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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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What the bow wand does and a midship wand can not do is CONTROL pitch when its really needed.

 

The prime exampe is when waves get big enough that the foils will ventilate unless the boat sails up and over the crests and down and through the troughs. The boat has to pitch bow down over the crests and pitch bow up again in the troughs, otherwise the hull just crashes into the crests and the foils come out of the water in the troughs.

 

The wand on the bow gets just that bit of anticipation, it passes the crest and flicks forward before the foil reaches the crest, applies up flap, kills lift and pitches the boat bow down. Conversly the wand reaches the base of the trough just ahead of the foil, gets pushed back, applies down flap, which lifts the front of the boat, pitches it upward so it can climb up the nest wave.

 

The few moths who have tried midship wands find that none of this happens, simply put the middle of the boat is already too high by the time the flap moves and any pitch down is way too late to avoid ventilation over the crest. And the bow tends to touch down in the trough before the wand starts to apply flap lift.

 

On moths the forward wand works very well in big waves with wave crest several boat lengths apart.

 

It does not work so well when the waves are only one or two boat lenghts apart because the frequency of responses is very fast and also because this size waves can tend to be more random, so deeper or steeper waves pop up which no wand system can cope with. Good moth sailors have developped extra boat handling techniques in these conditions but its still very challenging as seen in all the fun crash videos from various moth regattas.

 

In smooth water it does not seem to matter where the wand is.

 

Thanks for filling in a gap in my knowledge of this. The short time between wand and foil reaching the wave is not the thing to focus on then, but the extra distance which the foil travels through the water with the foil adjusted by the wand rising earlier, and even in a short distance it will lift the middle of a moth and thereby change its pitch significantly (winglets on the rudder holding the back down longer) before it reaches the wave. Clearly this functionality is more important than worrying about what does on flat water if you fail to keep the boat flat.

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Doug

 

A few stills from a video that everybody on here who has watched it but you says doesn't show consistent stable flight does not prove a single thing. If you think those pictures prove anything, then you have to accept that the nose dive picture plus the one showing the boat leaping out are just as valid.

 

You consistently prove in what you write that you have no idea at all about sailing light, high performance foilers. You try to learn everything second hand off the net and it leads you to poor conclusions. We established this back in Moth days and you continue your BS today with foiling cats. The only benefit you bring is that because you constantly post rubbish, we do get people who know what they are talking about post useful corrections, which you attack because if it isn't Lord's Law when it comes to foiling, it has to be wrong. Most on here seem intelligent enough to be able to tell who posts sense and who doesn't. Complete uninformed nonsense!

 

Simon, you don't know what you're talking about. The "few stills" and July 24th,2014 video are conclusive proof that the boat foiled and it did it, for the first time ever, in a 5mph(4.34knot) wind. Further, ALL the stills are valid:

1) The (partial)pitchpole occurred on the second day of testing in wind when the boat was overpowered and I tried to gybe. The next instant in that sequence shows the boat recovering and sailing away!

--

2) The "Take Off!" still was explained in post 195 on the previous page,

--

3) The other stills show the boat foiling extremely well for the first time in very light air(5mph/4.34 knots) and in waves "bigger" than the wind(from a 20 mile fetch thru a nearby bridge leftover from the previous night).

Testing clearly shows the progression of the boat to full foiling from the problems encountered at the beginning-the last video is 100% proof that the foil system worked perfectly-regardless of any uninformed attempt to say otherwise. But testing is not done yet even though we reached a major milestone with the boat foiling in a 5 mph wind while using two different altitude control systems simultaneously. Hopefully, starting in June or July we'll get a lot more video and in stronger wind. But July 24th, 2014 was a major accomplishment for the boat after a great deal of development-and we will build on that this year.

=======
So the stills are a record of testing and development concluding with a brand new radical trimaran design foiling in very light air-can't get much better than that for the very first time on foils!

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What the bow wand does and a midship wand can not do is CONTROL pitch when its really needed.

 

The prime exampe is when waves get big enough that the foils will ventilate unless the boat sails up and over the crests and down and through the troughs. The boat has to pitch bow down over the crests and pitch bow up again in the troughs, otherwise the hull just crashes into the crests and the foils come out of the water in the troughs.

 

The wand on the bow gets just that bit of anticipation, it passes the crest and flicks forward before the foil reaches the crest, applies up flap, kills lift and pitches the boat bow down. Conversly the wand reaches the base of the trough just ahead of the foil, gets pushed back, applies down flap, which lifts the front of the boat, pitches it upward so it can climb up the nest wave.

 

The few moths who have tried midship wands find that none of this happens, simply put the middle of the boat is already too high by the time the flap moves and any pitch down is way too late to avoid ventilation over the crest. And the bow tends to touch down in the trough before the wand starts to apply flap lift.

 

On moths the forward wand works very well in big waves with wave crest several boat lengths apart.

 

It does not work so well when the waves are only one or two boat lenghts apart because the frequency of responses is very fast and also because this size waves can tend to be more random, so deeper or steeper waves pop up which no wand system can cope with. Good moth sailors have developped extra boat handling techniques in these conditions but its still very challenging as seen in all the fun crash videos from various moth regattas.

 

In smooth water it does not seem to matter where the wand is.

 

Thanks for filling in a gap in my knowledge of this. The short time between wand and foil reaching the wave is not the thing to focus on then, but the extra distance which the foil travels through the water with the foil adjusted by the wand rising earlier, and even in a short distance it will lift the middle of a moth and thereby change its pitch significantly (winglets on the rudder holding the back down longer) before it reaches the wave. Clearly this functionality is more important than worrying about what does on flat water if you fail to keep the boat flat.

 

 

David, some of the best innovators in wand controlled multihulls swear by midship wands as opposed to wands way out in front. One thing about the Moth that has to be repeated: compared to the distance forward on the Vampire,as a proportion of boat length, the Moth wand is significantly closer to the foil than are the wands on the Vampire. The greater the distance the greater the chance of pitch coupling.

Look at the videos of Moths at the last worlds-every one of them is published on boatdesign.net under "Moth on Foils!"

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Doug

 

If you stopped trying to tell us what is going on via your video analysis and instead listened to people who actually sail the boats, you might just get somewhere. How many times do people with proven track records have to tell you things before you believe them rather than your own poor video analysis.

 

You have steadfastly refused to explain why those who have tried midship wands on Moth have found them to be significantly worse than bow mounted ones. We have even seen it with identical boats and foils. You must think all Moth sailors are stupid, ignoring a development that would make their boats better. And we are not talking about half arsed home designers. Many of the most successful Moth sailors of the foiling era are with AC teams, both as sailors and designers. Are you really telling me that those guys are so stupid or stubborn that they are deliberately burying their heads in the sand over this issue.

 

It is just like you telling world champions, on this very forum, that they didn't understand how their boats worked or even how they sailed them. You told Bora, then world champ and an aerospace engineer that he didn't understand how Moths foil, you told John Harris when he was world champion that he was mistaken about the best way to sail a Moth and you told Scott Babbage that he was wrong when he described what he was doing in a photo (yes, I know he hasn't won the worlds but he is probably the most consistent top sailor there is). All 3 stopped posting at different points because of your bullshit. You even said that Rohan Veal was lying about how much he weighed, no doubt because it totally screwed up the long list of (meaningless) calculations you used to plague us with. But my all time favorite was when you insisted everybody else was incorrect when you stated that the most famous British handicap race wasn't a handicap race at all and used one sentence from a report on the event to justify your claim. You have always maintained the view that you are right and everybody else is wrong. Well, I am sorry but I believe world champions and professional foil designers over anything you say, every time.

 

And just for the record, this isn't so much of an attack on you as a statement of facts. Every single thing I have posted above is true and correct.

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Figured I'd throw a question out to you guys...

 

Is there a database ala NACA foil sections for the various foils being (successfully) used out there? Or are these all one off propriety designs?

 

The reason I ask is that I have the CNC and CAD ability to make them but not the engineering know how to design them.

 

Cheers

 

Mark

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Can we stop this futile argument about nonsense and go back to discussion foils?

+ 10

 

Sorry, Phil, but there is no point as long as Doug posts shit. When you have somebody posting that everything everybody else says is wrong and keeps doing it, there are only 2 options. You either stop posting or you correct the errors. In this thread alone, Doug has said you are wrong and I am wrong about matters we both know are correct. I also find his attitude arrogant and disrespectful particularly towards people who deserve respect (and I am not talking about me!) We always have far better foiling discussions when Doug doesn't get involved.

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I'm kinda sorry too.

 

Unfortunately, I am the sort of person who cannot stand by when they see anti social behaviour - whether that be on a train, bus or in the street.
Even when I know it will lead to trouble - I will call them out.

999 times out of a thousand the person will stop straight away and revert to normal and acceptable ways.
We all have that inner voice of reason - just some people will choose to ignore it and blunder on even when called out......

I therefore will call out douchE baggerY when I read it.

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Doug

 

If you stopped trying to tell us what is going on via your video analysis and instead listened to people who actually sail the boats, you might just get somewhere. How many times do people with proven track records have to tell you things before you believe them rather than your own poor video analysis.

 

You have steadfastly refused to explain why those who have tried midship wands on Moth have found them to be significantly worse than bow mounted ones. We have even seen it with identical boats and foils. You must think all Moth sailors are stupid, ignoring a development that would make their boats better. And we are not talking about half arsed home designers. Many of the most successful Moth sailors of the foiling era are with AC teams, both as sailors and designers. Are you really telling me that those guys are so stupid or stubborn that they are deliberately burying their heads in the sand over this issue.

 

It is just like you telling world champions, on this very forum, that they didn't understand how their boats worked or even how they sailed them. You told Bora, then world champ and an aerospace engineer that he didn't understand how Moths foil, you told John Harris when he was world champion that he was mistaken about the best way to sail a Moth and you told Scott Babbage that he was wrong when he described what he was doing in a photo (yes, I know he hasn't won the worlds but he is probably the most consistent top sailor there is). All 3 stopped posting at different points because of your bullshit. You even said that Rohan Veal was lying about how much he weighed, no doubt because it totally screwed up the long list of (meaningless) calculations you used to plague us with. But my all time favorite was when you insisted everybody else was incorrect when you stated that the most famous British handicap race wasn't a handicap race at all and used one sentence from a report on the event to justify your claim. You have always maintained the view that you are right and everybody else is wrong. Well, I am sorry but I believe world champions and professional foil designers over anything you say, every time.

