1. What are the benefits over inhale for constant weight
2. Is there any advantage to doing it for Dynamics
3. long term would it be possible to equal inhale dive depths/ distances using FRC?
DD
After 3 years of FRC diving, I would answer with my opinion as follows:
1. Benefits for CW
- Far greater enjoyment, due to no stressful packing, no stressful final breath, no danger of packing blackout, no complicated water entry and difficult descent technique. No narcosis, no feelings of doom/fear at the bottom, much better feelings in the lungs, feeling more squeezed and bloodshifted like a seal. In general, just a far greater enjoyment of the dive. Also, much shorter recovery between dives when diving in succession. Great enjoyment of the long sinking phase.
2. Dynamics
Laminar and I have recently started doing FRC dynamics in the swimming pool. While FRC does, at first, seem to give no advantage in the pool, it seems I may have been mistaken about that. Quite frankly I have been astounded at how far we have been swimming. How is it possible? Possibly, a far lower drag due to much smaller lungs and smaller chest (i.e. smaller frontal surface area). This allows a much faster speed than with giant lungs from packing. Almost no ballast or neck weight is needed, further reducing drag. Greater hypoxic tolerance due to better blood flow to the brain means you can push way farther without a BO. During packing swims, blood flow to the brain is seriously impeded by the huge pressure on the heart. Ultimately, it appears that the 'limit' for swimming FRC dynamic is only somewhat shorter than with packing, but not dramatically.
3. Distances/Depths: FRC vs. Packing
For dynamic, the ultimate distance seems to be a bit less, though I still find it far more enjoyable than a packing dynamic. For constant weight, the story is far more complicated. After my FRC dives at Vertical Blue 2008, I was able to get a more accurate estimate/calculation of the plausible limit for an FRC constant weight dive. According to my estimate, 120m FRC CW is very possible -- more than that is possible, but you never reach the theoretical max, so I think 120m is practical. The dive would last far shorter than a similar dive with packing. This would also be possible with virtually no CO2/N2 narcosis or O2 toxicity, which is the current limiting factor for packing dives. Although packing divers like Mullins could theoretically do 150m in constant weight if it were not for narcosis/O2/CO2 problems, I predicted many years ago that a wall would be reached around 125m which would be almost impossible to pass with packing. So I would say that once you adapt to FRC diving, and your residual volume shrinks, and equalizing becomes easy, then your depth can be very similar to with packing.
Laminar and I are hoping to challenge the world records in CWNF and CW at Vertical Blue 2009, with FRC dives.
In my case, I took a huge step back in September 2005 when I switched to FRC, and it was hard to watch everyone else get better and better while I started back at square one. However in retrospect, it was the best decision I ever made.
My only warning is that if you switch to FRC dives, always always dive in very controlled conditions with good buddies & safety at the start. The sensations in the lungs and the breathe-up and everything is so different. You need to breathe-up much less than with packing, and you could inadvertently end up hypocapnic and suffer a major accident. It takes about a year to 're-learn' how to judge your body safely once you switch techniques.
Anyway I hope that answers the questions.
