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SkItZo
07-14-2009, 15:59
Anyone use or familiar with the suunto cobra?? I'm looking at getting one and have been told that it is a very conservative AI computer and for the price It seems pretty nice.:smiley25:

Jack Hammer
07-14-2009, 16:39
Conservative isn't necessarily a bad thing. I've got a Suunto Gekko and a Dive Rite Nitek plus. There is very little difference between them until you rack up mandatory deco. On a 100'+ (planned for deco) dive my Gekko had ~10 minutes more deco time than the Nitek had, I played it safe. For recreational diving the Suunto's are fine.

I used the Gekko on a dive trip where I made 4-6 ocean dives daily for a week, each averaging 50mins to an hour, Only once did I incur deco, and that was because we had to swim deeper on the end of a dive to get a diver who had followed a wall down well below us.

Jack

Skred
07-14-2009, 19:09
I use a Cobra and have been quite happy with it overall but its conservative nature is the reason I will explore other options when I get ready to change. If the conservatism is a concern for you, this thread contains some pretty good information and links that you may find useful:

http://forum.scubatoys.com/computers-gauges/24919-what-some-more-liberal-computers.html

SkItZo
07-14-2009, 19:59
well being new to diving and this being my first computer I'm thinking conservative would be a good thing?!?!?!? Later I can afford to get more liberal as I gain experience.

gNats
07-15-2009, 08:24
I have a Suunto Cobra and love it. I am not a big fan of the electronic compass, so the Cobra 2 and 3 are not in my radar.

I love that it is air integrated and the digital readout is very easy to read even by flashlight in pitch dark poor viz conditions.

It is a conservative computer. I didn't realize HOW conservative until recently, when I started to expand my own diving skills. During a reecent dive, I learned something new about my computer and it's artificial intelligence.

(Disclaimer, I am AOW, was diving with persons with even greater experience and certification, and have a solid handle on my own skills).

After a nominal dive and several hour surface interval, my dive buddy and I chose to do a dive to about 130' in a quarry. At depth, my Cobra gave me 7 minutes of bottom time BEFORE deco. When my computer hit 1 minute before Deco, I notified my dive buddy. We looked at my air. I had not used my first 1/3. He continued to explore, which ate up my 1 minute and my computer began to notify me that I was in deco.

Within another minute or so, we started up the line at an appropriate ascent rate. As I began to ascend, my computer went from deco obligation to normal dive readings, increasing my bottom time reading. We reached a plateau at about 40 feet and swam around looking at artifacts as we continued to make our way to the entry point of the quarry.

At 18 feet my computer gave me the 3 minute safety stop countdown. I'm pretty sure I had a caution symbol on the face of the computer, which indicates that a longer surface interval is recommended.

That dive was 134' depth, 34 minutes, average depth 45'. I exited the water with over 1200 lbs of pressure.

My dive buddy and I had a serious discussion about why he chose not to head up at my one minute countdown. :smiley2:

When I showed him my computer, he checked my remaining air pressure and knew I would have enough air. He also realized that the computer would adjust itself as we ascended and any deco obligation would be nominal.

The following day (on our first dive), I did allow the computer to once again enter deco and once again, it adjusted itself and I did not have any penalty or obligations beyond the safety stop.

I did read the manual afterward and (how I understand it) because the computer is a multi-level dive computer (which I am sure they all are) it will continuously adjust based on depth.

To wrap this babblefest up, I'm sure if I had stayed at 134' for a greater period of time, the Cobra would have eventually penalized me and added time to my safety stop. However, I no longer feel I have to "dart" to the surface <grin> because my computer is barking at me that my 7 minutes of time allowed at a depth has expired. I now take my air availability and comfort in the water into consideration.

While I am not in anyway recommending that you disregard any dive computer, I don't think even the conservative Cobra is that conservative when you take into consideration the multi-dive computations.

It's a very affordable recreational diving computer from a very reputable company. And it has great functionality. I strongly recommend that you purchase the uplink pc cable to synch to your personal computer. It provides a great deal of information such as SAC rate (for the dive), your starting and ending pressure (along with the math to figure out averages), average depth, etc.

my 2 cents. I looked at a few computers, what really sold me on this one was ability to read in bad conditions and price.