 

And just for the record, this isn't so much of an attack on you as a statement of facts. Every single thing I have posted above is true and correct.

 

Simon, all I have said in the last few days about the Moth is that the wand is much closer to the main foil than it is on the Vampire and therefore much less susceptible to pitch coupling. But you read that as an attack on the Moth and Moth sailors which it is not in any way. You attempt to corrupt the meaning of what I say or do to fit your own agenda. You're a bullshit artist Simon-and don't have a clue what you're talking about in regards to my boat or multihull wands-something I know a lot about whether you like it or not.

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what is the mental problem that you guys have with the ignore button? It works so damned good now, takes about 6 seconds, and makes this conversations more cogent, if not a bit shorter.

 

Stop complaining, and ignore Simon if you don't want to see the same three paragraph response to Doug that you've read forty thousand times. Ignore Doug if you don't want to read the same yapping from a guy who doesn't know how to design and doesn't know how to sail. Ignore both if you want a very short thread.

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what is the mental problem that you guys have with the ignore button? It works so damned good now, takes about 6 seconds, and makes this conversations more cogent, if not a bit shorter.

 

Stop complaining, and ignore Simon if you don't want to see the same three paragraph response to Doug that you've read forty thousand times. Ignore Doug if you don't want to read the same yapping from a guy who doesn't know how to design and doesn't know how to sail. Ignore both if you want a very short thread.

 

+10,000

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A bit more on surface piercing T-foils. I was inspired a few years ago by design work done by Mal(au) on the concept of a surface piercing T-foil for a Laser(see pix below). I also designed a combination surface piercing and "normal" foil that worked well with manual flap control in combination with the surface piercing elements when tested on a 16' hull.

Since I got into trying to help build a radio controlled AC cat, I've given a lot of thought to how to design a very simple foil system that would make it easier to get more RC boats in the air.

The idea for the Batfoils actually came from a foil I conceived of that could eliminate the main wand controlled foil on the Fire Arrow. It is basically a refined version of Mal's original idea combined with an iFlap(see earlier) on each tip to allow virtually automatic performance throughout the speed range starting at very low speed.

After talking with Alan Smith about canted T-foils I became convinced that some of the drawbacks with T-foils could be remedied by canting them. That was particularly true with the Batfoils, where a 4 degree angle of heel of the whole boat allows the windward main foil to fly saving on the electronics and weight of a retractable system on a model. These foils are about to be tested on the D4Z cat and ,though very,very experimental I think they have a good chance of working. They may have applications on some fullsize boats as well as on models, as a simple flying system, IF they work:

Surface Piercing T-Foils

------------------------------------

For the application of a surface piercing T-foil on the main hull of a trimaran to replace a wand controlled foil it is essential that the foil be capable of downforce with no manual intervention by the crew and no wand. So the idea,that may be tested later this year, is for a curved twisted "batfoil" with a center upside down asymmetrical section with the center downforce section separated from the rest of the foil by fences. Theoretically, it may be possible that as the boat speeds up and pitches down slightly that the asymmetrical section could develop downforce automatically. If so, it would allow the wand controlled foil on the Test Model to be replaced with a completely automatic foil with no moving parts.

I'd be interested in hearing almost anybody's comments on these foils ,particularly the one in the left illustration below. The generic surface piercing T-foil has applications on RC catamarans(with a 10 degree cant) and may have other applications as well. The surface piercing foil with downforce may be limited to the main hull of any size trimaran.

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post-30-0-43138700-1434818917_thumb.jpg

post-30-0-60358700-1434818929_thumb.jpg

post-30-0-14471400-1434818973_thumb.jpg

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Has anyone tried a rudder with an adjustable angle on the winglets for pitch control, thereby separating this from altitude control? That would let the wand deal with altitude alone (the wand could be placed near the foil) while the helmsman could adjust pitch by such means as twisting the tiller. Alternatively, the wand could be left far forward and the winglet angle would only be adjusted as a way of correcting when the pitch is wrong or to change the pitch earlier than the wand would if conditions require that.

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Almost every current foiler has an adjustable angle of incidence(AOI) on the rudder foil(s) by moving the whole rudder or an adjustable flap. Frequency of use varies a lot on multihull foilers and some multihull foilers don't have this adjustment available while sailing. The AC 72 rule prohibited using any rudder AOI adjustment during racing but the new rule allow it.

My test model does not require adjustable AOI on the rudder.

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What a completely uninformed comment!!! No adjustable rudder foil would have prevented this or even had a slight effect on it. This was caused by too much wind for the amount of sail while trying to gybe off the foils(skipper mistake). The boat recovered instantly and sailed on.

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What a completely uninformed comment!!! No adjustable rudder foil would have prevented this or even had a slight effect on it. This was caused by too much wind for the amount of sail while trying to gybe off the foils(skipper mistake). The boat recovered instantly and sailed on.

dlpaliar.png

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Has anyone tried a rudder with an adjustable angle on the winglets for pitch control, thereby separating this from altitude control? That would let the wand deal with altitude alone (the wand could be placed near the foil) while the helmsman could adjust pitch by such means as twisting the tiller. Alternatively, the wand could be left far forward and the winglet angle would only be adjusted as a way of correcting when the pitch is wrong or to change the pitch earlier than the wand would if conditions require that.

This is how many foilers work. Most of the monohull foilers have "on the go": adjustable rudder winglets, usually through twisting the tiller. on cats, some have adjustment on the go while others use "set and forget". The rudder winglets are used to trim out the main foils to keep them within a working range and in the case of wand control, so the main foil is always within a range that the wand can work. It gets complex with teh Moth as you can adjust everything, with multiple adjustments on the wand, its connection and gearing plus the rudder winglets.

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So that sensible discussion is due to start when exactly?

 

Before that gets taken out of context ..that was a general comment not related to the previous post... Just looking for interesting posts on actual design theory on real boats (not models) as without a proper foil shape all the rest is just BS IMHO

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Has anyone tried a rudder with an adjustable angle on the winglets for pitch control, thereby separating this from altitude control? That would let the wand deal with altitude alone (the wand could be placed near the foil) while the helmsman could adjust pitch by such means as twisting the tiller. Alternatively, the wand could be left far forward and the winglet angle would only be adjusted as a way of correcting when the pitch is wrong or to change the pitch earlier than the wand would if conditions require that.

This is how many foilers work. Most of the monohull foilers have "on the go": adjustable rudder winglets, usually through twisting the tiller. on cats, some have adjustment on the go while others use "set and forget". The rudder winglets are used to trim out the main foils to keep them within a working range and in the case of wand control, so the main foil is always within a range that the wand can work. It gets complex with teh Moth as you can adjust everything, with multiple adjustments on the wand, its connection and gearing plus the rudder winglets.

 

 

Right, so even with that control on the rudders it's still advantageous to have the wand a good way ahead of the foil as it partly or largely automates the pitch adjustments and saves you from doing unnecessary extra work at the helm. That is likely to apply to a multihull too, and the winglet angle control can I presume be used to help prevent the pitch of the boat going wildly wrong if you can anticipate a rotation in time, and enabling you to fly it flat more of the time so that the wand is setting the foil to the right angle. It'll be interesting to see if Doug takes that on board from now on, but he's helped me learn by attracting corrections from the rest of you which have expanded my knowledge, so, whatever people think of him, he has his uses.

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Has anyone tried a rudder with an adjustable angle on the winglets for pitch control, thereby separating this from altitude control? That would let the wand deal with altitude alone (the wand could be placed near the foil) while the helmsman could adjust pitch by such means as twisting the tiller. Alternatively, the wand could be left far forward and the winglet angle would only be adjusted as a way of correcting when the pitch is wrong or to change the pitch earlier than the wand would if conditions require that.

This is how many foilers work. Most of the monohull foilers have "on the go": adjustable rudder winglets, usually through twisting the tiller. on cats, some have adjustment on the go while others use "set and forget". The rudder winglets are used to trim out the main foils to keep them within a working range and in the case of wand control, so the main foil is always within a range that the wand can work. It gets complex with teh Moth as you can adjust everything, with multiple adjustments on the wand, its connection and gearing plus the rudder winglets.

 

 

Right, so even with that control on the rudders it's still advantageous to have the wand a good way ahead of the foil as it partly or largely automates the pitch adjustments and saves you from doing unnecessary extra work at the helm. That is likely to apply to a multihull too, and the winglet angle control can I presume be used to help prevent the pitch of the boat going wildly wrong if you can anticipate a rotation in time, and enabling you to fly it flat more of the time so that the wand is setting the foil to the right angle. It'll be interesting to see if Doug takes that on board from now on, but he's helped me learn by attracting corrections from the rest of you which have expanded my knowledge, so, whatever people think of him, he has his uses.

 

 

Wrong! Did you watch the video's I suggested? "Corrections"=uninformed speculation except from Phil S who is undoubtedly right in regards to the Moth-but not about wand controlled multihulls. Bradfield pioneered wands almost 30 years ago, the Whisper guys are among the best out there-don't discount what these guys have done on the basis of uninformed BS on the internet.

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Doug

 

Yet again, so wrong. Just because people have made foiling work without "on the fly" adjustment to the rudder winglets doesn't mean that things wouldn't be better with it. If you forget what type of foiling for a moment (active or passive), the AC guys say that it is always better to have the winglets adjustable than not. And it's not just them. And it is that clear cut. Sorry you don't seem to be in the loop but even you should be able to pick that up just by reading between the lines of almost everything that is written on the subject by those guys.

 

The reason why it is so much better is because as conditions change - wind strength, waves and boat speed, the optimum range for the AoA of the main foil changes. If you have to allow for all of that just through the flap and wand, you need significantly more range which means a bigger flap (slow) and, because wand movement is limited to the same amount, the flap moves more for any given input (again slow). So, simply put, the better you control the overall AoA of the main foil, the less you need to move the flap and the smaller the flap needs to be. In each case, that is faster. It does make the boat less "automatic", but overall, it makes for a better foiling experience in a wider range of conditions.

 

You keep going on about Bradfield's boats, but can you show us how Osprey performed in waves. The other boats had enough weight to act as a dampener but with lightweight boats, forces come into play you don't otherwise see and I have never seen any footage or photos or written reports about how that boat performs in anything other than flat water.

