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Fish scales reduce friction drag by 25%

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Created by colas Two weeks ago, 8 Oct 2020
colas
4001 posts
8 Oct 2020 4:42PM
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I guess it is time to save to skins of the fish you eat to glue them on your boards and foils :-)

"Using the specially equipped laminar water tunnel at the University of Stuttgart in Germany, Professor Bruecker and Professor Rist (University of Stuttgart) have tested the hypothesis of a transition (drag) delay by experimenting with a smooth flat plate and a flat plate covered with biomimetic fish scale arrays."

phys.org/news/2020-10-aerodynamicists-reveal-link-fish-scales.html

beefarmer
WA, 283 posts
8 Oct 2020 8:05PM
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Who wouldve thought, all the billions of fish in the ocean have evolved to suit their environment.

Sonds awsome in regards to board skin design. But its gonna be a bitch to repair a ding ;)

gregjet
QLD, 34 posts
9 Oct 2020 8:47AM
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Select to expand quote
beefarmer said..
Who wouldve thought, all the billions of fish in the ocean have evolved to suit their environment.

Sonds awsome in regards to board skin design. But its gonna be a bitch to repair a ding ;)


Actually depending on how they develop a "fish scale" bottom finish, it could be easier to repair, perhaps?

bobajob
QLD, 1434 posts
9 Oct 2020 3:35PM
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Don't land on it against the grain, might be a bit like a grater!

Chris_M
1976 posts
11 Oct 2020 3:23PM
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If that works, then the next logical step would surely be:





LeeD
1780 posts
12 Oct 2020 1:44AM
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But can your fish scale bottom finish secret the oil that a fish does?

LucBenac
373 posts
12 Oct 2020 3:51AM
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Select to expand quote
LeeD said..
But can your fish scale bottom finish secret the oil that a fish does?


Just start your paddle close to a marina first.....

colas
4001 posts
12 Oct 2020 1:20PM
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Select to expand quote
LeeD said..
But can your fish scale bottom finish secret the oil that a fish does?


The tests showing 25% drag reduction were done with "biomimetic fish scale arrays.", so not even with living skin wit mucus and (possibly) micro-movements like dolphins skin do.

515
527 posts
12 Oct 2020 3:17PM
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Hey Colas
From your windsurfing days did you ever see Angulo boards in the early 90's with "Phasers"?
They were a series of shallow hemispheres in the bottom of their boards.
From memory about 6 between the front and back foot straps.
They wanted to achieve a similar effect to the dimples on a golf ball.

nmpg
7 posts
12 Oct 2020 10:08PM
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This local shaper has something called Flowtech, that aims at reducing drag.

www.xhapeland.com/en/surfboardstock/index.php?accao=showarticle&id_cmsconteudo=219





colas
4001 posts
13 Oct 2020 2:31PM
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Select to expand quote
515 said..
From your windsurfing days did you ever see Angulo boards in the early 90's with "Phasers"?
They were a series of shallow hemispheres in the bottom of their boards.


Yes, but this was nothing new...
Early Windsurfers made in Holland by Ten Cate had foam mixing issues, and developed 4"-wide depressions by themselves over time. A board I had in 1977 had more than 30 of them on its hull :-)... It had no significant effect I could feel... but it was a 22kg board :-)

Jeroensurf
395 posts
15 Oct 2020 9:28PM
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The idea behind the phasers was getting airpockets there, making the board looser/less grippy on the water.Didnt work.

DavidJohn
VIC, 16459 posts
16 Oct 2020 4:56AM
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Jeroensurf said..
The idea behind the phasers was getting airpockets there, making the board looser/less grippy on the water.Didnt work.


Did work.. IMO.. because there was a noticeable difference that could be felt.. but the shaping and especially the glassing and sanding was the hardest part to achieve with very little gain in performance..
Mark was a friend back in the day before Josh was on the scene and their dad Ed was an awesome shaper who thought the golf ball principal was worth the effort to try and many people loved these boards.

colas
4001 posts
16 Oct 2020 1:36PM
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Select to expand quote
Jeroensurf said..
The idea behind the phasers was getting airpockets there, making the board looser/less grippy on the water.Didnt work.


No, it was just to create vortexes to promote water on water friction, which is smaller than rather than water on hull, thus keeping the flow laminar on a longer length, like on a golf ball.

In my opinion, it is just simpler to just have a sanded finish on the hull rather than a glossy one to achieve better laminar flow easily.

PS: I have read somewhere that channels, concaves, etc... and other hull features were just an invention by sadistic shapers to torment their glasser and sanders :-) It was intended as a joke, but... was it? ;-)

515
527 posts
16 Oct 2020 2:20PM
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Agree on wet sanded finish.
One time in Maui I did repairs and they had a lot of Angulo "phaser " boards with a number of cracks on the flat edges of the phaser - pia but not compared to glassing board!
Concaves were very subtle when I was building boards.
The worst was when I copied a bottom shape of twin tip wake board with elliptical phasers and channels so I could add twin fins to natural stance and play with sharpness/ softness of rail.
The things you can learn with experimenting on boards

Nozza
VIC, 2574 posts
16 Oct 2020 7:43PM
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From going back to sailing skiffs, we always went for a wet sanded rather than gloss finish.
But that may have been more of a reflection on our painting skills rather than hydrodynamics.
But,
a couple of years ago I put a camera under my board for a 5km paddle.
The whole time, given it was a double concave board, there was air under the board.
This I think means our boards are in turbulent flow the whole time, so any skin friction issues are irrevenant as we are never in a laminar flow situation.
Or I could be full of ****.
Probably the latter

gregjet
QLD, 34 posts
17 Oct 2020 7:32AM
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The thing most forget , is that except when surfing down a wave, the paddled board is NOT having the water flow along the board. It is the board moving over/through the water. The water is being pushed apart and flows back again. It is being moved more sideways, than front to back. Sounds trivial but isn't . Most of the water only moves about half the width of the board, except for the forward movement from the breaking wavemaking and skin friction.
When air gets trapped under the board it will follow the path of leat resistance, which on a flat surface, will be to the outside with the water. Concaves keep the air traped for longer and reduce the boundry layer friction ( less viscosity).
In practice it means that a board designed for paddling speeds , is probably not optimium for surfing induced speeds. Same goes for the fin shapes.

Balsaboards N.Z.
88 posts
18 Oct 2020 9:26AM
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yep, dont get a polish ;)



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"Fish scales reduce friction drag by 25%" started by colas