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wave fin ques....???
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skyking1231



Joined: 10 Jul 2000
Posts: 73

PostPosted: Wed Jan 02, 2013 12:08 pm    Post subject: wave fin ques....??? Reply with quote

i know wave fins give better manueverablilty..... but why ?

anyone have a simple explanation ?

google didn't really come up with much (at least the search i did).
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U2U2U2



Joined: 06 Jul 2001
Posts: 3085
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Thu Jan 03, 2013 12:30 am    Post subject: Reply with quote

they are shorter,they may have less area, they have more rake (compared to a pointer style)

some will have a more flex tip.

simple answers for a single wave fin board.

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skyking1231



Joined: 10 Jul 2000
Posts: 73

PostPosted: Thu Jan 03, 2013 10:27 am    Post subject: Reply with quote

But why ? why does the rake make it more maneuverable ?

that is what i have always wondered. I can see why a race/slalom fin will give better pointing...and that sort of thing.

looking for the physics behind it. I would think maybe the rake moves part of the lift more aft than allowing for more of a pivoting motion ???
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U2U2U2



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

PostPosted: Thu Jan 03, 2013 10:32 am    Post subject: Reply with quote

you said simple, being smaller ALONE would account for being more maneuverable.




http://en.wikipedia.org/wiki/Hydrodynamics

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noshuzbluz



Joined: 18 May 2000
Posts: 777

PostPosted: Thu Jan 03, 2013 10:59 am    Post subject: Reply with quote

Let's open the can-o-worms!
I really like the TA Enduro fin but at the same time like the MUF Wave. Two totally different concepts. Both work really well.



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U2U2U2



Joined: 06 Jul 2001
Posts: 3085
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Thu Jan 03, 2013 11:13 am    Post subject: Reply with quote

both those fins have rake on the leading edge, they are different as night and day, but are both wave fins, and offer guess what , wave fin qualities.

unlike a pointer type that is designed to offer speed,early and sustained planing , while suffering somewhat in the turn capabilities, relative to the wave type fins

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noshuzbluz



Joined: 18 May 2000
Posts: 777

PostPosted: Thu Jan 03, 2013 11:32 am    Post subject: Reply with quote

And the MUF fin doesn't flex/twist while you can really feel the enduro twist like crazy when you really crank hard on it.
Again two totally different concepts. Both work well.

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isobars



Joined: 12 Dec 1999
Posts: 14339

PostPosted: Thu Jan 03, 2013 11:46 am    Post subject: Reply with quote

One source for answers to your question would be a friend who has all the back issues of WSMag. Once upon a time, it published endless technical analyses of WSing components, including fins. I actually read the mag back then, not so much the last 10-15 years.

Another source would be to take your understanding of how race/slalom fins work and reverse each concept. Take these generalizations, for example:

Short chord lengths minimize drag, promoting greater top speeds for a given hull and sail. Straight edges optimize a fin for a narrow range of attack angles and speeds. Fin area is highly dependent on the sail's drag -- which is in turn dependent in part on sail size -- which it must counteract. To get the area needed by a racy fin, its short chord length dictates a long fin, which puts more area further from the hull compared to a wavy fin, which adds moment arm to the sudden rail-to-rail transitions common to turny sailing but rare in racing (try slashing right to left to right to left hard and tight and fast on a 40 cm fin vs a 22 cm fin of the same area). IOW, extra length damps rail to rail transitions. Stiffness also optimizes a fin for the narrower performance regime (e.g., top speed, max pointing) required for racing. All these factors also effect spinout resistance and recovery.

You want just the opposite for turny WSing, whether it's in ocean waves or you local bumpy lake. Their shorter length reduces angular damping to alow quicker slashing, their planform/profile edge curves and flex and twist allow a broader range of angles of attack, and their longer chord length provides greater power at slower speeds for accelerating out of speed holes produced by maneuvering. And as above, all these factors also effect spinout resistance and recovery even before one considers the pros and cons of slots.

Whether it's the wings of an airplane or a WSer fin, short'n'stubby promotes maneuverability at the expense of drag and thus top speed (wave fins, fighter aircraft), long wings/fins w/high aspect ratio reduce drag to promote speed and glide (long range bombers, the U2 spy plane, race fins). Every design tweak must compromise between these opposing requirements, and even non-jibers can feel performance differences between two different wavy fins, let alone a wavy fin vs a racy fin.

Mike \m/
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bred2shred



Joined: 02 May 2000
Posts: 661
Location: Jersey Shore

PostPosted: Thu Jan 03, 2013 12:36 pm    Post subject: Reply with quote

One of the main reasons wave fins are more manuverable is simply because they're shorter, therefore the fin's CE is closer to the bottom of the board. This means the fin has less influence over the heel/angle of the board. I.e., the fin is less likely to rail the board up. This means that the sailor can have his feet closer to the centerline of the board which in turn allows for easier and more aggressive carving. The shape of wave boards also has a lot to do with manuverability (lot's of rocker, vee, and rail tuck).

The soft and swept tip of wave fins also makes them much more forgiving and manuverable. The tip of the fin will flex to remain aligned to the flow (up to a point). So they are more predictible about when they are close to spinning out and they are easy to pull back in when they do spin out. All this means that the board can be carved and ridden agressively with less risk of the fin letting go.

sm
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U2U2U2



Joined: 06 Jul 2001
Posts: 3085
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Thu Jan 03, 2013 1:08 pm    Post subject: Reply with quote

B2S

thanks .. your response is more detailed than mine, but overall says the same as my 1st post.


lots of people have made reference to windsurf fins to aircraft wings, there are as many dissimilarity's as those similar.


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

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