Underwater Swimming Techniques--Vintage versus Brand New

[SeaRat]

As some of you may know, I have been experimenting with swim fin design and better underwater swimming techniques for decades. I started this study and modifying of swim fins while still in the U.S. Air Force in Okinawa. I felt that the fin designs were not optimal, and eventually developed my "scoop fin" design. But, it was already patented, so there was no potential for a patent.

I also in the early 1980s developed a streamlined BCD I call the Para-Sea BC. This is a front-mount BC that incorporated aspects of a parachute harness, with a unique four-point scuba harness attachment. I did patent this device, but no one would buy it. So I pretty much have had it with patents.

ECCBB516-C55C-46E0-9B6D-4658B7792545 by John Ratliff, on Flickr
Here you can see my Scoop Fins along with the Aqueon that I have experimented with over the years.

Fin Vector Analysis by John Ratliff, on Flickr
Here is my work on the Scoop Fin concept, from the 1980s.

SeaFinMods1 by John Ratliff, on Flickr
Here's an example of a fin design that I modified, by adding the springs, and also a wooden "wing" to this design. These fins were terrible until I put the springs in, as they would simply reverse and hit a stop, putting a lot of stress on my foot.

Seal Fins at High Rocks by John Ratliff, on Flickr
I even recently took the Force Fin, and made a "Seal Fin" out of it by placing another set of blades on the back of the Force Fin. I did not like the way the original Force Fin design had no thrust on the "up stroke."

IMG_0495 by John Ratliff, on Flickr
The "Seal Fin." Can you explain why I named it such?

Fara-Fin Mod-1 by John Ratliff, on Flickr
I also modified the Fara-Fin so that they actually worked, and worked quite well by increasing the angle of the leg support.

My work in recent decades has to do with what I called the "Sea Turtle-Dolphin" underwater swimming technique. Here's an example of it in the pool:

Sea Turtle-Dolphin Swimming by John Ratliff, on Flickr
This is a very efficient underwater swimming technique, incorporating a "Forward Unit" (the "Hammerhead" or "Sea Turtle" portion) with the dolphin kick, to produce outstanding inderwater swimming. In doing so, it is much more efficient and streamlined than modern divers.

I recently (like yesterday) tuned in to NPR's Science Friday, where the scientist, Dr. Megan Leftwich, professor of Mechanical and Aerospace Engineering at The George Washington University in Washington, DC, was discussing her work with the fluid mechanics of sea lions:

www.sciencefriday.com/segments/sea-lion-fluid-dynamics/

I've done some research on her, and her work, and will be contacting her to discuss the "Sea Turtle-Dolphin" style of swimming to see if she is interested in pursueing it is well as use of her studies for underwater vehicles.

John

[cg43]

Hello John

Interesting thread you bring up !

Since over 10 jears I partly use the dolphin tecnique during my apnea training for swiming lanes
in  the pool . The longer I do this , the more I like this technique .

Apnea diver's (with monofin) use the dolphin technique with great succes , therefore it must be 
very efficient . 
However dolphin technique with scuba is a littel bit different because you can't bend your body
as free as an apnea diver . But John would not be John if he don't found solution's for that problem .

!.) You use belts that allow more freedom for bending the body .
2.) You use the hammerhead to produce a counterforce against the force from kicking
      with both fin's  simultanious .

Will the dolpin technique  using scuba work withhout hammerhead ?
I don't know . For apnea dolphin I bending my body and strech out my arms as long as possibel 
to use my hands as "hammerheads" . This works great . 

Greetings   Rainer

[SeaRat]

Mar 24, 2024 7:54:35 GMT -8 cg43 said:

Hello John

Interesting thread you bring up !

Since over 10 jears I partly use the dolphin tecnique during my apnea training for swiming lanes
in  the pool . The longer I do this , the more I like this technique .

Apnea diver's (with monofin) use the dolphin technique with great succes , therefore it must be 
very efficient . 
However dolphin technique with scuba is a littel bit different because you can't bend your body
as free as an apnea diver . But John would not be John if he don't found solution's for that problem .

!.) You use belts that allow more freedom for bending the body .
2.) You use the hammerhead to produce a counterforce against the force from kicking
      with both fin's  simultanious .

Will the dolpin technique  using scuba work withhout hammerhead ?
I don't know . For apnea dolphin I bending my body and strech out my arms as long as possibel 
to use my hands as "hammerheads" . This works great . 

