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      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  
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tdarcy

Interesting......let the foiling wars begin

77 posts in this topic

.

 

hmmmmm, a jib will make tacks.... interesting.

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Very cool!

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.

 

hmmmmm, a jib will make tacks.... interesting.

I think that's an assym.....

 

Hmmmmm, raises more questions than answers. <;~\

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Why is it so big? 80kg is a hell of a weight for a single hander to haul up the beach at my club. That's the point in the day I'm very happy to have an Aero at less than half that. Also not sure how you'd right unaided it if it turtled?

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.

 

...it's kinda cool to see those beautiful long hulls flying around,,,

 

...but sorta ironic at the same time.

 

It seems the size and weight is there to accommodate the sailplan....which is there to accommodate the size and weight <;~\

 

I'm certainly no 'spert, but quite possibly some other issues to have the wand that far back, when others find an improved ride for having it as far fwd as possible...or maybe this is breakthrough technology!?

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.

 

...it's kinda cool to see those beautiful long hulls flying around,,,

 

...but sorta ironic at the same time.

 

It seems the size and weight is there to accommodate the sailplan....which is there to accommodate the size and weight <;~\

 

I'm certainly no 'spert, but quite possibly some other issues to have the wand that far back, when others find an improved ride for having it as far fwd as possible...or maybe this is breakthrough technology!?

Not sure if it's even a break even technology

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Forgive my ignorance, but wouldn't you want the wand in front of the foil to adjust to wave height before the foil was affected by it?

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If a foiling boat looks anything like a non-foiling boat, it's wrong.

 

A few more years and everyone will realize this. We are still in the transition phase, where our historical esthetic patterns are still the well we go to, and expect.

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Forgive my ignorance, but wouldn't you want the wand in front of the foil to adjust to wave height before the foil was affected by it?

 

This is what the F101 people say about a couple of features of their boat: http://www.foiling101.com/

SO WHY THREE HULLS?

 

Many Moths use buoyancy in the wings to help sailors get to grips with the boat, but this buoyancy is limited to helping the helm recover the boat from a capsize and does nothing to prevent the capsize in the first place. The F101 Tri configuration allows for a slender hull with enough length to prevent pitch poling, while at the same time creating a stable platform to allow novices to get out on the water with no previous foiling experience. The super slender wave-piercing outer hulls are set at an optimum angle to initiate foiling - simply sit on the windward hull, which will cant the boat to windward, then sheet in and take off! If the F101 does pitch forward, the main hull is designed to recover straight back onto the foils; the hull’s additional length keeps the angle of incidence shallow. Its rocker is matched to the angle of incidence – and the additional buoyancy forwards help lift the bow. The benefit applies to the outer hulls too - if the F101 falls in to windward, the windward hull lifts the boat back onto the foils. If the boat falls in to leeward there is enough buoyancy to prevent a capsize and the boat is quickly back on the foils.

WHY IS THE WAND ON THE TRAILING EDGE OF THE MAIN FOIL? *

 

The F101 has its control wand fixed to the back of the trailing edge of the main foil, as opposed to the mounted at the bow which is where Moth’s mount the foil. There are a number of advantages to the trailing edge position, the most important of which is that the wand measures the ride height of the boat irrespective of pitch. This important factor can help to eliminate the porpoise effect which many beginners experience when learning to sail a Moth.

 

* Raves, Osprey, Skat ,Whisper and Laser all use midship wands......

 

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Don't recall ever porpoising when sailing a moth even when learning. Probably cheaper to mount near foil rather than better

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Porpoising "problem" aside, can the foil mast be retracted into the boat? I could see a real advantage to having the wand mounted directly to and behind the foil mast: all the linkages for controlling the foil are internal to the foil mast, nothing goes outside through the hull to an external wand. Launch and recovery about 100% easier if fully retractable I would think, especially with the trimaran design.

 

EDIT:

 

Reading the site answered that question. Indeed it is #1 on the list of design features:

 

WHAT ARE THE SPECIFIC DESIGN FEATURES?
  • The foils should be retractable so that the boat can be launched from a regular trolley in shallow water

  • The mainsail should be able to be hoisted by halyard and, crucially, the sail should be easily dropped when coming on to a lee shore

  • The hull should be long enough to prevent nose diving

  • The design must be robust and reliable

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* Raves, Osprey, Skat ,Whisper and Laser all use midship wands......

 

 

 

 

....this makes it a good thing!? :mellow::lol:

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yes, a very good thing

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If a foiling boat looks anything like a non-foiling boat, it's wrong.

 

A few more years and everyone will realize this. We are still in the transition phase, where our historical esthetic patterns are still the well we go to, and expect.

https://s-media-cache-ak0.pinimg.com/originals/a0/d8/38/a0d838e68775f025ee8829f5786d76cd.jpg yes, should look like this

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Now that looks like fun!

