What brands exactly change in sail design every year so sail become "better and better"?
Aircrafts dont change wing design last 50years and we change sail desing every year, so what the hell we know that aerospace dont?

What we get with different batten stifness?

Sail materials have changed with newer ways of manufacturing and sail shape has changed, sometimes due to fashions, sometimes so they react better with certain board shapes and sometimes because we have learnt that a certain design makes more sense.
in 1990's were super light, and floppy as hell which over time has been reduced to a more steady looseness of the Leech area.
too were super light and snapped far easier then than they do now.

Wing shapes have changed for aircraft, like the ends of wings now have a little swept up bit, a little like a loose leech effect.

Batten stiffness effects how much depth a sail has and as sails have actually become flatter over the years so battens have become stiffer, less likely to break and lighter. This is due to the use of carbon which wasn't used that much 25 years ago and again due to technical advances, things like tube battens etc battens are also under a lot more tension too with the invention of Rocket style batten ends that adjust with a screw rather than a piece of webbing.

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Wind Smurf said..
Sail materials have changed with newer ways of manufacturing and sail shape has changed, sometimes due to fashions, sometimes so they react better with certain board shapes and sometimes because we have learnt that a certain design makes more sense.
in 1990's were super light, and floppy as hell which over time has been reduced to a more steady looseness of the Leech area.
too were super light and snapped far easier then than they do now.

Wing shapes have changed for aircraft, like the ends of wings now have a little swept up bit, a little like a loose leech effect.

Batten stiffness effects how much depth a sail has and as sails have actually become flatter over the years so battens have become stiffer, less likely to break and lighter. This is due to the use of carbon which wasn't used that much 25 years ago and again due to technical advances, things like tube battens etc battens are also under a lot more tension too with the invention of Rocket style batten ends that adjust with a screw rather than a piece of webbing.

Aircraft dont change wing design every year, once it is installed on plane it fly 20years...


P7 change sail panel by 25mm, what he get with this ?who said that sail is now faster ?

If you read the PWA official report it has a tolerance as sails do actually come out with slightly different measurements as things like stitch tension can alter a seam length, the seam in question was un-picked then re-stuck and the re-sewn. This has not been denied by Point 7. Point 7 also changed that sail by over 2cm on one seam.

Sails also feel different to different people as the person in question is actually holding the sail and one person may prefer a different sail shape and power due to their ability and body weight.

An Aircraft is a fixed wing vehicle and these rule don't apply. When the new Airbus 380 came into production they used lots of materials that haven't been used in Plane manufacturing before so new things are developed in the aircraft industry.

Josep may have felt like he needed slightly more or less power for that particular sail so they altered it, which is against the PWA rules.

Some brands have a two year cycle in changing items, Quatro and Goya, some ever year Severne, Duotone etc Some when they feel the need to.
I'm pretty glad they do change things because a sail thats 20 years old would be stretched to hell and wouldn't perform as well as a new sail.

Sounds like P7 have realized big sails with floppy leech's aren't efficient, hopefully others will follow.

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Ben1973 said..
Sounds like P7 have realized big sails with floppy leech's aren't efficient, hopefully others will follow.

follow?

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fpw9082 said..
Aircraft dont change wing design every year, once it is installed on plane it fly 20years...

I get your point, but there's two critical things here:

1. Airplanes have a very well defined and fairly narrow operating window and a huge team with a lot of engineering resources working on optimizing for the design objectives.

2. Removing a wing to replace it with updated technology would be a very complicated process... in fact, I'm not sure it's even possible without compromising the airframe's structural integrity. It would probably be cheaper to just build a new plane.

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ozzimark said..

fpw9082 said..
Aircraft dont change wing design every year, once it is installed on plane it fly 20years...

2. Removing a wing to replace it with updated technology would be a very complicated process... in fact, I'm not sure it's even possible without compromising the airframe's structural integrity. It would probably be cheaper to just build a new plane.

Thought I'd chime in on this just a little.

I worked on some wing modifications going to a large fuel saving winglet vs. a much smaller and simpler wingtip. The change in the winglet itself, with different mass and aerodynamics, caused a whole recertification effort. All my work was on the structural side but it was involved, in chasing down all the existing stress analysis and updating it for the new loads. Took a big team quite some time. And that's just the structural analysis side.

