Dolphin vs. Azimuth

[rayzjackson]

I wasn't using a drysuit as I was in water at about 20C in Lanzarote.

My scenario where I can't descend by simply emptying the BC is when doing a weight check at the end of the dive when the tank is fairly empty. So it isn't the case that I am then going to be significantly more positive later - I'm already at the "later". This does become troublesome when swimming shallow towards the end of a dive as there is no way to get less bouyant with breath control on the rebreather.

The bouyancy change with depth is primarily associated with a 5mm semi-dry suit - and here size certainly matters as I'm probably carrying something like 3 times the surface area of a small person! That means 3 times the change in bouyancy at depth. I think this is the root cause of my problem.

Also I don't believe the Nitrox in a 200bar 5litre tank weighs as much as 5kg, I was originally taught to allow 2kg for the air in a 12 litre tank.

I must disagree with your claim that fat is density neutral, any time I've been on a dive with a mixed bunch of people, the overweight ones have consistently carried more weight. Also just look at any cooking pot with the fats and oils on the surface!

I have no problems with bouyancy control with a typical rental BCD when on open circuit (although I think it may be fairly full by 30m) so I'm inclined to suspect the Dolphin has a rather limited lift capacity.

Also using the Dolphin I can maintain a clearance over uneven bottom contours and reefs with not too much difficulty so i don't think it's a fundamental lack of technique.

wazza - not sure why you say mouth-in-nose-out to descend is so bad? The bag is already full because I turn the air on before entry. I can't get any significant reduction in buoyancy by exhaling as it just puts the air back in the bag. However if I were to dump one breath the bag will still be partially empty and so will my lungs and I'll descend. The bag will then refill and if anything the demand valve may open and give me a richer mix.


Ray

 

[padiscubapro]

if you have that much of a buoyancy shift forget the semi-dry or wet suit, get a shell type dry suit. Your buoyancy with this type of suit changes very little with depth.. I am considerably lighter than I was in the past, even then I never used lots of weight with dry suits, 7mm farmer john wet suits required way to much so I got away from that along time ago...

I actually need less weight in my dui dry suit with full under garments than I need with a 3mm 1 piece wet suit! I use 2 layers of polartec undergarments in very cold water, 1 layer in your temp water, and no undergarments(just sweats) in warmer water where I will be doing extremely long dives.
If you decide to get a dry suit, get it fitted with a Pee-valve, it will add much needed relief especially on long dives.

If you are related to Hoover, a CCR will be a much better fit than an SCR,(You can find a used one, coupled with training that will be in the same range as a PROPERLY fitted Dolphin, not as sold from factory) and breathing the optimal mix at all depths will allow you to stay longer, and safer than you are currently doing, and much less chance of going hypoxic under high workloads at shallower depths..

You can do a long multi level dive, always staying beneath the MANDATORY deco stop threshold.. You will be warmer and much less dehydrated..

 

[rayzjackson]

padiscubapro once bubbled...
If you are related to Hoover, a CCR will be a much better fit than an SCR,(You can find a used one, coupled with training that will be in the same range as a PROPERLY fitted Dolphin, not as sold from factory) and breathing the optimal mix at all depths will allow you to stay longer, and safer than you are currently doing, and much less chance of going hypoxic under high workloads at shallower depths..

Rightly or wrongly, TDI et. al. (or at least their instructors) consider an SCR suitable for a diver of relatively little experience whereas the CCR courses tend to have a prerequisite of around 70 dives.

Having found the SCR so much of a benefit, I don't really want to carry out another 40-odd dives with open circuit until I meet the requirements for Inspiration training.

I guess I just have to go ahead with the SCR and if I find in a year or so that I want to go CCR, I'll have to try to sell the Dolphin second hand.

The fact is, I'm breathing heavy and cycling air at a high rate but probably not actually metabolising too much O2, so the SCR works fine for me in terms of increasing time to out-of-air dramatically. It may not be nearly as good as CCR but it beats O/C hands down.


Ray

 

[wazza]

After all Mr ray
What ever u r doing if u r taking a course in scr or ccr its good for u and for your experience in diving and its education don’t forget this, so have fun with the machine and I wish for u that u will be a ccr diver as well when u feel it’s the right time for u

 

[caveseeker7]

Ray,

if you already trained on and feel confortable with the Dolphin, you might as well go for it. The Azi is about the size and weight of the Inspiration, and prize wise between the two. For some good pics of the unit check out

http://www.nobubblediving.com/azimuth.main.htm

With either one you'll have to be carefull to watch you PO2 !!!
The mix you're breathing can vary widely if you exhaust yourself,
and Hypoxia is something you definitely want to avoid.