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If you built a control system with sensor trailing the actuator you would

Get laughed out of controls class. From my memory response improves up to around two wavelengths of the fundamental frequency with lead. Past that great reduction in improvement. But believe the hype of someone who is using other compromised foiling boats as proof what a good idea it is. Where's the video instead of single pictures

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It's kind of Ironic how they had to build expensive hulls to accommodate for the shortcuts they took in designing the control system.

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If you built a control system with sensor trailing the actuator you would

Get laughed out of controls class. From my memory response improves up to around two wavelengths of the fundamental frequency with lead. Past that great reduction in improvement. But believe the hype of someone who is using other compromised foiling boats as proof what a good idea it is. Where's the video instead of single pictures

 

What nonsense!

 

Whisper with trailing wands:

 

 

 

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From what I can see the question is are you trying to deal with waves or changes in height of the system.

Having the wand ahead allows it to 'see the wave coming' and presumably lifts the foiler up as the wave comes through.

If on the other hand the control system is damped so that it does not respond to each wave but aims to maintain a height over the average wave height, then it doesn't really matter if the wand is ahead of the foil or not. (in this case the wand is not truly 'trailing' the actuator any more than a thermocouple in an oven is trailing the actuator because its measuring the oven temperature down stream of the heating element.)

 

Placing the wand ahead of the foils also makes it susceptible to changes in pitch of the foiler, I don't know if that a good or bad thing

.

I suspect that the answer depends on what you are designing the control system to do.

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One of the best comments about having the wand forward of the foil is this one by Steve Clark talking about the UFO design and development:

 

In the interest of disclosure, we tried a trailing wand.

It has some nice features relative to usability. There are no connections to make up, and the wand tucks nicely behind the mai strut when you withdraw the strut.

But we discarded it after we saw how the wake of the strut played havoc with the wand.

Further by having the paddle back at the center of pitch rotation, pitch changes aren't caught by the surface sensor.

Pitch affects main foil angle of attack, which drives lift, and is as critical as the flap angle.

Moving the wand paddle forward makes main foil react to pitch changes as well as ride height.

Works better.

SHC

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One of the problems with the "see the wave coming" rationale is the speed of the boat and the reaction time of the wand/flap combination. It appears to be well proven in the Moth Class that a wand mounted on a bowsprit works well. It probably has more to do with Steves rationale :

 

 

"time to react to the waves"? Seems like there must be advantages to the bowsprit wand but I can't see this as one of them?

 

If the tip of the wand touches the water 5' in front of the main foil

-at 10 knots the boat is moving 16.86' sec, so a wave that moves the wand is already past the foil by the time it moves(time for wand to move flap(.3 sec)

-at 15 knots 25.3' sec( time for wand to move flap.2 second)

-at 20 knots 33.73' sec (time for wand to move flap .15 sec)

 

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If you built a control system with sensor trailing the actuator you would

Get laughed out of controls class. From my memory response improves up to around two wavelengths of the fundamental frequency with lead. Past that great reduction in improvement. But believe the hype of someone who is using other compromised foiling boats as proof what a good idea it is. Where's the video instead of single pictures

 

What nonsense!

 

 

 

I was late to class today. Is "bgulari" THE B. Gulari?! The same one that Doug Lord is saying is nonsense?

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^

 

Apparently. The horror of this is that in this instance I think Doug Lord is right. There, I said it.

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If you built a control system with sensor trailing the actuator you would

Get laughed out of controls class. From my memory response improves up to around two wavelengths of the fundamental frequency with lead. Past that great reduction in improvement. But believe the hype of someone who is using other compromised foiling boats as proof what a good idea it is. Where's the video instead of single pictures

 

What nonsense!

 

 

 

I was late to class today. Is "bgulari" THE B. Gulari?! The same one that Doug Lord is saying is nonsense?

 

 

actually you could argue that DL became THE Doug Lord after a shitfight with THE BL

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If you built a control system with sensor trailing the actuator you would

Get laughed out of controls class. From my memory response improves up to around two wavelengths of the fundamental frequency with lead. Past that great reduction in improvement. But believe the hype of someone who is using other compromised foiling boats as proof what a good idea it is. Where's the video instead of single pictures

 

What nonsense!

 

Whisper with trailing wands:

 

 

 

 

 

.......yer got a video of that boat in actual waves?

 

Gotta wonder why their promo vids are in protected waters, minimal wind. :wacko:

 

 

^

 

Apparently. The horror of this is that in this instance I think Doug Lord is right. There, I said it.

 

 

...depends who you listen to and what their priorities are.

 

Some prefer to have pitch accounted for, others prefer manufacturing convenience.

