Why Jet Fins???

[boomx5]

Your answer proves you did not understand my question.

 

[NaCL H2O Boy]

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?

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.....

I've tried my own informal tests with both my paddle fins and splits. I used a stopwatch as well as my Polar heartrate monitor. I timed laps in the pool at my fitness center, while also monitoring my heartrate to measure physical exertion. I made sure to give myself ample recovery time between using each set of fins, so as not to handicap the second pair being used. I found that on average, a 200meter flutter kick was around 5-7 seconds faster with the splits. I also found that with the paddle fins, my heartrate was 10-12 bpm higher at the end of the 200m. I tried this once using the splits first, then the paddles....and then used the paddles first followed by the splits. Now granted this may not be the most scientific test, but the Polar hrm is a pretty accurate monitor and it was showing a higher pulse rate using paddle fins. In addition, lactic acid production in my legs was noticeable much earlier with the paddle fins.

 

[Warren_L]

NaCL H2O Boy once bubbled...


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.

The thing that I think you may be missing here is that there is an efficiency curve. Measure cadence on the X axis and efficiency on the Y axis. Assuming max load, efficiency starts at 0 at low cadence, peaks out at the optimal level and then backs off as cadence goes too high. I used to be a road racer, but nothing like Lance .... and too high a cadence is inefficient as is too low a cadence. Depending on the conditions, there is always an optimal level.

 

[NaCL H2O Boy]

boomx5 once bubbled...
Your answer proves you did not understand my question.

In general a 4 cylinder engine, which operates at a higher rpm, gets better gas mileage. While there are exceptions to this, they are rare.

 

[boomx5]

Is the fin the engine, or mearly the tire that makes traction on the asphalt? Or both?

 

[Dan Gibson]

Of course the opposite could also be said about people who claim Jet Fins don't work as well as split fins. The problem when comparing the two fins is that most people can't frog kick worth a darn. It is not a huge kick as most people will lead you to believe. It is mostly from the ankles and lower leg. Modified is even smaller and uses very little ankle movement.

NaCL H2O Boy once bubbled...


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]

warren_l once bubbled...


The thing that I think you may be missing here is that there is an efficiency curve. Measure cadence on the X axis and efficiency on the Y axis. Assuming max load, efficiency starts at 0 at low cadence, peaks out at the optimal level and then backs off as cadence goes too high. I used to be a road racer, but nothing like Lance .... and too high a cadence is inefficient as is too low a cadence. Depending on the conditions, there is always an optimal level.

I agree with you that if the cadence gets too high, then it does become inefficient. I don't think kicking at twice the rate as with a paddle fin would be crossing into the inefficient zone. I would be surprised if kicking at that rate with splits makes that many people anaerobic.

BTW, I used to race road also. It took me a long time to finally switch from a masher to a spinner.(very stubborn) Once I fully committed to it though, it was an eye-opening experience. It's also much easier on your body.

 

[Warren_L]

The trick is, then is finding the optimal rate. My point was that neither of the opinions are necessarily incorrect - it is a balance between the two. I've since switched from road racing a few years ago to mountain bike racing, and cadence/efficiency issues are even more pronounced.

 

[NaCL H2O Boy]

boomx5 once bubbled...
Is the fin the engine, or mearly the tire that makes traction on the asphalt? Or both?

You could also ask if wider tires or skinny tires affects gas mileage as one will have more resistance than the other. I understand where you are going with your analogy, and I think both parts can be a factor.

 

[NaCL H2O Boy]

warren_l once bubbled...
The trick is, then is finding the optimal rate. My point was that neither of the opinions are necessarily incorrect - it is a balance between the two. I've since switched from road racing a few years ago to mountain bike racing, and cadence/efficiency issues are even more pronounced.

My guess is that the optimal rate for the average person would probably somewhere between the normal rate used with a paddle fin and the normal rate used with a split. Only problem is that attempting to use that rate with either type of fin will more than likely effect the performance in a negative way....unless you use a paddle on one foot and a split on the other.