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Fins

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Created by stehar > 9 months ago, 30 Jan 2020
stehar
NSW, 406 posts
30 Jan 2020 9:13PM
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Arrived today - try out tomorrow on Woolgoolga lake - into surf next week

pete53
NSW, 219 posts
30 Jan 2020 10:16PM
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What board are they going on?

stehar
NSW, 406 posts
31 Jan 2020 9:19AM
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Board is a custom blue planet - quad only - the " Jimmy Lewis quad converted me! Brilliant board but too small for me inthe end ( very tiring ) this is a beefed up version and is ideal for fast semi close out beach breaks. Steve

DHUPEDNORTH1
108 posts
31 Jan 2020 10:31AM
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I believe a quad set of Quobbas is not too far off now (been using a top line specialist in quads to assist in development apparently - they only do things properly so these things take time). And they're loving working with the SUPers, happy to split sets (e.g. for the JL riders), have a chat to them, love their keenness for innovation and to try new things/set ups, etc. They have a real interest in SUPs now considering the company was originally started some years ago by shortboarders (proners) for shortboard fins.

stehar
NSW, 406 posts
1 Feb 2020 11:48AM
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The Quobba fins measure 113mm deck to top - the back set measure 110mm deck to top { height } Is it necessary to have much smaller back fins - what effect will my setup have on performance?

Just noticed that most quad setups have smaller back fins!

Steve

colas
4271 posts
1 Feb 2020 3:38PM
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stehar said..
what effect will my setup have on performance?

Just noticed that most quad setups have smaller back fins!



In my experience (and Tom Carroll also mention it in a video), SUP quads need smaller back fins than what is used on prone shortboards. I guess because SUPs have longer and heavier, and bigger rear quads will stiffen the board too much: the board will tend to track. For instance I used L or XL fronts with S rears, or even twin fins in front with trailers as rears.

Basically, in your turns, if you understeer, you need a bigger difference between your front & rear fins, and the opposite if you oversteer.

The exception is very short (about less than 7'6") and light SUP boards, and if you can put your rear foot locked between the kick & arch on the rear pad in top turns, then you can use rear quads as big as the prone shortboard ones. I thus can use quobba L fronts with Quobba M rears on my 6'10" small wave board.



Also there are 2 type of quads: the ones with the rears close to the front ("edge fin"), which can handle bigger quads, and the most common ones, the McKee setup (as on my pic above), where they are closer to the central fin of a thruster, where they can be quickly overfinned.

stehar
NSW, 406 posts
1 Feb 2020 10:02PM
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Thanks Colas

estingo
81 posts
7 Sep 2020 7:37PM
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My set up for the Hokua 7'10 with K4 fins 13 cm in the front 12 cm in the back and the Quatro 8'0 MFC large in the front (stock fins) and HS quads small in the back








stehar
NSW, 406 posts
8 Sep 2020 6:20AM
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Angle maybe toe-in fairly exaggerated?

estingo
81 posts
8 Sep 2020 9:36PM
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How do you mean? and for which board? will try the next session the thruster again.

Balsaboards N.Z.
90 posts
12 Sep 2020 2:41PM
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colas said..

stehar said..
what effect will my setup have on performance?

Just noticed that most quad setups have smaller back fins!




In my experience (and Tom Carroll also mention it in a video), SUP quads need smaller back fins than what is used on prone shortboards. I guess because SUPs have longer and heavier, and bigger rear quads will stiffen the board too much: the board will tend to track. For instance I used L or XL fronts with S rears, or even twin fins in front with trailers as rears.

Basically, in your turns, if you understeer, you need a bigger difference between your front & rear fins, and the opposite if you oversteer.

The exception is very short (about less than 7'6") and light SUP boards, and if you can put your rear foot locked between the kick & arch on the rear pad in top turns, then you can use rear quads as big as the prone shortboard ones. I thus can use quobba L fronts with Quobba M rears on my 6'10" small wave board.



Also there are 2 type of quads: the ones with the rears close to the front ("edge fin"), which can handle bigger quads, and the most common ones, the McKee setup (as on my pic above), where they are closer to the central fin of a thruster, where they can be quickly overfinned.


nailed it mate

estingo
81 posts
14 Sep 2020 2:43PM
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stehar said..
Angle maybe toe-in fairly exaggerated?


Hello Stehar, probably for both then, I'll read this thread on the forum over here: www.seabreeze.com.au/forums/Stand-Up-Paddle/SUP/Multi-Year-Fin-Experiment-on--no-Toe-straight--Fins?page=3

Maybe the Riptide fins could take away the exaggerated toe-in what you mentioned.

