Bjorns, Antoines and Pascals make sails very fast.

Given the historical data on hand, big focused males from the northern hemisphere is the answer.

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Brent in Qld said..
Bjorns, Antoines and Pascals make sails very fast.

Given the historical data on hand, big focused males from the northern hemisphere is the answer.

Give Anders his dues also, first past 50 if I am not mistaken... also from the NH but maybe not quite as big or did he beef up a bit?

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cald said..

Brent in Qld said..
Bjorns, Antoines and Pascals make sails very fast.

Given the historical data on hand, big focused males from the northern hemisphere is the answer.

Give Anders his dues also, first past 50 if I am not mistaken... also from the NH but maybe not quite as big or did he beef up a bit?

Fair call, Anders was a speed demon without doubt. From memory 2m-ish & 110+/- kegs and the first windsurfer to average 50+knts over 500m.
R E A L F A S T

Don't forget our locals.... Slowey and Spotty both hit a gps 50 very early on. Two very different styles to suit their body sizes.

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LeeD said..
A wave sail pilted by a great sailor will always be faster than any race sail piloted by a good intermediate sailor.

"Always", is a big statement - And wrong!

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decrepit said..
fastest = best lift to drag ratio in the hands of a windsurfer.
It's all about the max power the sailor can hold, reasonably comfortably, with minimum drag.

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roo said..

A fast sail is all about stability and control, coupled with useable power and less drag. Nowadays as materials and technology have progressed the same principles apply but sail shape has changed to better utilise more stable carbon masts and material that stretches less. Twist also came into play, again as a direct result of ADTR testing. Back in the 1980s Marchaj was the authority and elliptical lift distribution was the mantra. That changed with twisting foils and bell shaped lift distribution is way more efficient. Cambers in the deep power section of the sail are used to stabilise the foil shape while the upper section of the sail is twisted off creating proverse yaw and also reducing drag at the tips and the resulting tip vortices.

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madge said..
A FAST sail will only go as quick as the board that its driving.

Partner them both together and then with a good sailor too and the right conditions and you have the fastest sail.

on any average day a Fast sail will :
one with good shape.
A mast that matches the sails best profile.
A good stiff boom.
Newer the better.
Rigged right.
Sailed to its best potential in the right winds strength.

There you go: Summarised for you. That pretty much says it all.

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Ian K said..

Possibly because sails have evolved to deal with the ever-present real world turbulence. (en.wikipedia.org/wiki/Law_of_the_wall )

When you run a truck at speed through relatively still air you eliminate turbulence.

Sorry if this is a numpty question Ian, but say a sail is undergoing turbulent conditions (eg vertical orientation at Lake George with Daisy giving it the beans on a bare away), how does going fast relate to the law of the wall ?. Is the wall the sail ?. How can you use this log law to improve a sail design ?

The "Law of the Wall" is tied up with the logarithmic wind profile. Probably called a "law" because you can't get away from it. It's everywhere. And Von Karman who came up with it has the universal constant K =0.4 named after him. But it's not all that constant and there's always re-evaluations being presented between K = 0.39 and K = 0.41.

Turbulence hasn't been properly explained yet but a simple ( mostly wrong ) interpretation of K, the universal constant, is that eddies mix up or down in the flow typically jumping a "mixing length". Which might be K times the height from the wall. So the tip of your sail at 4.5 metres typically gets hit by gusts coming down from 6 metres or lulls coming up from 3 metres.

You can muck around with the algebra and use this idea of a mixing length that's proportional to the distance from the wall to deduce a logarithmic profile.

But in practice you need to average a vertical array of anemometers for quite a while for a logarithmic profile to emerge. A bit less than 50% of the time your 2 metre anemometer is going to be reading more than your 4 metre anemometer and vice versa.

Doesn't relate directly to making your sail go fast but sails evolved with the best balance of twist and flex to deal with this mess. The sail will develop its own boundary layer. A smaller scale version of its "Law of the Wall" superimposed on what it is passing through.

