The following quote from See How It Flies, 6.1.2 affirms that the tail's lift is not necessarily downwards:

Tim,

They don't.

Curved foils are used in trimarans instead of straight ones for practical reasons only. They enable docking with the boards in any position and can be "hoisted", unlike the straight ones.

Curved wings in planes/gliders are similar to dihedral, they generate slip-roll coupling. As far as I know, slip-roll coupling presents designers with a dilemma: it increases roll-wise stability, but decreases (Dutch) roll damping.

Take a look at See How It Flies, 9.1 and 10.6.1 for more details about dihedral and slip-roll couple.

Rgrds,

Must be so tough going through life and dealing with idiots everywhere. Everyone being wrong/incorrect/stupid all the time. How do you do it? And more the case, who appointed you?

Is Wouter the messiah or just a very naughty boy?

without being racist the mix of dutch and engineer spell for a very naught boy.....at the ned of the day we are all wrong & only one person is right? Right.!

Give them a few more months and 90% of them will quietly disappear into the background, never to be heard off again.


Wouter [/quote]

do us all a favour and become an honorary life member of that 90%.

Last year on the int. A Class site there was a provisional rule on the hydrofoil subject which allowed for daggerboards to be bent or angled to the extent that the distance between tips of the daggerboards when fully down may not be less than 1.5 meters. I have since then not found any further mention of it, I am not sure if this is still current or not. If it is there cannot have been too much fuss about the bent boards.

Daniel

Does not sound like a class that is "Scared shitless of any REAL development."

Wouter, you are a very angry man. I find it amusing that someone with little real life competitive racing experience thinks he knows better than seasoned racers and then continues to tell them all what they are doing wrong and how they should be sailing their boats / running their class.

No wonder why many people look down at the F16 class with you being the Internet ambassador for them. Please do us a favour and STFU as I am eagerly awaiting to join the F16 class (or A Class) and would not like to see you tarnish the classes image even further.

Jake,




If indeed I'm angry then I'm not angry at the A-class, but rather at a sizeable portion of its sailors who at some instances celebrate the open, cool, development nature of the A-class, but when a new thing is tried become hysterical and almost immediately start throwing about "obsolete old design" and "kill off the class if not banned" kind of statements.

Most of them also reason along lines that are far less certain then they feel is the case. Hence my carbon mast example. Even if a given project results in significant jump in performance (carbon mast ?) then it is still not a given that this will impact negatively on a class (the A's in the 90's). This while many simply believe this to be something akin to a law of nature. Another example are the foiling moth, a obsolete making jump in performance if there ever was one, but the moths actually grew spectaculary internationally because of it. In deed such a development can also have very positive effects for a class. Interesting enough, there are quite a few examples of that, Upgrading the Tornado with a spi and double trapeze is another example. Still, these example are suddenly and completely forgotten whenever a new development is introduced.

Personally, I think the "raison d'etre" of the A-class is indeed development. Without it is will fall back to just a single sail solo sailor class that in time will be surpassed by other faster classes who do allow development. That is why I have so little patience with scared sailors in the A-class. If ever they get the upper hand and lock the A into a given setup by adding more rules and banning real development then they will have struck the biggest blow to the A-class in its 40 year existance. And we'll all loose an important part of the catamaran scene.

Wouter

How about you name those A class sailors. Not someone on the internet that wishes to talk about the A class, but the active racers.

Thanks for that Hans. Wasn't sure which Dutch sailor it was, and wasn't go to pick random names. Remember that in Sweden wasn't too much concern about the boards PJ used.

The results of the "hysterical" boat from the Euros:
32: Bob Baier (Allemagne) 190 points (Détail courses : 53,1,D+SC,DNS ,2,1,36,22,DNC ,)

Crazy coincidence it is a similar end placing to the wing in Florida, but there were more boats there.

The wind/wave conditions of the 1, 2 and 1, were they any different from the 53, 36 and 22? And training of course makes a huge difference.

But does someone have details on the hydrofoil committee results of a few years back? They set this 1.5m separation between the boards and should have discussed banana boards. This will stop Wouter's (and others) alarmist tendencies that seem to frequent internet forums.