ALWAYS KNOW YOUR PO2 !!!

Even more so when you're overweight and out-of-shape. Rather than spending money on Azi training and the higher price of the unit, get the
Uwatec ZO2/Oxy2 combo and the Oxygauge. Redundancy (although readings may vary slightly due to different sensor locations). That way you will
ALWAYS know your PO2 ... you get the idea ...

Dive safe
Stefan

 

[undah20]

Question for you RB guys on this subject;

Can the Uwatec Oxy2 transmitter be fitted to both the Dolphin and the Azi? (I know it can on the Dolphin, but the Asi?) Though you said having the drager Oxy2 gauge for the Dolphin is good for your diving, and I agree, but only as a back-up, it's a very poor tool for use alone.

I would like the ability to use it on both, as I believe the Oxy2 light-years ahead. First it's mounted on the inhalation loop, so you are gaining your true inhalation 02% and PPO2. Second, it has dual sensors that continually monitor your breathing gas, warn of to high or low of PPO2, warn of exceeding depth limits based on those values and then they monitor each other as well to continually check to be sure they are working. It's ambient pressure/altitude adjustable and gives battery and sensor remaining life readings. (Obviously the Oxy 2/AirX-ZO2 should be used in combination.)

Has anyone tried the Oxy2 with use on any other Rebreathers?

 

[caveseeker7]

As you said, the OXY2 was developed with the Dolphin in mind.
With the AIR ZO2 it can be used with SCRs only, as the computer was not designed for use with CCRs (more details in a pdf file at http://www.therebreathersite.nl/downloads.htm)

As for OXY2 - Azimuth adapters, there are two I can think of:

Bob Howell builds one, check his page & contact info at
http://www.rebreather.org.uk/

Another I found on the site of Extend Air, but I don't know
if they're manufacurer or reseller.
http://www.extendair.com/

I'm not the bigest fan of the Oxygauge, but it's a pretty good back-up instrument. Better than entirely relying on the wireless transmission between ZO2 & OXY2.

 

[DIR Tec Diver]

Hello all.

I am a Dolphin Instructor, and I also dive with the Inspiration, and I am now getting the Halcyon RB80 very soon. Comparing these is like comparing a ferrari with volkswagen. The Dolphin is a great unit, and a lot of fun. Perfect for entry level re-breather training and getting experience. Yes, you will most likely want to get into CCR if you want to, but many are quite happy to stick with the Dolphin.

The Inspiration is also an excellent piece of equipment. Rated one of the safest units you can get. It has completely redundant computers on seperate power supplies, and lots of warning and danger signals, but you should not get involved with it unless you are already a very competent diver.

The Azimuth is a sexy maching, but for those who are ready to take more risk, and pay a lot more money too. It was originally designed for the Italian Navy, but did not succeed, and now is on the commercial market. Think about that. If you are not a seasoned re-breather diver, then stay away from it.

I chose to go with the Halcyon RB80 for my personal diving because lets face it - it holds all the world records, and the best divers in the world use it. There is no questioning that, it is fact. It is definitely NOT for anyone not very familiar with tec diving or re-breathers, so this is the golden crown to shoot for when you get at lease 200+ dives wit a re-breather.

If you are starting out, think smart and safe. The Dolphin is a perfect way to start out, and you can always sell it easily if you decide that you want to upgrade to the Inspiration or to a unit like the Azimuth or Halcyon

 

[King Kong Matt]

DIR Tec Diver once bubbled...
...and I also dive with the Inspiration...The Inspiration is also an excellent piece of equipment. Rated one of the safest units you can get.

Hold up just one sec. You PERSONALLY know GI3 AND you dive an Inspiration AND you think the Inspiration is one of the safest units you can get...

Riiiiiiiiiiiiiiiiiiiiiiiiiiight...it was so good...you had us going, and then you just pushed it a little too far.

 

[caveseeker7]

DIR TD, 'cause GI3 might personally rip your c-card to pieces. ;-0
Don't you know it's really bad style to say something good about the Inspiration AND sign it with anything DIR?