 

...and only complete twits use Rave and Laser foil systems as examples of what works! :lol:

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One of the problems with the "see the wave coming" rationale is the speed of the boat and the reaction time of the wand/flap combination. It appears to be well proven in the Moth Class that a wand mounted on a bowsprit works well. It probably has more to do with Steves rationale :

 

 

"time to react to the waves"? Seems like there must be advantages to the bowsprit wand but I can't see this as one of them?

 

If the tip of the wand touches the water 5' in front of the main foil

-at 10 knots the boat is moving 16.86' sec, so a wave that moves the wand is already past the foil by the time it moves(time for wand to move flap(.3 sec)

-at 15 knots 25.3' sec( time for wand to move flap.2 second)

-at 20 knots 33.73' sec (time for wand to move flap .15 sec)

 

 

Makes sense.

from this it seems its best to think of the wand has handling average height above water in all cases, and also pitch when placed away from the center of pitch rotation, with the separation affecting sensitivity. I.e. long way forward gives a big reaction to a pitch change, near the center of rotation gives little or no reaction.

 

It may even be that what you want depends on the skill of the sailor :).'

 

cool, learn something new every day.

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One of the problems with the "see the wave coming" rationale is the speed of the boat and the reaction time of the wand/flap combination. It appears to be well proven in the Moth Class that a wand mounted on a bowsprit works well. It probably has more to do with Steves rationale :

 

 

"time to react to the waves"? Seems like there must be advantages to the bowsprit wand but I can't see this as one of them?

 

If the tip of the wand touches the water 5' in front of the main foil

-at 10 knots the boat is moving 16.86' sec, so a wave that moves the wand is already past the foil by the time it moves(time for wand to move flap(.3 sec)

-at 15 knots 25.3' sec( time for wand to move flap.2 second)

-at 20 knots 33.73' sec (time for wand to move flap .15 sec)

 

 

Makes sense.

from this it seems its best to think of the wand has handling average height above water in all cases, and also pitch when placed away from the center of pitch rotation, with the separation affecting sensitivity. I.e. long way forward gives a big reaction to a pitch change, near the center of rotation gives little or no reaction.

 

It may even be that what you want depends on the skill of the sailor :).'

 

cool, learn something new every day.

 

 

Good comment!

One of the things Steve mentioned was that they tried a trailing wand on the UFO and found the wake from the daggerboard played havoc with the wand. Which is interesting when you look at the Rave, Osprey and Skat systems because those boats have the wand attached(midships) to the daggerboard but on the side so the board wake can't interfere with the wand and the wand wake can't interfere with the board or rudder.

But that doesn't explain how the Whisper system works so well-where the wands appear to be right in the wake of the daggerboard- except that they appear to touch the water quite a ways aft of the foil.

And I still don't quite get why pitch coupling with altitude is a good thing on the boats with the wand way forward like the Moth, S9 cat, and Vampire cat-which works well on those boats.The F101 guys have ,apparently, noticed negative effects of pitch coupling on the Moth-they are skilled sailors as well. But other skilled sailors swear by the forward wand.

Steve came closest to a plausible explanation but it is exactly opposite of what Dr. Bradfields design theory was(as I understood it) : avoid pitch coupling-- let the rudder t-foil handle pitch and the wand handle altitude 100%. His system also works very well on the Rave, Osprey and SKAT. Interesting stuff.......

 

Bradfield planing midships wand mounted to side of daggerboard:

 

28jllc2.jpg

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All good in theory until you sail actually sail a real moth with the gearing adjusted right up. Going thru 2 or 3 powerboat waves feels like jumping speed humps in a car park. Put the wand behind the foil and the bumps would come after you have already passed them.

Fractions of a sec might sound insignificant, but lots happens in that time and when you are tuned into it, the fractions of gains all add up.

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All good in theory until you sail actually sail a real moth with the gearing adjusted right up. Going thru 2 or 3 powerboat waves feels like jumping speed humps in a car park. Put the wand behind the foil and the bumps would come after you have already passed them.

Fractions of a sec might sound insignificant, but lots happens in that time and when you are tuned into it, the fractions of gains all add up.

cool,

 

the question I have is, is it better to go over the speed humps or is it possible to go straight through them

I know in boarder cross typically you try to keep your CoG moving through a bump (letting your legs flex to maintain as near as possible a constant velocity through the bump). Is there any merit in the idea of trying letting the foiler stay straight as the wave passes through rather than moving the whole mass up and down as the wave passes. I'm assuming there are significant risks with this as well, and again it may depend on how the foiler is intended to be used.

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All good in theory until you sail actually sail a real moth with the gearing adjusted right up. Going thru 2 or 3 powerboat waves feels like jumping speed humps in a car park. Put the wand behind the foil and the bumps would come after you have already passed them.

