Please try this test on your fins!

[irishsquid]

Irishsquid, I have never been into frog kicking, but this recent hockey fin model made me enjoy the forward spring after using a frog kick. I do feel this model will change how fast one can go frog kicking. If I get a extra pair to send out for your comments I will let you know. Thanks for your interest and comments, Best, Bob

Thanks for the offer Bob! I'm always open and willing to learn. I started diving with split fins and really liked them. Then I started doing a frog kick and didn't seem to have any problem using the splits to do it. I then tried a set of Slipstreams after hearing that the paddlefins are better for a frog kick. They really worked for me and I haven't used my splits since. I like frog kicking because I'm a slow, sloth type of diver, but have been able to keep up with my dive buddies(flutter kick) using 1/3-1/4 the number of kicks and much less air. If the new model you are describing works as advertised, I may be able to move with a lot less kicking and stay down much longer.

 

[weaserm99]

I work with several of the divers that participated in the fin study test, yes the split fin was even more efficient when it was taped due to the way the water started moving off of the fin. One of the other things that should be noted, many divers when they first tried the split fin did not like them, when talking to these testers it was due to the fact that they were so used to their paddle fins. One tester even told me that he wanted to make the one pair have better results due to using them at the time. As for the longest and stiffest fin, one of the testers is my boss, when it comes to leg strength there isnt another person that i can compare him to (i have never seen him out kicked), his results for the Attack fin were off the charts. It should also be noted that some testers could not move the attack fin through the water.

The fins tested

Mares Attack
Apollo Bio Fin
Apollo Bio Fin taped
US Divers Blades
Scuba Pro Jet
Mares Avanti Quattro
Oceanic Ocean Pro
US Divers Compro

Just another side not, one of the divemasters that was working with the shop came back to diving after about 5 years of not being active, when he saw split fins he believed it was pure hype and they were duping people, I finally grew tired of this, gave him my split fins, told him to take them to the pool and compare against his paddle fins, the next day he was buying a new set of split fins.

Are split fins ideal for every condition, NO, and sales reps have even admitted it to me. Aeris for instance just released the Velocity X3 fin this past summer, they took the design of their split fins and made it into a paddle fin, creating the taping effect, after watching several of my students in the water use these fins last night i could see that they were working like the taped split fin.

As i type all of this i have the fin report right in front of my eyes, most of it is in extremely complex formulas, and no where in here do i see anything about being able to snap the fin into the air to measure efficiency of the fin.

 

[meesier42]

Ah but he did

"To improve performance of the fin, the time required to complete the transition should be minimized."

how this applies, is that a fin with very high "snap" or rebound will have a reduced time in the transition where little thrust is produced, and if you read a paragraph prior, this high rebound fin will also not loose as much "pressure" on the face of the blade and will produce more average thrust during the now shortened transition period.

followed by

"The transition and recovery phases provide little thrust, and in fact, added to overall drag... As most of the power was produced in the power phase, and little in the recovery phase, it may be advantageous to have higher thrust in the power phase but relieve the force required for the recovery"

which, if you know anything about the Force Fin design is the base concept of how they work.


so, as I already stated, the fin flipping demonstration is just that a demonstration, is to show that this type of material, while quite flexible has amazing rebound creating a significant improvement in the overall efficiency of the fin.

 

[Susanne]

weaserm99,

A Foil Force, split fin, performs better without duct tape.

Thank you for posting the list of mass merchandised fins tested by University of Buffalo here on the Force Fin forum. It shows how conspicuously absent the following Force Fin models were from this test: :

Original Force Fin
Pro Model Force Fin
Tan Delta Force Fin
Foil Force Fin The first to market of what has become known as "split fins"
Extra Force Fin
Excellerating Force Fin
Adjustable Force Fin
Beaver Force Fin

Most interesting is how the conclusion in this study is likewise as conspicuously descriptive of a Force Fin.

Force Fins were included in an earlier and more comprehensive study also conducted at the University of Buffalo... Would love to visit there sometime. It sounds like quite an interesting facility. Navy Study

Well in answer to your question...... Fins generated propulsion by moving through the water. If your leg is required to do all the work, then its less efficient than a fin of the same characteristic that rebounds or snaps to do some of the work for you.

Speed of that movement is shown by the rebound, or size of your bounce, and is directly related to how fast the water moves behind. A fin made of resilient, or snappy material, like polyurethane, is going to move water faster than a fin made of dead material...... Yeah, the University of Buffalo did not measure, or control for material, in either study... so do your own test.

