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Fire Arrow, July 24th, 2014 ,first time on foils, 5mph breeze:

2cwo6pu.jpg

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UptiP Ama Foil-first one used on any trimaran in history:

sawm5k.jpg

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Another good thread down the drain.

 

I post some pictures related to the model testing discussion and that sends the thread down the drain?! I don't buy it. There have been a lot of subjects covered here and model testing, UptiP foils on trimarans*, wand controlled main foils on trimarans should certainly be part of any discussion of modern multihull foil applications.

*Macif, Gitana, Exocet 19

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

If the multihull foiling aspirants do not want to learn from the most popular, most developed most, most sucessful and fastest small boat foilng class they might as well put their heads in the sand.

 

The Moth perspective you've brought to the discussion of foils has been outstanding. The discussion is not over but there are specific multihull applications worth discussing as well.

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If this were the first time these images had been posted AND if there had been a relevant discussion as to the recent work as it applies to these images, then sure, have at it. Unfortunately, this particular bit of your "historical irrelevant magic" hasn't left the grass for over a year and all you are doing is the same thing you have always done: that being: cut and paste these pages to death with relentlessly meaningless drivel that only serves to grease your own shabby arguments of efficacy.

 

Get the boat in the water and chase down the problems that it so obviously has under sail and come to a conclusion as to the how and why of its inability to foil with any kind of consistent control upwind and down. Right now, Douglas, you are just a shill for your own tired crap and all of us have seen it waaaay too many times now to find it entertaining.

 

That's why the thread has gone in the shitter. And it had evolved, without you, to a great discussion of things related to foiling in a general sense and lots of readers were learning from the posts by experienced sailors.

 

How about you just let it go and allow the guys here to enjoy the conversation? You have made your point about your expired boat concept enough.

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Works with the iFlap* for early takeoff and increases the total lift fraction at its designed angle of heel.

*see earlier post

 

A fullsize UptiP foil design:

looks like you tip id drooping

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Works with the iFlap* for early takeoff and increases the total lift fraction at its designed angle of heel.

*see earlier post

 

A fullsize UptiP foil design:

 

That doesn't really explain why it's curved. I'm just curious as to why it's better than if it was straight. If it was straight, I'm thinking it might generate slightly more lift for slightly less drag and you'd get a slightly earlier takeoff, so why would you deliberately design that curve in?

 

I'm also puzzled by the way you support the amas from a beam that connects half a mile behind them (and a fair distance aft of the shroud attachment point) - is that just to give you more space for the vital go-fast arrows?

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David, sorry you don't understand it but it is the best, most accurate answer I can give. The curve increases the vertical lift from the uptip portion of the foil at the designed angle of heel(10 degrees) and helps in early takeoff.

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

Regarding the ama--this is an update from the bd thread on the concept of a Two Stage Ama:

--
A while back I was thinking of a 15' version of the Fire Arrow and was troubled once again by calling such a crucial piece in the ama function and design a "curved piece". Then a light flashed on and I came up with a technically correct name for the ama + the "curved piece" : a "two-stage ama". The reason "two stage ama" works is because the curved piece actually is part of the ama though quite distinct from the ama hull. And in sailing, the buoyancy of the ama hull and of the curved piece affects the RM of the boat in two distinct stages: Stage 1- when the ama hull is immersed the RM is enhanced by the 6lb(about 280lb full size) of buoyancy of the " ama hull", Stage 2- when the "curved piece" is immersed the RM due to the immersion of the ama hull is doubled".
So from now on this feature of the Fire Arrow will be called a Two Stage Ama(TSA or 2S ama). Interestingly, in the testing done so far even in the overpowered conditions of the second video the second stage of the ama(the curved piece) has not been submerged. This hasn't been tested yet but ,theoretically, the high dihedral crossarms coupled with the Two Stage Ama(TSA) should allow self-righting from at least 90 degrees(if it ever gets that far).
The 2nd stage of the ama(curved piece) is designed with about the same buoyancy as stage 1(the hull) and together they create fairly high static RM coupled with the over square beam and high dihedral crossarms. But it is stage 2 that determines the run angle of the planing ama surface and of the ama foil. I even considered making the junction between the two adjustable
so the ride angle could be adjusted. The foils AOI(angle of incidence) is adjustable but the ride angle of the planing surface is not-at least on the Test Model. It could be adjustable on the full size version w/o a whole lot of trouble.
But,again, whats really cool about the Fire Arrow concept is that sailing(foiling)- the main and rudder foil working together control the ride angle of the planing surface and the foil! In other words neither can pitch up or down on their own.
-----
Clearly, this Two Stage Ama Design offers a lot both Statically and Dynamically:
1-Statically- the boat is sitting still and hit by a hand of God gust. It is theoretically possible that the boat could be knocked over with the mast horizontal but the two stage ama offers reserve buoyancy after the the ama hull itself is immersed and yet it is not enough to fly the main hull. It is enough, however, to right the boat.
2-Dynamically-The ama hull has two levels of dynamic vertical force:
a. first and foremost the ama lifting foil that works from very low speed on up,
b. Second, and a sort of back up at speed, is the planing hull design of the ama. To start with on the Fire Arrow, the planing surface, only comes into contact with the surface at very low speed with the ama starting to fly before the main hull does. And when the boat is flying the ama performs the same function that the planing ama on Hydroptere does: reserve lift during incidental surface contact at speed.

post-30-0-35737200-1435607831_thumb.jpg

post-30-0-79177400-1435607872_thumb.jpg

post-30-0-46266200-1435607897_thumb.jpg

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Okay, but it decreases the amount of lift you get from the rest of it, and that part's wider and generates more lift at any given point along that lower section of the uptip part of the foil, so you're losing more lift than you're gaining, and what you're losing is disappearing as extra drag.

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That's not correct.

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It may not be correct, but I'm hoping to tap into your expertise on this. If you keep the tip exactly where it is in relation to the C part of the foil and make the whole of the uptip section straight, every part of the uptip section will be generating lift in the same direction instead of having different parts work slightly against each other. The fatter part must be generating more lift than the thinner part, so by straightening it you're going to be making more of the lift from the fat part go closer to straight up, while more of the lesser lift from the section at the tip will go less close to straight up, but the total change will give you more lift in the direction you want it. That's my naive analysis of it, but I was hoping that you could point me to some document which sets out why it doesn't actually work that way.

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I've never seen a document that explains the curved portion of my foil and the slightly curved portion in the earlier rendering. I came up with this design for my boat and it works like an UptiP foil should providing altitude control for the ama and lifting the ama at very low speed and at higher speed. If you look at the picture in post 304, you can see that with the foil in the that orientation the lift from the uptip portion shifts to more directly vertical from the radius to the tip and still performs like an UptiP foil should. To understand how an uptip foil works go back to page 1, post 37 and read the fairly short, but somewhat technical description by Tom Speer.

The basics are that the curved ,semi vertical portion of the foil, and the uptip portion work together due to leeway coupling and that is what controls altitude. The two pictures below illustrate that working on the Fire Arrow: pix "A" the main hull is still sea hugging but the ama is flying, pix "B" shows the main hull flying and the ama still at the same altitude. That's as close as you can get to a perfect response from an UptiP foil: maintaining the same altitude under two different load and speed cases.

Hope that helps.

 

Picture "B"

25ix0k4.jpg

 

 

Picture "A"

fp5frn.jpg

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That description for the "two-stage ama" is one massive bag of crap. Just because you hang some horribly inefficient lump of flotation on the end of a beam does not make it a working concept that betters the design of the boat.

 

For starters, that, and let's be kind here and simply call it, a "form", for lack of a better, less confrontational descriptor. That "form" of yours is the worst looking hydrodynamic shape short of a lumpy box that I could imagine on a boat that hyped as the greatest thing for small multihulls since park benches and installed beer cups. The moment this "form" is immersed, the boat speed will drop like a stone, the immersed drag signature wil soar and this boat will be struggling to get back on its feet again.... all due to the actual shape of the ill-conceived piece of structure.

