Report and video on this weeks tech dive to the RBJ

[down4fun]

The RBJ is actually two wrecks that sit on top of each other forming a X, sitting in 260 feet of water. Due to depth and location viz is usually 40 feet or so and current is often strong. We were treated to and outstanding day of diving on her with blue water from top to bottom and little current on the wreck itself.
The team was Jeff Addis on a rEvo, Adrian Soler on a optima, Tony Land on a rEvo, and myself on a rEvo. The plan was 30 minutes of bottom time starting with a swim thru at 260 where the two wrecks cross, as Tony want to shoot video of this part of the wreck. We would then make our way up to the deck for the remaining 20 minutes. As we motored out to the site the seas were 2-4, and once we got there the captain informed us we had 1.8 knots of current so the decision to hot drop to the wreck was made.
Two of stood on the back platform with the other two ready to go and the captain set us up for a perfect drop. We landed right on the bow 3 minutes later. After a moment the get ourselves straightened out, everyone gave the ok and we were off to the swim thru. Conditions were so good that we hated to leave at thirty minutes, but had too. The team of four blew two bags and began our 90 minutes of decompression.
A little about the plan. It was my idea to do this dive this weekend. The other members of the team have dove it several or more times, as for myself the only times i have been there was during class, so I have been wanting to get back there in a non-class situation.
The four of us exchanged emails about run time and gases and came up with a plan. 10 minutes at the bottom for the swim thru and then up to the deck for the rest of the time. We all had 10/50 for diluent. The ccr run time was 120. As for bailout, this was definitely a team bailout situation. We each had a al80 of deep mix of 18/45 or 15/55 and then an al80 of 50%. To encourage my teammates to do the dive, I volunteered to carry the O2 as a third bottle. Besides it's good experience for me. Bailout run time was 144 minutes with two gases and a little less with the O2. We each had two computers each and I know i also had hand cut tables taped to my puter. And of course all the standard gear we take on a tech dive, spare masks, two bags and reels per person, wetnotes, multiple cutting tools (you'll notice lots of line on this wreck), etc.

Hope you enjoy the video!

YouTube - Hot dropping the RBJ

ps john feel free to embed the video

 

[Rhone Man]

Great video - outstanding water clarity!

 

[Cave Diver]

Looks like an awesome dive Kim! Thanks for sharing!

 

[Slamfire]

That's Oliver and Avid Diver! I was on that boat doing the Hydro Atlantic on May 8th. Very enjoyable diving. When did you guys do this trip? I think I met Tony on another dive I did on Avid Diver back in December 2009. We did the Clinton that time. Deepstops AKA Brian P. introduced me to Avid Diver on that occasion. HowardE was also on that Clinton dive. I don't get to Florida all that often, but when I did again this last May, I managed to squeeze in another dive with Brian and Oliver. Thanks for sharing, Kim. It's a pretty cool video.

 

[down4fun]

That's Oliver and Avid Diver! I was on that boat doing the Hydro Atlantic on May 8th. Very enjoyable diving. When did you guys do this trip? I think I met Tony on another dive I did on Avid Diver back in December 2009. We did the Clinton that time. Deepstops AKA Brian P. introduced me to Avid Diver on that occasion. HowardE was also on that Clinton dive. I don't get to Florida all that often, but when I did again this last May, I managed to squeeze in another dive with Brian and Oliver. Thanks for sharing, Kim. It's a pretty cool video.

May 15th we did this dive. If that clinton dive is the one the day after christmas 2009, I was on it too. I had just gotten my rEvo. Oliver is definitely a favorite down here. GLad you got back down and to the Hydro...she never gets old.

 

[Slamfire]

It was indeed on Dec 26th. I had to go look at the RBJ video again to make memory. I do recognize the tattoos but I don't think you had a ponytail that day and I think you had sun glasses back then. I do remember you had a new rebreather and Howard having problems with something in his rebreather. I think it was only you, Tony and Howard on rebreathers and the rest of us where on doubles. I was the only one wearing a 2mm shorty (Brian was only wearing a skin). The Clinton was really fun too. I'm looking forward to more dives like these in the near future.

Question about the RBJ dive. At one point the video shows your Predator was reading 71 mins into the dive with 71 mins TTS. From what I heard in the video that corresponds with the bailout plan (141 mins), not with the regular runtime (114 mins). Is there a specific reason for this reading? My Predator does only OC because that's all I do. I know next to nothing about CCR's and how Predators work with them.

 

[down4fun]

Question about the RBJ dive. At one point the video shows your Predator was reading 71 mins into the dive with 71 mins TTS. From what I heard in the video that corresponds with the bailout plan (141 mins), not with the regular runtime (114 mins). Is there a specific reason for this reading? My Predator does only OC because that's all I do. I know next to nothing about CCR's and how Predators work with them.

That shot was tony's predator and a couple of things created the difference in the actual run time. The planned run time was taken from V planner which runs a different algorithm than the predator which is GF, so there they never match exactly. The next thing, and probably the biggest culprit here, is that the predator penalizes you for being deeper than the stop it is showing you should be at. When Tony is shooting video it's not uncommon for him to be below the actual stop depth in order to get those profile shots of the divers with the sun behind us. The predator starts adding time as he is doing this. The result was a run time 20 minutes longer than anticipated. The other divers actually cleared there deco and were out of the water by the time Tony's predator cleared. Luckily the water was warm that day so I didn't mind hanging out with him.

 

[Slamfire]

The next thing, and probably the biggest culprit here, is that the predator penalizes you for being deeper than the stop it is showing you should be at.

Tell me about it. I got 10 mins in the penalty box on the Hydro Atlantc dive. I only have about a dozen deco dives on the Predator since I got it fairly recently. Before that it was only cut Buhlmann GF tables for me. Before the dive Brian, Henry (don't know his last name) and I discussed the plan. Henry was going to do Ratio Deco, Brian was going to dive a VPlanner +2 conservatism, and I had run a 30/80 GF profile on the Predators planner. I read them my stops and gave them my overall runtime and we all agreed it was good.

Overall runtimes in all these 3 methods where just about 1 minute off from each other. What I did not take into account is that VPlanner starts the stops at 90' while GF was starting stops at 70'. I made the mistake of gravitating too close to my buddies during the stops actually staying below the stops the Predator was demanding from me. Also it doesn't help that my Predator reads between 3' to 6' deeper than other computers that use a salt water setting. By the end of the dive the Predator was demanding 10 more mins at 10 feet. Conditions where benign I had plenty of gas so Brian gave me the bag and I did 10 extra mins by myself.

In the beginning I thought it was because my Predator was reading deeper than Brian's or Henry's computers. I wrote Bruce, Lynn and Tyler from Shearwater. Lynn explained that, more than the depth reading discrepancies, the likely culprit was the use of different algorithms. I went back to analyze my profile with the intent to prove her wrong, but no, I was deeper than the stops the Predator was calling for. As buddies we had agreed that we were each going to follow different algorithms and I did not follow mine faithfully.

Still, I asked Shearwater to add a feature for manually setting up water density values (aka salinity). My other computer has two settings, Salt and Fresh. It has always read depth in a very agreeable way to the computers of all my other buddies. Tyler explained that the Predator uses a single fixed setting that places water density in between Salt and Fresh. My Predator always read between 3' to 6' deeper than my other computer. It's not such a big deal because the Predator will actually do live profile calculations based on pressure readings, not depth readings. But I am of the opinion that it could come as a problem during planning and executing because humans do these based on depth readings. I don't know if in a future Predators will have a manually adjustable water density setting, but it doesn't hurt to ask.