How major of NDL benefits?

[waterpirate]

Hi all,

Iwould indeed like to see some examples of ndl dives in the 150 and less range with the focus on 80 to 100 feet. This is the typical set of dives that I do and am on the fence as to wether I should double up for more bottom time with deco obligation, or save my back and get a ccr.
My knowledge of ccr in practice is none, understand the physics of constant po2, but do not have software to compare.
My back and the ability to kill, sorry I mean observe shy marine life is making me look into the ccr as an option.
How extensive is the maintanance really?
I could except a whole weekends diving and one bout of maintanance on Monday, is this realistic?

any advice would be welcome.
Eric

 

[Mr.X]

Hi all,

Iwould indeed like to see some examples of ndl dives in the 150 and less range with the focus on 80 to 100 feet. This is the typical set of dives that I do and am on the fence as to wether I should double up for more bottom time with deco obligation, or save my back and get a ccr.
My knowledge of ccr in practice is none, understand the physics of constant po2, but do not have software to compare.
My back and the ability to kill, sorry I mean observe shy marine life is making me look into the ccr as an option.
How extensive is the maintanance really?
I could except a whole weekends diving and one bout of maintanance on Monday, is this realistic?

any advice would be welcome.
Eric

Depends on your back, wallet and what you define as a whole weekend of diving. If you're doing a 2 day tech trip on a boat and don't want to lug a pallet with you a CCR might be your ticket. However, don't get fooled into thinking it's that light. With bailout, drysuit gas and a big CCR it can be a mother...but always less than a twinset of 98's, 104's etc - comparably equipped. Of course, you will have to break down your CCR before Monday to dry out the sensors and clean some of the loop.

X

 

[waterpirate]

Thanx X,
What would be the ndl for a 90fsw dive on ccr with a normal set point? Conservative is not my bag. Typicaly I can do a saw tooth profile while hunting with top of structure at 30fsw and repeated drops to 70 fsw with my hp 120 and get between 60 and 78 minutes before I time out on ndl using genesis computer.

I was also told that a ccr unit is comparable to wearing an al 80, including 20cu bailout.

I know these are specific questions that have a lot of variables, but before my wallet goes in motion, I am going to try and get them answered.

 

[Mr.X]

Thanx X,
What would be the ndl for a 90fsw dive on ccr with a normal set point? Conservative is not my bag. Typicaly I can do a saw tooth profile while hunting with top of structure at 30fsw and repeated drops to 70 fsw with my hp 120 and get between 60 and 78 minutes before I time out on ndl using genesis computer.

I was also told that a ccr unit is comparable to wearing an al 80, including 20cu bailout.

I know these are specific questions that have a lot of variables, but before my wallet goes in motion, I am going to try and get them answered.

You could get a similar profile using nitrox 36 OC compared to a constant po2 of 1.3 ish? on the CCR. If you bring deco 100% 02 you'd blow off some deco time on OC too. All together no big potatoes OC vs. CCR regardless of the constant po2 debate, or implied conservatism.

A Sport Kiss, Prism, or Evolution or that new Pelagian might be in that 80 cubic weight range? However, you still have to get yourself down as any of these things aren't all that negative. Strap on a Cis, Boris, or Meg with a heavy plate and now we're talking heavy. The Cis was somewhere in the 80 lb range +- and the Classic Insp 70 +- without weights in the trim pocket.

Again, I am probably not the best person to ask regarding CCR's as I am pretty tired of having to work on them (sending to factory) for dives which could be have easily been completed on OC. Again, I think they are the best tool for penetration and deep work + long weekends where trimix and a compressor are scarce. One thing for sure...they will have some electrical, or hardware issues somewhere along the way which will leave the user pissed off.

X

 

[waterpirate]

Thanx X,
I am trying to compile research and make an informed decision as to how to lighten my wallet. I am starting to believe that for my application doubles are the way to go with mixed gas and deco, rather than rebreather.

