Electronic Foil Control Systems.

[clivee1]

It would be best to use the accelerometer for high-frequency height control and use the wand for low-frequency height control. The accelerometer will be subject to bias, scale factor, and alignment errors that will result in unbounded (ie, very, very large) errors if the acceleration is integrated to get vertical velocity and height. However feeding back wand position to the height estimate will stabilize the estimate against these errors. At the same time, the accelerometer will respond faster to a change in height than will the wand, making it most suitable for adding lead to the height control.

This is what I do. I do not amplify the accelerometer input to provide a phase advance, but do use the vertical velocity in the height control loop to achieve the same thing through a controlled gain setting.

Attached pic show data log from moment of instability, and a full 18kt crash. At the moment I have the height coupled to the wand quite tightly (0.5 sec) but this still filters a significant amount of chop that would feed through to the servo.

Scalling:

Height (mm)

Vvel (mm/S)

Vacc (mm/S/S)

The height trace follows the wand with no phase lag, but with reduced chop.

As my confidence grows I am sure that I will be able to further decouple and fly in inertial space.

 

[clivee1]

What you really need is a dynamic model that allows you to express the relationship between the motion of the boat and the values measured by each of the sensors, and the effectiveness of your control surface. Then you can estimate the quantities you want to control and determine how to move the surface. Check out NACA TR-918.

I have a model using an electrical analogue and a spice simulation package however at this scale

verifying and developing the model can make the project bigger not smaller.

 

[clivee1]

If you were trying to achieve precise positioning in the horizontal plane, you'd want direct side force control then, too.
There are really two coupled modes to the boat's motion you're trying to control - a pitch mode and a heave mode. With one control, you can only get at one mode by the way in which it is coupled to the other mode. With two controls, you can control each mode directly. And with the additional control you can satisfy an additional objective, such as minimizing drag.

The control of height using tail control will always have a lag compared to controlling height with the main foil flap. The reason is to change height, you need to change the vertical velocity, and to change the vertical velocity you need to change the vertical acceleration by changing the lift on the foil. If you have a flap on the foil, when you change the flap deflection, you change the lift and create an immediate change to the vertical acceleration. If you change the lift through the changing the pitch attitude of the boat to control the angle of attack of the foil, then you first have to generate a pitch acceleration to generate a pitch rate to generate a change in pitch attitude. Only once the pitch attitude changes do you change the lift on the foil and change the vertical acceleration and start to affect the height.

But it's worse than that. With tail control, as opposed to a canard, the tail has to drop to increase the angle of attack. So the boat actually has to descend slightly before it can start to rise. This has significant implications for the stability of control loops.

It's simply not possible to get as tight a height control using only the rudder foil compared to controlling only the main foil flap. The lags in the height response to pitch control mean that the boat will go unstable if the height control is cranked up too high.

However, height control using the flap is also subject to serious limitations. The flap only has limited authority. The lift on the foil is a function not only of angle of attack but of speed. Since the lift has to equal the weight, as the speed increases, the flap has to be deflected to offset the increase in lift due to speed. Eventually the flap will be fully saturated just trying to maintain the trim of the boat, and even before then, any deflection for trim takes away from the authority available to counter dynamic disturbances. Tail control doesn't have quite as much limitation in this regard. There's not much difference in angle of attack required to climb or descend at a constant angle, so once the pitch attitude is set, the tail control can return to near its trim value as the height changes. So over the long term, the tail can be much more powerful than the flap.

The combination of characteristics means the flap and tail controls can be used in complementary ways. The flap can null out high-frequency disturbances from small waves and the tail can adjust the pitch trim so that over the long term the flap deflection returns to neutral. This maximizes the flap's effectiveness for dynamic ride control, and the steady state flap deflection can correspond to the optimum angle for minimizing foil profile drag.

Most importantly however: I found last year sailing with a mechanical system that I seemed to be hitting a hard wall regarding max speed. Contrary to all the text books the drag appears to be going up far faster than V^2.

