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Fin swimming

Fin swimming the fastest way of swimming. This fin was developed as an experiment.

#@hanno; Jun 1999 Back »

Fin swimming

Dolphin man

From the first time I used a monofin I wanted to make my own. Why not experiment with making a mamal shaped fin? Look at the drawing, the pictures and the movies below. When I am in the pool I really look like a too large marine mamal ;-))).
You can feel your skin flap under te resistance from the water

I know the fin looks too large, but it does not feel like that. Making the fin was difficult as the flexibility plays an all important role in how the fin feels, when swimming. This one feels like it requires less effort to attain the same speed as with the more normal monofin shapes.

Design objectives

My aim was twofold,
firstly see if a high aspect ratio fin would work better than the normal type and secondly use the beautiful dolpin whale fin shape.

What I found is that the swimming mechanism, is different from what dolphins and whales can do. The main reason for that is the amplitude you can make with your feet. It is much less than that of the aquatic mamals.
Also the fin will have to be very supple to flex when swimming, too stiff a fin does not work at all.
This flexing requirement also means that the fin is very thin and has no profile section shape, as I would like to have.

I have been experimenting with a extremely high aspect ratio wing. like the trampofoil main fin, which was connected to my feet via a kind of leg extensions. The wing had a good profiel section and was hinged and place so that it "chose" its angle af attack.

I have stopped this experiment as it required quite some engineering. I still want to try and optimise it sometime. One problem to overcome will be excentric loading of the fin, due to whatever disturbance there is in the water and loss of control, as your feet (legs) have limited capability to counteract roll.

What have you learned about the stiffness of your fin?
This is critical, but when it is too stiff, gradual sanding will help this.
Do you make them by hand yourself?
Do you use a mold or jig of some sort?
No moulding, but I use a template, for shape.
What materials (i.e., fiberglass cloth and resin) do you use?
Polyester, glass and carbon fibre.
Is there another material you'd prefer to use?
Yes I want to experiment with epoxies.
Have you allowed other finswimmers to use your fin, and, if so, what do they think about your invention?
Sure, as I now swim daily, many people have used it. There is a significant group that find it difficult to master, but all like it very much, When my sons were 11 and 9 years they used the fins without a problem.
Are there any problems with the fin?
There are two problems with te fin:

  • The force on your feet can be pretty large with some, sometimes resulting in some calouses on my feet ;-)).
  • The polyester in the fin flexes quite a bit and this results in some cracks after about one seasons use. maybe a more industrial method of manufacturing and the use of different materials might solve this problem. for the use we make of the fins thats is not neccessary. In the image below the problem area's are indicated.

    Earlier models

    As with all new ideas it took quite some experimenting before I had a well working fin. Some of the earlier fins can be seen in beow. Fins too wide to control, fins too flexible or the stiff to be able to use.

    The most excotic fin I tried and still am interested in pursuing a little further I have no picture of but look at the drawing an you can probably understand what I try to do ....

    Dolphin man nacelle


    My dolphinman idea is based on a powerful monofin. These fins allow you to very efficiently propel yourself through the water. When you swim at high speed with the fin you can really feel the resistance of the water, the force is comparable with airresistance of app. 300km/h!!! because the density of water is that much larger. Imagine the result of fairing your body hydrodynamically!! The effect will be very large, much larger than the shark skin swimsuits used by worldclass swimmers as the monofin speed is that much higher. The idea of the dolphin suit/fairing looks apealing.

    Streamlined wetsuit.

     Of course we should have a streamlined body also. I am Thinking of using a combination of neoprene and rubber to connect to the dolphin head. Some form of scuba breathing gear will have to be incorporated in the navelle.

    Streamlined body wetsuit.

    This suit of lightweight carbon fibre segments connected bij neoprene, pares flexibility with streamlining. The major factor limiting speed is resistance and anly by further streamling we can expect better results.

    More Complicated version, impractical??


    A more complicated version of the dolphinman suit. Swimming the monofin it feels like I have more power available in my legs than I can get into the water. The fins will not absorb what I have. Maybe lengthening the stroke of the fin will solve this???

    Dave Hoffman's interpretation.

    Dave Hoffman sent me his idea's in this form, looks great and practical doesn't it.

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