Force Fin ---> Seal Fin Concept

[SeaRat]

I want you to first look at this video of two seals actually swimming. Study the swimming movements.



I have had a set of Force Fins since the late 1980s, when Bob Evans sent me a set for evaluation. I have used them off and on, but never really liked them because of the lack of an up-kick. But, they have one of the best foot pockets in the business, and a nylon strap system that is also very difficult to beat. So I lived with the lack of an up-kick for decades as I used them. They were my pick to take on a trip to Maui, and the three snorkeling adventures Chris and I had there. Why? Well, because they were very easy to get into and out of, their down-kick was quite powerful, and they were easy to walk in. I had already "invented" my scoop fins, which remained my favorites, but they were very difficult to get into and out of at times. Here are the Force Fins:

IMG_0492 by John Ratliff, on Flickr

IMG_0493 by John Ratliff, on Flickr

The Force Fin won favor by a lot of divers and swimmers who would get fatigued, or worse get cramps, using regular fins. The theory that Bob told me was that it was that up-kick which induced the cramps, and that the diver was better off without the fin really doing much work on the up-kick.

But my experience was in rivers with current. What I was finding was that the up-kick was pretty critical in positioning my body in the water column. Without it, I struggled to get my trim in the current correct (horizontal and near the bottom). So I was on and off again about the Force Fins.

But look at the video of the seals swimming. They do have one flipper which collapses, but they have another that takes its place on the reverse stroke (their is side-to-side). So that they don't loose any propulsion on either stroke.

Is that something that could happen with Force Fins?


John

[SeaRat]

I set out to see in 2019. As you know, I had already designed the Scoop Fin that would act on both the down-stroke and the up-stroke. These fins, in my opinion and after my own tests over a thirty-year period, provided the best thrust of any fin. Could a Force Fin be made to do just that, provide thrust on both strokes?

I set out to find out.

(Now, this post is under construction. I hope to figure out how to make a video of some of the recordings I have made too.)

John

[mberna]

You can't go wrong with copying from God. He's got a few years more experience than even the oldest divers and engineers out there. Seems like a lot of the best designs out there are copied from the natural world whether intentional or not.

[SeaRat]

About two or three years ago, I decided to test my theory, and took my pair of Force Fins and lashed them together, back to back. I wore the modified Force Fin on one foot, and my own Scoop Fin on the other, and dived the combo. I was surprised that the two worked well together. So last winter, after watching E-Bay for a long while, I finally found a pair of Force Fins that were relatively affordable (under $50). So I bought them. Here's what I got:

IMG_0491 by John Ratliff, on Flickr
The two outside fins were the E-Bay fins, and I found out after receiving them that they were not a pair, but two different fins, and slightly different sizes. But that didn't matter, as my idea was to combine the four fins into two fins.

So what I wanted to do was to cut off the E-Bay pair's foot pocket, and mount them back to back onto my original Force Fins.

IMG_0496 by John Ratliff, on Flickr

I've now got a pair of Seal Fins (not S.E.A.L., which stands for "Sea, Air, Land" for the SEAL teams), but rather a pair of fins mimicking the way a seal swims.

IMG_0497 by John Ratliff, on Flickr

I have used these fins now in the pool several times, and I now have two dives on these Seal Fins, and they work very, very well. I've found out that in the current, I need to have a fin which has power on the up-stroke, to help me stay where I want to be in relationship to the bottom. I've also got a video of my use of this combination for my Seal Fins, and will hopefully be putting that together in the coming weeks. Now, it's time for me to go diving, and use the Seal Fins on my third dive with them.

John

[SeaRat]

I did go diving today, and got video of my dive too. The dive I planned was not quite how it went, as I planned to use the jacket BCD with my Mossback Mk 3 regulator, which actually I did. But not as a BCD, as when I was donning the tank/BCD in the water the hose for the BCD release line parted. I had effectively a non-functional BCD. But I decided to dive it anyway, just not as a BCD. It had the straps to allow me to wear the scuba unit, so that sufficed.

I dived my Seal Fins too, and they worked exceptionally well. I had full control on both the down-stroke and up-stroke, and that made the dive easy. They were also easy to get into and out of. I spent about 15 minutes at our submerged car wreck, a 1960 Bellvielle, we've determined (see the other thread). I was trying to see whether there was another sticker that I had not seen before on the driver's side door frame, where it's supposed to be. But nope, it's not there. I used my knife to remove the rust and see whether there was a tag underneath, but there was not.

