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Waynemarlow

T foils v Z foils, why are we persevering with all the cost of Z foils

197 posts in this topic

Its sort of becoming a bit a money game of who can create the latest iteration of Z foils and how on spending all that development cost, only the very best who practice relentlessly, can wobble along, up on those foils for moments of time, before about a week later, they decide that they are not really that great and we had better get a new version underway.

 

Guys just avoid all the pitfalls and development costs of the Z and such like foils ( after all they were designed to get around a rules problem, not because they were the best and easiest solution to the foiling problem ), just use good old basic T foils which have all the lift in all the right places, have a well proven R&D development over many years, are structurally easier to make, lighter, more easily fitted with replacement horizontal foils when new lift sections are developed and can be adjusted on the fly by either mechanical or electrical means .

 

But to really understand this you are going to have to get over the fact that they may just sit a tad outside the hull line. Is that such a bad thing, nah its such a minor negative that in about a weeks time you will have gotten over it and be enjoying those really efficient foils which are half the price of the Z foils and can be retro fitted to virtually every class of catamaran out there.

 

If you want to get all anal about the fact that you cannot retract them higher than the hull for beaching onto sand, then foiling is probably not for you as every little grain of sand in that dagger board case is going to trash your foils, far easier to beach on a nice trolley with foils still inside the case which keeps all that sand out of all that very important slot areas.

 

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There is a lot wrong with your view. You think that Z foil development is different from T foil, but it is not. This is because you are comparing development classes with one design. You also seem to suggest that Z foils are significantly less stable than T Foils. They are not.

 

To prove this, look at the N17. It has Z foils and foils as well as any beach cat foiler and doesn't need the foils consistently updating. On the other hand, Moths spend a fortune on developing new foils and carry a whole quiver of them to events, probably spending more than is spent with the A Class.

 

When you have a development class, you will always get development and there seems to be a pay off between easy to foil and speed. There also seems to be a bit of a myth regarding A Class development. There are a very few "works" sailors who get foils to try but in reality, the fleet has not been constantly updating because the foils have not been available. Most people have only updated from their first set to the latest 10's, which over a 3 year period isn't too bad. I have heard of 11's and 12's but they have not been used in racing and aren't available to the public.

 

If I was designing a one design foiling beach cat from scratch, I would not look beyond Z foils. Cheap and easy with no moving parts, they can be designed to perform as well as any other foil.

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+1 Wayne!

 

T foils .... can be retro fitted to virtually every class of catamaran (boat) out there.

 

Laser, Opti, Arrow etc while some have been a good laugh and not huge on performance, the underlying theme is that they work on old and original seahugging designs. Although the moth crank think looked initially complex to the newby, it is getting pretty common now, and cheap Waszp-like alloy foils IMHO will just appear on all sorts of beach boats that were about to go to the dump. Think also of the success likely when the numerous Weta tris out there sit up on durable T foils after the (arguably) poor performance of the float C-foil attempted on one hull.

There could be some cheap fun-times coming?

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If I was designing a one design foiling beach cat from scratch, I would not look beyond Z foils. Cheap and easy with no moving parts, they can be designed to perform as well as any other foil.

Maybe we are at the point where Z foils are nearly there, but that nearly there has so many economic problems by the way of production cost and maintenance, that why should we take the economic cost of nearly there, when in the now T foils are still ahead despite not having the R&D being thrown at it. Are we just being followers of fashion rather than if we simply just back off a bit ( allow foil tips to be outside the hulls ) and enhance what has already proven to be good enough, to really enjoy foiling for all.

 

The recent in foil development has been Rules driven both in the AC and A Class, why should the average sailor have to be limited to those classes foibles ?

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From here: http://www.catsailingnews.com/2017/04/performance-sailing-nacra-17-foiling.html#more

 

Bora Gulari:

 

I would dare to say pitchpoles in the Nacra 17 are basically a thing of the past with the proper technique. We did try sailing two sails downwind I think it can work but will take a lot of practice to get the technique right. The coordination between the helm and crew is going to be next level stuff, gone is the inherent stability of a cat. The boat is now sitting ontop of a teeter toter in the roll axis and there is a lot of inertia, feels much more like a big skiff than a catamaran in that axis to me.
Seems like a major consequence of "Z" foils-where the "T" foil resists roll......
================================
T-foils have their own problems which is one reason why some foil designers think they should be installed canted 10-20 degrees like the Vampire.
Greg Ketterman said that the problem was different pressures on the same side of a t-foil which, he said, was why the Hobie trifoilers inward pointing surface sensor controlled "L" foils were faster than Bradfields "T"foils.

post-30-0-42726300-1492000155_thumb.jpg

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Here are a few other data points:

 

* The Phantom Essential chose Z boards. Looks very good and stable with people aged 65 and also youth sailors foiling along.

* The new F18 Cirrus has cases designed for what look like must be Z type boards for its foiling option.

* The Scorpion F18 Open design is going to offer Z boards.

* The Nacra 17 MKII as noted above.

* Rumors of others.

 

For sure the learning curve has taken some time and cost, but designers and builders are doing smart things now to make development easier going forward. Things like larger board widths inside the case so the narrower underwater board doesn't scrape as it goes down the case and provides a way for the case to hold many board designs without case bearing modifications.

 

At least in the A-Class, I believe two Zs can cost less than a moth horizontal and vertical. Zs are not perfect as noted above but they are a solid technology with less rigging and complication than other solutions.

 

I see new T classes are going with main and rudder lifting foils outside max beam of the boat. That is also possible with Zs that go outwards first (eXploder was doing this in the A before I saw this in the AC50s) and of course with any rudder. For me personally, I want to sail with a boat with foils only inside max beam. I do not want to have a trapeze line break or just missing the trap in a hurried tack result in a Frank Cammas kind of injury or worse.

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+1 Wayne!

T foils .... can be retro fitted to virtually every class of catamaran (boat) out there.

 

Laser, Opti, Arrow etc while some have been a good laugh and not huge on performance, the underlying theme is that they work on old and original seahugging designs. Although the moth crank think looked initially complex to the newby, it is getting pretty common now, and cheap Waszp-like alloy foils IMHO will just appear on all sorts of beach boats that were about to go to the dump. Think also of the success likely when the numerous Weta tris out there sit up on durable T foils after the (arguably) poor performance of the float C-foil attempted on one hull.

There could be some cheap fun-times coming?

The best T to make a Weta go fast is a Tohatsu😎

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From here: http://www.catsailingnews.com/2017/04/performance-sailing-nacra-17-foiling.html#more

 

Bora Gulari:

 

I would dare to say pitchpoles in the Nacra 17 are basically a thing of the past with the proper technique. We did try sailing two sails downwind I think it can work but will take a lot of practice to get the technique right. The coordination between the helm and crew is going to be next level stuff, gone is the inherent stability of a cat. The boat is now sitting ontop of a teeter toter in the roll axis and there is a lot of inertia, feels much more like a big skiff than a catamaran in that axis to me.

 

Seems like a major consequence of "Z" foils-where the "T" foil resists roll......

 

Of course a foiling cat loses the inherent stability of a conventional cat. That happens with all the current crop of foiling beach cats whether they use T foils, Z or V foils. It seems that all 3 types of foil produce a very similar sailing experience. Reading what Charlie has said about how the S9 behaves, it would be familiar to anybody who sails a foiling cat and certainly those who sail an A. It seems to me that the different styles of board don't have as much impact on handling characteristics as some might think.

 

There seems to be a belief that a foiling cat should or can be as easy to sail as a conventional cat. The simple truth is that it cannot be. Even ones that are meant to be easy to sail still needs some learning of new skills, as seen when the editor of Yachting World (or a similar rag) took the Whisper for a test sail. The resulting video showed everybody that even the easiest foiler was far from easy.

 

Before Doug starts, I am sure he can produce examples of one off or old school foilers which he will claim"prove" you can produce easy to sail examples, but what we are talking about are conventional geometry beach cats.

