Pervasive Fallacy about Split Fins

[Temple of Doom]

Dude, 30 posts on one thread in 4 days, 40 posts total in those 4 days. With all that spare time, if you got another job you might earn enough money to go diving.

I understand my arguments have been persuasive, and if that made you feel like you were being slapped in the face by 'phallacies', perhaps that's why you have resorted to attacking me personally, rather than trying to debate the statements themselves.

If I read the origional post right, the origional offending perverse phalacy is low gear vs high gear, but you may have even confused yourself with stiff fins (navels vs oranges?). As I read the reviews and tests, stiff splits perform better than soft splits, yet we all seem to have assumed you meant non-splits. Due to the high resistance of water, drift diving is the only diving not like climbing a hill and all dive fins are low gear!

You didn't read the OP right. The 'gearing' differences between fins is irrelevant. What matters is the efficiency of the fin (I include the method of using the fin as part of the efficiency of the fin, otherwise it would be completely irrelevant to diving). If you had two fins of the same efficiency, both would propel a diver at the same speed (with the same energy output of the diver). It wouldn't matter which fin was kicked faster/easier and which fin was kicked slower/harder. Gears do not affect efficiency! Please don't counter with automobile gears, I've repeatedly explained why that is a bad analogy, as cars have so many more mechanisims and devices which determine efficiency (though if you *were* able to isolate *just* the gears, you'd find that they do not affect efficiency in any but the most minute friction differneces between cogs).

Non-splits would seem to me to be a lower low gear.

Again, while the 'gearing' of fins is irrelevant, I still find it curious how you could claim that a fin which requires more effort less often is a lower gear than a fin that requires less energy more often?!

If is a big word! A Lambo' is faster than a Yugo, does that mean a Lambo' is more efficient than a Yugo? In the test results you want us to believe, where is the caloric and gas consumption data to conclude one fin is more efficient than another? I was unable to find exactly how efficiency was measured, please enlighten me. I believe the tests showed people going faster in splits but I most definately don't have to accept that they are the most efficient fin!

If you put the same engine in the Yugo, then you'd be able to see which is more efficient. In the case of diving, the diver is like the engine. It's creating a specific amount of energy. The difference in how much of that energy is translated to thrust between different fins. When the only difference is the fin, the difference in thrust indicates the difference in efficiency.

One need not measure caloric and gas consumption rates if one assumes that if the diver is swimming with the same (all out) effort for all trials, then the diver is expending the same energy for all trials. I think this is certainly a fair assumption, though if you have no faith in their methodology I understand how you could feel this is invalid.

Your skill level at addressing logical phallacies in debates is a minority opinion many of us are trying to seperate from fact, and why can't you open your mind to the logical phallacies in the supposed comprehensive tests you are slapping us in the face with?

We've been speaking of the report, but have you read through it?
http://www.scubadiving.com/200510_scubalab_fintest
Let us know which of the data or conclusions you feel is suspect, and why. Where are the logical fallacies, and why are they logical fallacies?

Are you sure a gentle kick results in [ I ]very, very nearly the same thrust[/ I ] as a strong kick? That's what I would call an illogical phallacy! Also, if paddle fins are high gear, shouldn't you be able to go faster than the low gear fins?

Oh, please that's laughable. Not only did you fabricate my quote, but you stuck it into the middle of *your* sentence and then argued against it! :no

Here's what I actually said in a discussion about drag differences some 15 pages ago, where the discussion was how thrust output under the *same effort* is affected by diver velocity (I can understand that if you weren't following the discussion you could be confused):

Swiming with fins provides the same thrust at all swiming speeds (very, very nearly)

It is also a false assumption to assume that the thrust
would be the same if the speed is zero or 4 kts (4 kts is FAST BTW).
There could (and will) be all kinds of efficiencies or inefficiencies that only
show up once dynamic fluid resistance enters into the picture.

Exactly why I added the "very, very nearly" immediately after the sentence. At the differneces in swimming speeds (a few kts), the difference in thrust is negligible. Further as it pertains to the discussion, the differneces in thrust at different speeds are effectively equal for both fin types. Thus making the distinction irrelevant to the discussion.

Please point out the logical fallacy in that. To be sure it should not be taken as fact, but it is a logical conclusion based on how fluid dynamics works and the correlation of results when a diver was swimming freely with max effort and when a diver was swimming while tethered to a stationary object under max effort. If you disagree that the difference in thrust output of a fin will be significantly affected at different swimming speeds under the same effort (and that the differences will be relatively different for each fin), please explain why the tethered/non-tethered results don't reflect this, I would love to be enlightened so.

Also, with different finning technique, how exactly do you come up with the same exact effort?

