Moth on Foils: 35.9 knots(41.29 mph)

Missed the Point

Hi Rick,

I've said this before, several times in fact, on various iterations of this over-arching discussion on foiling stuff; "I think the concept of a foil equipped boat is interesting and as a sailing craft they look to be decent fun. I do not think they are destined to be a replacement for the venerable, and apparently timeless, Hobie 16 by any stretch."

What my beef is now and will continue to be, as long as the hyperbole is spewing forth from the source, is this: Mr. Lord has taken the rather liberal opportunity to promote his potential commercial venture of a, so-called People's Foiler, under the guise of the now defunct aeroSKIFF project. As a development project, I had not one wit of an issue with his efforts, although the boat had about two tons of hype and one pound of delivery. The issue came about when it turned from development test bed to commercial product.

It would seem to me that if you are going to pound your message into the face of a bunch of educated, and experienced sailors who have everything from serious design backgrounds to extensive marketing experience, you better have your ducks in a row, or drop back and punt, so that you don't waste everyone's time.

Unfortunately, that has not been done and the proof is ultimately in the fact that the boat in question languished untouched and has been pushed off onto another party without any of the foily bits included in the package. The aeroSKIFF is functionally dead in the water.

Since there is no visual proof through competent stills or video of the performance claims of said prototype, it's been left to our belief system, as has been established by Doug's demeanor and overall hype-driven tendencies to gloss-off about stuff not in existence.

Don't bring commercial trade presentations to the Boatdesign pages unless it's formally asked about. When you do, have the decency to make your pitch in a minimal fashion and then direct the discussion off-list where folks can freely ask what they wish. Certainly, that shouldn't be too hard to adjust to.

Don't voluntarily put your stuff in front of a bunch of really sharp and well-spoken guys who give you their opinion and then find yourself espousing anger when they fail to see the "magic" of your vision. That's especially true when the audience doesn't agree with your interpretation.

When you get negative criticisms, don't fire-off retorts that are filled with vitriol and hostility unless you expect to be met with same in return.

Lastly... don't relentlessly pound away at the same old tired horse of buzz hype without recognizing that you are eventually going to get thumped in return; if only because we don't want to hear it anymore.

The public perspective is a tough piece of ground. Folks with thin skin have no business stepping into the harsh and unrelenting light of the public eye unless they're prepared to deal with the vast gamut of what can potentially come their way.

I don't know how involved you are in your work, Rick, with the commissioning client and their incessant desire to have substantive proofs delivered for their cold cash, but the public works in that same way and then some. If Mr. Lord thinks that he's not going to get grilled by industry publications, working professionals, concerned fathers of prospective buyers, tire kickers, in a fashion mor potent than he ever got on these pages, he's already way over his head in the product presentation game.

Perhaps you hold a different opinion.

I've taken my concept boats to various trade shows around the country over the years and I've heard all sorts of interesting comments. There are three types of people, basically, and it goes something like this at one of these boat shows: One group thinks you've just about ruined the sport with your "thing" and they'll tell you so in pretty damn harsh ways. Another group thinks you are like a God of some sort for creating the next coolest cheeseburger afloat. The last group has serious observations, pointed questions, unrelenting stares and a curiosity to see how you handle the pressure. Toss out the first two groups from the extreme ends of the bell curve and learn how to field the tough questions with a smile on your face and a sincerity that will allow you to learn from their comments and questions. That process doesn't seem to have happened in this case.

My suggestion to Doug, (and this has been made time and time again) is to go off to the shop, work his butt off to produce what he thinks is a viable, innovative product, test said product to failure and discover (and fix) what is wrong until he's sick of looking at the damn thing. Then... and only then, start showing it around and allowing it to produce a little grass roots viability before he steps, once again, into the big world. This is what was done by Ilett and all the others who tread this ground before.

I don't think this will happen, because I think Doug likes the WoW factor of gloss dumping on the Boatdesign site more than the work involved to deliver a solid product. Since Doug joined this site in Aug 2003 to share boat stuff, he's posted 1,422 times on various subjects. I joined the list one year later and now have posted 178 times. And I think I spend too much time here away from my prototype development shop. Speaks for itself, doesn't it?

I know that you understand the work thing of getting a product to full fruition. You'd be chased out of your shop in a minute if you started tossing out the gloss without the substance to go with it.

