While designing faster, more efficient sails we still do the same cardinal mistake.
We are trying to improve on existing designs by small evolutionary steps.
There is an interesting attempt by our friend Mostoviy to break with this tradition and do some revolutionary changes.

I propose to start from a completely different angle and instead of improving sail, forget it completely and ask what is absolute optimal, ideal shape.

Lets forget about our restrictions: that you need to fold sail, pack and transport. Gybe and sail in opposite direction.
Lets imagine that our sail is:
-solid shape, lightweight constructions like airplane or glider wing that do not flex or alternate too much.
-at given heigh - say 400 mm our 3D wing is like a molded solid structure, where there is no mast, battens but the whole shape is built like an airplane wing.
-the whole structure is supported by carbon fiber skeleton, self-supporting, without the need for the separate mast, two surfaces tp create optimal airfoil and additionally inflated, pressurized for additional rigidity.
-our goal here is clear - to create model airfoil shape that power us: 1) only in one tack ( without flipping) 2) design for optimal speed - approx 50-60 knots relative to water/ ground.

Let's imagine how it works.
You arrived do Luderitz, attach this leaf-like sail/ wing to your windsurfing board and sail one way in Luderitz canal, on way, 50 knots or more.
Our optimal model could evolute slightly - higher /taller, wider, more triangle or trapeze like but eventually will oscillate around one optimal shape depending on our human factor.
Sailor size/dimensions, weight, and strength are typical - so there could be an only narrow range of possible 3D shape for optimal performance.
Once we create this perfect model we will know what is the absolute perfection - that we could continue our improvement in traditional sails. The closer to optimal model - the better.
Since human factor is limiting here we could create mathematical, physical model illustrating this realations in our speed windsurfing:
all forces water resistance, air drag, lift, human counterweight vector will circle an area/ space on a 3d/4D coordinate system.

www.mwsails.com/single-post/2017/12/26/CFD-Study-of-Traditional-and-Wing-Sails

I believe solid wings were built for, and tested on windsurfers back in the '80's.
See Weymouth Speed Trials.
Obviously, nobody thought it was worth pusuing further.
I got the impression from videos that they were highly unstable and hard to control.

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Roo said..
It's already been done, it's called Sailrocket 2, holds the world sailing speed record at over 65 knots for 500m and didn't need a canal to do it but open water.

Or go all the way and adapt that hook foil to wind surfing. Attached to the back of a stiffened up waist harness. Fine control by a wiggle of the hips.
Take away the need for lead-weighted Gorillas in speed sailing, or any need to rig down in normal sailing.

We also had exactly those types of sails in the early 90's. I'd say the old WildWinds speed sail would qualify as similar to what you are describing. And those sails were as you suggest ... "ideal".

They were near-impossible to control.

Not impossible.

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Ian K said..

Roo said..
It's already been done, it's called Sailrocket 2, holds the world sailing speed record at over 65 knots for 500m and didn't need a canal to do it but open water.

Or go all the way and adapt that hook foil to wind surfing. Attached to the back of a stiffened up waist harness. Fine control by a wiggle of the hips.
Take away the need for lead-weighted Gorillas in speed sailing, or any need to rig down in normal sailing.

. Even with just a cable might work well like this boat they actually made it and there is a video on youtube . As for sail design i really think we might have sails that are about as good as there going to get for how we use them.encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQmBK2_666eHh1x5uerNW9LOTXbwOloE7xM2tqP85tuWFRXVJ43

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sailquik said..
Not impossible.

Extraordinary achievement and courage! I can't imagine water starting a case of falling.But I thought rather about 50 Knotts windsurfer speed, not the wind.Taking into account that we do sail then wind, achieving this 50 Knots speed should be possible with 30 -35 wind only in our ideal conditions.
To illustrate this phenomenon we could refer to wind turbine blades. That example could serve as a model - ideal airfoil.

At wind speed mere 35 km/h the blade tip travel 290 km/ h !
This means that our ideal airfoil travel here 8 x faster than wind speed and still generate positive lift ( not a drag) .

This wind turbine blade is also generating power and slow down by electric generator motor.

Returning now to our windsurfing - we should replace this generator with water resistance and our ultimate goal should be sailing 8 x faster than wind!
www.gizmodo.com.au/2012/08/monster-machines-worlds-biggest-wind-turbine-blades-spin-at-290kmh/

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Ian K said..