When a diver is swimming his fastest, regardless of what is on his feet, he is outputting the maximum energy that he can output. The difference in speed will indicate the difference in efficiency.

Do you think that a diver, when swimming his fastest, generates more or less energy depending on the fin he is using? If that were so, you'd be able to find a super fin that allows a diver to output enough energy to heat your home! No, that's not true, the ammount of energy a diver generates when trying his fastest is static (when physiological conditions are equal).

As far as I have seen, most of the tests are about going as fast as possible. How exactly do you conclude the results will be the same at all speeds? Those of us with any inkling of the scientific method cringe at statements like this (most of your statements?)!

Again, I question, did you read the reports? The one quoted above ran a test where the divers used "a kick they would be able to maintain for a period of time without overstressing their leg muscles". This was different from the max effort tests. The results showed a great deal of correlation to the max-effort tests.

IMHO most of your 30 posts in this thread have objective falsehoods in them and some have now been pointed out and corrected.

I'd love to see you point out an objective falsehood that I've stated. I don't want to be right, I want to say what's right. If you point out a falsehood I've stated, I will happily admit it and correct myself.

Craig

 

[Soggy]

I understand my arguments have been persuasive,

No, they really haven't. Actually, not at all.

 

[Blitz]

I am sure he persuaded himself, Soggy.

 

[MauiScubaSteve]

Freudian?

Phallacies?? What would Freud say about that?

definitely freudian.

freudian: of, relating to, or according with the psychoanalytic theories or practices of sigmund.

freudian slip: a slip of the tongue that is motivated by and reveals some unconscious aspect of the mind.

actually just stirring the pot to see if anyone worthwhile would come in this thread, successfully i might add. now i'll fantasize underwater yoga with rona!

 

[MauiScubaSteve]

Swiming with fins provides the same thrust at all swiming speeds (very, very nearly). Further, even if it were applicable, splitfins are low gear, paddle fins are high gear!

Are you sure a gentle kick results in very, very nearly the same thrust as a strong kick? That's what I would call an illogical phallacy! Also, if paddle fins are high gear, shouldn't you be able to go faster than the low gear fins?

Oh, please that's laughable. Not only did you fabricate my quote, but you stuck it into the middle of *your* sentence and then argued against it! :no

Hard to pick a place to start but defending my quoting skills will have to do. Below is the entire post I was quoting you from (page 6, your 11th post). Not only did I most definately not fabricate it, I didn't even have to add the bold.

If you think it through, or if you care to discuss further, you'll see that gearing on a car is not applicable as an analogy. A car needs gears to provide the same thrust at differnet speeds.

Swiming with fins provides the same thrust at all swiming speeds (very, very nearly). Further, even if it were applicable, splitfins are low gear, paddle fins are high gear!

If you were able to input the same energy into two gears, you'd get the same thrust and car speed coming out. The 'high/low gear' aspects of fins doens't affect thrust at all. What affects thrust is efficency of energy required in vs energy output as thrust. If you could design split fins to be less efficient, so that they were the same efficiency as paddle fins, then they'd both move you at the same speed, they'd have the same power. Paddle fins would be like a car in high gear in that you'd kick harder, but less than these low efficiency splits, but you'd still be going the same speed.

There is no such thing as extra force of a paddle fin. It just feels harder, but you kick less, but that's unrelated to the thrust differences. The reason splits offer more power is because they more efficiently use the energy your kicking gives them, this is what's been tested over and over again for the past few years.

If you take a look at the tests they ran, you'd see that they tested split fins while the diver was tied to a stationary object, thus effectively infinite drag (diver drag has pretty much zero effect on fin thrust output). They measured the force that split-fins were outputting in this 'infinite drag' scenario, it was higher than paddle fins, just like it was in 'normal drag' scenarios.

Please let's put this one myth to rest...

Craig

False accusations are not part of inteligent discussion, obviously!

Please don't counter with automobile gears, I've repeatedly explained why that is a bad analogy

Your op seems to indicate gears are part of the myth(s) we are discussing and your post above counters with gears, yet you refuse to answer my question about your use of gears. I ask again, if paddle fins are high gear, shouldn't you be able to go faster than the low gear fins?

 

[MauiScubaSteve]

From your 9th post;

It's important when you're weighing the pros and cons of something to be honest to yourself and others. People tend to over-exaggerate to support their preference about split fins. Doing so only weakens the good points they have.

From your 8th post;

By three kicks and two recoveries, splits could likely have left the paddles behind in total thrust.

However, it's important to note that after each full kick/recovery, the paddles will have generated less thrust/accelleration than the paddles.

Takes one to know one, especially when the good points are so few and far between. A little proof reading might help also.

