good points, the Wheel has perhaps seen it's day given the ready availability of inexpensive dive computers (both new and used) and dive software capable of being run on inexpensive PDA's. This is I think another reason for PADI to stop trying to use it as revenue source on it's own and incorporate it into OW classes.

You can pick up a new Palm 500 off e-bay for the price of a Wheel and then add Palm VPM for essentially free or buy a copy of DPlan for $60.00. Both programs offer a lot more utility and growth potential than a Wheel.

 

[Tommed]

would someone be so kind as to explain the GUE methodology referred to in several of the previous posts, or give some hints as to how to "mine" the Scubaboard for this info? My attempts at searches have turned up empty. Thanks

 

[Scuba_Steve]

would someone be so kind as to explain the GUE methodology referred to in several of the previous posts, or give some hints as to how to "mine" the Scubaboard for this info? My attempts at searches have turned up empty. Thanks

WOW I had to do some looking myself, and I even knew what I was looking for. I swear it wasn't that hard to find before.

Here's an piece of what MHK wrote a little over a year ago, when I first was exposed to it myself........

But given that this stuff isn't rocket science let me demonstrate how you calculate "on the fly" the 120 and 20%, it's pretty basic stuff...

120, based upon Navy tables, means that depth and time always add to 120. In other words an 80' dive means 40 minutes NDL, a 90' means 30 minutes NDL a 100' dive means 20 minutes NDL and so on.. So all one needs to do is take their depth and add to 120.. If they can't do that then they shouldn't be diving. 20% means that if you standardize you mix [ie; 32%] rather then go through the silly formulas that you spent all that money in your nitrox class to learn, all you need to know is that your EAD advantage is 20%.. So if you do a 100' dive your EAD is 80'.. So an 80' dive using the 120 rule means you have 40 minutes NDL.. This stuff is simple and doesn't require a degree in math and can be done in seconds "on the fly".. Those that tell you it's too complicated more then likely don't know it themselves or are trying to sell you a computer or a class.. Now if you wanted to be conservative you could use your max depth for the 120', but if you're turning your brain on underwater you can take 5 minute snap shots so for example if I did 10 minutes at 100' and 10 minutes at 80, I could simply average it as a 90' dive, therefore 120 - 90 equals 30 minutes NDL.. If you want to be more conservative use 115, the number doesn't matter to me, the idea is that it's simple and isn't impossible as many in the dive industry will tell you and it saves you $400 for your computer.. BTW, you can use that same money to take a DIR-F class because this is but one nugget of information we teach in the class ;-).. The shape is what is important, but mathematical models can only plot in depth and time...

Hope that helps..

I use a very similar formula. Infact I think I got it from the DIR dudes somewhere, but I can't locate it here. It's a rule of 130, with no 20% using EAN32. It works, and is basically the same thing as the 20% is roughly added to the 120 (Yeah yeah I know 20% of 120 is not 10...hehehehe), but it works just the same.

I had example to give you, of my own, but I didn't want to get my butt flamed, so I might just sit my example out for a while, but they do certainly expose the myth of tables vs. this model vs. that model vs. the other table.

If you realized how much "slop" was in this stuff (Recreational NDL's), you'd not be so worried about getting the exact number to stick on your NDL for a given depth and time. There is no magic number to find.

Maybe I will throw my 3-dive day example at you after all. Pulled out of my butt and not designed for any purpose or to drive a certain line of thought, but only to show the "slop".

Regards

Steve

 

[BigJetDriver]

I don't buy the argument that PADI's cost would go up if they used the wheel in their OW / AOW courses. It was developed in the mid 80's and has been around for nearly 20 years. PADI should have long since recovered their development costs selling them at $45 a pop...

You can pick up a new Palm 500 off e-bay for the price of a Wheel and then add Palm VPM for essentially free or buy a copy of DPlan for $60.00. Both programs offer a lot more utility and growth potential than a Wheel.

...especially since PADI used to force instructors to buy and teach the wheel...

...and your next point says it all...!!!

Cheers!

 

[Scuba_Steve]

...especially since PADI used to force instructors to buy and teach the wheel...
Cheers!

"Used to"??

I think they still do!

 

[FatCat]

Just a few remarks if I may,

First off, I see that most of you put quite a lot of faith in tables. Remember: tables are theory (well, to be fair they're statistics based on long-term trials based on theory). No-one can guarantee you won't get DCI if you dive your tables.

Also, remember that PADI tables are a lot more optimistic than US Navy tables.

I see a lot of talk about diving computers to the limit. Is this wise? Most divers I know sport impressive beer bellies, smoke and generally don't live a healthy life.

As for the wheel, this is a very funny piece of equipment. I'm especially amused by the way three different wheels tend to give you three different outcomes on complicated ML dives, even though all three are calibrated (the black dot in the circle, y'know).

What I do know about the wheel is that unless someone has a good grasp of decompression theory, they tend not to understand the way the wheel works. They just go through the motions and given an interval of say a couple of months, they don't remember how to use the wheel.

