Are split fins really that great?

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bwerb once bubbled...
The argument here revolves around physics...split fins and paddles use two different methods to propel the diver forward.

Um, not quite. The laws of physics don't change. And while the sales pitch claims to be based on a different part of physics, I'm yet to be convinced that they actually understand the physics behind their product and that their whole claim about being able to "push" off of turbulent flow isn't a complete and utter crock.

If you use the flutter kick with paddles...guess what, your legs will get really sore from moving such huge quantities of water. If you do to it with splits...they do what they are designed to do and propel you forward with a slightly different mechanism.

Splits move less water. You make up for it by kicking at a higher rate, just like the "bicyclist in a lower gear" analogy. This is not Rocket Science. You can do the same thing with a paddle fin by going to a physically smaller paddle (and a less stiff paddle), all without even a pinch of pixie dust in the physics.

In any event, any "best fin" decision must be made based on an objective assessment of a diver's needs, and this includes factors other than anything as simple as a fin's efficiency in a single situation.

Part of the challenge that we have is to avoid the "Placebo Effect", where we honestly believe that some new product must be better, because we spent $150 for it, gosh darn it. There is Snake Oil for sale in the dive industry, just like everywhere else that the consumer has to be careful to recognize and avoid.


-hh

 

[zeN||]

According to the engineers who make the Apollo fiins, quite the opposite is true, people ASSUME because a traditional fin requires more work, you are getting more thrust, you get used to the feel of the older fins, and you judge the split fins by that sensation, and write them off because they feel comfortable; look at the design of a fishes tail, does it look like a paddle or a split fin? It's worth looking at their theory behind their split fin, makes sense to me, lots of people feel they are getting better performance from the split fin, can swim farther, without nearly as much fatigue, all new designs and concepts are generally received with scorn until the proof is too hard to ignore zeN||

 

[bwerb]

-hh once bubbled...


Um, not quite. The laws of physics don't change.

I never said they did...although I completely understand your point...you misrepresented mine...the actual "fin" mechanics of a "stroke" using a flutter kick with splits and paddles are different.

They "feel" different because each fin is developing thrust using a slightly different mechanism...yes the physical laws are the same and don't change BUT...each of these fins is different in their application/utilization of the laws.

 

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bwerb once bubbled...


I never said they did...although I completely understand your point...you misrepresented mine...the actual "fin" mechanics of a "stroke" using a flutter kick with splits and paddles are different.

They "feel" different because each fin is developing thrust using a slightly different mechanism...yes the physical laws are the same and don't change BUT...each of these fins is different in their application/utilization of the laws.

I think we're still in disagreement. What I'm saying is that just because somone claims something doesn't automatically make the claim true.

And that this is separate from if they actually have a good product or bad (its possible that they have a good product, but simply not for the reasons that they claim it is).


To back up a second to zeN's post, where he says:
"According to the engineers who make the Apollo fiins...It's worth looking at their theory behind their split fin, makes sense to me..."

Beem there, done that.

Five years ago, I communicated with them and asked for a detailed technical explanation of this supposed "propeller" technology claim. Bottom line is that they didn't have any engineering analysis of the flow dynamics or any scientific proof that what they claimed was happening actually was. Sure, the idea sounds seductively appealing. They might have gotten lucky and stumbled across something that does work better, but there's a big difference between getting lucky and being honest enough to admit that, and claiming that they've found some profound new application through a previously unrealized theoretical understanding of flow dynamics.

So when they then go and make claims about "Propeller Technology" BS, it is just that: BS: they have no proof that their claim is right or wrong. This improper claim undermines the legitamacy of their product, be it good or bad.


In my opinion, their product's performance is more likely to be a simple derivative of that which we've known about paddle fins for a long time: you can reduce fatigue, swim further and cramp less when you're pushing a smaller and/or less rigid fin.

And ponder this: the split design allows the fin to remain physically large in cosmetic appearance, but mechanically small in its action.


When they have an Engineering Paper that's worthy of professional publication, I'll review their science claims again. In the meantime, my position is that while their product might do what they say it does, the *HOW* it does it part doesn't stand up to meaningful technical scrutiny.