Pitch control is very important for hydrofoil peformance, especially if you are using surface piercing foils or if the flap doesn't span the full width of the forward foil. At constant lift, the induced drag should decrease with the square of the speed - this is the whole point of using hydrofoils at high speed. But if the effective span shrinks with speed, the induced drag can actually go up. Pitch control can be important for flying lower and increasing the effective span to reduce induced drag more than the increase in parasite drag due to extra wetted area.

Whilst tail control has inferior height control it has superior pitch control and the biggest disturbances seen by a dinghy foiler are pitch disturbances due to the height of the rig above the CoG and the foils.

To meet my objective of a boat that can be easily flown in a wide range of conditions with a system that can be scaled to a larger craft, it may be necessary to control both foils.

 

[atypicalguy]

If you were trying to achieve precise positioning in the horizontal plane, you'd want direct side force control then, too.
There are really two coupled modes to the boat's motion you're trying to control - a pitch mode and a heave mode. With one control, you can only get at one mode by the way in which it is coupled to the other mode. With two controls, you can control each mode directly. And with the additional control you can satisfy an additional objective, such as minimizing drag.

The control of height using tail control will always have a lag compared to controlling height with the main foil flap. The reason is to change height, you need to change the vertical velocity, and to change the vertical velocity you need to change the vertical acceleration by changing the lift on the foil. If you have a flap on the foil, when you change the flap deflection, you change the lift and create an immediate change to the vertical acceleration. If you change the lift through the changing the pitch attitude of the boat to control the angle of attack of the foil, then you first have to generate a pitch acceleration to generate a pitch rate to generate a change in pitch attitude. Only once the pitch attitude changes do you change the lift on the foil and change the vertical acceleration and start to affect the height.

But it's worse than that. With tail control, as opposed to a canard, the tail has to drop to increase the angle of attack. So the boat actually has to descend slightly before it can start to rise. This has significant implications for the stability of control loops.

It's simply not possible to get as tight a height control using only the rudder foil compared to controlling only the main foil flap. The lags in the height response to pitch control mean that the boat will go unstable if the height control is cranked up too high.

However, height control using the flap is also subject to serious limitations. The flap only has limited authority. The lift on the foil is a function not only of angle of attack but of speed. Since the lift has to equal the weight, as the speed increases, the flap has to be deflected to offset the increase in lift due to speed. Eventually the flap will be fully saturated just trying to maintain the trim of the boat, and even before then, any deflection for trim takes away from the authority available to counter dynamic disturbances. Tail control doesn't have quite as much limitation in this regard. There's not much difference in angle of attack required to climb or descend at a constant angle, so once the pitch attitude is set, the tail control can return to near its trim value as the height changes. So over the long term, the tail can be much more powerful than the flap.

The combination of characteristics means the flap and tail controls can be used in complementary ways. The flap can null out high-frequency disturbances from small waves and the tail can adjust the pitch trim so that over the long term the flap deflection returns to neutral. This maximizes the flap's effectiveness for dynamic ride control, and the steady state flap deflection can correspond to the optimum angle for minimizing foil profile drag.

Most importantly however: I found last year sailing with a mechanical system that I seemed to be hitting a hard wall regarding max speed. Contrary to all the text books the drag appears to be going up far faster than V^2.

Pitch control is very important for hydrofoil peformance, especially if you are using surface piercing foils or if the flap doesn't span the full width of the forward foil. At constant lift, the induced drag should decrease with the square of the speed - this is the whole point of using hydrofoils at high speed. But if the effective span shrinks with speed, the induced drag can actually go up. Pitch control can be important for flying lower and increasing the effective span to reduce induced drag more than the increase in parasite drag due to extra wetted area.

Whilst tail control has inferior height control it has superior pitch control and the biggest disturbances seen by a dinghy foiler are pitch disturbances due to the height of the rig above the CoG and the foils.

To meet my objective of a boat that can be easily flown in a wide range of conditions with a system that can be scaled to a larger craft, it may be necessary to control both foils.

