Moth on Foils: 35.9 knots(41.29 mph)

Moth on Foils-no wand

I'm still convinced that eliminating the wand 100% would be fast though harder to master. They've sailed the 26' Mirabaud with manual control-last year-as well as the first two person bi-foiler-David Luggs I-14 in 1999. Somebody is bound to try it on a Moth-using the tiller twist grip to control the main foil instead of the rear foil. Many Mothies say that the rudder foil angle is rarely adjusted anyway and provision could be made for adjusting the rudder as well.
I've tried it on my boat and though I had problems due to installation mistakes I'm still convinced it will work and increase speed and reduce crashes(after it is mastered). I think a mixible set up that allows the mainfoil to be controlled by the twist grip while also controlling the rudder foil from 0% to some higher figure could also work.

 

Doug:

You've been posting this very idea for a few years now without convincing anyone who foils to try it. Why don't you prototype one and post a request here and on Sailing Anarchy to use it and do trials?

Ideas that never reach testing are pointless wastes of time and bandwidth. Since you are convinced (and have not convinced anyone else), it is time to take the bull by the horns and make all the people who doubt this concept become believers. Given your faith in the concept, investing a little of your time and money will be worthwhile.

I'm comfortable enough it ask Bora Gulari (and others) to test your concept once you've got it ready to attach to a Moth - I'm certain he will give it a very thorough review. I'll even post a blog on the testing and publish results for you.

Le us know what you need in terms of requirements to get this idea off the back burner, otherwise you should probably let it die.

--
Bill

 

Well, its been tested on several different boats ,as I said before-the most recent being last year on Mirabaud, the worlds largest bi-foiler. It works. Somebody in the Moth class sooner or later will do something with it. I'm using it on my new boat-I have no interest in trying it on a Moth but I can help anyone that wants to with the collected wisdom of those that have tried it including David Lugg, Alan Smith, Thomas Jundt and myself. Technically ,it can be a very simple setup-much simpler than a Moth wand. With a small amount of greater complication the mixable version can be tried-probably far superior to just manual control of the main foil- but this version hasn't been tested yet. I'll help anyone interested in trying it to understand the setup possibilities-that would be great. The problem that will come up is the will of the person that tries it because it will take lots of practice to master to a race winning level.

 

It has been "tried", but not successfully in the "faster than the alternatives" sense. If you measure success as "trying" than I guess it has been tested. The "tries" done to date have been in one-off boats with no control group or comparison to a baseline. How can anyone conclude anything?

Testing to me means something very different: posting a hypothesis, developing a test plan, generating a broad range of data points across all usual conditions and then comparing results to a control data set established from the established state of the art. Once you have both representative data and a control data set you are then equipped to draw some conclusions regarding the results. Subsequent peer review post publication will provide credibility.

By my standard there has been no testing to date, and no conclusions can be reached. My suggestion to you was to start the ball rolling on actually trying and measuring results to reach some conclusion whether or not this is a valid idea. My suggestion of the Moth class is that there is more than one, so measurement and comparison is possible.

Perhaps my education and thirty years work experience are getting the way here and I should accept things on faith. There is a Zen-like quality to your pronouncements .... "sooner or later" someone will test your theory in a Moth and prove it correct. My bad.

--
Bill

 

Here's how I have approached a manual control system....(PS-I started with a lot of experience with wand control systems)
=========================
There are two major elements of testing a manual control system: (three for racing)
1) developing the mechanical system so that altitude can be controlled
a. deciding on a method for the application of force to the twistgrip and
the design of the twist grip
b. deciding on a protocol for which way the twist grip should rotate
for "up and down"
c. designing the extension tiller system so the rotation is the same on
both tacks,
d. designing a system to transmit the force developed at the twist grip to
the flap of the main foil
e. test sailing the system to determine and fix weak points such as
any "play" in the system. Determine how well the system works in
tacking and gybing and making corrections as necessary-is a "drag"
that can be turned on and off required? Is the rotation protocol right-
does it reflect most peoples intuition as to which way the twist grip
should be turned? Can it easily be reversed?
2) Rigourous test sailing until the altitude control system is second nature.
3) In a racing application, this is the point that two identical boats should
be tested one with the wand and one with the manual system.
===================
I'm at e. above-again- having had trouble at e. during the first tests and then having to redesign the system at d. above.
It should be noted that manual control ,even with the problems I had originally ,is a lot of fun and a system like this may interest people who are not into racing as well.
--
my original twist grip:

 

So, you are really suggesting that recreational sailors would just love to have an enormously more involved learning curve before they can begin to enjoy their expensive boat?

Tip O' The Day

People who only use their Moths for purely recreational purposes are not going to seek out a control system that is harder to learn and fraught with unlimited crashing. These folks want it as painless as possible, with the highest level of enjoyment for each hour spent on the water. Long learning curves do not fall within that paradigm.

 

I do not believe that the tiny drag reduction from eliminating the wand makes sense given the challenge and learning curve implicit in the use of manual control. The existence of dual wands rather supports my opinion. It's down in the noise, second or third order stuff, etc., etc.

A wand-controlled foil is an example of a feedback control mechanism. The following is a simplistic look at control issues for those who are interested and don't already have familiarity with the subject; I apologise to the cognizant but I don't know the degree of familiarity with this subject in the boating world:

The simplest form of feedback control mechanism is the on-off control of a basic domestic hot-air heating system. Such simple systems easily become unstable, the heating system works because the air limits feedback gain and the thermal mass of furniture and walls act as a low-pass filter. Heating systems that heat the house structure more directly such as under-floor heaters either respond slowly which prevents instability (domestic) or have more sophisticated control methods (fast-responding industrial).