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A Class,

 

Not trying to get into a pissing match but Z11's were used in racing at Aussie Nationals by Stevie Brewin per your own statement. I've since heard of much later iterations of boards, but you are correct that Z10's are the latest production. All the development that has happened in the A's is because of Rule 8 and ways around it. The A cat would have had more stable foiling 3 years ago like the Phantom Essential and the Nacra 17 Mk. 2 are showing today if more of the lift was done on the main boards and the rudder winglets could be used primarily for pitch control, not lift addition outside the slower speed range. Foiling tacks and gybes may be possible. Right now none of this is possible without a top speed penalty under rule 8. Its up to someone to build it and show the world what can be done outside the 1.5m rule, but I don't think this means going to a wand based foiling solution (Off yer rocker proved that was slower in their implementation waaaay back in 2007) or really an insert from the bottom solution that has its own difficulties and penalties, and besides is outside the max beam rule on the A cat.

 

Personally I am afraid that costs will go up on the boat if we keep marching down the closed development path because it is leading to longer and longer rudders with higher and higher winglet lift requirements that require high modulus carbon to maintain stiffness and therefore strength at these lengths. Maybe that doesn't change with higher lift main foils but I suspect it will stabilize more.

 

We are still cheaper than a Moth for parts, a single bottom main foil (without the vertical) is several hundred $$ more than a pair of complete main foils for an A cat from Exploder: http://www.sailingbits.com/foils/

 

All up our foiling package for 2 boards, 2 rudder verticals, 2 rudder winglets, complete rudder hardware and complete slider assemblies we are at less than $4k. The two vertical struts and two foils on a Mach 2 2.3 are over $7k total!! I would like the class to preserve this, and certainly the main boards not changing helps but if we start marching down the Moth path we can easily end up at $4k for rudder hardware alone (maybe DNA is already there).

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Sam,

 

No question about it there are a couple of guys who are team riders that are testing out boards that aren't really in the market, and it wouldn't surprise me is Brewin is one of them. But so long as we are a development class with major manufacturers involved that's always going to be true. It is almost their enire R&D budget, and obviously there are going to be a lot of false starts along that route.

 

One of the things about the A-Class unlike other classes is that I don't know that the guys at the tip of the spear are really looking for more stable flight. Ashby, Mishka, et al. Simply don't care that much about stability because they have already mastered the techniques to foil with what we have. Instead they are looking for faster foils, with the caveat that faster includes being able to foil a larger part of the time. For the A-Class this is really ok, we are a development class with boats that aren't designed for the new sailor, and with very little margin for the inexperienced. Not that the boats are hard to sail, but little allowance is made for inexperience if any.

 

So we will constantly favor the fastest foils around the course at the expense of accesability and that's ok, that what the class is supposed to be.

 

And I am not kidding, if you show up at most A-Cat events with non-conforming foils you would be welcome to sail. Doesn't matter if they are insert from the bottoms, intrude on the 1.5m rule, have wands, or use ferrets to adjust foil angles. The only change to the rules I think would get absolutly shot down is a move to wands, but we would let you sail to test them. Frankly the cost of going to wands is just too high. I don't think anyone would relish the idea of tripling the cost of foils no matter what the performance gains.

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Guys, its well and good constantly talking about A Class's but the worlds Cat fleet is only a teeny wheensy little bit made up of A Class. Now we have F18's F16's, and dozen other classes all going ummm just maybe I cold modify my boat to foil.

 

Now most of these are over weight and probably will never make a great foiler, but at club level they could be a load of fun, if the right foiling package could be used. Z foils are just not going to do this as the bending loads are going to be enormous and only the highest modulus carbon in Auto clave conditions are going to suffice, but at great cost.

 

Are the bending loads on a simple T foil going to be the same, are the costs going to be the same as in we would probably need a wand ( the S9's is pretty simple and not that difficult to replicate surely ) , are the costs of a horizontal tip going to be as expensive as replacing the whole board in a fast grounding, there's lots of permutations we need to think about other than just how fast we can go.

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samc99us

 

Sorry, I forgot Brewin used 11's. I believe he has been using 10's since. The point I was making is that you cannot buy all these developments because they are prototypes and the reality is that the foil designs have remained remarkably stable with SNA not having made any changes and Z10's being standard for the best part of 18 months.

 

The rudder depth issue is the same with our foils or with T foils. There is even a suggestion that they would get deeper with T's. I am also not so sure rudder foils are really getting bigger. They were too small to start with and are now a bit bigger, but compared with Moths, they are still pretty small. I also believe that high modulus carbon is being used already.

 

StumbleNova

Maybe in the USA people would be welcomed with non class compliant foils but I think the picture is very different elsewhere. I think it would be looked at very negatively here in Australia.

 

I also don't get the thinking of those who promote this. Our boats now foil very well. They are easy to use with simple insert from above boards. There is no complexity such as wands. You really couldn't get a more simple set up and it works. Note how others are adopting what we do because it is so simple and efficient. If we change the rules now, we risk serious damage to the class. The development cycle would start all over again. I would be very surprised if we would gain anything. In some ways, that suggests there is nothing to fear by opening things up but what it would do is promote uncertainty just at a time we are beginning to see some stability. Unless a major development is seen elsewhere which would leave the A's behind, I think we need to send a very clear message that the rules won't change and we are happy with what we have.

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Can we leave the emotive words "A Class " out of this as yes Z foils are probably now developed enough and the rules in place for a long enough period, that the A Class is working in a way that seems to work for them.

 

But what about the more heavy and much less expensive club boat that the owner is willing to spend a few K and get a rejuvenated package that he or she will want to sail and enjoy. Yes it won't end up as fast, won't be as agile, won't probably cover their costs, but may well put a big smile on their faces again.

 

In these cases should we take the simple option of T foils over the Z foil ?

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A Class Sailor,

 

My point was that at weekend regattas we are welcoming all comers. It's only at serious regatta's like North Americans where they would be an issue. So far no one has shown up with non-compliant foils that show any gains over compliant ones, so there is no impatus to change the rules. But let's say someone showed up with Z foils that intrude on the 1.5m rule by 100mm and those foils were proven to be just as fast but much more stable, I think you could get some buy in from the class to change the rules to allow them. Minimal if any cost different, a direct plug and play, and a better boat. So why object to them?

 

The failure to show they are better however seems to indicate that development path isn't playing out very well. Or at least no resources have been spent to try it.

 

 

Wayne,

 

I think what you are missing is T foils are not the low cost or low complexity solution you seem to think. T foils must be wand controlled which means lots of small carbon bits and very high retrofitting costs. Plus the foils themselves have a lot of internal mechanical linkages. A complete set of foils for an A-Cat run $4,000, to replicate those foils from a Moth would cost about $15,000. If older boats want to try retrofitting then stronger Z foils are a much better option than T foils.

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Seems to me there is another factor when considering "Z" foils vs T-foils: draft of the foils. Especially in places like Florida . "Z" foils draw a lot more water than equivalent T-foils or wand controlled "L" foils designed specifically for shallow draft. And I think lessons can be learned from Bradfields wand systems that predated the Moth in terms of simplicity as well as the relatively simple Whisper foil/wand combo.

 

Whisper foil/wand combo:

 

Photo from Henry White/catsailingnews.com :

 

 

2rrt5hf.jpg

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[...]

 

Wayne,

 

I think what you are missing is T foils are not the low cost or low complexity solution you seem to think. T foils must be wand controlled which means lots of small carbon bits and very high retrofitting costs. Plus the foils themselves have a lot of internal mechanical linkages. A complete set of foils for an A-Cat run $4,000, to replicate those foils from a Moth would cost about $15,000. If older boats want to try retrofitting then stronger Z foils are a much better option than T foils.

 

That's the crux of it for me. It doesn't matter if the foils are Z, J, L, whatever and are a little slower in straight line speed, their ease of use and lower cost is a huge bouns.

 

I hope multies continue with development of wandless designs. The progress so far has been amazing and there is every indication that they will reach a level comparable to current wand controlled T foils, but without the added complexity and cost.

 

It may mean that A Class has to modify their rules to a 1 metre gap rather than 1.5 m, but that's not an issue for other classes (or new ones).

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It may mean that A Class has to modify their rules to a 1 metre gap rather than 1.5 m, but that's not an issue for other classes (or new ones).