Travelnsj
07-15-2009, 10:20
I've had a Cobra since they first came out about 8 or 9 years ago. Yep they are conservative and I have gone in Deco a few times (a couple were planned) which can be madding when other people have 5 minutes or so on different computers. Just keep an eye on you Deco time. But nothing wrong with being conservative safer diving!

thesmoothdome
07-15-2009, 11:12
Love mine. When diving Nitrox, I rarely run into NDLs. When doing multiple dives on air, I definitely noticed the conservative nature of the logarithm. A few extra minutes of stops don't necessarily bother me though. As others have said, more conservative isn't necessarily a bad thing.

Jack Hammer
07-15-2009, 14:32
well being new to diving and this being my first computer I'm thinking conservative would be a good thing?!?!?!? Later I can afford to get more liberal as I gain experience.
Conservative can be a good thing. Many computers have an option to make them more conservative, not as many have an option to make them more liberal.

Jack

Travelnsj
07-15-2009, 15:30
Love mine. When diving Nitrox, I rarely run into NDLs. When doing multiple dives on air, I definitely noticed the conservative nature of the logarithm. A few extra minutes of stops don't necessarily bother me though. As others have said, more conservative isn't necessarily a bad thing.

If I am diving 3 to 4 dives a day....I usually mix in a bottle or two of Nitrox...But that few extra minutes of stops for an Air Hog...unless it is planned...Not safe diving....I've learned my lesson!

ScubaToys Larry
07-15-2009, 15:40
When I was in Truuk, there was a guy on our trip with a Suunto that sat out several dives because of how conservative the computer was. If it had been Palau, he could just stay shallower on the wall, but if your target is a wreck on the bottom - not really anything to see 30 or 40 feet above the wreck.

I prefer the Aeris / Oceanic / DSAT / Padi Algorithms, and if I want to be more conservative, I'll just set the computer to beep if I get within 5 minutes of deco instead of at deco... But I want to make that choice - not have the computer make it for me.

thesmoothdome
07-16-2009, 11:09
When I was in Truuk, there was a guy on our trip with a Suunto that sat out several dives because of how conservative the computer was. If it had been Palau, he could just stay shallower on the wall, but if your target is a wreck on the bottom - not really anything to see 30 or 40 feet above the wreck.

I prefer the Aeris / Oceanic / DSAT / Padi Algorithms, and if I want to be more conservative, I'll just set the computer to beep if I get within 5 minutes of deco instead of at deco... But I want to make that choice - not have the computer make it for me.

How bad were the deco stops the logarithm was asking for? I've hit deco a few times on multiple dives in a day and haven't had any that couldn't be cleared by a hang tank. Was the computer locking him out for the next dive?

CompuDude
07-16-2009, 13:10
When I was in Truuk, there was a guy on our trip with a Suunto that sat out several dives because of how conservative the computer was. If it had been Palau, he could just stay shallower on the wall, but if your target is a wreck on the bottom - not really anything to see 30 or 40 feet above the wreck.

I prefer the Aeris / Oceanic / DSAT / Padi Algorithms, and if I want to be more conservative, I'll just set the computer to beep if I get within 5 minutes of deco instead of at deco... But I want to make that choice - not have the computer make it for me.

How bad were the deco stops the logarithm was asking for? I've hit deco a few times on multiple dives in a day and haven't had any that couldn't be cleared by a hang tank. Was the computer locking him out for the next dive?

In my experience, with Suunto, it really depends on the profile in question. You can go many dives with profiles that are not all that different from other divers with other computers, and be pretty close to in line with them, and then hit one dive that their algorithm just doesn't like and really get slammed.

wheelman
07-16-2009, 15:38
In my experience, with Suunto, it really depends on the profile in question. You can go many dives with profiles that are not all that different from other divers with other computers, and be pretty close to in line with them, and then hit one dive that their algorithm just doesn't like and really get slammed.