 

[MauiScubaSteve]

You didn't read the OP right. The 'gearing' differences between fins is irrelevant. What matters is the efficiency of the fin (I include the method of using the fin as part of the efficiency of the fin, otherwise it would be completely irrelevant to diving).

Please do not change your posting style, I really enjoy waiting 5 or more days and a couple hundred posts to figure out what you thought you were communicating in the op. On the other hand, let's look at a few of your other posts:

From your 4th post;

Basically, I'm ok with people not liking split fins, there's lots of reasons not to. What I don't like is if the reason is the one in the OP, because it's just a myth.

From your 6th post;

My only reason for creating this thread is that it seems that a lot of poeple like to cite the wrong reasons for disliking split fins. In every thread about split fins vs paddles you'll find somebody bring up this myth.

...

The myth that somehow you get less power out of a split fin is simply wrong.

From your 8th post;

You're going off the topic of the myth

From your 10th post;

Please let's put this one myth to rest...

From your 31st post;

The topic is designed to explain that there are objective truths about different fins. Often in discussions about the two types of fins, people make statements that are objectively false. That's something that should be pointed out and corrected.

I guess I'm not the only one confused about the topic.

OK, got to get some shut eye before the morning dives. See you all again tomorrow, same bat time, same bat channel.:11doh:

 

[MauiScubaSteve]

We've been speaking of the report, but have you read through it?
http://www.scubadiving.com/200510_scubalab_fintest
Let us know which of the data or conclusions you feel is suspect, and why. Where are the logical fallacies, and why are they logical fallacies?

Efficiency: Six test divers, using a flutter kick in approximately 10 feet of water, swim a straight-line course 65 feet long, including a 15- foot "runway" to allow them to get up to their most efficient kicking rhythm--a kick they would be able to maintain for a period of time without overstressing their leg muscles. Timing themselves with digital stopwatches, the divers complete two runs for each fin. The best runs for each diver for each fin were then averaged.

While I like the runway idea, from what I've observed and personally timed 65' is less than a minute at most non-dry suit divers traveling speed, although there is a considerable difference slowest to fastest. Some divers have had very gentel profiles for the majority of their diving and would be hard pressed to do 65' in a minute. Anyway, how very scientific these scubadiving magazine tests are; for a period of time without overstressing their leg muscles is a pretty subjective speed, but my favorite part is the fact that they average the best timed runs for each fin and evidently the fastest fin wins. This is not efficiency, this is a distance race.:shakehead Does the fin tester know the fastest time wins? How much gas was consumed in 65'? Further more, with regard to the entire test, are the testers equally divided in finning technique; half better paddlers, half better bicycle flutterers, with a similarly balanced amount of goodness/badness at both techniques and a similar multiple balance of tester body size, fitness level and gender (pairs of mirror finners)?

My normal dive site would be a good test; starting at 6' deep, work your way out along the edge of the reef, ignoring all the turtles, octopi and rays, just cruising out until you hit your turn pressure. If you reach the teeth cleaning station or oasis rock (~60' deep and 300yds+ out) before tp, how long do you get to stay? Return in similar fashion, recording the same info you would in your log book; time, max depth and psi consumed. To reduce some variables, test dives would have to be ~ 14 or 28 days apart (slack tides?), at the same time of day (7AM?), when the surface conditions are similar (flat and glassy?), after the same breakfast (same dinner, same drinks, same sleep?). All but the sleep is fairly reasonable parameters. With 4, 6, 8 or 12 divers per dive (following tester balance from above), diving abreast with no more than 6 to a group (5 or 10 min interval between groups) 2, 4 or 6 different fins each dive, each diver using each fin at least twice, also documenting all divers turn pressures. Now maybe we can talk about signifigant efficiency data, for the test divers on this fairly abnormal dive! Actual accuracy with regard to the general dive population is just a function of how well your testers compare to all the other divers in the world who would do this kind of diving!

Now don't we also have to ask ourselves what results would cause the major fin advertisers in scubadiving magazine at the time of the tests (or the time of the publishing) to buy more advertising? Oh no, wait a minute, magazines would never bend the content of the articles to favor the advertisers. My Bad!:no

 

[wettek]

I find it fascinating that Temple can be such an expert on fins, eficiency, thrust and how they relate to gearing etc, when according to his blog he has the sum total of 17 dives. Obviously he has surfed the web a lot to gain all his knowledge???????????

 

[Izze]

I don't think he made himself out to be an expert - rather he related basic mechanics and results from studies. You don't even need to be a diver to do that. From a neutral observers point of view this has been sort of like looking at a debate between a college professor and school children.

Personally I don't really care about what fins anyone else uses. I opted for jet fins (or copies rather, for a quarter of the cost) because they suit me. When it comes to arguing for or against though, Temple has the rest of the thread outclassed.