I bought a pair to experiment as well. I have for the coming weeks a lot to try and change to see what works best.

estingo
81 posts
26 Feb 2021 5:15AM
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Got some other bad boy fins to try out soon when the waves are pumping again, Evafins
hollow in through the middle, release point above the E at the logo, and rounded shape.



Emeboy
NSW, 346 posts
26 Feb 2021 11:28AM
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estingo said..
Got some other bad boy fins to try out soon when the waves are pumping again, Evafins
hollow in through the middle, release point above the E at the logo, and rounded shape.




What the heck!! Do these ones have WiFi as well Estingo??

DHUPEDNORTH1
108 posts
26 Feb 2021 10:26AM
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estingo said..
Got some other bad boy fins to try out soon when the waves are pumping again, Evafins
hollow in through the middle, release point above the E at the logo, and rounded shape.



wow! love to see the CFD modelling on those. Expect they would be trying to create more lift?

colas
4271 posts
26 Feb 2021 2:17PM
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estingo said..
Got some other bad boy fins to try out soon when the waves are pumping again, Evafins
hollow in through the middle, release point above the E at the logo, and rounded shape.


Wow, I never heard of them.

I am a bit skeptical however, about the embossed logo. How could anybody with any hydrodynamics awareness put such a huge flow-pertubating thing on the side of their fins? For instance, I immediately sanded off the raised FCS logo on the side of my nubsters, and they were much less obtrusive, and only on one side, and after the flow separation point...

Tardy
QLD, 4042 posts
26 Feb 2021 4:52PM
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Looking at those weird fins I Always thought ,you need fins to cut the face of the wave and be fast at doing it ,like a hot knife through butter .

I couldn't see these doing that ,but be draggy instead ,I could be wrong

estingo
81 posts
26 Feb 2021 3:34PM
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Haha, very good guys I'm the same as you very skeptical but when I saw them I had to try them! btw no WiFi included (bummer)

They are made in Spain and they tested them on the same program like Quobba did "Computational Fluid Dynamics program".
I was also concerned about the holes in the beginning that they are all on the same side of the fin, I would place them all on the outside of the fin instead, but it's just esthetics, they won't affect your performance according to the creator. Especially for the flow-perturbation, I thought that it would maybe have a stabilizing function with the hole in the middle with the releasing point through the logo. I also agree with the logo that it might create too much of a "drag" factor in the hydrodynamics department, but I have to find this out myself.

Will keep you updated on how this goes because I'm very curious how these will feel in the water as well. As there is no rake on these fins, it would probably feel more agile and counterintuitive fins, the creator is saying that the hole is the secret in these fins.

If you want, you can give this guy a shout out on Instagram @evafins_surf



slsurf
60 posts
27 Feb 2021 12:36AM
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I couldn't understand these fins either until I realized there is a miniature jet ski engine contained on the inside, then it all made sense. I guess we all have seen non-raked fins in windsurf and sailboats, so might be ok in a straight line but wonder about turning and drag.

colas
4271 posts
27 Feb 2021 3:56PM
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estingo said..
They are made in Spain and they tested them on the same program like Quobba did "Computational Fluid Dynamics program".
I was also concerned about the holes in the beginning that they are all on the same side of the fin, I would place them all on the outside of the fin instead, but it's just esthetics,


Did you find any info? there is nothing on his instagram...

I guess "it's just esthetics" summarizes the concept :-)
The square leading edges are abysmal.

estingo
81 posts
28 Feb 2021 3:39AM
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Hi Colas, I think so but they do test it. At the moment they are working on a website because they get a lot of questions like what we have over here as well. I'm just sostupidcurious to buy them without background information. He still mentioned "you know the advantage of ends, these are ultra technology. The water enters at 4m per sec and comes out at 17m sec, more agility and flexibility on the board".. but for me is it now just another esthetic gimmick. Probably coming Friday if the forecast stays like this I have the opportunity to test them out.

Other Quote's of him are:
"The agility you will feel it regardless of the size because the water penetrates inside the fin"

"The material is from a 3d printer: Technologie ultra tech voxel"

colas
4271 posts
28 Feb 2021 2:58PM
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estingo said..
The water enters at 4m per sec and comes out at 17m sec



I am totally skeptical of this statement.

Imagine the board being dragged at 4m/s in a pool, and looking at the wake, e.g with some ink droplets in the water.
You can do the experiment yourself in your bathtub with the fin moved by hand.

There is no way the fin will eject water at 13m/s backwards (relative to the bathtub) in its wake. Perpetual movement is not possible.

What has probably happened is that they set up the simulation software with a constant water flow. This means that it forced the 4m/s water to go through a small hole, increasing its speed... because they supposed that there was a pressure build to jam the water through at the artificially fixed 4m/s. But this pressure both needs a force exerted on the water (by the only moving part: the fin, creating drag by reaction), and the pressure itself will increase drag on the leading edges of the fin!