Roo said..
It's already been done, it's called Sailrocket 2, holds the world sailing speed record at over 65 knots for 500m and didn't need a canal to do it but open water.

Or go all the way and adapt that hook foil to wind surfing. Attached to the back of a stiffened up waist harness. Fine control by a wiggle of the hips.
Take away the need for lead-weighted Gorillas in speed sailing, or any need to rig down in normal sailing.

If we look closely at the physical mechanism that allows sail rocket to achieve this phenomenal speed - there is one fundamental change to all previous sailboats- windsurfing including.
Instead of using body weight as a counterweight against the force created by sail. wind we should stand on the opposite side of the board and actually push the sail, not pull !! The well-fed sailor could weight around 100 kg and that is the limit. But weightlifter could push 200 - 300 kg up! Now we could use some tricks and employ lever mechanism to multiply our effort. Are there already any historical examples of windsurfers standing at opposite side of the board and pushing sail, not pulling?



I imagine that our futuristic push windsurfer would rather be semi-rigid ( at the bottom joint so sailor effort will be limited only to small force controlling wing/ sail not taking all force on himself.
Now we could go a step further and replace old fashion boyuancy board with fashionable hydrofoils blades. One pulling down and another up.
Maybe this is how sailboat and windsurfers may look in next century?

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Macroscien said..
Maybe this is how sailboat and windsurfers may look in next century?

... so... like the Olympic class cat's ?

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Macroscien said..




Instead of using body weight as a counterweight against the force created by sail. wind we should stand on the opposite side of the board and actually push the sail, not pull !!

Looking at your darwing and
at videos of the sailrocket I really think you're barking up the wrong tree. The man you drew in would clearly not be pushing against the sail if he was to replace the cables above him.

Why would one want to give up the lever the sailor hanging on to the sail provides?

What does pushing against the sail mean in terms of stability? Well, look at freestylers and you'll see that double rotations become a lot easier once you're there. I doubt this is what one would want to experience at 50+ knots.

Sailrocket does not work the way you seem to think Macro.

Simplisticly, the whole craft virtually 'hangs' off the foil with the lift of the sail. When at speed, the only parts touching the water are the foil and the steering hull at the front. And even that hull was barely touching the water apart from it's steering fin.

So think of a kite surfer with a foil sticking out the back of his harness and into the water behind him. It is L shaped and the submerged part is angled back towards the sailor and parallel to the kite (or at least at right angles to the kite lines) . Imagine when he gets going fast he is supended between the kite and the submerged foil and his board does not touch the water at all. This is the way Sailrocket works. I just can't yet imagine a way the kite sailor could control the angle of the foil, which is critical!

One of the big advances of Sailrocket (among many others) is that there is virtually no hull drag. The foil counters the lift from the wing. (there is no 'heeling' force).

I just realised that is the first picture of the supercavitating foil on Sailrocket I have seen.

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sailquik said..
Sailrocket does not work the way you seem to think Macro.

Simplisticly, the whole craft virtually 'hangs' off the foil with the lift of the sail. When at speed, the only parts touching the water are the foil and the steering hull at the front. And even that hull was barely touching the water apart from it's steering fin.

So think of a kite surfer with a foil sticking out the back of his harness and into the water behind him. It is L shaped and the submerged part is angled back towards the sailor and parallel to the kite (or at least at right angles to the kite lines) . Imagine when he gets going fast he is supended between the kite and the submerged foil and his board does not touch the water at all. This is the way Sailrocket works. I just can't yet imagine a way the kite sailor could control the angle of the foil, which is critical!

One of the big advances of Sailrocket (among many others) is that there is virtually no hull drag. The foil counters the lift from the wing. (there is no 'heeling' force).

I have thought about this before , you could control the foil easily with a computer , then the board is not really needed and the kite could be a glider , then the sailor could sit in the glider. so really im imagining a glider that drops a hydrofoil on a wire then sails as if that wouldnt go rediculously fast. ive seen a concept of doing it with a blimp before which was cool. i wonder if any one has tried this.

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sailquik said..

Simplisticly, the whole craft virtually 'hangs' off the foil with the lift of the sail. When at speed, the only parts touching the water are the foil and the steering hull at the front. And even that hull was barely touching the water apart from it's steering fin.