I then swam downstream, and exited after getting some video of me swimming against the current. This video turned out well, and here's a screen shot of it:

Screen Shot 2022-08-22 at 10.47.10 PM by John Ratliff, on Flickr

I am happy with the Seal Fin concept, and will continue to use the Seal Fins in my diving, along with my own Scoop Fins too. As some of you can tell, I have been intrigued with underwater swimming techniques for decades now, and the fins on our feet are only the beginning of my work.

John

[Aquala1]

Interesting watching the seals in motion. I’ve also found Bob’s fin creations interesting. I met Bob at DEMA back in 2001 and bought a signed set of Force Fin Pros from him. I then ran into him a few years later at a Historical Diving Society banquet and he’s a super nice guy. I was excited about the fins, because up until then I always just dove Scubapro Jetfins since 1984. The Force Fins were fine, and propelled well using a flutter kick, the only kick I had ever been shown other than the awkward dolphin kick.

Then in 2003 I discovered GUE and began their Fundamentals training. GUE teaches four core fin kicks, with the traditional flutter kick not really being one of them. They teach with a rigid rubber fin, like an SP Jetfin and after learning those kicks, I’ve never seen the need for any other type of fin. In fact, the Force Fin no longer worked for half of the kicks taught.

From what I’ve seen, most modern fin development tries to improve the efficiency and effectiveness of the traditional flutter kick, but I’ve found that the traditional flutter kick is not that great of a kick to begin with. Sure it has a place in a heavy current, but aside from that, a frog kick or a bent-knee flutter kick is a much better option. A frog kick or a bent-knee flutter doesn’t work that well with non-rigid rubber fins, and with kicks like a back-up kick or a helicopter turn, the non-rigid fins barely work at all.

[SeaRat]

Aug 23, 2022 19:54:34 GMT -8 Aquala1 said:

Interesting watching the seals in motion. I’ve also found Bob’s fin creations interesting. I met Bob at DEMA back in 2001 and bought a signed set of Force Fin Pros from him. I then ran into him a few years later at a Historical Diving Society banquet and he’s a super nice guy. I was excited about the fins, because up until then I always just dove Scubapro Jetfins since 1984. The Force Fins were fine, and propelled well using a flutter kick, the only kick I had ever been shown other than the awkward dolphin kick.

Then in 2003 I discovered GUE and began their Fundamentals training. GUE teaches four core fin kicks, with the traditional flutter kick not really being one of them. They teach with a rigid rubber fin, like an SP Jetfin and after learning those kicks, I’ve never seen the need for any other type of fin. In fact, the Force Fin no longer worked for half of the kicks taught.

From what I’ve seen, most modern fin development tries to improve the efficiency and effectiveness of the traditional flutter kick, but I’ve found that the traditional flutter kick is not that great of a kick to begin with. Sure it has a place in a heavy current, but aside from that, a frog kick or a bent-knee flutter kick is a much better option. A frog kick or a bent-knee flutter doesn’t work that well with non-rigid rubber fins, and with kicks like a back-up kick or a helicopter turn, the non-rigid fins barely work at all.

Ty,

I’ve tried most of the kicks, but mostly use in my diving the flutter kick and the dolphin kick (modified, with my forward unit). In my experience, the original Force Fins don’t work well with a “frog kick.” I put that in quotes because there are actually two ways to do a frog kick. The traditional breast stroke frog kick uses the bottom of the feet for the kick (without fins). This is how GUE teaches the kick, and it works well with the rubber fins like the Jet Fins. But the Force Fins give way when used in this manner, providing very little propulsion. But we also, in competitive swimming, learned the “whip kick” for breaststroke. This uses the top of the foot for the frog-style kick. The Force Fins work well for this “whip kick.” Now, the Seal Fins, with their duel blades, will work with the frog kick (I’ve tried it in the pool). I’ll also try it again tomorrow when I dive again.

While I haven’t tried it, the helicopter turn probably will work with the Seal Fins due again to their duel fin blades on each fin. This is a kick I’m not proficient in, as I really don’t need it in a river current. It is made for use in caves with very little space for maneuvering. (Most GUE kicks are made for cave diving, I think.)

By the way, my Scoop Fins do well with the frog kick too.