 

Your desire, Doug, to be cute with this boat and have its shapes be driven by whimsy, rather than sound design practices is amusing to be sure, but it certainly is not a clever departure that makes any sense. So, let's pound this one hard, shall we? Fast boats demand fast shapes if they are to perform in a speedy fashion. I'll direct you to the work of a much greater talent than yours by asking you to take a long look at the decidely well-proven work of Martin Fischer and his, Jessica Rabbit, foil assist trimaran. Even though this boat is meant to spend almost all of its time in the foil borne mode with hardly any actualy immersion of the full-sized amas, the amas are beautifully shaped so that in the event that they are pressed hard under sail, they do not make the boat behave as if an anchor was suddenly thrown overboard with yards of rode and tackle attached.

 

Your little model will do preceisely that when those horrific second stage shapes come into contact with the surface should this boat ever get up to any kind of speed.

 

I suggest that you rethink the shapes, rebuild them to reflect a suitable harmony with the flow characteristics of a well-designed immersed form and stop trying so hard to fool the world with stuff like this.

 

Besides.... they are flat-ass ugly. Buzzkill.

 

.

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Mainfoil wand

-----

The Fire Arrow concept for a trimaran is unique for a lot of reasons but the foils are the main attraction. The dual locked together wands operate entirely differently than any other wand based boat including the Moth and any wand based multihulls. On this boat, the wand controlled main foils' purpose is to fly the main hull in light air, and work with the rudder T foil all the time to control pitch ,the boats angle of heel and the ride angle of the ama foil.

The biggest difference is that, as the boat speeds up, the main foil is nearly 100% unloaded with the ama foil taking the vast majority of the load(approaching 95%).

No other boat with a single wand controlled main foil unloads to this extent, substantially reducing drag while allowing the foil to produce instant lift or downforce as required to control pitch and heel angle.

I'm convinced that a mainfoil like this could substantially improve the handling and safety of large tri's and benefit all tri's in helping to fly the main hull before it would fly due to wind pressure alone. That, in turn, opens design windows allowing smaller tri's to effectively use square or oversquare beam w/o sacrificing light and moderate air performance.

 

2v1kfg8.jpg

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Isn't it interesting as hell...? World class design shops all over the planet have been directly connected to foil capabilities for many, many years now and yet... not one of the dim bulb design shops have managed to produce a single design that is configured in the fashion of our hero, Mr. Douglas Lord's specious, Flaming Arrow?

 

So very interesting that the best and the brightest just have never gotten it when it comes to how foils work, how drag issues function and how handling and safety of sailing machines are manifest in functional design mastery

 

Not one single person.... save for the self-appointed guru of all things foily. the One, the Only, the Master of Disaster, the Highest of High Holiness, Doug Lord. There is one really tiny sliver of a window opening here for his Dougliness.

 

Mr. Donald Trump has, just today, found his ass tossed to the curb from NBC broadcasting after just getting the same, kicked his ass to the curb, treatment from Spanish language TV giant, Univision. Just imagine if someone were to bond Trump and Lord together as spit swapping buddies so they could manifest their self-aggrandizement in a modern new reality TV show.

 

Everybody knows Trump's game about world political dominance and a relentless need for adoring self-importance .... but the Dougster can easily go toe-to-toe with the Donald on the ego need thing and Doug has sailing in his back pocket what with his profound technical knowledge, hyper aesthetics and just flat, beat the crap out of you racing victory experience. I think Douglas could singlehandedly resurrect sailing as a sport and rocket boat sales into the stratosphere... he's that good.

 

Excuse me while I change my diaper. It appears that I've shit myself laughing.

 

.

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I've never seen a document that explains the curved portion of my foil and the slightly curved portion in the earlier rendering. I came up with this design for my boat and it works like an UptiP foil should providing altitude control for the ama and lifting the ama at very low speed and at higher speed. If you look at the picture in post 304, you can see that with the foil in the that orientation the lift from the uptip portion shifts to more directly vertical from the radius to the tip and still performs like an UptiP foil should. To understand how an uptip foil works go back to page 1, post 37 and read the fairly short, but somewhat technical description by Tom Speer.

The basics are that the curved ,semi vertical portion of the foil, and the uptip portion work together due to leeway coupling and that is what controls altitude. The two pictures below illustrate that working on the Fire Arrow: pix "A" the main hull is still sea hugging but the ama is flying, pix "B" shows the main hull flying and the ama still at the same altitude. That's as close as you can get to a perfect response from an UptiP foil: maintaining the same altitude under two different load and speed cases.

Hope that helps.

 

Thanks for pointing me back to Tom Speer's description - I understand it better now than I did on previous readings, but I can't see anything in it that justifies UptiP drooP. I'm still wondering if you really added the curve just to make it look as if it was a clever tweak to the design that's been carefully calculated to improve performance even if in reality it harms it a little.

 

I've also just seen your addition to post 313 explaining the 2nd stage of the ama - that makes more sense now and I can also see why you want it so far back (as well as so high). I find the whole thing a fascinating design which may have great potential, but like everyone else I want to see more video rather than an ongoing bombardment of more stills which tell us nothing about its performance.

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You have a fertile imagination!

If the large, detailed stills I've posted tell you nothing about the boats performance you don't understand what you're looking at-and that's unfortunate. But that's the way it goes.........

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He understands plenty.

It is not a fertile imagination at play - it is nature's inbred scepticism to allow things to speak for themselves & be distrustful of those speaking too much on its behalf.

DouG you have spoken volumes (and volumes) of its capabilities - its time to let the show begin........

Allow your masterpiece to enthral us with its performance.

I am fond of this quote:
“Don’t talk unless you can improve the silence.” - Jorge Luis Borges.

Just dwell on that for a while.

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First day on foils-July 24th, 2014, 5mph breeze, 2 different altitude control systems, first tri in history using an UptiP foil on each ama, one at a time:

 

2najwaq.jpg

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Another good thread down the drain.

 

If folks wouldn't engage the troll - it would have been ok. I know, I used to engage him continually. Offered monetary assistance even. He's just a troll.

 

 

This post is hidden because you have chosen to ignore posts by Doug Lord. View it anyway?

This post is hidden because you have chosen to ignore posts by Doug Lord. View it anyway?

This post is hidden because you have chosen to ignore posts by Doug Lord. View it anyway?

This post is hidden because you have chosen to ignore posts by Doug Lord. View it anyway?

This post is hidden because you have chosen to ignore posts by Doug Lord. View it anyway?

This post is hidden because you have chosen to ignore posts by Doug Lord. View it anyway?

This post is hidden because you have chosen to ignore posts by Doug Lord. View it anyway?

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Doug

FFS. Please stop posting the same single photo taken from a long video shot a year ago as evidence that an idea works. If you insist that it proves something, you have to accept the photos of the boat nosediving and/or it not foiling are just as valid as evidence the boat does not work.

 

Looking at the video and photos, the most that can be claimed is that it might have potential. You cannot take a few seconds from one part of the film and a maximum length of flight of 15 seconds as evidence that the system works. I foiled my A Class on C foils for longer than that but it didn't prove anything other than given perfect and steady conditions, it is possible to overcome inherently unstable set ups. And we all know that an A on C foils doesn't foil properly.

 

When we watch other model yachts foil, it is clear that they do so for the majority of time they are sailing in any given direction. If you want to have any integrity, you need to make claims for your foil system based on evidence of sustained flight in various and varying conditions. I should also add that posting the same images multiple times does not change or prove anything.

