New DPV - Dive Xtras

[DA Aquamaster]

I was with @stuartv and another buddy Saturday, as Stuart said we were all new to scooters, we all purchased Blacktips and this was the first time we all had them in the water. @DA Aquamaster was aweseome enough to show up with his as well and give us some pointers, I feel like if he hadn't been there we would have all been second guessing our scooter purchases. The first few minutes were definitely humbling, but after a few adjustments to tow cord and a few changes to approach/technique it started to settle in and make sense.

At least 2 of the 4 of us had the DeWalt 12 Ah batteries, I had the Waitley 9 Ah batteries, I cannot remember for sure what the 4th person had. I found this to be very accurate:




My first dive was a roller coaster ride, 40 minutes of up and down the gears on the trigger, we were on the trigger almost the whole time, and I spent extended time at speeds 5 and 6, popping higher than that for brief moments. Had I stayed on speed 3 or 4 I feel like I would have had a lot more battery left. I didn't check what my batteries were at between dives, I wish I would have. On the next dive I spent about 10-15 min at speeds 3/4 steadily before I really started to lose power. The Blacktip was at 2 bars when I got back in the water for Dive 2, after maybe 5-8 min it dropped to one bar. You could really tell when it began to lose power, I was in gear 4 and my buddy right behind me was keeping pace at speeds 1 and 2. Eventually it died so I hitched a ride with my buddy, as we got back I tried it again and was able to get a little more juice out of it, just enough to get me back to the dock. I pulled the batteries when I got out, one said 17%, the other 18%. The two with me that had DeWalt 12 Ah batteries still had plenty of battery power. The 9.0 Ah Waitleys having roughly 60% the run time of the DeWalt 12 Ah seems very accuarate to me. My original plan was to purchase 2 sets of Waitley 9 Ah, now I am rethinking that. I feel like with the DeWalt 12 Ah on most dives I do I wouldn't have to carry a second set of batteries. So it was definitely good to run the batteries to the end and see the true extent.

I had never been on a scooter before, so I don't have a lot to compare to, but so far I am impressed with this one, especially at the runtimes I saw with the bigger batteries. I am nowhere close to setting foot in a cave, so this scooter right now is plenty for me. A few things I would like to be different:

-The damn trim issue. It's honestly not enough to second guess the scooter, it's just enough to annoy me having to reposition it every time I let off the trigger. If a longer or different tube would offset this that would be awesome.

-I'd like to have more control over the speed settings, delays, start speed, etc. From what I understand the Piranhas are fully programmable like this, though I could have misunderstood that. I don't even know if this is possible with the electronics inside the Blacktip, but I would be interested in that, even if it was an add-on module.

All in all though, I am impressed after comparing this scooter on paper to others and then getting it in the water. Would I be more impressed with a Piranha P2? For sure. But it's not in the budget, it's not what I need for the diving I do, so it was never considered. At this price point this scooter was low enough priced that I could justify it as making sense in my budget even if it only goes out with me sometimes. I really feel like there wasn't a scooter out there until now that fit into this category, which may be a huge market - those who want more than an older Mako but less than a full technical DPV.

I also had 9 Ah batteries installed. On the first dive, I had about 20 minutes on the trigger, mostly at speed 4 or 5, but with a brief burst at 8 while I followed Stuart who I suspect was going "Whoooo!". Dive 2 was almost entirely at speed 2 or 3 as we went all the way around the lake. I pulled the batteries when I got home and I had 57% and 58% respectively. So I had a plenty of run time left at speed three.

The reasons for that are probably three fold:

1) An awareness of battery capacity and asense for how much you've got and how fast you can afford to go. Larger batteries will let you go farther, or let you go faster, or both. With a smaller battery you have to pick one or the other.

That said, if you are splitting it up over two dives, and switch batteries between dives, you'll be able to run rings around a diver with a single set of 12 Ah batteries. It takes about 2 hours to recharge a set of 9 Ah batteries and about 2.5 hours to recharge 12 Ah batteries. With maybe 60 minutes of charge time in a typical 90 minute surface interval, even if the 12 Ah battery diver gets a partial recharge, you still have an edge or at worse are at no disadvantage with a pair of 9 Ah batteries. You can buy three sets of 9 AH Waitley batteries for the price of a single set of 12 Ah DeWalts.

Where 12 Ah batteries make sense is on a single dive where you need more range, or more speed over the entire dive.

2) The more you dive a DPV, the more efficient you will get. Dive Xtras speed and range numbers are conservative (unlike the often very optimistic numbers posted by other companies. That said, I can beat the posted Dive Xtras speeds in speed runs, due to a cleaner than average gear configuration and very good buoyancy and trim.