John

[SeaRat]

Ty and all,

I dove today (August 23, 2022) at Cook Park, on the Tualatin River. This dive was not deep, with a max depth probably just over 6 feet (or 2 meters). But it was interesting to me. First, let's talk about the Seal Fins I was wearing.
I
Seal Fins Performance

I used only the frog kick today, as visibility was about 3 feet (1 meter), with a bottom of algea and silt over the rock bottom. Here's what this dive site looks like:

IMG_3386 by John Ratliff, on Flickr

The Seal Fins, like I said above, has two blades on each fin, giving it a very good "bite" into the water with a frog kick. I used the bottom-of-the-foot type of frog kick, which is what I think GUE teaches (from my watching of cave divers). I got good forward motion against a slight current (maybe 0.5 mph). I wanted to use the frog kick as I was watching for very small mussels in the bottom, where I could view the bottom through the algea. So my conclusion is that these Seal Fins will work with the frog kick very well.

The Mussels

So what was I really looking for in relatively shallow water. I have canoed this area for several years with my wife, but have not dived it with scuba until today. I wanted to see whether in addition to the mussel shells I had seen and collected, I could fine live mussels. Well, the live mussels were all over the bottom. It is a great place for the mussels as they are well protected. Here's an example:

IMG_3405 by John Ratliff, on Flickr

At times I moved the algea away from the bottom to expose the actual bottom. Without removing it, this is what the bottom looks like in a lot of areas.

IMG_3385 by John Ratliff, on Flickr

But find a place without the algea, or move the algea away, and here is what I saw.

IMG_3380 by John Ratliff, on Flickr

With some patience, I could see both the incurrent and excurrent syphons for the mussels.

IMG_3395 by John Ratliff, on Flickr

After waiting, I finally got a really nice photo:

Version 2 by John Ratliff, on Flickr

I used my twin 45s (3000 psig tanks), with my Mossback Mk 3 double hose regulator, my SeawiscopeEY on my mask, and the Seal Fins. I had my float too, to ensure that no boats ran over me (but most watercraft were canoes and kayaks here). The double hose regulator allowed me to get my face very close to these mussels without disturbing them.

John

[SeaRat]

I had a funny little thing happen upon my exit yesterday. First, I took off my scuba and used my Aqueon for the first time in open water this season. Without scuba, the Aqueon actually did well propelling me through the water. Then I was getting out, and there was a fellow with his pickup down at the dock and he called out to me. I couldn't understand what he said, as I had my hood on over my ears. So I said, "Just a minute, I can't hear you." I then pulled my hood away from my ears, and he repeated his question.

"Navy or Marines?" he asked.

"Actually, U.S. Air Force Pararescue," I replied.

I then asked, "How did you know?"

He replied, "I saw how you dived."

It turned out he was also prior service, and said he was in the Marines Special Forces. He did guard duty, and went on to tell me he had been in combat. He said he had killed some intruders who were trying to steal equipment from their motor pool, or something like that. He tried to impress me by saying that you should "Take a head shot, because they're all wearing body armor."

At that point I started hauling my gear back to my SUV, and I'm thinking he's an imposter. He didn't give any unit out, said he couldn't talk about it (secret stuff, you know). So to me, his credibility was pretty well shot. But it makes an interesting little highlight of my dive yesterday.

John

[Aquala1]

Aug 23, 2022 21:14:35 GMT -8 SeaRat said:

Aug 23, 2022 19:54:34 GMT -8 Aquala1 said:

Interesting watching the seals in motion. I’ve also found Bob’s fin creations interesting. I met Bob at DEMA back in 2001 and bought a signed set of Force Fin Pros from him. I then ran into him a few years later at a Historical Diving Society banquet and he’s a super nice guy. I was excited about the fins, because up until then I always just dove Scubapro Jetfins since 1984. The Force Fins were fine, and propelled well using a flutter kick, the only kick I had ever been shown other than the awkward dolphin kick.

Then in 2003 I discovered GUE and began their Fundamentals training. GUE teaches four core fin kicks, with the traditional flutter kick not really being one of them. They teach with a rigid rubber fin, like an SP Jetfin and after learning those kicks, I’ve never seen the need for any other type of fin. In fact, the Force Fin no longer worked for half of the kicks taught.

From what I’ve seen, most modern fin development tries to improve the efficiency and effectiveness of the traditional flutter kick, but I’ve found that the traditional flutter kick is not that great of a kick to begin with. Sure it has a place in a heavy current, but aside from that, a frog kick or a bent-knee flutter kick is a much better option. A frog kick or a bent-knee flutter doesn’t work that well with non-rigid rubber fins, and with kicks like a back-up kick or a helicopter turn, the non-rigid fins barely work at all.

