dimple thread,I thinking of having the bottom of my next board designed with this pattern will it go fast?
on a cold winters morning my sack looks like a golf ball...
then again when I adjust the scientific and aerodynamics of it,it really is more of a walnut ....
I have the opposite issue Chrispy, lots of blokes brag about having large old fellas.
well I am not blessed in that department, however, I have massive nuts.
No walnuts in my sack, more like golf balls, dimples and all.
ET.
Select to expand quoteMacaha said..
dimple thread,I thinking of having the bottom of my next board designed with this pattern will it go fast?
no your not
There's no advantage in the case of surfboard hulls, the topic has been covered extensively on Swaylocks and elsewhere.
Can explain why if you like.
Like the man said they make no differnce better to look for a concave if you want to go faster
Select to expand quoteRoyStuart said...
Can explain why if you like.
I would like to know Roy
Select to expand quotevanders1 said..
Just pm him Roy, the rest of us don't care.
Rude. I would like to know as well please.
Select to expand quotegenuine said..vanders1 said..
Just pm him Roy, the rest of us don't care.
Rude. I would like to know as well please.
Ok pm genuine too Roy.
Roy when you do explain the golf ball thing, just for my benefit Roy, please put a dictionary link after each big word. .............
Ok so it's settled, pm's for Cobra, genuine, SandS and include descriptions and meaning for the big words, simple.
Ok to the best of my knowledge this is how it goes:
A smooth golfball has laminar flow initially, this is a low drag situation with virtually no turbulence. The laminar flow is easily disturbed though and once the air flows to the low pressure zone at the back of the ball it suddenly becomes chaotically turbulent and separates from the back of the ball, leaving a wide turbulent wake behind the ball which is high in drag.
A golf ball with bumps does not have laminar flow, the bumps create turbulent flow immediately but the turbulent layer is thinner and more controlled. This turbulent layer stays attached for longer as it flows around the ball, and when it separates it does so leaving a narrower lower drag wake. The net result is lower drag overall.
It's the low pressure area behind the ball which causes the flow to separate in both cases.
With a surfboard hull the situation is quite different as the pressure all over the hull is higher than the surrounding water pressure, so there's no problem with flow remaining attached.
With a clean smooth surfboard hull there's a short section at the leading edge of the wetted surface area which has laminar flow but it soon breaks up into turbulent flow. There's theoretically an advantage top be gained by inducing the turbulent flow in a managed way before it does so naturally as the turbulence is kept to a thinner layer and is thus lower in drag. Mini vortex generators can be used to do this.
This fellow explains it better:
"Just to clear up why the dimples work on a golf ball, and not on bigger slower things like boats....
See the attached image. This is a classic system found in all fluid mechanics texts, and one that an amazing number of students fail on their Fluids II midterms.
The dimples induce a slight bit of turbulence in the boundary layer- the very thin film of air that is right against the surface of the object. With a laminar boundary layer, the flow would travel in smooth layers, and would separate from the ball very close to the leading edge in order to maintain these smooth layers- leaving a huge, turbulent wake behind. A slight bit of turbulence in the boundary layer delays the separation, allowing the flow to remain in relatively smooth contact with the ball until somewhere along its trailing face- thus, when the flow does break from the ball, the turbulent wake is much smaller.
It's not a complicated system, but it is important to distinguish between turbulence in the boundary layer and turbulence in the wake. A slight increase in the former, for a golf ball, greatly reduces the energy dissipated in the latter.
The spin on a golf ball is not intended for reducing drag. What it does is to induce a slight circulation around the ball, which results in a net upward force (a lift) on the ball. This effect is not nearly as intuitive as it sounds and some reading on potential flow theory is required to understand why it works. But in the end, the lift comes at the expense of the rotational inertia of the ball, and so while the spin slows down in flight, it spends more time in the air and so goes farther.
Now to a boat. Unless you're sailing a harbour tug, you do not have separated flow on the underside of the boat to begin with. And you're not in the same Reynolds number regime as a golf ball. So the increase in skin friction you get by forcing a turbulent boundary layer is not offset by a decrease in the energy dissipated in a separated wake, because there is no separated wake to begin with.
Predatory sharks, AC yachts and other high-tech marine systems sometimes use tiny ridges and other structures on the skin of the animal/boat. Exactly how they work is the subject of a lot of research right now; essentially, they are manipulating the boundary layer to provide the right combination of laminar and turbulent properties for the pressure gradient in a particular area. Simply slapping the stuff on has no benefit without knowing what it's doing to the boundary layer in which area."
www.boatdesign.net/threads/golf-ball-boat-install-a-dimple-plate.20413/
What part of 'pm' was not understood???
You certainly won't get any favour with Scotty with posts like that.
Select to expand quotevanders1 said..
What part of 'pm' was not understood???
No one's taking orders from you that's what's happening, it's not a reading comprehension issue.
Select to expand quotelaceys lane said..
do chicks with dimpled legs run faster,
well do they
Hmmmmmmm well I'm going to say yes particularly if The Stud Macaha is in town
Select to expand quotevanders1 said..
Just pm him Roy, the rest of us don't care.
Well the rest of us don't care reading about the gold coast mothers club meeting for coffee every week but we tolerate
Select to expand quoteCobra said...vanders1 said..
Just pm him Roy, the rest of us don't care.
Well the rest of us don't care reading about the gold coast mothers club meeting for coffee every week but we tolerate
Don't feel left out mate, you know we'd accept you if you were here.
hey cobra is that avitar the butcher from the aunty jack show ? kev cabana was it ?
Select to expand quote
Cobra said..
vanders1 said..
Just pm him Roy, the rest of us don't care.
Well the rest of us don't care reading about the gold coast mothers club meeting for coffee every week but we tolerate
cobra awakes
Select to expand quotelaceys lane said..
do chicks with dimpled legs run faster,
well do they
No they have usually have too much drag around the rear end
Select to expand quoteRicardo1709 said...laceys lane said..
do chicks with dimpled legs run faster,
well do they
No they have usually have too much drag around the rear end
Strap a tunnel fin to em mate, apparently it makes them a much better ride.
My water ski has them. It also has small channels down the rails.
Couldn't see them working on a board. This thing is skitish but so fast
Select to expand quotelaceys lane said..
do chicks with dimpled legs run faster,
well do they
And they definitely do when ya chase 'em round the house starkers with a horse tickler in one hand and a bagel in the other champion
