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wave fin ques....???
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coachg



Joined: 10 Sep 2000
Posts: 2003

PostPosted: Thu Jan 03, 2013 1:29 pm    Post subject: Re: wave fin ques....??? Reply with quote

skyking1231 wrote:
i know wave fins give better manueverablilty..... but why ?

anyone have a simple explanation ?


Simple explanation:
Less area means less lift and you counter the lift so a board with less lift is easier to turn and softer material so more flex or less resistance to the turn.

For less simple explanation read the above post. Rake, tip, width, thickness and throw in the adjustability of the Standard Box fin and you can not get “simple.”

Coachg
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isobars



Joined: 12 Dec 1999
Posts: 14239

PostPosted: Thu Jan 03, 2013 1:43 pm    Post subject: Reply with quote

U2U2U2 wrote:
surf fins are closer, but do not have the same loads, or any desire to go upwind


But go upwind they will, just not as efficiently. I hear it very often in the Gorge: "I sail little boards with small fins, so I can't point at all. Turning and pointing are mutually exclusive." These guys swear they can't gain even 100 feet of westerly (upwind) ground in a one-kilometer reach (with no current), and are condemned to BAFing in front of the launch, out of reach of any better conditions that may lie upwind or downwind. I've even seen at least one advanced sailor quit WSing because he could never get his sinker upwind at all.

Then I go out on a smaller, turnier board with a wavier fin and turn and point just fine, by non-racing standards, going thousands of yards up and down the river. Superior skill? Sharper rails? Secret techniques?

Naaah; bigger sail.

Then add truly expert skills, and my bigger sails still suck ground ... IF the other, better, sailor is planing at all on his little fin and little sail.

Sure, I gotta try harder, and can't point quite as high, if I'm on a pure wave board with a pure wave fin instead of a B&J fin and/or a more slalomy board, but that's OK, at least until the wind backs way off and I'm underpowered. That's a big part of why I rig big; rigging and sailing for maximum efficiency (i.e., smallest sail bragging rights) costs us versatility, planing time, upwind and downwind ability, and often speed.

My relative point is that, as others have indicated, fins don't work in a vacuum. They're a partially assimilated part of the Borg ... and we haven't gotten into the arrangement options possible with 2 to 5 fins.
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U2U2U2



Joined: 06 Jul 2001
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Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Thu Jan 03, 2013 4:29 pm    Post subject: Reply with quote

Rolling Eyes
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skyking1231



Joined: 10 Jul 2000
Posts: 72

PostPosted: Thu Jan 03, 2013 4:53 pm    Post subject: Reply with quote

thanks for the replies. I got it now. (why did it take so long for me to figure it out ?)

As the one mentioned...ws fins and airplane wings...as much as they are similar....they are dissimilar.

remember the hydrofoil fins ?? I only saw pictures and maybe a vid back in the day.
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PeconicPuffin



Joined: 07 Jun 2004
Posts: 1214

PostPosted: Thu Jan 03, 2013 5:34 pm    Post subject: Reply with quote

skyking1231 wrote:
thanks for the replies. I got it now. (why did it take so long for me to figure it out ?)

As the one mentioned...ws fins and airplane wings...as much as they are similar....they are dissimilar.
.


Well, they're more similar than dissimilar.

What's useful about the difference between fins is it allows you to tune your board for different conditions (or different sailing plans) by quickly switching a relatively inexpensive component. Wind is a little light but you don't want to rerig? A bigger fin helps. Having trouble holding a planing carve in a duck jibe? Go more swept or smaller. And so on.

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U2U2U2



Joined: 06 Jul 2001
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Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Thu Jan 03, 2013 7:47 pm    Post subject: Reply with quote

a wing is a sort of fin.

most aircraft wings are asymmetrical , most windsurf fins are symmetrical

aircraft wings have flaps & slates that can change the angle of attack to provide lift for take off and then less drag when at cursing attitude to provide speed and fuel economy. They also have flex 26' on the Boeing 787.

Penguins have wings. But dont fly, where flying fish and flying squirrels do fly, or more proper glide.



fluid mechanics, Bernoulli's principle are all things a aeronautical engineer will understand and take delight in discussing, me, way beyond my comprehension

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noshuzbluz



Joined: 18 May 2000
Posts: 776

PostPosted: Thu Jan 03, 2013 8:04 pm    Post subject: Reply with quote

U2U2U2 wrote:

fluid mechanics, Bernoulli's principle are all things a aeronautical engineer will understand and take delight in discussing, me, way beyond my comprehension


Brian at Open Ocean has brought up his name numerous times. Pretty interesting. Rick at MUF also has some interesting sections on his website. Here's a couple of them:
http://mauiultrafins.com/MUF7_english/About.html
http://mauiultrafins.com/MUF7_english/FAQ.html

Good stuff if you're in to that scientific kinda thing.

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cgoudie1



Joined: 10 Apr 2006
Posts: 1259
Location: Killer Sturgeon Cove

PostPosted: Thu Jan 03, 2013 10:51 pm    Post subject: Reply with quote

Funny you should mention penguins, since they do fly, through water,
and use their wings much like.......... fish fins, only with more birdlike
flying motion.

Bernoulli works either way, but there are differences in whether
the medium is compressible or not.

-Craig

U2U2U2 wrote:
Penguins have wings. But dont fly, where flying fish and flying squirrels do fly, or more proper glide.



fluid mechanics, Bernoulli's principle are all things a aeronautical engineer will understand and take delight in discussing, me, way beyond my comprehension
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isobars



Joined: 12 Dec 1999
Posts: 14239

PostPosted: Fri Jan 04, 2013 9:28 am    Post subject: Reply with quote

Not to mention that, after 100 years of flying machines, the entire concept of airfoil lift is being seriously debated by aeronautical engineers. Is it Bernoulli or Newton that keeps these things up there?

Just one example:
http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/airfoil.html
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Wind-NC-Hatteras



Joined: 28 Jun 2008
Posts: 777
Location: Cape Hatteras, NC

PostPosted: Fri Jan 04, 2013 9:34 am    Post subject: Reply with quote

Another thing to consider is the amount of torque that is required to put the board on it's rail, or more importantly, go from one rail to the other. A long straight fin will require more torque due to the amount of surface area further away from the board. A short, chordier fin with most of it's area right up next to the bottom of the board requires less torque to rock back and forth.

This explanation might be used to describe why the radically different outlines of the mufin and the traditional wave fin both have similar sailing characteristics- overall, they're both relatively short and wide fins, despite the different tip shapes.

Disclaimer- I'm not a physicist... Very Happy

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