So Wouter.... How about the 18 Skiff. Should they have brought in the OD hull and increase in class rules or should they have remained a very open development class.

Are the Foiling Moths seeing greater numbers racing then they did when Moths were sea-huging Skiff Moths or even Scow Moths?

Did the A Class make a mistake by introducing a min weight.

Better to race in a healthy fleet then be a one off racing on handicap with others.

The A Class have not rushed into any decision, but will look at it carefully. If it does look like the bannana boards will have a large advantage, obsoleting all other boats in the class.... Do you think it will be healthy to allow it to happen. Would see a lot of sailors turn away from the class.

Just as a tangent.

I'm not in any way or form an official or ambassador for the F16 class. I'm my own man and my statements can only reflect back on my person and not some class that some may want to tarnish for unrelated personal reasons.

Additionally, I don't THINK that I know better, I KNOW that I know better. And the usual people frustrated at my persona will find out soon enough that once again the comments I've made are alot closer to the truth then theirs. And last time I checked you were still not a world class or seasoned sailor yourself Stephen. You are just an amateur like the rest of use. But even if you were Glenn Ashby and stating publically on this forum something that is verifiably untrue then I would still have no inhibitions to write that down in public.

Interesting thing of course is that guys like Ashby never seem to make such untrue or dumb statements. They know the limits of their expertise in contrast to sailors much lower on the food chain like yourself.

Sorry mate.

The only way to go about it. This decision should be made by the sailors...... Not people on the interweb that think it would be cool to see what happens, with no regard to those with a financial interest in the class.

Why on earth is anything to do with foiling "real development"? and everything else insignificant. As you say, the class has been around for more than 40 years, how many quantum leaps are you still hoping for? You have to look hard to see the difference on F1 cars, but they get faster every year. The A cat has evolved substantially over the last 5 years and has got quicker still.

Looking at it practicaly, its one thing talking about a 25 kg Moth that can be carried into the water with its foils by one person and a totally different matter rigging and launching an A cat in some breeze with meter long foils attached. The days of going sailing without assistance would be over, that has nothing to do with being scared. If foils were allowed, I would not convert, the ballache factor is way to big.

Me thinks, the last C Class event was not a terribly good advert or inspiration for ordering foils for my A, it was facinating and respect to the gentleman involved for not spamming up the internet with theory and actually trying it. Pictures of anglegrinders cutting off foils have scarred me for life.

Daniel

Moths is a no brainer dude. Gone from 30 at the Worlds a decade back and the same people each time, to possibly 80+ in Weymouth next week. To get a new Prowler is a 12 month waiting list, and Bladerider is prob 4 to 6 months. And the other manufacturers are similar. But the moths went from being possible footnote in history to one of the most popular things happening in sailing.

A-Cats on the other hand had one of their most successful worlds outside of Europe with 98 boats.

But the old skiff moths can be retrofitted with foils rather easily.

For the A, rebuilding a centreboard case (and possibly moving to another part of the hull) is a different story. Does the boat have the structure to take loads in an area not previously designed for it? And development of boards would start in earnest.

The condition in the race not sailed well by Bob where diffferent from the races he did good but he had also some luck to make the right side of the course. When i did see Steven go around the first mark as 40 and see him finishing as 3th with a standard type boat then what was better the curved board or the straight boards. I think the skill of the sailor did the most and making the right choices on the difficult course with wind going around the place was more critical then the boat or boards used.
The fact that Bob did good in a few races made everybody nervous and because he was using something else was firing up this. The other Nikita's did have also curved boards and did sail on the place the skipper should be in that type of conditions and when the trick should work then they should be further in front then the real did.
So every body is seeing ghosts is my opinion.

Cheers,
Hans Klok

Ahh finally some factual argumentation (when in only part of your post anyway)




I'm convinced that if the banana boards are proven to have a "large" advantage that the A-class should adopt this feature fully. I don't think the old boats are made obsolete that easily and if they are then I also don't believe this to be a major issue for the class. Mostly because local fleets will transition much slower then the top of the fleet who are changing boats very often anyway. Also a curved daggerboard trunck is quite an acceptable modification to any older A-cat. It is on a par with upgrading to a new design mainsail in cost. And nobody when ballistic over that either. And again, I think such a step to be comparable to the carbon mast introduction that obviously did not kill the class or prevent it from growing internationally.