One of those being a sawtooth profile.

gee
07-16-2009, 17:38
I have used a Cobra for about 4 years and I'm very satisfied with it. I've learned to pay attention to the no deco time remaining & ascend slightly as it gets close to 0. My other dive computer experience is with a Suunto Vyper and I believe it is just as conservative, but that's ok by me. I just look at it as a safety margin.

bsktcase93
07-17-2009, 20:21
i have been using a suunto gekko for almost 5 years and havent run into any problems with it locking me out of dives and ive done multiple dives in a day at depth. it also depends how you set your diver profile

mitsuguy
07-17-2009, 22:00
Another divemaster/instructor and myself were leading some divers on two different dives the other day... dive 1 - max depth 70 feet, total dive time for me was 53 minutes, total time for her, 52 minutes... average depth was around 50 feet for both of us... out of the water for about 50 minutes, then a second dive... max depth here was about the same, and average depth was around 35 feet...

close to the end of the second dive, she asked me if my computer was ok, to which I shrugged and said yes... I asked why and she swam over... we had almost identical profiles, but according to her computer, she was required to do a 7 minute safety stop between 10 and 13 feet on her Suunto, however my Oceanic still gave me 40 more minutes of no-deco time at that depth, which was around 40 feet...

now, granted, I know that all profiles have slight differences, etc... however to be that different after a second dive is a little crazy to me...

navyhmc
07-18-2009, 00:36
Interesting mitsuguy. I know that the Suunto's are very conservative, but didn't think they were that conservative. I think I know someone who has one, may be a fun test to do on my next dives. Put both on an arm and do a few dives.

mitsuguy
07-18-2009, 03:20
Interesting mitsuguy. I know that the Suunto's are very conservative, but didn't think they were that conservative. I think I know someone who has one, may be a fun test to do on my next dives. Put both on an arm and do a few dives.


thats our next plan... we've got a Cressi Edy, Oceanic Geo, Oceanic Veo and a Suunto that we're going to try out over a couple dives and see what happens...

navyhmc
07-18-2009, 04:18
Cool!!! Have fun and let us know the results. No doubt you'll have a few dives in before I do.

chinacat46
07-18-2009, 08:04
I've used Suunto for years but mostly dive nitrox and have never had problems unless diving with air. Seems the added NDL that nitrox gives you is enough that the Suunto's perform fine. However as I said diving with air I have run into NDL's during the 3rd dive of the day. So if doing multiple dives I try to use Nitrox if not I will probably be limited unless I can dive someplace shallow.

Mtrewyn
07-18-2009, 19:33
I use a Cobra, and something to think about is that there are some settings that you can set to make it "very" tight, and unless you know your computer real well you would not know it was set that way.

One is a "personal" setting 3 steps 0 1 2, zero being loose 2 being very tight.

The other in an Altitude setting, and this more or less does the same thing, but works in addition to the other, they add together, so if you had one set and the other set you could end up with a "very" tight computer.

I am new enough that I never even "touch" the no deco time my "air" time runs out first. so it is fine for me, I'm going on a week long trip to Bonaire, and I'll really see there, but honestly I don't foresee any issue, but that is just me.

DMWiz
07-18-2009, 21:14
Another divemaster/instructor and myself were leading some divers on two different dives the other day... dive 1 - max depth 70 feet, total dive time for me was 53 minutes, total time for her, 52 minutes... average depth was around 50 feet for both of us... out of the water for about 50 minutes, then a second dive... max depth here was about the same, and average depth was around 35 feet...


On Suunto computers, not doing a 60 minute SI on a profile like that will kill your BT on subsequent dives every time. I have compared mine with others (mainly oceanic computers) and the minute the SI hits the 60 minute mark the allowable bottom times are closer.

navyhmc
07-18-2009, 21:36
Intweresting DMWiz..wonder what algorhythm they use?

DMWiz
07-18-2009, 21:48
Intweresting DMWiz..wonder what algorhythm they use?

RGBM and some of the newer models RGBM with deep stops.

Jack Hammer
07-19-2009, 06:03
Another divemaster/instructor and myself were leading some divers on two different dives the other day... dive 1 - max depth 70 feet, total dive time for me was 53 minutes, total time for her, 52 minutes... average depth was around 50 feet for both of us... out of the water for about 50 minutes, then a second dive... max depth here was about the same, and average depth was around 35 feet...


On Suunto computers, not doing a 60 minute SI on a profile like that will kill your BT on subsequent dives every time. I have compared mine with others (mainly oceanic computers) and the minute the SI hits the 60 minute mark the allowable bottom times are closer.
When I was on Roatan I believe all my dives had an hour or more SI. That could explain why doing up to 6 dives a day for a week never caused me any of the NDL issues others have reported.

Jack

rongoodman
07-19-2009, 10:09
Intweresting DMWiz..wonder what algorhythm they use?

RGBM and some of the newer models RGBM with deep stops.

