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Mark _australia said..
Any minute - wing sails.

3 - 2 - 1 ...........

^^^ + 1 Cmon Wing11 fess up. Your buddy is MW ? OR are you MW?

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Wing 11 said..
@chris249
Nobody said the wind shear do not exist,just that wsurf sail is to small to feel sinigficinat differnece in wind speed,this 3-4m difference in height is to small...

@Madge
"The wind speed at the front of the mast will be exactly the same at the top or the bottom of the sail."
I agree with you...

Did you ever have measurment at higher altitudes ,30m etc, how much is there differnece in speed, compare to bottom?


@al planet


In this few senteces ,evertyhing about wsurf twist is well done explain.Straight to the point.

Where you find this text ,link?

iwindsurf.com/forums/viewtopic.php?t=30174

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Wing 11 said..
@chris249
Nobody said the wind shear do not exist,just that wsurf sail is to small to feel sinigficinat differnece in wind speed,this 3-4m difference in height is to small...

@Madge
"The wind speed at the front of the mast will be exactly the same at the top or the bottom of the sail."
I agree with you...

Did you ever have measurment at higher altitudes ,30m etc, how much is there differnece in speed, compare to bottom?


@al planet


In this few senteces ,evertyhing about wsurf twist is well done explain.Straight to the point.

Where you find this text ,link?

Hang on, you still haven't provided any evidence that the shear is too small to be felt over a windsurfer rig. You are relying mainly on one source (Frank Bethwaite) that doesn't say what you imply, and ignoring other sources, including professionals in aerodynamics (which Frank, with due respect, was not). Marchaj's plot, for example, is much more detailed than Frank's claim and it shows considerable wind shear between zero metres and 4.5 metres. The pic above seems to show a Star class mast. Knowing the dimensions of the Star mast and eyeballing the position of the wind indicators, it appears that there are several degrees of visible twist within a span of about three metres. That's enough to be very significant.

Professor Richard Flay of the University of Auckland, one of the aerodynamics experts involved in the team that has won the America's Cup for New Zealand, is well respected by the other America's Cup designers and engineers I know. The paper I linked to earlier explains that shear is so significant that you really need a twisted flow wind tunnel (ie one that simulates shear) to allow accurate downwind sail testing.

In that paper, Flay includes two diagrams showing shear. He also notes that "most of the twist occurs at lower levels" and that for IACC boats, twist was very important downwind but not upwind (perhaps partly due to upwash) or to the way IACC boats are trimmed.

So we still have, on the one side, people who study wind for a living, people who do racing yacht wind meters and VPP integration for a living, America's Cup winning sailmakers and meteorologists all saying that there is significant shear. On the other hand we have...........



PS - The quote Al posted, by the way, refers to the apparent wind wind shear you say doesn't exist, so if you're saying it's well done then you are agreeing that there is significant shear.

By the way, contrary to an earlier quote, a floppy leach is probably not like a winglet or endplate. A floppy leach seems to basically be what wing designers call "washout", which is the opposite of a winglet. Washout reduces lift at the tip, winglets increase it.

It would be interesting to find out more about how washout and floppy leaches work in sails.

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Chris 249 said..

Wing 11 said..
@chris249
Nobody said the wind shear do not exist,just that wsurf sail is to small to feel sinigficinat differnece in wind speed,this 3-4m difference in height is to small...

@Madge
"The wind speed at the front of the mast will be exactly the same at the top or the bottom of the sail."
I agree with you...

Did you ever have measurment at higher altitudes ,30m etc, how much is there differnece in speed, compare to bottom?


@al planet


In this few senteces ,evertyhing about wsurf twist is well done explain.Straight to the point.

Where you find this text ,link?