 

Please go and sail your model. I think you would be surprised by how many are genuinely interested in the resulting video (and please show us the whole thing and not edited highlights). The problem is that you are following an age old pattern - you build something, you sail it briefly and not enough to prove anything, you post about it for years, you make claims of when you will next sail and you never do. You have followed this cycle at least 3 times since I have been on SA. Please break the cycle.

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Won't happen Simon - we've offered cash, launch assistance, anything to help him get back on the water, the best he's done is promised a mid-June launch date of the NEW model (what happened to the old one? Garage fire?) and now that we're approaching July, nothing, nada, zilch.

 

Everyone put him on ignore, he'll skulk back to BoatDesign or some other place to bother the inhabitants.

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Doug

FFS. Please stop posting the same single photo taken from a long video shot a year ago as evidence that an idea works. If you insist that it proves something, you have to accept the photos of the boat nosediving and/or it not foiling are just as valid as evidence the boat does not work.

 

Looking at the video and photos, the most that can be claimed is that it might have potential. You cannot take a few seconds from one part of the film and a maximum length of flight of 15 seconds as evidence that the system works. I foiled my A Class on C foils for longer than that but it didn't prove anything other than given perfect and steady conditions, it is possible to overcome inherently unstable set ups. And we all know that an A on C foils doesn't foil properly.

 

When we watch other model yachts foil, it is clear that they do so for the majority of time they are sailing in any given direction. If you want to have any integrity, you need to make claims for your foil system based on evidence of sustained flight in various and varying conditions. I should also add that posting the same images multiple times does not change or prove anything.

 

Please go and sail your model. I think you would be surprised by how many are genuinely interested in the resulting video (and please show us the whole thing and not edited highlights). The problem is that you are following an age old pattern - you build something, you sail it briefly and not enough to prove anything, you post about it for years, you make claims of when you will next sail and you never do. You have followed this cycle at least 3 times since I have been on SA. Please break the cycle.

 

Hogwash. I've answered this same bullshit from you multiple times. You don't have a clue what you're talking about.

At the very least, this system-particularly the UptiP ama foil and wand controlled main foil(that unloads the faster it goes-to zero lift) are worthy of serious, intelligent discussion as a new, innovative foil solution for trimarans. Saying it doesn't work because it only worked for 30 seconds or so is complete nonsense. In testing you take one step at a time and this step was successful in that it showed the boat would foil in a 5mph wind and that the radical dual altitude control systems worked. Ignoring that is ridiculous.

Multihull foiling systems aren't just limited to cats-there could be a good discussion about the continued potential of this system as compared to other new trimaran foiling configurations. Because, without a doubt the Fire Arrow system has great potential........

 

tarcea.jpg

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Everyone put him on ignore, he'll skulk back to BoatDesign or some other place to bother the inhabitants.

 

 

No, he won't.

 

Doug is ill (or so he says, anyway) he is desperate for attention and he has his only audience on this and the bd.net site (where his foolishness is indulged like a crazy uncle who always shows-up at Thanksgiving) As long as he can lift his meaty fingers to scroll the mouse, he'll be dropping irrelevant photos here unabated. Normal de-trolling mechanisms just won't work with this guy.

 

.

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Doug - are the UpitP foils on Fire Arrow designed to be raised at any time or do they always stay down?

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On the model, they stay down-too complicated to add RC control of retraction. And it's not necessary. Full size they would be able to be raised and lowered(maybe).


Lowering the ama foil might be worth it in rough water, though the ama foil and planing ama should handle roll just fine.

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Doug pointed me back to post #37, Toms Speers explanation of how UptiP foils work and should work, and I'd like to know how much of it I'm still misunderstanding, so discussing it could be an opportunity to learn a lot more.


The curved part of the vertical foil produces essentially the same lift as it rises. This is necessary to counter the side force from the sail rig, which does not change as the height changes.

 

I assume this is talking about the whole boat rising, but it looks to me as if the sideways lift must vary depending on how much of the foil is in the water.


Because the horizontal lift is constant but the vertical area is reduced as the boat rises, the leeway angle increases. It is the coupling of leeway with heave that is exploited by the L foil to provide vertical static stability.

I can't see how the horizontal lift is constant while the immersed vertical area reduces - if it was, there would be no difference in how much the boat slips sideways.

 

 

The dihedral angle of the horizontal wing is set so that the angle of attack of the wing is reduced as the leeway angle increases. This satisfies the static stability condition that the vertical lift decrease as the heave increases.

 

I think this is trying to say that the boat slips sideways more as it rises higher out of the water, and that sideways movement changes the direction of the flow over the uptip part of the foil, thereby reducing the amount of lift it is generating. This means the uptip part can stay completely immersed and still vary the amount of lift it provides at different depths because the side force from the C part of the foil varies with altitude.


Because the same horizontal lift is produced over a reduced vertical span, the sideways wash in the wake is also greater and the trailing vortices are more intense. This causes a coupling with the horizontal wing that increases the vertical lift, because the horizontal wing acts as a winglet for the vertical part of the foil (and vice versa). The dihedral angle required for vertical stability is greater than what one might expect by looking at the wing alone because it must overcome this wake-coupled influence. The result is there is a range of dihedral angles that provide positive vertical stability and a range of dihedral angles that are destabilizing in heave because of the coupling with the shed vorticity of the vertical part of the foil.

 

Just as the angle that the water crosses the uptip part of the foil will reduce lift as the boat slips sideways more, the angle across the C part of the foil will also change, generating more sideways force from it, thereby countering some of the sideways slip (but the total sideways force must still reduce a bit in order for the boat to slip sideways more to generate these angle changes in the first place). This change in angle over the reduced amount of immersed C foil should indeed result in more intense vortices, so the rest of the above makes sense (if we take it for granted that this coupling effect happens and don't worry about how it works) - the dihedral angle of the uptip has to be greater in order to provide a greater difference in the flow angle of the water across it to counter the increase in lift generated from the coupling effect with the stronger vortices (though there must be a reduction of the strength of the vortices coming off the uptip part, so I'm thinking that that must reduce the lift from the C part of the foil at the same time, and I don't know why that doesn't cancel out the effect, but we can probably take it on trust that it doesn't).


Although there are times when the foil tip has broached the surface, this is not the normal mechanism for providing heave stability in L foils. The best performance is obtained with the hull just above the wavetops and the wing submerged well below the surface. The leeway-modulated heave stability is still effective in this condition, and the induced drag is minimized.

I had wondered how the foils on the Eagle were meant to work, but I'm guessing that this is the explanation as it doesn't look as if the end will stick out above the surface at all. (Haven't heard anything about the Eagle since Doug posted the original pictures of it - has it appeared anywere to show that/if it works?)

 

 

Canting the foil inboard has the effect of increasing the dihedral angle of the wing, which enhances the heave stability. The vertical lift is spread over a greater span because the curved part of the foil is oriented to provide more vertical component of the force. This reduces the induced drag due to the vertical force. However, the induced drag of the horizontal force would be increased, so cant is typically used off the wind when the side force from the rig is less and the side force produced by the foils is correspondingly less. The foils still have to support the weight of the boat, so the vertical force is not lessened, but the relative proportions of vertical and horizontal force are changed, making the canted foil better suited to the operating condition. Cant allows the leeway-modulated heave stability to be increased an an acceptable penalty in the induced drag because of the lower side force and the higher speeds, which also reduce induced drag.

This is where the uptip foil appears to be used more like a V foil, though with the advantage that whenever the whole tip is under the surface, the altitude control continues to function as the sideways force from the C part continues to vary. I don't get the bit about the induced drag being reduced and increased.

 

 

Upwind, the foils are canted to their vertical position to minimize the induced drag from the high side force and reduced speeds. The reduction in horizontal wing dihedral angle with vertical cant impacts the leeway-modulated heave stability, which is why it is much more difficult to achieve stable flight upwind than downwind. The crew had to be more active in trimming the wing and foil to deal with the reduction in natural heave stability, which was very hard on the grinders when flying upwind.