Enough said on the topic and like CT, I'm going to watch from a distance until there's more substantive stuff on the table. I wish you guys well and hope that an earth shattering nautical discovery emerges from your inspired communication.

 

Moth on Foils/other experiments/ Foilr, Stephen,Rick

Foilr, you asked at one point why I didn't have a Moth. The answer is very simple: I weigh 245 pounds and would be well outside of the perfomance weight range of the boat.Otherwise, I would have had one years ago. So I designed my aeroSKIFF 16 a year before the first bifoil Moth flew and built it a year after. It was not a particular good foiler design and had some serious problems. Chief among those was that it was far too athletic for me particularly recently due to some minor physical problems I've had. But it was fun and a great testbed and learning experience.When the boat foiled it was with a manual altitude control system like Luggs I14 but connected to the mainfoil flap instead of to the rudder flap. The rudder flap was also adjustable.. The mods I had contemplated earlier this year have been incorporated in the aeroSKIFF 14 a project I am collaborating on with Eric Sponberg ; the 16 has been retired to a life of teaching kids about sailing minus the high horsepower rig and foils which are being incorporated into my new "Trapwing 14" foiler described elsewhere on this forum(p2 of "Sailboats") and inspired by my desire to see if I can't translate some foiling excitement into a "sit inside" boat using movable ballast and suitable for people with physical problems and or disabilities. It is highly experimental and designed to foil only downwind to start with while I learn to use the movable ballast system.
The mods I contemplated adding to the 16 and that are part of the aeoSKIFF14 design include buoyancy pods,sliding bench seats , an adjustable hub wand with clutch disengage similar to Bradfields Rave mods with manual overide for jumping.
I think the Moth class would benefit greatly from something the Bladerider claims to incorporate: retractable foils. John Ilett doubts that will work on a Moth but the idea of having to launch and wade out a long way to install foils doesn't go over well here.They worked perfectly on my 16 and allowed the boat to be trailered with the foils and foil control systems in place making set up as simple as any other 16' dinghy. Another mod your own guys seem to think would help beginners and that I have personal experience with is buoyancy pods(see the UK site-"Is this a trimaran") .I sailed a 14 footer for a long time a few years ago that had a higher beam to length ratio than a Moth-and it would have been unsailable(by me) w/o the pods. The stabilty of the Moth is greater on foils than off and "fixing" that problem would go a long way to enticing newcomers.
But you know what really amazes me: you guys that are (seemingly) active sailing the most revolutionary development in sailing in ,at least, my lifetime are so quiet-except of course when you want to "correct" a friend regarding whether the Moth is popular(your defnition) in Australia or not. I know you guys all seem to have your own websites but I didn't even know about Luka's until you posted here-and I do research on the Moth class.How many average sailors do you guys think even know that you have a website? You can see here from the pathetic comments of some of the anti-foilers(AF's) that they don't have a clue about what is going on regarding the performance of the Moth. Is Rohan the only one doing anything? Why don't you guys start a campaign to educate the public about the foiler Moth; why don't you talk about the tremendous performance of the boat on any other forums- are you trying to keep a secret? Do you guys in Australia visit sailing schools, yacht clubs, scout troops or whatever to try to showoff the boat up close and personal? You know, most people in the US and I dare say in Oz don't have a clue that Rohan has actualy beaten a fleet of A class cats or 49ers or whatever, or that Phil Stevenson matched speed off the wind with a Tornado while in 6th place in his own foiler Moth race. In my humble opinion, you guy do not talk enough about your boat-and I look at every major forum. In thread after thread on various forums are glaring falsehoods or "facts" that are plain wrong aout the Moth that you guys could clear up-if you decided to take the time and the heat. You can see on this forum if the AF's can't get you on the facts of the incredible performance of the Moth they'll come at you personally with out right lies, innuendo,distortion etc. Are you Moth guys afraid of incurring the wrath of some of these losers?
You asked what suggestions I might have: the biggest one is SPEAK UP! Don't let this exciting time go by whle you guys talk to each others website-get on SA- I would but can't because of their new software being incompatible with my antique webtv-but whats stopping you guys?
My interest is Moth techology not the Moth class specifically and I think you guys have a golden opportunity to translate the publicity the technology is receiving to boats on the water if you'd just be more proactive about getting the word out-and I wish you the best of luck!
Whether you guys fully appreciate it or not the the Moth technology is very significant in the annals of sailboat design. The AF's realize this
and three of them on this forum -unable to discredit the technology- try hard to discredit the messenger by calling the facts I have presented here "hype" and by ,most recently, engaging in one of the most disgracefull campaigns of personal attacks that I have ever witnessed on any forum. The attempt is clear : to shut me up. One of these individuals went so far as to say:".. He is also part of the mechanism of destroying dinghy sailing as foiler sailing is like a side car attraction..." Destroying dinghy sailing all by myself?? I know my last name is Lord but that goes too far....
To friend and foe alike let me make this clear: I will , to the best of my ability ,continue to present the FACTS of whats happening with bi-foil monofoiler development at every opportunity whether that means relating another Moth class "speed record" or Sean Langmans Maxi Skiff or the Out95 foiling. I will continue to report both the good ,bad and hopeful about my own foiler experiments and will contribute to this thread, "Foiler Design" and the "Trapwing" thread as I have something to add. And I encourage others interested in foiling to speak up and celebrate being alive in one of the most electric era's of sailboat innovation in history-Don't let the Af's discourage you-let's get the word out and let's discuss the newest developments ,misconceptions and disinformation about bi-foil monofoilers.
And once again: no, I won't be quiet.