I agree with Clive. Even with a pivoting daggerboard I spend a lot of time managing pitch-induced phenomena.

 

[Doug Lord]

Sketch by Tom Speer from boatdesign.net-I'm using a system similar to this to further explore manual control:

 

[BalticBandit]

Sketch by Tom Speer from boatdesign.net-I'm using a system similar to this to further explore manual control:

No one cares.

 

[atypicalguy]

If you were trying to achieve precise positioning in the horizontal plane, you'd want direct side force control then, too.
There are really two coupled modes to the boat's motion you're trying to control - a pitch mode and a heave mode. With one control, you can only get at one mode by the way in which it is coupled to the other mode. With two controls, you can control each mode directly. And with the additional control you can satisfy an additional objective, such as minimizing drag.

The control of height using tail control will always have a lag compared to controlling height with the main foil flap. The reason is to change height, you need to change the vertical velocity, and to change the vertical velocity you need to change the vertical acceleration by changing the lift on the foil. If you have a flap on the foil, when you change the flap deflection, you change the lift and create an immediate change to the vertical acceleration. If you change the lift through the changing the pitch attitude of the boat to control the angle of attack of the foil, then you first have to generate a pitch acceleration to generate a pitch rate to generate a change in pitch attitude. Only once the pitch attitude changes do you change the lift on the foil and change the vertical acceleration and start to affect the height.

But it's worse than that. With tail control, as opposed to a canard, the tail has to drop to increase the angle of attack. So the boat actually has to descend slightly before it can start to rise. This has significant implications for the stability of control loops.

It's simply not possible to get as tight a height control using only the rudder foil compared to controlling only the main foil flap. The lags in the height response to pitch control mean that the boat will go unstable if the height control is cranked up too high.

However, height control using the flap is also subject to serious limitations. The flap only has limited authority. The lift on the foil is a function not only of angle of attack but of speed. Since the lift has to equal the weight, as the speed increases, the flap has to be deflected to offset the increase in lift due to speed. Eventually the flap will be fully saturated just trying to maintain the trim of the boat, and even before then, any deflection for trim takes away from the authority available to counter dynamic disturbances. Tail control doesn't have quite as much limitation in this regard. There's not much difference in angle of attack required to climb or descend at a constant angle, so once the pitch attitude is set, the tail control can return to near its trim value as the height changes. So over the long term, the tail can be much more powerful than the flap.

The combination of characteristics means the flap and tail controls can be used in complementary ways. The flap can null out high-frequency disturbances from small waves and the tail can adjust the pitch trim so that over the long term the flap deflection returns to neutral. This maximizes the flap's effectiveness for dynamic ride control, and the steady state flap deflection can correspond to the optimum angle for minimizing foil profile drag.

Most importantly however: I found last year sailing with a mechanical system that I seemed to be hitting a hard wall regarding max speed. Contrary to all the text books the drag appears to be going up far faster than V^2.

Pitch control is very important for hydrofoil peformance, especially if you are using surface piercing foils or if the flap doesn't span the full width of the forward foil. At constant lift, the induced drag should decrease with the square of the speed - this is the whole point of using hydrofoils at high speed. But if the effective span shrinks with speed, the induced drag can actually go up. Pitch control can be important for flying lower and increasing the effective span to reduce induced drag more than the increase in parasite drag due to extra wetted area.

Whilst tail control has inferior height control it has superior pitch control and the biggest disturbances seen by a dinghy foiler are pitch disturbances due to the height of the rig above the CoG and the foils.

To meet my objective of a boat that can be easily flown in a wide range of conditions with a system that can be scaled to a larger craft, it may be necessary to control both foils.

I agree with Clive. Even with a pivoting daggerboard I spend a lot of time managing pitch-induced phenomena.