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Ben1973 said..
Sounds like P7 have realized big sails with floppy leech's aren't efficient, hopefully others will follow.

I can see a tighter leech being more efficient but these guys are very skilled and use the sails for 2 minutes at a time. Whereas most of the sails that are sold are used by average people like me who use them for hours on end and need them user friendly.

This is for fpw9082.

This is a bloke who takes a bit out of seams in the leech.
Funny thing is he says stuff like "just undo the batten and take 30mm out of the seam, it's easy". No its not easy, you have to then re-attach the re-enforcement, the batten end etc then put new sticky back down and re-sew batten pocket back on. Its hours of work.

Anyway here's the Vid.

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Imax1 said..

Ben1973 said..
Sounds like P7 have realized big sails with floppy leech's aren't efficient, hopefully others will follow.

I can see a tighter leech being more efficient but these guys are very skilled and use the sails for 2 minutes at a time. Whereas most of the sails that are sold are used by average people like me who use them for hours on end and need them user friendly.

Being able to use a sail 2m smaller would make life a lot easier

I like sails with their profile lower, foiling really influenced the sail design and sails became a compromise between the 2 disciplines with profiles moving higher up, ended up selling my newer sails 2022 and picked up some 2015-2017 race sails and for me they perform better on fin and feel great with power locked down low.

^^^ Lawn needs a touch of water....

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Imax1 said..

Ben1973 said..
Sounds like P7 have realized big sails with floppy leech's aren't efficient, hopefully others will follow.

I can see a tighter leech being more efficient but these guys are very skilled and use the sails for 2 minutes at a time. Whereas most of the sails that are sold are used by average people like me who use them for hours on end and need them user friendly.

20 knots average wind and 7.8m (or whatever they use) and they are doing speeds on choppy open water which is faster than I have ever done on flat water. The race sails are for use by people on the PWA scene and sailors who want to fast, at all costs. All the brands have decent 2 and/or 3 cam sails in their range in addition to their full on race sails, which you would think are easier to rig and use.

Sail evolve to adapt to different rider styles, materials and competition requirements.

Battens work to keep a sail shape together. The more battens the steadier the shape.

This may go down in history as 'the Soe/Japan debate', but it has certainly revealed a lack of understanding about sail design.

In the days when sails were simpler, people were only accused of cheating when a sail was measured as being bigger than everyone else's.
But of course in a lot of modern slalom races you can use what size sail you want, unless they limit the number of sails you can register to use.

Once you have just the one sail to use, you can tune it a bit with different outhaul and downhaul tensions, and maybe you can try and force more shape into it with extra batten tension and/or with stiffer/softer battens.


But the crucial issue for power delivery is how full the sail is cut and how the leech twists open at the head. To alter this power delivery, you then have to alter broadseaming behind the batten pockets, or else your change the 'luff round' cut into the leading panels.

The simple theory is that a tighter leach works better for light wind and for acceleration, whereas a flatter sail with an open leech may be faster at top end speed. The way the sail interacts with the mast is also pretty important.
That simplified view then gets a bit more complicated when we change from fin sailing to foil racing.
With foil racing the sailor is bodily trying to hold down the foil lift, and a tighter leech sail will help that. With fin racing, the sailor pushes sideways on a fin and is holding down the rail of the board, so his or her sailing stance is very different different in each case.

Foiling still tends to happen in lighter winds, and so this is another reason why foiling sails tend to be higher aspect and are cut with tighter leaches. And if, like in the IQ Foil class, you are course racing with an upwind leg, and then also slalom racing, the design shape of the sail will be very different from your typical PWA downwind slalom rig.

Foiling sail must have tighter leech and flater profile because efficiency factor (board speed / wind speed ratio) is higher, that mean apparent wind angle hit sail at smaller angle, sail effective angle of attack is smaller.

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Wind Smurf said..
This is for fpw9082.

This is a bloke who takes a bit out of seams in the leech.
Funny thing is he says stuff like "just undo the batten and take 30mm out of the seam, it's easy". No its not easy, you have to then re-attach the re-enforcement, the batten end etc then put new sticky back down and re-sew batten pocket back on. Its hours of work.