 

That certainly looks like it may be the limiting factor on stability for the A, the video of the N17 appears very stable not to mention foiling gybes after only a few sails. I thinke there was a comment from DNA a little while ago saying much the same thing.

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Perceived stability and speed is a function of the skipper - especially on a foiling boat. Please observe an average sailor on multiple foilers before you form your opinions on stability and speed. Ashby would look great on any foiler - not so much the rest of us. Just my opinion, probably not yours - no problem - just a data point.

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Charlie

You make the point I was trying to make. With all of these beach cat foilers, the sailor makes a bigger difference than the type of foil used. My views on this has been reinforced by reading your experiences which seem so similar to what I have experienced with the A.

 

I think 3 things have a major impact on how sailable a foiler is. The first is weight because the lighter the boat, the more it reacts. Then there is "power" or the amount of sail area. Speed is the last factor and it doesn't matter how good the foil system is, the faster you go the more sensitive the steering and the more chance that fairly small steering inputs can lead to dramatic moments. I believe that these factors will always make the A a "wild" foiler irrespective of what we do with the rules.

 

We have seen really clearly that you can make a great foiler with Z foils and it has the advantage of being the most simple system. Even on a 2 man boat, leaving both foils down is a big advantage while having no complex wand/flap system is also great. So for converting existing cats to foils, by far the cheapest and easiest way of doing this is to use Z foils. A cheap way forward for the future might be to simply buy the kit Nacra have produced for the N17, once initial demand has been met. Or the gear made by the Flying Phantom guys. You would need to strengthen the transoms but other than that, fit a new c/b case and away you go. The other great thing about Z foils is they are the cheapest option costing little more than a conventional foil made to the same standard

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I think you ignoring the "wave" factor , wery important, as well as the gusty winds, all of which prevent an easy and stable flight.

 

I do not think that a kit foils as S9 cost more than kit foils N 17?

Have you DNA prices, N17, etc.?

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Be interesting to compare prices Michele, would you in the future offer a kit as I do remember you having a larger horizontal foil. Equally do we know the all up prices of the DNA, Nacra, Exploder.

 

What I'm pretty sure is if some enterprising company offered a foil package for the F16's and F18's they would be pleasantly surprised on the interest.

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Last year I paid approx 3000 euro all inclusive for a complete retrofitting set from exploder (rudders, rudderstocks, z10s and entryslider and exit for the boards).

 

Marvelous price, I think. A little more than a new sail, but speed has (or hopefully will) increase way more ;- )

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The N17 conversion kit costs 7900 euros but that includes materials for hull strengthening, 1500 euros for labour and a new spinnaker. The kit has some really nice parts, such as the rudder rake system and a belt drive board adjustment set up. Take the kite, labour and additional material off and I think you are under 5000 euros

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The latest promo video for the FP Essentiel shows exactly why Z foils are tempting for a mainstream foiling cat. Pull them up, beach your catamaran, have a picnic.

 

Fiddling with the wand mechanism is awkward -- I know this firsthand. Putting the beach wheels in the right spot with T-foils is a f*g hassle. We do it because we love what we're doing. We're early adopters.

 

If the S9 and Whisper had Z foils that insert from the top, and perform reasonably well, I'd take them.

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Sorry guys , but in my wiev there are nothing better than wand sistem .

Also all existing cars all around the world have automatic contros sistems , power without constrol its a big error .

1 month ago we have test my little 13.4 feet with 24 knots wind and really big wave , 2 meteres with pipe , only surfers on wather , only wand sistem boats have show fly in this extreme conditions .

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ita 16 you make a valid point, I do think the wand systems might be a bit more heave stable, though I think a competent sailor in big breeze can handle the boat. L/J foils have been used in the conditions you mention. Most of the time the problem is speed as mentioned above. Weekend warriors don't have the time to train and learn to control the boats at high speeds, but many of these guys can't handle the boats in breeze as is, so the foil choice isn't really the issue.

 

Have you seen the video of the Nacra 17 full kite hoist on the foils? That level of stability I have only seen from top A cat sailors and only downwind in a straight line. Yes, I understand the 17 crews are very experienced, but looking at the video in detail its the boat doing the work, not the crew. They are already doing foiling gybes and most crews have less than a week on the boat. No one is full foil gybing an A. Other boats will get there, but it requires a good pair of Z foils and nice big symmetric rudder elevators, optimized for low drag and high pitch stability.

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Showing my age here: Trifoiler and Rave were true pain-in-the-!$@. Much worse than my S9. Broken rudder castings were pretty common.

S9 beach wheels are outside the hulls so no danger to wands. Don't know about Whisper. I beach launched the S9 twice so far: Newport was a nice calm beach with offshore wind. Piece of cake. Canyon Lake was a nightmare. Rocks, choppy shallow water, onshore wind. Took three people. Now I launch from a trailer on a boat ramp. One person job. I am not familiar with Whisper wand system so I have nothing to compare with the S9. Haven't given us any trouble so far. We did receive great tips from Federico and Michele.

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S9 in high wind - up to 34 mph Saturday - is the most fun I have ever had on a boat. Never feels overpowered. Hard to keep it off the foils. I am learning not to panic when those pointy little bows start pointing down.

I was always grossly overpowered on my old cats in those conditions. I have no experience in Z or other foils to compare.

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Have you seen the video of the Nacra 17 full kite hoist on the foils? That level of stability I have only seen from top A cat sailors and only downwind in a straight line. Yes, I understand the 17 crews are very experienced, but looking at the video in detail its the boat doing the work, not the crew. They are already doing foiling gybes and most crews have less than a week on the boat. No one is full foil gybing an A. Other boats will get there, but it requires a good pair of Z foils and nice big symmetric rudder elevators, optimized for low drag and high pitch stability.

I would suggest that most of the top 30 or so Sailors at the Australian A Class nationals can foil downwind with the amount of stability being discussed, up until about 15-18 knots. The problems that then occur are nothing to do with the foils and everything to do with the amount of power and the high speeds. The biggest things that stops people from foiling an A downwind properly are foil set up and not knowing what to do. I was all over the place with my new boat until somebody told me how to set the foils up properly. It was then like sailing a different boat.

 

The S9 seems like a great boat that is fairly under powered compared with, say, an A and that makes as big a difference to ease of sailing as the foils.

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ACS: S9 indeed underpowered in light wind, I guess that's why it is good in a blow. First jib kit added to one of our lake boats just this morning. We'll see how that works.

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......and yes, it seems to me that T foils and rudders could be added to any cat - the cost/benefit ratio may not be worth it - best bet may be floater A cat. I have spare foils, anybody down here have a spare floater?

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In a podcast from last summer i think, Bora talked all about Z vs. T vs. L/J/C foils and specifically how much more stable the Z foils are in the N17v2. His point was that even for the best Olympic sailors, L/J/C foils are simply too much work. As for wand-controlled, the big issue there is, as explained above, the added expense and significantly more complexity of the linkage and adjustments. For a Z, you put them down and leave them there. With a J, you have to pick up a board on every maneuver, and timing is critical. With a T/wand, you have wand length, gear ratio and height adjustment, all of which need to be adjusted when changing upwind/reach/downwind.

 

Finally, the directness of the linkage between wand and foil is extremely important, especially when the wand is bow-located, as all experienced foiling designers and sailors will tell you is essential for pitch stability in chop. If you can't keep the slop out of the linkage - even a few mm here and there - ride stability is massively reduced. The tolerances are extreme and as any engineer will tell you, extreme tolerances are expensive to produce in a factory.

 

Search the Sailing Anarchy Podcast on stitcher or itunes to find the discussion. I think we talked about it in the VPLP interview as well, but it's all a blur.

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This doesn't make "Z's" sound all that stable in roll:

 

From here: http://www.catsailin...iling.html#more

Bora Gulari:

I would dare to say pitchpoles in the Nacra 17 are basically a thing of the past with the proper technique. We did try sailing two sails downwind I think it can work but will take a lot of practice to get the technique right. The coordination between the helm and crew is going to be next level stuff, gone is the inherent stability of a cat. The boat is now sitting ontop of a teeter toter in the roll axis and there is a lot of inertia, feels much more like a big skiff than a catamaran in that axis to me.

