Diving Performance - Beyond Drag (article Series And Discussion)

[REVAN]

I think where this thread ended up is to try and make a point that scuba in general to many people has become way to mechanical and gear reliant way beyond what is necessary. Yeah scuba will always be mechanical in the sense of the tank, regulator, hoses, etc., that is the inevitable mechanical component and always will be, but the rest has incrementally crept in to become what is known today as "mandatory equipment", and to the minimalists this is simply not true.
I'll bet almost 100% of new open water students have no idea of anything beyond what the training facility outfits them in to do their dive training. This would include a modern BCD that is generally very large and cumersome and way over padded, a large amount of weight placed into the integrated pockets of the BC, hoses sticking out everywhere that can cause drag and also catch on things, large consoles that are difficult to stow in a fashion that keeps them close to the body, fins that may or may not be optimal high propulsion efficient designs, ankle weights, a lot of times a very large snorkel that is mandated by some agencies, and in cold water I see poor tank material choices such as using AL tanks since they require more lead to sink making the diver really heavy out of the water.
These students may never realize that there is a much simpler and more streamlined way to dive without half that crap. It's actually safer and more enjoyable not to be encumbered by all the stuff that's supposed to be there to make our diving "safer".
Minimalism is a moving target and can mean many things in many different dive scenarios.
However in the most excessive senarios I have witnessed, putting on doubles, stage bottles, can lights, long boses, dry suits, a buddy, and being towed around by a scooter on a 50' shore dive just because the certain "school" of training says that all that gear must be used on every dive for training purposes and to develop "muscle memory" is kind of the jist of what the thread is chipping away at; to the degree that some diving has gotten kind of rediculous but it may also just be a scubaboard thing since I see almost none of this anymore in the actual reality of Northern California diving. Just like I hear all kinds of stuff about sidemount but have never actually seen one in person. So therefore in my world it continues to remain a myth.

Also the casual recreational diver that likes diving but may not like all the gear they have to purchase, don, and also maintain just to do simple 40' reef dives in warm water. The excess gear can be a real turn off to people, I actually know a few in my neck of the woods that gave up scuba for freediving simply because they didn't know there was a better and simpler way to scuba dive.

I think this thread along with other similar threads in the past have done a good job at exposing hungry minds to think outside of the box and realize there are alternatives to the current industry standard.

To those that are gear heads and love to carry more more more, more power to you carry on, the dive shops love you.
To those that would like to find ways to streamline and reduce their gear to become more efficient in the water read on.

Well put, @Eric Sedletzky . Chipping away is good terminology. It takes time and repetition, as some people are so offended at what they read about minimalist diving that they can't make sense of it. They get defensive about the normal they are used to and then offensive as a coping mechanism to put minimalism down and convince others that they should not dive without the extra gear.

This part is so correct, that it's worth repeating:

These students may never realize that there is a much simpler and more streamlined way to dive without half that crap. It's actually safer and more enjoyable not to be encumbered by all the stuff that's supposed to be there to make our diving "safer".

I'll add to that statement, it can be less expensive too!

 

[REVAN]

I would love to see some serious work on applying some of these ideas in a real world environment.

I kind of thought that's what I was doing here. I adapted to a standard tank, so that I don't need custom manifolded mini-tanks to get the streamlining. As far as boat diving goes, the only thing different should be I don't have a tank valve exposed to put the bungee on. I'll need to do something different if I want to set my kit in a standard bench holder, but that's no different from having doubles. They don't fit the standard single tank holder either. I can make a strap and clip to secure it, so it's not a big deal.

 

[Patoux01]

Gotta work out that stuff before we swim with the Dolphins.

Yeah, gotta make it work backwards as well... going in only one direction is a no-no for me.

 

[John C. Ratliff]

Yeah, gotta make it work backwards as well... going in only one direction is a no-no for me.

Interesting, I'm going to turn the Hammerhead Unit around and try it backwards! I can do that as I'm wearing fins too. Thanks for the suggestion.

SeaRat

 

[John C. Ratliff]

Revan and John C. Ratliff, what are your thoughts on kick technique and fin stiffness ?