I am not really sure. We may have two probable situations here with sail rocket:
1) Sail is pushed into/ towards water and foil counteract in opposite direction - to float our boat above water
2) A sail is indeed working like a kite and trying to lift the whole boat. Foil then works like a plow pulling boat down.

I doubt that second scenario is realistically possible without computer exactly balancing sail and foil. The slightest imperfection, gust, and our boat will fly away ( but will not jump safely like kiters do -at this speeds above 50 knots- mean instant crash)

The first scenario is self-correcting. Additional gust will push our boat deeper int the water - but foil will correct this movement- so our boat will accelerate even more.
Oooops! I could see my mistake. Indeed you are right! Because design could work completely different once you have wind - starboard or port.
I my drawing and calculations I naturally assumed wind from opposite direction.
Which means that boat according to my plans wasn't built yet! The difference in proposed by me direction is that you could increase wind speed and speed without any limit and risk of flying away.
My vehicle works like Formula One car . That could drive upside down - due to sucking force, sticking car to the road at force well above its weight.
Same here. My boat will be pushed into the water by sail, but foil will not allow boats to sink.
My drawing showing sailor pushing on the sail is correct then.The difference between this two: Sailrocket and mine reversed design is such that mine don't have the upper limit in wind speed or boat speed. You could increase wing/ sail area and wind speed almost indefinitely - until you reach material strength limits. But that is all in my imagination and real experiments are needed to test the concept.

An additional difference is such that my design should be able to drive on a hard surface - road or ice, but sail rocket most likely will fly away at certain speed.
The difference is that Sailrocket is getting " lighter" the faster it goes. My boat is getting " heavier and heavier" . Sailorocket will fly away with increased wind and speed , my boat my only sink.

"Are there already any historical examples of windsurfers standing at opposite side of the board and pushing sail, not pulling?"

Yes sailing lee side is common. It's not fast though. You can try it yourself. Just tack like you're setting up for a helitack only don't flip the rig. Just stay on the same side. If you put much pressure on your back hand the sail will push you over. Maybe you could stand on the boom for more leverage.

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NotWal said..
"Are there already any historical examples of windsurfers standing at opposite side of the board and pushing sail, not pulling?"

Yes sailing lee side is common. It's not fast though. You can try it yourself. Just tack like you're setting up for a helitack only don't flip the rig. Just stay on the same side. If you put much pressure on your back hand the sail will push you over. Maybe you could stand on the boom for more leverage.

Closer but not exactly. Because you are still limited by the sailor weight to counteract tilting forces.
In my design you need to move mast base outside the board - to the side, say by a meter or more.
Then you stand on board and push against the sail.

Macro. Sailrocket is unidirectional, the way it is built.

And it does not 'fly away' as the wind gets stronger. The whole principle is that the forces balance and it just goes faster.

It appears only to be limited by its ability to keep the forward foil in the water to maintain steerage control. Oh, and overall structural integrity!

It also appears to be the fist sailing craft that can produce enough power to make a supercavitating foil work.

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Macroscien said..

sailquik said..

Simplisticly, the whole craft virtually 'hangs' off the foil with the lift of the sail. When at speed, the only parts touching the water are the foil and the steering hull at the front. And even that hull was barely touching the water apart from it's steering fin.

I am not really sure. We may have two probable situations here with sail rocket:
1) Sail is pushed into/ towards water and foil counteract in opposite direction - to float our boat above water
2) A sail is indeed working like a kite and trying to lift the whole boat. Foil then works like a plow pulling boat down.

I doubt that second scenario is realistically possible without computer exactly balancing sail and foil. The slightest imperfection, gust, and our boat will fly away ( but will not jump safely like kiters do -at this speeds above 50 knots- mean instant crash)

The first scenario is self-correcting. Additional gust will push our boat deeper int the water - but foil will correct this movement- so our boat will accelerate even more.
Oooops! I could see my mistake. Indeed you are right! Because design could work completely different once you have wind - starboard or port.
I my drawing and calculations I naturally assumed wind from opposite direction.
Which means that boat according to my plans wasn't built yet! The difference in proposed by me direction is that you could increase wind speed and speed without any limit and risk of flying away.
My vehicle works like Formula One car . That could drive upside down - due to sucking force, sticking car to the road at force well above its weight.
Same here. My boat will be pushed into the water by sail, but foil will not allow boats to sink.
My drawing showing sailor pushing on the sail is correct then.The difference between this two: Sailrocket and mine reversed design is such that mine don't have the upper limit in wind speed or boat speed. You could increase wing/ sail area and wind speed almost indefinitely - until you reach material strength limits. But that is all in my imagination and real experiments are needed to test the concept.

