Kneeboard Surfing USA Community Forum

Rhetorical question, but I've been fascinated by the quality of the photos we are seeing on this site - and the way they describe not only how the water flows around our boards but also how our boards interrupt the flow of water...

As a starter here's a photo of Mark Slater by that surf God photog Slats.
I found it interesting the way the water is reacting with the back of the board - you can almost see the meniscus sucking the baord back into the water. And that water hanging on the inside edge of the fin .....



you can almost imagine it running along the bottom of the board, hitting the fin's inside edge and being redirected off the back of the board


just kidding with the poll

gooday Frank

something tells me there is something on the tip of your tongue

Book
Essential Surfing
George Orbelian

scary what knowledge is in there if you study it. Reread the section on fin hum last night.

Photos lie
They catch an instant when there may be a transition of state. You may see a board pushing water (all boards do, at some point) and conclude something about the design, even though the board hardly ever pushes water.

Videos can help - back forward back forward, etc. But you can only formulate armchair concepts - you still have to feel them on a board in the water and see whether other people feel the same things.

Hi Doctor Red

thanks for answering.. Good points .. Videos are very relevant but rarely are they so close and detailed. And bare in mind thay are just a collection of "instants'".. Of course what comes before and what comaes after are just as relevant as the instant of a still photograph - so you are right...

just had a nice two hour session by myself, (ie with all my friends)

and while I was in the water (dark murky cold full of suspicious looking carnivores with no names) I decided I'd better stick with surfing rather than eulogizing over a drip of water captured in time.

cheers

HW

by the way, do you mind if i call you doctor?

I've been wondering if "river waves" produced in a flume are an accurate model of ocean waves such that a laboratory environment could be created in which to test ideas about surf board design. I just don't know, though if the water speed required matches the board speed in the ocean. Any ocean engineers out there? Won't settle what's right for who, but allow comparison of different modifications on a theme. I've also thought about mounting a tiny camera inside the bottom of a board facing the fins so you could see what's happening around them in the water.

I'm such a geek.

They have wind tunnels for testing aircraft wings, why not water tunnels for testing board shapes? Other thatn the obvious moneyreasons.

not a geek

one of the ways of seeing how water behaves is to coat the bottom of your board with graphite and oil

the water patterns show up in the graphite


- I've bveen riding 14 mill concaves for about six years now.

I always assumed that they were deep enough to allow a flow of air underneath them.

Then one day I chose to look.

A little eyeball observation showed me that instead of a constant flow of air from nose to tail, the air travels in oval bubbles of air about eight inches by six inches (themselves bordered by discrete bubbles about the size of a walnut) .

this is when the board is planing rather than railing.

the faster you go the more chance of the bubbles joining up.

what good the bubbles? Think of how they might break up meniscus tension. Then look back at the photo in the first post..

Question eg: some say that a shallow concave makes a board harder to turn. Then why would a deep comcave make it easier to turn?

You can add all your senses to observing how a board works. EG I can hear the air coming out of the back of my board as it goes off the plane when I flick off in a flat section.

I am a geek too..

Who cares?



Kage

you can always get some hydrodynamics student to test a board for his final year topic

..

good point

consider those silver fcs fins with no rake

fast but maybe usless for drawing curves

We do have water tunnels to test board designs.

Sometimes they are called "TUBES".

It's a popular term used by surfers.

I've been designing and testing kneeboards since I was 12 years old.
I'm 51 now. (do the math).

30 years worth in Hawaii, where there's surf on all sides of the islands all year long.
The Banzai Pipeline is a great water tunnel type place to test a design.
Arguably one of the best places to find out what works or doesn't.
If it doesn't you could die!


We also traveled to some of the best places on the planet to test them.
Like Jeffrey's Bay, Peru and Indo.

G-Land is another water tunnel type wave that makes for a great test.



We also spent exhaustive amounts of time riding average surf to just plain junk surf testing designs.



Imagine how much testing went down for the last 30 plus years in a location that virtually never goes flat.
(Not to mention the money spent. )

hello Bud

nice to see you back

great comments but was it logical objective testing?

Here is one of the factors used in our kneeboard testing:

C20H25N30

(the numbers should be subscript...sorry)

who needs rugs when I have incohol? err alcolcol... I mean grog.

concaves - who needs em?
Jet bottoms are the go (art meets surfboards):
http://www.swaylocks.com/forum/gforum.c ... ead#unread

Sorry about the wide line for the link above
Just joking about the concaves - really!

Andrew, it's drred actually, but it's not official until the fat man sings
5 years of rabid study. Now I can really get into board design... (spoon project heating up)