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Depending on the use of the boat and the design a controlled rudder foil is simply not necessary. Most Raves did not have one but later it was an option. My F3 15 years ago started out with one but it proved totally unnecessary. It is unnecessary on the Fire Arrow Test Model and would likely be on the fullsize sport boat version. I'm not positive but I don't think the Whisper, Phantom, Nacra 20FCS or Vampire have rudder foils adjustable while foiling. Most wand controlled boats don't need to do more than make minor changes to the rudder AOI very infrequently. A boat with UptiP foils(depending on the design) is entirely different than a wand controlled foiler and it is probably best to have a controllable rudder foil-at least on bigger boats-changing from an upwind to downwind setting ,for instance. Constant active adjustment probably doesn't do much good on any multifoiler. Under the new AC rule, though, the total max adjustment is 3 degrees if I remember correctly.

Part of the reason why frequent adjustment is unnecessary is that most foilers have trailing rudder foils that, at maximum, carry about 20% of the load at takeoff and much less as the boat speeds up and pitches down to the point that at a certain speed the rudder foil develops downforce automatically. You need to know what that transition speed is before you mess with the rudder AOI on a foiler going fast.

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You cannot keep using the fact that some boats don't use adjustable rudder winglets as evidence that it is the best way to go. For instance, I know of an AC team that has fitted adjustment to one of their Flying Phantoms and it made a significant difference. Then you hear comments made somebody from another team, Chris Draper, who said after sailing the GS32 that it would be better if it has adjustment to the rudder wings.

 

And it doesn't really matter whether you are using active or passive foils when it comes to how effective it is to change the rudder wing AoA. The issues it helps to tackle are many, not least the differences in speed from uphill to downwind. Speeds can more than double. As the speed increases, so does the amount of lift (obvious) which means you fly higher and have less range for the wand to work. There are a number of ways of trimming this out and adjustable rudder wings is one. In addition, when everything is set up right, you can use the rudder adjustment to trim the boat fore and aft - in every case I know of, boats foil faster if they are trimmed bow down, which I believe is all about aerodynamic improvements.

 

And finally,there is a good reason why the AC have allowed rudder wings to be played and that is because it makes for better foiling.

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On the moth the rudder foil angle of attack is frequently used but not many people try to use it for each wave crest/trough, basically they come through too quickly for your wrist or the foil to react in time.

 

It is adjsuted for light wind take offs. If take off is marginal it pays to add lift to the rudder and in some cases move slightly aft, to add to the total lift and share it between both foils.

 

It is also adjusted beween upwind and downwind sailing, or fast and slow speeds.

 

At upwind speeds of 11 to 16 kts there is benefit is having slight lift on the rudder so that the boat sits very level in pitch trim and minimises the windage of the wings. This can put the main foil nominally at a low AoA so that the foil needs slightly increased flap deflection to carry the weight of the boat and crew. This deflection makes the foil section higher camber than in neutral, and provides an effective foil AOA greater than at neutral setting, both of these provide the opportunity to heal the boat to windard and use the extra available lifft to suck the boat up to windward.

 

At the windward mark its common to wind the tiller and reduce the ift on the rudder. Boat speed goes up to 22 to 28. This does a few things, it raised the bow so that the boat better handles the bow down pitch from the bear away, it increases the AOA of the main foil whichmeans at the extra speed the flap does not need to be deflected as much, so the main foil flies with less flap which reduces the camber of the section and reduces the drag coefficient of teh section. If this is all you do the boat wikl fly out, becasue the wand has to go lower to reduce the flap deflection, so its common to also reduce the wand length and/or shorten the deck pushrod to bring up the flap with the wand still backand keep the boat low enough for the waves. Add in the vang and cunningham and it gets a bit busy at the rounding marks.

 

All these have to be changed back again at the bottom mark, I like to pull the cunningham in first as it makes the round up from about 24kts a bit easier to manage, the others can wait until you have rounded, slowed down and got your breath back.

 

So foiling is a lot more than choosing what letter of the alphabet you like, or even what planform, section or area you choose in the design office.

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Phil, as usual, you eloquently describe in a non adversarial manner the "whole" picture - this style of sailing is so much more than elevated sailing and the subtle nuances have large consequences.

 

The management of any performance boat 49er, 14ft skiff are hectic at their mark rounding. Make it singlehanded and foiling and the intensity increases again.

The main issue is that at windy and choppy venues there are still only a small number who have the mastery of the Moth. Same can be said of A's who are not yet as developed in their learning curve.

 

Yet the fact that we can see what appears effortless from off the boat - is for those involved anything but.......

 

Which is why sweeping statements of 100% stability and success raise the reactions that are seen here.

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On the moth the rudder foil angle of attack is frequently used but not many people try to use it for each wave crest/trough, basically they come through too quickly for your wrist or the foil to react in time.

 

It is adjsuted for light wind take offs. If take off is marginal it pays to add lift to the rudder and in some cases move slightly aft, to add to the total lift and share it between both foils.

 

It is also adjusted beween upwind and downwind sailing, or fast and slow speeds.

 

At upwind speeds of 11 to 16 kts there is benefit is having slight lift on the rudder so that the boat sits very level in pitch trim and minimises the windage of the wings. This can put the main foil nominally at a low AoA so that the foil needs slightly increased flap deflection to carry the weight of the boat and crew. This deflection makes the foil section higher camber than in neutral, and provides an effective foil AOA greater than at neutral setting, both of these provide the opportunity to heal the boat to windard and use the extra available lifft to suck the boat up to windward.

 

At the windward mark its common to wind the tiller and reduce the ift on the rudder. Boat speed goes up to 22 to 28. This does a few things, it raised the bow so that the boat better handles the bow down pitch from the bear away, it increases the AOA of the main foil whichmeans at the extra speed the flap does not need to be deflected as much, so the main foil flies with less flap which reduces the camber of the section and reduces the drag coefficient of teh section. If this is all you do the boat wikl fly out, becasue the wand has to go lower to reduce the flap deflection, so its common to also reduce the wand length and/or shorten the deck pushrod to bring up the flap with the wand still backand keep the boat low enough for the waves. Add in the vang and cunningham and it gets a bit busy at the rounding marks.

 

All these have to be changed back again at the bottom mark, I like to pull the cunningham in first as it makes the round up from about 24kts a bit easier to manage, the others can wait until you have rounded, slowed down and got your breath back.

 

So foiling is a lot more than choosing what letter of the alphabet you like, or even what planform, section or area you choose in the design office.

 

Thanks, Phil-great explanation for the Moth.......

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On the moth the rudder foil angle of attack is frequently used but not many people try to use it for each wave crest/trough, basically they come through too quickly for your wrist or the foil to react in time.

 

It is adjsuted for light wind take offs. If take off is marginal it pays to add lift to the rudder and in some cases move slightly aft, to add to the total lift and share it between both foils.

 

It is also adjusted beween upwind and downwind sailing, or fast and slow speeds.

 

At upwind speeds of 11 to 16 kts there is benefit is having slight lift on the rudder so that the boat sits very level in pitch trim and minimises the windage of the wings. This can put the main foil nominally at a low AoA so that the foil needs slightly increased flap deflection to carry the weight of the boat and crew. This deflection makes the foil section higher camber than in neutral, and provides an effective foil AOA greater than at neutral setting, both of these provide the opportunity to heal the boat to windard and use the extra available lifft to suck the boat up to windward.

 

At the windward mark its common to wind the tiller and reduce the ift on the rudder. Boat speed goes up to 22 to 28. This does a few things, it raised the bow so that the boat better handles the bow down pitch from the bear away, it increases the AOA of the main foil whichmeans at the extra speed the flap does not need to be deflected as much, so the main foil flies with less flap which reduces the camber of the section and reduces the drag coefficient of teh section. If this is all you do the boat wikl fly out, becasue the wand has to go lower to reduce the flap deflection, so its common to also reduce the wand length and/or shorten the deck pushrod to bring up the flap with the wand still backand keep the boat low enough for the waves. Add in the vang and cunningham and it gets a bit busy at the rounding marks.

 

All these have to be changed back again at the bottom mark, I like to pull the cunningham in first as it makes the round up from about 24kts a bit easier to manage, the others can wait until you have rounded, slowed down and got your breath back.

 

So foiling is a lot more than choosing what letter of the alphabet you like, or even what planform, section or area you choose in the design office.

I'm not sure what you describe in term of boat pitch is the fastest on a moth.

 

I'm not an expert,but both from my (small) moth experience and both from what I remember from Amac speech at the last foiling week, as soon as the boat is at 15knots, the fastest way is always to have flap close to neutral. And that normally means flat or slightly bow-up upwind and definitely bow-down downwind in the breeze.

 

I think that This bow down mode for the breezy downwinds is also the reason why sone top guys on mach2 run pretty small AOA now and also why the new mach2 rudder vertical is so much longer than the previous one

 

Edit: re-reading again your post, only thing I don't really lagree in the end is that upwind, foils are less draggy if they have more camber. Of course,as you said, going a bit bow-up increases aero drag,so I'm not really sure of where the fast point is

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Has anyone tried a rudder with an adjustable angle on the winglets for pitch control, thereby separating this from altitude control? That would let the wand deal with altitude alone (the wand could be placed near the foil) while the helmsman could adjust pitch by such means as twisting the tiller. Alternatively, the wand could be left far forward and the winglet angle would only be adjusted as a way of correcting when the pitch is wrong or to change the pitch earlier than the wand would if conditions require that.

This is how many foilers work. Most of the monohull foilers have "on the go": adjustable rudder winglets, usually through twisting the tiller. on cats, some have adjustment on the go while others use "set and forget". The rudder winglets are used to trim out the main foils to keep them within a working range and in the case of wand control, so the main foil is always within a range that the wand can work. It gets complex with teh Moth as you can adjust everything, with multiple adjustments on the wand, its connection and gearing plus the rudder winglets.

 

 

Right, so even with that control on the rudders it's still advantageous to have the wand a good way ahead of the foil as it partly or largely automates the pitch adjustments and saves you from doing unnecessary extra work at the helm. That is likely to apply to a multihull too, and the winglet angle control can I presume be used to help prevent the pitch of the boat going wildly wrong if you can anticipate a rotation in time, and enabling you to fly it flat more of the time so that the wand is setting the foil to the right angle. It'll be interesting to see if Doug takes that on board from now on, but he's helped me learn by attracting corrections from the rest of you which have expanded my knowledge, so, whatever people think of him, he has his uses.