Ty,

I’ve tried most of the kicks, but mostly use in my diving the flutter kick and the dolphin kick (modified, with my forward unit). In my experience, the original Force Fins don’t work well with a “frog kick.” I put that in quotes because there are actually two ways to do a frog kick. The traditional breast stroke frog kick uses the bottom of the feet for the kick (without fins). This is how GUE teaches the kick, and it works well with the rubber fins like the Jet Fins. But the Force Fins give way when used in this manner, providing very little propulsion. But we also, in competitive swimming, learned the “whip kick” for breaststroke. This uses the top of the foot for the frog-style kick. The Force Fins work well for this “whip kick.” Now, the Seal Fins, with their duel blades, will work with the frog kick (I’ve tried it in the pool). I’ll also try it again tomorrow when I dive again.

While I haven’t tried it, the helicopter turn probably will work with the Seal Fins due again to their duel fin blades on each fin. This is a kick I’m not proficient in, as I really don’t need it in a river current. It is made for use in caves with very little space for maneuvering. (Most GUE kicks are made for cave diving, I think.)

By the way, my Scoop Fins do well with the frog kick too.

John

GUE began in the caves of Florida, but they soon found that what worked in tight, silty caves also worked inside a rust encrusted wreck, as well as in any delicate environment like a coral reef. What I especially like about the GUE fin maneuvers, like the helicopter turn and the back-up kick, is they eliminate any use of the hands. All too often I see divers fanning their hands to make tight turns or to back up off of an object. With these techniques you don’t have to do that. It’s complete finesse and control.

[SeaRat]

Here’s a YouTube demo of these strokes and turns;



I’ve been diving a very long time, and in most of the places I dive, these strokes and turns look very inefficient. The main objective is to keep from stirring up the bottom, or injuring coral. But this comes at a sacrifice of actual movement forward. These are specialty strokes, for very specific environments. But what I see is that these are being taught now as the only way to swim underwater.

Much of my research is to make foreword motion underwater as streamlined and powerful as possible. I was at one time Finswimming Director for the Underwater Society of America, which is a competitive underwater swimming sport to get as streamlined and fast as possible. This is the exact reverse of what is being taught by GUE.



As you can see, there is a vast difference in the two techniques, as they have different objectives.

John

[SeaRat]

Okay, I may have been a bit hard on Ty above, but the demo I found on YouTube looks to only be about 25 feet of travel distance, and it takes a long time to get from one stake to another. My emphasis has been on efficiency in the water, and the GUE methods are emphasizing not efficient movement, but non-disturbance movements. In the rivers I dive in regularly, these motions regular swimming kick motions are not a problem, and we have fish such as salmon coming up and making "redds" in the river bottom with their fins. These are depressions into which they deposit their eggs. I've also documented lampreys moving gravel around to cover their eggs. But I could not even hope to do some of this kind of diving using the frog kick.

Now, the Seal Fins I've made actually do give a good push on the frog kick. Unlike the Force Fins, which have just one blade which give way on the up-stroke, the Seal Fins work on both the up-stroke and down-stroke of the crawl kick, or the dolphin kick for that matter. They also have enough blade area to do a very good frog kick. I haven't tried the helicopter turn, as I'm always diving solo with a line, and doing that would probably entangle my legs in my float's line (which happens regularly anyway).

Seal Fins at High Rocks by John Ratliff, on Flickr
This photo is off a GoPro video I'm putting together about the Seal Fins.

I've now used these fins both at High Rocks on the Clackamas River, and at Cook Park on the Tualatin River. I used exclusively the frog kick at Cook Park, as the bottom was not like the bottom at High Rocks, but had a lot of algea and I was trying to document the mussels there.

So at this point I've pretty well established that the Seal Fin concept is a valid one, and that they will work on a number of different kicks.

I'd like to share a post from ScubaBoard that I made, answering a question one of the divers had about swimming up excessive weight:

Boarderguy:
I dive wet with both steel and AL and adjust my lead based on which tank I grab. I'm still trying to figure out how a diver could not swim up their full kit when wet... total bc failure = ditch some weight and start kicking up. The majority of us could tread water in just swim trunks (with effort) with 10-15 lbs, why couldn't that same majority kick up 20-25 lb with fins on? 35-40 would suck but is doable especially as your wetsuit regains buoyancy. Drop one pocket and start working your way up to avoid an uncontrolled ascent. Drop the other once on the surface of you still are not floaty. Factoring in a tank's buoyancy is nice but unnecessary. If rather have the extra air and better trim from my steels than the floaty AL 80s.

