Forward fins set vs. less forward fins set

[albert]

On my retro board it did seem to lift the tail up a little, I just had troubles with it when I would try to push down on the board to get to the bottom once I had speed. It didnt seem to want to let me push down the face of the wave to the bottom as easily as I would like. but it did add a little stiffness to my retro board which it was in dire need of.

[red]

Came across this on a windsurfing site. Talks a lot of sense about fins.

"The foil shape is the most important consideration. two thirteen inch fins with the same plan shape and area but with different foils may look the same but will perform differently. Probably the easiest thing to consider is the maximum thickness as a percentage of the cord length (width of fin). This will give a rough guide to the foil type, for example a fin with 100mm cord length and a thickness of 10mm has a thickness ratio of 10%. If you compare this with a fin of 80mm cord length and 10mm thickness the ratio is 12.5%. Generally the higher the percentage the more lift the fin generates for its area. The thicker foil of 12.5% although it generates more lift it generates slightly more drag, but the efficiency can be increased or drag reduced by shortening its cord length, so our fin of 80mm cord length generates as much lift as the 100mm cord length fin because of the shorter cord length and reduced drag, essentially we have increased the fins efficiency there are also other benefits. A shorter cord is easier to jibe and less likely to overpower in the gusts. It also flexes more which gives better control in the chop and in gusty conditions. So are there any advantages with the 100mm cord length fin? Yes, it has more lateral resistance which gives good performance in light winds but once its speed increases its efficiency decreases and it becomes slow compared with the shorter cord fin. It will also overpower quickly and tend to drive the board up out of the water and will be more difficult to jibe.

Lets go back to our fin with the 80mm cord length and give it a thickness of 10%. Now you will find that it does not generate enough lift until it is travelling at high speeds. It will be very fast with a good top end and excellent off the wind. But you will probably require an extra inch in length, to have enough holding power. It would also be very hard pointing high up wind.

Stiffness... A property frequently overlooked , stiffness is the most important after foil shape. Two fins of identical shape but different flex characteristics will effect the performance of a board in the following way. A fin that is too stiff will give the board a rough ride and in choppy water will overpower more quickly. It will be more prone to spinout and will give little warning of impending disaster. A fin with too much flex will handle the chop well but will be hard to get on to the plane and will have a lower top end speed. Ideally the fin should be stiff in the base and be flexible in the tip. "
http://www.finco.com.au/FinSelect.htm

[ross]

red
do you reckon that a more flexible fin could be used in larger surf where a little extra drag is less of a hinderence?
ross

[red]

Ross,
I have no idea about fins and flex. I'm one of the sheep following, herd minded kneeboarders. I ride conventional (finely honed, but conventional all the same) equipment and just want to do one perfect turn befor the knees or ticker gives out.
But wasn't narrow, flexible fins Greenough's philosophy that started the shortboard revolution?

[DrStrange]

GG's fins were relatively narrow when revolution started. Pretty wide base with taper outline and rake and flex. As time passed he narrowed them to the extreme testing the limits.

[Bob]

First of all, regardless of what you ride in good surf, everyone should have a big, wide Aussie "platter" board as I call them, for small surf. I bought a used Parkes and "wow" on small mushy days.

Here is my question: How come when the fins are placed forward, when you are coming off the top or doing a cutback, it feels like you are pushing on a pillow as compared to the snap of a "fins farther back" board? I am placing no judgement here. I enjoy both types of boards. I am just wondering.

[hart]

Here is my question: How come when the fins are placed forward, when you are coming off the top or doing a cutback, it feels like you are pushing on a pillow as compared to the snap of a "fins farther back" board?

Bob

I saw this question this morning and now I am looking at it again, at the end of the day.

No-one has commented.

It's enlightening to hear that you can see the advantage of the OZ "fin-forward" approach that you mention..but also the drag backwards..

(pillow biting)

Forward placement of fins allows unrestrained pivot. No doubt.

Good for crap waves? Sure..no doubt, again.

But unbridalled pivot can be good for good waves too



(noting Farrer in the upcoming video footage of NSG 2005 surfing a six- foot-eight)

So why did Australian Kneeboards grow so long?

It's just that with a little more railfoil (and the entry it provides to aid fin-control) combined with a little more length thru the bottomline, the pivot-point of a board can be elongated

And if you add a touch of curve (class)

a new World can be your Oyster!

hart

curve, class and brass (too Sydney)

ps

apologies for all the OZ faux pas..it's Coopers induced

[john -]

[quote="hart

And if you add a touch of curve (class)

[/quote]


does that suggest a skilled surfer handles/enjoys more curve?

and if so does Farrer call his boards Marilyn

[hart]

Norma Jean Baker had far too many curves for any one man..

So beautiful, yet so vulnerable

She devoured sports stars and US presidents alike..whether they knew it, or not



and if she were a surfboard?

she would do the same



hart

"..even though I never knew you at all

"you had the grace to hold yourself,

"when all around you fell.."

Taupin

and no other mere mortal, would get it so right

[Bob]

Thanks! Now for more reseach and development...if the wind and swell ever cooperate.

[Bob]

Thanks! Now for more reseach and development...if the wind and swell ever cooperate.