I am trying to keep my legs straighter, with less knee bend and toes pointed throughout. Not so easy on the up kick. Should I keep my kicks narrow and quick, medium width ?

What about fin stiffness ? My fins are very soft. I know freedivers like a soft blade. Would a slightly stiffer fin be good for scuba since air consumption is not as big a priority ?

Keeping the legs straighter helps, but you need some ankle flexibility to point the toes optimally. I use varying kick styles depending on the situation. If I am in a silt-up situation, than the kick is short and quick with my fins mostly over my body. But if I want to move quickly, I take a full kick, or a series of them, to get going and keep going. After you get to the speed you want, you can go to a more medium width kick to maintain the speed.

Now, on buoyancy compensation, realize that I started diving before buoyancy compensators. I also had a hand, through testing concepts in buoyancy control and writing in NAUI News and at the IQ-6 and IQ-7 (the Sixth and Seventh International Conferences on Underwater Education) in developing buoyancy compensators. I demonstrated Bill Herter's BCs, for instance, which led to the jacket BC (this was before Scubapro came out with theirs, and they were in attendance at these IQs).

Buoyancy compensators were developed originally for use by divers wearing thick wet suits. Dry suits had their own buoyancy compensation system (by inflating the dry suit), and so didn't need a BC. We dove dry suits in the 1970s sans BCs (see the photo below). I have dived in Clear Lake, and at about 35 feet taken off my weight belt (16 pounds at that time, when I weighed about 165 pounds), and dived weightless sans any weights. When I wanted to ascend, I pulled the weights off the loop I had placed in the boat's anchor line, and went back up with my weight belt (every diver should know how to place, and take out, a butterfly knot in a line).

Now, BCs are "standard equipment" needed on all dives, tropical or not. A thin wet suit doesn't loose buoyancy, and therefore doesn't need buoyancy compensation by an external device. We dove tropics with an inflatable vest or LPUs (underarm life preservers), but no BC. BCs now cost more than regulators, which is quite odd in my way of looking at things. I don't think there has been a decrease in fatal accidents for divers because of BCs either, and BCs were implicated in a significant number of fatal accidents:

Buoyancy Compensator
In 8% of cases the B.C. malfunctioned. Usually this was due to failure of the inflation

system, but some B.C.s did not remain inflated.

In 6% of deaths, the B.C. was misused. Some divers confused the inflation and dump valves, usually causing over-inflation of the B.C. and precipitating an uncontrolled ascent. Others pressed the wrong button and sank when they wanted to float.
http://www.divingmedicine.info/Ch 34 SM10c.pdf

http://www.rf30.org/final2012/wp-content/uploads/2013/02/Denoble-Diving-fatalities-by-numbers.pdf



'Just wanted to give a bit of perspective.

SeaRat

 

[caseybird]

I kind of thought that's what I was doing here. I adapted to a standard tank, so that I don't need custom manifolded mini-tanks to get the streamlining. As far as boat diving goes, the only thing different should be I don't have a tank valve exposed to put the bungee on. I'll need to do something different if I want to set my kit in a standard bench holder, but that's no different from having doubles. They don't fit the standard single tank holder either. I can make a strap and clip to secure it, so it's not a big deal.

Doubles will sit in a standard tank holder at the correct height for donning/doffing. The tailcone, by design, will raise the tank substantially and will not sit without some kind of holder that needs to be a lot more secure than the average plastic clip with bungee design we're used to.
One solution for the tailcone issue might be a quick disconnect attached to the tank, but this would require a second person to add a cone to the tank after the diver stands up. This might not work for really small boats or backroll entries. Or you might have to design a new kind of tank holder that will accommodate the tailcone, while allowing the diver to don/doff with some ease.
The forward fairing would have to have: quick (no tools) attachment, redesigned valves that extend beyond the fairing, and appropriate cutouts for the hoses. The hose issue might be simplified by adopting some variant of the Mares Hub system with an integrated LP hose to the BCD (I'm not giving this up) and going to an air integrated computer with pressure read out in your computer or mask. One of the problems you have here is that the minimalist diver who might adopt some aspects of your system might well refuse to adopt an air-integrated computer. The mares hub and the sherwood system with the built-in inflation/deflation lever was, to put it mildly, not widely accepted by the community.
The Hogarthian hose routing with a long hose and bungeed octo might be a good solution to the hose streamlining problem. The octo is nearly universally accepted, and won't be discarded by all but a few divers.
Other aspects of streamlining can be easily adapted, such as storing SMBs and reels in pockets rather than dangling from D-rings and hooks. Lots of low-hanging fruit here.
Good luck,
SS