They use the RGBM name, but almost certainly not the RGBM bubble model--there's not enough computing power there to do so. The algorithm is proprietary, but most discussions about it seem to come to the conclusion that it's some type of Buhlmann, with deep stops and some other modifications added.

navyhmc
07-19-2009, 18:33
Kind of what I was thinking goodman. I also thought that if it as others claimed to use the RGBM, the NDL vs. SI would be at least similar.

DMWiz
07-19-2009, 19:21
Intweresting DMWiz..wonder what algorhythm they use?

RGBM and some of the newer models RGBM with deep stops.

They use the RGBM name, but almost certainly not the RGBM bubble model--there's not enough computing power there to do so. The algorithm is proprietary, but most discussions about it seem to come to the conclusion that it's some type of Buhlmann, with deep stops and some other modifications added.

As I understand it, it is Suunto's implementation of RGBM. The way I read this is: Based in the RGBM with proprietary modifications by Suunto.

From the Suunto Cobra Manual:


6.2. REDUCED GRADIENT BUBBLE MODEL,
SUUNTO RGBM
The Suunto Reduced Gradient Bubble Model (RGBM) is a modern algorithm for
predicting both dissolved and free gas in the tissues and blood of divers. It was
developed in a co-operation between Suunto and Bruce R. Wienke BSc, MSc.
PhD. It is based on both laboratory experiments and diving data, including data
from DAN.
It is a significant advance on the classical Haldane models, which do not predict free
gas (microbubbles). The advantage of Suunto RGBM is additional safety through its
ability to adapt to a wide variety of situations. Suunto RGBM addresses a number
of diving circumstances outside the range of just dissolved gas models by:
• Monitoring continuous multiday diving
• Computing closely spaced repetitive diving
• Reacting to a dive deeper than the previous dive
• Adapting for rapid ascents which produce high micro-bubble (silentbubble)
build-up
• Incorporating consistency with real physical laws for gas kinetics.
SUUNTO RGBM ADAPTIVE DECOMPRESSION
The SUUNTO RGBM algorithm adapts its predictions of both the effects of microbubble
build-up and adverse dive profi les in the current dive series. It will also
change these calculations according to the personal adjustment you select.
The pattern and speed of decompression at the surface is adjusted according to
micro-bubble infl uence.
Also on repetitive dives adjustment may be applied to the maximum allowable
nitrogen overpressure in each theoretical tissue group.
Depending on circumstances Suunto RGBM will adapt the decompression
obligations by doing any or all of the following:
• Reducing no-decompression stop dive times
• Adding Mandatory Safety Stops
• Increasing decompression stop times
• Advising an extended surface interval (Diver Attention symbol).

rongoodman
07-20-2009, 05:31
There's a review of the new Suunto mixed gas computer over on Yorkshire Divers where this is discussed. One of the points the reviewer made was that the profiles generated are very similar to a modified Buhlmann model, and quite different from RGBM as produced by the GAP desktop program. Since the algorithm is proprietary, it's hard to know what they're doing.

navyhmc
07-20-2009, 05:57
in todays litigous society, it's is easy to understand their conservative approach, it cuts down on lawsuits.

mitsuguy
07-20-2009, 06:00
in todays litigous society, it's is easy to understand their conservative approach, it cuts down on lawsuits.


But at the same time, when is the last time you heard about someone getting bent using another computer within their no deco limits...

navyhmc
07-20-2009, 06:04
I have, a diver took a light hit: some sub-q emphysema and joint pain with dive 3: about 90' for 15, 2 hour SI, 60' for 30, 2:40 SI, last dive 50' 25 min. Symptoms came on about 40 min after the last dive. He had something like 15-20 min of NDL remaining.

mitsuguy
07-20-2009, 06:17
I have, a diver took a light hit: some sub-q emphysema and joint pain with dive 3: about 90' for 15, 2 hour SI, 60' for 30, 2:40 SI, last dive 50' 25 min. Symptoms came on about 40 min after the last dive. He had something like 15-20 min of NDL remaining.

Those dives could have been done using the PADI tables and still had dive time remaining... Accordng to PADI's tables, we actually would have had 48 minutes of no deco time remaining... Those were actually very conservative dives... Shows how crazy DCS can be...

navyhmc
07-20-2009, 06:54
I have, a diver took a light hit: some sub-q emphysema and joint pain with dive 3: about 90' for 15, 2 hour SI, 60' for 30, 2:40 SI, last dive 50' 25 min. Symptoms came on about 40 min after the last dive. He had something like 15-20 min of NDL remaining.