-hh

 

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Oh, and a PS for zeN:

If you do call them, ask for the Names, disciplines and P.E. Licence numbers of their their supposed "Engineers"who are staking their professional repuations on these claims...


...bet ya that their response will be a "HUH? Whazza PE?""


-hh

 

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n/t

 

[bwerb]

-hh once bubbled...


I think we're still in disagreement. What I'm saying is that just because somone claims something doesn't automatically make the claim true.

When they have an Engineering Paper that's worthy of professional publication, I'll review their science claims again. In the meantime, my position is that while their product might do what they say it does, the *HOW* it does it part doesn't stand up to meaningful technical scrutiny.



-hh

Why you would chose to speak with the engineers at Apollo instead of those at Nature's Wing is beyond me...how about this little write-up...Engineering

Sure it's not a scientific paper but it might get you one step closer to talking to the designer vs. a licensee who may or may not have any idea what he is talking about.

 

[diverbrian]

Finhead_Chris once bubbled...
I own SCUBAPRO Split-Fins and Mares Avanti Quattro Fins.
Almost ended up owning only the Split-Fins quite recently , right DiverBrian?? Hee Hee....

Both the wife and I use the Split Fins when drysuit diving in freshwater, but will switch depending on the type of dive. Prefer the Mares in strong current situationsand for backup use if a buckle breaks or I lose a fin. After using the split fins, the Mares feel like a couple of boards were strapped to my feet for awhile.

Tried the splits out in Cozumel and they just felt weird in
that environment. Wife and I both opted for our paddle fins
at that time. My split fins are sized for use with drysuit boots
and are a little big for wetsuit boots, so I usually pack the
Mares when travelling.


Chris

I have found that contrary to belief, I can swim in a current with splits. I can do frog kicks and I can even helicopter a bit (OK, my legs get sore trying it, but that is another issue.) That probably comes from owning only splits in my diving time and just learning to live with disadvantages as well as advantages. The owner of the LDS here does the same as I have never seen him outside of splits except in pictures of the "old days".

But, it doesn't take an engineering degree to figure out if I am trying to drift (I never have done a drift dive myself, unless you count those ripping Tobermory surface currents that stole that Mares fin that I was trying out .) that those "boards" would direct me better than the softer splits that I own and that I could use them as a rudder, much in the same way that I would direct a canoe with the paddles in a current.

I will stay out of the debate regarding the engineering of the splits. The people that want to argue (er... ah... debate )about that......

continue your debate and I am sorry for interrupting the thread.

 

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bwerb once bubbled...


Why you would chose to speak with the engineers at Apollo instead of those at Nature's Wing is beyond me...how about this little write-up...Engineering

Sure it's not a scientific paper but it might get you one step closer to talking to the designer vs. a licensee who may or may not have any idea what he is talking about.

My apologies for the incorrect pronoun reference...it wasn't Apollo who I talked to, but the inventors themselves - Bob Evan's group.

Secondly, I happen to subscribe to M.E. magazine, and have worked with some of their Editors. For the article in question, I almost wrote a letter to the Editor over the article you referenced. Two things that immediately jump out is to try to figure out how a symmetrical "wing" cross section can ever induce asymmetrical forces (eg, "lift"), and note also how the article contains absolutely no data (numbers).

Unfortunately, it wouldn't be the first time that ME has been taken to task for propogating unsubstantiated claims of others. The most recent example is in the current issue (Aug 03), page 8: check out what Robert Woods PE had to say about a claim from TRIZ that ME republished, specifically how it is possible for a 20 year old inventor who claimed to have studied the intellectual property in 200,000 patents to actually have the time to do that (at 10 minutes per review, 9 hours/day since he was 12 years old...yep, happens every day!).

Again, I'm not flat-out saying that it doesn't work...merely that their "scientific" explation is hand-waving smoke and mirrors.


-hh

 

[zeN||]

What is it with you guys and your jet fins, I even took mine to the pool yesterday to try them again after listening to such high marks on the forum, and they felt like lead weights, like bad shoes on your feet-to each his own scales and fins I guess zeN