Less than perfect buoyancy takes a huge hit on efficiency. If your buoyancy isn't spot on, you end up having to divert some of the thrust with a vertical vector to offset the positive or negative buoyancy. New DPV divers won't do as good a job of estimating and correcting buoyancy changes with depth change (if they think about it at all) and won't notice the buoyancy issue until they stop and either cork or plummmet to the bottom.

Similarly, any excess drag in your configuration has a large effect on speed and range. Parasitic drag is a square function where going twice as fast adds four times the drag, so you'll see a much greater loss of efficiency at higher speeds.

Trim is also important. If you find yourself using your fins to hold your legs up, that's coming at the cost of increased drag. Similarly, if you can feel the prop wash on your stomach or legs, then you are down in the prop wash and you're losing a lot of efficiency as well.

It takes awhile to get good enough with a DPV to become efficient with the DPV and it's just part of the normal learning curve.

3) I'll pm you with this one, and we can take care of that next time you get down to NC.

 

[stuartv]

Probably easy for me to say at the 1atm of my stand up desk but if in confined space, wouldn't you just revert to muscle propulsion until cleared from the confined space?

That's what I ended up doing. But, I think that is harder when the scooter goes nose up as soon as you let off the trigger. And anyway, I don't really think that should be necessary. Restarting slower than you were going before doesn't sound like it has any legit downside. Restarting faster than you were going before just sounds like a bad idea in general. As @DA Aquamaster noted, if you were going at 1 when you stopped there might be a good reason for it. And with the way the BlackTip trigger works, where the timing of the button clicks is fairly specific, I can foresee having it restart at 3, the user trying to quickly get it down to speed 1, and ending up, for example, having the scooter think you double-clicked instead of single-clicking twice, so it goes to 4, instead of 1. I think I might have actually done that on Saturday. Extra disconcerting when I was in a confined space AND the scooter was pointing up towards the ceiling a bit.

I had a Piranha in the truck I would have happily let you demo.

I appreciate all that very much! Maybe if you're able to make the Morehead trip at the beginning of May...? As it was, I don't think I was ready to try a different scooter until after the 3rd dive that Aaron and I did. By the end of the third dive I was feeling MUCH more comfortable with it even than I was after the 2nd dive. Aaron and I took turns towing each other a fair ways on that third dive. I did some circles around the plane and a boat while towing Aaron. After we went back to individual operation it felt like everything was so much easier!

I think that is excellent input. If you're operating the DPV at less than the cruise speed of 3, there is usually a reason, and as you point out re-starting faster could be an issue.

I also agree the pause before the BlackTip starts could be a lot shorter.

On the other hand, putting the two "bugs" together, the overly long delay does allow you to shift it down from speed 3 to speed 2 or speed 1 before it actually starts. Conversely it also allows you to shift up 2 or 3 gears before it starts as well. I did a lot of that in speed testing where I wanted to start off the line in a specific gear, where those bugs together ended up being a useful feature, once I figured out how to use them to my advantage.

Yes! If I have it on 1, there is probably a reason. And, as I said above, if it starts in 3 and I need to get it back to 1 quickly, there's a fair chance I'll end up registering a double-click and going to 4 instead.

I get how the two "bugs" together could equate to a feature for what you are doing. But, for people who are not trying to do specific tests, so we don't care about starting off immediately in a specific gear, is there any other benefit that you see to the current length of the delay?

 

[AustinV]

2) The more you dive a DPV, the more efficient you will get. Dive Xtras speed and range numbers are conservative (unlike the often very optimistic numbers posted by other companies. That said, I can beat the posted Dive Xtras speeds in speed runs, due to a cleaner than average gear configuration and very good buoyancy and trim.

Less than perfect buoyancy takes a huge hit on efficiency. If your buoyancy isn't spot on, you end up having to divert some of the thrust with a vertical vector to offset the positive or negative buoyancy. New DPV divers won't do as good a job of estimating and correcting buoyancy changes with depth change (if they think about it at all) and won't notice the buoyancy issue until they stop and either cork or plummmet to the bottom.

Similarly, any excess drag in your configuration has a large effect on speed and range. Parasitic drag is a square function where going twice as fast adds four times the drag, so you'll see a much greater loss of efficiency at higher speeds.

Trim is also important. If you find yourself using your fins to hold your legs up, that's coming at the cost of increased drag. Similarly, if you can feel the prop wash on your stomach or legs, then you are down in the prop wash and you're losing a lot of efficiency as well.

The buoyancy changes do take some getting used to. I at one point had a depth change where I came up from 40ish feet to maybe 15 over maybe 3 minutes (going from memory) on the trigger the whole time without letting air out of my wing (or thinking to...). As soon as I let go of the trigger I started ascending quicker than I should have been...