So I like to use the wheel as a teaching tool. Not to get divers to actually use it, but to get them interested in the principles on which tables are based.

As for using ordinary tables to calculate ML dives, I am sometimes awed by the creative thinking that has gone into the different ways of getting a result. What I don't know is if there has been any reliable testing of these methods. Has anyone actually sampled a population of divers over a certain period of time while using ML calculations on a flat table? It would be interesting to see such results if they exist.

 

[Mako Mark]

So I like to use the wheel as a teaching tool. Not to get divers to actually use it, but to get them interested in the principles on which tables are based.
.

The wheel was published in 1986-88, this was a long time ago when you think that was about when I upgraded my sinclair to a commodore 64.. It was way ahead of its time and has been a useful tool over the years.

Now, it will go the way of most dive tables in recreational diving, as a backup for when electronics fail. It may not go this year or even next year, but SDI has already been teaching an entry level divers course for there or four years that doesnt include table use. It will happen, PADI is just a little more conservative to change than some other agencies.

As for using ordinary tables to calculate ML dives, I am sometimes awed by the creative thinking that has gone into the different ways of getting a result. .

did we helter skelter the USN tables before the wheel came out? sure we did, that is why thy decided to create the wheel so the multi level capability could be included.

That quote by MHK is stunning. Steve, how does he calculate dives deeper than 120? I just have to have more info on this because although I have known for years about the 120 rule for figuring out the NDL, in my mind, it works for non repetitive no deco dives only, and I know MHK does the ocasional dive that does not fit that kind of profile....

(if you think it is more appropriate, start a "120 rule" thread in a different forum where it is less likely to get us into a bunfight)

 

[Charlie99]

As for using ordinary tables to calculate ML dives, I am sometimes awed by the creative thinking that has gone into the different ways of getting a result. What I don't know is if there has been any reliable testing of these methods. Has anyone actually sampled a population of divers over a certain period of time while using ML calculations on a flat table? It would be interesting to see such results if they exist.

There isn't any reason to sample a population of divers to find out if my version of a flat wheel works. I simply took a big hammer to the wheel and flattened it out . In case you haven't noticed, the pressure groups on the wheel and the RDP are indentical, and the SI times are the same +/-1 minutes or so. Both are merely ways to track N2 loading in the 60 minute compartment, while not exceeding the Spencer M-value limit in any other compartment. I have run a sufficient number of problems on both the wheel and my "flat wheel" to be confident that both give the same answers.

There are both circular slide rules and stick type slide rules. They both work on the same principle. The RDP and the wheel have the same sort of relationship. All that is needed to do full and proper multilevel planning using the RDP is to add the "ML" (multilevel NDL limits) to the RDP, and to use the same 5 special rules for multilevel diving that must be followed with the wheel. Everything else is already there on the RDP.

 

[Scuba_Steve]

That quote by MHK is stunning. Steve, how does he calculate dives deeper than 120? I just have to have more info on this because although I have known for years about the 120 rule for figuring out the NDL, in my mind, it works for non repetitive no deco dives only, and I know MHK does the ocasional dive that does not fit that kind of profile....

(if you think it is more appropriate, start a "120 rule" thread in a different forum where it is less likely to get us into a bunfight)

It's not stunning at all. As you've said, it's been around for decades.

We are speaking of recreational NDL diving, and not deco diving. I would hope that would have been obvious to everyone, but I guess it's worth noting, I hope like heck no one is going to run out and do this stuff on back to back to back 120ft + dives to the limits, on any gas of their choice! They'd be in for a world of hurt to be sure. They would also NOT be doing recreational diving either.

It will work on multi-level diving, and repetitive dives. I just didn't mention that part of the math in my previous post, nor will I.

I use a *******ized (I would assume) method of doing these, as it was put to me this way, by MHK I do believe. I was told..."Sit down, with the tables, run some profiles, and try to figure out the commonality in all this madness. Figure out a simple "rule" that will work across the board. It's right there in front of you."

So I did, and I did. I'm not saying it's what GUE teaches, because I don't know that part of their equation for sure, but I have found out what it probably is, because my method works, and it makes sense given what it seems to me, they've done with their NDL's and how the initial first dive (and multilevel dives) is worked out.

Fortunately, I will soon be seeing first hand (As I suggest everyone do) what GUE does teach on this topic. It will be interesting to see how "close" I come to their formula.

I really should give you the examples that I have using the RDP, Rule 120(Or 130 for EAN32) and V-planner. The differences in time would blow your mind. Which one is "more" right?

You'd readily see all this bunk a few here are worrying about is better spent doing just about anythign else. This model, that model, PADI tables, NAUI tables, USN Tables, Cobra, Vyper, Mosquito (Any other animal I failed to mention??) C'mon, it's recreational diving for pete's sake!

Seeing how easy GUE's "way" is, I'd never do it any other way. There's no need. It's simple and it works, it's also free to use, it gets you thinking more about your dive, and will no doubt give you an appreciation of GUE methodology. (That's supposed to be a good thing :] )

regards gents

Steve

P.S. Any questions? Please ask MHK.