C4 Monofin!

[Fondueset]

'opposed to a monofin' - LOL I get an image of a guy with shaved head and speedo - arms crossed and not looking at a monofin stacked in the corner.

What C4 seems to be showing is a valuation of feedback over PR. It seems like they are really sincere about product development.

[trux]

OK, since we discussed diverse new monofin concepts here, including the Lunocet, I should also mention the new monofin developed by the Greek company the Trygons of Alex Sarasitis. From the picture it is not quite clear how it works, but I suspect it may be close to the idea Dave Mullins mentioned above.

More details at Freedive Central and on Trigon's website.

EDIT: I've re-read the article, and the fin is to be only used to propulse the human powered submarine - so it is not a monofin like the Lunocet, or the C4 monofin discussed in this thread.

[jome]

Trux: I intrepret this following quote as them developing also some sort of monofin? Of course there is no telling what is shown in that picture But I think they definitely are working on a new type of fin...?

The submarines will be designed and built by project Engineer Alex Sarasitis and will utilise a hydrofoil tail fin attached to the pilots legs for propulsion. The foil angle will change automatically producing an 'automatic transmission' effect making it the most efficient way of swimming. This new fin technology will be used by Herbert Nitsch, "The Flying Fish", during a Constant Weights World Record attempt in 2008. Alex's designs will be based on the motion and shape of fast swimming fishes such as tuna and mako sharks, giving them the fastest form possible. The “dry” submarines will be built from carbon fibres, giving rise to a new species of fish: the Carbon Fin Tuna.

[H.Balázs]

Hello,

I found this short video about C4 monofin:

YouTube - Monopinna prototipo C4

It does not look so effective...

Balázs

[Kars]

Jep, this design does not appear effective to me.
It looks too soft, not stable, appart from the diver who does not have a good technique and apparently is not that frilled about what he's swimming with. - I would expect some more serious lapswimming and better cameraposition if this would be a serious project.
My suspicions are confirmed with this video.

C4 has still a lot to do.

Thanks for the movie Balazs!

Now I need to refresh the 'Lunocet' thread window

Love, Courage and water,

Kars

[Fondueset]

Kars, The lunocet looks like it would be at its best for very fast swimming - of course I have not tried it - but I would like to hear a review from someone who has a lot of experience. I am not sure of the logic of basing a fin for humans on the fast swimming fishes - at least for freediving.

The C4 looks mono resembles the way some fish with sort of eel like swim patterns swim, also it appears to fold sort of chaotically. Good for covering small distances with lots of energy expenditure. I am sure they will re-work it.

[HJ]

Originally Posted by trux

... Me too, I believe that the current monofins are very far in efficiency from what they could be. However, the hydrodynamics is little bit more complicated, so just having a fin with ideal angle of attack is not all. There are several aspects in the flow, not only the angle of attack. It is quite complex, so I would no reject long fins completely. They may not be ideal for speed swimming, but may offer some advantages for slow swimmers. The long fin (if correctly designed) allows for more relaxed, steady / continuous kick with little turbulences. At the kick the pushing edge is only part of the time in the optimal attack angle - there are rather big "dead" motions bringing only little propulsion if you have a type of fin you described. In contrary, the long fin (together with your body), moves in a sinusoid, and propulses you smoother, and possibly more efficiently - there are really far too many factors involved to tell it without testing that long monofins are not well suited for freediving. In animal world you can finally also find both wide short and narrow long fins, and they seem to have withstand millions of years of evolution, so both probably have some advantage. ...

Hi Guys... enjoying this thread. I also think it depends on the purpose of the fin. If it is for max thrust and speed, then a lunate-type fin (high aspect ratio) would seem the way to go. However, a lunate fin may also prove best for max efficiency or low "Cost of Transport" (COT). I'm still reading the Dr. Fish PDF (linked elsewhere) and am coming across all kinds of fascinating research on this. For example, under a section on Propulsive Efficiency, Dr. Fish (his real name!) says: "propulsive efficiency, N, is defined as the ratio of the mean thrust power required to overcome the drag on the animal divided by the mean rate at which the animal is doing work against the surrounding water [ref]. Efficient thrust production requires high lift production while minimizing energy loss into the wake. [ref] ...

Then a little later: "The high efficiencies asociated with swimming by cetaceans [whales, dolphins] are dependent on a fluke [tail fin] design that enhances high thrust with reduced drag and on fluke oscillations that maintain continuos thrust production [not really possible by humans in my view]. The aspect ratio is the most important morphological parameter [ref]. High aspect ratio reduces drag while maximizing thrust [ref]. The fin whale Balaeonoptera physalus with 6.1 aspect ratio flukes has a higher maximum N (0.96) than the beluga whale and white-sides dolphin with aspect ratios of 3.3 and 2.7, respectively [ref]. ... "

He goes on and on talking about Metabolic Efficiencies, minimum Cost of Transport, and on and on and on. (FYI: did you know that the maintenance costs of dolphins is 57% of the active metabolic rate? Bet you didn't.)

Anyway, that C4 prototype looks kinda horrible to me.

HJ