An additional difference is such that my design should be able to drive on a hard surface - road or ice, but sail rocket most likely will fly away at certain speed.
The difference is that Sailrocket is getting " lighter" the faster it goes. My boat is getting " heavier and heavier" . Sailorocket will fly away with increased wind and speed , my boat my only sink.

definitely option 2
This boat is so cool every part of its perfect even the hull is angled for the apparent wing and not the direction of travel its sad that other craft like kites and windsurfers go for it in such a brute force way just counting on more wind rather than just perfect design like this

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sailquik said..
Macro. Sailrocket is unidirectional, the way it is built.

And it does not 'fly away' as the wind gets stronger. The whole principle is that the forces balance and it just goes faster.

It appears only to be limited by its ability to keep the forward foil in the water to maintain steerage control. Oh, and overall structural integrity!

It also appears to be the fist sailing craft that can produce enough power to make a supercavitating foil work.

1. Re "Sailrocket is unidirectional, the way it is built."
It is at this moment, indeed unidirectional, but I am trying to prove that don't have to be. More. I am trying to show that could be even faster when we apply wind from another side! Obviously, that requires only small modification and beside cables to pull sail we need also rod/ stick to push them up while sailing in opposite direction. Reverse foil angle to action from pulling down to pushing up.


2. Cavitation is usually our enemy. But I think that one day we could use cavitation to our advantage.
Let's imagine a pair of foils. One will cause cavitation and another follow in this disturbed water.
If we could now achieve more lift ( due to lower drag) on second foil then we lose of the first one then the balance of the expenditure on cavitation could be eventually positive.
It could be the quite interesting experiment to insert cavitation foil in the front of the main foil as see what happen then. Let's remember that our hydrofoil in sailboats may work in both direction - up or down ( lifting the boat from water or pulling down) and our cavitation may help/ benefit in one of those.
Super torpedo may travel nowadays much faster underwater in cavitation bubble.

The flipping image is of the first sail rocket. This one had several design faults. Initially they struggled to get it over 30 knots , in fact they had difficulty getting it planning. Then when they sorted that and got some speed up the second serious flaw became apparent. The lifting foil/wing was attached to the forward planning pod. But they learned from their mistakes and built another correcting those faults. Simon 100, when SailRocket was just a 60cm model, there was guy who started to build a glider with a hydrofoil. I've seen photos of it almost finished but never heard anymore about it. I think he ran out of funds or time.
Andrew, the kiter towing a foil idea has been around a while now. 42 years in fact..
miriam-english.org/files/ultimate-sailing-rig-without-hull/The%20Ultimate%20in%20Sailing%20is%20a%20Rig%20Without%20a%20Hull.html
Somehow it doesn't seem practicable. A better option would be to try to improve on sailrocket....

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Macroscien said..

2. Cavitation is usually our enemy. But I think that one day we could use cavitation to our advantage.
Let's imagine a pair of foils. One will cause cavitation and another follow in this disturbed water.
If we could now achieve more lift ( due to lower drag) on second foil then we lose of the first one then the balance of the expenditure on cavitation could be eventually positive.
It could be the quite interesting experiment to insert cavitation foil in the front of the main foil as see what happen then. Let's remember that our hydrofoil in sailboats may work in both direction - up or down ( lifting the boat from water or pulling down) and our cavitation may help/ benefit in one of those.
Super torpedo may travel nowadays much faster underwater in cavitation bubble.

super-torpedo's have stability issues... unless they also stick plain old foils outside of the cavitation bubble ( into the rather still water ). But more importantly -> they use thrust-vectoring (gimbled engines, tail-fins, etc).

