Diving Performance - Beyond Drag (article Series And Discussion)

[dmaziuk]

I can't make a dolphin kick work for me using the F1's (though I'd love to learn). Flutter kicking with the F1's feels really uncomfortable for me.

Try finding fins that fit?

Back kick is the one I avoid, mainly because the amount of propulsion I get from it isn't enough in anything other than very still water. Gotta work on that one. There's an easy cure for the rest of them: get in a pool with a kickboard and pair of swim fins and do laps alternating dolphin and flutter, front and back. And then take fins off and do some frog kicks. Take 600-800 m/yards three times weekly, come back in five years if problem persists.

 

[undrwater]

My fins fit quite well, thank you. When I say "uncomfortable" I just mean the kick feels really awkward. I'm certain it's my kick shape.

Take 600-800 m/yards three times weekly, come back in five years if problem persists.

Buy me some time and I'll oblige you. The only kicks I get to work on in the pool are the ones that keep me from drowning when the kids pile on (they can't help it when Papi is in the pool!).

 

[REVAN]

For clarity, I was referring only to swimming performance of scuba divers. It is an interesting reference though. The human body has not really changed much, but the records in competitive swimming continue to show improvements. Reflecting that on scuba diving shows that technique and training can play a major roll. It is not only about the gear.

The name "reverse dolphin kick" is a term that I created as far as I know. When I frog kick my long soft tip fins (which actually do frog kick reasonably well), I can get better performance from them when I use less leg separation and stroke on more of a 45 degree angle than inward. The frog kick just seems to waste the energy absorbed and released in the fiberglass spring. On the 45, it worked better.

Taking that to the next limit, I rotated the fin stroke from the 45 to the vertical with both fins stroked in unison similar to a dolphin kick but with one major difference. Like the frog kick, the energy stroke is on the back side of the fin stroke with the forward/down facing stroke a coasting motion with very little energy input into the system. The energy stroke is a little like doing a calf press.

The benefits:

1) The fins work together canceling the interference between the fins, whereas a flutter amplifies the interference. This makes the fins more efficient working together than they would be independently. In that regard, it is similar to a frog kick with the fins working together.

2) If there is water being thrown off axis from straight back (a feature correlated to fin efficiency), it is being deflected up and away from the bottom instead of down toward the silt. This should prevent stirring up the silt which is the reason someone would be using this stroke to begin with. Preliminary indicators are that this will be an effective anti-silting technique with the right kind of fin blade design.

3) The propulsion is noticeably stronger and more efficient feeling than the frog kick. More importantly, this stroke does not break the diver's streamline form like what happens when the diver bends their knees and spreads their legs apart to frog stroke. Less drag will mean less thrust is needed and the dive becomes easier and less air is consumed.

 

[dmaziuk]

Buy me some time and I'll oblige you.

Yeah, I know. It's one of the perks of working in academentia: one "recsports" fee gets me into all of the univresity's facilities and those include swimming pools, plural. But on the more serious note, it's like most everything else: 90% practice.

 

[REVAN]

@undrwater - If you missed the video that shows the reverse dolphin kick, it is in this one at about 7 minutes in.

 

[undrwater]

@undrwater - If you missed the video that shows the reverse dolphin kick, it is in this one at about 7 minutes

Thanks!

 

[REVAN]

Okay folks. I did more swimming tests, this time using my DiveRite Transpack 2 and no BC wing. I have a 48" hose on my single regulator with the hose routed in a low drag configuration. It's the kit shown in part 4 of the article: Diving Performance, Beyond Drag - Part 4 – DeeperBlue.com under "Equipment Considerations".

Normalizing the data to that of a freediver swimming with arms at the side, here is how the drag coefficients (Cd)s breaks down:

Cd Freediver = 1.0
Cd Diver with Al80 in experimental streamlined kit = 1.15
Cd Diver with Al80 in DR Harness with no BC = 1.6
Cd Diver with Al80 in OMS BP/Wing = 2.0

As a kit and compared to the OMS BP/Wing:
Ditching the wing cuts the drag of the scuba kit by 40%.
The streamlined kit cuts the drag of the scuba kit by 85%

For the whole diver system:
Ditching the BCD wing saves 20% in total diver drag.
Using the experimental streamlined kit saves over 40% in total diver drag.

Streamlining gear works and can make a really big difference in the overall diver's performance, level of relaxation and efficiency of air use.

FYI: I'm thinking of taking the experimental streamlined kit discussed above to the DEMA Show this year. Let me know if anyone here is interested in this. It is more likely to happen if I receive some encouragement.

 

[ronscuba]

I think your fins will get more interest than your streamline cones.

 

[Nemrod]

Adding fairings, US Divers and others have had marketed streamlined tank systems. They failed.

Are you reinventing vintage and minimalist diving? Tank, single second stage regulator and flippers and mask, already there.

N

 

[REVAN]

Adding fairings, US Divers and others have had marketed streamlined tank systems. They failed.

Are you reinventing vintage and minimalist diving? Tank, single second stage regulator and flippers and mask, already there.

N

This builds on existing scuba equipment. The goal at this stage was not to invent some new form of scuba equipment, but to take what was already there and make it work better.

Minimalist diving has been around, but no one is currently marketing it. Most agencies push for more equipment, even going so far as to claim that more equipment is mandatory. Also, no one has actually made streamlined scuba systems that I'm aware of. They have put scuba equipment in aesthetic looking packs before, but no one has made anything that will reduce the drag of a scuba kit by 85%. This scuba kit did that.