DIR fin technique questions

[Dyno Bill]

So during the 100 ft swim evaluation how many kick cycles did it take and was it an average of travel in both directions?

 

[Lenaxia]

BTW

I did a swimming efficiency test for myself a couple of years ago. I set 100 feet of line at a fixed depth and did timed swimming trials back and forth along its length. I tried different kick styles and different speeds.

By far, the most efficient kick was a slow flutter kick, significantly more efficient (in terms of SAC) than the frog.

This is exactly what I was trying to get at. For even just looking at scenery, not even moving fast, a slow flutter kick should use less energy than a slow frog kick.

Of course its not scientific proof, but it is in line with my intuition...

 

[Doc Harry]

So during the 100 ft swim evaluation how many kick cycles did it take and was it an average of travel in both directions?

I don't remember the details, but I swam 400 feet during the slow and moderate speed trials. During the high-speed trials it was too hard to swim 400 feet, I probably only swam 100 feet but I don't remember exactly.

My SAC was lowest during a very lazy flutter kick that to take forever to get anywhere. I actually got the most distance per cubic feet of gas doing this than any other kick or speed. Big lesson for us cave divers.

My SAC rose steeply with increasing speed, as expected.

The line of SAC versus speed rose slightly more steeply with the frog kick compared to the flutter, showing that the frog is slightly less efficient (at least for me).

But when you're in a tight cave, and having to maneuver a lot, the frog is infinitely precise than the flutter.

 

[rongoodman]

Aside from its non-silting properties, the frog kick is comfortable for me because it transitions very easily to turns and back kicks--they all seem to flow into one another. I only use a modifed flutter for short bursts of speed or to give my legs a change of pace.

 

[Dyno Bill]

Perhaps my enjoyment of the flutter kick is born out by experience in So Cal waters. There are caves but not many. The kelp forest has always been my passion and they lie along the shoreline on slopes usually. The holdfast is always set on a rocky outcropping and silt isn't a concern but as you might imagine current is usually present along a coast line so more powerful kicking is required more often than not. I found when transitioning to breathold diving and the use of the long fin I had to re-train myself to moderate my kicking force as I would overpower the softer although much longer fins. My extreme enjoyment of the kelp forest is probably why my diving style and equipment has stayed the same for so many years. For me to get lost in mid water in the canopy or just below it is like being in the forest well above the ground and I see no good reason to dive in other places. I have had the good fortune to have dove in a number of places in the world and even while diving a reef in the Caribbean I find myself imagining the kelp forest.

 

[Blackwood]

I have had the good fortune to have dove in a number of places in the world and even while diving a reef in the Caribbean I find myself imagining the kelp forest.

They are quite stunning and unique.

 

[HenrikBP]

Given the resistance to movement in water, I think for any "efficiency" swim tests, you'd have to very accurately time the swims over a set distance.

I.e. in order to accurately determine the most efficient kick wrt. air consumption, each kick style test would have to be perfectly timed to match: swimming 4 x 100' (two laps in each direction) at constant speed and each kick style test should take, for instance 10 minutes (arbitrary number).

Any variance in time would probably invalidate a judgement on air consumption. It may also be that certain kick styles are more efficient at a particular speed than at an other.

Henrik

 

[Dyno Bill]

Due to the variations as you mentioned there is always a variable. We arn't running time trials at Indy so a little fudge is acceptable. I used the technique to help navigation in a limited visibility situation. I used to enter a large cove and do a tour, they may have been several football fields acrossed so I would set a course and start counting fin cycles. When I got to a pre determined count I might have changed course to allow exploration in a different porting of the cove, I also used the technique when guiding other divers but I also used a nav board and payed a lot more attention. It averaged 14 cycles for a hundred ft at a normal pace for myself using Mares Plana Avanti fins.

 

[Dyno Bill]

I lived on the Espalnade for years at Ave I as well as on my boat in King Harbor. The PV peninsula is a great de-stressing spot after work.

 

[TSandM]

Guy, I agree with you about flutter kicking and leg fatigue in Jets. They just aren't made for that, and if that's the kind of swimming someone is doing, I think a fin with more give to it is much better.

The cave divers I know who use flutter more than frog, use a softer paddle fin -- and they kick very slowly.

I don't think there are very many divers doing the kind of dives you're describing, though. If I had to do a long surface swim followed by 3/4 mile of swimming over featureless sand, I think I'd look for another site. We DO have a dive or two like that up here, but they are not done by swimming divers, to my knowledge; only by scooter users.

The DIR principle is to use the right tool for the job. It wouldn't make sense to burn gas and acquire deco obligation swimming through things you don't want to look at, when you can use a scooter to do the job faster. Of course, a lot of scooter use is just because they're fun!