I'm considering to buy a larger sail for my Bic WindSup 11'6", which in some respects is similar to a longboard and I have seen a brand ( I don't recall which one) with 3/4 length battens , i.e. not extending to the luff, like the conventional shortboards( planing) sails.

The reason for this would be, according to some, that 3/4 length battens ( at least the main battens above the boom) allow a better light winds performance because of a tighter leech, unlike the regular planing sails which need a strong d/haul and a floppy top to perform in higher winds planing.
In fact the older longboards performed very well in light winds subplaning with partially battened or soft sails.

I used to think that perhaps there is some merit in this argument. In fact, as reported elsewhere in this or other Forums, I have done myself experiments with some of my sails by pulling away ( or squarely cutting!) the battens about 5" or 6" away from the luff and I have found that the sail does gain more power .

This has sparked a debate, with some saying that this " more power" is a false perception: a tight leech shifts the draft from the lower sail ( larger) to the upper sail ( narrower) , where it is less efficient, hence in the end I lose power. In trhe end, better using a larger sail in light winds than toying with a tight leech.

This argument had in the end convinced me, especially after reading about the principles of the foil, according to which the lift is caused by the pressure differential between the two faces of the sail( foil) , one being curved, hence with less air pressure because the air molecules are dispersed along a longer surface. ..

But then the 3/4 length battens seem to undermine this principle : there would be a soft spot around the luff and this lessens or breaks the full curvature of the sail at the point of attack ( the mast) where the wind-flow splits creating curved streamlines along one face of the foil.
With 3/4 length battens at the more strategic part of the sail (the lower one) isn't the full power of the sail decreased?

Are these 3/4 battens sails recommended?

Thanks

Ittiandro

Personal preference.
Small, tight leech sails can be very fast, in their wind range, which is usually smaller than a bigger, loose leeched sail. But the gain is sail handling from the smaller size.
The gain in power is not all that great with 3/4 length battens, but it's mostly noticeable in non planing winds. Once powered up for the size and tuning, there isn't much difference in feel.
I do use a couple of SuperFreaks mixed in with North Zeta/Voodoos of the same sizing.

Maybe put a link to the sail you are talking about.

Clarence

Hot Sails Maui Superfreak and SpeedFreak.

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clarence said..
Maybe put a link to the sail you are talking about.

Clarence

It is a HSM Superfreak at www.hotsailsmaui.com/sail.php?uid=1

At some point of low winds and sub-planning conditions I imagine the sail acts more like a parachute than a wing.

At that point you get no power from the foil shape, but simply from the area exposed to the wind.



I am pretty sure the idea of the Superfreaks is more than just two of the five battens being 3/4 length. Would being made of soft Dacron not mean the battens have less effect in shaping the cloth into a foil across the whole sail so the material becomes a factor as much as batten length.

But I am not convinced that the difference between two sail brands of exactly the same size when sailing a SUP in 8 knots will be the difference between a rubbish time and good time. The point of sailing a SUP in 8 knots surely isn't to go as fast as possible. Chasing every last knot in those conditions is not the point of those conditions.

The Superfreaks are arguably the most 'durable' sails out there. When you are not sailing your kids can make cubby houses with them in the back garden. You can use them as a mattress when camping, you won't crease the sail. A dog on the beach can run across them, it won't scratch the monofilm.

I sail Superfreaks (sometimes). A superfreak (especially a Superfreak UL) on a SUP would be great (but so would many other brands and models). But a Superfreak isn't going to make you hit 20 knots when a same size sail of another model drives you at 10 knots. But likewise it won't limit you to 10 knots when you otherwise be doing 20.

I reckon that if you are on a SUP with a sail bigger than about 6m2 then that isn't the point of a windSUP. If that is the sailing you want to do get a long board / race board, not a bigger / different sail.