Cavitation is water-vapour-bubbles that collapse under surrounding-water pressure. We could use it to our advantage as a method to reduce drag - it does not allow us to put a control-surface inside the bubble(s)... Ask anyone who has ever surfed/windsurfed/sup/etc, there is no control in white-water [ when it is full of air ]. I dont see how control is achieved with a second foil in this turbulent flow.

I like the idea of thinking outside the box - but some materials work better under tension, than under compression ... like carbon. But saying "going even faster" than the current-record-holder (... and smashed the record by like 20%), sounds a bit silly ... if you came up with some vector-diagrams of pressure/thrust/etc, it might be easier for us to visualise how we could go x8 faster than 30kn.

Let's look at the most aerodynamically efficient machine today.
Modern Glider.



As we can see total wing area is only 10m2 !
Quite comparable to our windsurfing sail size.
Whole device is still controlled manually by a single person wit effort needed much less then windsurfer.
But have a look what this 10 m2 can do:
carry up 600 kg with speed up to 270 km/h

If our windsurfing or just sailboat development goes this direction that is reasonable limit what we could expect at Lauderitz A.D. 2117

Grandson of our Sailquick doing above 200 km/ h on massively extended Lauderits runway.
I am afraid that he may need to use parachutes then to stop, as lay down gybe is not an option to stop the vehicle.

If we are trying to guess how XXII nd century windsurfer may look like here is my vision.
We tend to think that higher the speed the smaller and narrow windsurfing board must be.
Up to needles like speed boards at speed channels 40 cm wide and 50 liters (?)
That may not be the case for our windsurfer traveling 150 -200 km/ h - or 100 knots if you like.
Water resistance is merciless at higher speeds.
If we can we should avoid contact with the water to an absolute minimum.
So our future windsurfer will fly over water surface completely, not just sometimes from time to time.
Future sailboards employ following effects:
-flying on the cushion of air above the water ( like wonder Goose build by Hughes)
- use ailerons spoilers to push boar into the water like F1 racing cars
- all powered by inflated pneumatic wing like a sail. Yes. I am afraid that future generations of windsurfers need to pump their gear as kiters do nowadays.
So summarizing. Our high-speed windsurfing boar may look rather like nowadays RSX board or even twice as wide and long.
To provide:
1) adequate lift over water,
2) stability when pushed down by spoilers
3) counter lever to asymmetrically located sail/ wing ( yes - mast base will not be located in the middle of the board but to the side - but can change sides after gybe)
4) our windsurfer aslo change sides in relation to sail/ wing. This time will by on the other side of the sail
5) Sail vertical axis tilted not towards wind but with wind wind
6) Yes, we still need some sort of connection with water, for basic physics of our wind propulsion to work. But maybe instead of fin we use wheels rather. Not a traditional tires but spinning circular blade attached to our board and cutting through the water surface. This blade wheels provide us required lateral resistance but also lift of downward forces - as hydrofoils od nowadays. The advantage of our wheel instead of the fin or hydrofoil is such that at high speed remains almost stationary in relation to water- so drag us massively reduced.If we use few circular blades separated by few mm we have another physical phenomenon to our disposal - Tesla turbine that could provide us another angle of unlimited forces. So Tesla may be present not only on the roads but on the water too in XXII century.

Now I could imagine that handling 10m2 while sailing at 100 knots must be quite exciting!

We may need new sort of airbags- instantly inflated around sailor in the case of a crash.

This is what I will think a 22nd century windsurfer will look like:



















Extinct

But to humour you Macro. Look at the most efficient wind powered Land and Ice speed record holders.

Not that fast, even with very high aspect wings and very streamlined bodywork. The land records is 126 MPH (109.5 Kts)



The Ice record is actually lower. although no one seems to know why. (Edit: Although there are unofficial and unverified reports of some large ice yachts reaching up to 137Kts)

That means that Sailrocket2 is only about 60% as fast as the Land Yacht, and SR2 blew every other boat completely out of the water! To get anywhere even near the land craft speeds will require some very different thinking and design, just like SR2 was a radical departure from other water sailing craft.



Land sailing record holder:


Ice sailing record contender.

Here is something else to think about:

Developed in the '80's and breaking world sailing speed records in the '90's. Longshot - Tri-Foiler

Put into mass production in a slightly larger, tow seat model by Hobie in the 90's with a couple of hundred Hobie Tri-Foilers produced.

