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Whale Tail Shaped Monofins?

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.

MBanks

Martin
Feb 7, 2006
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I have been thinking about this, and I can't figure it out; why are monofins not shaped in the same way as a whale, the most perfectly evolved freedivers?
 
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I've seen pictures of earlier monofins that had more of a whale or a dolphin shaped tail.

One thing to note though it that whales, dolphins etc can control their tail by stiffening it or relaxing it depending on what they want to do at the time. Now if you could do that with a monofin then you'd have some leeway in the design...

Cheers,
Ben
 
hi Mbanks

A friend of mine manufactured a whale tail shaped monofin - didn't turn out very auspicious though in my opinion. I will post pics/videos ASAP.

yours
Pat
 
I would say that a rectangle shaped monofin would alter the hydrodynamics and effect the vortex's left behind by a freediver using the monofin.

The fact that whales can stiffen ad soften thier tails could be a good reason for not making monfins shaped that way. However I feel that as nature has spent millions of years evolving a tail with a shorter central length distance than the edges, then it is likely it is due to maximising effort and hydrodynamics, as well as many other biological reasons. I was curious if many people or companies had experimented with this shape and what they had found from it. It seems to be a subject that is hardly touched on, but to me one that would be obvious for discussion.

I look forward to seeing your friends pictures and videos....and I'm already thinking of ways a freediver can stiffen or soften the properties of a monofin

Martin
 
If you look inside a mammal's tail you would see most of the equivalent bones we have in our legs and feet, starting below the hip.
Fish and mammals with tails generate most of their propulsion from vortexes generated by their bodies, not from their tails. The tails are the finishing touch in the movement, not the penultimate manouever. Look at tuna for example- they can swim incredibly fast, and then look at the relative surface area of the tail: minimal, if not ridiculously small compared to the power created. This reminds me of the 'bees cannot fly" mathematics of aerodynamics. There should have been a "fish can't swim" equivalent!
We would be better off with no legs and a monofin attached below the hip, if we had the hydrodynamics right.
Peace,
Erik Y.
 
I understand that the tail/fin of a whale or fish is a large part of the propulsion whilst swimming, but surely without the tail/fin the vortex's are serverly minimised, reducing propulsion. This is shown in Laursen, Riche, Lernosse's paper on optimising monofins for propulsion?

www.emse.fr/~leriche/mao04_monofin_final.pdf

They have concluded a flat ended monofin to be optimal for their theoretical 2D liquid.

How and why do whales and dolphins control their tails by stiffening it or relxing it? Is it a general stiffness or do they strengthen parts of it for manovers? There must be ways of reproducing this in a monofin worn by a freediver.

I know this thread could lead into quite a scientific discussion, but that's what I'm hoping for, can anyone help? I'm really curious as to what steps would need to be taken to create a monofin that mimics the whales. I have started to look into the subject but I don't have the knowledge about freediving fins and the choice for their shape, over a whales.

As for a rectangle shaped monofin, I'm sure the hyrodynamics would be ruined, right at the front!

It has been proved time and time again that nature's designs are better, but with the combination of nature's designs and technological advancement man can create tools to improve our abilities for progress in the chosen area of study. So why not monofins?

thanks!
 
Yes, that's my opinion, too. I also started a similar thread about the [ame="http://forums.deeperblue.net/showthread.php?t=64238"]propeller / splitfin concept at monofins[/ame].

Unfortunately, the market for both freediving bifins and monofins is very small, and companies producing them do not have sufficient means for exhaustive 3D computer simulations, hydrodynamic tests in chambers, or comparative tests with representative number of competitors that would help with the development of new concepts, more complex shapes, and variable blade stiffness distribution (not only in lenght as at current monofins) helping to better control turbulations. Hopefully, hydrodynamic 3D computer simulations become soon easier accessible even for some of the fin manufacturers and help them to find more efficient fin geometry.
 
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I don't see the big deal with a rectangular shaped monofin blade.

We certainly don't design plane wings to look like a bird. If you look at an ultralight, like the Gossomar Challenger, it certainly looks like nothing you see in nature, but it worked to get across the English Channel by human power alone. Scubapro even had a fin out at one time based on this idea, the Seawing, but they also came out with crap, like the spilt fin, so that may not be the best example.:head

What does seem too stickout in many "advanced" monofins is the leading edge "wing" design. Since this has been brought to the forefront by C4's latest design, the Mustang, I don't see why it wouldn't work in a wider blade- they HAVE done their homework more so than any other fin company out there in these matters. All that needs to be done is widen one of their Mustang blades to accomodate two footpockets and your in business. Length, and stiffenss, could be altered on the needs of the diver's weight and ability.

Jon
 
trux, although it becomes quicker for the development of the monofin with 3D computer simulations, hydrodynamic tests, and multiple tests with professional freedivers, I still believe it can be achieved by anyone with the determination, it just takes time, effort. That's my initial reason for posting, as I plan to make a monofin, and orginally I was going to make a "regular" monofin, but I saw opportunity to possibly improve on the design, and the whale tail shape was the first question that I thouhght of.

Would the area near the footpockets on a rectangle monofin blade not bend and fold creating drag? If not I would be interested to see how it compares.