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Ok the consensus of the A Class sailors are that Z Foils are the biz. Those who have sailed the S9 and the Whisper are going, well for those who are not that expert, then they do make learning to foil a bit easier.

 

Certainly from my only experience of foiling, which was the S9, I can support that as within a few hours it was pretty easy to get up on the foils and stay there ( for good measure it was pretty marginal conditions on the day ). So my gut feelings are that for the minimum hassle of wands ( sorry Clean but they are now so widely used and the foibles well known that I think the days of them being overly complex and expensive, maybe are past ) that for the the vast majority of sailors, the average club sailor the pros of the wands out way the cons.

 

But are we just following the aviation development pattern with foils and moveable flaps, certainly in gliders the early wing shapes meant that they needed flaps to operate over a wide speed band and yet by the early 80's a new wing shape was developed which had about 90 % of the speed band and probably overall ( as it took the pilots knowledge out of the equation) was not unsimilar in performance to the fully flapped gliders.

 

Which leads me to wondering why we actually need wands. Perhaps the Moth has taken us down a path which on the longer water line lengths of the Cats, we shouldn't be quite so concerned about, that of fore and aft roll. With our better understanding of foils, just maybe the ease by which we can move along the cats whilst on the trapeze ( unlike the Moth ) may well mean a fixed foil whose AOA can be adjusted by our body movement maybe is all we need.

 

Certainly on my limited time on the S9 I did suspect that you could control the height using body weight, as good as the wand. Mmmmm food for thought.

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Waynemarlow,

I have disconnected the wands for displacement sailing in very light winds to see a nice performance gain. Will try again in higher winds to see what happens. Might have some more crash videos 😊

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Wayne

I believe there is far more to the issue than you make out. T foils will always be significantly more expensive that single piece foils such as Z's, even without the wand and flap system and the heavier the boat, the worse the problems get. Wandless T foils have been played with and you end up with either a nightmare to sail or something like the still born Tomahawk system of some years ago which seemed to offer promise but was actually a huge disappointment. You need to have some sort of "mechanism" for heave stability and without a flap, there is none at all with a T foil, which means they would be far harder to sail than any other foiling system.

 

If you have a boat with a wand or 2 in the case of a cat, there is the need to keep the system working. I don't know what the experience has been like with the S9 but on my Moths, this takes constant maintenance. Flaps need to be looked after and eventually rebonded and while it seems that the cable system on the S9 works OK, with Moth we moved away from cables because of many issues including friction and maintenance.

 

I am not really sure why you are so much against Z foils. The Nacra 17 and the Flying Phantom Essential seem to be doing rather well on them and Moth sailors i know who have tried A's say they are far easier than a Moth to sail , so why are you fighting so hard against what seems like a great solution which is cheap, lacks the moving parts and makes the boat easy to handle on shore and launching.

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This doesn't make "Z's" sound all that stable in roll:

 

From here: http://www.catsailin...iling.html#more

Bora Gulari:

I would dare to say pitchpoles in the Nacra 17 are basically a thing of the past with the proper technique. We did try sailing two sails downwind I think it can work but will take a lot of practice to get the technique right. The coordination between the helm and crew is going to be next level stuff, gone is the inherent stability of a cat. The boat is now sitting ontop of a teeter toter in the roll axis and there is a lot of inertia, feels much more like a big skiff than a catamaran in that axis to me.

 

When I first read this post, I started to type the string of abuse it deserves, but then decided to wait a day, calm down and now I am going to attempt a proper, measured response.

 

Doug, you are yet again showing your total lack of knowledge and understanding. Bora states very clearly that he is comparing the boat's behaviour with the inherent stability of cat. All foiling beach cats with any foil configuration have shown themselves t be significantly less inherently stable than a normal cat. It is so obvious only somebody with no understanding of boat dynamics would find his comments surprising or try to make the conclusions you seem to be making. Read everything foiling cat sailors say. watch the videos. Even on boats like the Whisper and S9, they inherent stability of a cat has gone. I just reread what Charlie said about his recent sail on his S9, when he capsized as the boat reacted unexpectedly. He clearly says it behaves very differently from any cat he has sailed. That is the nature of light weight foiling beach cats. You will never get one to have the same inherent stability of a standard cat and if you think that is possible, you really do have less understanding than I thought.

 

i also admit to being puzzled by Wayne's fight in favour of T foils. I have just seen and rad more of Charlie's experiences in launching and protecting his foils. I like the big fender he uses to avoid banging the foils on the dock and how he launches, but it doesn't give a universal solution for all situations and looks a bit of a pain. It really is hard to argue against insert from above foil systems that can be done once launched or before returning to the beach and it gives you one less thing to have to learn or compensate for.

 

Wandless T foils have been tried on a beach cat and it was unsailable.

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Just to put it out there my ideal boat would basically be a superfoiler with centerline T foils one of these https://buy.garmin.com/en-US/US/p/557294, a flight controler and a couple servos. Anyone that says that a z foil boat is better behaved than a moth should think real hard about it, Scale an A cat to 11ft and it would be almost unsailable, the interia in the pitch axis makes it a bit easier.

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1) Even on boats like the Whisper and S9, they inherent stability of a cat has gone.

 

2) Wandless T foils have been tried on a beach cat and it was unsailable.

 

 

1) Bora was talking roll stability and on a cat with dual independent wands, properly set up, the roll stability is great. See the S 9 video sailing with no crew. Roll stability on boats like the wand based Osprey(very light) is extraordinary due to the wide beam(22' on an 18' LOA) which unloads the foils while they generate RM using automatic windward foil downforce coupled with automatically increased lift of the lee foil.

---

2) The Eagle Cat used wandless T foils. They have since changed to a version of an UptiP foil. I wrote to Heiner Wolfshofer at Eagle Cat and, while these foils worked and allowed a 36.8 knot speed in a 25 knot wind, Heiner said that as far as he was concerned the Whisper wand controlled foils were the best available and that they were considering switching.

 

Impressions from the editor of www.catsailingnews.com:
"This might be the first set of foils aiming to what kites are doing on refining the foiling wings. Also windsurfing boards have a super stable ride with similar setup, no wands, but full body trim & control , which is difficult to replicate (the crew influence on the flight by body dynamics) on a 20' double handed cat, but I think on a Stunt 9 things can get interesting.
Nevertheless the Eagle team seems to have achieve some quite stable flight as reported by Roland, will be interesting to see a video next. Kudos to Eagle for innovating that path that in my view could
be really efficient even in racing arenas in the future.
The yard has a long time reputation on building high quality cats, The great Beto Pandiani has used Eagles for his ocean crossings for instance."
Pictures by Michael Ehlers,www.eagle-cat.com

post-30-0-45637400-1492349929_thumb.jpg

post-30-0-52418800-1492349960_thumb.jpg

post-30-0-45335200-1492350002_thumb.jpg

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Just to put it out there my ideal boat would basically be a superfoiler with centerline T foils one of these https://buy.garmin.com/en-US/US/p/557294, a flight controler and a couple servos. Anyone that says that a z foil boat is better behaved than a moth should think real hard about it, Scale an A cat to 11ft and it would be almost unsailable, the interia in the pitch axis makes it a bit easier.

 

Thanks for the Garmin link-very interesting as is your choice of boat!

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Well yes, any foiler is logistically more difficult than a floater - especially in shallow water - hence my trailer launching and retrieval - we are lucky to have that option here. AFAIK, everyone else uses beach wheels, which are not so good here. And yes, a lightweight foiler is an order of magnitude less stable than a heavy old floater - but well worth it. The increase in the fun factor as I learned to get around a course on the foils is difficult to describe. Nothing like it - a real thrill.

Foil designs: if you look at aviation, particularly Burt Rutan's designs, you quickly realize there is more than one solution to achieving controllable flight.

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Just to put it out there my ideal boat would basically be a superfoiler with centerline T foils one of these https://buy.garmin.com/en-US/US/p/557294, a flight controler and a couple servos. Anyone that says that a z foil boat is better behaved than a moth should think real hard about it, Scale an A cat to 11ft and it would be almost unsailable, the interia in the pitch axis makes it a bit easier.