Eric

 

[Dr. Doug Ebersole]

I've been doing my recreational dives on a Sport Kiss for about 13 months with over 100 hours on the unit. The weight is 38 pounds and I've got 5 hours of bottom time with a standard setup. The no deco limit for a 60 foot dive is somewhere around two hours with a conservative setpoint of 1.2. I will usually put a 13 cu ft pony alongside so I have 27 cu ft of bailout gas (14 cu ft diluent) along with 14 cu ft of oxygen. The set up time is about 20-30 minutes start to finish. At the end of the weekend I break everything down and rinse it like I would my open circuit gear. I just put the mouthpiece, counterlungs, etc in a solution with a little disinfectant. I then let things dry out just like I would with open circuit. So maintenance hasn't been a problem.

Why do I like it for recreational diving in the 60-100 fsw range? Quiet, warm moist breathing gas, closer interaction with certain marine life, no changing over equipment despite a two tank morning and two tank afternoon trip, and I'm always the first one in and the last one out.

Doug

 

[Mr.X]

I've been doing my recreational dives on a Sport Kiss for about 13 months with over 100 hours on the unit. The weight is 38 pounds and I've got 5 hours of bottom time with a standard setup. The no deco limit for a 60 foot dive is somewhere around two hours with a conservative setpoint of 1.2. I will usually put a 13 cu ft pony alongside so I have 27 cu ft of bailout gas (14 cu ft diluent) along with 14 cu ft of oxygen. The set up time is about 20-30 minutes start to finish. At the end of the weekend I break everything down and rinse it like I would my open circuit gear. I just put the mouthpiece, counterlungs, etc in a solution with a little disinfectant. I then let things dry out just like I would with open circuit. So maintenance hasn't been a problem.

Why do I like it for recreational diving in the 60-100 fsw range? Quiet, warm moist breathing gas, closer interaction with certain marine life, no changing over equipment despite a two tank morning and two tank afternoon trip, and I'm always the first one in and the last one out.

Doug

Stainless, or Aluminum Case?
Weight inclusive of backplate, drive tanks and bailout?
How much weight to get down with the unit fully loaded on a drysuit, or 7mm?

Any problems with the handsets, or sensors to date?

X

 

[wedivebc]

or that new Pelagian might be in that 80 cubic weight range?

Have you actually seen a working pelagian? I think they are as rare as unicorns.

 

[Mr.X]

Have you actually seen a working pelagian? I think they are as rare as unicorns.

I'd love to see one. Too bad I am not in Thailand. Could use some authentic Pad Thai for lunch.

Going by photos and claims it seems to be a contender in the "light" category. From their site:

The weight of the unit with full standard scrubber, two full 2,7 liter, (19 cft), cylinders, but no BCD is 20 kg. The weight of the unit as you would travel with it, i.e without cylinders and with an empty scrubber, is 9,5 kg.

Regardless of stated dry weight, a RB requires weight to offset the buoyancy of the loop and other bits and pieces. So a PRISM, which is a remarkably light unit requires a #'s number of kg/lbs to get it under the surface. My Meg with bailout (40), drysuit bottle, can light + 6lb plate requires zero in the way of weight to get it under.

X

 

[bwh6]

Stainless, or Aluminum Case?
Weight inclusive of backplate, drive tanks and bailout?
How much weight to get down with the unit fully loaded on a drysuit, or 7mm?

Any problems with the handsets, or sensors to date?

X

I dive a sport kiss with drysuit in monterey. With stainless case and soft plate (Oxycheq Apac lite) I add 6 lbs of integrated weight. Total weight of the thing rigged and ready to dive with 13cuft tanks I've measured at 52 lbs, plus weight for bailout as appropriate (al19 up to 2x al40) and accessories (light, reel, etc). For reference, on OC my HP80 rigged and ready to dive (11 lbs integrated weight) is again about 50-52 lbs. This is with a CF200 and polartec undies, add more for thinsulate.

Bought the unit in April and have about 170 hours on it. After about 150 hours two of the displays bugged out. I don't really like the display design (have to open them up after every 20 hours to change the batteries, exposing a rather delicate PCB to the environment), and so I now have a shearwater computer hard-wired to the cells, no connector to fail (boo Fischer) and won't have to open it up to change the battery for another year or so. It's been rock solid so far, about 20 hours.

Brian