Wow look at all these parabolic wood rails...

General Discussion
1

…in the new Surfer oversize issue. That beauty board Kelly Slater’s riding in the feature (67 things to do before you take your last ride")? And then Mick Fanning airborne on one a few pages later. And Bobby Martinez riding a clear one a few pages after that?

And there’s Daniel Thomson in a Honolua Surf Co. ad, cutting the rails off a blank he’s shaping…

Beautiful sprays on the Slater and Fanning boards.

Hmmm. Big Firewire ad running in the back… Firewire board in the “Board Forum”…

Revolution in the air…

2

But, but, what’s that k00k screw thing on the deck of Bobby’s board?

seriously, I was most impressed by the 1% for the planet badge on the firewire ad. way to go guys.

3

Apologies if this has been covered elsewhere but … what is it about parabolic rails that’s … parabolic?

Perimeter stringers could be made parabolic regardless of a board’s planshape. (But would that make them work better than ones that were simply … curved?)

But for the rails to actually be parabolic, wouldn’t the board’s planshape have to be parabolic?

I’m thinking I might have a bunch of foam-and-fiberglass parabolic rails on my old pu/pe boards. Cool! (humor intended).

4

I think what you have there may in fact be metabolic

5

Hi -

Maybe you (or someone else who knows about these kinds) of things can explain…?

What is the difference between a parabola and hyperbola?

I see snow skis with the exagerrated “hourglass” shape referred to as “parabolic”, yet on surfboards, the “parabolic” stringers bow the opposite way, i.e. outward curves - wider in the middle.

The “butterfly” stringer configuration (like on old G&S Hot Curls or John F’s Butterfly Bonzer) for instance… should it be referred to as hyperbolic or parabolic?

http://www.swaylocks.com/resources/detail_page.cgi?ID=1333

6

Hey, some thing I know about, unlike surfboards.

Math is all about definitions. So suppose you have a plane, regular x and y coordinates. Then you can define things like lines, eg a horizonal line that goes through the point x=0 y=2 is made up of all the points that have coordinates like (2,a) where “a” can be any number.

A hyperbola is defined like this:

Pick two points, say (-2,0) and (2,0) [but they could really be any two points] call these P and Q.

You then pick some number, say 5, call this K.

You can measure the distance from any point on the plane to any other, for let d(P,Q) be the distance from P to Q for example.

Then the hyperbola is defined as all of the points that satisfy this equation: d(T,Q)-d(T,P)=K

Or in english I “decide” that a point is on the parabola if the distance from that point to P minus the distance from that point to Q is equal to K.

This turns out to give two curves like the butterfly board you mentioned.

A parabola is a little different, and only defines one curve. It’s the (x,y) coordinates that satisfy (att, 2at) where “a” is some number you chose to determine the shaper of the parabola and “t” is any positive number.

I don’t know if you actually wanted to know this, but here it is.

I used these pages to jog my memory, there’s some pictures is my explination didn’t make sense.

http://mathworld.wolfram.com/Hyperbola.html

http://mathworld.wolfram.com/Parabola.html

7

Hi John and all,

Boy, was I spacing. What I was thinking was a parabola is actually an ellipse. (Definitely a metabolic issue.)

Wikipedia has a seemingly good page on parabolas here: http://en.wikipedia.org/wiki/Parabola

I don’t know the slightest thing about parabolas myself.

But I think my question still stands should anybody care to entertain it: What is it about parabolic rails that’s parabolic? What, if anything, is their parabolic quality?

One of the pictures on wiki kind of looks like a knife rail to me, but I don’t think that’s it.

8

I hate to beat this to death - here’s an article that maybe explains my confusion… although dated '99, it details the hourglass shaped skis that have become the norm today as “parabolic.”

Virtually EVERY ski manufacturer now has “parabolic” shaped skis in it’s lineup. If I understand the links you provided, they should all be renamed “hyperbolic?”

http://www.exn.ca/Stories/1997/01/17/01.asp

9

what a pitch

if I skied at all

i would definately be on my way to get a pair of parabolas to strap on

I am now a better skier.

if I read that dicovery artickle again I’ll be even betteer.