The HOT SAILS MAUI Superfreak, has 5 battens, The 2 above the boom are 90, NINETY % , they do not reach the mast. Not 75% not 3/4

the remaining 3 are 100% in length, meaning full length.

the Superfreak UL, ultra light, ME, Maui Edition, Speedfreak are all variations of the Classic Superfreak.

the dacron material probably has more/higher defining character than the batten lack of length.

This is a makers blurb for the sail:

The 2 battens directly above the boom are both 90% in length, stopping just short of the mast sleeve. This batten design provides a super controllable, luffable sail that can be powered or de-powered in an instant.

The design is all about control at the expense of power response and speed.

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Francone said..
I'm considering to buy a larger sail for my Bic WindSup 11'6", which in some respects is similar to a longboard and I have seen a brand ( I don't recall which one) with 3/4 length battens , i.e. not extending to the luff, like the conventional shortboards( planing) sails.

The reason for this would be, according to some, that 3/4 length battens ( at least the main battens above the boom) allow a better light winds performance because of a tighter leech, unlike the regular planing sails which need a strong d/haul and a floppy top to perform in higher winds planing.
In fact the older longboards performed very well in light winds subplaning with partially battened or soft sails.

I used to think that perhaps there is some merit in this argument. In fact, as reported elsewhere in this or other Forums, I have done myself experiments with some of my sails by pulling away ( or squarely cutting!) the battens about 5" or 6" away from the luff and I have found that the sail does gain more power .

This has sparked a debate, with some saying that this " more power" is a false perception: a tight leech shifts the draft from the lower sail ( larger) to the upper sail ( narrower) , where it is less efficient, hence in the end I lose power. In trhe end, better using a larger sail in light winds than toying with a tight leech.

This argument had in the end convinced me, especially after reading about the principles of the foil, according to which the lift is caused by the pressure differential between the two faces of the sail( foil) , one being curved, hence with less air pressure because the air molecules are dispersed along a longer surface. ..

But then the 3/4 length battens seem to undermine this principle : there would be a soft spot around the luff and this lessens or breaks the full curvature of the sail at the point of attack ( the mast) where the wind-flow splits creating curved streamlines along one face of the foil.
With 3/4 length battens at the more strategic part of the sail (the lower one) isn't the full power of the sail decreased?

Are these 3/4 battens sails recommended?

Thanks

Ittiandro

Here is your question , Do you recommend the Superfreak based on , 2 batten lengths ,THAT, don't extend to the the mast?

the battens are One, of the charactericts that define how the sail performs, intended to sail. Placement, number of, material of..on on on
tbe panel layout is another design feature that determines, and the sail material and WHERE it's placed.

the HSM Superfreak , has a cult like following, like vegemite or marmite.
It is soft and forgiving, it excels in being overpowered, the dacron has much more give than other sail ..mono..like material, it is extremely durable, will fade if left in the sun a lot. They are the opposite from a power wave sail, the power delivery is slow and deliberate, rather than abrupt.

it spawned other iterations since around 2008, but remains in its basic premise . It is fairly lightweight, best mast would be a slightly soft top, SDM ok so long as it's softish.
for use on a WINDSUP it would be hard to find OVERALL a better weapon .

SF 3.7 5.0 5.5 5.8 6.0
SF UL 4.2 4.7 6.2
SF ME 3.7
SF Micro 3.2

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forceten said..


Here is your question , Do you recommend the Superfreak based on , 2 batten lengths ,THAT, don't extend to the the mast?

the battens are One, of the charactericts that define how the sail performs, intended to sail. Placement, number of, material of..on on on
tbe panel layout is another design feature that determines, and the sail material and WHERE it's placed.

the HSM Superfreak , has a cult like following, like vegemite or marmite.
It is soft and forgiving, it excels in being overpowered, the dacron has much more give than other sail ..mono..like material, it is extremely durable, will fade if left in the sun a lot. They are the opposite from a power wave sail, the power delivery is slow and deliberate, rather than abrupt.

it spawned other iterations since around 2008, but remains in its basic premise . It is fairly lightweight, best mast would be a slightly soft top, SDM ok so long as it's softish.
for use on a WINDSUP it would be hard to find OVERALL a better weapon .