 

 

Wrong! Did you watch the video's I suggested? "Corrections"=uninformed speculation except from Phil S who is undoubtedly right in regards to the Moth-but not about wand controlled multihulls. Bradfield pioneered wands almost 30 years ago, the Whisper guys are among the best out there-don't discount what these guys have done on the basis of uninformed BS on the internet.

 

 

Well Doug, the Vampire draws a lot from the Moth, including the forward wand position which they may hope will provide the same functionality. If the flap is adjusted a couple of yards sooner, the pitch of the foil (due to the pitch of the boat) will be different not just after those two yards (where the difference may be tiny), but over many yards that follow, leading to a significant difference in the total extra lift generated through that time. It's hard to see why that shouldn't apply to all the wand-controlled multihulls. Were any experiments done on the Osprey to try out other wand positions or was it always kept where it was due to the way it was connected to foils that had to be possible to raise? Have any experiments been done on the Whisper, or are they too tied to their unique way of putting the whole wand below the hull? With the Moth, the experiment has been done, so we're getting real knowledge from there based on hard-won experience. Are you providing real knowledge or just guesses when you say "undoubtedly right in regards to the Moth-but not about wand controlled multihulls"?

 

Thanks again to Phil and Simon for the insights into winglet adjustments and how they're actually used.

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17mika, not everone uses the same techniques. I have talked a lot with the fast people in my area but not a lot to the many others around the world and I am sure everyone has their own preferred settings. The variety is what makes it all interesting, challenging and so damned hard to master.

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The moth crowd put a lot of effort into eliminating slop in the linkage system. Any slop certainly delays the reaction and even in smooth water the boat will hunt or pump up and down, but it tends not to induce pitching.

 

Once the relaitve AoA between the main foil and the rudder foil are close to optimum, the boat flies very level, and this is what is needed almost all of the time. The exceptions are the cases I described in earlier posts, climbing up onto the foils, and climbing up and down very big/long waves.

 

When you see pictures of boats with the bow in the air like cat on the previous page, or the promo photo of Rohan from about 10 years ago, it can only be because something has gone very wrong, or because they are doing it intentionally to make a good photo. When you see photos of moths with the bow digging in its usually because a moment earlier the boat was too high and the main foil ventilated and lost all lift, most often because of adverse waves.

 

Basically pitching is not an issue one the boat is set up correctly.

 

One occasion when the wand has most difficulty is the rare occasion when you get waves overtaking the boat. This tends to be a wake from a large fast motorboat, and the problem mostly occurs when going upwind, when the wave speed has a chance of being faster than the moth. In this case the wave troght gets to the foil before the wand and the reaction of the sytem gets out of phase with what is needed. Plenty of splashdowns occur and some people choose to tack away and avoid the mess up. It does however endorse the use of the forward wand.

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Did you watch the videos yet?

Have you actually sailed a modern foiler yet/ever???

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Yes Simon, the point is just put him on the Ignore list and get on with life.

 

 

Can we stop this futile argument about nonsense and go back to discussion foils?

+ 10

 

Sorry, Phil, but there is no point as long as Doug posts shit. When you have somebody posting that everything everybody else says is wrong and keeps doing it, there are only 2 options. You either stop posting or you correct the errors. In this thread alone, Doug has said you are wrong and I am wrong about matters we both know are correct. I also find his attitude arrogant and disrespectful particularly towards people who deserve respect (and I am not talking about me!) We always have far better foiling discussions when Doug doesn't get involved.

 

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You don't seem to understand that at any speed over 10 knots a wave that moves a wand that is forward as on the Vampire will have long since passed the foil when the foil moves. And pitching of the boat can cause wand/foil flap movement which interferes with the altitude control function of the wand. When pitch coupling happens to coincide with normal wand movement extreme flap movement can result that is completely unrelated to altitude control.

Did you watch the videos yet?

Doug

 

I think it is time for you to start rethinking your ideas on wands.forget for one moment your mantra above and consider facts, It is a fact that on lightweight performance foilers, having the wand ahead of the foil is faster, so much so that some latest Moths are even placing the wand as far forward as it can go. Because people have tried mid wands and all sorts of set ups, we have a pretty good idea of what works best.

 

The other thing that needs to be factored into any theory on wands is an acceptance that Phil and others are right when they say that the videos of it all going wrong show pilot error, not "system" error. If you are watching videos looking for system errors and have no experience of sailing the boats, you might well make the mistake if blaming unusual attitude issues to system problems, when it is not.

 

I think that people who haven't sailed these high performance, lightweight foiler (both mono and multi) really do under estimate just how much fairly small inputs from the sailor can have a very big affect on the overall attitude of the boat. Phil does a great job of trying to explain it, but even then, there is so much that comes as second nature that it gets missed out - a slight ease of the sheet or a small movement of bodyweight at the right time can be the difference between success and failure. I do feel that some of it is a case of if you leave it until the boat reacts, you are too late. Knowing how the boat will react and then spotting the conditions is as important as anything.

 

So to dismiss forward mounted wands based on some idea of how fast the boat is moving compared with the waves seems to me to miss the whole point and ignores too many basic truths.

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You don't seem to understand that at any speed over 10 knots a wave that moves a wand that is forward as on the Vampire will have long since passed the foil when the foil moves. And pitching of the boat can cause wand/foil flap movement which interferes with the altitude control function of the wand. When pitch coupling happens to coincide with normal wand movement extreme flap movement can result that is completely unrelated to altitude control.

Did you watch the videos yet?

Doug

 

I think it is time for you to start rethinking your ideas on wands.forget for one moment your mantra above and consider facts, It is a fact that on lightweight performance foilers, having the wand ahead of the foil is faster, so much so that some latest Moths are even placing the wand as far forward as it can go. Because people have tried mid wands and all sorts of set ups, we have a pretty good idea of what works best.

 

The other thing that needs to be factored into any theory on wands is an acceptance that Phil and others are right when they say that the videos of it all going wrong show pilot error, not "system" error. If you are watching videos looking for system errors and have no experience of sailing the boats, you might well make the mistake if blaming unusual attitude issues to system problems, when it is not.

 

I think that people who haven't sailed these high performance, lightweight foiler (both mono and multi) really do under estimate just how much fairly small inputs from the sailor can have a very big affect on the overall attitude of the boat. Phil does a great job of trying to explain it, but even then, there is so much that comes as second nature that it gets missed out - a slight ease of the sheet or a small movement of bodyweight at the right time can be the difference between success and failure. I do feel that some of it is a case of if you leave it until the boat reacts, you are too late. Knowing how the boat will react and then spotting the conditions is as important as anything.

 

So to dismiss forward mounted wands based on some idea of how fast the boat is moving compared with the waves seems to me to miss the whole point and ignores too many basic truths.

 

 

You mean like the Whisper(midship aft wands)??!! One of the lightest two person foilers being produced. Basic Truth #1: you're wrong, Simon.

 

post-30-0-33145400-1434989322_thumb.jpg

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Doug

 

Please stop and read what I said. How can you use an example of what is a one off boat as evidence of what is faster. I have never said that mid wands don't work, so stop posting examples like that. What I said is that it has been proven time and again that boats with forward wands out perform those with mid wands, all other things being equal. That is why the Moth guys use it. The examples you keep providing do not compare like for like. You can only use them if you can say they have been sailed with mid wands and forward wands, which is a comparison the Moth guys have made and, I believe,a few others as well.

 

For you to be able to say that I am wrong you need comparative evidence, which you fail to give.

 

Mid wands like the Whisper is very seductive because it gets rid of the biggest problem with wands - the mechanism and making sure there is no play in the system.

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You don't seem to understand that at any speed over 10 knots a wave that moves a wand that is forward as on the Vampire will have long since passed the foil when the foil moves. And pitching of the boat can cause wand/foil flap movement which interferes with the altitude control function of the wand. When pitch coupling happens to coincide with normal wand movement extreme flap movement can result that is completely unrelated to altitude control.

Did you watch the videos yet?

 

I don't know which videos you think prove your point, but anything you're trying to read from videos of Moths which contradicts what Moth sailors actually say would indicate that you're reading them wrong - they've done the testing that you haven't (and which you are not in a position to do). As for the Whisper videos, they show it sailing in beautiful, flat water. The difference in performance may not show up too well in videos either, unless you're watching two identical boats setting out to compare different wand positions in waves and seeing one of them pull ahead time and time again. Have you got links to any like that for Moths or any cat? Have you got accounts from the people who designed and sailed a decent foiling cat who describe how they've tried wands next to and far ahead of the foil and they've determined that the former is better? Your reasoned argument doesn't carry any weight because it contradicts the findings of Moth sailors, so it can't be trusted to hold for foiling cats either. This looks like something that needs to be settled by careful experiments rather than by simplistic arguments, and if the experiments haven't been done properly it's too soon to declare a winner. (The Vampire looks best placed to try out such experiments, but it would still involve a lot of potentially unnecessary work and is unlikely to be a priority for them.)

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Discussion of wand for racing boats is still totally irrelevant to anything except moths (and maybe CCats) until RRS52 gets changed at ISAF or in event SIs or fleet Class rules. Up till now there seems to be no desire to change this situation, particularly in ACats ot the AC. None of the new wand controlled cats seem to be selling enough boats to make a new class with its own rules and if the beach cat regatta circuit gets serious they will not be able to race there either. So its all sort of accademic.

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The moth crowd put a lot of effort into eliminating slop in the linkage system. Any slop certainly delays the reaction and even in smooth water the boat will hunt or pump up and down, but it tends not to induce pitching.

 

Once the relaitve AoA between the main foil and the rudder foil are close to optimum, the boat flies very level, and this is what is needed almost all of the time. The exceptions are the cases I described in earlier posts, climbing up onto the foils, and climbing up and down very big/long waves.

 

When you see pictures of boats with the bow in the air like cat on the previous page, or the promo photo of Rohan from about 10 years ago, it can only be because something has gone very wrong, or because they are doing it intentionally to make a good photo. When you see photos of moths with the bow digging in its usually because a moment earlier the boat was too high and the main foil ventilated and lost all lift, most often because of adverse waves.

 

Basically pitching is not an issue one the boat is set up correctly.

