Shearwater for a newbie ?

[NAM001]

Did anyone who had a Predator buy a Petrel or Perdix ? I bet some did and that kind of supports what I am saying.

I did I have a predator a petrel 1 and a 2.m other than a minor hardware or 2 they all operate the same way. and the petrel 2 compass is really nice to use.

 

[NAM001]

The real advantage of the Shearwaters, in addition to the superb customer support, is the underlying philosophy. No lock outs, no annoying alarms, no proprietary software. The computer presents the information, the diver uses it. If and when better algorithms appear in the future, implementing them can be done with firmware updates.

you are 100% right and that is why I use them.

 

[Peter69_56]

I disagree. Let's say you are diving 50/80. Your first stop is where you get to GF50. Now you skip the stop, ascending to e.g. GF 70. The computer SHOULD keep you there until you are below the initial calculated GF line and then resume the ascent.
The other option of recalculating a GF line from 50-80 when you are at 70 would be impossible? I believe that it will increase your later stops if you skip early stops in order to get back below the line.

Whether that works out in practice due to suboptimal ascent rates etc is anyone's guess.

As tbone1004 said, the shearwater keeps on trying to help you. What do the other brands do in particular recreational ones, they give up and lock you out. To me thats a big winner to have a computer trying to help. So you are locked out with your X brand computer, what now? Ascend again with ?????? a guessed plan, another pc that doesnt know you already dived? or a shearwater thats still giving you resonable data based on your previous crap dive. I know what I prefer and have been in that exact situation. Came up early due to fouling a line and got pulled up, sorted it out and then went back down and finished my obligation, then some. Came up ok. With my Oceonic it would have been come to the surface, sort the problem, then go back down and guess, not an option I like.

I also agree that the calculation it uses is a known and open algorithm. What others use is hidden and who knows what the results will be, unpredictable. I base my opinions on what I have used and am impressed and happy with my Petrels. They have helped me out of the poo a number of times when things have gone pear shaped. I have not been bent to date so they are doing something right obviously.

 

[rongoodman]

@tbone1004 just like a petrel running out of numbers won't be a problem to its dead user. But personally I prefer knowing that when it "doesn't compute", my computer will just stop and ask for a cold reset. That's simple stupid and IME simple stupid works much more often than any alternative.

You're assuming the lock-outs programmed into recreational computers are due to them actually not being able to complete their calculations, as opposed to being there simply to shield the manufacturers from liability.

 

[tbone1004]

@rongoodman you are absolutely correct. @dmaziuk the computers that lock out are capable of finishing the obligations because they will let you finish the first dive. They lock out on the surface. They do that because the computer manufacturer thinks it is a safety feature and I call BS.

@KenGordon if you skip stops, it may definitely add time to the next stop. It may not be the same amount of time at depth, i.e. if you blow a 30ft stop on backgas and end up at 20ft on O2, it will likely be a shorter deco, but if you blow 20ft, it will give you the same amount of time at 10. Slow compartments are still slow and need to keep up. The leading compartments will be well under, but the slow ones need to play catch up.

 

[KenGordon]

Assume a simple dive on backgas. If there is astop at 12m for a given GF and I stop I will off gas according to the gradient at 12m. If instead I ascend to 6m do I off gas more slowly or more quickly? The gradient is bigger so the off gassing is faster. So my deco time will be less. A bit like GF 100/70 vs 50/70. You may surface at the same GF but which will be quicker?

The fastest stop is at the surface, the question is only whether it is safe to get to the surface.

The computer just does the numbers on the on and off gassing and then compares with the m-value limits. The shallower you are the quicker you off gas and so the quicker you can surface. If doesn't matter if you exceeded the limits on the way.

 

[KenGordon]

I have had a Zoop lock me out at 7m while it was set to air and I had done a 60m trimix dive with two deco gases. I was above the ceiling for long enough for it to get in a huff. But if it had been the only computer I had it would have got me to a place where I could just breath my deco gas down then surface.

 

[BoltSnap]

I have had a Zoop lock me out at 7m while it was set to air and I had done a 60m trimix dive with two deco gases. I was above the ceiling for long enough for it to get in a huff. But if it had been the only computer I had it would have got me to a place where I could just breath my deco gas down then surface.

But this computer wasn't meant to be used for this type of diving. It is wrong tool for the wrong job.

 

[KenGordon]

But this computer wasn't meant to be used for this type of diving. It is wrong tool for the wrong job.

I am pointing out you do not need to surface to upset a computer, as claimed in the previous post.

It is actually a fine computer to use in combination with a slate. It tells the time and depth. Given the failure of a primary computer that is all you need.

 

[Scared Silly]

For the OP, computers can last a very long time if cared for properly. My wife is using her 13 year old Suunto Cobra still. For 10 years it was her primary computer, now it is her back up as she now has a Perdix. I dove a Suunto Vytec for a decade before switching computers. So computers can last a long time. Both of these Suunto were used on trips to places like Truk Lagoon with many days of multiple deep dives.

One of the biggest issues with most puck computers is that they are black and white screens that can be hard to read. For instance, Suunto computers now use a dot matrix that is more from the 1980s than 2010s. Their older LED bar style is easier to read. The other item is that computers like the Shearwaters are color. Much easier to read.

At this point there are folks like my wife who switched from a Petrel to a Perdix and are selling their computer (shameless plug). So do not be afraid to look for one on the used market.