Advice

[-hh]

Are you suggesting that out-of-shape divers shouldn't dive, or that they should use some sort of crutch?

No to the first part, but maybe to the second.
It is a question of risk assessment and risk acceptance.

From a risk assessment perspective, we can fairly safely say that when "all other factors being equal", an out-of-shape diver will probably be at a higher risk because they're in some way incrementally less capable.

However, that doesn't mean that they shouldn't dive.

First off, from a risk acceptance perspective, they can simply just accept that higher risk.

And there's also the alternative that they may elect to do something about it and lower their risk. What this risk mitigator is may or may not be considered a "crutch" of some sort - it could be that they change their gear, or they could just do more conservative dives, for example.

In any case, for any diver and regardless of fitness ...or any other measure... diving invariably comes down to risk and the process of managing it. Another part of assessment is risk:benefit, which is what ultimately determines acceptance. The devil is in the details of making sure that you've been holistic and objective in your risk assessment...unfortunately, there's a lot that gets skipped over all too often, or we try to pretend that a particular risk doesn't exist.

I happened to choose fitness here because it applied well to the example: if one has a surface floating position that requires the expenditure of energy to maintain one's breathing airway, then fitness is obviously going to be one of the variable factors that determines how long they're able to survive.

Since we're not diving with horse collars anymore, we have a surface floating condition that requires the expenditure of a non-zero amount of energy on our floats. Our modern dive gear does not and will not reliably assure a clear airway for an unconscious diver floating at the surface. This condition is due to equipment selection and is unequivocally an objective risk.

From that point, the next question is quantifying the risk, which depends on specifics and context to quantify objectively.

And after the risk has been quantified, the final stop is for the individual diver to assess and decide if he is going to accept the total level of risk present. Naturally, everyone's risk tolerance/acceptance varies, so this is always a YMMV.



Jim: that you've never seen a mannequin that is able to make minute adjustments is exactly the point: an unconscious or disabled (Bent) or fatigued out diver won't be able to perform such actions to control their body either. And I suggested a mannequin because I spent enough time on the floor ... and outdoors ... to know that what looks good on the computer in the office isn't real until it has been verified through real world testing. If you can't find a suitable mannequin, use one of your dummy engineers and hit him over the head with a brick to knock him out. Just don't phone me at midnight asking for bail money


-hh

 

[g1138]

hh I'm 5'6" 108lbs, dove with aluminum 80 tanks in full 4/3, 5mm booties, lycra hood and 1mm gloves; all in tropical Philippines.
6lbs of weight w/ a 23lbs back inflate.

I fully inflated it at one time when seas were rough, and another time when I wanted to stare at the sky. I never had any trouble with this so called faceplant.
During pool sessions I'm wearing a 3/2 full and 5mm booties with 4lbs of weight; once again w/ Al 80's. No problems either.

No finning, no counter-torque. Just leaning back and balancing or overcompensating so you're laying on the bladder as a cushion, you can do this in as little as a 20degree angle. At one point or another you will shift the weight so the bladder does not shove you face first in the water. You really have to lean forward just to make this possible. Vertical and leaning back you can easily counter-act this.

If the wing has too much lift, then simply deflate. Once again, in tropical waters you don't need to fully inflate a 30lbs wing. Or if you got one of those tech inspired 90's BC's: a 70lbs wing.

 

[-hh]

hh I'm 5'6" 108lbs, dove with aluminum 80 tanks in full 4/3, 5mm booties, lycra hood and 1mm gloves; all in tropical Philippines.
6lbs of weight w/ a 23lbs back inflate....

I'm sorry, but your anecdotal experiences ... as well as everyone else's ... doesn't prove that it is impossible for everyone else in the world to have such a problem.

The reason why is because the scientific process cannot ever 'prove a negative'. The best that can be done is to illustrate that the problem is uncommon.

...I fully inflated it at one time ..

"Once"? I dived with my wing configuration for nine full seasons. The effect was always there if one paid attention to look for it, but you also must understand that that alone doesn't mean that it was a problem on every dive. And please don't assume that I didn't experiment with multiple setup variations to try to make it better...I was able to lesson the magnitude of the effect, just not enough for my personal satisfaction.

Granted, I will point out that part of my decision could be characterized as because I'm being "over demanding", but that stems from years of firsthand dive experience with a Jacket which didn't have the same magnitude of this problem, as well as even more years of firsthand dive experience before that with a horse collar which didn't have the issue at all.

Of course, those other BC designs have their own trade-offs, which is why I said upfront that no gear is perfect. There's lots of things that I don't like about the Jacket that I chose to replace it with (and for some things it is worse), but given my personal priority ranking of the variables involved, doing so was the correct trade-off decision for my needs.

In the end, I still was not satisfied with an element of my Wing's performance, so I finally dug out my wallet to replace the wing with something else. Given how notoriously "frugal" divers are, that in of itself should be quite telling.


-hh