Is the 'Wall' some upstream construction that is creating the turbulence? What the hell is the Wall?

BTW. In my humble experience, the turbulence of the wind varies greatly depending on the upstream land profile. Sandy Point WSW now behind the growing dunes,= Huge turbulence. Lake George down near Cockies in a SE High pressure gradient wind = very low turbulence. Sandy Point WSW in 1980 to 2006 = pretty low turbulence, depending on the particular air mass. Luderitz speed canal with gale force wind coming over hilly terrain for many miles = extreme turbulence. I don't think any sail can be, or has been designed to work perfectly in that whole range of conditions.

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sailquik said..
Is the 'Wall' some upstream construction that is creating the turbulence? What the hell is the Wall?

BTW. In my humble experience, the turbulence of the wind varies greatly depending on the upstream land profile. Sandy Point WSW now behind the growing dunes,= Huge turbulence. Lake George down near Cockies in a SE High pressure gradient wind = very low turbulence. Sandy Point WSW in 1980 to 2006 = pretty low turbulence, depending on the particular air mass. Luderitz speed canal with gale force wind coming over hilly terrain for many miles = extreme turbulence. I don't think any sail can be, or has been designed to work perfectly in that whole range of conditions.

Yes they use a term called "roughness length" to try and allow for it in the logarithmic profile equation. But then for the equation to have any hope of working the level of roughness has to have been the same for a good distance upwind. Waves in open water appear to be in some sort of harmony with the wind and aren't as rough as their size suggests as far as affecting the wind goes. An atmospheric scientist fellow ,who was also a windsurfer, told me once that that was the reason onshore wind on the inside at a surf beach is lighter. The waves, once broken, lose that harmonious shape and have a bigger effect on the wind.

en.wikipedia.org/wiki/Roughness_length

Oh the wall is the surface over which the wind is blowing. Maybe Von Karman had his pitot tubes mounted on the wall of his wind tunnel when he came up with the term? Maybe it just sounds more poetic that any other surface he could think of.

I'm a picture man Ian. I sure could use some diagrams . I'm still a bit confused about what a Wall is. Is a boundary layer of a sail contouring the sail, or is it normal to it ?

"roughness length". Is this similar to wind gradient effect ?

That's an interesting effect about onshore winds. I didn't think about it like that.

Here you go JN. Even got the wall labelled!


You can see how eddies are larger further from the wall. And the boundary layer progressively thickens as you get further back from the leading edge of the wall. Your sail is passing through the boundary layer associated with the water surface but it will generate a boundary layer within a boundary layer. You can't have the large eddies with the higher speeds at 3 metres directly on the surface of your sail. Smaller eddies will be generated to slow it down. Not that there are no small eddies up high. Big eddies rub together to produce them also. Here's the famous old poem that still pretty well summarises all we know about turbulence.

Big whorls have little whorls
That feed on their velocity,
And little whorls have lesser whorls
And so on to viscosity.

-- Lewis F. Richardson

Thanks Ian.

Here is what my simple, practical mind visualised when you mentioned turbulence and a Wall:







Very relevant to sailing in SW'ers at Sandy Point these days.

Here is another variation that is relevant in a lot of places:

Thanks Ian. That makes it clear.

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Roo said..
A fast sail is all about stability and control, coupled with useable power and less drag. It was what we found testing sails on the ADTR when developing Pascal Maka's speedsail that he first broke the world sailing speed record with back in the 1980s. Nowadays as materials and technology have progressed the same principles apply but sail shape has changed to better utilise more stable carbon masts and material that stretches less. Twist also came into play, again as a direct result of ADTR testing. Back in the 1980s Marchaj was the authority and elliptical lift distribution was the mantra. That changed with twisting foils and bell shaped lift distribution is way more efficient. Cambers in the deep power section of the sail are used to stabilise the foil shape while the upper section of the sail is twisted off creating proverse yaw and also reducing drag at the tips and the resulting tip vortices.

Roo, what does ADTR stand for ?

.... testing range?

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JCBoston said..

