Venting for Drag.

[Bob Evans]

I backed off on comments, since I will never win. I love how people like to talk about fins, yet I have lived 40 years designing swim fins. Some time best just keep to your self. ..and that I have done the past 10 years, lay low and keep below the radar. Have a NICE DAY.

 

[John C. Ratliff]

@Bob Evans you answered your own question with regards to the bias on this board. Frog kicking is the predominant kick used by most people that contribute to this board. Wish you had something that worked for that

I'm going to chime it here, as it appears that you are ganging up on Bob Evans. And he is declining to defend his Force Fins.

Frog kicking is about the most inefficient kick known to divers. It is intended only for one thing, and that is not to throw any water toward the bottom where it can disturb the very fine silt seen in cave diving. This disturbance of silt is potentially life-threatening in cave diving, as it reduces visibility to zero, and disorients divers, causing them to go where they should not go, run out of air, and die. So frog kicking has become the standard for caves, and that was then given as a standard for technical divers too. But, it is not efficient as a propulsive method.

I have just completed a swim in our Tualatin Hills Aquatic Center pool, which is 25 yards in width, and 50 meters in length. We were swimming widths today, as a team was practicing diving in the deep water (16 feet deep, platform diving). Well I tried the traditional "frog kick" with the Force Fins I was using, which were original Force Fins that Bob had given me years ago when we both were evaluating different swim fins (yes, Bob, I still have them). I tried two widths frog kicking, and it took 21 kicks to get across.
(more on this later)
SeaRat

 

[tbone1004]

@John C. Ratliff I'm not picking on him, far from it. His fins work well for what they are designed to do, but the types of kicks being discussed are not those types of kicks. Whether the frog kick is efficient or not is irrelevant to the discussion, unfortunately he decided to delete all of his comments on the thread, so the whole thing is pointless now since we have someone who is clearly going to try to push his product at something as the best thing out there aimed at something incompatible. He then comes talking about how many patents he has in fins, who cares? Having patents only means you came up with a novel idea, not that it actually works, or is better. If he came out and said "we did these independent tests against competitors products, with this methodology, and here are the results" that would be different. Unfortunately it comes across as used car salesman type marketing since there is no evidence behind the claims.
You then go and do the same thing, say you got across the long course with 21 kicks, but nothing about how many kicks it takes for any other fins. His video here proves my point. The Force Fin is designed to grab water on the top of the fin on the "downstroke", and move through the water more easily on the "upstroke". Dolphins have a tail structure similar to the Force Fins with the edges of their tail bending down. Power is generated on the downstroke, with an easy recovery on the upstroke. When you frog kick with a Force Fin *which I have*, you don't generate any power. You can back up like a mad man though. If you are primarily a flutter kicker, great tool for the job, but I am not, nor will I ever be, and many on this board are the same.

I wish he made something that was ideal for frog kicking, and if he did, I would buy them. If they worked, I would advocate for them. Small business aimed at doing one thing better than anyone else in our industry? I'm 100% behind that. Unfortunately that one thing he does better than anyone is not compatible with my diving and instead of acknowledging it, any time he is questioned, he gets very defensive and starts touting patents, military contracts, etc etc which are irrelevant to the discussion.

 

[John C. Ratliff]

@tbone1004, you wouldn't even give me the time to finish my post before replying. The "More later" comment was because I needed to drive my wife to work and drive back. So rather than trying to complete that post, I'll do a completely new one in a few minutes. Here goes for a second try:

Frog kicking is about the most inefficient kick known to divers. It is intended only for one thing, and that is not to throw any water toward the bottom where it can disturb the very fine silt seen in cave diving. This disturbance of silt is potentially life-threatening in cave diving, as it reduces visibility to zero, and disorients divers, causing them to go where they should not go, run out of air, and die. So frog kicking has become the standard for caves, and that was then given as a standard for technical divers too. But, it is not efficient as a propulsive method.

I have just completed a swim in our Tualatin Hills Aquatic Center pool, which is 25 yards in width, and 50 meters in length. We were swimming widths today, as a team was practicing diving in the deep water (16 feet deep, platform diving). Well I tried the traditional "frog kick" with the Force Fins I was using, which were original Force Fins that Bob had given me years ago when we both were evaluating different swim fins (yes, Bob, I still have them). I tried two widths frog kicking, and it took 21 kicks to get across. By doing a simple division, I get:

25 yards / 21 strokes = 1.19 yards/stroke

I think I can do almost as well without fins with my frog kick for the breast stroke than 1.2 yards per kick.