If them surfboarrd makerrs ever get an artickle printed

written like that the water will be filled with experts in no-time.!

who needs math

put down the lettuce ,listen for the bell and out the door a better surfer!

dem it emmit where we gonna git some o’ them expert makin sports items

…ambrose…

hal and julia

the future is here and the future is us

future+ utility= futility

10

Someone should ask Greg why he used the term parabolic power system. I see Firewire is using it in their marketing, too, and to me it doesn’t make any more sense there either.

Parabolas are natural flight trajectories…accelerating in one direction, moving linearly in the perpendicular direction.

If you took a wide ski and cut a parabola out of each side, the result would not follow a hyperbolic set, though.

11

I don’t know the slightest thing about parabolas myself.

But I think my question still stands should anybody care to entertain it: What is it about parabolic rails that’s parabolic? What, if anything, is their parabolic quality?

You cannot know until you know what a parabola is bro.

Generally speking, a parabola is simply a 2D curve, usually symmetrical, defined by a simple algebraic equation, containing a squared variable. The general 2D shape of an egg can be perfectly defined by two or more parabolic equations. Trust me, you DONT want to know any further :wink:

‘Perimeter’ is a more accurate description.

‘Parabolic’ terminology used in sporting eq is marketing speak…‘parabolic’ sounds more interesting, technical and catchy than “curve” doesnt it?

Hey where can I find some of that ‘fabucor’ board building mat’l? That’s fabucor…like fabulous…what a gas!

But hey y’never know when the term could come in handy…

“hey now…doesnt she have a nice set of parabolas?”

hmm…Im starting to like it now.

12

actually a parabolic tail would make more sense, as a rounded pintail can resemble a parabola.

Parabolic rail cross-sections maybe, on an old school longboard.

But, most surfers a) don’t do math and b) will buy whatever is trendy, right?

13

It’s a parabolic curve only if the coordinates of the curve follow the parabolic formula

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

A more general expression might be to use a Bézier curve

http://en.wikipedia.org/wiki/B%C3%A9zier_curve

Or possibly a spline fit:

http://en.wikipedia.org/wiki/Spline_%28mathematics%29

14

Sorry, I forgot you mentioned skis another thing I actually know a little something about. But the thing about math is that it’s exact, if something doesn’t perfectly fit the definition of say a parabola or a hyperbola then it’s neither. I got caught up in being exact with what a parabola or a hyperbola are to really answer your question.

Maybe I shouldn’t have said that the butterfly board you mentioned looked like it had hyperbolic stringers. I don’t know how it was made. Could be two parabolas. Could be a kind of curve called a catenary (not a parabola or a hyperbola), which is what you get if you suspend the ends of a chain at an equal height. I -think- that you get a catenary curve if you use a piece of wood to draw a fair curve when the third nail/pin/clamp holding your wood is the same distance from the two on the ends, but don’t quote me on that.

As for skis, I’m not exactly sure what manufacturers do. I don’t think that they’re a hyperbola, could be parabolas. Probably just a marketing word. It gets complicated cause you have the curves on the sides and a curve on the bottom, a reverse rocker if you will. Then how the ski turns depends on what it looks like when it’s turned on edge and flexed. There’s been some folks making their own skis lately [frozen water stoke at www.skibuilders.com] and having good luck with just drawing a fair curve.

Hope that makes sense.

15

I think the “parabolic” reference in shaped skis is more to do with the lines you draw with them on the snow, than the actual shape of the ski itself. Although, due to abuse, the term “parabolic” is now synonymous with the shape of the ski. Equally wrong is the term “straight skis”. You would have to venture way back in history to find a ski with no side cut at all. Not that I would wish to go back to my old 200cm skinny arse sticks!

16

Conic Sections:

17

Whoa…

Dammit, I was talking about some pieces of wood around the edge of some surfboards and now you guys are bringing terrorism (Al Jebra) into it! I’m out of here!

18

anyway

cant get surfer fag here in nZ

can you post a few pics of the pros ridng

alchabolic comptech epochsie

so i can show all my sheepshagging kiwi mates what ive been raving about for the last year

is acutally come to pass

19

two Italians palying bocci ball in boston

Pair a bolas.

…ambrose…

I love the cones

20

Hmmmm…don’t know 'bout hyperbola…sounds like the plural of hyperbole…appropriate?