 

Thanks Doug.

A few comments...

Fair point. Performing at the front of the Moth fleet does require youth, athleticism and relatively light weight.

Yes they'll help launching, though won't achieve anything while sailing. Then there's the task of putting them down when you're sailing which is not trivial on a boat that is less than a foot wide. I'd like to see it in action though.

Don't like the idea personally. But then it would help people who are learning.

Yes. I would say there are very few Mothies that frequent internet forums. There are few Mothies to begin with. But then there are very few of the top 18' skiff sailors, 49er sailors etc here as well. I'd guess there are very few really brilliant sailors posting on the internet in any capacity.

I agree that we should speak up, and we all do it in our own way to provide our honest and authentic opinions and experiences with the boats. Internet forums don't lend themselves to either honesty or authenticity unfortunately.

Unfortunately the bits of information that do make it here end up being so distorted after passing through so many hands. ie. Phil paced a Tornado for a few hundred metres that day at SIRS, he was not racing, nor was the Tornado. VMG wasn't taken into account. Neither Phil nor any other Moth sailor I know would claim to be faster than a Tornado around the track.

We need to be pretty sure that what we claim to be evidence is rock-solid. One shadow of a doubt on a claim we make discredits everything else we say. Most of us don't want to look like fools.

Keep it real mate

 

Have you considered getting ONE system to work reliably before tossing all the bells and whistles into one boat? Like dusting off the foiling canter One Metre and getting the foil control system to work, then replacing the canting ballast with a sliding deck ballast system?

I'm certainly not anti-foiler and from what I've read in this thread I don't see any "Anti-Foiler" posters. I certainly have not described your efforts to build a foiler as pathetic, yet you feel that there are "Anti-Foilers" that are making pathetic comments. Who's guilty of mud-slinging?

The fact that a World Champion has sailed faster than a fleet of whatever's is not news. A World Champion that could not out sail a fleet of whatever's would be.

Matching speed with "a Tornado" while in 6th? So? What place was the Tornado in? Was it racing? Did it know it was (or should have been) racing against the Moth?

Just so we are clear ... NO one is even trying to discredit the technology. It exists, it is interesting, no argument. Where we differ is the importance to sailing in general, what works (extremely well) at the Moth scale has absolutely no impact on the future design of 40ft mass produced sailboats. There will never be a Beneteau Foil 37.5 ... Calling the the foiling Moth one of the greatest innovations in the last 100 years is hype ... some of us are tired of it.

"Hype"
1. Extreme promotion of a person, idea, or product.
2. overwhelming publicity or exaggerated claims v. to promote or accent excessively
3. to give something more attention than it deserves or to try to make it seem more important than it really is
4. A hyperbole, largely synonymous with exaggeration and overstatement, is a figure of speech in which statements are exaggerated or extravagant. It may be used due to strong feelings or is used to create a strong impression and is not meant to be taken literally.
5. Technology hype is unjustified, excessive discussion and usage of a technology or concept

Facts are one thing.

Fact: Someone on a foiling Moth got a snap 27.9 knot reading on a GPS
Fact: The 10 second average is 20% slower
Fact: GPS speed reporting data is notoriously full of spikes, most people don't take spot GPS readings seriously
Fact: People that look at GPS track data for speed conformation are leaning to an average of several non-overlapping 10 second data tracks.
Fact: On a given day two back to back GPS runs can vary by 10+ knots (we have big current here).
Fact: The only valid way to measure sailing speed is over a closed course, GPS was not designed to measure speed (that's why it is not very good at it).