Hang on, you still haven't provided any evidence that the shear is too small to be felt over a windsurfer rig. You are relying mainly on one source (Frank Bethwaite) that doesn't say what you imply, and ignoring other sources, including professionals in aerodynamics (which Frank, with due respect, was not). Marchaj's plot, for example, is much more detailed than Frank's claim and it shows considerable wind shear between zero metres and 4.5 metres. The pic above seems to show a Star class mast. Knowing the dimensions of the Star mast and eyeballing the position of the wind indicators, it appears that there are several degrees of visible twist within a span of about three metres. That's enough to be very significant.

Professor Richard Flay of the University of Auckland, one of the aerodynamics experts involved in the team that has won the America's Cup for New Zealand, is well respected by the other America's Cup designers and engineers I know. The paper I linked to earlier explains that shear is so significant that you really need a twisted flow wind tunnel (ie one that simulates shear) to allow accurate downwind sail testing.

In that paper, Flay includes two diagrams showing shear. He also notes that "most of the twist occurs at lower levels" and that for IACC boats, twist was very important downwind but not upwind (perhaps partly due to upwash) or to the way IACC boats are trimmed.

So we still have, on the one side, people who study wind for a living, people who do racing yacht wind meters and VPP integration for a living, America's Cup winning sailmakers and meteorologists all saying that there is significant shear. On the other hand we have...........



PS - The quote Al posted, by the way, refers to the apparent wind wind shear you say doesn't exist, so if you're saying it's well done then you are agreeing that there is significant shear.

Madge has proven,he measured on sail rocket ..

AL planet post,refers to change in apparent wind because of wind gust(when true wind increase velocity=apparent wind move more aft ),not refers to wind shear...
floppy head act like flag or weather vane,point in direction into apparent wind,so head addapt to apparent wind all the time but now lift on head is zero..But if gust hit too hard(especillay on dowind course),apparent wind move to aft too much so head can not open that much,then head also produce some lift..
shifting apparent wind is much bigger because of wind gusts compare to wind shear

washout decrease lift,winglet and end plate increase lift, but all decrease induce drag/vortex drag making wing/sail more efficient...

Gotta say when I posted the quote I wasn't super impressed by the explanation as the top of a floppy sail probably doesn't behave like the end of a plane wing but beyond that its probably way to complex for me beyond knowing that the sails I used back in the eighties were all pretty ordinary. In fact I think they got a lot worse (heavier and more expensive) before they finally improved.

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Wing 11 said..

Chris 249 said..

Wing 11 said..
@chris249
Nobody said the wind shear do not exist,just that wsurf sail is to small to feel sinigficinat differnece in wind speed,this 3-4m difference in height is to small...

@Madge
"The wind speed at the front of the mast will be exactly the same at the top or the bottom of the sail."
I agree with you...

Did you ever have measurment at higher altitudes ,30m etc, how much is there differnece in speed, compare to bottom?


@al planet


In this few senteces ,evertyhing about wsurf twist is well done explain.Straight to the point.

Where you find this text ,link?

Hang on, you still haven't provided any evidence that the shear is too small to be felt over a windsurfer rig. You are relying mainly on one source (Frank Bethwaite) that doesn't say what you imply, and ignoring other sources, including professionals in aerodynamics (which Frank, with due respect, was not). Marchaj's plot, for example, is much more detailed than Frank's claim and it shows considerable wind shear between zero metres and 4.5 metres. The pic above seems to show a Star class mast. Knowing the dimensions of the Star mast and eyeballing the position of the wind indicators, it appears that there are several degrees of visible twist within a span of about three metres. That's enough to be very significant.

Professor Richard Flay of the University of Auckland, one of the aerodynamics experts involved in the team that has won the America's Cup for New Zealand, is well respected by the other America's Cup designers and engineers I know. The paper I linked to earlier explains that shear is so significant that you really need a twisted flow wind tunnel (ie one that simulates shear) to allow accurate downwind sail testing.

In that paper, Flay includes two diagrams showing shear. He also notes that "most of the twist occurs at lower levels" and that for IACC boats, twist was very important downwind but not upwind (perhaps partly due to upwash) or to the way IACC boats are trimmed.

