Why the Compass on the Left Arm?

[PfcAJ]

Another scooter point is that the scooter is driven with the right hand. Hard to navigate via compass if it's on the driving hand.

 

[DaleC]

If you exclude SM and CCR from scuba as a whole, what non gimmicky adjustments have been made to ANY scuba system in the last 20 years?

In regards to dir related equipment I think LED technology is making it harder to justify only using a canlight for certain dives. I think, at the lower end of the spectrum, divers really have a choice between using a simple, cheap LED (perhaps in a goodman glove) for adequate light or an expensive, overpowered canlight (with its accompanying routing issues). Especially if they are into photography or videography, where they already have money and lumens tied up in camera related lighting. In that case, a high powered canlight almost becomes problematic and redundant.

And camera use in general has probably increased as well with digital technology. While that might not make the act of shooting any different it certainly puts more people in the water with cameras, who may have different behaviors and needs than the average diver.

I might also argue that computer use at the recreational level has become so common place that very few people dive without them these days. Trying to maintain continuity by negating their use at the recreational level has probably become a harder sell.

If someone were at say, Port Hardy, doing 4 rec dives a day, kitted to the nines in full dir configuration, but limiting themselves by trying to depth average or dive tables, I'd think they were a little nuts and in some ways, needlessly endangering themselves.

 

[TSandM]

That's funny, Dale! You would have loved the last two groups I dove God's Pocket with, all of whom fit your description to a T.

 

[DaleC]

Were they all on the same page? I can see a group working together (because they are all accepting the same parameters) but a mixed group might have some issues.

In all the above, I'm not saying the dir methodology is wrong, just answering the question about what technology may have an impact.

Here's another one. Heated undergarments. Not much of an issue to tropical divers but I would say the main limiting factor in temperate diving is cold stress. It's what limits most people to hour long dives-they just get cold. I just did a 90 minute dive in 45F today and that's about my comfort limit before cold begins to affect me. I used twin 72's and came up with half volume left, which means theoretically, I could have done about a 3 hour dive just on back gas. Better technology in heated garments may mean that rec level northern divers will begin to push to their equipment limits instead of their physical limits and start incurring real DCS risks.

 

[TSandM]

Yes, both groups were DIR groups.

I agree with you about the concern regarding heated undergarments. I think they need to be used with a solid strategy.

 

[lamont]

Truth be known, it could have been a gut feeling or maybe he had a "noisy" scooter. Remember, this whole thing emerged in the mid 90's and some things have changed since then. Maybe scooters have better shielding now? Dunno...

Dive buddy of mine quite a long time ago tried mounting a compass on the body of a gavin before and went looking for a wreck and wound up experiencing the magnetic deflection. Most compass mounts that I've seen have been on the handle and have not been on gavins.

I've wondered about the big 18/21/24W ballast slug being right next to the compass before, but I've never noticed any deflection from that.

 

[Vegan Shark]

Rather than start a new thread, I'll just ask another DIR question here:

Why is there not a redundant SPG for back-gas, when redundancy is one of the key components of the DIR safety philosophy? Since DIR also suggests having wrist-mounted gauges for ease and quickness, wouldn't an AI wrist unit be the very best scenario, with a clipped SPG as backup? I know DIR usually hates on AI, but what is the rationale?

With an AI unit you have:
- Easier, faster access to your pressure. No unclipping and re-clipping of the SPG necessary.
- Redundancy.

An SPG failure is unlikely, but not unheard of, so why not have redundancy when all the other equipment has a redundant system in place? Even if one were against AI, could still have two SPGs.

 

[Goat_Tower]

Rather than start a new thread, I'll just ask another DIR question here:

Why is there not a redundant SPG for back-gas, when redundancy is one of the key components of the DIR safety philosophy? Since DIR also suggests having wrist-mounted gauges for ease and quickness, wouldn't an AI wrist unit be the very best scenario, with a clipped SPG as backup? I know DIR usually hates on AI, but what is the rationale?

With an AI unit you have:
- Easier, faster access to your pressure. No unclipping and re-clipping of the SPG necessary.
- Redundancy.

An SPG failure is unlikely, but not unheard of, so why not have redundancy when all the other equipment has a redundant system in place? Even if one were against AI, could still have two SPGs.

The Odds of an SPG failing are low. The odds of an AI failing are much higher. I dove an AI computer (Mares Icon HD) for two days before going DIR (not a fun story). I think any thread discussing AI computers over in the equipment forums will explain.

I assume you are referring to manifolded doubles. So, why are two SPGs better? You mention redundancy, but the SPG is just a check on your gas supply. You should always be above minimum gas (enough for you and a buddy to end the dive). If you have a gauge blowout and begin to loose gas, you thumb the dive. If you have a manifold/valve failure, you thumb the dive. After you've thumbed the dive you don't really need to know exactly how much gas you have, you should have enough to reach the surface or a gas switch.

The extra gauge won't tell you anything that the first gauge won't. In the event that you have to close an isolator, you've had a failure and should be thumbing the dive. If you don't have any failures, and you don't close your isolator, then the two gauges will have the same reading. The second gauge won't tell you anything useful.

By contrast, lets say you wanted to add a second gauge: Where does it go? How does it mount? Where do you clip it? How does the hose route? If you want to add a right hip D-ring...where does the light cannister go?

The addition of a second gauge in pursuit of blind redundancy doesn't accomplish anything. The system isn't redundant for the sake of redundancy. In the case of a backgas SPG, the second gauge adds so little to the system, that the benefit is outweighed by the complexity of managing it. This is in contrast to a backup light, which can be slipped into a retaining band, easily deployed when needed and out of the way the rest of the time.

While redundancy is a huge part of DIR, you need to remember minimalism. Keep It Simple Stupid.

 

[DaleC]

If this weren't the dir sub forum I'd argue the point but I respect this as a place for discussing that regime.

 

[Vegan Shark]

Fair points about the SPG.

Right now what I'm mainly having trouble with is the use of a bottom timer for recreational dives instead of a computer. For technical diving I fully understand, but for recreational dives that don't have a square profile it feels like the equivalent of choosing to use a typewriter instead of a laptop, or a horse-drawn carriage instead of a car.

Does everyone actually use rules like 120 and minimum decompression on all their rec dives, or are there a lot of DIR divers who use it just in the class, then go back to computers afterwards?