Fractions of a sec might sound insignificant, but lots happens in that time and when you are tuned into it, the fractions of gains all add up.

cool,

 

the question I have is, is it better to go over the speed humps or is it possible to go straight through them

I know in boarder cross typically you try to keep your CoG moving through a bump (letting your legs flex to maintain as near as possible a constant velocity through the bump). Is there any merit in the idea of trying letting the foiler stay straight as the wave passes through rather than moving the whole mass up and down as the wave passes. I'm assuming there are significant risks with this as well, and again it may depend on how the foiler is intended to be used.

 

 

 

take a look

 

http://youtu.be/Yq83PVulc-Y

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All good in theory until you sail actually sail a real moth with the gearing adjusted right up. Going thru 2 or 3 powerboat waves feels like jumping speed humps in a car park. Put the wand behind the foil and the bumps would come after you have already passed them.

Fractions of a sec might sound insignificant, but lots happens in that time and when you are tuned into it, the fractions of gains all add up.

cool,

 

the question I have is, is it better to go over the speed humps or is it possible to go straight through them

I know in boarder cross typically you try to keep your CoG moving through a bump (letting your legs flex to maintain as near as possible a constant velocity through the bump). Is there any merit in the idea of trying letting the foiler stay straight as the wave passes through rather than moving the whole mass up and down as the wave passes. I'm assuming there are significant risks with this as well, and again it may depend on how the foiler is intended to be used.

That's exactly what a wand does.

For some reason there is a misconception in this thread that a wand is for handling wave management, that is not the case.

The wand handles height management independently of wave action.

When the hull is waterborne the wand tells the foil to creat more lift by trimming the flaps down. The opposite when the foil rides too high to the surface. It auto levels the ride right where it should be.

this is true in both flat and choppy water.

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The bumpiness can be felt big time on a Rave in short steep chop. The flap is moving up and down fast as the boat goes over the chop and the pulses of lift and downforce are felt like a truck driving over a bumpy dirt road. But there is a solution and that is manual control-that way the wand isn't moving the flap- the skipper is- so it won't move as fast or as frequently. Two Raves were converted to manual control and they were faster in racing than the wand equipped boats. I've got a lot of hours in a Rave but never got to sail the manual controlled version but I talked at length to one of the guys involved. The system uses two joysticks each one controlling one main foil. On the Rave, the foils develop all the righting moment so the joysticks not only control altitude but roll(righting moment) as well. You use your feet to steer....

Some say manual control is impossible in a Moth-I don't believe it-but it hasn't been successfully used in Moth racing as far as I know. David Lugg flew an I-14 using manual altitude control in 1999 as an experiment and, of course, the AC boats have the foil rake(altitude) controlled by the skipper.

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The bumpiness can be felt big time on a Rave in short steep chop. But there is a solution and that is manual control-that way the wand isn't moving the flap- the skipper is- so it won't move as fast or as frequently. Two Raves were converted to manual control and they were faster in racing than the wand equipped boats. I've got a lot of hours in a Rave but never got to sail the manual controlled version but I talked at length to one of the guys involved. The system uses two joysticks each one controlling one main foil. On the Rave, the foils develop all the righting moment so the joysticks not only control altitude but roll(righting moment) as well. You use your feet to steer....

Some say manual control is impossible in a Moth-I don't believe it-but it hasn't been successfully used in Moth racing as far as I know. David Lugg flew an I-14 using manual altitude control in 1999 as an experiment and, of course, the AC boats have the foil rake(altitude) controlled by the skipper.

 

 

Doug - go and watch the video I just shared. Pay attention to how busy the skipper is. Watch his sheet hand. watch the wand popping.now think, how fast can I twist a tiller grip, and steer, and sheet, and use my weight. Then ask, what happens when I throw in a gybe?

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People always come up with reasons why it won't work on a Moth-the main objection being the work load you mention. But I think about the Rave guys with manual control where they had to control altitude(independently on both sides simultaneously!) and roll and steer with their feet, adjust the rudder t-foil lever and sheet two or three sails! Not impossible, just difficult. Definitely faster if it could be mastered based on the Rave and AC experience.

 

 

Rave manual controls. Rudder t-foil lever is alongside the seat:

post-30-0-81032300-1479857029.jpg

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.

 

...^^....rather makes a difference that the sailor sits in a pod rather than hiking.

 

Apples and oranges. :wacko:

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I will resist commenting from here on out as someone who has the time to comment all day long versus sailing know much more than me.

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So how many of the classes mentioned in this thread actually have national or international racing fleets. That is at least one way to conclude whether they're good designs

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Gotta wonder why their promo vids are in protected waters, minimal wind. :wacko:

Southampton Water. See where is says "solent.ac.uk" in big letters on the hull? That august institution is in Southampton.