OK I reserve the right to disagree with myself. If my mainfoil flies like a stabilator it has just as much control over pitch as the rudder would, and even more really, because it just parks the nose of the boat a certain distance from the water (ideally). That in turn sets the AOA on the rudder, which is really just along for the ride. Tempting to call it a canard setup but in the end that terminology is just so many angels dancing on the head of a pin. Or was that 'angles'?

 

[The Black Pearl]

Angels dancing on the head of a pin, that's just what it feels like when it all goes right......

 

[bgulari]

If you were trying to achieve precise positioning in the horizontal plane, you'd want direct side force control then, too.
There are really two coupled modes to the boat's motion you're trying to control - a pitch mode and a heave mode. With one control, you can only get at one mode by the way in which it is coupled to the other mode. With two controls, you can control each mode directly. And with the additional control you can satisfy an additional objective, such as minimizing drag.

The control of height using tail control will always have a lag compared to controlling height with the main foil flap. The reason is to change height, you need to change the vertical velocity, and to change the vertical velocity you need to change the vertical acceleration by changing the lift on the foil. If you have a flap on the foil, when you change the flap deflection, you change the lift and create an immediate change to the vertical acceleration. If you change the lift through the changing the pitch attitude of the boat to control the angle of attack of the foil, then you first have to generate a pitch acceleration to generate a pitch rate to generate a change in pitch attitude. Only once the pitch attitude changes do you change the lift on the foil and change the vertical acceleration and start to affect the height.

But it's worse than that. With tail control, as opposed to a canard, the tail has to drop to increase the angle of attack. So the boat actually has to descend slightly before it can start to rise. This has significant implications for the stability of control loops.

It's simply not possible to get as tight a height control using only the rudder foil compared to controlling only the main foil flap. The lags in the height response to pitch control mean that the boat will go unstable if the height control is cranked up too high.

However, height control using the flap is also subject to serious limitations. The flap only has limited authority. The lift on the foil is a function not only of angle of attack but of speed. Since the lift has to equal the weight, as the speed increases, the flap has to be deflected to offset the increase in lift due to speed. Eventually the flap will be fully saturated just trying to maintain the trim of the boat, and even before then, any deflection for trim takes away from the authority available to counter dynamic disturbances. Tail control doesn't have quite as much limitation in this regard. There's not much difference in angle of attack required to climb or descend at a constant angle, so once the pitch attitude is set, the tail control can return to near its trim value as the height changes. So over the long term, the tail can be much more powerful than the flap.

The combination of characteristics means the flap and tail controls can be used in complementary ways. The flap can null out high-frequency disturbances from small waves and the tail can adjust the pitch trim so that over the long term the flap deflection returns to neutral. This maximizes the flap's effectiveness for dynamic ride control, and the steady state flap deflection can correspond to the optimum angle for minimizing foil profile drag.

Most importantly however: I found last year sailing with a mechanical system that I seemed to be hitting a hard wall regarding max speed. Contrary to all the text books the drag appears to be going up far faster than V^2.

Pitch control is very important for hydrofoil peformance, especially if you are using surface piercing foils or if the flap doesn't span the full width of the forward foil. At constant lift, the induced drag should decrease with the square of the speed - this is the whole point of using hydrofoils at high speed. But if the effective span shrinks with speed, the induced drag can actually go up. Pitch control can be important for flying lower and increasing the effective span to reduce induced drag more than the increase in parasite drag due to extra wetted area.

Whilst tail control has inferior height control it has superior pitch control and the biggest disturbances seen by a dinghy foiler are pitch disturbances due to the height of the rig above the CoG and the foils.

To meet my objective of a boat that can be easily flown in a wide range of conditions with a system that can be scaled to a larger craft, it may be necessary to control both foils.

I agree with Clive. Even with a pivoting daggerboard I spend a lot of time managing pitch-induced phenomena.