Greetings   Rainer

Hi Rainer,

The dolphin technique works well with vintage scuba harnesses, but not with the BCD/Scuba units of today. The reason is what you describe. The new BCD styles are much more confining than the vintage scuba harness.

Now, concerning the Hamerhead Unit, this not only produces a counterforce, but also provides on its own some propulsive fluid dynamics. This effect, plus the streamlining, work to increase the efficiency of the diver in the water. I have proven this in one dive last year where I came upon two Sheriff's deputies divers, overtook them easily and continued on my dive.

John

[cg43]

Hi John

Is there any mechanic or do You only hold the Hammerhead in your hands ?
I can not see this on the photo .
Many modern BCD are straitjackets .
They are not steramlined , and more worst they restrict the movement of your bodv
and restrict the breathing with the belly and the lower rips .
Most modern divers don't know it better , therefore a lot of this devices are sold .

Greetings   Rainer

[SeaRat]

Rainer,

You can get a good idea from this YouTube video I made several years ago.


Note that I am using Duck Feet fins for this demonstration. I have four pair, two full-foot and two the original design with the heel strap (one set is like it was brand new).

The Hammerhead unit features freely rotating wings on each side, which allows the unit to maneuver through turns as well as straight ahead.

John

[cg43]

Hi John

The video is very informative .

Today I made my first exercise with a very simple Hammerhead version swimming lanes apnea in a pool .
I used a wooden board 90 cm x 9 cm with rounded edges . A well shaped profie will be better ,
but for the first try ok .
The board produces thrust and I can swim only by using the board .
Unfortunately this works better with highter speeds than I like . 
A very thick profil may be better for low speed .
However I found it cumbersome to use the board .

Greetings   Rainer

[SeaRat]

Mar 26, 2024 14:39:43 GMT -8 cg43 said:

Hi John

The video is very informative .

Today I made my first exercise with a very simple Hammerhead version swimming lanes apnea in a pool .
I used a wooden board 90 cm x 9 cm with rounded edges . A well shaped profie will be better ,
but for the first try ok .
The board produces thrust and I can swim only by using the board .
Unfortunately this works better with highter speeds than I like . 
A very thick profil may be better for low speed .
However I found it cumbersome to use the board .

Greetings   Rainer

Rainer,

I have now made four versions of this Hammerhead unit. This one was made with two kayak paddles that I found in the Clackamas River (kayakers tend to loose their paddles fairly ofter in the rapids when they get dumped).

IMG_0006 by John Ratliff, on Flickr
Note the handles made out of an old aluminum bicycle drop handle bars. Note also that the two sides can be independently rotated; this is cirtical to the functioning of the Hammerhead Unit, and makes them much more manageable. I used flexible flat pieces to make more surface area than the paddles gave, making it much better.

If the board you are using is one solid board, it needs to be cut in two, and holes drilled in the end for a solid metal rod. Then put handles on the separate boards.

The reason I'm not showing some of the older ones I've made are two-fold:
--The first one was made from the propulsive wings of my Aqueon. The Aqueon is now back in its original condition.
--I've lost two of these Hammerhead Units on dives, when I forgot te pack them into my car (Yes, I'm getting older).

John

[SeaRat]

A while back I took my Spoiler fins, which I distinctly disligked because of their rigidity, and modified them to a scoop fin design.

IMG_1108 by John Ratliff, on Flickr
Because of the double blade, it was very difficult to get this fin to bend. That negated any effect of the "spoiler" blade with the water going through the entire blade.

IMG_1109 by John Ratliff, on Flickr
So I cut apart the blade, and inserted foam neoprene in the middle of the ribs. This allowed the fins to bend, and the scoop action increased the efficiency of the blade.

_MG_5877 by John Ratliff, on Flickr
Here are the cuts I made. I actually took these fins in this condition into the pool, to see whether the cuts made them into a sort of split fin. They did, and were more effective than the flat, sandwiched blades, but not as good as the scoop modification I did later.

_MG_5878 by John Ratliff, on Flickr
Here's what the modification looked like before riviting.

_MG_5889 by John Ratliff, on Flickr
Tthe final product/modification.

_MG_5888 by John Ratliff, on Flickr
Different view of the final product.

While the modification was successful, I still don't really like these fins as the foot pocket is uncomfortable. I put strings on one of the fins, and somewhere have a video of the use in the water. I'll look to see if I still have it.

John