Take the fins listed in your post, bend them as Bob does in his video, pull them back, hold for a second or two, the let them go. Measure how high they leap and compare that with the results obtained in the study to see if there is a correlation... If they can't leap as high as a hand cast polyurethane Force Fin, then as Bob says, "Wrap it up like a dead fish and throw it away!"

 

[Splitlip]

Irishsquid, I have never been into frog kicking, but this recent hockey fin model made me enjoy the forward spring after using a frog kick. I do feel this model will change how fast one can go frog kicking. If I get a extra pair to send out for your comments I will let you know. Thanks for your interest and comments, Best, Bob

What is the "Hockey" model.

I have originals and cannot frog kick with them. A frog kick is opposite of the down stroke so to speak.

 

[irishsquid]

What is the "Hockey" model.

I have originals and cannot frog kick with them. A frog kick is opposite of the down stroke so to speak.

Hey Tim, I was going to ask the same. After Bob replied, I started searching and couldn't find anything on them either. You made the observation I couldn't describe earlier; the frog kick gets propulsion during the "recovery stroke" and the frog kick "recovery stroke" is what would be the "power stroke" phase, with the blade on edge to reduce the drag as you load up for the next kick. I was originally thinking that if the Force Fin was made in reverse fashion they might work frog kicking.

Bob, if this hasn't been tried (the Force Fin made in reverse fashion), that may be a new product down the road for you.

 

[csicnomore]

" The First Review " on the next page of threads is all about the yet unnamed "hockey fin" and you can find some by searching this forum. Bob, Blair, or Messier42 can tell you more. It's also what I showed a picture of to Sibermike7 in that thread we were kidding him with.

 

[Splitlip]

Hey Tim, I was going to ask the same. After Bob replied, I started searching and couldn't find anything on them either. You made the observation I couldn't describe earlier; the frog kick gets propulsion during the "recovery stroke" and the frog kick "recovery stroke" is what would be the "power stroke" phase, with the blade on edge to reduce the drag as you load up for the next kick.

LOL. You did a better job of amplifying than I did.

Thanks.

I really am curious however.

 

[meesier42]

the hockey fin is a very different fin indeed. the demo was actually done using a Hockey Fin in some really special material. At many request I was able to convince Bob to make the Hockey Fin for me, its purpose designed to excel at underwater hockey. The first version, the one that you see earlier in this thread leaping off of Bob's knee is in XXL, much too big a boot to work really well for barefoot use, but using a pair of comfort insteps in each fin I was able to play hockey quite well in them, I have since started using them for diving as they just fit my drysuit boot. I have found this first version, while requiring some tuning for hockey, turned out to be one hell of a diving fin. It is very similar to the Excellerator, but has the "whiskers" built into some very low profile tabs at the end of the blade that are very effective at stabilizing the fin despite their small size.

For frog kicking they are noticeably different than the Excellerator. While similar in its ability to perform very fine movements with absolute precision. The far end of the Hockey fin is beefed up which shifts the flex profile enough to allow an extremely powerful frog kick, my initial dive with them showed that I was kicking once for every 2 times the guy with me was (in Jets/Turtles)

 

[Blue Sparkle]

I think the Force Fins look really neat -- I'd love to try a pair sometime Among other things, I love the idea that you are powering them with leg and front of ankle and not with foot and toe (I know, you do power regular fins with your legs, but there is that pointed toe thing with the full foot vs. the open toe...)

I have a question though, and what it's probably going to do is show my complete ignorance (but that's okay - I'll learn something new. )

I was thinking about physics law of Conservation of Energy: Wouldn't that mean that if a fin is more resilient, like a Force Fin, that you have to put more energy into it in the first place? I mean, so that it can then "store" it and give it back to you in the way that a Force Fin does?

Or can the fin "give back" more than you put in? (Maybe it's not a closed system? Or... something else physic-sy?)

I imagine my first thought is not right for some reason, but I don't understand physics enough to know why it's not right.

B.

Later thought: Maybe it's something about the way or timing of how you get the energy back; so that it doesn't even matter if it's not *more* energy than you put in. Like how a snappy wrist makes a Frisbee go.

Even Later thought: But hmmm, the propeller analogy. I guess the propeller doesn't give you back more energy than your engine puts in, but rather wastes less energy than something else that you might put on the end of a shaft. So maybe that's the key: The more resilient fin wastes less energy?

Last and latest thought: I think I'm confusing two characteristics here (maybe). One being the resiliency (snappiness), and the other being the shape (impeller vs. propeller in drawing). With a propeller you can control how hard an engine works and then get either more low end torque or more high end speed, I think (but I think you have to give up some of one to get more of the other, and then there is the idea of matching the propeller to the recommended RPMs of the engine....). With an impeller... I'm not sure how that fits in.

Okay, straighten me out here! Before I think more