I’ve just discovered that many divers are now being taught only the frog kick and inefficient elevated flutter Kick by GUE and other instructors. Because of this, it is entirely possible that a new diver could not ”kick up” a 10 pound load because they don’t have the kicking skills to do that. It seems to me to be an instructional problem that divers are not now being taught powerful kicks.

SeaRat
scubaboard.com/community/threads/al-tanks-and-diving-wet.624369/page-6#post-9767954

Boarderguy gave me a "Bullseye" for this comment.

John

PS, note that this was the dive where I evaluated the new silicone diaphragms for the Dacor R-4 regulator too.

[Aquala1]

John, no problem with your posts. I was traveling yesterday so I didn’t have a lot of time to respond.

Ok, the video of the frog kicking diver is a demo. video, so he’s likely going slow so the viewer can see what he’s doing. However I doubt he’s actually GUE trained since he’s using long bladed freediving fins. That might also be the reason for his slow movement. Also, the competitive mermaid fin racing is pretty cool, but I don’t see how it correlates to what we do as underwater adventurers and explorers.

In all honesty and with the utmost respect, I say this…most of your understanding of GUE’s teachings and techniques are completely inaccurate. It’s difficult to gain understanding from Scubaboard discussions and Youtube videos. If you ever get the chance, take a GUE Fundamentals class or dive with some GUE trained divers. I really think you would enjoy it.

[SeaRat]

Aug 27, 2022 13:11:03 GMT -8 Aquala1 said:

John, no problem with your posts. I was traveling yesterday so I didn’t have a lot of time to respond.

Ok, the video of the frog kicking diver is a demo. video, so he’s likely going slow so the viewer can see what he’s doing. However I doubt he’s actually GUE trained since he’s using long bladed freediving fins. That might also be the reason for his slow movement. Also, the competitive mermaid fin racing is pretty cool, but I don’t see how it correlates to what we do as underwater adventurers and explorers.

In all honesty and with the utmost respect, I say this…most of your understanding of GUE’s teachings and techniques are completely inaccurate. It’s difficult to gain understanding from Scubaboard discussions and Youtube videos. If you ever get the chance, take a GUE Fundamentals class or dive with some GUE trained divers. I really think you would enjoy it.

I’d like to do that, Ty. Do you think they’d let me dive with them with the Seal Fins and my DiR-configured regulator?

IMG_1829 by John Ratliff, on Flickr

IMG_1824 by John Ratliff, on Flickr

This regulator has been proven on the Hannes Keller dive to 1,000 feet.

divermag.com/hannes-keller-diving-pioneer-and-renaissance-man/

John

PS, maybe I should have used this video.


It still looks inefficient to me. But, I did get some fairly decent propulsion out of my Seal Fins using the frog kick.

[Aquala1]

As long as you have a donatable air source, a GUE diver will let you dive with whatever you want. If you’re taking a class, that’s a different issue.

The system you posted would work with a little modification. Your primary 2nd stage reg and your secondary 2nd stage reg, need to run off of the right side of the body. It looks like your set up would, but just want to clarify.

Your primary needs to be on a 7’ long hose and your secondary needs to be on a 24” hose (approx). Maybe yours is, but it’s hard to tell from the photo. Your back-up second stage needs to be on a bungee necklace and you need a bolt snap on your primary reg. The power inflator hose and the SPG route on the left side of the body, and the SPG needs to have a bolt snap attached instead of the plastic strap. All of this works with a backplate, harness and buoyancy wing with left and right chest D-rings, and a D-ring on the left waist strap.

The Seal fins, though unconventional, would be ok if you could perform the necessary kicks. You’ve proven they work with a frog, and bent knee flutter. I’m not sure if they would work with a helicopter turn, but I feel they would fail with a back-up kick.

When Bob designed the Force Fin, the thought behind the fin was that it gave the diver a rest in the upstroke, which was the weakest and most cramp prone part of the diver’s kick. A rest that a straight bladed fin, like a Jetfin didn’t provide. When you put the same blade on the back of the fin that’s on the front, it prevents that resting stroke on the upstroke. So basically what you have (from a performance perspective) is a straight blade fin like a Jetfin, but one that likely won’t helicopter turn and likely won’t back up. If you can make them helicopter and back up, then they would be fine.