SF 3.7 5.0 5.5 5.8 6.0
SF UL 4.2 4.7 6.2
SF ME 3.7
SF Micro 3.2

Yes, basically what I wanted to know was if a sail like the Superfreak with two battens that are not full length is just as efficient than sails with full length battens. My question was framed from a theoretical perspective involving the question of the foil, but you and others have indirectly addressed this issue by pointing out that the battens are not the only characteristic that determine the performance of a sail. In the case of the Superfreak, the Dacron seems to weigh considerably in the excellent performance of the sail. Good to know!

It is very expensive though. Maybe other less expensive brands will do, even 2nd hand and I'm open to suggestions. I understand that a WindSup is not made for planing and speed, but I don't think that with a 6.2 I have reached the limits of its design and that I cannot tackle stronger winds and perhaps planing, especially now that I started using the harness.

Thanks to you and others for your input

Francone

When rigged and lying on the ground a SF is completely flat, no shape or belly, only when put in the wind does it take shape. This is useful for depowering completely while waiting for a wave or swell. SF rigs with neutral or very little outhaul.
Compare this for instance to an Ezzy which uses a lot of outhaul and sets with a lot of shape, a big belly.
A used SF would be a good value as they last so long.

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Carantoc said..
At some point of low winds and sub-planning conditions I imagine the sail acts more like a parachute than a wing.

At that point you get no power from the foil shape, but simply from the area exposed to the wind.



I am pretty sure the idea of the Superfreaks is more than just two of the five battens being 3/4 length. Would being made of soft Dacron not mean the battens have less effect in shaping the cloth into a foil across the whole sail so the material becomes a factor as much as batten length.

But I am not convinced that the difference between two sail brands of exactly the same size when sailing a SUP in 8 knots will be the difference between a rubbish time and good time. The point of sailing a SUP in 8 knots surely isn't to go as fast as possible. Chasing every last knot in those conditions is not the point of those conditions.

The Superfreaks are arguably the most 'durable' sails out there. When you are not sailing your kids can make cubby houses with them in the back garden. You can use them as a mattress when camping, you won't crease the sail. A dog on the beach can run across them, it won't scratch the monofilm.

I sail Superfreaks (sometimes). A superfreak (especially a Superfreak UL) on a SUP would be great (but so would many other brands and models). But a Superfreak isn't going to make you hit 20 knots when a same size sail of another model drives you at 10 knots. But likewise it won't limit you to 10 knots when you otherwise be doing 20.

I reckon that if you are on a SUP with a sail bigger than about 6m2 then that isn't the point of a windSUP. If that is the sailing you want to do get a long board / race board, not a bigger / different sail.

Carantoc said..
At some point of low winds and sub-planning conditions I imagine the sail acts more like a parachute than a wing.

At that point you get no power from the foil shape, but simply from the area exposed to the wind.



I am pretty sure the idea of the Superfreaks is more than just two of the five battens being 3/4 length. Would being made of soft Dacron not mean the battens have less effect in shaping the cloth into a foil across the whole sail so the material becomes a factor as much as batten length.

But I am not convinced that the difference between two sail brands of exactly the same size when sailing a SUP in 8 knots will be the difference between a rubbish time and good time. The point of sailing a SUP in 8 knots surely isn't to go as fast as possible. Chasing every last knot in those conditions is not the point of those conditions.

The Superfreaks are arguably the most 'durable' sails out there. When you are not sailing your kids can make cubby houses with them in the back garden. You can use them as a mattress when camping, you won't crease the sail. A dog on the beach can run across them, it won't scratch the monofilm.