Now, in the early 1960s (yes, I am that old) we on the North Salem High School Swim Team used to use what was then called the "whip kick" with either butterfly or the breast stroke. The whip kick is similar to the frog kick, only it uses the tops of the feet instead of the bottoms (I think it is outlawed for butterfly now). The theory behind it was that it was a very quick kick, and that the top of the foot would provide more surface area than the bottom of the foot for propulsion.

Well, I have used the whip kick with my Force Fins to very good effect. Using the whip kick, I was able to get across that 25 yard pool in 14 kicks. Doing the math:

25 yards / 14 strokes = 1.79 yards/stroke

That is quite an improvement, and it still pushes the water directly behind the diver, rather than downward toward the bottom to disturb the silt. (I have just reviewed the video I took this morning of these strokes, and confirmed this.)

Now, Bob Evans and I go way back, when he was first developing his Force Fins. I have those fins that he first sent to me for evaluation. They still function fine, and they are from the mid-1980s. I have since gone through several pairs a Atari fins, and other plastic fins which have worn out. My Force Fins have not. But, I never did like the loss of the up-stroke with the Force Fins. In the 1960s I began experimenting with a different concept in fin design, one I found was not patentable because someone else had already done it (but in a manner which made it unworkable).

I called these my "scoop fins," and still use them today (different ones though, as I lost the Voit Viking A66 fins during my time in the USAF; photo from 1970 in Alexander Springs State Park, Florida). If you want to make some for yourself, it's fairly easy to do:

But what I've found over the last year or so that I have been diving with my Force Fins, is that the Force Fins actually work pretty darned well. Bob's theories, as explained in his patents, are that the up-stroke on fins provide no real propulsion, but do cost a lot energy-wise. So he minimized the up-stroke, and maximized the down-stroke. Here is his patent, and I would ask that you read the claims he has made for the Force Fins (this, I believe, is his first patent on these fins).

US4929206A - Swim fin with flexible fin member having movable tips - Google Patents

I am one of those "vintage divers," who's been around a while. I have a whole collection of fins, and have been experimenting on them since the 1960s. At one point, I was also the Fin Swimming Director for the Underwater Society of America.

SeaRat

 

[MichaelMc]

When you frog kick with a Force Fin *which I have*, you don't generate any power.

tbone, Are your fins the Original (weaker) or Pros (stiffer)? Not to say that either is designed for forward frog kick, but the originals are not powerful in either direction.

If all you can do is frog, due to silt, something designed just for it is likely best. If you do frog because it it low effort and stable, but can break into a flutter if desired, a multi use fin may be more broadly useful. I've done frog as my standard kick with Pros for 50 some NorCal ocean dives, only breaking into flutter if I want speed. I think the Force Fins are multi use with increasing frog capability as you go from pro to hockey to excelerator.

When I've piped up to say Pros are good fins, I've mentioned they work fine for reverse. That's because the forward frog seems dead simple. *For open water me*. Reverse is the tricker bit. And my reverse in pros is more often the 'fold the sidewalls/tails over' version rather than the 'slide them back sole-to-sole and use their flex as designed' version.

Originals: To me, original are too flimsy for scuba even with flutter. Much less a max speed frog! I think they're sweet flutter fins in swim gear. But I can over drive them just in skin gear. My experience with them is limited to playing with them and pros over a few weeks and one head to head pool play time with both in swim gear to see which I wanted to keep for diving. Originals might be a fine light flutter scuba fin. But I think they have no place in any discussion of against current or with drag while using frog as your everything even speed kick!

Pros: I can speed up and catch Nor Cal flutter buddies using my pros for frog easily. But I can also just switch to flutter. But, to be clear, this is my non-cave trained open water diver frog. I think it is a fine frog, but no one has cave trained my frog kick. So.... When I've swum up current, that had tropical flutter buddies and DMs dodging between rocks, I used flutter.

Hockey: My (forward) frog is much more powerful with hockey than with my pros. Not from any measured face off, just from diving both and my sense. The drag I feel on head and arms is markedly different that with the pros. Reverse much simpler as well. They do not fold over, so slipping them back and grabbing some water to move me back, or turn requires so little finesse it is simplistic.

But it is Excelerator that were designed more for that application. But I haven't dove them. I wanted more tech fin than my Pro's and went with Hockey, not Excelerator, as my reading was that Hockey were more dual use, and I recalled Hockey having a lower entry point on needed power to drive them with flutter.