 

One occasion when the wand has most difficulty is the rare occasion when you get waves overtaking the boat. This tends to be a wake from a large fast motorboat, and the problem mostly occurs when going upwind, when the wave speed has a chance of being faster than the moth. In this case the wave troght gets to the foil before the wand and the reaction of the sytem gets out of phase with what is needed. Plenty of splashdowns occur and some people choose to tack away and avoid the mess up. It does however endorse the use of the forward wand.

 

Discussion of wand for racing boats is still totally irrelevant to anything except moths (and maybe CCats) until RRS52 gets changed at ISAF or in event SIs or fleet Class rules. Up till now there seems to be no desire to change this situation, particularly in ACats ot the AC. None of the new wand controlled cats seem to be selling enough boats to make a new class with its own rules and if the beach cat regatta circuit gets serious they will not be able to race there either. So its all sort of accademic.

It's an interesting point, Phil. I have been trying to find something in the NOR and SI of the Round Texel because there was at least one wand boat sailing but I could find nothing about RRS52. And I think this will be pattern - I expect most events to ignore it so it will be interesting to see if we get protests from competitors and if we do, how it will be handled. Maybe it is time for ISAF to specifically address this and make an exception for wands,

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I have been trying to find something in the NOR and SI of the Round Texel because there was at least one wand boat sailing but I could find nothing about RRS52.

 

Isn't that a matter for class rules rather than SIs?

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I have been trying to find something in the NOR and SI of the Round Texel because there was at least one wand boat sailing but I could find nothing about RRS52.

 

Isn't that a matter for class rules rather than SIs?

 

Not if the event is open to boats of any, or no particular class, like the Texel.

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I have been trying to find something in the NOR and SI of the Round Texel because there was at least one wand boat sailing but I could find nothing about RRS52.

 

Isn't that a matter for class rules rather than SIs?

 

Not if the event is open to boats of any, or no particular class, like the Texel.

 

I looked in the NOR and SI"s for a number of the classic British handicap/pursuit races such as the Bloody Mary (reputed to be the largest dinghy race in the world) and it seems that none of them mention RRS52. The NOR specifically states that the event is sailed under the RRS unless modified. Theory suggests that other competitors could protest the Moths.

 

I think that it is a far bigger issue in individual classes. For instance, while I am sure that A Class sailors would be happy to sail in events where Moths are racing even without any changes to RRS52, if anybody tried to compete with a wand system in an A, there would be a pretty swift protest on a number of grounds of which RRS52 is but one.

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I would have expected the classic UK pursuit races with yardstick handicaps would require boats to comply with their own individual class rules for which their yardstick was allocated. If this was the case then only moths could use wands.

This might also apply in the Texel but there are no existing cat classes which allow wands. (maybe CCat by precident not text)

In either case one offs or individual boats without a class association and set of class rules would be breaking RRS52.

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Discussion of wand for racing boats is still totally irrelevant to anything except moths (and maybe CCats) until RRS52 gets changed at ISAF or in event SIs or fleet Class rules. Up till now there seems to be no desire to change this situation, particularly in ACats ot the AC. None of the new wand controlled cats seem to be selling enough boats to make a new class with its own rules and if the beach cat regatta circuit gets serious they will not be able to race there either. So its all sort of accademic.

 

It isn't the wands that appeal to me, but the idea of canting T foils with adjustable flaps for minimum drag on all points of sail. On a two-man boat I can imagine the crew controlling something that duplicates the functionality of a wand while watching where the wand would normally be and looking ahead to anticipate where it would be likely to go next, but I don't know if it's actually possible for a human to act fast enough for this to work. In videos I see the wands jumping up and down like crazy on wavelets, but a person simulating a wand wouldn't need to bother making those little adjustments, so the task wouldn't be as frantic as it is for a real wand, but it may still need reactions faster than any human can achieve to keep the hulls off the water and the foils in, so the question I'm asking myself now is how close can a person get to the required reaction times?

 

Has this been tested properly to see what's required and what's humanly possible? I can imagine someone trying the experiment on a Moth and getting nowhere with it because he has too many other things to do at the same time, so it needs to be done on a boat where the person trying to control the altitude is free to do nothing but that. It takes a long time to learn to ride a unicycle, but some people can do it if they put in the time, so what could easily be written off as an impossible skill after even a long time of testing it may in the end turn out to be possible after all. Also, if you put sensors in place to measure water speed and pressure around the foil (and air speed and pressure around the sail), it may be possible to run the data through a computer and provide a display which the crew can unthinkingly follow to adjust the flap so that he isn't caught out by subtle changes which indicate that a wild change in lift requirements is about to occur but which are hard for a human to read directly. Would that be breaking a rule?

 

Another possibility is a compromise between active and passive control such that passive controls (involving extra drag) correct for extreme movements (e.g. an extra foil higher up, which only comes into play if the hull dips too low) while active controls (avoiding extra drag) put the rest under human control (with the human only having to guard against sudden movements upwards without having to worry about sudden downward movement - occasional mistakes could be less costly than the continual extra drag required by 100% passive control solutions).

 

The point of all this is that if it turns out that it is humanly possible to control altitude using T-foils without wands, and if that results in better performance, then that may become the standard way things are done (except on single-handed boats), and that will require the crew to be locked into that task full time, making it a terrible chore which might put a lot of people off this kind of sailing and lead to a few dedicated freaks dominating while no one else can find a willing crew with sufficient skill. It may also reach the point where adding wands doesn't add significantly to performance, but merely makes sailing safer while bringing back the fun, and I would hope that if we get to that point the pressure to change the rule would force the change.

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Dave Lugg built a foiling i14 with a manually adjusted T foil back in 2001 (which was subsiquently banned). Having watched them train it wasn't a big success.

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My first 16' foiler had manual control of the main foil flap that worked fairly well on a boat that ,as a whole, was a bit of a disappointment. Two guys modified two different Rave 16' foilers with manual control of the two main foils and did well against other wand controlled Raves in racing. Manual control can work, depending on the boat. See PDF below-

 

Picture of David Luggs I-14 under manual control:

Rave-Hand-Controls-for-Rave.pdf

post-30-0-57021200-1435103108_thumb.jpg

post-30-0-07722600-1435104004_thumb.jpg

post-30-0-57736400-1435104050.jpg

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My first 16' foiler had manual control of the main foil flap that worked fairly well on a boat that ,as a whole, was a bit of a disappointment.

 

 

This bit of comedy just keeps popping up in your histrionic lexicon, Doug; That your Aerothud actually foiled.

 

It did not foil, you don't have a single bit of verifiable proof that it did and yet.... you continue to spew your own brand of mythology on the topic as if a moronic chant can somehow bring it back to life as a functional boat.

 

This whole episode has gotten so greasy that it now has passed through the veil of dorkiness and on into the realm of pure asininity. At some point, a fake story you can't support should be gracefully retired from the daily babble so that you, yourself, can move on to other fallacious meandering. You know, sort of "freshen up" the old girl a bit for public viewing.

.

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My first 16' foiler had manual control of the main foil flap that worked fairly well......

Mr. Lord

 

Do you have any pictures of "your" manual control system??? NO!!!

 

Do you have any pictures of your boat actually foiling??? NO!!!

 

You are nothing but a fraud.......a pathalogical liar and a fraud. You have been caught in your lies, yet you continue to lie. You have ZERO credibility!!!!

 

You claimed that you could not afford another rig for your FirEarrOw, yet you somehow built an entire second boat......more lies!!!

 

You haven't sailed your Lawn Ornament in a year. You have repeatedly been asked why, and have refused to answer, by ignoring the question entirely.

 

Yes, you are a LIAR and a FRAUD!!!

 

***R.T.***

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David,

I think the Hydros CCat team had the crew continually controlling main foil incidence. They did very well with it most of the time, with not a lot of practice. Flap control would have to be easier with lighter loads. These seemingly impossible things seem to get conquered by some determination.

Having the manual controlled flaps on sloping mainfoils would potentially give some extra height control. I have suggested to a few ACat people it might be worth a try, but if Rule 8 gets dumped the development will go in a new direction.

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Yes, as far as I understoood, the Hydros C-Cat crew were ajusting "real-time" their main foil's AoA and less frequently, the"canting".

Their lifting surface was quite short for a 21cm chord section and almost perfect L @ 90°.

 

Hydros' had incredible boost of speed but a lack of stability.

It's probably very difficult to keep concentration for this kind of real time adjustment

As a result, the helm had the tiller + wing main control line

I don't know who was adjusting the sail camber & twist when the boat speed was changing a lot.

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I tried moth sailing without wand control a few times.

Firstly in the very early days when we tried to do it with no wand at all and more recently and more commonly when some linkage or wand has broken. Even though we have had easilly adjustable rudder foil AOA available its very hard in anything except very flat water to maintain height between the very small safe height limits. Its really stressful as you know a big splash is only a blink away. Its also possible to foil upwind without some pressure pushing the flap down although height can be more easilly managed by feathering to control speed variations.

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Luggs boat had a canard configuration where the rudder foil was significantly larger than the daggerboard foil so he was able to control flight with the rudder foil adjustment, On a "normal" configuration where the main foil is larger and carries most of the load, its next to impossible to control flight with just the rudder foil. On my boat the twist grips on the extension tiller controlled the main foil flap which was a relatively docile arrangement that worked.

On the Rave the mainfoil flaps on each side were controlled manually. That means the skipper controlled altitude and righting moment.

 

aeroSKIFF main foil with partial span flap(and rudder with extension tiller and twist grips) and the main foil flap twist grip handle:

post-30-0-54173400-1435147036_thumb.jpg

post-30-0-86644400-1435147062_thumb.jpg

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So it can be done for a bit and is almost practical, but really needs some assistance, such as some way of combining active controls with passive.

Thinking down the purely passive foil path though, it occurs to me that the FP and similar designs already have reasonable downwind speed and the thing that's really putting me off them is their poor upwind performance. If you have a passive V foil which generates upward lift on average, that's a draggy equivalent of a vertical T-foil. It's also the angle that uptip foils are generally used at. If you raise them you are effectively canting them a bit due to the curved main part of the board, so you should be able to generate a bit of lift to windward, unless when they're in the V position they're generating lift to leeward due to the uptip part of the foil generating more lift than the curved side - I don't know how balanced the two sides are in that regard. Does anyone have figures on the percentages of lift generated by these two parts?