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Mr bgulari, It was you was it not in a recent video making enthusiastic comments about four point foiling on the Nacra 17 and how it was a great improvement over the curved board version of the boat? I was wondering if you might comment further in these pages, particularly what you think about that layout vs 3 point foiling as on the flying phantom or generally where you think robust multihull foiling should go. I think you will find an very receptive, and respectful, audience here for any insightful "nonsense" you might have.

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the question I have is, is it better to go over the speed humps or is it possible to go straight through them

 

In practice you don't have that choice do you?

 

The wand cannot tell the difference between a wave and a change in average ride height. Either way its going to react. The folks who've actually sailed the boats extensively tell us that having the wand ahead of the foil so that it tends to act in phase with the water tends to work better than having it behind where its going to be out of phase. Its easy to think of good reasons why this should be correct, and hard to think of good reasons why this should be wrong.

 

If you wanted to attempt to control ride height more independently of waves, well that would be quite challenging. Maybe you'd have to have multiple wands with differential input, one as far forward as possible, one aft, and maybe give one greater input than the other. It feels like a mechanical and maintenance nightmare to me, but who knows. Given a long enough boat then averaging out the inputs from different wands might have some advantages in controlling the ride height independently from the foils.

 

I suppose it might just be a tad less draggy not having the foil shape react to every little bump, but I have a ghost of a suspicion that foil orientation in respect to water flow within the wave form might be more important in that respect than what the actual water surface is doing.

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The wand cannot tell the difference between a wave and a change in average ride height. Either way its going to react. The folks who've actually sailed the boats extensively tell us that having the wand ahead of the foil so that it tends to act in phase with the water tends to work better than having it behind where its going to be out of phase. Its easy to think of good reasons why this should be correct, and hard to think of good reasons why this should be wrong.

The designers' assertion is that it reduces porpoising which, they say, is a typical beginner's problem in Moths. The tutor at Europe's main Mothing school is one of the design team & presumably knows what issues beginners have.

 

You may or may not buy into that argument and personally, I wouldn't know, but it isn't the case there is no rationale for the choice.

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the question I have is, is it better to go over the speed humps or is it possible to go straight through them

 

In practice you don't have that choice do you?

 

The wand cannot tell the difference between a wave and a change in average ride height. Either way its going to react. The folks who've actually sailed the boats extensively tell us that having the wand ahead of the foil so that it tends to act in phase with the water tends to work better than having it behind where its going to be out of phase. Its easy to think of good reasons why this should be correct, and hard to think of good reasons why this should be wrong.

 

If you wanted to attempt to control ride height more independently of waves, well that would be quite challenging. Maybe you'd have to have multiple wands with differential input, one as far forward as possible, one aft, and maybe give one greater input than the other. It feels like a mechanical and maintenance nightmare to me, but who knows. Given a long enough boat then averaging out the inputs from different wands might have some advantages in controlling the ride height independently from the foils.

 

I suppose it might just be a tad less draggy not having the foil shape react to every little bump, but I have a ghost of a suspicion that foil orientation in respect to water flow within the wave form might be more important in that respect than what the actual water surface is doing.

 

 

You do have a choice.

Looking at the moth videos, I'm sure that the choice of a long flexible wand and I suspect some type of damping component (either intrinsic to the mechanism or specifically added in) act to filter out higher frequency inputs from the waves. The issue is not whether the wand reacts, but how you use that reaction to control the control surfaces. In addition the way the control surface them affects the trim of the boat has some inevitable damping built in.

 

In any control system you can adjust things like the gain and damping of the system to make the mechanism act to filter unwanted inputs, its not always easy, but its generally possible.

 

I don't know what the best answer is, it certainly appears that among foilers there are different opinions on this, and I'm interested in the reasons and how those reason affect the design decisions.

 

The energy argument is more about the cost of lifting the whole structure up and down over every wave as opposed to maintaining height, (rather than the drag of the control surface). To me the idea of having the boat move up and down over every wave seems very inefficient, and does not appear to be how the boats in the video were reacting to the waves. The boats were rising and falling at a fairly low frequency compared to the rate they were encountering waves.

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A couple of practical questions from the viewpoint of someone who is interested and curious:

 

On the Chesapeake, we have many protected estuaries that on the face of things might seem ideal for foiling cats and tri's. However, they are often shallow and the humps move around a bit especially after hard winters with high, prolonged winds. During the summer, the waters are often in a near-constant state of churn from ski-doo's, ski boats and large power yachts.

 

1. What happens if you run aground? How catastrophic is the damage? How expensive are repair parts?

2. How do these boats deal with sloppy conditions vs. the clean glass in the photos and videos?

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the question I have is, is it better to go over the speed humps or is it possible to go straight through them

 

In practice you don't have that choice do you?

