ssd sailboards sick nothing like it on the market get one youl see

either picked it out of season or didn't cook it enough.

Seriously though, if I didn't make my own boards, I'd probably get Mark to make me one. Either him or Blue Juice.

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Originally posted by Juice

Thankyou Decrepit for your compliment.

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I've only seen a few of your boards down here, but they looked good.

Being a surfer and professional surfboard maker from way back, I believe in the local custom tradition, even if I have to pay a bit more, I prefer to support the local product, especially if I can have some input into the boards design.

Same goes for sails, that's why I'm prepared to wait several months for Bugs to get round to making me a sail.

the willis bros "phazer bottom" is the golf ball dimple thing.

i remember seeing a few surfboards around in the 80's and i think also morey boogie used it on their boards too.

Wow, both those boards Are beautifully crafted.

Really good link
I wonder if they actually have an effect.

I think the other area on a windsurfer that could be looked into would be where the fin meets the board.
A cowl, like they have between fuselage and wing would be a good thing to have.
Also 'winglets' on the end of the fins to reduce induced drag.

And a forward sweep fin, I wonder what that would do?

www.fortboise.org/windsurfing/spinout.faq.html

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Originally posted by The Grinch


And a forward sweep fin, I wonder what that would do?

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From my experience, they generally dont work for plaining board - although I'm not sure about sub-plaining or very high rake angles (ie: like weed fin, but back to front).

There are some fins where there is very little rake; when combined with the AoA of the board, the tip of the fin is forward of the base. The end result is that they are very twitchy and spin-out very easily. And in some cases you can feel the fin vibrate just before it lets go.

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Originally posted by The Grinch


That would make sense..I could imagine they would be very unstable.

What fin end plates? Have you had any experience of those?

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nope. I do understand some of the theory behind why it has an advantage in a compressible medium (air), but I'm not sure about water. I'd imagine that it would help remove some tip vorticity's, but at the expense of extra drag -> might has well have a longer fin which produces no lift from the tip. One expectation would be that since lift is proportional to speed, you would need a bigger end-plate for a higher speed.

And relatedly. Non-carbon wave fins have their tip twist off very easily -> you are often able to bend it with your fingers; while carbon fins tend to be *very* stiff for their whole length. I have wondered if it would be possible to make a fin that the base is 100% carbon up to about 50% its length, progressing to the tip where it is 0% for about 10% of its length (think a bit like sail twist). Most fins at the moment do this by reducing thickness and/or area to remove material -> with such a layup, you might be able to keep the area and thus reduce the total length. But what do I know... just speculating.

"Wave Scalpel" sailboards and l, "Stone Surfboards", shaped dimple bottom boards for a number of years in the 80's. Shane Ocallahan ,"Wind Energy" got the idea in Maui l think, told us. They loosened up the board under the front foot, made it feel a bit quicker at the expense of drive.Reasonably easy to do, and popular at the time. It was before concaves really kicked in.

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Originally posted by The Grinch


As an aside decrepit, since you have board design experience have you ever tinkered with planing surface texture?

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Well I've only had polished and 400 wet and dry finishes, but I've never done any tests to see which is faster.
There's a long thread in the speed section about it. The golf dimples are mentioned, not very favorably.
www.seabreeze.com.au/forums/topic.asp?TOPIC_ID=28486&whichpage=1

here comes mike on his invisable board.....

do do do do do do doo doo do doo do doo

WONDER WOMAN

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Originally posted by Juice

Basically dimples on a golf ball work by reducing the area of turbulant air and the subsequent friction behind the golf ball, by maintaing the laminar flow a lot further past the mid section of the ball. I doubt that principle would work on a sailboard.

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Its is my understanding that this is not entirely accurate - dimples *increase* turbulent flow, with as you said, the effect of reducing drag.

There are two types of foil flow, laminar and turbulent - such that laminar is the effect of having a thin boundary layer at the surface, whereas turbulent is often an order of magnitude thicker flow and also more disturbed. The actual definition is little more complicated as the turbulent flow cross-section could be regarded as laminar, if you took a big-picture look at the flow.

In the case of a foil such as a fin, laminar flow is required as it generates more lift than turbulent. Since the water flow follows the fin surface, it joins back together with the flow from the opposite side, resulting in a low drag component.

On a golf ball the back edge is much too curved to maintain laminar flow and so the air detaches creating a very high drag component. By using a thicker less-attached air flow, less air is sucked behind the ball, thus reducing drag.

This all depends on foil size, fluid viscosity, speed, etc. Or at least some of the books say that... ;-)

And I guess you don't want to volunteer for rigorous scientific testing to find out?????

Mathew thankyou for your correction I'm always keen for knowledge. I believed that the dimples caused the air to hold on for longer at the back edge of the ball which I though was laminar flow. I totally agree with what you wrote, my wording about the idea of less air being dragged behind the ball was probably not as descriptive as yours

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Originally posted by WINDY MILLER

here comes mike on his invisable board.....

do do do do do do doo doo do doo do doo

WONDER WOMAN

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The phazors or dimples were deepeper at the front (4mm), and came up smooth at the back to the original bottom line. The outline was eggshaped. Little pockets of air would form at speed, causing a bit of cavitation in cotrolled areas of the board unsticking it slightly, hence loosening it like how a fin spins out. You definently lost drive under your front foot, ie when you look for speed forward on your front foot , the board would tend to slide a bit sideways..Surf boards are much slower than sailboards though.
With golfballs, is not their pattern also to help them go straight, the ball will be continually spinning.