Are plane wings not designed to create lift as a birds, by the movement of airflow over the front of the wing? Early attempts at flying machines would have been made from wood, making the wings heavy, unlike the empty bones of birds, but as technolgy allows hollow wings to be built it occurs in aeroplanes? I'm not talking about copying nature exactly, that wouldn't work, as each design has been evolved over millions of years for a specific perpose, but utilising it's designs and adapting them to suit our needs using new technology.

I Thought the first thing to be looked into in monofin design would be the shape, and I thought a post explaing why the whale tail shape is worse would appear

I would still like to know how whales a dolphins utilise stiffening and softening their tails. Is this for speed and effeciency?

What are other apects of improving the monofin have people had?
I like that guys dolphin tail! although I think some kind of quick escape mechanism from the wetsuit and body shells might be needed!:crutch

 
"All that needs to be done is widen one of their Mustang blades to accomodate two footpockets and your in business. Length, and stiffenss, could be altered on the needs of the diver's weight and ability."

Maybe you could test this idea by using Mustangs and strapping your ankles together. After watching a 75 meter dive using C4-40s and a dolphin kick, that might be a very good setup for most of us. There must be hundreds of divers that have tried to make a monofin. Three of them that I talked to spent a lot of time and money for zero results. They did teach me a few things.
Plan on building at least three models. Maybe try to copy a good design first, before you try to improve it. Don't think aerofoil and hydro foil, build a propeller, a very slow speed propeller.
I still think that the design should; have as little surface as possible ahead of the bending point (all that does is create negative thrust and drag) and be as thin as possible (shapes don't produce lift in non compressible water).
Aloha
Bill
 
After watching a 75 meter dive using C4-40s and a dolphin kick, that might be a very good setup for most of us.

Bill, I remember Eric posting somthing about the 40's being better at dolphin kicking than some monofins when coming up from depth.

BTW: Are you dolphin kicking with you 80's, or flutter kicking, on you deep dives? Have decided to make the switch to a mono yet?

Jon
 
I don't plan to spen much money at all, I dont have much! I usually get what I need via recycing old things which people don't want, it has suited me well so far However I don't suppose I will come accross and C4s soon!

So far I plan on using the profile mentioned in the academic paper I found online. and I have a simple idea for a stiffening and softening action if I can find out whether it'll benifit it. and I think I'll use the whale tail shape, but maybe make the length in the centre longer than a whales dues to the narrower profile of humans. I have a few people helping me so I'm not alone

If anyone finds, or comes accross any materials that they think might be handy, (or where I might find them on other products ) then let me know!

Martin
 
Has anyone out there ordered a monofin with one
or more these characteristics:

* wider (~80cm)
* shorter (~60cm)

I see that LeaderFins "Free Flyer" allows you to choose
the width and length of the blade.
 
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Re: The paper on Monofin Optimization (by Leursen, LeRiche and Lemosse)

Though Leursen, LeRiche and Lemosse spent quite some time studying monofin optimization (an endeavor for which I hold much respect and appreciation), I'm not entirely convinced of the the approach.

Translating two dimensional fluid dynamic models of a fin into three dimensions, then using an algorithm to calculate efficiency does not seem to take into account the swimmer's combined body/fin natural flowing movement through water. The previously mentioned model of swimming tuna is a good example. The paper itself points this out. It assumes the "swimmer is represented by linear articulated segments whose kinematics is identified from experimental swimmer data and imposed."

Even though the paper has well reasoned math and a thoughtful approach to it, please don't be entirely convinced that it actually models the motion of a swimmer using a flat trailing edged monofin.

There are other qualities in a monofin blade we value too - like ability to track straight. Fin design (like the fluke on a whale) though it very well may decrease propulsion efficiency, seems like it would decrease stress on muscles of the feet/ankles, and increase an overall feeling of stability through the water.

I'd ask a whale, but they seem too busy enjoying the water to surf web forums.
 
Pelcami

Not to sounds stupid but most of the Characteristics you describe for furthr testing are stanfard fitment on the higher end models from the leading manufacturers.

My Tritent fin has the following features you mention:

-Fibreglass blade
- Leading shoulder
-Angled footpockets

and as mentioned above different laminations in both the left to right plain and the front to back plain to control blade flex.

It Is a VERY good fin!

wider and shorter is interesting and i think is being very well tested in the Lunocet fin eing designed (lots of info on this forum).

As for controlling and changing the stiffness goes it would be interesting to see how you go about this as with dolphins the use of movable joints and bones along with the controlling muscles and tendents would be very difficult to replicate and even more so to control... intersting thought though look forward to seeing the result.

DD
 
Hey DD,

After reading your post, I edited mine. Wasn't thinking my ideas through there, and hadn't read enough monofin posts.

On the verge of buying a monofin here myself. Has anyone out there explored a LeaderFins Free Flyer with the following specs:

soft blade
span: 80cm
chord: ~60cm
 
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Hi Freedivers,
Greetings from Specialfins.com
During of August, all your ideas are welcome and Specialfins will produce based of different ideas few prototyps of monofins.
We will send them for testing and hopefully freedivers forward them to another freedivers.
Weedback information will be welcome!

Greetings,
Jyri
www.specialfins.com
 
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