 

The wand cannot tell the difference between a wave and a change in average ride height. Either way its going to react. The folks who've actually sailed the boats extensively tell us that having the wand ahead of the foil so that it tends to act in phase with the water tends to work better than having it behind where its going to be out of phase. Its easy to think of good reasons why this should be correct, and hard to think of good reasons why this should be wrong.

 

 

 

 

Which folks? The folks that designed the F101 have tremendous experience in Moth sailing as well as great experience sailing with a trailing wand on the Whisper cat that they designed. Dr. Sam Bradfield was an American foiling pioneer and his midship wand system was used successfully on several boats and works extremely well-I've sailed his Rave a lot. In my opinion, there is not one group of "folks" that have the answer for every foiler that uses a wand. There are major advantages and disadvantages to both types of wand depending on the boat design.

And manual foil control is something that is being used on the AC boats where the skipper controls the AOI of the main foil and was also used on specially modified Raves and proven faster than wands in extensive racing.

Ignoring these people and these developments is really shortsighted.

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Mr bgulari, It was you was it not in a recent video making enthusiastic comments about four point foiling on the Nacra 17 and how it was a great improvement over the curved board version of the boat? I was wondering if you might comment further in these pages, particularly what you think about that layout vs 3 point foiling as on the flying phantom or generally where you think robust multihull foiling should go. I think you will find an very receptive, and respectful, audience here for any insightful "nonsense" you might have.

 

 

.......unlikely you'll get a peep with th'Lard around.

 

 

...some pretty credentialed sorts drop by, but hard to get a word in without being 'corrected' <_<

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Video originally posted by "Blaze720" in the DA thread---For the "crendentialed sorts" that just don't get it-midship wands work exceedingly well.

Same mainfoil/wand system as used on the F101:

 

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.

 

 

.....^^...so why no footage yet in 2' chop!? :mellow:

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What I don't understand is why White got involved in this? Doesn't in reduce the Whisper's chance of getting established ?

 

And what are the pros and cons of each ?

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Some background, the designer of the Whisper is the same guy as the Foiling 101. He designed the Whisper with the wands behind working with his own design theory and thoughts. Let's just say the jury is very much out on whether it really works. There a quite a few very good mothies who are not buying it. Hes now developed the 101.

People seem too feel it makes foiling easy but it's not fast.

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Heres a good video of the F101. Of course, it has the wand in the wrong place which explains how well it is flying! Maybe they could stick a bowsprit on the bow for luck?!

https://www.youtube.com/watch?v=UU7ROtmSfUA

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In that vid the slow reacting heavily damped action reveals that on an average Nor Easter on Sydney harbour, with ebb tide, it would spend a lot of time slow hitting waves or flipping a over t!

 

Thanks for that! Just what this place needs-more "expert" opinion........ (based on nonsense)

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...it seems its best to think of the wand has handling average height above water in all cases, and also pitch when placed away from the center of pitch rotation, with the separation affecting sensitivity. I.e. long way forward gives a big reaction to a pitch change, near the center of rotation gives little or no reaction....

 

The pitch attitude of the boat is the sum of the angle of attack of the foil and the flight path angle of the foil through the water. The slower dynamics of the boat play out at almost a constant angle of attack, and changes in the pitch attitude of the boat reflect changes to the flight path angle. If you multiply the flight path angle by the velocity, you get the rate of change of the flying height. So the pitch attitude times the speed also corresponds to the rate of change of the height.

 

Putting the wand ahead of the foil means the feedback signal is a combination of both height and the rate of change in height. This adds lead to the control system and improves the damping. If you consider that, at constant speed a change in angle of attack is needed to change the flight path angle, then pitch attitude feedback adds even more lead because it anticipates the change in the flight path angle as well as the flight path angle's effect on height.

 

If you make a feedback system that has only position feedback (like pure height measurement), what you create is an oscillator. The feedback will make the system correct back toward the set point, and the feedback goes to zero at the set point, but the trajectory is already passing through the set point and headed toward the opposite extreme. As error accumulates in the opposite direction, the system will reverse and correct back, but it will overshoot again in the original direction.

 

When you add rate feedback, the reaction of the control system is stronger when it is headed away from the set point, and the feedback goes to zero before it gets back to the set point. The control system will already be applying control to slow things down as it gets to the set point, so any overshoot the other way is less than for the pure position feedback design. This makes the response settle down and converge to the set value. If you have enough rate feedback, there won't be any overshoot at all and the system will be heavily damped.

 

That's why putting the wand forward helps to make the boat easier to sail. It's not so much that it anticipates the waves, but more that it anticipates what the boat will do, even in flat water. Sure, you can put the wand at the foil and get damping from other sources. But moving the wand forward is a powerful way to add damping, and pitch attitude feedback is especially effective when the boat is going fast.