Anyway here's the Vid.

How they know sail is 2km/h faster if wind change speed and direction all the time?
there is no same run..
Only if two riders with same weight and height (same righting moment) and at same gear sail in the way that sail wake dont interact with other sail?

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fpw9082 said..
Foiling sail must have tighter leech and flater profile because efficiency factor (board speed / wind speed ratio) is higher, that mean apparent wind angle hit sail at smaller angle, sail effective angle of attack is smaller.

I think it's just a bit more complicated than that.

We all sail on 'apparent wind' and that wind is the combination of the 'true' wind of the day and of the 'created' wind which we feel as we drive forwards.
The true wind is often flowing across the board in typical windsurfing, whereas the created wind is running straight along the board from nose to tail.
The apparent wind then takes up an angle which is somewhere between the nose-to-tail wind and the true wind direction of the day, and we sheet in our sails to that apparent wind direction.
Another key thing to note is that the strength of the true wind tends to be less near the water and across the hull deck, but stronger up high, near the mast tip. So for most sailing craft we have sail twist which is partly to allow a different sheeting angle at the head of the sail compared to the sheeting angle at the sail foot.

With foils, a craft can sail very fast in light wind, and may even travel faster than the true wind speed of the day. That light wind efficiency in foiling means that foil craft has less twist in their sails, with the head of the sail more sheeted in to the created wind direction. There is still twist, but less so.
You can also cut a foiling sail to have a tighter leech for much the same reason. It's all about relative sheeting angles, from foot to sail head, as it is about the most efficient foil depth for both speed and acceleration.

Many windsurf sailmakers now sell sails meant for both fin sailing and for foiling, but they usually recommend you use less downhaul when setting the sail for foiling - and that's because less downhaul usually means the leech is set tighter, to adapt to a different apparent wind.
The tighter leech may also work better in 'holding the foil down' , because the drive point of the sail will be higher up.

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Basher said..

fpw9082 said..
Foiling sail must have tighter leech and flater profile because efficiency factor (board speed / wind speed ratio) is higher, that mean apparent wind angle hit sail at smaller angle, sail effective angle of attack is smaller.

I think it's just a bit more complicated than that.

We all sail on 'apparent wind' and that wind is the combination of the 'true' wind of the day and of the 'created' wind which we feel as we drive forwards.
The true wind is often flowing across the board in typical windsurfing, whereas the created wind is running straight along the board from nose to tail.
The apparent wind then takes up an angle which is somewhere between the nose-to-tail wind and the true wind direction of the day, and we sheet in our sails to that apparent wind direction.
Another key thing to note is that the strength of the true wind tends to be less near the water and across the hull deck, but stronger up high, near the mast tip. So for most sailing craft we have sail twist which is partly to allow a different sheeting angle at the head of the sail compared to the sheeting angle at the sail foot.

With foils, a craft can sail very fast in light wind, and may even travel faster than the true wind speed of the day. That light wind efficiency in foiling means that foil craft has less twist in their sails, with the head of the sail more sheeted in to the created wind direction. There is still twist, but less so.
You can also cut a foiling sail to have a tighter leech for much the same reason. It's all about relative sheeting angles, from foot to sail head, as it is about the most efficient foil depth for both speed and acceleration.

Many windsurf sailmakers now sell sails meant for both fin sailing and for foiling, but they usually recommend you use less downhaul when setting the sail for foiling - and that's because less downhaul usually means the leech is set tighter, to adapt to a different apparent wind.
The tighter leech may also work better in 'holding the foil down' , because the drive point of the sail will be higher up.

Problem is center of pressure is higher up in high AR sails, that reduce sail force that sailor weight can handle, so thrust is reduced as well.
For max thrust distance h must be minimal and L and W maximal, as formula shows..


Free body diagram

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fpw9082 said..

Basher said..

fpw9082 said..
Foiling sail must have tighter leech and flater profile because efficiency factor (board speed / wind speed ratio) is higher, that mean apparent wind angle hit sail at smaller angle, sail effective angle of attack is smaller.

I think it's just a bit more complicated than that.

