I was able to look at one of the prototypes of the new Nomad today. While there are some differences between the one I looked at and the final version, I was told about them and they are very minor. I do like most of the characteristics of the new wing. It has been designed to maintain a low profile without trapping air anywhere. The bungees run under the wing, not over it like most people do with the current Nomads. I’ve been running my bungees under my wing for a couple years now and am glad to see Dive Rite is finally doing the same. And they’ve figured out a way to keep the wing low profile. However, any repairs/replacements will likely have to be done by Dive Rite because of the way this rig is designed.

I don’t understand all the exhaust valves. But keep in mind that this rig is being marketed to the general public. If the general public thinks they want more exhaust valves, then that’s what they get. Apparently, there are enough people that wanted them. I don’t like the position of the top exhaust valve . They put it there to keep the back of the wing as flat as possible, and to help prevent water accumulation in the wing. I haven’t had much of an issue with my exhaust being on top of my current Nomad wing. However, I’d love to have a recessed exhaust, and I think it would be easy to design on. Simply drop the exhaust inside the wing with the threads on the inside rather than outside like they currently are, and place the threads of the cover on the outside so it can be threaded into the wing component rather than on it. Place some mesh over top to prevent debris from falling in and problems are resolved. As for the water issue, whoever is having issues with too much water in their wing simply needs to learn how to exhaust air appropriately by pulling the dump cord for a shorter period of time. I don’t think changing the location of the exhaust is going to fix this “issue”. When the exhaust is open and there’s no air coming out, water will go in. The issue with having the exhaust on the front of the wing is you can’t dump all the air from the wing from a horizontal position. To get the exhaust in the highest position on the wing, you’ll need to go vertical. I’ve experienced this in the Hollis wing, which has the exhaust on top but it folds over toward the front when in worn. I may experiment with making a recessed exhaust like I described and see if I can install one in my current Nomad.

The webbing on the new Nomad is a continuous piece, but, in my opinion, that does away with one of the things I really like about the original Nomad. The shoulder webbing now routes to the rear of the rig rather than being able to be routed straight down. This position places the webbing directly under where the valves/1st stages sit and, for those of us that store backup lights on our shoulder webbing, traps the lights under the valve/1st stages. I don’t have room in my pockets for the backup lights and I don’t want to point them up on the shoulder webbing.

For those of you that don’t like the shoulder pads, they are incorporated into the design of this new rig. Personally, they don’t bother me. The dump cord for the top exhaust is routed through a channel in the shoulder pads. Anyone wanting to remove the shoulder pads would have to modify that, but it doesn’t appear it would be much of a problem.

Finally, the rig is one piece. I like the modularity of my Nomad. If I need to replace the harness or the butt plate, I can. Not so with the new Nomad. However, I don’t see how they could have made it modular.

All in all, I really like the design of the wing, with the exception of all the exhausts (the bottom ones are not necessary for me) and the position of the top one. I could see this working for me with some modifications. However, before spending the money on one, I’ll have to work on the exhaust modification and see if I can make that work. If so, I may end up getting one of these eventually.

There’s a lot more to piloting a DPV than just, well, piloting it.  Many cave divers believe that it’s easy enough to do, buy a DPV, and start doing cave dives with it.  Fortunately, most are able to complete successful cave dives without any issues.  But what happens when there is an issue?  How do we prepare for those?

One of the easiest ways is to take a class.  For a small fee and 2 days of diving with a qualified, experienced instructor, a lot can be learned.  Now, some of you are probably thinking, of course I’m going to recommend taking a class.  After all, I’m an instructor.  Go back and re-read that I wrote “one of the easiest ways.”  You can also find a mentor who has a lot of experience on DPVs.  This could take longer.  And you’re also gambling on whether or not your mentor knows what’s important to teach.  But that can also be an issue with an instructor.  The difference is instructors have standards to follow.