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Thanks, Tom-that is the best explanation I have yet read of the benefits of a forward wand.

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Thanks, Tom-that is the best explanation I have yet read of the benefits of a forward wand.

For such a foil wanker as you this should be old news and no come as a surprise - it is also very simple logic for a control system

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"no come as a surprise", man.......

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Some background, the designer of the Whisper is the same guy as the Foiling 101. He designed the Whisper with the wands behind working with his own design theory and thoughts. Let's just say the jury is very much out on whether it really works. There a quite a few very good mothies who are not buying it. Hes now developed the 101.

People seem too feel it makes foiling easy but it's not fast.

 

I enjoy following along with the new tech.

 

Why does everyone insist that new foilers have to match or exceed moth speed?

 

Theres thousands of different boats out there, and not every design is made to be faster than current tech. Ease of use is certainly a huge factor in anything we do; it sure holds value in beginner foilers.

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Some background, the designer of the Whisper is the same guy as the Foiling 101. He designed the Whisper with the wands behind working with his own design theory and thoughts. Let's just say the jury is very much out on whether it really works. There a quite a few very good mothies who are not buying it. Hes now developed the 101.

People seem too feel it makes foiling easy but it's not fast.

 

I enjoy following along with the new tech.

 

Why does everyone insist that new foilers have to match or exceed moth speed?

 

Theres thousands of different boats out there, and not every design is made to be faster than current tech. Ease of use is certainly a huge factor in anything we do; it sure holds value in beginner foilers.

 

 

 

There's nothing particularly "new tech" about this boat, though it is innovative.

 

The comparison with a Moth is in regard to the wand position, not speed. The reason that a Moth is used for comparison is that it's an active development class that generally only does things that are proven to be "better" than alternatives. It's a well sorted wand controlled foiler, so whatever the top boats are doing is likely to be better than alternatives. A Moth can put the wand anywhere from 0.5m off the bow to 0.5m off the transom. The current trend is to put it as far forward as it can go within the class rules, it wouldn't be that way if there weren't advantages.

 

People can theorise about why it's better that other positions, but the fact that it is "better", at least for Moths, is fairly well established (though I think the benefits of using a bowsprit are overstated, at least for us "mid–fleeters"). From my experience, a forward mounted wand is better because:

  1. It causes the boat to start reacting to waves before the wand reaches where the wand is, so helping to overcoming inertia and
  2. You can easily see what the wand is doing and steer to keep it roughly in contact with the water surface (or above it)

There is a caveat on #1: the boat response is attenuated by inertia, so going to windward in most conditions the boat goes through waves so fast that it doesn't have time to react to individual waves, so doesn't go up and down over waves much until they get quite big (say over 1m). Very different downwind, where the boat overtakes the waves more slowly so does have time to respond. This is where sailor skill is involved to sail the boat without causing either the foil to leave the front of a wave and crash, or drive the hull into the back of a wave and crash (though somewhat more slowly).

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This is what the F101 guys say about their wand:

 

WHY IS THE WAND ON THE TRAILING EDGE OF THE MAIN FOIL?

The F101 has its control wand fixed to the back of the trailing edge of the main foil, as opposed to the mounted at the bow which is where Moth’s mount the foil. There are a number of advantages to the trailing edge position, the most important of which is that the wand measures the ride height of the boat irrespective of pitch. This important factor can help to eliminate the porpoise effect which many beginners experience when learning to sail a Moth.

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This is what the F101 guys say about their wand:

 

WHY IS THE WAND ON THE TRAILING EDGE OF THE MAIN FOIL?

The F101 has its control wand fixed to the back of the trailing edge of the main foil, as opposed to the mounted at the bow which is where Moths mount the foil. There are a number of advantages to the trailing edge position, the most important of which is that the wand measures the ride height of the boat irrespective of pitch. This important factor can help to eliminate the porpoise effect which many beginners experience when learning to sail a Moth.

I like the F101 a lot

 

I think the above is spin

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Midship wand(s) on a Moth:

 

pix by Thierry Martinez-

 

rati8o.jpg

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By the way the picture above is of Jean Pierre Ziegart-from an 8 year old thread: ...... "the midship [wand] has been adopted experimentally by Jean Pierre Ziegart who sailed to a 14th out of 36 boats in the Velocitec Speed Challenge and to 31st out of about 95 boats at the UK Moth Worlds."