I sail Superfreaks (sometimes). A superfreak (especially a Superfreak UL) on a SUP would be great (but so would many other brands and models). But a Superfreak isn't going to make you hit 20 knots when a same size sail of another model drives you at 10 knots. But likewise it won't limit you to 10 knots when you otherwise be doing 20.

I reckon that if you are on a SUP with a sail bigger than about 6m2 then that isn't the point of a windSUP. If that is the sailing you want to do get a long board / race board, not a bigger / different sail.

In light winds and sub-planing a sail works the same as it does in strong winds. There's no difference at all in the basic way a sail works that is related to windstrength per se. However, in light winds the foil shape is very important because a deeper foil gives more power.

A sail designed for a SUP or longboard will be significantly faster than a shortboard sail in light winds on a SUP. It's hard to estimate how much difference it would make, but put it this way - if you put a soft longboard sail on a shortboard you go a lot slower than you do with a shortboard sail. The same applies when you put a shortboard-type sail on a longboard in anything under about 20+ knots of wind.

Some people find extra light-wind speed as important as extra strong wind speed. If it's blowing and you're charging around at 30 knots, going 2 knots faster may not be all that important. Because of the way drag and apparent wind work, a small initial increase in speed in light winds can allow you to generate a noticeable amount of extra speed, which can make the difference between gliding and schlogging.

Select to expand quote

Francone said..
I'm considering to buy a larger sail for my Bic WindSup 11'6", which in some respects is similar to a longboard and I have seen a brand ( I don't recall which one) with 3/4 length battens , i.e. not extending to the luff, like the conventional shortboards( planing) sails.

The reason for this would be, according to some, that 3/4 length battens ( at least the main battens above the boom) allow a better light winds performance because of a tighter leech, unlike the regular planing sails which need a strong d/haul and a floppy top to perform in higher winds planing.
In fact the older longboards performed very well in light winds subplaning with partially battened or soft sails.

I used to think that perhaps there is some merit in this argument. In fact, as reported elsewhere in this or other Forums, I have done myself experiments with some of my sails by pulling away ( or squarely cutting!) the battens about 5" or 6" away from the luff and I have found that the sail does gain more power .

This has sparked a debate, with some saying that this " more power" is a false perception: a tight leech shifts the draft from the lower sail ( larger) to the upper sail ( narrower) , where it is less efficient, hence in the end I lose power. In trhe end, better using a larger sail in light winds than toying with a tight leech.

This argument had in the end convinced me, especially after reading about the principles of the foil, according to which the lift is caused by the pressure differential between the two faces of the sail( foil) , one being curved, hence with less air pressure because the air molecules are dispersed along a longer surface. ..

But then the 3/4 length battens seem to undermine this principle : there would be a soft spot around the luff and this lessens or breaks the full curvature of the sail at the point of attack ( the mast) where the wind-flow splits creating curved streamlines along one face of the foil.
With 3/4 length battens at the more strategic part of the sail (the lower one) isn't the full power of the sail decreased?

Are these 3/4 battens sails recommended?

Thanks

Ittiandro

Whether the upper leach is tight or not should have no effect, in itself, on the draft lower down. Same with battens - they don't have to have any effect on the draft of a sail, how tight the leach is, or the curvature of the luff. Look at a Laser dinghy sail - it has very short battens but it has a very tight leach and a fairly even curve at the luff.

Battens are a tool that can be used to change or maintain sail shape - they don't have to change shape by themselves. Way back when, they were used to force extra depth into dinghy sails (because if you pull them tight, the compression forces the sail into a curve) and then a while later they were used to make dinghy and catamaran sails flatter (because they used stiff battens with less tension and the battens acted as stiffening to stop the sailcloth from stretching).

Secondly, the upper part of a sail is not less effective, especially in light winds. In light winds the air down at the lower part of the rig is often significantly slowed by friction over the water and any land upwind, therefore the upper part (which can be in noticeably stronger wind) can be the most effective part of a sail.