I think the core of the class is the active racers at the top. Keep those on boards and the recreational sailors will follow anyway despite pretty vocal declarations to the contrary. I refer to the Tornado upgrades as a prime example of that. 2/3rd voted the changes down but 2 years later over 2/3 ofd the fleet had changed to the new voted down setup anyway, with the class now just as strong as before.

I truly and honestly believe that the core of the A-class is largely unregulated development. Without it the class would have died as a 100 kg alu masted single sail singlehander years ago. Another class like the inter-17 or F16 would have replaced within 1 or 2 years of its introduction. And that has nothing to do with either the inter-17 or F16 class and all with the inability of such an A-cat class to remain exiting in a scene where other classes progress to new levels of performance and attractiveness.

In fact, I will even be a large supporter of allowing curved boards in other classes like the F18's and F16's once the design has stabilized. In a similar way the square tops replaced the old pinheads.

As an engineer however I don't see curved boards to be able to result in a "large" performance gain. There is not enough percentage associated with the hulls in the old-fashioned setup to justify such an improvement. Of course the drag related to the (straight) daggerboards remains as this is closely linked to the sail force of the rig that isn't changing in any significant way.

I classify the curved daggerboards much more as a refinement then a breakthrough. This because its effects are far more in the field of damping the boats movements then lowering the overall drag. I also feel the latter is already partly adressed by inward canted straight boards. (whatever happened to outward canted boards guys, the hot and exiting development of a few years back ?) And there are some conflicting design problems that are not obvious at first glance. One of those is that simply curving inwards the boards doesn't do that much to lift the boat when the foils are symmetric. In the way of damping movement they will be effective that way. In order to create meaningful lift (in this case, enough of it to matter) assymmetric profiles are needed or a permanent angle of attack of say 4 degrees. At low speeds or when having two boards down these characteristics are actually a disadvantage. That is why patient lady C-class design, raised one baords and lowered the other after each tack. Patient lady is one of the very few examples of a sufficiently succesful implementation of curved daggerboards as a performance enhancing item.

I think I have answered all your questions.

Wouter

Based on what.... your extensive competitive racing experience or “because I am an engineer and you are not”



Don’t pretend to be top International..... Not even close. I am only an amature, but a seasoned racer who has raced extensively at a National, State and local regatta level, along with 2 World Championships and other International events. At the top level, I am mid fleet...... But still a seasoned racer.

I am not some wannabe that avoids racing regattas and in quality fleets.

My sailing experience would run rings around yours and there are plenty of people here that are better sailors than me that you presume to know more than.

Just look at the bloody numbers mate !

Get beyond the "gutt feeling" side of "engineering" and look at the data and models already available.

And pick the needle off the "extensive competitive racing experience" broken record. Having the skills to make a boat go fast on the water is not the same as having the skills to design a fast boat.

But I'm not even adressing the more difficult engineering aspects here, we are still stuck in the obvious rookie mistakes. My small nephew even understands without a formal engineering education that when a hull represents only 20% of the total sailboat drag that a 25% lifted hull (due to partial foiling) can never result in more speed gain then 2.5%. And that is when given optimal conditions for foiling. By the way 25% lift on an A-cat equates to about 40 kg of created vertical lift which is alot for a curved foil as used currently. A straight bruce foil will need to be angled to 22 degrees to match that given the close link of vertical lift to the given sideways resistance to sailforces. There is a pretty tight interaction there.

2.5% is about a minute per 45 minute race. Of interest to the absolute top of the international A-cat fleet but pretty unimportant for 85% of all others. Of course in not optimal conditions the setup may well be a drawback making a sailor actually slower then its competition. Curved foils will most definately show such a characteristic with the obvious drawback zone being low hull speeds (light winds)

You don't have to be a Glenn Ashby to understand this.

Wouter