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An absolutely terrific comment by Basiliscus in answer to a question by "robg" in the Foiler Stability and Control thread in multihulls:

 

You're right that the pitch attitude is referenced to the horizontal. But the trajectory of a foiler, like an airplane, has a third dimension.
The force on the foil depends on the angle of attack, which is referenced to the velocity vector, not the horizontal. If the velocity vector is horizontal, then the pitch attitude and angle of attack are the same (when the boat is sailed with level heel). But if the velocity vector is pointed up or down, then for the same angle of attack the pitch attitude will also be more up or down.
Another example is a boat that maintains the same pitch attitude, but loses speed. The angle of attack has to increase to maintain the same lift (lift = weight at near steady-state conditions). The boat starts to sink down, resulting in the velocity vector pointing downward and the angle of attack increases because of the change in the velocity vector instead of a change in the pitch attitude.
You can get a similar effect with the controls. Say you used the stern foil to maintain pitch attitude and you made a step increase in the main foil flap deflection. The increase in lift from the flap will accelerate the boat upwards, and very quickly the new trajectory will reduce the angle of attack and bring the lift back into equilibrium as the boat continues to rise at a steady rate. In all these cases, vertical direction of the velocity vector (flight path angle) summed with the angle of attack (angle between the velocity vector and the reference line) equals the pitch attitude (angle between the reference line and the horizontal).
What the sailor wants is for the trajectory to be level. The lift on the foil depends on both the flap and the angle of attack, and the boat has to find the combination of flap angle and pitch attitude that brings the lift into equilibrium with a level trajectory. The pitch attitude and the flying height don't respond at the same time to the flap control. A designer has the option of exploiting the phase difference between pitch and heave at the expense of more complexity in the control system, due to having to link a forward mounted wand to the flap on the foil.
Or the designer can opt for a mechanically simpler arrangement that doesn't try to feed back pitch attitude to the flap. In that case, maybe the designer adds area to the stern foil to increase the pitch stability and damping. The wetted area will be higher, increasing the drag, but for a one-design the simplicity may be worth the tradeoff. There's no single way, or even one best way, to design the control system because the requirements for each boat are different. That's why design is an art.

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To the foil tech heads here. I'm getting interested but I can't find much in the way of resources online on the theory, design, rules of thumb etc.. Any pointers to online resources would be gratefully received.

 

I was looking at the R class boats here in New Zealand (Lyttelton) on Saturday and it got me thinking about the design of the foils.. One question of I have about the T type foils that the R class is using along with the Moths is why the horizontal section doesn't have end plates (winglets whatever you call them). I see some of them sweep back and come to a point something like a dolphins tail does this get help eliminate vortex generation at the tips?

 

This may be the wrong place and is resurrecting an old thread but this was the first decent foiling thread that I found :)

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To the foil tech heads here. I'm getting interested but I can't find much in the way of resources online on the theory, design, rules of thumb etc.. Any pointers to online resources would be gratefully received.

 

 

Until there is a price point for the mass public sailing..............................it is all moot.

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To the foil tech heads here. I'm getting interested but I can't find much in the way of resources online on the theory, design, rules of thumb etc.. Any pointers to online resources would be gratefully received.

 

Until there is a price point for the mass public sailing..............................it is all moot.

 

http://www.fulcrumspeedworks.com/UFO/

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To the foil tech heads here. I'm getting interested but I can't find much in the way of resources online on the theory, design, rules of thumb etc.. Any pointers to online resources would be gratefully received.

 

I was looking at the R class boats here in New Zealand (Lyttelton) on Saturday and it got me thinking about the design of the foils.. One question of I have about the T type foils that the R class is using along with the Moths is why the horizontal section doesn't have end plates (winglets whatever you call them). I see some of them sweep back and come to a point something like a dolphins tail does this get help eliminate vortex generation at the tips?

 

This may be the wrong place and is resurrecting an old thread but this was the first decent foiling thread that I found :)

 

The best book on the market right now that I know of is "Hydrofoils Design Build Fly" by Ray Vellinga. It has a great deal on theory written in a clear and understandable format. There is a lot on small power foilers but there is even a section on Moths. I think it's available through Amazon and or Peacock Hill Publishing ,Gig Harbor, Washington.

You could also join the International Hydrofoil Society-membership is open for free now.

If you need further help PM or e-mail me and I'll try to point you in the right direction.

 

http://www.foils.org/

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Dear god it's like foiling herpes.... don't scratch it, it'll come back worse than before.

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To the foil tech heads here. I'm getting interested but I can't find much in the way of resources online on the theory, design, rules of thumb etc.. Any pointers to online resources would be gratefully received.

 

 

Until there is a price point for the mass public sailing..............................it is all moot.

 

Hmmm with a bit (or a lot ) of DIY it's not expensive to cock around with so the price point is what you make it guess.

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Thanks everybody. Off to do some scratching... going to work on a ride ;) And meanwhile do some reading..... My other half has gone and got herself a job on the beach for 2 years I have to find something to do!

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