 

[John C. Ratliff]

Caseybird,

What about a flexible forward fairing on a set of small doubles? The doubles could sit below the shoulders, and have a thin, formed neoprene sheet fairing.

SeaRat

 

[caseybird]

Caseybird,

What about a flexible forward fairing on a set of small doubles? The doubles could sit below the shoulders, and have a thin, formed neoprene sheet fairing.

SeaRat

I saw someone with a rig like you describe a few years ago, looked like twin 40's hard manifolded to one center valve and post. Even without a fairing, it sat really low, the diver was a smallish person and it seemed like a very nice adaptation. I thought it would be a super stable rig, the wide low sitting tanks would not induce a lot of roll.
Certainly worth looking into. Without the double valves and posts and a simple backplate wing mount this could make for a nice rig. With a single center valve post there would be less training/complexity/acceptance issues. If the tailcone was left off, it would sit very comfortably on a conventional boat bench. Revan understands the drag issues better than I, leaving off the bottom fairings might cost some serious drag.
Years ago I read some comments about the Cousteau style fairing that indicated that draining water/air from the rig created issues entering or exiting the water. The simple open bottom fairing on the leading edge you suggest might solve a lot of these problems.
Cost wise, 2 40' tanks with a manifold and a single reg cost more than a single 80' tank and reg, and a lot less than twins with a manifold and 2 regs. Also, less training. There is some cost to adapt this system, but probably not a deal breaker.
Interesting.
Best,
SS

 

[REVAN]

Doubles will sit in a standard tank holder at the correct height for donning/doffing. The tailcone, by design, will raise the tank substantially and will not sit without some kind of holder that needs to be a lot more secure than the average plastic clip with bungee design we're used to.

As far as putting the kit on, it's not much different from a standard kit. It free stands on its own, probably with more stability than a typical kit because of the tripod foot on the tailcone. I can put it on with it sitting on the ground, at bench level or table top level. I've tried each of these and all these options are viable.

 

[REVAN]

My 17 lb wing is pretty small. I don't think it adds much drag resistance.

00542.MTS.Still001

• ronscuba
• Apr 3, 2016

Revan and John C. Ratliff, what are your thoughts on kick technique and fin stiffness ?

I am trying to keep my legs straighter, with less knee bend and toes pointed throughout. Not so easy on the up kick. Should I keep my kicks narrow and quick, medium width ?

What about fin stiffness ? My fins are very soft. I know freedivers like a soft blade. Would a slightly stiffer fin be good for scuba since air consumption is not as big a priority ?

In general, I like to use fairly small kick amplitudes. Comparing your kick in the picture above to my kick in the videos shows your kick is quite large by comparison. I don't know if this is your normal kick, or just happens to be what was going on when the picture was taken, but you may want to try smaller amplitude kicking to see how it goes. Different fins may respond differently as well. What kind of fin blade do your fins have?

As for blade stiffness, I think a scuba fin will lean toward a slightly stiffer blade than a freediving blade. Not all fin blades are the same. There is more to a good blade design than just blade length and an expensive FRP material. I look for fins that have a soft floppy tip even on a stiffer fin blade (ie - it should have a lot of taper to the stiffness along its length). That soft tip is what makes the fin efficient. If the whole fin is stiff, it will absorb a lot of power, but won't efficiently convert it to thrust. It just feels powerful while bombing the bottom with off-axis waste momentum instead of pushing you forward.

This is the main reason most scuba fins are so poor at thrust efficiency. Take a pair of jet-fins and add an extra 8 inches of soft floppy fin blade on the end and it would probably make for a decent fin (except the foot pocket is still pretty cheesy).