While here its functionality appears to be compromised by the need to remove a lot of the sideways lift from the uptip section in order to reduce/eliminate/reverse any lift to leeward.

 

 

Whether canted or upright, the mechanism for providing natural heave stability was still the coupling between heave and leeway, which led to a reduction in vertical lift because of the designed-in coupling between leeway and vertical lift by virtue of the wing dihedral. Reduction in horizontal/vertical-lifting area due to the foil tip broaching the surface was not part of this primary source of heave stability. Allowing the tip to broach the surface had big penalties in terms of induced drag and increased leeway due to insufficient vertical span.

 

In some videos, the tip appears to cut through the surface most of the time, but perhaps that's unavoidable at high speeds.

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Some designers have a different opinion about the efficacy of the tip of the uptip foil breeching the surface and consider that a key element of altitude control along with leeway coupling.The GC 32 and Phantom regularly fly with the uptip portion of the foil breaking the surface.

The Eagle set a speed record on its initial foils somewhere around 36 knots or more after I posted the original stuff. One of the top guys with the Eagle company told me they were considering adopting the Whisper cat wand based foil system which he called "the best around". The Eagle foils are not uptip foils -they are T-foils with some dihedral-photo from the Eagle Company. GC 32 photo from Gulain Grenier(the inboard tip of the port foil is right in line with the port rudder but clearly above the surface) :

post-30-0-34528500-1435694076_thumb.jpg

post-30-0-72674500-1435694421_thumb.jpg

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I was thinking of the older version as seen in the picture at the top of this page: http://www.eagle-cat...en/eagle-20-hf/

 

To save people from clicking on the link, the vertical part is a slightly curved C, then it turns sideways and runs slightly downwards for a time before kinking upwards but continuing on sideways until it's back level with the bottom of the C part. In short, an L with the horizontal part turned into a shallow V.

 

(I'd forgotten that they switched to a different foil design since then, so this one maybe didn't work out too well, and it's hard to fathom why it ever was the shape it was.)

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"I can't see how the horizontal lift is constant while the immersed vertical area reduces - if it was, there would be no difference in how much the boat slips sideways."

David,

Isaac Newton says it is. 3rd law, force on an objcet has to be opposed by an equal and opposite force, (or the object accellerates in the direction of the greater force)

If the sideways sail force is constant the sideways foil force has to be the same, no matter how high the boat flys. As it flys higher the area gets smaller but the boat normally gets faster so less area is OK, but eventually more angle of attack is needed, which means more leeway, up to a point when the angle gets too big or the area too small and the foil stalls, boat jumps sideways which upsets all the other foil flows and the boat crashed to the water. We say the AC72 do this a few times on the first reach, big splashdown.

 

Same goes for vertical forces. The total lift will always equal the mass of the vessel, (+/- any vertical forces induced from a canted rig.)

 

Coupling these with sloping foils is the new science. Tom Speer has published the best stuff I have seen on the subject.

 

Having the uptip come out of the water does not seem to change this much but the drag from the surface piercing must be significant. Its apparent that its the angles between the foil branches, relative angles of attack and the angle the whole foil is set in the boat which makes most of the differences we have seen.

 

In Moths and in foiling kiteboards, the tip developments have all been towards minimising the chance of the tips cutting the surface. In these small boats crash prevention seems more important than in big stable cats. So to us it seems odd to be controlling height with drag inducing tip ventilation.

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In Moths and in foiling kiteboards, the tip developments have all been towards minimising the chance of the tips cutting the surface. In these small boats crash prevention seems more important than in big stable cats. So to us it seems odd to be controlling height with drag inducing tip ventilation.

In Moths, the tips intersect the surface at a very shallow angle, equal to the angle of windward heel (15 - 20deg. or even less). In cats with uptip foils, I think the angle is more like 45deg. Steep angles are much less likely to cause ventilation.

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Gino Morelli on TNZ foils from Cup Experience. Illustration from the article:

http://www.cupinfo.com/en/americas-cup-gino-morrelli-foils-multihulls-13144.php scroll down to "how to do it"..

 

“The advantages/disadvantages are this ‘V’ is self-leveling,” Morrelli says. “As it raises up to the surface at high-speed, it loses lift, because it stalls a little bit, and it settles back down -- where a true ‘L’ will go completely out of the water, and you have to find another way of controlling the angle of attack and the amount of lift it creates.”
Because the foils extend to their tips at an upward angle instead of flat, as the foil reaches the surface the portion of the foil with water flowing over it, generating lift, is reduced incrementally, and the boat comes down gradually to an equilibrium point. The idea is to balance the forces as speed changes, avoiding the all-or-nothing conditions that a more horizontal lifting foil encounters.

post-30-0-75776600-1435707373_thumb.jpg

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A bit on uptip foils from Dario Valenza(he calls them "acute L/V or just L/V foils")-scroll down to Sunday, March 16: http://carbonicboats.blogspot.com/search?updated-min=2013-12-31T05:00:00-08:00&updated-max=2014-08-02T12:29:00%2B10:00&max-results=24&start=13&by-date=false

 

 

Ilustrations of area and RM comparison of different types of foils by Dario Valenza:

post-30-0-19433300-1435709276_thumb.jpg

post-30-0-05106100-1435709307_thumb.jpg

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Another one of many, many pictures(by Sander Van Der Borch) of the GC 32 with the inboard lee foil tip breaking the surface:

Doug, wouldn't the foil operating like this have similar characteristics to the "V" foil on your tri-at least in terms of surface piercing drag?

 

ddyuyb.jpg

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I can't believe I'm about to do this....

 

Doug,

 

Given the info from Morrelli you've quoted above how can you justify the reverse inflection (LimpdicK) in your foils? By adding that feature you've effectively taken the worst part of L foils and added them to V foils.

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I disagree. The foil works and works at low speed which was exactly what it was designed to do. Design is a compromise regardless of the boat-this appears to be a good compromise for low speed takeoff.

 

sawm5k.jpg

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Blah-blah-blah.... and the ultimate test of all this blahness; The thing still can't stay on foils for any duration, or under any real control.

 

Doug spews testimonial rhetoric as if he knows of what he speaks, and then, he proves his theories by taking four years to construct a boat that can't get out of its own way. In the meantime, many other model boat proponents have built and successfully sailed foiling multihulls of their own design; some in multiples of expressions.

 

And still.... Dougie's boat doesn't work and he's too fearful to put it back in the water to even attempt to sort the issues. If it isn't because of football, it is about a sick relative, or that the wind isn't right, or that he has that pesky catamaran model to build, or he is sick himself, or that the property management people are going to build a seawall with steps. Every freaking excuse to avoid that which is so hugely hanging in front of his mug each and every day

 

Doug's theories mean nothing until he can actually prove them with repeatable results.

 

I'm not a psychiatrist, or psychological counselor, but after this much time with zero happening save for a blame game, I've come to the conclusion that Doug is pretty much just like an alcoholic, or drug addict. Everything around him is the problem, but he's as sparkly as a guy can get... when he's deep into his jones, that is.

 

With the same kindness that I would extend to any other human.... I urge you, Douglas, to get help while you still have some life left to live.

 

End of sordid story.

.

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Narcissistic personality disorder is a mental disorder in which people have an inflated sense of their own importance, a deep need for admiration and a lack of empathy for others. But behind this mask of ultraconfidence lies a fragile self-esteem that's vulnerable to the slightest criticism.

A narcissistic personality disorder causes problems in many areas of life, such as relationships, work, school or financial affairs. You may be generally unhappy and disappointed when you're not given the special favors or admiration you believe you deserve. Others may not enjoy being around you, and you may find your relationships unfulfilling.