So we still have, on the one side, people who study wind for a living, people who do racing yacht wind meters and VPP integration for a living, America's Cup winning sailmakers and meteorologists all saying that there is significant shear. On the other hand we have...........



PS - The quote Al posted, by the way, refers to the apparent wind wind shear you say doesn't exist, so if you're saying it's well done then you are agreeing that there is significant shear.

Madge has proven,he measured on sail rocket ..

AL planet post,refers to change in apparent wind because of wind gust(when true wind increase velocity=apparent wind move more aft ),not refers to wind shear...
floppy head act like flag or weather vane,point in direction into apparent wind,so head addapt to apparent wind all the time but now lift on head is zero..But if gust hit too hard(especillay on dowind course),apparent wind move to aft too much so head can not open that much,then head also produce some lift..
shifting apparent wind is much bigger because of wind gusts compare to wind shear

washout decrease lift,winglet and end plate increase lift, but all decrease induce drag/vortex drag making wing/sail more efficient...

Yes, Madge says that they measured on Sailrocket, but the basic theory of twist indicates that what happens on Sailrocket can be of little relevance because of the effect of very high boatspeed on the vectors. Secondly, as lots of theories state, the amount of shear varies according to meteorological conditions and therefore measuring at one time, place or area is inconclusive.

Secondly, with respect, why say that Madge must be right and the professionals, sailing instrument designers, professors, Boeing designers and America's Cup sailors and sailmakers with budgets of tens of millions of dollars are all wrong? Not to mention, if it doesn't exist then why do we see it? I have to often twist my boat sails much more when I am sailing inland, because I can see the tell-tales showing that there is more difference in the wind angle on top of the sail than when I am sailing on the coast.

Select to expand quote

Chris 249 said..
By the way, contrary to an earlier quote, a floppy leach is probably not like a winglet or endplate. A floppy leach seems to basically be what wing designers call "washout", which is the opposite of a winglet. Washout reduces lift at the tip, winglets increase it.

It would be interesting to find out more about how washout and floppy leaches work in sails.

Good point, but theres also a lot of difference between a floppy leech which is good in big gusts, and a progressively twisted leech.
The progressive leech acts like a ramp and the wind can accelerate off it, rubbish up wind as you need to hook the wind more, better anywhere between around 65 degrees and broad reach.

Washout is basically dumping wind....

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Chris 249 said..

Wing 11 said..

Chris 249 said..

Wing 11 said..
@chris249
Nobody said the wind shear do not exist,just that wsurf sail is to small to feel sinigficinat differnece in wind speed,this 3-4m difference in height is to small...

@Madge
"The wind speed at the front of the mast will be exactly the same at the top or the bottom of the sail."
I agree with you...

Did you ever have measurment at higher altitudes ,30m etc, how much is there differnece in speed, compare to bottom?


@al planet


In this few senteces ,evertyhing about wsurf twist is well done explain.Straight to the point.

Where you find this text ,link?

Hang on, you still haven't provided any evidence that the shear is too small to be felt over a windsurfer rig. You are relying mainly on one source (Frank Bethwaite) that doesn't say what you imply, and ignoring other sources, including professionals in aerodynamics (which Frank, with due respect, was not). Marchaj's plot, for example, is much more detailed than Frank's claim and it shows considerable wind shear between zero metres and 4.5 metres. The pic above seems to show a Star class mast. Knowing the dimensions of the Star mast and eyeballing the position of the wind indicators, it appears that there are several degrees of visible twist within a span of about three metres. That's enough to be very significant.

Professor Richard Flay of the University of Auckland, one of the aerodynamics experts involved in the team that has won the America's Cup for New Zealand, is well respected by the other America's Cup designers and engineers I know. The paper I linked to earlier explains that shear is so significant that you really need a twisted flow wind tunnel (ie one that simulates shear) to allow accurate downwind sail testing.