One big advantage of shorter battens is that battens and pockets are really heavy. That doesn't matter much if you are reaching around in 20 knots in a straight line, balancing rig weight against wind force, but it can make a big difference in light winds when you have to move the rig over a wider range and often have to essentially hold it up. The original Windsurfer dacron sail is less than 2kg with battens - a modern sail of the same size is often well over 4kg with battens, which you can really feel when you are moving something with a centre of gravity above your head. If you are using a sail in light winds, when the wind is not strong enough to distort the sail so you don't need battens to keep the shape rigid, you may not want to carry the extra weight.

I'm no expert about aerodynamics, but there may be an issue with the idea that foils lift because of the difference in the length of the two faces - in a sail a millimetre or so thick, how can there be enough difference to create the force we experience? I've been lucky enough to be able to bother some very good aerodynamic experts (ie MIT professors, Boeing designers, designers of America's Cup rigs and world record-breaking foils, America's Cup sailmakers and design chiefs, etc) about sails. As all the experts say, there are a bunch of different ways to model and understand lift. Personally I find the momentum model to be intuitive and useful. If we think that we essentially get moving by re-directing the air flow so we shove it out the back, quite a few things become easy to understand, like why we want to change the balance between lift and drag, why we want to reduce turbulence, the advantages of elliptical span loading, why induced drag decreases by the square, etc.

I find this link

www.aviation-history.com/theory/lift.htm

to have a very good explanation. To me, the line "We now would like to introduce a new mental image of a wing. One is used to thinking of a wing as a thin blade that slices through the air and develops lift somewhat by magic. The new image that we would like you to adopt is that of the wing as a scoop diverting a certain amount of air from the horizontal to roughly the angle of attack" is something that is easy to apply when we're adjusting sail shapes.

yeah but ...

In very light winds wouldn't you hold the sail so the angle of attack is at 90 degrees (or close to 90 degrees) and so the windward surface area becomes more important than any draft within the foil ?

I guess the definition of "light" is arguable. I am picturing this :



Not this (with one person struggling watching another planning and thinking they could do the same if only they had .... ) :

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Carantoc said..
yeah but ...

In very light winds wouldn't you hold the sail so the angle of attack is at 90 degrees (or close to 90 degrees) and so the windward surface area becomes more important than any draft within the foil ?

I guess the definition of "light" is arguable. I am picturing this :



Not this (with one person struggling watching another planning and thinking they could do the same if only they had .... ) :

Nope, you don't; even in really light stuff like in the top pic, you try desperately to keep attached flow (ie air flowing evenly from front to back of the sail) rather than pulling the sail on and stalling the flow (ie getting it to act like a parachute). This is best seen on boats, where you have "tufts" on the sails that show the flow (or lack of it). Light-wind speed depends enormously on sail trim that keeps the airflow attached as it flows from front to back.

Part of the reason why boards are slow in very light winds is that the rigs are not designed to keep flow attached as much as possible, as boat sails are (or can be, because they have more adjustments available).

Even on a "parachute spinnaker" on a boat, you are trying to keep air flowing from luff to leach as much as possible - that's why you continually ease the sheet to make sure that the luff is curling and the sail is eased off as far as possible. Parachutes also work via the principle of flow.

Well, you learn something new everyday.


So what about when you pump the sail then ?

In a fully cambered sail that holds its foil shape I can understand this would just accelerate the speed that the foil is moving through the airflow, so generating more lift. But in the top pic above, pumping would generate more forward movement but wouldn't it be more like pulling a bucket through water than creating a laminar flow across a wing ?

Francone,

I would suggest a 3 x batten NP Fly or the 4 batten NP Wizard before people start to red thumb me as these are specialised sails both these sails are designed to depower & re-power quickly which works great for a wind SUP, plus they are very light. Go see Reg at windsurfing Perth I know he has some superseeded models available.