Those dives could have been done using the PADI tables and still had dive time remaining... Accordng to PADI's tables, we actually would have had 48 minutes of no deco time remaining... Those were actually very conservative dives... Shows how crazy DCS can be...

Totally agree. :smiley20: But still, he was on a computer alone... Granted the defense would most likely state what you just did, but still. It can and on occasion does happen.

CompuDude
07-20-2009, 16:23
Intweresting DMWiz..wonder what algorhythm they use?

RGBM and some of the newer models RGBM with deep stops.

They use the RGBM name, but almost certainly not the RGBM bubble model--there's not enough computing power there to do so. The algorithm is proprietary, but most discussions about it seem to come to the conclusion that it's some type of Buhlmann, with deep stops and some other modifications added.

They claim it's RGBM but from what I understand, the people who have really tried to figure it out have determined that it's actually Buhlmann with some proprietary tweaks to turn out numbers similar to RGBM.

DMWiz
07-20-2009, 17:08
I dunno, but if B.R. Wienke puts his name on it and says it's RGBM I'm leaning towards believing him.

I don't know how old this document (http://www.gap-software.com/staticfiles/RGBMOverview2004.pdf) is, but it's an interesting read IMO.

http://www.gap-software.com/staticfiles/RGBMOverview2004.pdf

The only project I know of that combines RGBM and Buhlmann ZHL is the Abyss Dive Planning Software (http://www.cisatlantic.com/trimix/abysmal/tech-articles.html)

CompuDude
07-20-2009, 17:19
I dunno, but if B.R. Wienke puts his name on it and says it's RGBM I'm leaning towards believing him.

Show me where he says this?

Although even if he does, there are people out there with serious issues about how he allowed what should have been public domain work to be locked up in corporate cabinets.

The Deco Stop - RGBM vs SUUNTO RGBM (http://www.thedecostop.com/forums/showthread.php?t=9560)

DMWiz
07-20-2009, 19:28
I dunno, but if B.R. Wienke puts his name on it and says it's RGBM I'm leaning towards believing him.

Show me where he says this?

Although even if he does, there are people out there with serious issues about how he allowed what should have been public domain work to be locked up in corporate cabinets.

The Deco Stop - RGBM vs SUUNTO RGBM (http://www.thedecostop.com/forums/showthread.php?t=9560)

Earlier on the thread I quoted from the Suunto manual and the document I linked in the previous posts discusses this as well.


SUUNTO RGBM
The Suunto Reduced Gradient Bubble Model (RGBM) is a modern algorithm for
predicting both dissolved and free gas in the tissues and blood of divers. It was developed in a co-operation between Suunto and Bruce R. Wienke BSc, MSc. PhD. It is based on both laboratory experiments and diving data, including data from DAN.

DMWiz
07-20-2009, 19:39
This post (http://www.thedecostop.com/forums/showpost.php?p=137261&postcount=24) from that thread you linked on TDS explains it in plain english:


There are two flavors of the RGBM model. The "full up" or iterative model is the one used by BRW to generate the NAUI Tables and is also available in GAP and the HS Explorer. The version that Mares and Suunto use is the "folded" version. The folded version is designed for recreational use and can be imbedded in any computer that uses an M-value algorithm.

The folded RGBM model parameters were calibrated and fitted to match the iterative model. Deep stops can be inserted imperially (which Suunto is now doing - maybe Mares as well, not sure). With this version you get a model that is easy to calculate, matches the iterative RGBM over the range it was calibrated for, and applies reduction factors to limit repetitive, reverse profile, and multiday diving.

Hope this helps clear some of this up.

Brian

CompuDude
07-20-2009, 20:26
Good stuff. Wish we knew more about how the "folded" version (whatever that means) came about.

debullenbulle
07-22-2009, 22:18
I love my cobra, just one thing, buy one with a quick release... It's easier to travel

KennyD
07-22-2009, 22:24
I have a Suunto Cobra and love it. I am not a big fan of the electronic compass, so the Cobra 2 and 3 are not in my radar.

I love that it is air integrated and the digital readout is very easy to read even by flashlight in pitch dark poor viz conditions.