In that paper, Flay includes two diagrams showing shear. He also notes that "most of the twist occurs at lower levels" and that for IACC boats, twist was very important downwind but not upwind (perhaps partly due to upwash) or to the way IACC boats are trimmed.

So we still have, on the one side, people who study wind for a living, people who do racing yacht wind meters and VPP integration for a living, America's Cup winning sailmakers and meteorologists all saying that there is significant shear. On the other hand we have...........



PS - The quote Al posted, by the way, refers to the apparent wind wind shear you say doesn't exist, so if you're saying it's well done then you are agreeing that there is significant shear.

Madge has proven,he measured on sail rocket ..

AL planet post,refers to change in apparent wind because of wind gust(when true wind increase velocity=apparent wind move more aft ),not refers to wind shear...
floppy head act like flag or weather vane,point in direction into apparent wind,so head addapt to apparent wind all the time but now lift on head is zero..But if gust hit too hard(especillay on dowind course),apparent wind move to aft too much so head can not open that much,then head also produce some lift..
shifting apparent wind is much bigger because of wind gusts compare to wind shear

washout decrease lift,winglet and end plate increase lift, but all decrease induce drag/vortex drag making wing/sail more efficient...

Yes, Madge says that they measured on Sailrocket, but the basic theory of twist indicates that what happens on Sailrocket can be of little relevance because of the effect of very high boatspeed on the vectors. Secondly, as lots of theories state, the amount of shear varies according to meteorological conditions and therefore measuring at one time, place or area is inconclusive.

Secondly, with respect, why say that Madge must be right and the professionals, sailing instrument designers, professors, Boeing designers and America's Cup sailors and sailmakers with budgets of tens of millions of dollars are all wrong? Not to mention, if it doesn't exist then why do we see it? I have to often twist my boat sails much more when I am sailing inland, because I can see the tell-tales showing that there is more difference in the wind angle on top of the sail than when I am sailing on the coast.

Measured sail rocket and front wing deflection on an F1 cars. To be honest results are totally different because your actually looking for totally different effects, one is lift and acceleration and drive, the other is down force.

I agree with him that twist is not needed. There must be sails around that are contrary to what we've been doing for the last few decades, and I bet they work just fine. Wing11, do you have any examples of such a thing?

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Mark _australia said..
I agree with him that twist is not needed. There must be sails around that are contrary to what we've been doing for the last few decades, and I bet they work just fine. Wing11, do you have any examples of such a thing?

When wind has strong gusts I can not sail with out twist= less dawnhaul,sail want kill me ,catapult me,but in light winds I can sail with out twist.

Even if you dont trim sail with twist=less downhaul , sail allways have slighlty twist shape when sailing,because pressure make this shape.
Sail is not rigid,upper part allways slighty twist to leeward.

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Wing 11 said..

Mark _australia said..
I agree with him that twist is not needed. There must be sails around that are contrary to what we've been doing for the last few decades, and I bet they work just fine. Wing11, do you have any examples of such a thing?

When wind has strong gusts I can not sail with out twist= less dawnhaul,sail want kill me ,catapult me,but in light winds I can sail with out twist.

Which is what is already happening- raceboard, foil, wally or trip back to 80's/early 90's sails have less twist built in but do the same thing to a race sail designed to be travelling at higher speed & where you dont require that leverage from top of sail then as found in your own experience you go slow.

The answer is written there & between your hands when sailing yet some just like to argue over semantics. People can throw any written quote they want to support their argument but doing so often puts it out of context & anything not backed up by data is just opinion not fact. Wind shear is very real for us, it affects apparent wind & given the leverage effects from 2.5m above us twist is pretty essential for wide wind range but majority of sailors just don't use sails to full range, not many of us choose to hold down 8.6m sails in 25 knots but that is in the design brief for the sail.