 

So something like Mirabaud LX but with electrically controlled foils instead of mechanical?

 

I can see how it would work, but how much force would you need the servos to generate? Over the course of a day you would need a pretty good amount of power, which means large batteries. How much additional weight this system would add I don't know. Butt operating two/four servos nonstop for hours is going to eat up a lot of power even if they don't draw much per stroke.

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Well yes, any foiler is logistically more difficult than a floater - especially in shallow water - hence my trailer launching and retrieval - we are lucky to have that option here. AFAIK, everyone else uses beach wheels, which are not so good here. And yes, a lightweight foiler is an order of magnitude less stable than a heavy old floater - but well worth it. The increase in the fun factor as I learned to get around a course on the foils is difficult to describe. Nothing like it - a real thrill.

Foil designs: if you look at aviation, particularly Burt Rutan's designs, you quickly realize there is more than one solution to achieving controllable flight.

 

Another example: the surface piercing(no wands) canard configuration "4X4" foiler C Fly: http://www.c-fly.co.uk/

 

Vid from C Fly website:

 

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Just to put it out there my ideal boat would basically be a superfoiler with centerline T foils one of these https://buy.garmin.com/en-US/US/p/557294, a flight controler and a couple servos. Anyone that says that a z foil boat is better behaved than a moth should think real hard about it, Scale an A cat to 11ft and it would be almost unsailable, the interia in the pitch axis makes it a bit easier.

Nobody has said anything about scaling an A to the size of a Moth. It's also all very well a world class Moth sailor saying this, but most of us live in the real world. I can foil an A on Z foils pretty well. I tried a Mach 2 Moth a while ago and have never spent so much time swimming. Somebody tried to tell me that the Moth was easier in a straight line than an A, but I am not convinced. Maybe with more practice and flat water, but I know I would need a lot more practice.

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Just to put it out there my ideal boat would basically be a superfoiler with centerline T foils one of these https://buy.garmin.com/en-US/US/p/557294, a flight controler and a couple servos. Anyone that says that a z foil boat is better behaved than a moth should think real hard about it, Scale an A cat to 11ft and it would be almost unsailable, the interia in the pitch axis makes it a bit easier.

So something like Mirabaud LX but with electrically controlled foils instead of mechanical?

 

I can see how it would work, but how much force would you need the servos to generate? Over the course of a day you would need a pretty good amount of power, which means large batteries. How much additional weight this system would add I don't know. Butt operating two/four servos nonstop for hours is going to eat up a lot of power even if they don't draw much per stroke.

 

 

Bora said "superfoiler" so I guess he could mean something configured like the Superfoiler-a trimaran with UptiP ama foils---- plus centerlineT foils?

 

Superfoiler: http://www.boatdesign.net/forums/multihulls/new-trimaran-foilers-55834.html

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no ama foils, damnit I replied

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no ama foils, damnit I replied

 

thanks......

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Doug its nothing that personal, but over the years you have driven me to madness more than once

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Bora, I understand. Believe me-the feeling is mutual but I wish you well.

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Doug - what does mutual means in your world? The way we translate it into danish makes 0 sense in the context?

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To the contrary, I'm not against Z foils at all, I favour all flavours of development, but at this stage of foiling, I'm not yet convinced that Z foils are yet as easy to foil as their proponents make out. One only has to look at most foiling A's and N17's Online videos to see some of the worlds best sailors, who have probably spent more time practicing on them, than I would spend in 5 years of sailing, looking pretty ordinary.

 

Perhaps my expectations maybe are just a bit too high, but with the level of investment in both time and use, together with the advances in computer modelling and materials, one would have thought that the Z foil would be better than what they currently are. I'm open to being convinced though and my A Class Flyer is sitting waiting for a set of foils of some kind in the near future, but it won't be any of the current crop of Z foils as I don't fancy investing my capital into something which I don't consider to be proven enough to make the change worthwhile.

 

As to T Foils, you guys have given examples of 20 year old boats, they did not have the benefit of the knowledge on foil shapes that has been garnered in recent years. Also I would consider the 20 ft foiler as having far different requirements as the 14 footer, you don't see any open class gliders that are not flapped for the same comparison.

 

I just think perhaps that class requirements have perhaps taken us down not the easiest paths to foiling and that if we open our minds a little then we may well come up with a better foiling solution that fits a far wider range of boats.

 

Charlie you have perhaps the one boat that could be tried as a fixed foil shape as a T foil, have you tried setting about 2 degrees of AOA and then adding 1 degree of flap and locking it off, the least wind, the more flap you will need. Then perhaps add another degree to see what happens. It would be an interesting experiment.

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Waynemarlow: I love what you are suggesting. The adjustment mechanism for the trailing edge flap can be disconnected from the wand system and either allowed to "float" or mechanically locked in place. The entire board/foil assembly can then be angled as desired within the confines of the board adjustment system. However, I have no idea how to measure AoA. A static measurement is possible (hey Will!) but weight shift on the boat will of course change that considerably. Nevertheless, I would love to make a few high speed passes just to see what happens. Heck, I've been pitched off often enough, I think I can handle it. I'll make sure the chase boat stays close. I bet Michele and his crew are laughing their asses off, because I suspect they have already done all this.

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Charlie

If you are going to try going wandless, set the flap to neutral. I think you will find anything else will have zero chance, because it will always give you an asymmetric section which means you will make it really tough to reduce lift when needed.

 

Don't worry about setting the foil exactly because it is impossible and as you point out it changes as you move. The amount you need also changes depending on speed and I suspect to stand any chance, you will need to alter it depending on conditions. What will be more important is the difference between rudder and main foil, but that will be trial and error.

 

I don't think the idea will work at all because it has been tried on a number of boats. The only way is through specially designed foils, which clearly your foils aren't. I know it has been tried an an A and it made the boat totally unsailable when with wands attached, it was fine. You will need to move fore and aft pretty aggressively, anticipating how much the boat is going up or down, plus use a lot of sheet.

 

I don't understand Wayne's logic. He thinks Z boards don't work well enough but they have a pretty good degree of automated ride height control. Now he wants you to try a system which will have zero automated ride height adjustment. It has to be significantly harder than Z foils,

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ACS: yes, I understand. I've gone wandless in light winds.

Helps considerably: in full displacement mode flap is all the way down, pretty draggy. The wake actually changes when you detach the flap mechanism. I'll go out and try a quick flight, stop the boat and immobilize the flap, then sail again. I am curious to see what happens. Note: I keep the Teleflex lubed with a high qualty spray, but there has been absolutely no other maintenance on the control system. 14 months sailing now.

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Z foils do have a degree of automated ride height, accepted. T foils with wands have automated ride height, accepted. However neither can fully interpret the whole range of forces operating on the foils such as sea conditions / the swell height, speed, the amount of lift a foil needs to keep the hull air bourne at a range of speeds and give the necessary lee slip prevention for the sail to change the forces to a forward motion..

 

A human brain can however, once its been trained, make those decisions in a much more varied and in a way which evaluates the consequences of those decisions. As with the lessons learnt in gliding though, if you give the skipper too many things to change such as AoA and flap angle ( amount of lift the foil produces ) then it gets overly complicated for the average pilot, its far better to simply have a foil design that gives a wide ranging speed band, giving the optimum lift over that range allowing the pilot to simply fly the glider. yes they loose peak efficiency but that can be gained in the way the glider is managed.

 

Z foils are a future which if we keep going down the path we are, will probably succeed in getting a pretty good compromise of foiling and maximising speed, but I think at a cost whereby only the best sailors will benefit. The A Class is such a speed based machine, its the F1 equivalent.

 

The T Foil will also succeed once a broad speed foil design is produced that is designed for the boat its applicable to, but at a cost of low speed lift and lower high speed, but will benefit the majority of club sailors. As a manufacturer that's the largest market by far.

 

Perhaps far more knowledgeable people such as TSpeer would like to comment as I understand there are few of these foil designs which have a very flat lift curve.