I just recently assisted with a DPV class in which one of the students has been using a DPV for several years.  Much of that previous experience was also with a diver who had taken a Cave DPV course about a year earlier.  He came out of this class learning a lot and feeling like a better DPV pilot than he had been before the class, even with all that experience.

It’s not all about the skills of piloting the DPV during the dive.  It starts before the dive, before you ever take the DPV on a dive.  You need to rig the DPV up correctly and make sure it’s balanced properly.  An improperly rigged DPV and/or improperly balanced DPV will only create issues during the dive, especially if the DPV malfunctions and you have to tow it or swim it out.  Not only will it be more difficult to exit the cave, but it will also likely cause damage to the cave during the exit.  Improperly rigged and balanced DPVs are also harder to control while functional.  This is one of the most important parts of any DPV class and should be addressed before ever gearing up.

There are also emergency procedures that should be taught during a DPV class.  This experienced diver knew nothing about the palm bump.  If you’re wondering what that is, then maybe it’s time you scheduled a DPV class for yourself.  There’s plenty of evidence of the lack of knowledge in these areas, including a large scooter rut 3100′ back in a popular cave system.

How about sharing air while exiting on DPVs?  Have you ever thought of the logistics of doing that?  Or just gas management?  The rule of thirds is no longer applicable when a DPV is involved.  And counting on flow to get you out with a dead DPV is not acceptable.  How many of you plan proper gas management for DPV dives?

Just a few things to consider before taking a DPV into a cave.  There’s a lot more to the class than just the things I mentioned, at least to the class I teach.  Don’t think piloting a DPV into a cave is simple.  It’s not.  It’s something that takes a lot more planning and preparation than simply swimming in.

Respiratory Minute Volume (RMV) is the amount of air you breathe measured in cubic feet per minute. You’ll often hear someone saying their SAC rate is .6. That’s actually incorrect. Surface Air Consumption (SAC) is a measure of PSI per minute breathed. Someone might have, for instance, a SAC rate of 12psi/min. SAC is specific to the cylinder size it is determined on.

RMV, on the other hand, can be used with any cylinder, regardless of size since it is a measure of volume, not pressure. When determining RMV, you must know your cylinder’s rated pressure. Rated pressures are typically stamped around the top portion of the cylinder. However, aluminum 80s, for example, actually only hold 77.4 cubic feet of gas. For ease of reference, they have come to be called 80s. And low pressure steel cylinders are rated to 10% over the number stamped on the cylinder. You will see “2400″ stamped on LP cylinders, but they are actually rated to 2640 PSI.

Following are rated pressures for common cylinder sizes:

Aluminum Cylinders
80 – 3100
100 – 3300

Steel Cylinders
Low Pressure cylinders (LP) – 2640
High Pressure cylinders (HP) – 3442

Steel 72s – See numbers stamped on cylinder. Will vary dependent on when cylinder was manufactured.

Three different RMVs are typically calculated – Average, Resting, and Working. Average RMV is calculated by descending to a set depth (33 fsw or 34 ffw works best), noting starting pressure, swimming at a comfortable pace at the same depth for 5 minutes, and noting ending pressure. Enter the numbers into this form to calculate average RMV. Resting RMV is calculated by descending to a set depth (again 33 fsw or 34 ffw), noting starting pressure, hovering at that depth for 5 minutes, and noting ending pressure. In my courses, I actually have my students do this at 15 or 20 ffw during a 5 minute safety stop. Working RMV is calculated by descending to a set depth, finding an unmovable structure (a big rock works great), noting starting pressure, swimming as fast as you can while trying to move it for 2 minutes, and noting ending pressure. Once you have your 3 RMVs calculated, you can use them to safely plan your dives.

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This form is to be used to get an estimate of your gas consumption rate. It is only as accurate as the method used. Use the RMV calculated using this form at your own risk to plan your dives. Regardless of RMV and dive plan, all divers should monitor cylinder pressure regularly throughout the dive and begin ascent at a predetermined pressure as calculated during dive planning. In other words, if you get injured or die, it’s not my fault!