Roo said..
A fast sail is all about stability and control, coupled with useable power and less drag. It was what we found testing sails on the ADTR when developing Pascal Maka's speedsail that he first broke the world sailing speed record with back in the 1980s. Nowadays as materials and technology have progressed the same principles apply but sail shape has changed to better utilise more stable carbon masts and material that stretches less. Twist also came into play, again as a direct result of ADTR testing. Back in the 1980s Marchaj was the authority and elliptical lift distribution was the mantra. That changed with twisting foils and bell shaped lift distribution is way more efficient. Cambers in the deep power section of the sail are used to stabilise the foil shape while the upper section of the sail is twisted off creating proverse yaw and also reducing drag at the tips and the resulting tip vortices.

Roo, what does ADTR stand for ?

.... testing range?

AeroDynamicTestRig

Given the same sailor, board and sail size
my guess would be.

The Aspect ratio of the sail and the
drag coefficient of the sail.

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windfred said..
Given the same sailor, board and sail size
my guess would be.

The Aspect ratio of the sail and the
drag coefficient of the sail.

For slalom and speed windsurfing, a lower AR of the sail has proven to be faster to some extent:
As Decrepit said at the strat of the thread: Best Lift to Drag ratio that the sailor can hold/control.
And within those low'ish aspect ratio sails, the centre of effort has also lowered over the years as flatter twisted heads have evolved.
The lower position of the C of E, can allow the sailor to harness more power in a vector more directly in line with the direction of travel.

Strange the new NP foil race sails have the highest AR of their entire line.

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LeeD said..
Strange the new NP foil race sails have the highest AR of their entire line.

Look at the IQFoil sails

They are 530cm masts with 232cm booms at 9.0. Definitely high aspect but also very fast/stable.

They just copy NP's lead.
Most just buy the new NP by late summer, crash course design a copy, make 3 protos, try it, and order it for production ASAP.
Everyone in the KNOW......knows this

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LeeD said..
Strange the new NP foil race sails have the highest AR of their entire line.

Not strange. Foiling is different. Thats why I specially stated "Slalom and speed Windsurfing".

So when we are talking ADTR is a standard mono film faster than a scrim sail .not that they make many scrim race sails .

so are smother surfaces more aero dynamic or would a scrim being more stronger and less give have more power ,if power equals speed .

just a thought ,

Are YOU sure of what you say?
Low AR of slalom pros is not about speed, but about quickness thru a course with multiple jibes.
Speed is mph, kph, or however you measure of TOP SPEED, not easy jibing or acceleration.

ADTR was abandoned by 1989.
Yes, Gaastra sails were VERY fast, but only within a defined wind range.

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LeeD said..
ADTR was abandoned by 1989.
Yes, Gaastra sails were VERY fast, but only within a defined wind range.

are you sure what you say ,GA (gaastra) sails are still pretty quick ,and wind range is good .

Yes, I am sure.
ADTR was not relevant after 1989. Twist sails came out in 1986, and slowly took over racing because a rider can hold .7 to 1.5 bigger when sails twisted off, something you need when racing in a pack.
Gaastra Regional team rider, 1985 to 1989.

My current Gaastras are 2018 Matrix 5.5.
2017 2 cam 6.7.
2016 3 cam 7.5.

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Tardy said..
So when we are talking ADTR is a standard mono film faster than a scrim sail .not that they make many scrim race sails .

so are smother surfaces more aero dynamic or would a scrim being more stronger and less give have more power ,if power equals speed .

just a thought ,

Tardy the monofilm sails retain their shape over a longer period of time in use, they don't stretch. If they have no UV protection the mylar breaks down and ultimately fails. Ultimately smooth surfaces have less drag but you would have to get rid of batten pockets and stitching which wouldn't be practical.

THE ADTR was not abandoned, Gaastra was sold and the funding for the project dried up. LeeD sometime you have no f^&*(%g idea. A regional racer is a nobody in the professional racing world. Stop trolling and spend your time doing something useful for a change.