We all sail on 'apparent wind' and that wind is the combination of the 'true' wind of the day and of the 'created' wind which we feel as we drive forwards.
The true wind is often flowing across the board in typical windsurfing, whereas the created wind is running straight along the board from nose to tail.
The apparent wind then takes up an angle which is somewhere between the nose-to-tail wind and the true wind direction of the day, and we sheet in our sails to that apparent wind direction.
Another key thing to note is that the strength of the true wind tends to be less near the water and across the hull deck, but stronger up high, near the mast tip. So for most sailing craft we have sail twist which is partly to allow a different sheeting angle at the head of the sail compared to the sheeting angle at the sail foot.

With foils, a craft can sail very fast in light wind, and may even travel faster than the true wind speed of the day. That light wind efficiency in foiling means that foil craft has less twist in their sails, with the head of the sail more sheeted in to the created wind direction. There is still twist, but less so.
You can also cut a foiling sail to have a tighter leech for much the same reason. It's all about relative sheeting angles, from foot to sail head, as it is about the most efficient foil depth for both speed and acceleration.

Many windsurf sailmakers now sell sails meant for both fin sailing and for foiling, but they usually recommend you use less downhaul when setting the sail for foiling - and that's because less downhaul usually means the leech is set tighter, to adapt to a different apparent wind.
The tighter leech may also work better in 'holding the foil down' , because the drive point of the sail will be higher up.

Problem is center of pressure is higher up in high AR sails, that reduce sail force that sailor weight can handle, so thrust is reduced as well.
For max thrust distance h must be minimal and L and W maximal, as formula shows..


Free body diagram

What's your point?

If you tighten the leech like he shows in the video, the center of effort moves invariably higher. This is OK if you are prepared for it.

Sailmakers can do this when they first design and build a sail.

Think of the Sailworks Hucker and Flyer sails. Both have a higher center of effort. Hucker riders are used to this. Flyer foilers actually benefit from this since it tends to push down on the sail mast base in gusts.

As a keen social windfoiler on Slalom type foils my preference is always a loose leech
Watching the PWA it looked like most foil sails tended to have a loose leech too

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tonyk said..
As a keen social windfoiler on Slalom type foils my preference is always a loose leech
Watching the PWA it looked like most foil sails tended to have a loose leech too

Thats correct about the PWA sailors having a loose leech but they are sailing at max wind strength for those sails too.
I read some of the statistics.
7.8m in 22 knots plus.
5.6m in 40 knot gusts.
They are just about holding on.
Also have noticed their stance, bent both legs and arse really out.

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tonyk said..
As a keen social windfoiler on Slalom type foils my preference is always a loose leech
Watching the PWA it looked like most foil sails tended to have a loose leech too

It looks that way.
The 2023 Duotone foiling sails I've seen have a loose leech. The locals here use them, I havent seen other brands in the flesh. Much looser than 3 years ago from what I remember. Things are developing fast. Front wings are getting a lot smaller and therefore faster as they produce less drag and dont provide as much lift as a larger wing. So maybe the idea of having to have a tighter leech to help force the board down (against the lift of the foil at speed) isnt as necessary. Sailors technique to get the smaller foils going, and gybing, is also improving (not for me though). They are using a lot longer harness lines and different body position to help keep the plot in the water as well.

I dont know about the PWA sailor's fuselage length, if that has changed. From my experience, going from a freerace type AFS 1080 wing & 85cm fuselage to a Phantom (Z Performance freeride kit) 730 wing and 100cm fuselage provides nearly the same lift, but easier to use as its more stable when I go over 20 knots. The 1000cm front wing I got in the same kit, provides lots of lift. I havent used my 8.5m sail since getting it, the 7.5m is sufficient. I'm not a slalom foiler, and the leech on my Ezzy Lions is still tighter than when I use the sail on the fin. I use less downhaul and a lot more outhaul to flatten the sail. But for slalom, it looks like loose leech, but not as loose as fin sails.

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Basher said..
.........
With foil racing the sailor is bodily trying to hold down the foil lift, and a tighter leech sail will help that. .......

Basher, how does a tighter leach help with holding foil down?

Well the theory is that a tighter upper leach makes the rig pull or drive from higher up, and then that would mean extra leverage holding the nose of the board down.
But it would be interesting to hear comments on that from anyone who takes foil racing seriously, because we are in armchair sailing territory here.