 

Unfortunately, a canted V foil won't perform automatic altitude adjustments as well as it does when not canted, so it isn't the same as canting a wand-controlled T-foil, and I'm guessing that that's part of the problem too. It occurs to me though that a V foil with separately adjustable flaps on its two sides could be used vertically and generate lift to windward by using a bit more flap on one side and less on the other, so it wouldn't need to cant. I would imagine that someone must have tried that long before now, so is it in use anywhere and how well does it perform?

 

Also, it would be intersting to know if anyone's stuck passive foils on a Moth to compare its performance with other Moths (it's bound to be slower due to the extra drag) and to see if it can foil well upwind (and at what angle). It would also be interesting to see a cutting-edge passive-foil Moth to get a better idea of how passive cats should be performing.

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Brett Burvill's surface piercing (passive) foil(s) on a Moth(ruled illegal) . A surface piercing T-foil like Mal drew below on a Laser might work but probably not as well as a wand (or manually) controlled T-foil. 10 degree canted surface piercing T-foils to be tested on the D4Z test model sooner or later :

post-30-0-58649800-1435190708_thumb.jpg

post-30-0-20261100-1435190999_thumb.jpg

post-30-0-02885800-1435191653_thumb.jpg

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Originally Posted by David Cooper :

 

So it can be done for a bit and is almost practical, but really needs some assistance, such as some way of combining active controls with passive.

 

Thinking down the purely passive foil path though, it occurs to me that the FP and similar designs already have reasonable downwind speed and the thing that's really putting me off them is their poor upwind performance. If you have a passive V foil which generates upward lift on average, that's a draggy equivalent of a vertical T-foil. It's also the angle that uptip foils are generally used at. If you raise them you are effectively canting them a bit due to the curved main part of the board, so you should be able to generate a bit of lift to windward, unless when they're in the V position they're generating lift to leeward due to the uptip part of the foil generating more lift than the curved side - I don't know how balanced the two sides are in that regard. Does anyone have figures on the percentages of lift generated by these two parts?

 

 

 

Unfortunately, a canted V foil won't perform automatic altitude adjustments as well as it does when not canted, so it isn't the same as canting a wand-controlled T-foil, and I'm guessing that that's part of the problem too. It occurs to me though that a V foil with separately adjustable flaps on its two sides could be used vertically and generate lift to windward by using a bit more flap on one side and less on the other, so it wouldn't need to cant. I would imagine that someone must have tried that long before now, so is it in use anywhere and how well does it perform?

 

Also, it would be intersting to know if anyone's stuck passive foils on a Moth to compare its performance with other Moths (it's bound to be slower due to the extra drag) and to see if it can foil well upwind (and at what angle). It would also be interesting to see a cutting-edge passive-foil Moth to get a better idea of how passive cats should be performing.

David : It seems like the current crop of small catamarans is your best chance for getting the comparisons of active & passive foils that you want. I'm not sure which ones, specifically, but as Doug Lord mentioned, it's not likely to happen in the Moth class under their current rules.

 

But when you say the FP has such poor upwind performance, what are you comparing it to? Compared to other comparable cats ? If so, I'd like to see some references & numbers. Compared to their downwind speed ? If so, that's not a fair comparison. All sailboats that I know of are slower close-hauled than they are on a beam reach or a broad reach. So, of course they won't foil as readily upwind. It's more complicated than that, of course, but the lower upwind speed is the 1st obstacle in the way of upwind foiling.

 

I would caution you against trying to make sweeping comparisons of different types of foils. Far more important than whether a certain foil is a T or a V or whatever, is what are its dimensions for the loads it's carrying (horizontal span for the vertical lift & vertical depth for the sideforce). And these things change with the conditions. A T & a V foil can be very close in drag in many instances. A V foil can have much smaller drag at high speeds, but it's often too small to be the best at very low speeds. A T foil can be better at lower speeds, but it will almost certainly be larger than it has to be at high speeds.

 

No one can tell you a general number for the percentages of lift generated by the parts of any foils. That depends on the sizes & shapes of the individual designs, the incidence angles & the speeds involved.

 

For a given span, a V-Foil is actually a very efficient shape. Contrary to what you might think, the 2 segments facing each other provide a favorable interference. Low pressure on the upper surface of each segment helps the other segment to lift more easily & significantly lowers the induced drag.

 

Canting the foils can have its advantages, but you make it sound like it's a necessity to getting the foils to provide sideforce. You speculate that uncanted V foils could be made to lift to windward using flaps on the 2 segments, but you seem to be forgetting that all these types of foils get plenty of sideforce automatically by virtue of their leeway angles.

 

Good luck in trying to figure out the best configurations for upwind foiling. It's an interesting problem that has already provided us with a few surprises & I'm sure we can look forward to many more.

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On the moth the lift distribution between the two foils depends almost totally upon where you sit. This is because the crew is 2 to 3 times the mass of the boat. This will not be the case with heavier boats but crew position has to have a lot to do with distribution.

 

Upwind and downwind in smooth water we generally sit well forward, level with or slightly aft of the forward foil, which is also close to the centre of gravity of the boat. In this position the main/forward foil has to be carrying almost all of the weight.

 

Downwind in waves we sit further aft, to unload the forward foil and give the wand and flap a better chance of controlling height, rather than carrying load. It also means the forward foil will use less flap to carry less weight, and hence have kess drag. Most rudder foils are still slightly cambered so letting them fly at slightly +ve lift is less drag than flying at zero lift

 

If you sit too far aft upwind you get an odd feel of lee helm in the helm. This takes some figuring out but my take is that with the 15-20deg windward heal and quite small rudder foils, some of the vertical lift comes from the rudder blade and since its aft of the bearings it gives the tiller a lee helm feeling. This does not happen when we move aft downwind because we do not sail with as much windward heal.

 

Upwind at the stated 15-20deg windward heal it is apparent that the centreboard is flying at zero AOA and hence at minimum drag. The track of the boat climbs upwind above its heading due to the side component of lift from the main foil. In smooth water and depending on the foil span the boat can be flown very high with negligible amounts of centreboard in the water, proving its doing very little for leeway control. Big light-wind foils, and everything in waves need to be flown deeper to prevent the leeward side tips ventilating near the surface. Rudders need to be deeper than the centreboard though to maintain directional control. Weed or small motor boat wakes can mess things up quickly.

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interested to note that the first race of the UK Moth nationals was sailed today in 10 knots of wind and a classic Solent Chop. Anybody who has sailed at Stokes Bay and seen the photos of the race (see Y&Y report) will know that it is a real test of whether your wand system is working. And the winner of the race has his wand 500mm out front. Considering the boat has only recently been launched and Dylan hasn't had anywhere near the practice time the others have had, it is clear that having the wand further forward than his main rivals isn't harming his speed.

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Phil:
I always appreciate hearing your voice of experience with the Moth. It's amazing how many subtle little things are going on with such a seemingly simple boat. I don't have your years of experience (just a few months & only a few dozen actual hours on the water), so I haven't made all the connections of what happens & when. Your posts have been very helpful to me.

 

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Originally Posted by Phil S :

If you sit too far aft upwind you get an odd feel of lee helm in the helm. This takes some figuring out but my take is that with the 15-20deg windward heal and quite small rudder foils, some of the vertical lift comes from the rudder blade and since its aft of the bearings it gives the tiller a lee helm feeling. This does not happen when we move aft downwind because we do not sail with as much windward heal.

Phil : I'm going to take a stab at another possible explanation of this.

 

Suppose you're sailing along in perfect balance, with no weather helm or lee helm. Even though this implies that the net side force on the aft T-foil is zero, the "horizontal" & "vertical" components of the T-foil will have non-zero side-forces on them (equal in magnitude, but opposite in direction). Because the pressure on a foil acts perpendicularly to its surface, the side force on the "aft horizontal" should equal its vertical lift force multiplied by the tangent of the heel angle.

 

Moving your weight aft results in an increase in the vertical lift carried by the "aft horizontal" , and thus a proportional increase in its sideforce. Without adjusting the rudder, this increase in sideforce pushes the stern to windward - i.e. gives your boat a lee helm.

 

Does this make any sense to you? I find it a little confusing to think about.

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interested to note that the first race of the UK Moth nationals was sailed today in 10 knots of wind and a classic Solent Chop. Anybody who has sailed at Stokes Bay and seen the photos of the race (see Y&Y report) will know that it is a real test of whether your wand system is working. And the winner of the race has his wand 500mm out front. Considering the boat has only recently been launched and Dylan hasn't had anywhere near the practice time the others have had, it is clear that having the wand further forward than his main rivals isn't harming his speed.

I noticed in the video that Rashly has a bow sprint now too.

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David : It seems like the current crop of small catamarans is your best chance for getting the comparisons of active & passive foils that you want. I'm not sure which ones, specifically, but as Doug Lord mentioned, it's not likely to happen in the Moth class under their current rules.

 

I just though it was possible someone might still be experimenting with passive foils on a Moth to try to develop the most efficient version of it that's within RRS52. The interesting thing that would come out of that would be to see the upwind performance, specifically how easily it foils upwind, how high it goes and how fast. Would it, for example, head off at 40 degrees to the wind and make better VMG than a non-foiling Moth, or would it go at 50-55 degrees and make no gain in VMG.

 

 

[i've just found there's a pointless limit to how many boxed quotes you can make in a post, so I'll have to use the " kind instead.]

 

 

"But when you say the FP has such poor upwind performance, what are you comparing it to? Compared to other comparable cats ? If so, I'd like to see some references & numbers. Compared to their downwind speed ? If so, that's not a fair comparison. All sailboats that I know of are slower close-hauled than they are on a beam reach or a broad reach. So, of course they won't foil as readily upwind. It's more complicated than that, of course, but the lower upwind speed is the 1st obstacle in the way of upwind foiling."

 

What I'm referring to specifically is the FP (and similar boats) going upwind at 55 degrees to the wind and making no gains over their non-foiling equivalents. That doesn't make them bad boats, but it leads me to think that there is likely to be a better foil solution which doesn't suffer from this relatively poor performance upwind while retaining the high downwind performance.

 

 

 

 

"I would caution you against trying to make sweeping comparisons of different types of foils. Far more important than whether a certain foil is a T or a V or whatever, is what are its dimensions for the loads it's carrying (horizontal span for the vertical lift & vertical depth for the sideforce). And these things change with the conditions. A T & a V foil can be very close in drag in many instances. A V foil can have much smaller drag at high speeds, but it's often too small to be the best at very low speeds. A T foil can be better at lower speeds, but it will almost certainly be larger than it has to be at high speeds."