It is a conservative computer. I didn't realize HOW conservative until recently, when I started to expand my own diving skills. During a reecent dive, I learned something new about my computer and it's artificial intelligence.

(Disclaimer, I am AOW, was diving with persons with even greater experience and certification, and have a solid handle on my own skills).

After a nominal dive and several hour surface interval, my dive buddy and I chose to do a dive to about 130' in a quarry. At depth, my Cobra gave me 7 minutes of bottom time BEFORE deco. When my computer hit 1 minute before Deco, I notified my dive buddy. We looked at my air. I had not used my first 1/3. He continued to explore, which ate up my 1 minute and my computer began to notify me that I was in deco.

Within another minute or so, we started up the line at an appropriate ascent rate. As I began to ascend, my computer went from deco obligation to normal dive readings, increasing my bottom time reading. We reached a plateau at about 40 feet and swam around looking at artifacts as we continued to make our way to the entry point of the quarry.

At 18 feet my computer gave me the 3 minute safety stop countdown. I'm pretty sure I had a caution symbol on the face of the computer, which indicates that a longer surface interval is recommended.

That dive was 134' depth, 34 minutes, average depth 45'. I exited the water with over 1200 lbs of pressure.

My dive buddy and I had a serious discussion about why he chose not to head up at my one minute countdown. :smiley2:

When I showed him my computer, he checked my remaining air pressure and knew I would have enough air. He also realized that the computer would adjust itself as we ascended and any deco obligation would be nominal.

The following day (on our first dive), I did allow the computer to once again enter deco and once again, it adjusted itself and I did not have any penalty or obligations beyond the safety stop.

I did read the manual afterward and (how I understand it) because the computer is a multi-level dive computer (which I am sure they all are) it will continuously adjust based on depth.

To wrap this babblefest up, I'm sure if I had stayed at 134' for a greater period of time, the Cobra would have eventually penalized me and added time to my safety stop. However, I no longer feel I have to "dart" to the surface <grin> because my computer is barking at me that my 7 minutes of time allowed at a depth has expired. I now take my air availability and comfort in the water into consideration.

While I am not in anyway recommending that you disregard any dive computer, I don't think even the conservative Cobra is that conservative when you take into consideration the multi-dive computations.

It's a very affordable recreational diving computer from a very reputable company. And it has great functionality. I strongly recommend that you purchase the uplink pc cable to synch to your personal computer. It provides a great deal of information such as SAC rate (for the dive), your starting and ending pressure (along with the math to figure out averages), average depth, etc.

my 2 cents. I looked at a few computers, what really sold me on this one was ability to read in bad conditions and price.

You did what?:smilie39: Followed my line? Where?:smilie39:

gNats
07-23-2009, 08:14
[quote=gNats;315127]
You did what?:smilie39: Followed my line? Where?:smilie39:

Hmmmm.... I don't remember seeing a line identified as the KennyD Line.

:smiley2:

Aussie
07-24-2009, 19:30
I love my cobra, just one thing, buy one with a quick release... It's easier to travel

Dont forget to always carry a few O-rings for the quick release as I have seen a few go.

Personally prefer a computer like Suunto Vyper which is the same computer as the Cobra without AI and a glass/brass SPG. If your lucky maybe buy another Vyper second hand and have as a backup. Really helpful in remote locations if one computer fails.

Regards Mark

SYOTABUCS
08-06-2009, 14:03
Another divemaster/instructor and myself were leading some divers on two different dives the other day... dive 1 - max depth 70 feet, total dive time for me was 53 minutes, total time for her, 52 minutes... average depth was around 50 feet for both of us... out of the water for about 50 minutes, then a second dive... max depth here was about the same, and average depth was around 35 feet...


On Suunto computers, not doing a 60 minute SI on a profile like that will kill your BT on subsequent dives every time. I have compared mine with others (mainly oceanic computers) and the minute the SI hits the 60 minute mark the allowable bottom times are closer.

I had noticed on our second dives our Sunnto Gekko seemed to be really cutting us short on bottom time. Maybe we were coming up just a little short of 60 min. on the SI. This is diving Cozumel and second dives can be 60-70 ft for a while. But we were having to come up (to avoid deco) 10 minutes ahead of most others, unless they came up due to air.