My two kicks worth. Maybe three kicks worth? frog-flutter-reverse?

ETA: If the cave is covered is silt, how is there high current? Seems like you would not have silt there? So, you could flutter. So a dual use fin could be useful. Particularly if it gave you higher thrust against that current, in flutter. But I'm not cave trained. ?

ETA2: Well, even with no current, you want to make most efficient time over the silt, so frog speed, or at least gas efficiency, is important. Anyway, not my area.

 

[MichaelMc]

@John C. Ratliff, You're not really answering the 'what if you have to frog' question. For some, frog is their critical kick. It has to work well. Are you suggesting whip as a replacement for frog in caves?

 

[Joneill]

I'm going to chime it here, as it appears that you are ganging up on Bob Evans. And he is declining to defend his Force Fins.

Frog kicking is about the most inefficient kick known to divers. It is intended only for one thing, and that is not to throw any water toward the bottom where it can disturb the very fine silt seen in cave diving. This disturbance of silt is potentially life-threatening in cave diving, as it reduces visibility to zero, and disorients divers, causing them to go where they should not go, run out of air, and die. So frog kicking has become the standard for caves, and that was then given as a standard for technical divers too. But, it is not efficient as a propulsive method.

I have just completed a swim in our Tualatin Hills Aquatic Center pool, which is 25 yards in width, and 50 meters in length. We were swimming widths today, as a team was practicing diving in the deep water (16 feet deep, platform diving). Well I tried the traditional "frog kick" with the Force Fins I was using, which were original Force Fins that Bob had given me years ago when we both were evaluating different swim fins (yes, Bob, I still have them). I tried two widths frog kicking, and it took 21 kicks to get across.
(more on this later)
SeaRat

Totally untrue characterization of frog kicking - from an air consumption standpoint, it is the most efficient technique.

It may not be fast, but diving is not supposed to be a race - for me, at least, it is about moving at a relaxed pace to take it all in while maximizing dive time. However, I use different techniques based on the dive environment and conditions.

This is a good summary:
How To Maximize Propulsion With Finning Techniques - DIVE.in

 

[John C. Ratliff]

@John C. Ratliff, You're not really answering the 'what if you have to frog' question. For some, frog is their critical kick. It has to work well. Are you suggesting whip as a replacement for frog in caves?

Possibly, try it and see.

SeaRat

 

[MichaelMc]

Possibly, try it and see.

SeaRat

I've tried dolphin in the pool. Its fairly high energy. I can try whip. Don't really have a cave handy to try whip in with fins.

How have you found it in caves?

 

[John C. Ratliff]

Totally untrue characterization of frog kicking - from an air consumption standpoint, it is the most efficient technique.

It may not be fast, but diving is not supposed to be a race - for me, at least, it is about moving at a relaxed pace to take it all in while maximizing dive time. However, I use different techniques based on the dive environment and conditions.

This is a good summary:
How To Maximize Propulsion With Finning Techniques - DIVE.in

Joneill,

That article is not a "good summary." It states things that simply are not true. How do I know? Well, 60 years of diving in many different circumstances tells me so. Here's a couple of examples:

(Concerning the flutter kick)

The reason for its popularity is quite simply that it is the strongest of all the kicking techniques, and it generates a lot of propulsion. And back in the early days of diving, before the invention of the BCD, speed was the primary way of maintaining buoyancy.

Speed was NOT the primary way of controlling buoyancy, and that's not why we used the flutter kick. Breath control, and proper weighting were our means of buoyancy control.

Frog kick

The aptly named frog kick looks very similar to the leg portion of the breast stroke from swimming. A large and wide kick, that utilizes the full strength of the leg, it is a good, general technique for open-water diving, either in the water column, or close to the bottom. Because the movement and propulsion isn’t continuous, good buoyancy technique is required, though.

Source: DIVE.in

Here, again, there are some discrepencies. It does not talk about the drag from the frog kick, only stating that it is a "large and wide kick that utilizes the full strength of the leg, it is a good technique for open-water diving." It is not a good technique for open water diving. The frog kick presents for a large portion of the stroke too much resistance to the water to be good for open water. Obviously, "propulsion isn't continuous..." That's because the "shape" of the kick has a large "dead area" when the legs are brought up to get the fins in position.

Now, I have seen nothing in this article about the other kick that is the most powerful kick for diving--the dolphin kick. Why is that kick not even mentioned?

SeaRat

Source: DIVE.in