 

Charlie, you will need a small amount flap down to begin with to get effective lift off as if you step to far to the back of the boat to get an AoA sufficient to get enough lift off your quite small foils, then you will get too much drag off the now submerged stern and not lift off. Far better to accept that you're going to be needing probably 3 -4 knots faster water speed and get a gentle lift off. Be aware that there's not much difference in total around the course VMG in that low mid range of hull speed whether you are just kissing the surface or fully up on the foil. Experiment with the amount of flap you need dependent on the conditions. You may need to talk to the UK guys as they have measured the AoA of the main foil and made a small calibration ruler which they mounted on each foil, if you know what the total range is from fully forward to back then you should be able to get a reasonable idea of what the foil is doing. Best of experimenting though.

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Wayne,

 

I have a set of custom airfoils that outperform most of the existing foil choices that are out there, including the ones Tom has drawn and release (over a decade old at this point). They have wide alpha bands and a wide drag bucket. The latter is key in any power limited situation. Exploder are aware of this fact as well, the biggest change from Z5's to Z10's was entirely in the airfoil D3 designed for their foils.

 

I weighed the decision to put Z boards into my Flyer for a long while for the same reason as you. At the same time, no major breakthroughs on the main boards have happened since the Z10, foil position is now fixed at 400mm aft of the main beam (further forward has shown to have negative impacts), the bottom exit and top exit locations are pretty fixed. Any board that comes along after Z10's will very likely have to work in this trunk or you alienate a lot of existing class members. So IMO, now is the time to cut into your boat and install boards. Without a baseline, how do you know what is better?

 

Inherently a wand based semi-automatic flapped foil can be more stable in heave than an unflapped foil.You also get high CLmax's, north of 1.5, with a flapped foil. Unflapped airfoils at 10% thick typically stall around 10° alpha with Clmax's of around 1.2-1.3 and on the board, CLmax is probably 1.0. Hence a flapped foil can have a lower takeoff speed and a higher top end speed as the foil can be sized a bit smaller as well. Z boards do have some neat characteristic as well however, in that you are on less of the board at higher speeds which makes for some interesting design decisions. I'm also of the opinion that these boards have less righting moment implications than T foils but I won't get into that.

 

Bora, +1 on your idea.

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Just to put it out there my ideal boat would basically be a superfoiler with centerline T foils one of these https://buy.garmin.com/en-US/US/p/557294, a flight controler and a couple servos. Anyone that says that a z foil boat is better behaved than a moth should think real hard about it, Scale an A cat to 11ft and it would be almost unsailable, the interia in the pitch axis makes it a bit easier.

Nobody has said anything about scaling an A to the size of a Moth. It's also all very well a world class Moth sailor saying this, but most of us live in the real world. I can foil an A on Z foils pretty well. I tried a Mach 2 Moth a while ago and have never spent so much time swimming. Somebody tried to tell me that the Moth was easier in a straight line than an A, but I am not convinced. Maybe with more practice and flat water, but I know I would need a lot more practice.

 

Having sailed both I would say a MK II is a hell of a lot easier to get stable foiling than an A in a straight line, in fact almost effortless (Other than hiking) in flattish water.

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Just to put it out there my ideal boat would basically be a superfoiler with centerline T foils one of these https://buy.garmin.com/en-US/US/p/557294, a flight controler and a couple servos. Anyone that says that a z foil boat is better behaved than a moth should think real hard about it, Scale an A cat to 11ft and it would be almost unsailable, the interia in the pitch axis makes it a bit easier.

Nobody has said anything about scaling an A to the size of a Moth. It's also all very well a world class Moth sailor saying this, but most of us live in the real world. I can foil an A on Z foils pretty well. I tried a Mach 2 Moth a while ago and have never spent so much time swimming. Somebody tried to tell me that the Moth was easier in a straight line than an A, but I am not convinced. Maybe with more practice and flat water, but I know I would need a lot more practice.

 

Having sailed both I would say a MK II is a hell of a lot easier to get stable foiling than an A in a straight line, in fact almost effortless (Other than hiking) in flattish water.

 

I didn't sail the Mach 2 in flat water. Upwind it was OK although I found the hiking hard work, but downwind was a nightmare. Then there were the tacks and gybes. I am absolutely certain that I can foil my A from the windward mark to the bottom mark easier than a Moth. I also saw a recent post on Facebook by one of the top Australian A Class sailors about him sailing a Moth and he certainly had issues. I do think that those who have had monohull experience have an advantage over us multihull sailors with foiling in general as it is more natural steering to keep the boat under the rig.

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ACS aren't you forgetting a pretty basic thing with your assessment of the Moth v A, the A you have sailed for a lot of hours, the Moth, 1 afternoon at most, or did I misinterpret your posts ?

 

My understanding is the Moth is not an easy craft to get going on at best, but those who persevere eventually get the hang of it. The A's have inherent stability ( its a Cat after all ) I would have expected it to be much easier than a Moth and from the videos I have watched, that's not yet the case, hence my questioning why we are continuing to look at Z foils and wonder if we had spent the R&D instead on T foils, what the outcome would have been. I guess we are so far down the Z foil path that we are not about to back off.

 

Interesting to see the latest vid, in the S9 thread, you can see just how much stability it has now that it has that little bit of extra sail on it.

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I am only just starting to learn to foil however I would have thought other classes are looking at the Z foils for the following reason.

 

- Ease of lauching (insert from the top, no wands to get in the way)

 

- Cheaper to produce and less maintenance (less parts, particularly moving parts)

 

- Do not have to lift boards when tacking / Gybing)

 

Every system at the moment is a compromise and none tick all the boxes however to me it looks like the Z foils are currently the most cost efficient and practical.

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Many of my concerns developed before I bought the boat (most of which I picked up on these forums) have proven to be unfounded. I have no experience on other modern foilers, but on the S9 the wands are not an issue at launch, the boards are left down, and maintenance on the moving parts is not an issue. You will spend more time maintaining your mainsheet and traveler than servicing the T foils. This discussion is interesting but there will never be a consensus. Kinda like the MaryAnn vs Ginger discussions, it boils diwn to personal preference more than right or wrong.

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Charlie

While I accept the S9 is a good boat and that T foils are a valid solution, I am still puzzled by a number of things, launching being the biggest. You posted the following

 

Well yes, any foiler is logistically more difficult than a floater - especially in shallow water - hence my trailer launching and retrieval - we are lucky to have that option here. AFAIK, everyone else uses beach wheels, which are not so good here.

You are incorrect that any foiler is logistically more difficult than a floater. Any boat with Z foils or any other insert from above foils is no different from a floater. Take everything else out and that alone is a big benefit of that type of foil. With your launch system, I note you have a big fender to stop the foil hitting the dock, which iplies launching from a dock and returning is problematic. In many situations, I launch on my own and it can be hard to get rid of the wheels and keep the boat off the shore. Surely with 2 foils sticking out this issue is even more relevant,

 

I also get concerned about the whole rigging and crowded boat park issues. I presume at some point you need to tip the hulls up to fit the T foils. From then on, don't you have 2 blades sticking out the sides? How does that work on a crowded beach with boats of other classes. There are times i have to almost fight to stop my m=boat being hit or hitting others. What happens when people don't know the foils are there?

 

How do you tackle weed with T foils? I know a number of places where weed is an issue, but I would imagine there is an issue with anything you might pick up on the foils.

 

Maybe these issues don't effect you and maybe there are things I don't get because I haven't tried the boat, but I am just trying to apply common sense. In the A Class we have discussed these issues about insert from below foils and T foils. Many have concluded that the perceived issues mean we shouldn't consider a rule change, although this has been helped by how well the boats sail now.

 

I am not suggesting that Z foils are perfect but it seems to me that there are compromises everywhere. Maybe the A's have it wrong about how practical other foil set ups actually are. I also think it is very insightful that both Nacra and Flying Phantom chose to go with removable foils for the 17 and Essential.