OK I reserve the right to disagree with myself. If my mainfoil flies like a stabilator it has just as much control over pitch as the rudder would, and even more really, because it just parks the nose of the boat a certain distance from the water (ideally). That in turn sets the AOA on the rudder, which is really just along for the ride. Tempting to call it a canard setup but in the end that terminology is just so many angels dancing on the head of a pin. Or was that 'angles'?

careful douggie will call you insane

 

[atypicalguy]

If you were trying to achieve precise positioning in the horizontal plane, you'd want direct side force control then, too.
There are really two coupled modes to the boat's motion you're trying to control - a pitch mode and a heave mode. With one control, you can only get at one mode by the way in which it is coupled to the other mode. With two controls, you can control each mode directly. And with the additional control you can satisfy an additional objective, such as minimizing drag.

The control of height using tail control will always have a lag compared to controlling height with the main foil flap. The reason is to change height, you need to change the vertical velocity, and to change the vertical velocity you need to change the vertical acceleration by changing the lift on the foil. If you have a flap on the foil, when you change the flap deflection, you change the lift and create an immediate change to the vertical acceleration. If you change the lift through the changing the pitch attitude of the boat to control the angle of attack of the foil, then you first have to generate a pitch acceleration to generate a pitch rate to generate a change in pitch attitude. Only once the pitch attitude changes do you change the lift on the foil and change the vertical acceleration and start to affect the height.

But it's worse than that. With tail control, as opposed to a canard, the tail has to drop to increase the angle of attack. So the boat actually has to descend slightly before it can start to rise. This has significant implications for the stability of control loops.

It's simply not possible to get as tight a height control using only the rudder foil compared to controlling only the main foil flap. The lags in the height response to pitch control mean that the boat will go unstable if the height control is cranked up too high.

However, height control using the flap is also subject to serious limitations. The flap only has limited authority. The lift on the foil is a function not only of angle of attack but of speed. Since the lift has to equal the weight, as the speed increases, the flap has to be deflected to offset the increase in lift due to speed. Eventually the flap will be fully saturated just trying to maintain the trim of the boat, and even before then, any deflection for trim takes away from the authority available to counter dynamic disturbances. Tail control doesn't have quite as much limitation in this regard. There's not much difference in angle of attack required to climb or descend at a constant angle, so once the pitch attitude is set, the tail control can return to near its trim value as the height changes. So over the long term, the tail can be much more powerful than the flap.

The combination of characteristics means the flap and tail controls can be used in complementary ways. The flap can null out high-frequency disturbances from small waves and the tail can adjust the pitch trim so that over the long term the flap deflection returns to neutral. This maximizes the flap's effectiveness for dynamic ride control, and the steady state flap deflection can correspond to the optimum angle for minimizing foil profile drag.

Most importantly however: I found last year sailing with a mechanical system that I seemed to be hitting a hard wall regarding max speed. Contrary to all the text books the drag appears to be going up far faster than V^2.

Pitch control is very important for hydrofoil peformance, especially if you are using surface piercing foils or if the flap doesn't span the full width of the forward foil. At constant lift, the induced drag should decrease with the square of the speed - this is the whole point of using hydrofoils at high speed. But if the effective span shrinks with speed, the induced drag can actually go up. Pitch control can be important for flying lower and increasing the effective span to reduce induced drag more than the increase in parasite drag due to extra wetted area.

Whilst tail control has inferior height control it has superior pitch control and the biggest disturbances seen by a dinghy foiler are pitch disturbances due to the height of the rig above the CoG and the foils.

To meet my objective of a boat that can be easily flown in a wide range of conditions with a system that can be scaled to a larger craft, it may be necessary to control both foils.

I agree with Clive. Even with a pivoting daggerboard I spend a lot of time managing pitch-induced phenomena.

OK I reserve the right to disagree with myself. If my mainfoil flies like a stabilator it has just as much control over pitch as the rudder would, and even more really, because it just parks the nose of the boat a certain distance from the water (ideally). That in turn sets the AOA on the rudder, which is really just along for the ride. Tempting to call it a canard setup but in the end that terminology is just so many angels dancing on the head of a pin. Or was that 'angles'?

careful douggie will call you insane

I thought he didn't give compliments? How are rudders coming?

