This past Tuesday, I dove with Andrew and the new UTD MC90 mCCR.
Since its announcement to the world, it’s caused more than a few amusing posts on Internet forums. The comments ranged from interested, to wait and see, to let’s give the MC90 a chance, to WTF are these guys thinking.
Like any configuration, I assume that it has its plus and minuses. And for what it’s designed for, I bet it meets its needs. Since I don’t do deep expedition in remote locations, I’m not the best judge of success. However, there are a few aspects of the MC90 that I do appreciate:
Similar protocols to OC – I like the similarities of handling issues from OOG to rock bottom. I’m sure the consistency is nice for those who dive both rebreathers and OC, but I also like it for the ability to dive in mixed teams. I don’t want to miss a dive because I don’t have a rebreather.
Gas extension – Not unique to the MC90, but I’ve always been fascinated by the recycling aspects of rebreathers. Lower gas usage and lower costs (in the long run) are intriguing.
Variable P02 set points – Hadn’t thought about this till we spoke about rebreathers on the drive down to Monterey. Current models and decompression schedules are based on changes in pressure and the P02 of the gases breathed at specific depths. The ability to change P02 at any depth opens up a lot of possibilities for decompression diving.
How much weight
Proper weighting is achieved when a diver can hold a 10′ stop with no air in the BC and with 500 psi remaining in the tank. This insures that the diver can hold his last stop at the end of a dive, without the need of a buoyancy device.
Why overweighted in OW?
If the proper weighting is significantly
Effects of Overweighting
Carrying additional weight than necessary means that the diver needs to carry more air (buoyancy) was well.
When a diver ascends, this extra air expands and needs to be managed.
Let’s say that a diver is properly weighted and compensating for 2# of weight near the end of his dive at 100′. He ascends from 100′ to 33′ and now has 4# of lift in his wing, as the air in the BC expands from decreased pressure. In order to remain neutrally buoyant, the diver removes 2# of lift.
In the same scenario, let’s say that the same diver is over weighted by 4#s. At 100′, he is now compensating for 6#s of weight. When he ascends to 33′, the air in his BC expands to equal 12#s of lift. To remain neutrally buoyant, the diver must now remove 6#s of gas from the BC.
It’s definitely possible to manage the extra 4#s of gas. However, it requires more management and more diligence. For new divers, this extra 4#s of gas is additional work that is not necessary and only adds to make diving more difficult.
Requiring less weight the more I dive
As you gain experience, you shed add’l weight cause you improve your breath control, your body movement and buoyancy.
In addition, you’re be more effective in eliminating gas from your BC. Trapped gas or inefficient purging is one of the reasons that new divers need to carry more weight.
In September, we made a return trip to Maui. We dove off Lanai for three days with Capt. Steve Juarez at Dive Maui Hawaiian Rafting Adventures. This is our second trip with Steve, and we continued to have a great time – the boat and crew were fantastic. When you’re on a boat for >30′ you can’t discount a stable and fast boat, and their custom dive boat was much appreciated.
Hawaii isn’t lush with tropical fish, but Lanai offers very interesting topography.
Steve finds octopus on many of the dives.
For my tropical trips, I’ve been using the UTD Z Sidemount system. With the QC6 quickdisconnect, it’s easy to get in and out of the water. In the water, sidemount really shines.
On Tuesday we meet up with Tim from Hawaiian Paddle Sports at DT Fleming Beach, north of Lahaina in Maui. After introductions, clinic Tim instructs us on the basics of outrigger canoeing in Maui – from holding the paddle, to positioning the body to maximize the stroke, to paddling commands in Hawaiian.
Underway, we paddle to Honolua Bay. Tim guides the canoe so we hug the shoreline, protecting us from the wind. As we make our way, Tim discusses the flora and fauna of Maui, pointing out the seaweed that turtles eat that make their fat green as well as indigenous blue coral beneath us.
At Honolua Bay, Elissa notes some odd splashing across the bay, and Tim quickly spies a pod of spinner dolphins. The canoe double times as we dash forward, only to catch the dolphins depart. While it’s disappointing not to be able to swim with the dolphins, if we had arrived a few minutes later we wouldn’t have seen them at all. And even if we were in the water, it’s a strong possibility that we would have missed them. The odd splashing was a free diver trying to descend. When we approach, the free diver remarks at the large number of turtles in the water. Even though he was probably 20 feet away from the pod of dolphins, he had missed them. Most likely they swam behind his back.
After taking a leisurely tour of the bay, Tim anchors the canoe over sand near the northern wall of the bay. Before letting us in the water, Tim reviews key landmarks and discusses marine animal interaction (don’t touch) and their consequences.
Immediately after splashing, we’re greeted with turtles and numerous fish.Â Elissa and I meander along the reefs edge and after a few minutes we’re joined by Tim. He helpfully points out fish by name, and leads us to a turtle cleaning station.
At the reefs edge, in 60′ of water, I see a dark shadow gliding.Â I flutter kick in high gear and dive down to see a large manta ray. Fortunately, and remarkably, the manta turns around and heads back towards us.Â We instantly give chase, diving down to get a better look.Â At 60’+, he’s outside my freediving range, but within Tim’s reach.
The picture below is me (camera) at 50′, and Tim and the Manta at least 20′ below me.
And as if the manta turning around back towards us wasn’t enough, he turns again and swims to 30′ to the turtle cleaning station. At this point, we have a manta in the shallows with 7 turtles around us.
I freedive like a scuba diver… hmmm….
After a good number of dives, we swim towards the boat and Tim takes a picture of Elissa and I near a turtle sunbathing.
Back on the canoe, Tim takes us out of the bay and we point towards DT Fleming. The wind at our back helps with the paddle back, but good piloting is still required for us to not overshoot our target. Tim is enthusiastic about outrigger canoe and Hawaiian culture, giving us a much appreciated history lesson of the islands as we head back.
January 22, 2011 – It’s always great to be invited for a milestone dive and 100 is the first big one for all scuba divers. Traditionally, you’re supposed to dive naked. But I really think that’s a warm water tradition. In Monterey, there’s nothing like marking your 100th dive in low viz (5′), surgy conditions, and rough shore entry.
December 18, 2010 – Cynthia, Ben, Brian, and I meet up at Breakwater (San Carlos Beach) for a Grand Tour scooter run. While we had hoped for stellar winter conditions, we got the standard 10′ – 15′ viz. We were blessed with a few sea lions at Metridium Fields though. Usually they don’t hang around this long, but could be curious teenagers.
On a sunny Sunday morning, Kevin, Ted, and I gathered at Pt. Lobos to wrap up Kevin’s Hole in the Wall mapping project. Having worked through logistics with other dive teams on Friday and Saturday, we were batting clean-up – literally. We had a few stations to map, but we also had to pull all the survey lines at Lobos.
Kevin stressed that we shouldn’t be goal oriented, but we couldn’t help ourselves. In the 90 minute dive, we completed the survey and successfully retrieved all survey equipment.