Capable of 30+ Knots in production form (I rode with Mal Wright in one to a peak of 32 knots in less than 13 knots of wind - two up!)

Longshot held records over 43 knots.

Mal Wright obtained one from the USA in about 2007 and declared with confidence that even the production version could easily do over 40 knots with better foils (Even to my untrained eye, the foils look very agricultural). Sails could be improved a lot too, even using just a modern windsurfing design. Unfortunately, Mal's project never got off the ground due to other priorities. (It has sat in my backyard now for over 6 years).

AFAIK, this is by far the fastest off the beach, commercially mass produced sailing craft ever. I wonder whether even the newly developed "Super Foiler' would be faster reaching off the wind, and that is not something you could sail recreationally without a lot of skill.

The word out there is that of lot of Yachties bought these and promptly scared the sheet out of themselves, put them in the shed and there they have stayed.

Goes on both tacks. Foiling Gybes and Tacks. Foils upwind in 15 knots with 2x10sq/m sails.. Walks over moderatly choppy water like it's not there.

What is not to like?

I think I should get her cleaned up and take another tilt at it.

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Macroscien said..
Whole device is still controlled manually by a single person wit effort needed much less then windsurfer.
But have a look what this 10 m2 can do:
carry up 600 kg with speed up to 270 km/h

It can go that fast, because the glider is put into a dive - it is speed-limited due to drag -> the lift plays very little part in going that fast. In fact, the excessive lift (needed for efficient soaring), is a big contributor to the drag (it is known as "plan-form drag").

There is a reason we use lead-weight-jackets - it allows us to use a bigger sail for a given set of wind conditions, allowing go faster for our size. The extra weight gives us more control over that foil - just like adding water to a glider, it stabilises the wing (ie: "wing loading"). But there is a limit to how the size that person can carry -> I can wear 5kg all day and not notice it, but 10kg makes me tired in an hour (I am 70kg)... gliders carry most of that weight in their structure/wings, not on the person.

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Macroscien said..
6) Yes, we still need some sort of connection with water, for basic physics of our wind propulsion to work. But maybe instead of fin we use wheels rather. Not a traditional tires but spinning circular blade attached to our board and cutting through the water surface. This blade wheels provide us required lateral resistance but also lift of downward forces - as hydrofoils od nowadays. The advantage of our wheel instead of the fin or hydrofoil is such that at high speed remains almost stationary in relation to water- so drag us massively reduced.If we use few circular blades separated by few mm we have another physical phenomenon to our disposal - Tesla turbine that could provide us another angle of unlimited forces. So Tesla may be present not only on the roads but on the water too in XXII century.

For something to affect your directional stability, you need to apply a force. Your wheel would need to push sideways (to your direction of travel) so that the wind doesn't just push you sideways. It is the same size of sideways force ( this is just an application of Newton's third law ) - how can you provide lateral resistance without also creating drag ? [ ie: making a statement, needs to be supported by verifiable facts ]

The Telsa turbine hasn't ever been shown to drive a load. It is a nice idea/experiment, but there is no evidence to suggest that we could extract any meaningful work out of it. Do you have a diagram of how you think this might work ?

All this quest for advancement and innovation, when i was young we used to use handkerchiefs tied to icypole sticks on a rubbish bin lid and we were happy when our father used to beat us up for having fun at the beach.........

As a kid who hasn't jumped off a wall, fence or verandah with a big umbrella and imagined themselves flying!!

Came here to joke that propellers are the future, but now I want a tri-foiler.

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Macroscien said..
Let's look at the most aerodynamically efficient machine today.
Modern Glider.



As we can see total wing area is only 10m2 !
Quite comparable to our windsurfing sail size.
Whole device is still controlled manually by a single person wit effort needed much less then windsurfer.
But have a look what this 10 m2 can do:
carry up 600 kg with speed up to 270 km/h

If our windsurfing or just sailboat development goes this direction that is reasonable limit what we could expect at Lauderitz A.D. 2117

Grandson of our Sailquick doing above 200 km/ h on massively extended Lauderits runway.
I am afraid that he may need to use parachutes then to stop, as lay down gybe is not an option to stop the vehicle.

You've forgotten that you have used an external power source to achieve the results of wind power. Start the glider at ground level and use just the wind to propel it forwards. Using the airplane is cheating