More sophisticated servo systems use PID (Proportional-Integral-Differential) control in which the sensor signal is subjected to simple scaling, integration and differentiation with respect to time, these 3 results being summed to form the feedback signal.

The proportional feedback loop is usually the major factor and describes a wand-controlled foil. Such systems tend to have either instability or poor sensitivity and slow response speed. The introduction of a differential feedback loop improves response speed or short-term accuracy, and the introduction of an integral feedback loop improves long-term accuracy. They allow proportional gain to be reduced for improved stability. In addition to the gain adjustment in each of these loops, it is usually found necessary to impose a limit on the magnitude of the feedback to prevent oscillation. Other feedback elements are introduced in typical mechanisms to compensate for such things as backlash but they need not concern us.

Some or all of these features will be present in an automatic steering system. Looking at the wand-controlled foil in servo terms, the proportional gain is obviously a function of the wand-to-foil linkage system. Positioning the wand forward of the foil introduces an element of prediction into the feedback signal and is analogous to the differential feedback loop; note that in a servo system the introduction of a differential loop would typically be accompanied by a reduction in proportional gain. Limiting the feedback magnitude obviously translates to motion stops at the end of the foil tab range.

If I wer to design a dual-wand system, I would locate the wands in tandem, with feedback from the wands being combined and applied to a single foil. I would provide for easy adjustment of the linkage to allow me to optimize the proportional (aft wand) and differential (forward wand) feedback gain.

I am not sure how an integral feedback loop could be accomplished, but if this were a servo system that I was tuning then reducing proportional gain and increasing integral gain would be the first thing I would try. Perhaps manual control input would be suitable for long-term height control.

I don't know if this helps add a measure of predictability to wand systems. It may of course be terribly old hat.

 

Gulari wins Rolex Yachtsman of the Year

Congratulations ,Bora....

Rolex Yachtsman of the Year – Bora Gulari (Detroit, Mich.) has been named US SAILING’s 2009 Rolex Yachtsman of the Year, earning the coveted award with his very first appearance on the shortlist of nominees. Gulari had tough competition for the honor: all but one of the 10 male nominees, Gulari included, had won a world championship title. Ultimately, 10 of the 14 panel members gave Gulari their first-place vote, acknowledging his growth from square one in the Moth class two years ago to winner of the CST Composites International Moth World Championship in 2009 as nothing short of remarkable. Although many sailors compete for years in a class before making it to the elite level, Gulari won his first Moth world championship his second time out and became the first American in 33 years to claim the class’ world title. One of the panel members witnessed the first two days of competition at the worlds and attested to the high level of talent in the Moth class, while another panelist felt that the sport was witnessing a watershed moment in terms of the class taking off in the U.S. In existence since 1929, the Moth is a development class with a design rule that has remained basically unchanged, while the craft has gone from a home-built, flat-bottomed skiff to the current version incorporating hydrofoils on which the craft flies across the water.

“I just do this because I love it, and I think this year was the start of great things to come for dinghy sailing in the U.S.,” said Gulari. “With the addition of the foils, the Moths became easier to sail and a lot more rewarding. . . generating a level of excitement for sailing in some of the top sailors in the country that I have not seen before. I don’t think it will take people away from traditional dinghy classes, but the Moth is so fun that it's attracting people that have never had any interest in dinghies, and its bringing people back to dinghies who thought they were done getting wet.”

 

" ... since 1929, the Moth is a development class with a design rule that has remained basically unchanged ... "

Was that remarkable foresight by a gifted panel or just incredible luck? Whatever it was, it gets my vote for best illustration of the value of simplicity and consistency.




" ... With the addition of the foils, the Moths became easier to sail ... "

I'm speechless; how often does that happen?

 

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

Why, yes...Before John Iletts wand controlled bi-foiler(1999) the Moths' hull beam had shrunk to its current approximately 1'+ . The way the boat responds on foils is like a boat with the beam of the main foil according to several Mothies I've talked to. I noticed that on my boat the thing was much more steady in roll on the foils.
----------
Comments by Ian Ward(2004!) from a slightly different version of this paper published on foils .org-Basically, the same words and meaning:

http://www.moth.asn.au/reports/foilers_may_2004.html

a) Stability: sailing on foils is easier than it looks, being more stable than existing Moths without foils. There is considerable dynamic stability generated by a foil around 800mm(31.5") wide as opposed to a 300mm( 11.8")
wide displacement hull.

 

Good post AK.

Don't let the minor diverson that has since followed put this thread off a useful course.

 

========================
Just heard from Thomas Jundt: they are rigging manual altitude control(for 2010) to bypass the wand for heavy conditions.The new system will allow main foil flap control from each wing(rack). He says that manual control is superior in big waves and heavy wind-as compared to a wand or wands. Something I suggested it would be a long time ago.

 

Congratulations Doug! You are one smart cookie! I'm impressed!

Since this is a Moth thread, I was a little surprised you felt the need to congratulate yourself regarding Mirabaud developments, so I'm going to help you with your self esteem issues and let the thread get back to Moth speed issues.

Mad props! You da man!

--
Bill

 

Hello Pat... meet Back. You two should get along famously.


In a rare moment of objectivity, Doug, perhaps you could also offer-up the list of, er... your "suggestions", that have never seen the light of day and never will?

 

Moth on Foils-manual altitude control

Check out Thomas Jundts complete e-mail regarding manual altitude control on Mirabaud here:
http://www.boatdesign.net/forums/sailboats/foiler-design-2447-58.html#post331448