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"I can't see how the horizontal lift is constant while the immersed vertical area reduces - if it was, there would be no difference in how much the boat slips sideways."

David,

Isaac Newton says it is. 3rd law, force on an objcet has to be opposed by an equal and opposite force, (or the object accellerates in the direction of the greater force)

If the sideways sail force is constant the sideways foil force has to be the same, no matter how high the boat flys. As it flys higher the area gets smaller but the boat normally gets faster so less area is OK, but eventually more angle of attack is needed, which means more leeway, up to a point when the angle gets too big or the area too small and the foil stalls, boat jumps sideways which upsets all the other foil flows and the boat crashed to the water. We say the AC72 do this a few times on the first reach, big splashdown.

 

Same goes for vertical forces. The total lift will always equal the mass of the vessel, (+/- any vertical forces induced from a canted rig.)

 

Coupling these with sloping foils is the new science. Tom Speer has published the best stuff I have seen on the subject.

 

Having the uptip come out of the water does not seem to change this much but the drag from the surface piercing must be significant. Its apparent that its the angles between the foil branches, relative angles of attack and the angle the whole foil is set in the boat which makes most of the differences we have seen.

 

In Moths and in foiling kiteboards, the tip developments have all been towards minimising the chance of the tips cutting the surface. In these small boats crash prevention seems more important than in big stable cats. So to us it seems odd to be controlling height with drag inducing tip ventilation.

 

Thanks for that explanation - I think I see what's going on now and what it was that was confusing me. If we avoid the complication of the wind speed changing and just imagine that the boat is rising, and if we also imagine that the boat is not moving forwards at all at any point (another simplication aimed at removing any variables due to changes in speed), the area of the vertical foil will reduce as the boat rises and the boat will slip sideways more, and now that the boat's slipping sideways, the force on the rig is reduced infinitesimally, and there will be a equal reduction in the force generated back against that from the foil, but this is a tiny reduction and is nothing like the reduction in the area of foil in contact with the water. We do have a moment of acceleration while the boat increases its sideways speed, but the forces soon balance out again as the extra drag from moving the foil sideways builds up. So, the force is essentially unchanged, as Tom says.

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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.

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

Most recent from Dario Valenza's blog. Friday, July 3rd, 2015: Full comment here: http://www.carbonicboats.blogspot.com.au/

 

"Interest in our L foil kits has been overwhelming. We are at full capacity fulfilling orders and have additional tooling in the pipeline to shorten lead times. Will be sure to publish more images and detailed specs as soon as we get a chance.

 

Market demand speaks clearly and people are voting with their wallets. People who want the best solution within the original A Class box rule far outnumber those willing to invest in complex rule-cheats, chasing a moving target.

 

Other manufacturers are also gearing up to match demand for ‘non Rule 8’ foils. A wise investment on their part. Having more products on offer is great. Whether competing or complementary at different price points, the result is more choice for the sailor and a healthier fleet.

 

Solutions by manufacturers and private builders don’t just include L/V inserted-from-below designs, but also Z/Hydroptere type foils with longer span and less tortured angles.

Every configuration has strength and weaknesses. Personal preference plays a part and competition will further inform us on how the performance envelopes overlap. What they have in common is the pursuit of efficiency unshackled from arbitrary chains."

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Dario should STFU. He has failed to produce a competitive A after 4 years of trying, making him the least successful manufacturer ever. He has proven he doesn't understand the existing rules with his fanciful and stupid interpretations, which were shot down as soon as common sense was used. Now he thinks because a few people have bought L foils from him it means everybody wants to change the rules and everybody wants L foils. The number of compliant conversion sets sold by DNA and Exploder combined with the number of new boats sold show what the vast majority really think (100 plus). Maybe if he actually sailed at some events he would have some idea what the class is really thinking because whether we keep rule 8 or not, nobody wants L foils that you have to lift the windward board, which is his rather limited offering.

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Mouths agape, the courtiers shuffle uncomfortably as the shout rings out from the overhead gallery. The sound of steel against leather as weapons are drawn to protect the erstwhile crown prince and his collected accoutrement making their play for the wayward wishes of the semi-informed pseudo cognoscenti.

 

The play is afoot and it appears.... nothing will stop the flow of the desperate as they virtually leap from one confection to another; never happy with their chioces, always searching for fulfillment... never quite reaching a place to call home.

 

Where is my camera and light kit?

 

.

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Mouths agape, the courtiers shuffle uncomfortably as the shout rings out from the overhead gallery. The sound of steel against leather as weapons are drawn to protect the erstwhile crown prince and his collected accoutrement making their play for the wayward wishes of the semi-informed pseudo cognoscenti.

 

The play is afoot and it appears.... nothing will stop the flow of the desperate as they virtually leap from one confection to another; never happy with their chioces, always searching for fulfillment... never quite reaching a place to call home.

 

Where is my camera and light kit?

 

.

ja ja ja good one

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Mouths agape, the courtiers shuffle uncomfortably as the shout rings out from the overhead gallery. The sound of steel against leather as weapons are drawn to protect the erstwhile crown prince and his collected accoutrement making their play for the wayward wishes of the semi-informed pseudo cognoscenti.

 

The play is afoot and it appears.... nothing will stop the flow of the desperate as they virtually leap from one confection to another; never happy with their chioces, always searching for fulfillment... never quite reaching a place to call home.

 

Where is my camera and light kit?

 

.

Maybe try a better class of drug.

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It's a thread about foils, that's why I would suggest those who are interested with the topic to have a look at the WASZP foils

 

Split tips is not a new idea, it comes from bio-mimetics research and improves the induced drag and the L/D ratio

 

But it's the first time it's done for a large production boat.

 

Probably all foils specialists on this thread could confirm , if it comes from 3D carbon printing ?

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Dario should STFU. He has failed to produce a competitive A after 4 years of trying, making him the least successful manufacturer ever. He has proven he doesn't understand the existing rules with his fanciful and stupid interpretations, which were shot down as soon as common sense was used. Now he thinks because a few people have bought L foils from him it means everybody wants to change the rules and everybody wants L foils. The number of compliant conversion sets sold by DNA and Exploder combined with the number of new boats sold show what the vast majority really think (100 plus). Maybe if he actually sailed at some events he would have some idea what the class is really thinking because whether we keep rule 8 or not, nobody wants L foils that you have to lift the windward board, which is his rather limited offering.

Very insightful comments. You are obviously an astute observer of actual sailing and not blinded by the keyboard bullshit publicity.

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AMAC on WAZP bog, (somewhere else he says they are nylon):

"We design a new set of ‘Eagle’ Wing Tips, this time with only 3 feathers so we could make them stiffer. We also realize that the angle of attack was too low on the feathers – a mistake I probably would not have made if we had to go direct to moulds like we did with the Mach2. The 3D printer has taken focus out of the initial design process allowing you to just build and test.

But it is starting to become obvious that while the eagle tips might be more efficient, they need care when launching. This is really brought home when on the beach the mainsheet is caught between the fingers. I pull on it and do damage. OK, the 3D print is not as strong as the production injection moulded ones will be, but it is easy to see the potential for damage.

So I decide that night that we need to go much more conservative with the tips, even the end plate tips on the rudder have lost a bit off the tip misjudging the ramp. At 10:30 that night I design a new bulb like tip, by morning a pair is printed and by lunchtime painted.

But the wind does not show. 4 days we wait. Sat 26 is the last day before I have to pull it apart to take to bits of it to TFW in Italy."

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Thanks a lot Phil,

 

Even with greater AR foils, split tips should improve L/D ratio for Moth too, unless rule-boxe...

 

I feel confident somebody is brainstorming at the moment about it.

 

A-Cat foils with split tips is probably the next to come.

 

Cheers Everybody

 

W

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It's a thread about foils, that's why I would suggest those who are interested with the topic to have a look at the WASZP foils

 

Split tips is not a new idea, it comes from bio-mimetics research and improves the induced drag and the L/D ratio

 

But it's the first time it's done for a large production boat.