 

With a V foil and the two sides at 90 degrees to each other, each providing equal lift, that lift is working in two different directions which leads to a total lift upwards equivalent to a straight, horizontal foil spanning the same width. Much of the lift is therefore cancelled out, and the drag will be 1.4 times that of the horizontal foil. However, there will be complications as the area between the two sides may be reduced in pressure to a much greater extent (as you say), and the horizontal foil needs a vertical piece to hold it in place which will also generate drag (though less than if it was also generating lift), so the difference in drag may not be anything like as great. There is also the drag through the air of the rest of the boat which has to be factored in, so the difference in total drag may be trivial.

 

On the Moth though, the flap allows the horizontal foil to be shorter such that it can still provide a lot of lift but also reduce the drag dramatically at high speed. (I should point out that I'm not trying to teach anyone anything here as you all know it fine already - I'm just trying to set it out in such a way as to clarify it for myself and to attract corrections from people who know a lot more than I do). The FP doesn't have adjustable flaps in what may be serving as a V foil, so it is restricted to changing the pitch of the whole foil. Maybe the drag reduction in doing that is just as great though and I'm misunderstanding the value of a flap - the flap may only be there to provide easier active control from the wand, so that's a gap in my knowledge which needs filling.

 

 

 

"No one can tell you a general number for the percentages of lift generated by the parts of any foils. That depends on the sizes & shapes of the individual designs, the incidence angles & the speeds involved."

 

My guess is that more of the lift comes from the uptip part, and if that's the case it may result in the foil as a whole generating lift to leeward while sailing upwind, directly harming performance, so I'm trying to establish whether that's actaully what's happening. There's a huge difference in angle to the wind between these foiling cats and Moths, and I want to understand what's causing it.

 

 

 

"For a given span, a V-Foil is actually a very efficient shape. Contrary to what you might think, the 2 segments facing each other provide a favorable interference. Low pressure on the upper surface of each segment helps the other segment to lift more easily & significantly lowers the induced drag."

 

That's good, and there's no wand drag to factor in either, so what I'd like to establish is whether a V-foil with adjustable flaps could provide just about as good performance as a canting T-foil controlled by a wand.

 

 

 

"Canting the foils can have its advantages, but you make it sound like it's a necessity to getting the foils to provide sideforce. You speculate that uncanted V foils could be made to lift to windward using flaps on the 2 segments, but you seem to be forgetting that all these types of foils get plenty of sideforce automatically by virtue of their leeway angles."

 

I'm taking the importance of the canting aspect from the way that Moths use their foil when going to windward, but I don't know how important it actually is for that - some of the upward lift is actually generated from the sail being tilted towards the wind, but then a more vertical sail would generate more power to put through a foil generating more lift, so that aspect may cancel out. A number of people have suggested that lift to windward from the foil is important for generating the Moth's upwind performance, and that's doubtless why they've gone to the trouble of putting canting T-foils on the Vampire. Sailing a Moth vertically might provide concrete answers as to whether that makes it harder to get up on the foil and what sort of angle to the wind can be achieved, but the way the Moth has to be sailed to be competitive already tells us that there is a gain coming from some aspect of this tilt, and the most likely candidate is the lift to windward. If anyone knows anything about the Vampire's upwind performance, that would be well worth sharing.

 

 

 

"Good luck in trying to figure out the best configurations for upwind foiling. It's an interesting problem that has already provided us with a few surprises & I'm sure we can look forward to many more."

 

I'm a late arrival to this, so everything I'm thinking about has probably already been tested, if not on full size boats, then on models (by people like Doug) and in computer simulations, unless everyone's so tied up in designing things to fit in with existing rules for different classes that they've missed something significant. What I'm imagining right now is a V foil under each hull of a cat with a flap on just one side of each foil, used specifically for generating lift to windward. A vertical section would connect the V to the outside of the hull and allow the windward foil to be raised, and the whole thing could be removed sideways for launching and landing without damaging it. An additional Tornado-style foil could be housed in the hull for use in displacement mode.

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Originally Posted by David Cooper:

With a V foil and the two sides at 90 degrees to each other, each providing equal lift, that lift is working in two different directions which leads to a total lift upwards equivalent to a straight, horizontal foil spanning the same width. Much of the lift is therefore cancelled out, and the drag will be 1.4 times that of the horizontal foil.

David : What you wrote sounds perfectly plausible, but is actually not true. I'm attaching a graph from the classic book Fluid-Dynamic Drag by S. Hoerner. The bottom curve shows the results for wings with span held constant, showing an increasingly significant favorable effect as the dihedral angle increases. The parameter plotted is essentially 1/e, where e is the commonly used induced drag efficiency factor.

 

It's a little hard to read the scale, but for a 45deg wing, the plotted value is about 0.85 or 0.90, rather than the value of 1.4 that your reasoning produced. In other words, there is not a 40% increase in drag, but rather a 10% to15% reduction. For 60deg (which is the angle on my trimaran's foils), the reduction is even larger (>25%.).

 

These results are for wings in free air, but I have done calculations in a Vortex-Lattice code both in free air & with the water's surface accounted for. In free air, for 60deg, my calculated factor is about 0.78, which is similar to what's shown on the curve. When the free-surface effect is accounted for, the factor increases, typically to around 1.12, so its drag is somewhat higher than ideal (but nothing like 40% more).

 

So,really, V-Foils are much better than they get credit for!

post-21863-0-31201400-1435272859_thumb.jpg

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Originally Posted by David Cooper:

With a V foil and the two sides at 90 degrees to each other, each providing equal lift, that lift is working in two different directions which leads to a total lift upwards equivalent to a straight, horizontal foil spanning the same width. Much of the lift is therefore cancelled out, and the drag will be 1.4 times that of the horizontal foil.

David : What you wrote sounds perfectly plausible, but is actually not true. I'm attaching a graph from the classic book Fluid-Dynamic Drag by S. Hoerner. The bottom curve shows the results for wings with span held constant, showing an increasingly significant favorable effect as the dihedral angle increases. The parameter plotted is essentially 1/e, where e is the commonly used induced drag efficiency factor.

 

It's a little hard to read the scale, but for a 45deg wing, the plotted value is about 0.85 or 0.90, rather than the value of 1.4 that your reasoning produced. In other words, there is not a 40% increase in drag, but rather a 10% to15% reduction. For 60deg (which is the angle on my trimaran's foils), the reduction is even larger (>25%.).

 

These results are for wings in free air, but I have done calculations in a Vortex-Lattice code both in free air & with the water's surface accounted for. In free air, for 60deg, my calculated factor is about 0.78, which is similar to what's shown on the curve. When the free-surface effect is accounted for, the factor increases, typically to around 1.12, so its drag is somewhat higher than ideal (but nothing like 40% more).

 

So,really, V-Foils are much better than they get credit for!

 

A pretty darn cool boat for sure:

https://vimeo.com/34164014

Are you still playing with Broomstick?

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Doug H,

The graph only shows induced drag, but total drag incudes surface drag. Your argument that the induced drag drops with more dihedral applies only if procected span is constant, and to achieve that the total length and area of the foils has to increase.

 

For a V of 90deg, or 45deg dihedral in the digaram, the induced drag as you state is reduced by 10 -15% but the total area is increased by the 40% argued by David, so surface drag goes up as he says.

 

The proportion of induced and surface drag is very sependant on aspect ratio. Short spans have more induced drag, longer spans have less indiced drag. ACat foils must have lots of induced drag. Moth foils would have a lot less.

 

I like the old video of your Tri, Lots of performance with very large dihedral. I can not work out what is casuing your mini crashes. Your tacks are like a lot of my moth tacks, must be the grey beard we have in common.

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Doug H,

 

enjoyed your video, any particular reason you don't have any fences on those foils ?

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A Cat with Dario Valenza's uptip foils and the story behind it: http://www.catsailingnews.com/2015/06/q-with-bob-fischer-retrofitting-1998.html#more Apparently this address became unavailable-go to www.catsailingnews.com if it works.

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The article is interesting for a number of reasons. First, all credit to the guy for doing the conversion.

 

It should be noted that although the article tries to perpetuate the myth that removing rule 8 makes it possible to convert older boats, it actually confirms that the work done is exactly the same as you do to convert a boat to comply with rule 8. It is therefore bullshit to say that we need to remove rule 8 in order to allow heap conversion of older boats.

 

And while it is still early days and there is no accurate speed readings, the owner claims 17-18 knots + and deeper angles. The current rule 8 boards are achieving far deeper angles and speeds of 25 knots +.

 

The article notes that launching is still an issue and IMO, simply stating that new solutions will arise is not good enough when looking at a rule change.

 

Finally, for this foil configuration, you still need to raise the windward board, something which I predicted was a major issue and something everybody is trying to avoid as hard as they can!

 

Nice try, but I don't see the future of the A Class here.

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interested to note that the first race of the UK Moth nationals was sailed today in 10 knots of wind and a classic Solent Chop. Anybody who has sailed at Stokes Bay and seen the photos of the race (see Y&Y report) will know that it is a real test of whether your wand system is working. And the winner of the race has his wand 500mm out front. Considering the boat has only recently been launched and Dylan hasn't had anywhere near the practice time the others have had, it is clear that having the wand further forward than his main rivals isn't harming his speed.

I noticed in the video that Rashly has a bow sprint now too.

 

I didn't spot that. Somebody really should tell them that they are moving their wands the wrong way and they should be getting closer to the foils, not further away. What are they thinking, making it so hard on themselves. Or maybe it is some sort of handicap system - the better you ar, the further forward you have to have the wand in an attempt to slow them down and make the racing more even. :ph34r:

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From Y and Y forum: yandy

post-30-0-83287300-1435319726_thumb.jpg

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The article is interesting for a number of reasons. First, all credit to the guy for doing the conversion.

 

It should be noted that although the article tries to perpetuate the myth that removing rule 8 makes it possible to convert older boats, it actually confirms that the work done is exactly the same as you do to convert a boat to comply with rule 8. It is therefore bullshit to say that we need to remove rule 8 in order to allow heap conversion of older boats.