& some of the comments re stuff like battens angled upwards aren't correct, when the sail is in planing position the battens are more closely aligned with flow but if that was primary concern battens would be made slimmer, batten pockets would be made different etc but battens aren't greatly above the level that trips flow on a windsurf sail. The thing that did become apparent when battens began to be angled in 1995 was that twist was less impeded, they ran more dynamic twist than prior loose leech static twist designs resulting in significantly better bottom end.

In all the maybe 100+ sails i've owned over the years only one set had too much twist, it slightly hurt bottom end & small gust response but not as much as I would have thought yet they were also the most comfortable & easy to use race sails that i've owned.

& just like Mark_australia i've been waiting for this thread to take a left turn to wing sails since 1st post

Great pic showing huge twist and he's the fastest in the buisiness.
Looks like the bottom is working like a plane wing and the top more like the wind hitting a angled sheet ( pushing forward ) and the middle half way between.???
Maybee the top is holding the bottom steady. I reckon there's heaps of different dynamics working together.
If there just now grasping how a normal plane wing actually works , ( and there is still debate ) , this twisting thing ain't going to be that simple to explain.
Saying that , the speed breaking boats use a solid narrow straight simple wing.
If the fastest windsurf sails have such a huge luff pocket and they are halfway a wing anyway , why not go all the way.
Twisty topped wing sail ???
We know we want to like them.

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Mark _australia said..
I agree with him that twist is not needed. There must be sails around that are contrary to what we've been doing for the last few decades, and I bet they work just fine. Wing11, do you have any examples of such a thing?

I seem to remember reading some years ago that they were making custom sails at the gorge in the US without twist as the wind is strong and consistant and they dont need to dump power because of gusts. I could be horribly wrong, others may know better.

On all other sailing vessels there is a tripod affect that can take up variances .
On a windsurfer it's a 100% equal , opposite balance. Mabee we need twisty , flexy , to match what our body does.
Windsurf Sails do more and more mimic bird wings , which are the absolute best at what they do. And they have millions of years of no compromise evolution on there sides.

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Imax1 said..
On all other sailing vessels there is a tripod affect that can take up variances .
On a windsurfer it's a 100% equal , opposite balance. Mabee we need twisty , flexy , to match what our body does.
Windsurf Sails do more and more mimic bird wings , which are the absolute best at what they do. And they have millions of years of no compromise evolution on there sides.

I think birds wing is good way to look at.
owl wing story :)
www.mauisails.com/video/25


Sail develop only on riders feedback to desinger.No wind tunnel,no science,no nothing high tech.
That is reason why sail evolution go so slow.

But windsurifng sport is so small,no place for high budget tehnology like in F1 or NASSA or american cup etc...
And wsurf equipment is ridiculously expensive ,so no wonder that sport is on the edge of extinction.
4000AUD one piece of styropor!!!

Lots of changes that brands made on sail/board are only from marketing/fasion reason,from year to year,and they just rotate in cycle.
Last 10 years I dont see any radical improvement.

Who can tell that for example evo10 is better sail than evo9,you think that AA sail on evo9 in 2018 will be slower than others?!!No way.
etc.

You think that severne reflex system improve sail aerodynamics??!No it does not,it was here because of marketing= better sell..
If it makes some improvement,than mach1 will still has reflex system on leech...and rest brands would copy reflex.

first year close clew,second year open clew,third year again close clew etc..Cmon bro!

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Swindy said..
I seem to remember reading some years ago that they were making custom sails at the gorge in the US without twist as the wind is strong and consistant and they dont need to dump power because of gusts. I could be horribly wrong, others may know better.

Gorge winds can be strong, yes, but consistent? Of all the places I've windsurfed, the Gorge was the only one that deserved a blog post about how gusty the wind was (boardsurfr.blogspot.com/2010/06/gusty-defined.html). But maybe I was there too early in the summer.

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TurnBackTime said..
Sail develop only on riders feedback to desinger.No wind tunnel,no science,no nothing high tech.
That is reason why sail evolution go so slow.

