thick fins

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alakaboo
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Re: thick fins

Post by alakaboo » Sat Jun 30, 2012 8:36 am

Dunno about faster in a straight line, unless you mean the thin ones are flat and don't have foil.
A thick fin supposedly has less drag I.e. turbulence and is better for direction changes.
I've ridden some very thick windsurfing fins, close to an inch thick.
Put one in a short single and it was very smooth, but the fin wasn't foiled properly it was pretty huge

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Cpt.Caveman
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Re: thick fins

Post by Cpt.Caveman » Sun Jul 01, 2012 5:20 pm

I haven't experimented much between thick and thin fins, however to my understand the stiffer the fin the more drive it can produce, but to the detriment of responsiveness compared to a fin which flexes more and is easier to overpower.
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PeepeelaPew
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Re: thick fins

Post by PeepeelaPew » Mon Jul 02, 2012 11:50 am

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Last edited by PeepeelaPew on Tue Jul 03, 2012 5:51 pm, edited 1 time in total.

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ric_vidal
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Re: thick fins

Post by ric_vidal » Tue Jul 03, 2012 11:24 am

saltman wrote:Seems almost counter intuitive that a thick profiled fin will be faster - but look at the front edge of plane wings
Our good mate Roy uses this as reference (I believe) for both board shape and fin foil...
NACA foils.jpg

alakaboo
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Re: thick fins

Post by alakaboo » Tue Jul 03, 2012 1:05 pm

From what I remember of fish locomotion lectures the thickest point should be 1/3 to 1/4 from the front.

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ric_vidal
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Re: thick fins

Post by ric_vidal » Tue Jul 03, 2012 1:15 pm

saltman wrote:Nice so thickness should = 10% of length
But where do you position the thickest foil?
In some of my fins the thick point seems to vary along the lenghtg at different heights of the fin ?
I'm a great believer in PHI (1.618) for most things, think it might migrate pretty well to this. So I work elements around the decimals and use 'em as a percentage 62% and 38%

So my application would be put the widest point 38% of the way through the cord length.

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Re: thick fins

Post by Nick Carroll » Tue Jul 03, 2012 1:34 pm

fongy it all depends what you mean by "faster".

If you mean "more slippery" (like creating less turbulence and thus less drag) then it's all about getting the foil right, not so much the thickness per se.

I'd imagine boo's sailboard fin was thick because the designer wanted it to be stiff as a board and not flex around, not because of any foil advantage.

Foil is pretty much a settled issue, you want to go to a good boat designer and talk to him/her -- if you're lucky he/she might use some design software and draw you your very own perfectly foiled fin CAD program. Then you can go get a fin plate and get it cut to order. It'll cost a bit but most good design does.

I guess what I'm saying is that it's all been done elsewhere outside the surfing world, no need to re-invent the wheel on foils.

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ric_vidal
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Re: thick fins

Post by ric_vidal » Wed Jul 04, 2012 1:01 pm

fongss wrote:
ric_vidal wrote:
I'm a great believer in PHI (1.618) for most things, think it might migrate pretty well to this. So I work elements around the decimals and use 'em as a percentage 62% and 38%

So my application would be put the widest point 38% of the way through the cord length.

interesting ric....i'm thinking a board and fins made too that formula :idea:

the foil of the fin matching the foil the board :idea:
Mate, played with the formula with boards, but hard to know how and where to apply so gets a little confusing to say the least.

I reckon it isn't a bad formula for volume though, slightly different to Feral Dave (.35).

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dUg
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Re: thick fins

Post by dUg » Wed Jul 04, 2012 2:15 pm

Ever so slightly hinting at Reynolds Numbers there Ric? ;)

Pretty much every mainstream fin manufacturer uses the NACA foil... in fact... they pretty much use the identical foil. Sure... tweaking outlines, different flex chx & materials etc have an effect, but it's only experimenters and foil nerds who play with the foil.

I have some fins in my posssion that DON'T use the NACA foil ( which arguably was desgined for aircraft wings with mostly straight leading and trailing edges ), BUT maintain a constant foil. I have reasons behind it I won't broadcast here, but everyone who's surfed 'em loves 'em. 8)

As for thicker foils... much thicker = more surface area = more drag, but given the inherent turbulence at the base of anything that isn't a glass-in fin it's all relative.

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ric_vidal
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Re: thick fins

Post by ric_vidal » Wed Jul 04, 2012 3:45 pm

dUg wrote:Ever so slightly hinting at Reynolds Numbers there Ric? ;)
Had never heard of it, dUg, until your reference. I just don't have the head for those formulae.

Nah, just think nature has a knack, but it's all about numbers ultimately.

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steve shearer
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Re: thick fins

Post by steve shearer » Mon Jul 09, 2012 1:27 pm

Most pros use fin systems.

Not one pro in the top Ten uses glass ons.
I want Nightclub Dwight dead in his grave I want the nice-nice up in blazes

damo666
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Re: thick fins

Post by damo666 » Mon Jul 09, 2012 6:35 pm

steve shearer wrote:Most pros use fin systems.

Not one pro in the top Ten uses glass ons.
Hmmm, are you absolutlely sure about that Steve? I know without a doubt that when Taj was riding Firewires last year they were all glass-on's, which was his preference, and the Mayhem he won this year's Snapper event also had glass ons.....

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steve shearer
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Re: thick fins

Post by steve shearer » Mon Jul 09, 2012 8:53 pm

You're right, I'm wrong.

By my obs at Snapper and Bells Taj is the only pro in the top 16 rocking glass-ons.
I want Nightclub Dwight dead in his grave I want the nice-nice up in blazes

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ric_vidal
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Re: thick fins

Post by ric_vidal » Tue Jul 10, 2012 10:02 am

damo666 wrote:
steve shearer wrote:Most pros use fin systems.

Not one pro in the top Ten uses glass ons.
Hmmm, are you absolutlely sure about that Steve? I know without a doubt that when Taj was riding Firewires last year they were all glass-on's, which was his preference, and the Mayhem he won this year's Snapper event also had glass ons.....
Other question would be, was it really a Firewire?

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Re: thick fins

Post by collnarra » Tue Jul 10, 2012 11:27 am

I don't think Taj is riding FWs anymore. I ready Matt Biolos' blog (mayhem / lost) and he seems to be doing a few for him (and everyone else!)

Biolos seems to have his head screwed on the right way. Does some lovely looking boards, and you know what they say - if it looks right....

JG
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PeepeelaPew
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Re: thick fins

Post by PeepeelaPew » Tue Jul 10, 2012 3:26 pm

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Last edited by PeepeelaPew on Wed Jul 11, 2012 10:47 am, edited 1 time in total.

Quangers
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Re: thick fins

Post by Quangers » Tue Jul 10, 2012 5:50 pm

steve shearer wrote:You're right, I'm wrong.

By my obs at Snapper and Bells Taj is the only pro in the top 16 rocking glass-ons.
He mustn't have worked out a fin sponsor yet - he'll have to sack the manager!

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ric_vidal
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Re: thick fins

Post by ric_vidal » Wed Jul 11, 2012 9:22 am

collnarra wrote:I don't think Taj is riding FWs anymore.
JG
No he isn't, but that wasn't the inference.

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