 

Probably all foils specialists on this thread could confirm , if it comes from 3D carbon printing ?

 

Injection moulded plastic tips inserted into aluminium extrusions. Very flexible.

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AMAC on WAZP bog, (somewhere else he says they are nylon):

"We design a new set of ‘Eagle’ Wing Tips, this time with only 3 feathers so we could make them stiffer. We also realize that the angle of attack was too low on the feathers – a mistake I probably would not have made if we had to go direct to moulds like we did with the Mach2. The 3D printer has taken focus out of the initial design process allowing you to just build and test.

But it is starting to become obvious that while the eagle tips might be more efficient, they need care when launching. This is really brought home when on the beach the mainsheet is caught between the fingers. I pull on it and do damage. OK, the 3D print is not as strong as the production injection moulded ones will be, but it is easy to see the potential for damage.

So I decide that night that we need to go much more conservative with the tips, even the end plate tips on the rudder have lost a bit off the tip misjudging the ramp. At 10:30 that night I design a new bulb like tip, by morning a pair is printed and by lunchtime painted.

But the wind does not show. 4 days we wait. Sat 26 is the last day before I have to pull it apart to take to bits of it to TFW in Italy."

by Doug Schickler:

"Injection moulded plastic tips inserted into aluminium extrusions. Very flexible."

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

Thanks Phil and Doug-great info! Sounds to me like a step too far for the Waszp but I'll bet we'll see lots more development in the Moth.

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"...Sounds to me like a step too far for the Waszp but I'll bet we'll see lots more development in the Moth"

 

 

That's just flat hilarious, coming from you, Doug.... the Queen of all things too complicated.

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The Waszp foil wingtips(tentative?), from AMAC's blog:

 

xcvdrd.jpg

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AMAC on WAZP bog, (somewhere else he says they are nylon):

"…while the eagle tips might be more efficient…"

 

The key is "more efficient" with "than other options" unstated. Tip options with the WAZP foils are limited due to the constant chord, so while feathers make sense in this case, they likely don't offer better performance than current tapered foils with an equivalent span of a WAZP foil with tips.

 

AMAC isn't big on prototyping, I'm surprised any of this stuff has come to light. Maybe someone just wanted to play with a 3D printer.

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That's just flat hilarious, coming from you, Doug.... the Queen of all things too complicated.

 

 

If you don't quote, or better don't reply, those with him on ignore remain blissfully (and wilfully) ignorant of his posts. ;-)

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That's just flat hilarious, coming from you, Doug.... the Queen of all things too complicated.

 

 

If you don't quote, or better don't reply, those with him on ignore remain blissfully (and wilfully) ignorant of his posts. ;-)

 

+++

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Boys, boys, boys.... you simply can not unsee what has already been seen.

 

I know that it is Comicon week in 'Dago, but at some point, you are going to have to drop the pretense of your artificial innocence.

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Another very interesting short article from Dario Valenza with an excerpt below: http://www.carbonicboats.blogspot.com.au/

 

It is inescapable that we must be able to get all our upward lift from our leeward foil if we ever want to be able to efficiently foil upwind. Also if we want to foil in light airs downwind, and if we want to keep pushing max speed downwind in fresher conditions.
Recent work with AC45 Turbo test platforms, and smaller cats, has shown that differential rudder rake, such that the windward elevator foil produces downforce, can add significant speed. (emphasis DL)
It may be that using the windward foil to pull down could pay, bringing about a return to four-point systems.

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Isn't this significant extra speed only going to appear in a gale? If you've got your weight out as far as it can go and the wind's still trying to tip you over, clearly you can potentially gain more speed by generating downforce from a windward foil/rudder. It may be sufficiently advantageous that it will end up having to be done in order to be competitive, even though it won't be fun if that foil comes out of the water or if it generates enough force to snap something expensive if you go too fast. Personally, I'd rather find ways of moving crew weight further out instead, and/or move the foils further out too (and not have them go down through the hull), though rules limiting boat width will prevent that for many classes.

 

 

After the bit you quoted, Dario says:-

 

But it is certain that span restrictions that require multiple surfaces to get sufficient lift on the leeward side are driving development to a dead-end. If such restrictions persist, more changes are inevitable as people invent elaborate rule-cheats such as having several foils in each hull.
Much better to encourage simplicity.

 

I wonder if it is such a dead end. If you move the main foil a lot further forwards, you'll need to add lift to the rudder to maintain balance, but at the same time you'll reduce the need for so much lift in the main foil. People are talking about needing another 25% of lift, but moving the main foil a long way forward might remove that need while making up for it by having a rudder which provides substantial lift, and you might even end up with equal lift from the two. The front foil would also provide some of the pitch control that you get on a Moth by placing the wand out in front - a foil placed far forward would respond to the waves sooner and adjust the pitch earlier in the same way. The restrictive rules on A cats might drive evolution in this direction, creating boats that are radically different from those of today and which might result in a better solution than you would get by rushing to copy what has already been done.

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But it is certain that span restrictions that require multiple surfaces to get sufficient lift on the leeward side are driving development to a dead-end. If such restrictions persist, more changes are inevitable as people invent elaborate rule-cheats such as having several foils in each hull.

Much better to encourage simplicity.

 

I wonder if it is such a dead end. If you move the main foil a lot further forwards, you'll need to add lift to the rudder to maintain balance, but at the same time you'll reduce the need for so much lift in the main foil. People are talking about needing another 25% of lift, but moving the main foil a long way forward might remove that need while making up for it by having a rudder which provides substantial lift, and you might even end up with equal lift from the two. The front foil would also provide some of the pitch control that you get on a Moth by placing the wand out in front - a foil placed far forward would respond to the waves sooner and adjust the pitch earlier in the same way. The restrictive rules on A cats might drive evolution in this direction, creating boats that are radically different from those of today and which might result in a better solution than you would get by rushing to copy what has already been done.

 

Really???!

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C Fly's canard arrangement seems to work well in rough water. I was curious as to Davids reasoning about enhanced pitch control with a wand "out in front".

Phil, do you think the "way forward wand" enhances pitch control on a Moth?

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I don't know for sure but she was a very interesting surface piercing foiler with retractable foils and movable ballast.

post-30-0-82400100-1436840187_thumb.jpg

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what ever happened to spitfire?

 

http://www.windrushyachts.com.au/sailing-boats/spitfire

 

050310foiling4.jpg

 

It was at Windrush last time I saw, could be wrong who knows what I stumbled across ;) haha

 

What are you talking about movable ballast Doug, It did not have moveable ballast, it had water ballast in each hull.

 

Amazing aero design on the project I might add.

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More and more moths are getting bowsprits to move the wand forward. I do not know of anyone taking them off this year. I have not tried one yet.

The first one I know of was John Ilett in 2008 at the Torbole WC. Its taken a while for others to appreciate the value.

John was also one of the 3 WA boats with the wand on the back of the centreboard in 2005 at the Black Rock WC. This idea has not been seen on a moth since, well until the 3 French/Ward scows at Sorrento.

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David, I think this is like what you are getting at?

The forward canard control foil on C-Fly is a special stepped superventilated section which works at the water surface. At Foiling Week 2014 they kept it under covers but I did sneak a peak, just enough to say it would not be easy to copy. It is intended to maintain constant height so that the aft main foil controls its lift by rising and hence reducing its angle of attack as speed increases.

Same concept on Vestas Sail Rocket, the planing hull forward maintains constant height while the aft foil adjusts AoA for speed.

I first saw the principal on the Rich Miller foiling sailboard from the 1990s, and Ian Ward (who shoed me the Miller articles) tried the Miller concepts of a planing bow canard on some of his early moth foiling experiments.