 

[stuartv]

The buoyancy changes do take some getting used to. I at one point had a depth change where I came up from 40ish feet to maybe 15 over maybe 3 minutes (going from memory) on the trigger the whole time without letting air out of my wing (or thinking to...). As soon as I let go of the trigger I started ascending quicker than I should have been...

I was trying to work on that as well. And when I was towing Aaron around there was a point where we had gradually descended about 20 feet, following the line to the plane. Once down deeper, it felt like I was driving with my trim about 30 degrees head up because it felt like Aaron had not put any air in his wing on the descent and was now weighing me down at the back big time. LOL A fun learning curve.

I could see maybe trying not to scooter during an ascent at all, unless necessary. Ascend vertically as needed without being on the trigger. Get neutral at the target depth. THEN get on the trigger to go somewhere while holding depth, if needed.

Or maybe that approach is for rookies...

 

[macado]

I took my blacktip out for a ride yesterday. Good conditions for New England with 30ft of visibility and the water has warmed up to 41f (5c) degrees. I didn't go too far offshore, only about ~.6 nautical miles but still had plenty of juice left in my 9Ah batteries when I got back to shore

I decided to go solo and practice this social distancing thing that everyone has been talking about.
No coronavirus found, only some scallops.

 

[NothingClever]

Courtesy with a DPV is important. My full cave instructor commented once that Chris and Chrissy Rouse had blown the viz in a large portion of Ginnie using their DPVs. He made this comment in 2008, 16 years after they died, and it was still one of his most enduring memories of them. So keep that in mind when scootering not just in a cave or wreck, but also over any silt bottom where you might blow the viz. It's not a legacy you want to leave. In general, be sure that when you start, you don't have the prop pointing down at the bottom.

Great counsel.

I'm confident enough to jump in the water and just figure it out but old enough now (a euphemistic way to say "I've already screwed up enough stuff in life") to know that it pays to get some high quality training.

 

[stuartv]

I took my blacktip out for a ride yesterday. Good conditions for New England with 30ft of visibility and the water has warmed up to 41f (5c) degrees. I didn't go too far offshore, only about ~.6 nautical miles but still had plenty of juice left in my 9Ah batteries when I got back to shore

I decided to go solo and practice this social distancing thing that everyone has been talking about.
No coronavirus found, only some scallops.

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Man, that is like cheating! LOL

 

[DA Aquamaster]

The buoyancy changes do take some getting used to. I at one point had a depth change where I came up from 40ish feet to maybe 15 over maybe 3 minutes (going from memory) on the trigger the whole time without letting air out of my wing (or thinking to...). As soon as I let go of the trigger I started ascending quicker than I should have been...

I was trying to work on that as well. And when I was towing Aaron around there was a point where we had gradually descended about 20 feet, following the line to the plane. Once down deeper, it felt like I was driving with my trim about 30 degrees head up because it felt like Aaron had not put any air in his wing on the descent and was now weighing me down at the back big time. LOL A fun learning curve.

I could see maybe trying not to scooter during an ascent at all, unless necessary. Ascend vertically as needed without being on the trigger. Get neutral at the target depth. THEN get on the trigger to go somewhere while holding depth, if needed.

Or maybe that approach is for rookies...

It comes with practice. Over time you'll get good at estimating how much air you need to add to or remove from your wing and dry suit - and counterlung in the case of a CCR diver. You'll focus on the major depth changes first, then you'll also get good at recognizing and correcting for the slow changes in depth over time.

It helps a lot initially if you stop periodically and check to see how well you are adjusting buoyancy when on the trigger. With practice, you'll start to feel whether you are maintaining any significant vertical vector to correct for poor buoyancy.

Using a DPV does however highlight the need to manage loop volume, suit volume and wing volume proactively and in the right order.

 

[RayfromTX]

It is also a challenge when towing others to get them to do the same. I stop every few meters in depth change so they can re-establish neutral buoyancy. Then we continue. It gets smoother with experience. When ascending it is even more important. A danger exists when ascending and in case of a problem that needs to be resolved. My compadres were slow to react yesterday when I was towing both of them at 4 meters and one had an spg hose leak. We stopped to check it and they failed to immediately establish buoyancy before investigating the source of the bubbles. They caught it at 1.5 meters and came back down to me. There is a list of these things to learn and practice but it isn't a big deal and just a part of the learning progression.

 

[laikabear]

If the batteries (DeWalt) are not in the scooter and unused, can they discharge to the point where you can't get them recharged? Or is that just if you leave them in the scooter?

I have the batteries and charger but no scooter, and unsure when it will come. I guess they are backordered and that could mean anything at this point. I charged the batteries but I am wondering when I need to check / recharge them if they are just sitting in a drawer for 6 mos.