Why Jet Fins???

[d33ps1x]

Oh yah...Anyone looking to buy a couple of pairs of Atomics? ;-)

 

[boomx5]

NaCL H2O Boy once bubbled...


Little resistance ensures less muscle fatigue, making you less likely to cramp and/or run out of air as quickly. Less air consumption results in getting to enjoy your dive longer. Conditioning your body to a higher cadence will always prove to be a more efficient approach in any type of physical activity. If you were planning on doing a 15 minute dive, then it wouldn't be as much of a factor. The bottom line is that most people would like to have as much bottom time as possible.

As for kicking faster to get similar propulsion, that's absurd. Two people of equal physical ability, one with paddle fins and one with split fins...the one with paddle fins will never be able to keep up. I've dove with people who use paddle fins and have legs stronger than myself, and when we kick it into high gear, I am always considerably ahead.

what gets better gas mileage, a four cylinder engine, or an eight cylinder engine?

 

[Warren_L]

NaCL H2O Boy once bubbled...


Little resistance ensures less muscle fatigue, making you less likely to cramp and/or run out of air as quickly. Less air consumption results in getting to enjoy your dive longer.

The measure of resistance is only one metric by which your finning efficiency is measured. That alone is not really that relevant. Take off your fins and try swimming. Even less resistance than splits, but you're not going to get too far.

 

[Dive Source]

It would be nice to see one of the dive magazines come out with a some type of swimming machine that could measure resistance vs. thrust and give actual numbers to compare. If you ever look at consumer reports test criteria for products they are much more scientific than Rodales etc.

We have breathing machine tests for regulators that everyone likes to quote, why not hard data on finning performance?

All of the fin tests and opinions you read are only as good as the person who tried them and whatever faults, bias or prejuduce they carry into the test as well as there ability and experiance level.

Whether the tester/contributor is writing an evaluation for a magazine or for his cyber buddies on scuba board, no test that relies on humans swimming is exactly the same each time because it is nearly impossible for humans to repeat things exactly the same each time.

This means that the test is flawed and scientifically invalid so it is only an opinion not a true test.

Of course even if someone does come up with a machine there will probably be debates on all the variables of how the machine works versus individual divers styles and abilities. But at least you could have different catagories of comparison for the test (i.e. current, body mass, diver drag, diver cross sectional area,frog kick, dolphin kick, fin area, water temperature and density etc,etc...)

Once machine I could envision would be a manickin that has legs that move via electric motor in a standard flutter kick at a set rate using a set force. The manicken could be dressed in standard gear submerged in a pool and made neutrally buoyant at 5-6 feet below the surface. The cyber diver could then be hooked to a wire running the length of the pool and simple time trials could be done or the energy used by the motors measured.

This of course is just one idea, perhaps some of the scuba DIY guys could add some more.....

 

[jonnythan]

Dive Source once bubbled...
It would be nice to see one of the dive magazines come out with a some type of swimming machine that could measure resistance vs. thrust and give actual numbers to compare. If you ever look at consumer reports test criteria for products they are much more scientific than Rodales etc.

We have breathing machine tests for regulators that everyone likes to quote, why not hard data on finning performance?

Because there is so much more going on biologically in the leg and abdomen muscles that can't be even remotely approximated by a simple "work per foot" metric. It would be almost completely worthless. Also, there's a lot more to finning in SCUBA than hauling butt without slowing down in a single direction until you run out of air.

 

[Dive Source]

jonnythan once bubbled...


Because there is so much more going on biologically in the leg and abdomen muscles that can't be even remotely approximated by a simple "work per foot" metric. It would be almost completely worthless. Also, there's a lot more to finning in SCUBA than hauling butt without slowing down in a single direction until you run out of air.

Perhaps not but wouldn't you agree that it would be much more valuable than what are currently only opinions without hard data?

If you go buy the argument that a mechanical testing is completely worthless is human testing even less value?

Don't get me wrong, I hear what you are saying and agree that a lot of stuff is going on in the human body, but does that mean accurate fin testing is impossible?

The navy tests propellers on Submarines, Airplane makers test wing designs, racing yaught hull designs get tested, Bicycle companies test bicyles so why can't fins be tested with more than just opinion?

 

[MikeR]

Dive Source once bubbled...


Perhaps not but wouldn't you agree that it would be much more valuable than what are currently only opinions without hard data?

If you go buy the argument that a mechanical testing is completely worthless is human testing even less value?

Don't get me wrong, I hear what you are saying and agree that a lot of stuff is going on in the human body, but does that mean accurate fin testing is impossible?

The navy tests propellers on Submarines, Airplane makers test wing designs, racing yaught hull designs get tested, Bicycle companies test bicyles so why can't fins be tested with more than just opinion?

Simple-airplanes, subs, cars ect. can be built identical. No to human bodies are identical. Stong, weak, thin, thick. They all have different results with the same fin. Its like having 1 propeller for every airplane made. It will work great on some not at all on others.

Sac rate also needs to be taken into account when testing a fin. Only humans can provide that.

 

[NaCL H2O Boy]

jonnythan once bubbled...

That's what I hear... and I also hear that splits are not good for use in currents. How is it they go faster in still water and slower in moving water? Besides, I've done my experimenting with splits, and I dive with people in splits. I know how it goes.

I've had absolutely no problems with them in currents. My only guess is that if someone has problems with splits in a current, they are doing something wrong.

 

[NaCL H2O Boy]

d33ps1x once bubbled...


As far as diving wet I still have a problem with a lack of resistance. What good is that if you have to therefore kick 10 times as much in little kicks to go the same distance?

You expend far less energy kicking at a higher cadence than with large, slow kicks against higher resistence.

 

[NaCL H2O Boy]

boomx5 once bubbled...


what gets better gas mileage, a four cylinder engine, or an eight cylinder engine?

Or you could use another analogy:

What's a more efficient and effective style of riding a bike....spinning a high cadence with less resistance or grinding a lower cadence with high resistance? I bet Lance could answer that one for all of us.