All rely on the centre of gravity being just in front of the main foil so it carries most of the weight while providing a small bow down pitching moment if the bow foil/ski comes out of the water.

Unless you get the high tech design like C-Fly I think the idea will have trouble in rough water, where a surface following planing ski will either give a very rough ride or dig in and cause loss of control.

Whether the bow foil is also the rudder like C-Fly or just a pitch/height control is not significant, and the aft foils do not have to be outboard either, so it would be possible to test the idea within the ACat rules, with or without Rule 8

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More and more moths are getting bowsprits to move the wand forward. I do not know of anyone taking them off this year. I have not tried one yet.

The first one I know of was John Ilett in 2008 at the Torbole WC. Its taken a while for others to appreciate the value.

John was also one of the 3 WA boats with the wand on the back of the centreboard in 2005 at the Black Rock WC. This idea has not been seen on a moth since, well until the 3 French/Ward scows at Sorrento.

 

Just curiously Phil, do you think the wand didn't work too well on its own before, yet coupled with the adjustable length wand is now phenomenal?

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The wand on the bow is about 1.25m forward of the main foil. The bowsprit is allowed to be 500mm max. So with the wand it is possible to get a 40% increase in the spacing and hence 40% increase in reaction time. Note this is still a lot less than is possible on the larger catamarans shown on earlier posts.

 

It makes very little difference in flat water or upwind but downwind in waves the logic is that getting the pitch correction sooner has to be an advantage.

 

When the waves are big enough to risk ventilation, getting the bow up in the troughs and down over the crests is vital.

If the pitch up does not happen until the foil is at the trough, then the hull will touch down or worse the bow will crash into the next wave.

If the bow down does not happen until the foil is at the crest, then the foil will fly out of the downwind face of the wave and the boat will crash, badly.

 

So there are some very good reasons for the wand to be well forward of the foil, and good logic in getting it as far forward as possible.

 

Except there are some limits.

25kts is about 13m/s so the boat travels the 1.25m in less than 1/10 of a second. An extra 4/100ths of a second does not seem like much. In practice its hard to see what is happenning until it starts to happen well. Your perceptions are somewhat dirupted by violent immersions.

The moth class also limits bow fittings to 500mm and this includes the wand, so if the bowsprit is 500mm the wand can not extend beyond vertical.

With bow mounted wands its normal for the flat water operation angle for the wand to be back at about 45deg. The wand length is adjusted so that when it swings forward to vertical the foil is still submerged in the troughs. If the water gets rougher the wand swings forward of vertical and prvovides generous up flap and pitches the bow down as described above. The wand clears the water and by going forward reduces its effective length and will not touch the water again until the boat is lower than when the wand first left the water. This makes for safe flying.

If the wand is already mounted at the maximum of 500mm, then the range of legal movement allowed means that the extra generous movement needed in big waves has to be achieved aft of vertical. In this case the wand will not leave the water until the boat is at its highest and will recontact the water as soon as it comes back down to the same height.

Basically the bow mounted system has a system height deadband without a time deadband, while the legal bowsprit mounted wand has no deadband and no safety margin.

I have not studied how the bow mounted wands are used, there was only one at Sorrento, and as Rohan had not raced a moth for many years, his excellent performance indicates his boat must have been working well for him. There are more bowsprits in the UK but I have not studied any videos either. But if someone starts doing very well with them I am sure their close competitors will be watching.

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Sometimes, people get too caught up in theory and don't pay attention to what actually happens on the water. The position of the wand is a case in point. Moth sailors aren't stupid. in fact, they include some of the leaders in foil development and some of the best sailors in the world. Among the front runners, they will try almost anything sensible (and sometimes not so sensible) to get an edge and/or make the boats faster and/or easier to sail. Based on that premise, we know the following.

 

Wands have been tried on the back of the centerboards by more than one person. In every every case, they were removed. Many top Moth sailors are moving their wand as far forward as they can, using 500mm poles out the front of the boat. At very least, we can be certain that it is no worse than the conventional set up, otherwise they would have been changed back. So the evidence from real testing is that it is either equal to or better than the conventional wand position on the bow. But we can go further. Top sailors have had it fitted to their new boats having sailed with it previously. This tells us that they must believe there is a benefit, otherwise they would go for the simpler bow mounted system.

 

As said, the guys doing these tests aren't stupid and aren't imagining benefits. Therefore, we know with a high degree of certainty that on Moths, having the wand as far forward as possible is the best place, or equal best place. It doesn't matter how often people say that this is problematic because of theoretical reasons, the results speak for themselves. therefore, if reality doesn't match theory, it is the theory that needs to be reconsidered. And just because people cannot explain something that has been proven on the water doesn't mean the test results are wrong.

 

In addition, when discussing the ideal placement of wands in relation to the actual surface they control, there is no benefit in discussing one off cases where different wand positions haven't been tried and compared. Just because a boat flies well with a particular wand position does not tell us anything about how ideal that wand position is. It is only after extensive tests of different positions that include true side by side comparisons across a range of wind and sea conditions can any conclusions be drawn.

 

Believe in the evidence of extensive testing and be skeptical of theoretical gains which have not been tested properly.

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It's not a case of anyone being stupid-the results seem to speak for themselves in the Moth class. But in order to progress it is important to understand why the forward wand works.

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what ever happened to spitfire?

 

http://www.windrushyachts.com.au/sailing-boats/spitfire

 

 

 

It was at Windrush last time I saw, could be wrong who knows what I stumbled across ;) haha

 

What are you talking about movable ballast Doug, It did not have moveable ballast, it had water ballast in each hull.

 

Amazing aero design on the project I might add.

 

 

So water ballast is not movable ballast? As far as I know, Spitfire moved its ballast(500kg) side to side(or hull to hull) just like Hydroptere does. I talked to Brett Burvil(I think) about this a long time ago and I'm fairly sure he said the ballast could be on one side or the other-how it was actually moved I don't remember.

http://marine.bdg.com.au/spitfire_features.html

 

Although testing is still in the early stages, Spitfire is already close to meeting its performance estimates. It 'takes off' (lifts up on its hydrofoils) at around 12 knots - which it can achieve in 10 knots of wind. Once on the foils, the bumping of waves disappears as Spitfire smoothly accelerates up to speeds of 25 knots, in 14 knots of wind; 30 knots in around 20 knots of wind. We expect it to get to its maximum speed (without ballast) of 35+ knots in 25 knots of wind or less. With water ballast tanks fitted, the estimated top speed is above 40 knots.

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

Tom Speer on water ballast for multihulls-comment about Spitfire:

http://www.boatdesign.net/forums/boat-design/water-ballasted-multihulls-6504.html post #7

 

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

 

"The Spitfire hydrofoil catamaran uses water ballast. When I asked Mark Pivac why he went with water ballast instead of using hydrofoils to create all the righting moment (ala Rave), he said, "Why lift the same load twice?" And, of course, he makes perfect sense.

 

Water ballast isn't needed until there's enough heeling moment that the lee hull or foil is supporting the whole craft. After that point, one can use down-force on the windward hydrofoil or an equivalent amount of water ballast in the windward hull. If you elect to use water ballast, the lift on the lee hydrofoil has to increase by an equal amount, which will incur a drag penalty. If you elect to use hydrodynamic down-force, the lee hydrofoil still has to oppose the down-force and incur the same drag penalty. But in addition, the windward hydrofoil has its own drag penalty. Hence, Pivac's comment about lifting the same load twice - once for the leeward foil and once for the windward foil.

 

However, for a high-speed craft more sail area is not necessarily a good thing. So it may be better to back off on the heeling moment than to add weight so as to sustain a greater moment. For example, I have two different sized sails for my landyacht. Provided there's enough wind to move the yacht, the small sail is invariably faster than the large sail. It's only in the light winds that the large sail pays off.

