DPV proficiency - how long before you are comfortable?

[_Ralph]

So with my drysuit it took about 50 dives before I felt ok and capable and until 100 dives before I really understood and could predict how my suit would behave in shallow and deep waters before I needed to react.

How long does it take for a DPV? I kick occasionally to keep an even keel - I feel like I am getting used to it but inflating my wing and drysuit on the run is still unpredictable unless I stop and make adjustments. Is it just time and practice?

First dive to get the mechanics down, a few more to get really comfy.

No issues with CCR, if you’re dialed in, you’ll feel it if you’re heavy or floaty..

A quick ’pause’ off the trigger will tell you, add/dump if required and you’re on your way (even better while on the trigger)



_R

 

[jon holcomb]

DPV's are a great advantage to any competent diver. Learning is simple, quick, exhilarating. Just don't trust they will always work, and attach a float bag for that occurrence if you work deep.
I purchased the first of two Farallon MK-6 units I've used for over 1,000 hours in 1978, and the second in 1984. Both had 90 lbs of thrust, both liked 60% power for a longer time of use, and needed lots of battery maintenance / charging, so I had two sets of 4 batteries, two/pack. The adjustable power knob was poorly situated, needed protection as bumping it ruined it. I added a glassed on shield, as the factory should have. I remember being so depressed when the first of these two scooters (torpedo's as we called them) 'quit' quite often when I wanted to go to work. Lots of returns on that 'lemon'.
I'd wait until it was repaired to go back to work. I'm a commercial diver, used the scooter for scouting as well as Abalone recovery deep when the fishery was still viable. Power is weight. If a unit doesn't have much weight it doesn't have much power. This unit weighted 90 lbs. w/ batteries. It would pull your face mask off if you turned sideways under full power. That was advertised as "3 knots", and it was a real number...unlike some I see advertised today on 18 lb scooters, etc.
I 'detuned' the last MK-6 to 24 volts, from 48 volts @top speed. This for slower 'understanding' of the bottom as I passed over it. Too fast and you can't process all you see.Last video's taken from that scooter (compass added, another 'missing' feature you want) is @ "Purple Sea urchin recovery w/ proto-type air lift" on you tube.
Lawyers and law suits probably destroyed the potential of any real DPV 'for sale' years ago, as well as many good dive equipment ideas. Build your own!
I'm now building a good air powered DPV for use w/ hooka, the system used by commercial divers. I have plenty of air, (60 cfm) for a small unit, and a low price to pay for a new air motor when this one goes away. 750-1500 RPM's is the ideal prop speed and the Korte nosel and prop of the last unit will be used on this motor.
DPV's are a great tool for easy access to deep or long trips. Air hoses and compasses are what make it practical for surveys. Survival requires a back up plan when it quits...and it will. Camera's are best tied to your head. What you see is then what you record. They can save your life, or take it, depending on your experience. Learn in shallow water.

 

[nickbutcher]

It took me couple of dives to get pretty comfortable with my Sierra. I had no formal instruction but did get some very good advice which kept me out of trouble.

Switching to a Piranha was horrible (for the first few minutes). Due to its almost complete lack of inertia, it is very skittish (compared with a longer, heavier DPV) and needs to be kept under control, which was tiring on the wrist to start with. I only use mine to pull my arse down the shotline and around wrecks. If I needed to ride the thing for a long time, I'd be more comfy with my Sierra or a Cuda.

Now, after a good few hundred DPV dives, it's all second nature. I use a scooter on almost every dive.

 

[DA Aquamaster]

There's a difference between open water DPV use and cave DPV use. The latter really should require formal instruction from a cave DPV instructor, now so much for the scooter's use but for the gas planning, other contingency planning, tow and gas share techniques, etc.

I'm also a very strong advocate of progressing in small steps when it comes to *cave DPV* use. I regard 100 cave dives after completing Cave or Full Cave to be the minimum before you take a Cave DPV course. If you want to make longer penetrations requiring stages to maintain adequate bailout, then you also need to be very comfortable carrying and managing (a) stage(s) before you decide to blast off and do it with a DPV. Mentoring can be useful before or even after a Cave DPV course to either get you up to speed, or get additional techniques or perspectives not covered in a class.

Even in open water a new DPV diver will benefit from some mentoring. It will speed the learning curve in terms of weight and trim for the scooter, setting up the tow cord (and going over various tow cord options, pros and cons). It'll also help the new scooter diver in terms of cleaning up his or her configuration to get the most out of the scooter, as drag matters and has a significant impact on maximum speed and range. Switching to a DPV can also trigger some configuration changes, such as moving the light from the right hand to the left and that's an area where mentoring can be useful. It's also useful to get some insight on programming electronic speed controls on scooters where that is an option, so a mentor with experience on that particular model can be very helpful.

Finally, not all scooters are created equal. Trim and buoyancy have a big impact on ease of use, especially in a cave environment. Size can also make a difference. I've encountered some smaller scooters that were not well designed in terms of controlling torque. Even tow cord orientation (3 and 9 o'clock versus 6 and 12 o'clock) can make a difference in how some scooters handle.

Personally, unless I'm selling one to someone with prior DPV experience, I like to get in the water with them on their first dive to make sure they get off to a solid start with a minimum of bad habits.

 

[DA Aquamaster]

My P1 trigger is quite nice, but it is possible to catch the tow rope in it if you aren't paying attention. I went for quite the spin on my second dive with my P1 as a result. :-D

Now I always lock off the trigger if we're going to swim a bit, or if I'm going to spend some time with the camera while stopped.

Locking the trigger is a good idea. When the lock is properly positioned it's only three quick spins with the finger tip - maybe 1.5 turns total - between locked and unlocked.

However, I also added a piece of tubing to my tow cord to prevent the line from wrapping over the trigger.

The knot in the cord holds the tubing snug against the handle and prevents the cord from wrapping around the handle or trigger.

 

[DA Aquamaster]

As some others have noted, you need to keep track of your buoyancy when operating a DPV. Under power, the DPV can be incorrectly used as a crutch, using a vertical thrust vector to offset negative or positive buoyancy. There are two issues with that.

Most obvious is the immediate "change" in buoyancy when you let off the trigger. That can put you on the bottom or float you toward the surface. Ideally, you'll learn to anticipate the change in buoyancy with depth changes while you are on the trigger, so that when you stop you are very close to neutral. You can learn learn that by getting off the trigger briefly after a depth change to see how accurately you anticipated and adjusted for the change in buoyancy.

Less obvious is the effect maintaining that vertical thrust vector has on overall performance. If you are having to offset 5 pounds of negative buoyancy with thrust from the scooter, that's 5 pounds less thrust that is being used for forward thrust. That's costs you speed and efficiency.

In a cave environment that downward vector also potentially disturbs the cave floor, so you're not just hitting bottom when you get off the trigger, you are silt bombing the entire cave passage if the passage isn't quite large.

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Adding a dry suit and a CCR to the mix increases the number of volumes to manage, but it's not hard provided you learned to manage your CCR at minimum loop volume as it then becomes very intuitive and easy to manage that volume. Similarly, if you learned to manage your dry suit at minimum volume (enough to keep the squeeze off, or alternatively in cold water enough to fully but not excessively loft the undergarment) then it's not hard to manage those volumes either.

If you didn't learn to manage your loop and suit volumes that way, you're going to have a bit steeper learning curve with a DPV.