 

And while it is still early days and there is no accurate speed readings, the owner claims 17-18 knots + and deeper angles. The current rule 8 boards are achieving far deeper angles and speeds of 25 knots +.

 

The article notes that launching is still an issue and IMO, simply stating that new solutions will arise is not good enough when looking at a rule change.

 

Finally, for this foil configuration, you still need to raise the windward board, something which I predicted was a major issue and something everybody is trying to avoid as hard as they can!

 

Nice try, but I don't see the future of the A Class here.

 

 

SImon

 

If you are going to quote , quote the entire article, you know well I wrote several times that I doubt this conf will become more efficient from night to day over current legal conf, I point that in the article again.

 

And on the work done for apdapting the foils is clearly described after the direct question on the matter.

 

So you will know better on 'agendas', as in fact I been pushing for insert over top to stay put as it favors progressive innovation, and I personally don´t like the launching issues with insert from below , on tide variations we have to solo launch. (You forgot to quote that from previous posts)

 

 

100% of the sailors here, will only upgrade older boats to a full foiling & stable flight solution, thus the US fleet will simplify that, all are asking me a pair of FP Js for their As. Racing performance will be another matter, current conf in my view is untouchable in the all round, (you also forgot to quote that remark from previous posts,...)

 

Bob's words are clear on the pros and cons also.

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The article is interesting for a number of reasons. First, all credit to the guy for doing the conversion.

 

It should be noted that although the article tries to perpetuate the myth that removing rule 8 makes it possible to convert older boats, it actually confirms that the work done is exactly the same as you do to convert a boat to comply with rule 8. It is therefore bullshit to say that we need to remove rule 8 in order to allow heap conversion of older boats.

 

And while it is still early days and there is no accurate speed readings, the owner claims 17-18 knots + and deeper angles. The current rule 8 boards are achieving far deeper angles and speeds of 25 knots +.

 

The article notes that launching is still an issue and IMO, simply stating that new solutions will arise is not good enough when looking at a rule change.

 

Finally, for this foil configuration, you still need to raise the windward board, something which I predicted was a major issue and something everybody is trying to avoid as hard as they can!

 

Nice try, but I don't see the future of the A Class here.

 

 

SImon

 

If you are going to quote , quote the entire article, you know well I wrote several times that I doubt this conf will become more efficient from night to day over current legal conf, I point that in the article again.

 

And on the work done for apdapting the foils is clearly described after the direct question on the matter.

 

So you will know better on 'agendas', as in fact I been pushing for insert over top to stay put as it favors progressive innovation, and I personally don´t like the launching issues with insert from below , on tide variations we have to solo launch. (You forgot to quote that from previous posts)

 

 

100% of the sailors here, will only upgrade older boats to a full foiling & stable flight solution, thus the US fleet will simplify that, all are asking me a pair of FP Js for their As. Racing performance will be another matter, current conf in my view is untouchable in the all round, (you also forgot to quote that remark from previous posts,...)

 

Bob's words are clear on the pros and cons also.

 

I should gave made it quite clear that I was attacking the concept and not the reporting. Sorry for the confusion. The thing that really makes me see red is the continued claim by people trying to get the rules changed that it will make it easier and cheaper to convert older boats and this is not true. I guess I should learn to breath a bit before posting!

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interested to note that the first race of the UK Moth nationals was sailed today in 10 knots of wind and a classic Solent Chop. Anybody who has sailed at Stokes Bay and seen the photos of the race (see Y&Y report) will know that it is a real test of whether your wand system is working. And the winner of the race has his wand 500mm out front. Considering the boat has only recently been launched and Dylan hasn't had anywhere near the practice time the others have had, it is clear that having the wand further forward than his main rivals isn't harming his speed.

 

your observation is a bit incorrect

In all Rockets (both solid and soft winged) the distance between the wand and the mainfoil is still comparable with most other moths (ex. Mach2), because the mainfoil is soooo much forward than in all other designs. I don't have precise measurement, bud I'd say mast-mainfoil are 20cm more forward than in the Mach2 and wand is 30cm more forward than in a Mach2.

 

Right now what you describe is what is happening in latest Exocets (ex. Rashley's boat). They have moved the wand a lot forward, without moving the mainfoil (as far as I know). I haven't talked with anyone with a new exocet, but I suspect they are running comparatively with less gearing, to keep the correct timing of the flap response.

 

My2c

IMHO There is no "right" distance between wand and mainfoil, because the "perfect" distance changes with wave height and lenght (the last is more important). the trend that seems to be emerging in the last couple of years is that having a distance a bit higher than than, say, a Mach2, gives a bit more options, in terms of gearing... so you can probably use a bit less gearing for the same wavelenght.

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Before addressing Phil S's specific comments, I would like to emphasize that I'm not claiming that V foils are uniquely superior to other types, just that they don't deserve to be dismissed so cavalierly as being "too draggy,". as David Cooper did. Quoting from my original response to him :

 

Originally Posted by Doug Halsey:

I would caution you against trying to make sweeping comparisons of different types of foils. Far more important than whether a certain foil is a T or a V or whatever, is what are its dimensions for the loads it's carrying (horizontal span for the vertical lift & vertical depth for the sideforce). And these things change with the conditions. A T & a V foil can be very close in drag in many instances. A V foil can have much smaller drag at high speeds, but it's often too small to be the best at very low speeds. A T foil can be better at lower speeds, but it will almost certainly be larger than it has to be at high speeds.

Which brings me to the 1st point that Phil S made

 

Originally Posted by Phil S :

The graph only shows induced drag, but total drag incudes surface drag. Your argument that the induced drag drops with more dihedral applies only if procected span is constant, and to achieve that the total length and area of the foils has to increase.

 

For a V of 90deg, or 45deg dihedral in the digaram, the induced drag as you state is reduced by 10 -15% but the total area is increased by the 40% argued by David, so surface drag goes up as he says.

The total area only goes up that much when compared to a planar foil with no apparent means of supporting it. And such a foil wouldn't be of any use in resisting sideforce. A more fair comparison would be between T foils & V foils having the same horizontal spans & vertical depths as each other. In that case, the V foil will always have slightly less wetted surface than the T foil (assuming the same chords, of course). About 6% less in the case of a 90deg V.

 

Then there's Phil's 2nd point:

 

Originally Posted by Phil S :

The proportion of induced and surface drag is very sependant on aspect ratio. Short spans have more induced drag, longer spans have less indiced drag. ACat foils must have lots of induced drag. Moth foils would have a lot less.

Agreed. The A-Cat rules severely restrict the span. And even with no restrictions, when designing a foiler with surface-piercing foils, it's hard to get enough foil-span without an unreasonable overall beam. For example, even though my trimaran has a beam of 17 feet, each V foil only has slightly less than 2 feet of span (at the zero-heel, floating waterline). So, it would have a lot of induced drag if I tried to fly at less than about 10 knots.

 

Most importantly though, while the surface drag goes up roughly in proportion to the square of the boatspeed, the induced drag goes down by about the same proportion. In the file I'm attaching to illustrate this point, the red curve represents the viscous drag, the blue curve represents the induced drag, and the green curve represents their sum. This graph is for a very simplified approximation to a Moth foil, with simplified equations for the 2 types of drag.

 

So at high enough speeds, it's well worth it to sacrifice some span or efficiency & tolerate more induced drag, in order to reduce the wetted area & the surface drag. That's when V foils, or surface-piercing foils in general, really come into their own.

 

 

I realize that I've been asked to comment a little about Broomstick, but I'll have to put that off for some other time. (My boats need some attention.)

 

 

 

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post-21863-0-20673700-1435345063_thumb.jpg

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One thing wands can't do on a monohull that they can on a trimaran is simultaneously generate all the righting moment for the boat in addition to all the lift. Dual, independent wands(or "feelers") and a relatively wide boat(to unload the foils) is required. Examples include the Hobie trifoiler, Rave, Osprey and Skat among a few others. Both Ketterman and Bradfield proved that high speed was possible with such a system. The Osprey(18'long X 22' wide foil tip to foil tip) is the only one of the group that allows the crew to move to weather. And it is the only one to foil in as little as 7 knots of wind. The disadvantage is that the boat has to be very ,very strong and that tends to add weight, but the Osprey, despite its beam (and its three hulls), weighs about the same as an F18 cat.

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Before addressing Phil S's specific comments, I would like to emphasize that I'm not claiming that V foils are uniquely superior to other types, just that they don't deserve to be dismissed so cavalierly as being "too draggy,". as David Cooper did.

 

I said a V-foil is a draggy equivalent of a vertical T-foil; not that it's too draggy. You've helped me to change my mind about them though, as I now see that it isn't automatically any more draggy at all, and can be less so in some conditions. I'm now looking at V-foils much more favorably than I was before (and particularly as adding flaps to them could enable them to match the functionality of canting T-foils while removing most of the complexity). If I can find enough time to start building models to try a few experiments, I'll be using V-foils first.

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Uh Oh! - David you used the "m" word, and you know you, will now add you to his list as a reference for justification. ;) (Not that models are bad, per se, just that there is a limit to what they teach - without the extra dimension that full size gives & allowing direct onboard observation.

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interested to note that the first race of the UK Moth nationals was sailed today in 10 knots of wind and a classic Solent Chop. Anybody who has sailed at Stokes Bay and seen the photos of the race (see Y&Y report) will know that it is a real test of whether your wand system is working. And the winner of the race has his wand 500mm out front. Considering the boat has only recently been launched and Dylan hasn't had anywhere near the practice time the others have had, it is clear that having the wand further forward than his main rivals isn't harming his speed.

 

your observation is a bit incorrect

 

Whether increasing wand/foil separation by 300mm makes a boat faster around a course (given the zillion other factors are held constant) will not be settled by one race in relatively moderate conditions.

 

There are so many factors involved in real world situations that any formula for wand/flap/wave interaction is just a rough approximation of an idealised reality. The variability of wind, wave and boat velocities and particularly angle of incidence between boat and waves downwind means that the "ideal" lag between wand movement and flap response varies hugely, even for different parts of the course on a single day. Get hit by a big gust downwind and you may (or would like to, if conditions allow) be rocketing through waves at 90º. Hit a lull and you come up to almost 0º. Whether those events happen in 0.5m or 1.5m chop (which might be top and bottom of the course) has a huge bearing too.

 

BTW, a bit weird to be discussing Moths in a multihull forum.

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