 

I think the real question regarding water ballast for a multihull is, "Is the extra sail area worth it, or would a lighter boat with less sail area be faster?" In principle you can get any righting moment you want from a mulithull just by making the platform wider. But you have to think of stability in two-dimensional terms with a multihull instead of just roll stability. So when the beam is great enough, pitch or diagonal stability become the limiting factor. Of course, water ballast can be used aft as well as forward. But you're submerging the lee hull even more so you need reserve buoyancy to cover the water ballast, too. You get into a vicious circle that may not be buying you much additional performance.

 

The real problem with multihull stabilty is the downwind trap. And the most promising solution for that issue is new types of sails, not water ballast."

__________________

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The wands original purpose was to control altitude when Bradfield first invented it so he put the contact point of the wand with the water very near the f&A CG of the boat. I'm wondering about using the wand to control altitude and pitch-does that open up the system any kind of cross coupling in certain conditions? I'm interested especially in any reports from people who have actually sailed the bowsprit version.......

 

Some good video of wands in various conditions. The first video shows more bowsprit equipped boats. The second video is in more intense conditions:

 

 

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Many top Moth sailors are moving their wand as far forward as they can

Just out of curiosity, who exactly are you referring to ? Any of the top 10 from the recent Worlds ?
All new exocets (rashley, plus new boata of goodison,greenhalgh etc) now have a telescopic bowsprit wand,mounted at max lenght (50cm). Rockets (fletcher etc) have always had a bowsprit,but never went the full 50 cm,to be able to use a normal adj wand (if you go full 50 cm with an adj wand,as soon as you start to shorten wand you go illegal.)

I heard a chat of sone m2 guys trying,butjust chat.

 

The whole point is to be able to handle the chop with less gearing. I'm probably upgrading to full 50 cm telescopic system next autumn, but I don't like the idea of having to change my current friction wand sysyem to a spring+cleat system. Friction wand imho is smoother to operate,especially when it gets fresh to frightening

 

Doug I hace a bowsprit boat,but with mainfoil forward as well so the spacing is higher than normal boats,bit not by much.

As I said;one advantage is you give the flap a bit nore time to react,so less gearing required,less pitch,more speed (hopefully)

Second advantage is you can put the paddle more close to the centerline,but you still have a limit you can't cross,because if you go too close to centerline your wand wake starts to induce mainfoil ventilation,when going upwind on starboard(especially in conditions where you apply sgbificant elastic tension). So it's a very subtle tradeoff

 

Edit: I forgot the biggest advantage! Bowsprits are cool! :D

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17mika, thanks for the info!

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David, I think this is like what you are getting at?

The forward canard control foil on C-Fly is a special stepped superventilated section which works at the water surface. At Foiling Week 2014 they kept it under covers but I did sneak a peak, just enough to say it would not be easy to copy. It is intended to maintain constant height so that the aft main foil controls its lift by rising and hence reducing its angle of attack as speed increases.

Same concept on Vestas Sail Rocket, the planing hull forward maintains constant height while the aft foil adjusts AoA for speed.

I first saw the principal on the Rich Miller foiling sailboard from the 1990s, and Ian Ward (who shoed me the Miller articles) tried the Miller concepts of a planing bow canard on some of his early moth foiling experiments.

All rely on the centre of gravity being just in front of the main foil so it carries most of the weight while providing a small bow down pitching moment if the bow foil/ski comes out of the water.

Unless you get the high tech design like C-Fly I think the idea will have trouble in rough water, where a surface following planing ski will either give a very rough ride or dig in and cause loss of control.

Whether the bow foil is also the rudder like C-Fly or just a pitch/height control is not significant, and the aft foils do not have to be outboard either, so it would be possible to test the idea within the ACat rules, with or without Rule 8

 

I was commenting on more than one issue and trying not to mix them together. My comments about putting the foil further out to the side rather than through the hull are driven by three needs - greater RM, ease of removing foils before landing, and making the boat take up less space on land (and when trailing).

 

My other comments were based around the A Cat rule restrictions and the idea that 25% span is needed for the foils than is allowed. When I mentioned a "front foil", I was thinking of what is currently the main foil, but moved further forward. The further forward you move it, the more leverage it has to lift the mass which will be centered further behind it, and all you need is to move it far enough forward for the lift it's currently generating to be sufficient to do the job without adding 25% of lifting power to it. More of the mass will now push down the rear of the boat instead, so you need the rudder to generate more lift to compensate, but that's where you'd be able to gain the 25% increase in overall lift. If the front foil is moved far enough forward, it could end up using less span than it does now while the rudder might end up generating an equal amount of lift, at which point there would no longer be a "main foil". With the front foil further forward, the pitch of the boat would be adjusted sooner by waves, though that may be of little use given that the foil itself is going to reach the wave just as much sooner, so it may be of no actual help at all in that regard - I now suspect this advantage can only apply to devices like wands controlling flaps on foils further back. So, the only thing to look at here is whether the foil span limitation problem can be got around by moving the foil forward and adding more lift to the rudder. If this has already been experimented with and is known not to work, then it's a no go, but if it hasn't been looked at properly yet, it may offer a route for the A Cats to evolve down in order to generate more lift within the current rules (unless there's a rule I don't know about restricting how far forward the foil can go). The C-Fly and the Spitfire both have a main foil with the weight almost centered on it, so they aren't representing what I'm imagining. It's interesting to see the C-Fly though, and particularly as it suggests that the front foil doesn't disrupt the performance of the main foil too badly - that makes me worry less about the problems of generating more of the lift from the rudder foils in the water disturbed by the other foil ahead of it.

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David, since the forward foil you want to move is attached to the daggerboard you have to be careful about how far forward in can go w/o creating too much weather helm. A guy by the name of Bill Roberts came up with a concept he called "shared lift" where the daggerboard was reduced in size and moved forward and the rudder area was increased. It was on his Arc 21 and he said it worked well.

But there is well known science that says loading the mainfoil with 75- 80% of the boats weight results in a boat with good pitch stability so getting around that may not be so easy.

 

http://aquarius-sail.com/catamarans/arc21/index.html

 

 

some catsailor discussion of moving the daggerboard forward on a cat foiler including a comment about "shared lift" :

http://www.catsailor.com/forums/ubbthreads.php?ubb=showflat&Number=279133

 

 

 

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Thanks Doug. That second link tells me what I need to know:-

 

The problem with that is that in order to have stability and control as you transition through lifted flight and non-lifted motion, the main lifting elements need to carry a large majority of the load...just like an airplane. If the foils are moved further toward the ends of the craft (sharing more lift between the boards and the rudders or the wing and the elevators), the dynamic changes in lift as it transitions states is wild and difficult to control. This was one of the (re)discoveries that the America's cup campaigns discovered...they had to put the boards near the CG of the boat - otherwise it would porpoise wildly when it tried to get into the air and was unstable while transitioning. It is the same reason that the main wing element on most aircraft carries almost all of the weight of the plane.

 

It sounds though from that as if it does work once you're up and flying. If you had a way of reducing lift at the back to ensure that the front always goes up first, and then slowly increase lift at the back until it's flying too, that might fix the control issues during the transition phase. That's something I'd like to experiment with using models.

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I'm probably upgrading to full 50 cm telescopic system next autumn, but I don't like the idea of having to change my current friction wand sysyem to a spring+cleat system. Friction wand imho is smoother to operate,especially when it gets fresh to frightening

There's no need to use "spring+cleat" for a telescopic wand, a continuous friction system is quite easy too.

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I'm probably upgrading to full 50 cm telescopic system next autumn, but I don't like the idea of having to change my current friction wand sysyem to a spring+cleat system. Friction wand imho is smoother to operate,especially when it gets fresh to frightening

There's no need to use "spring+cleat" for a telescopic wand, a continuous friction system is quite easy too.

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