This has got me looking at the Oceanic Geo as an upgrade.

gNats
08-06-2009, 14:24
Another divemaster/instructor and myself were leading some divers on two different dives the other day... dive 1 - max depth 70 feet, total dive time for me was 53 minutes, total time for her, 52 minutes... average depth was around 50 feet for both of us... out of the water for about 50 minutes, then a second dive... max depth here was about the same, and average depth was around 35 feet...


On Suunto computers, not doing a 60 minute SI on a profile like that will kill your BT on subsequent dives every time. I have compared mine with others (mainly oceanic computers) and the minute the SI hits the 60 minute mark the allowable bottom times are closer.

This is really interesting news. I usually have a several hour SI, but lately I have been jumping back in quickly. I have a day of boat diving coming up this month. I can foresee less than a 60 min SI between the 2 dives within each set.

I'll be at a quarry this weekend. I think I will do a quarry test - 2 dives with a short SI on the first day and 2 dives with over 60 minutes and try to keep all dive profiles the same. See what the difference is.

DMWiz
08-06-2009, 14:37
Another divemaster/instructor and myself were leading some divers on two different dives the other day... dive 1 - max depth 70 feet, total dive time for me was 53 minutes, total time for her, 52 minutes... average depth was around 50 feet for both of us... out of the water for about 50 minutes, then a second dive... max depth here was about the same, and average depth was around 35 feet...


On Suunto computers, not doing a 60 minute SI on a profile like that will kill your BT on subsequent dives every time. I have compared mine with others (mainly oceanic computers) and the minute the SI hits the 60 minute mark the allowable bottom times are closer.

This is really interesting news. I usually have a several hour SI, but lately I have been jumping back in quickly. I have a day of boat diving coming up this month. I can foresee less than a 60 min SI between the 2 dives within each set.

I'll be at a quarry this weekend. I think I will do a quarry test - 2 dives with a short SI on the first day and 2 dives with over 60 minutes and try to keep all dive profiles the same. See what the difference is.

It's all depth and time dependent. I have done many dives sans SI (The time it takes to change tanks) in shallow waters and I'll be all good. As a matter of fact, if I take less than 5 minutes the computer will consider it the same dive.

But if you do a dive to max depth ~70' and total BT is say close to 60 minutes you bet the computer will want a 60 min SI. Anything short of that and your BT on the second dive will be dramatically reduced. So when you test yours out keep this in mind.

If you go to the dive plan menu on your computer after the 1st dive and plan a second dive to say 60 feet it will tell you what your allowable BT is even before you splash down. If you do this before and after the 60 min. SI mark you will see the difference.

gNats
08-06-2009, 15:13
[quote=gNats;320842][quote=DMWiz;315906][quote=mitsuguy;315782]

But if you do a dive to max depth ~70' and total BT is say close to 60 minutes you bet the computer will want a 60 min SI. Anything short of that and your BT on the second dive will be dramatically reduced. So when you test yours out keep this in mind.


If you go to the dive plan menu on your computer after the 1st dive and plan a second dive to say 60 feet it will tell you what your allowable BT is even before you splash down. If you do this before and after the 60 min. SI mark you will see the difference.

Let me double-check my understanding... I may be able to quantify this logically and report back my finding after this weekend.

Dive #1: My typical dive profile at this quarry is pretty much give or take the following details:

Max Depth: 56 ft (say 60')
Ave Depth: 35 -40 something
Duration: 35-40 minutes
Computer Allowed Bottom Time at 56': ???

The one piece of information I need to record would be the allowable time at 56' reading during the first dive. This number could be 40 minutes, 60 minutes, or 120 minutes. Whatever it is, I need to document that number.

During the Surface Interval, I can use the Dive Plan functionality on the computer to see the time difference in my next dive's total non-deco bottom allowed at 60'.

So, I can report back the total non-deco allowed time for a surface interval consisting of

30 min
45 min
60 min
75 min

And should see a noteable difference between the readings when the surface interval time passes the time I documented during the dive.

Clear as mud?

Do I understand the test properly?

Honestly, I've never used the Dive Plan functionality on my Cobra. So this will be interesting.

DMWiz
08-06-2009, 16:41
Yes basically you have it down. You won't see a marked difference in your allowable BT from 60 to 75 min SI, but you will between 45 and 60.

As a matter of fact you don't even have to dive the computer, you can do it all in the plan mode and see for yourself. The interface is clunky specially adding the SI time between dives.