That may be true most of the time, but I recall reading and article about the origin of twist in windsurf sails. That included measurement of windsurf rigs mounted on cars (jeeps I think), if I recall correctly. It's been a few years since I read that, though, so I don't recall which magazine or year it was published in.

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boardsurfr said..

TurnBackTime said..
Sail develop only on riders feedback to desinger.No wind tunnel,no science,no nothing high tech.
That is reason why sail evolution go so slow.

That may be true most of the time, but I recall reading and article about the origin of twist in windsurf sails. That included measurement of windsurf rigs mounted on cars (jeeps I think), if I recall correctly. It's been a few years since I read that, though, so I don't recall which magazine or year it was published in.

Yes you are right,I aslo watched long time ago video on internet,wsurf sail on car roof and doing some test,but I cant find it any more :(

About gust,I never see wind without gusts only my hair dryer.Wish all winds blow like hair fan,I will allways sail with out twist(max horspower) :)

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boardsurfr said..

Swindy said..
I seem to remember reading some years ago that they were making custom sails at the gorge in the US without twist as the wind is strong and consistant and they dont need to dump power because of gusts. I could be horribly wrong, others may know better.

Gorge winds can be strong, yes, but consistent? Of all the places I've windsurfed, the Gorge was the only one that deserved a blog post about how gusty the wind was (boardsurfr.blogspot.com/2010/06/gusty-defined.html). But maybe I was there too early in the summer.

It can be very gusty - especially in early summer... That said, one of (if not)the first production floppy leach race sails were the Gaastra Gorge Slalom LE designed by then Rushwind(now Sailworks) designer Bruce Peterson.... not sure where you got the tight leech info, you very definitely need twist here!

Sail did not has floppy leech/head,but sail was more narrow/pointed on top , small area in top make less overturnnig moment.
Also narrow head/small area =less induce drag.

Today race sail has bigger head area,but floppy.


good old times!

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TurnBackTime said..
Sail did not has floppy leech/head,but sail was more narrow/pointed on top , small area in top make less overturnnig moment.
Also narrow head/small area =less induce drag.

Today race sail has bigger head area,but floppy.


good old times!

Yep, amazing how much better the new stuff is! ...My 3 batten wavesail has more range than that Race sail .... Awesome!

Fun to watch those old vids though .... I can still remember exactly how those sails felt. Massive skills & strength to be able to control that gear overpowered.

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Swindy said..

Mark _australia said..
I agree with him that twist is not needed. There must be sails around that are contrary to what we've been doing for the last few decades, and I bet they work just fine. Wing11, do you have any examples of such a thing?

I seem to remember reading some years ago that they were making custom sails at the gorge in the US without twist as the wind is strong and consistant and they dont need to dump power because of gusts. I could be horribly wrong, others may know better.

Would make sense, first the stronger the wind the less difference there is in wind speed at ground level comparison to higher up, 2nd the higher the wind the better a flatter sail with less twist works. You actually need more twist at lower wind speeds when your using a fuller sail profile

Hi TurnBackTime, welcome to the forum. Where in Queensland do you live and sail?

What we need is some men in white coats

and that is seabreezer Roo on the left holding the board, and Pascal Maka in the middle

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Sparky said..
and that is seabreezer Roo on the left holding the board, and Pascal Maka in the middle

Someone mention Roo! Looks like a sail on a rig on top of a truck, wonder what that does? The twist was a byproduct of trying to reduce pitching moment in the sail. On a windy day when the trailing edge of the tip was pushed up with a stick the pitching reduced as the center of pressure moved down in the sail, the numbers being spat out by the computer showed it. Gaastra were the first to take advantage of it, they also owned Rushwind at the time. Here's a double surface wingsail we were also testing at the time.

^^^^ Good to see when u fell off that thing on a salt late, you only ended up with such a small graze on ya knee

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Sparky said..
Hi TurnBackTime, welcome to the forum. Where in Queensland do you live and sail?

Thanks!

Brisbane ,usually Moreton Bay.