 

[Phil S]

"Pitch control is very important for hydrofoil peformance, especially if you are using surface piercing foils or if the flap doesn't span the full width of the forward foil. At constant lift, the induced drag should decrease with the square of the speed - this is the whole point of using hydrofoils at high speed. But if the effective span shrinks with speed, the induced drag can actually go up. Pitch control can be important for flying lower and increasing the effective span to reduce induced drag more than the increase in parasite drag due to extra wetted area."

Disagree.

In my last 4 years of racing foil moths I think all my crashes were due to either"

Excess height due to friction, lag or poor settings in wand/flap linkage, or

wave troughs deeper than centreboard length enabling main foil to aerate when I did not manage to steer around them, or

Poor roll control in manoevres like gybes, or

Bad sailing.

Pitch stability is very well controlled by the aft foil without any adjustment, just as it is in a well trimmed aeroplane. Variations in rig drive are adequately managed by an efficient wand/flap mechanical system. In fact rear foils are getting smaller without detriment to pitch control.

Suggest that development of this hybrid, and moth illegal control system should take into account what is really happenning in the competitive end of the moth fleet, and not just a few brief encounters either on the water or via the www.

Bladerider has proven that simple but efficient mechanical systems which are easilly managed by saiors without necessarilly full understanding, make for more sucesful foiling sailors and a wider market appeal. Complex electonic systems with associated maintenace issues are not needed.

 

[Doug Lord]

Complex electonic systems with associated maintenace issues are not needed.

===============

Typical Philism. Who is to define what is needed? You have said that manual control is not only not needed but won't work. Only thing is a working manual system would likely beat a wand(and IS legal in the Moth Class). There are many extraordinary developments that may increase speed, make it easier to foil or both and God help us if they weren't tried because they weren't legal in the Moth Class. Go Clive!

 

[Phil S]

Doug,

I have done maybe 500 hours of foil sailing in the last 5 years, designed built and tried many different foils and systems, configurations and arrangements. All done in a competitive competition environment where success can be measured and failures made obvious for what they are. I do not win much but I am prepared to learn from others who do better than me.

Doug, just what have you done to make you such an expert?

(Do not bother answering me direct as I will have you back on ignore.)

 

[Doug Lord]

Doug,I have done maybe 500 hours of foil sailing in the last 5 years, designed built and tried many different foils and systems, configurations and arrangements. All done in a competitive competition environment where success can be measured and failures made obvious for what they are. I do not win much but I am prepared to learn from others who do better than me.

Doug, just what have you done to make you such an expert?

(Do not bother answering me direct as I will have you back on ignore.)

======================

And you've been very,very wrong in your past expert predictions about large foilers and now about manual control and electronic developments. I don't need to be an expert to see what you've said with your own words and that has been proven wrong by numerous experimenters.

Thats not to say you aren't a Great Man; you are. Just wrong about some important aspects of foiler development.

 

[the_skiff_devil]

GTFO troll.

You advocate manual control of foils. This is about electronic automated foil control as an alternative to mechanical systems. Big difference.

You have no expertise on this topic. Come back when someone could give a fornicating rodent's rectum about what you have to say.

 

[SimonN]

And you've been very,very wrong in your past expert predictions about large foilers and now about manual control and electronic developments. I don't need to be an expert to see what you've said with your own words and that has been proven wrong by numerous experimenters.Thats not to say you aren't a Great Man; you are. Just wrong about some important aspects of foiler development.

And you, who has no track record of building multiple succesful foilers, including designing and building your own foils, claims to be always right! Actions speak louder than words and while you try your ideas on this forum, Phil tries them on the water. And while Phil might occasionally be wrong (and usually he admits when that has happened), how often can you prove you are right? The answer is simple. You cannot prove you are right because you are not out there sailing foilers you have developed and you aren't actually trying your ideas for real. They are all still sitting in a workshop, although that seems a grand term to describe what appears to be little mnore than a garage used for storage.

