PADI v NAUI Master Scuba Diver Rating

[boulderjohn]

. But while the lift bag calculations offer some interesting exercises, I could never understand their practical use. Over the years I've been involved in using both bags and barrels for moving heavy objects underwater ... a few years back I spent a whole winter building a small rock reef at one of our local sites ... and I've never once performed any calculations. In the real world, you just keep adding air until the object you want to move floats off the bottom. The real fun begins when you have to manage it as you change depths ...

I agree, and have explained the same thing to DM candidates. I think they were just stretching to find practical applications for students to demonstrate a knowledge of Archimedes' principle.

The actual training calls for the students to lift something from the bottom under control. That does take some skill, but in reality most people just send it up and stay out of the way. What is missing in the training is what a DM might actually have to do--take a weight DOWN while under control. That takes a heck of a lot more skill than bringing something up under control--adding just the right amount of air a little at a time without sending it back up to the surface is not easy.

Two weeks ago I took a very heavy weight for a permanent ascent/descent line from the shore, down a slope, and over a ledge at about 40 feet. It is similar to what DMs often have to do in our area as they take a heavy weight for a platform anchor out to the training location and sink it gently so as not to create a silt storm.

 

[shurite7]

. But while the lift bag calculations offer some interesting exercises, I could never understand their practical use. Over the years I've been involved in using both bags and barrels for moving heavy objects underwater ... and I've never once performed any calculations. In the real world, you just keep adding air until the object you want to move floats off the bottom. The real fun begins when you have to manage it as you change depths ...

... Bob (Grateful Diver)

I completely agree with you on this issue.

 

[wetb4igetinthewater]

I've both taken and taught the NAUI Master Diver class. It's a fine class ... in fact, I think it's the best class NAUI offers at the recreational level. But while the lift bag calculations offer some interesting exercises, I could never understand their practical use. Over the years I've been involved in using both bags and barrels for moving heavy objects underwater ... a few years back I spent a whole winter building a small rock reef at one of our local sites ... and I've never once performed any calculations. In the real world, you just keep adding air until the object you want to move floats off the bottom. The real fun begins when you have to manage it as you change depths ...

... Bob (Grateful Diver)

Bob,

You don't just do the calculations in your head, blast the air in until the donating cylinder drops in pressure by the calculated amount? Amateur ..... Kidding!

 

[MXGratefulDiver]

I built a sling with a cylinder strapped to it. When the cylinder gets down to around 500 psi, I replace it with a fresh cylinder and keep working ...

... Bob (Grateful Diver)

 

[MichaelMc]

What is missing in the training is what a DM might actually have to do--take a weight DOWN while under control.

To lower a weight, you can just suspend it from something on the surface, like a surface inner tube float, and effectively play out more and more line. An anchored surface float lets you hold a heavy weight belt 'object' and the down line in one hand and equalize with the other. Squeezing the down line lets you control or stop your descend. It worked well to return weight belts to the bottom for students to then lift. More advanced for an unanchored float might be put a pulley on the object or float and similarly control the feed by grip/release, but there is more concern with what the as yet unused line is doing in that scenario. Again no calculation beyond will you sink the float.

 

[BoltSnap]

I've both taken and taught the NAUI Master Diver class. It's a fine class ... in fact, I think it's the best class NAUI offers at the recreational level. But while the lift bag calculations offer some interesting exercises, I could never understand their practical use. Over the years I've been involved in using both bags and barrels for moving heavy objects underwater ... a few years back I spent a whole winter building a small rock reef at one of our local sites ... and I've never once performed any calculations. In the real world, you just keep adding air until the object you want to move floats off the bottom. The real fun begins when you have to manage it as you change depths ...

... Bob (Grateful Diver)

It is important/useful if you have to lift very big/heavy/sensitive items from the bottom.

 

[boulderjohn]

It is important/useful if you have to lift very big/heavy/sensitive items from the bottom.

Do you calculate the volume of air you need to lift that object before you do so? Do you know the weight and volume of the object beforehand, and do you then calculate how much air volume you will need to lift it before entering the water?

 

[Trailboss123]

For PADI all that is required for the Master Scuba Diver Program are five specialty certifications

It should be noted that whereas this statement is absolutely true, the prerequisites prior to obtaining this rating are the completion of Basic Open Water, Advanced Open Water and Rescue Diver certifications + the 5 specialties.

 

[BoltSnap]

Do you calculate the volume of air you need to lift that object before you do so? Do you know the weight and volume of the object beforehand, and do you then calculate how much air volume you will need to lift it before entering the water?

Yes to all of the above when it is something big, valuable and sensitive in addition to many other variables. I am talking about professional applications where there are safety, costs, liability, chance for financial losses and expensive damages, etc.

 

[TMHeimer]

My old take on the MSD debate is simple-the 2 agencies are different. With NAUI you get 8 dives minimum. With PADI, there could be a few more or less than 8. I recall my PADI MSD went like this:
NAV: 4 dives
Night: 3 I think
Deep:4
Wreck:4
Equpi. Specialist:0

==15 dives.
PADI Problem is any specialties count, not just the "core" ones if you will. With NAUI's MSD course being similar to PADI's DM one, you get a whole bunch of "why" knowledge. A certain small % of that is really practical for your diving, the rest is just nice to know.
In comparing the two DM courses, my educated guess is in the end you come out about the same, in that you get somewhat similar theory in both (though be it through the prerequisite MSD in NAUI's case). But, I do know that PADI eliminated some of the theory in DM course right around 2010 (I took the "old" course and there was a lot). This knowledge is now gotten in the PADI Instructor Course. How much of this that is missing from the new PADI DM course that is really relevant to actual DM work is questionable. The PADI DM course did add some practical stuff, which I thought was a good idea.