 

Wayne

As the point under discussion was ease of sailing, the amount of time in a particular boat isn't an issue. I know that I could let any competent sailor out on my foiling A in 12 knots and there is a very good chance they would foil OK and probably sail around and not capsize or maybe once or twice. Put the same sailor in a Moth and while I am sure they would get up foiling the chances are that they would do a lot of swimming. This is fairly irrelevant in discussing your original post, because with the cats, I am sure that the T foils are a bit easier to sail with, although I was told that the A with T foils was a real handful. which I put down to size of rig and power to weight.

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The S9 has a single bolt at the T intersection, simply put the vertical in from the top and mount the horizontal in its correct mounts from the bottom and lock it on with an Allen headed bolt, takes about 3 minutes to mount it, also allows a complete change of horizontal foil at any time if any damage occurs and future proofing it if the foil design changes. When you pick up the horizontal part its really tiny on the S9 and has minimal surface area, its cost to produce must be insignificant compared to the Z foils where the entire length has to be changed. Its quite a clever design of the T intersection as the horizontal locks in completely solid, with an auto connection to the flap control rod in the vertical and yet only held on with a 4mm bolt. The dolly wheel shields the end of the foil, but it only sticks out by 100mm or possibly less, than the hull edge.

 

ACS you surely can't be implying the Moth is less stable because of the T foil, try balancing on one foot and you may have your answer, takes a bit of practice but can be done.

 

There are solutions to all problems, we just have to be open minded about things and what can be perceived as a problem, are often not.

 

Funny enough for the larger two handed boats, where the weight transfer along the boat has less influence, there's a pretty good call for Z boards, ( or T's with flaps :) ).

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ACS: I understand you, I think. The T foil has a precision socket, board has a precision extension. Board is installed frim the top, then the T is fit and secured by a single screw. T can be fit at any time. Boat tipping a la Phantom is not required. Still more hassle than a Z but not as much as you perceive, I think. The additional hassle is as much rudders as it is boards. All foilers I am aware of have T or L rudders. These act as brakes during an onshore-wind beach launch. Boat is very reluctant to tack, if waves or big chop are present it is even worse. Pretty easy to break something back there. In my experience this went a long way in killing foilers as beach cats. ACS: again, just my observations and opinions. Not making anything up here, just describing my experiences.

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This seems like a good thread to ask this question. I recently acquired a boat suitable for experimentation and I am trying to get up to speed on foil developments. Hence, no hidden agenda or judgement in my question.

 

i keep reading that the Z foils are heave stable while all the other alphabet foils, except T, are not, but not any discussion of why. I am assuming that it is because the angled portion of the Z breaks the surface of the water. In that respect, are they simply a version (albeit a very sophisticated modern version) of the "traditional" angled surface piercing foils of the type Hydroptere uses?

 

The boat, which was a gift, is something like a 20 year old, 16 foot, miniature version of Hydroptere with some clark-Y foils. The amas are pretty clunky and I am free to experiment on whatever goes on the ends of the crossbeam. Any suggestions on where to get technical data on modern Z foils?

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You might consider using a version of an UptiP foil on each ama or an "L" foil mounted at an angle so that when immersed it works like an UptiP foil. Being used on multiple large tri's that are sailing or under development. Less draft, less inboard movement of the center of lift(compared to a Hydroptere type foil), excellent altitude control without the variation of a surface piercing foil and can be designed to require no adjustment while sailing.

 

Pix by DL

Twisted(wash-in) uptip foil on 5' Test Model:

 

y09it.jpg

 

Pix by Alexis Courcoux:

 

M24 Test Model:
wko7rt.jpg

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Doug, thanks for your suggestions, but it doesn't really address my question, and I am familiar with Tom Speer's explanation of the link between leeway and angle of attack on foils that curve upward.

 

But I prefer not to jump straight to the conclusion without understanding the analysis. My question essentially was how do Z foils provide stability.

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Wayne, I like most sailors around the world launch from a beach or shore with beach rollers. I also have waves to contend with like many..... how would you launch the T foil boat solo so as to not damage the foils or wand set up.

 

Also, to produce a flapped foil with wands and associated hardware will always be more expensive to produce. There will also be more maintenance. Maybe not straight away but as the boat ages.

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Doug, thanks for your suggestions, but it doesn't really address my question, and I am familiar with Tom Speer's explanation of the link between leeway and angle of attack on foils that curve upward.

 

But I prefer not to jump straight to the conclusion without understanding the analysis. My question essentially was how do Z foils provide stability.

 

Have you seen this-page 26 especially- but also see the very first illustration showing the Z foil loading on a NACRA17-and the contribution to heave stability from the windward and leeward foil: https://www.dropbox.com/s/x44cb22wlw5zfvb/Meeting%20Presentation.pdf?dl=0

One thing that may not be clear is that a tri can be designed to effectively use uptip foils w/o the hassle of having to lift/deploy foils with every tack or gybe.

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Doug, thanks for your suggestions, but it doesn't really address my question, and I am familiar with Tom Speer's explanation of the link between leeway and angle of attack on foils that curve upward.

 

But I prefer not to jump straight to the conclusion without understanding the analysis. My question essentially was how do Z foils provide stability.

 

Have you seen this-page 26 especially- but also see the very first illustration showing the Z foil loading on a NACRA17-and the contribution to heave stability from the windward and leeward foil: https://www.dropbox.com/s/x44cb22wlw5zfvb/Meeting%20Presentation.pdf?dl=0

One thing that may not be clear is that a tri can be designed to effectively use uptip foils w/o the hassle of having to lift/deploy foils with every tack or gybe.

 

As usual, Doug doesn't answer the question.

 

Z foils work because the faster you go, the more lift is produced and the boat rises, which reduces the amount of foil in the water which reduces the amount of lift available. Design it right and it becomes self stabilising. This can also be adjusted by changing the fore and aft rake of the boards, which widens the speed range that the foils can work in because it changes the angle of attack of the lifting parts. Although a separate issue, you need to balance the amount of lift from the rudder foils with the Z foils. The more lift you get from the rudders, the more lift you need from the Z foils and the higher you will foil, which is good because less foil in the water equals more speed. the downside is that it also equals more instability as there is less foil in the water. It's also more difficult to foil at slower speeds because with all the foils low in the water, you get more drag. I hope all f this makes sense.

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A lot of development these years, so its not obvoius whether z's or t's (or some other letter) are (or will) best.

 

Z's has the advantage of better RM, hardly any lift on the windward board - where t's has equal lift from both. T's seems more selfstabilizing, a least when looking a good moth-sailors.

 

And sailing with z's can be very stable as well -> https://www.facebook.com/paolo.penco/videos/1416077275081882/

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Lars, I'd say that wand based foils are the most stable in roll because they actively change the amount of lift from each foil automatically whereas Z foils are passive and work like surface piecing foils.

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I think one reason T's in cat's, beyond the above launch/retrieval hassle, were ditched is the performance of Off Yer Rocker. At this point a 10 year old design and I'm sure they would do things differently today, but in almost all sailboat classes we are drag limited, and they found the big T's + wands soo draggy in light air that it was better to cut them off entirely! Carrying around two t foils + wands is inherently more draggy than a pair of Z or L/J style boards, on average for the same foil area. T foils are certainly more stable but that performance comes at the cost of top end speed, no one is saying a S9 or Whisper are faster around the course than a Z board equipped boat, more stable yes but not faster! Certainly in either case the rudder foils are a factor as well, but its easy to fully retract a Z-board when going downwind in light air on an A or Nacra 17/Phantom Essential. On a T foiler you'd be carrying around the extra drag of that foil no matter how much you retract the vertical.

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Sam, don't you think the foil area for the same lift will be greater for a Z than for a T foil ? The lifting element of the Z is at a big angle compared to the horizontal lifting element of a T foil.

And the speed shown by the S9 and to some extent Whisper is pretty good. The Vampire takes a wand controlled T foil to another level, canting the leeward t-foil and retracting the windward foil. They seem to do real well.

The biggest problem with an uncanted T-foil is high and low pressure on the same side-draggy according to Greg Ketterman and others.

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For cats and T-foils, I give credit to the UFO for putting Ts in the right place on a multihull. http://www.fulcrumspeedworks.com/UFO/

 

Beach launch, check.

Weed clearing, mostly.