Basically the common bull** of "Venturi/Concaves creating speed" you read from people with no scientific background: focusing on a small part of a complete system, ignoring the opposite forces at play in the whole picture.

estingo
81 posts
1 Mar 2021 4:30AM
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Hi Colas,

Totally agree with you assessment on the comments on the statement that Evafins made. Especially because I did "your" test the day they arrived in the baby bathtub I wanted to see how the water speed would increase and with those number it should be squirting out of the back or the eva fin hole. It came out faster but of course I couldn't measure the outcome speed.

I was also already thinking how I could measure the speed compared to other fins. Because it made me wonder if you have a small focus compared to a wider focus. What you mentioned about the "Venturi/Concaves creating speed" and the small part of the bigger picture. I have actually studied hydrodynamics at the university so basically do I understand where you are coming from.

Anyway I'll let you know how they go, if it's rubbish will I also tell it, and they have a though competitor in my fin quiver because I'm comparing it to the quobba fins.

colas
4271 posts
1 Mar 2021 2:04PM
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Yes.

This said, there is more to a fin than just efficiency (lift/drag ratio). Handling, control, predictability,... lots of things can make an hydrodynamically "inefficient" fin great for surfing. I am eager to read your report!

Kami
1542 posts
1 Mar 2021 3:47PM
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I'm very sceptical about this fin as I'm also about any fin that is working separately from the board. My opinion about fin is that a fin is making work the planning area giving the drive to the complete hull made of the board and fin altogether.
Fin is just a 3D extension of the rail line they won't be able to generate fin by themselves. The fin is making the drive from its base as close as back foot toe or heel it can be and the tip of the fin is stabilizing the drive of the overall board.
Here a study under Shape3D to imagine hull and fin designed altogether in the same project: www.shape3d.com/Viewers/Viewer3D.aspx?Board=7527

ECSurf
8 posts
5 Mar 2021 6:41PM
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I took a large Quobba thruster set out this morning in peak shoulder/head beach breaks. Definitely noticed increased speed on hollower waves, made sections that I would not normally expect to make. Really nice drive off the bottom turn. Looking forward to confirming with a few more sessions. Thanks for the recommendation Colas! Was running an 8'9 Flash, I am 107kg and 6'6. The large set was perfect, loose but with lots of drive. It would definitely suit lighter folks as well.

estingo
81 posts
9 Mar 2021 10:58PM
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estingo said..
Got some other bad boy fins to try out soon when the waves are pumping again, Evafins
hollow in through the middle, release point above the E at the logo, and rounded shape.





Tried these out last week on the quad set-up like shown in the picture and another day I used the riptide fins (from this topic:www.seabreeze.com.au/forums/Stand-Up-Paddle/SUP/Multi-Year-Fin-Experiment-on--no-Toe-straight--Fins) with no toe in the front and the Eva fins in the back.

For the first try I experienced that starting paddling they are faster than normal fins, once you have the wave they slow a bit down and generate some drag but once on the face of the wave they start generating speed. I think after the turbulence of the water underneath is settled and it goes through the fin, like a turbo that needs to get a certain amount of spins before you feel the power (turbo lag). So I thought if I switch the front fins to a traditional shape (ultimate set up is quobba's in the front, but before that, I wanted to test again the riptides) and keep the speed/turbo feeling of the quads (rear fins) on the back. That would be the bomb, so I tried that the other day.

So my feeling today was that they were not quicker while paddling for the wave but once on the wave dropping in they were quite fast and it kept generating speed so I could gain speed in the bottom turn and they felt very lose with those 12 cms (in the back) in the top turn.

The next try is a thruster set-up of two of those Eva fins in the front and 1 quobba medium in the back.
I'm just trying different setups as well but I think for now the quobba's are too superior to beat even though these are more fun than normal fins because there is happens something which feels like a propulsion and you can still turn them easily. The only thing that I don't like is the small drag factor by dropping in (4 eva fins in quad setup). Two normal fins in the front and two Eva fins in the back should do the trick, if I try quad again will it be 2 large quobba's in the front and 2 Eva fins in the back.

I have no theoretical background to back up my feeling on how they surf, but I will keep experimenting. For the record, my experienced is based on these Dutch waves, that were clean but only shoulder high.




estingo
81 posts
16 Jul 2021 7:37PM
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Tried today the Eva fins again in a thruster set-up in some choppy head high waves. Not the best feedback with this kind of waves and I'm also not saying that everyone needs to hop on the EVA fins bandwagon but they work. Can't compare them with the Quobba's that's just another league but they are responsive and they track well when you're paddling which is nice.




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"Fins" started by stehar