 

[atypicalguy]

Disagree. In my last 4 years of racing foil moths I think all my crashes were due to either"

Excess height due to friction, lag or poor settings in wand/flap linkage, or

wave troughs deeper than centreboard length enabling main foil to aerate when I did not manage to steer around them, or

Poor roll control in manoevres like gybes, or

Bad sailing.

Pitch stability is very well controlled by the aft foil without any adjustment, just as it is in a well trimmed aeroplane. Variations in rig drive are adequately managed by an efficient wand/flap mechanical system. In fact rear foils are getting smaller without detriment to pitch control.

Phil I think if you actually measured the variation in pitch on your boat as it is foiling you would find there are rather large variations, particularly offwind overtaking waves, which contribute to the boat's excess height and crash. But it is only a guess as I have no accelerometers or gyros either.

 

[Phil S]

Karl,

Some automated pitch respose only when boat tries to follow surface of large rolling waves. If they are big enough then the boat can follow down troughs and up to the peaks, but mostly they are smaller.

Dilemma for control system and skipper is to distinguish between those small enough to ignore, (ie shallower trough to median less than foil depth below design ride level), and those waves which are deeper but too short to allow the wand and rudder foil to retrim pitch and follow the contour. Then if the skipper does not take action the foil can break surface and the boat will crash. What we do to adjust pitch in this case is move weight, sail lower by strategic trimming bow down with rudder foil, or heal and steer to use the vertical rudder as pitch control. Mostly we try to steer around the big holes we can see ahead of the boat.

It all happens very quickly, at 20 knots a moth does three boat lengths a second, if the mid size dilemma waves are about 0.5m deep they are probably about a boat length peak to peak, so we are passing 3 waves a second at that speed which is too fast for wand or skipper reaction, so avoiding the troughs or going slower and lower are the safer options.

I do not see how the elecronic sysyem can decide whether or not to change pitch based on the trough depth just ahead of the boat. If it reacts to pitch changes it might be contradicting the boats desire to follow a big safe rolling wave or reacting against the skippers intention to heal and track down a hole he can not steer around.

It is crasy to think any control system whether mechanical or electronic will be able to change the pitch of the boat to steer up and down 0.5m waves at a frequency of 3 per second or more. The loads and forces needed to move the total boat mass up and down this distance at those frequencies are just too much for the foil structures and the skipper's stomach.

 

[atypicalguy]

Karl,Some automated pitch respose only when boat tries to follow surface of large rolling waves. If they are big enough then the boat can follow down troughs and up to the peaks, but mostly they are smaller.

There is a great photo of Scott from Garda bearing off at a windward mark with his bow waaay up in the air...I think there is something about the cyclical flow of water in a wave which provides more lift as the mainfoil approaches the crest, either that or the boat pitches up enough in climbing over the wave that the wand/flap cannot scrub enough lift to bring it back down quickly.

It is crasy to think any control system whether mechanical or electronic will be able to change the pitch of the boat to steer up and down 0.5m waves at a frequency of 3 per second or more. The loads and forces needed to move the total boat mass up and down this distance at those frequencies are just too much for the foil structures and the skipper's stomach.

Well there's a lot in that statement.

In short, you don't have to change the pitch of the boat to accomplish that - you only need to change the pitch of the foil. I do pretty well overtaking waves sailing really fast. It's when I slow down to gybe that the problems appear!

You are right about the skipper's stomach or more accurately the skipper's inner ear - it is really hard to gybe a boat that is bouncing up and down all over the place several times per second! Very rodeo-esque, but the bull weighs only 70 lb and the landing is much softer!

My control system does pretty much what you describe as crazy Phil. Really it is not that far fetched. The materials are plenty strong enough to handle it. I have my share of problems but the behavior you describe is readily achievable.

 

[aus_stevo]

My control system does pretty much what you describe as crazy Phil. Really it is not that far fetched. The materials are plenty strong enough to handle it. I have my share of problems but the behavior you describe is readily achievable.

is it faster?