Safe in moving about on the beach or boat park without foils sticking outside max beam, check.

Uses a T-foil the way it should be (like a moth), check.

Makes foiling easier by not having to the use the trapeze, check.

 

I do not think it is an easy retrofit option.

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You're 100% right about some multihulls........Maserati had a T-foil on the daggerboard at about the same time the UFO was introduced. A daggerboard T-foil on a tri is the best trimaran foil configuration out there when used in combination with foils that work like uptip foils on each ama(used one at a time) with rudder t-foils.

 

PS there is a "beachcat" in Australia-the Arrow-with a T-foil in the center like the UFO.....

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You're 100% right about some multihulls........Maserati had a T-foil on the daggerboard at about the same time the UFO was introduced. A daggerboard T-foil on a tri is the best trimaran foil configuration out there when used in combination with foils that work like uptip foils on each ama(used one at a time) with rudder t-foils.

 

PS there is a "beachcat" in Australia-the Arrow-with a T-foil in the center like the UFO.....

Be careful what you read on the Internet Doug. The story you reference is three and a half years old and I'm very familiar with the boat and the person who modified it. It was a very brief attempt and it was quite unstable. Certainly incapable of getting around a course effectively. It was quickly returned to standard floating configuration and sold. The owner now sails a trailer sailer - non-foiling.

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I just remembered the story and given the comments that have been made I figured it was, at least, worth a look. At the time there was some discussion of the guy not using a rudder T-foil or two-do you know the facts?

 

http://www.catsailingnews.com/2014/01/foiling-for-all-budgets.html#more

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samc99us: FYI: on the S9 the wands are held up out of the water by a lightweight hook while launching, retrieving, and light air sailing. No drag. Zero.

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Interesting conversation, and I will make no value judgment on the comparison, as I do not sail cats and have no experience with anything but T foils.

 

But I think everyone has missed the major advantage of the T foil and that is the benefits from windward heal. With foils big enough for take off there is always excess lift once airborne and sailing at increased speed. Raising the flap reduces some lift but there is always extra. By healing to windward some of this lift is diverted to lateral resistance. On the moth, at about 20deg this means that the centreboard or strut no longer makes any contribution to lateral resistance and hence is flying through the water at zero angle of attack and hence minimum drag. The drag reduction is very noticeable. Sailing a moth upright is just very slow, especially upwind.

 

Whether the T foil is on the centre line or under the leeward hull, healing a cat to windward 20deg becomes a problem when the windward hull starts to drag on waves. The UFO is quite narrow so it works, wider cats will always have a problem. Keeping the T foils upright will result in extra drag, excess lift and will not perform like a moth does.

 

The Cat style Z foil align the leeward hull lifting section of foil at an angle not dissimilar to the moth style 20degs. Its unloading the vertical from most of its lateral resistance loads, so its working a bit the same way. But only if the windward foil is close to flying at zero lift. The 2 handed cats of course are doing this by raising the boards, but the fast people in ACats must be getting it right by careful tuning of AoA and toe in. Thats why the good guys are so much better than the people who have just boats a set of foils and stuck them into a boat and expected everything to be fine. Its obviously a fine science and only a small number of people seem to understand what to do.

 

When we sailed at the same regatta last November, only two of the ACats seemed to be flying effectively upwind and downwind compared to all 25 of the moth fleet. Still a long way to go I think. But its worth it for the rides.

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Good analysis Phil.

Earlier in this thread the difference in development time between A's and Moths was dismissed as not all that significant. There is around 7 years difference and equipment and techniques move quite quickly. Last weekend I sailed a regatta where amongst others, two Z10 equipped A's sailed against a J board boat. All are good sailors and been foiling a fair while. It was chalk and cheese. The Z10's lifted much earlier and were very stable around the course including to windward. The J lifted about 3 knots later and was far less stable and didn't lift to windward. There is only about two and a half years between the introduction of each board. I think the Moth is at a much more advanced stage than the A in overall development. The future is certainly exciting.

Another interesting observation was an A sailor who has little foiling experience and hasn't sailed for 18 months jumped on one of the Z10 boats for the last day. He was able to foil stabily straight away because the boat is very well set up. He was slow in the transitions but quick in a straight line. We're getting there😀

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OK so in the ultimate quest for a simple and cheap singlehanded foiler, what about a scow moth with Z boards offset all the way to the sheerline and single centerline moth rudder ?

how would that work ?

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Wrong thread but quick moth answer:

Moth foils must not cut the water surface outside the static waterline (monohull rule)

Makes them too close together if Zs are turned inboard ACat style.

Potential though to turn boards out like French offshore monos, and still be inside OA beam and might be safe if under the wings. Not tried yet AFIK.

Twin T foils have been tried by Jim French and Ian Ward but I see they have now switched to a single T foil on the CL.

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Brett Burvill's (Windrush Catamarans) Moth. Not sure how it handled though.

 

IMG_9484_zps9jmluapc.png

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I wish the A Class hadn't settled for Rule 8 which was initially intended to prevent foiling. Now that the leading sailors and builders have established themselves with this solution, they will never go for another vision, which may lead to a better result. Such is the nature of sailboat classes. I continue to believe that there are better configurations that have not been explored. I may take the last DK17 and modify it out of class to do more experimentation on a smaller and more achievable scale.

With regard to the practical one man foiler, I think the UFO ticks all the boxes. Floats like a multihull, flies like a Moth. Cheap too.

SHC

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Steve, there is DK in my back yard too, and I've been thinking about cool things to try. Would love to hear your ideas.

 

I agree on the UFO. Seems to do a lot right, and at the right price. I wouldn't be surprised if it costs a ready-to-sail UFO just to fully convert an F16 or F18 to foiling with any current technology.

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Burville moth yr 2000, Sydney 18 about same time, Hydroptere, all much the same as James Grogono did in the 1970s. Not go well upwind.

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Wasn't Burvill's Moth the first foiler to win a race(or two?)* at a Moth World Championship?

 

 

*Brett Burvill sailed a narrow skiff Moth with inclined surface-piercing hydrofoils to a race win at the Moth World Championships in 2001 in Australia, which was the first time a hydrofoil Moth had won a race at a World Championship.

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Twin T foils have been tried by Jim French and Ian Ward but I see they have now switched to a single T foil on the CL.

I happened to be out sailing my moth near BYRA last year on a perfect foiling day gusting 8 to 12+ knots and dead flat water when they were testing the twin inclined T scow moth. we lined up a few times for a comparison and it is no exaggeration to say that I was twice as fast. Very stable, but but just didn't light up. Though to be fair not only would my MK2 be a lot lighter so was I. I saw them out with single T scows last weekend, so looks like the twin T experiment is over.

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Burville won a couple of WC races in Perth, yr 2000, when the wind turned the course into reaches. Boat is now in WA maritime museum. Class refined its rules and banned wing mounted foils shortly afterwards.

 

Jim and David French sailed their twin T foil scows in Perth 2016. There is a photo posted with me in the background behind David, I had rounded the windward mark the second time just after he rounded it the first time. Leaders were long gone. Typical of most races. Upwind they were same speed as low riding scow, downwind about 1/2 to 2/3 skiff speed, but slower in the corners and take offs. Recent FB postings show the boats fitted with centreline T foils like the skiffs.

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With all the chatter on moths v A's it's sort of logical to think that Cats will diverge onto Z foils and the monos the T's ( Burvilles twin foils were not T's ) through mainly class requirements rather than true foil development.

 

I do wonder if the small Tri's such as the F101may well run off with the eventual crown of ease of sailing and be equal in speed to the A's. They do have the thing that the other classes don't, they are new kids on the block and have no class rules and thus can learn from the developments and foibles of the others. So often it's the 2nd generations that are the winners.

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I think small tri's 12-20' will eventually be renowned for their ease of handling, light wind foiling and rough water foiling capability. And doing this with a single wand (or manually)controlled main foil, rudder T foil and two uptip ama foils (used one at a time). It's the perfect trimaran configuration,in my opinion, and allows the full benefits of the trimaran configuration to be used-especially on an oversquare platform. Just a matter of time. No Z foils.

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