Taking those facts, picking out only "Moth on foils 29.7 knots" and claiming that foiling sailboats will revolutionize sailing ... is ... HYPE

 

The source has survived!

Doug, I am relieved to hear that you are still OK. Can you please keep the postings down below 1000 words though, unless you really have anything new!
There is nothing that will allow the Moth class to grow significantly, in my opinion, as it seems to way out on a limb to what mainstream sailors might be interested in. It is spectacular, it is very fast, no argument, but is moving into a rarified environment since it went 1 foot wide, and even more so when it sprouted foils.
No one can build one at home that will be truly competive at the top level, and the cost of buying a professional built one, is too high for the TARGET MARKET. Yes, the target market is older teenagers and a few years older, that generally dont have the finance.
As we all get older and then have the money, some of us get heavy, less agile, and want something that is comfortable as well as high performance. Therefore your dilemma, to get the numbers to grow isn't going to happen!

 

Moth on Foils: Keep it real, Mate

++++++++++++++++++++++++
Scott, I make a serious effort to accurately quote what people who sail Moth's have said on the subject. If you check here , post 38, you will see that I was exactly correct in my description of what Phil said he did. This is one of the coolest, most inspirational things written by any Moth sailor anywhere at any time:
Building a Moth - Sailing Anarchy Forums
Address:http://www.sailinganarchy.com/forums/index.php?showtopic=27655&hl=
I 100% agree with you that comments regarding Moth performance by Moth sailors needs to be
reported accurately and I do my best.
I don't blame you for not wanting to look like a fool but I can't understand your reluctance to utilize the internet to communicate facts about the Moth-you have your own website so you can't be too negative about the internet-and you have posted here. There is much people like you , Luka and others can do to get the word out about your fantastic class without looking like a fool to anyone.(except ,perhaps to AF's, but they don't count)
Do you guys-as a class- in Australia have any organized way to introduce more people to the boat? Don't you think it might be beneficial to try such things as removable buoyancy pods to-at least- give people a taste of foiling that they otherwise might not get because of becoming frustrated trying to keep the boat upright as a seahuggger? I'm curious about your thinking on how to take advantage of the remarkable situation you've found yourself in as a foiler Moth sailor.

 

Case in point of how a statement can be mis-interpreted.

No. The Association only barely has the funds to survive year to year. It does not have the funds to support a fleet of learn-to-sail Moths, and very very few sailors give away their $18k carbon fibre toys to learners.
If a sailor is going to get frustrated keeping a boat upright, they're not going to be Moth sailors. Simple.
Being a Moth sailor takes a unique mindset. Ego is not something you want to bring to the class, because you're going to get cut down to size very quickly. A Mothie needs to be very persistent, very patient to learn how to sail one. There are very few people in this instant-gratification society who have those attributes.

The Association doesn't have a militant recruitment approach. The majority of sailors enjoy sailing and racing their boats without the hard sell and ra-ra publicity. We've taken a hands-off approach, if people are interested in sailing our boats, they'll take it on their own initiative to do the research and come down and get involved. If they don't have that amount of initiative they're hardly going to survive. Obviously that approach isn't entirely successful in increasing the numbers.

But then I have given my foiler to a bunch of rock-stars for test sails. A few Moth World Champions, a few 18' skiff winners, a few guys who could spend the $18k without blinking. None of them are rushing to order boats, despite being amazed by the sensation. Unfortunately the class lacks the critical mass of closely matched boats which would make racing for these people worthwhile.

So... a podded-contraption won't be the silver bullet. I don't see the problem as being a technical one.

 

Moth on Foils: 27.9 knots /Yachts and Yachting

For those in denial regarding the Moth class "contest" and the reliability of GPS speed readings it is interesting to note the comments by the designer of the Velocitec on Rohans website as well as the fact that Rohan is currently ranked at #1 in dinghy speed by the Speed Freaks page of Yachts and Yachting who attempt to weigh the plausibility of GPS speed claims-giving Rohan an 85% plausibility.
Sailing news as it happens - Yachts and Yachting Online
Address:http://www.yachtsandyachting.com/speedfreaks/
+++++++++++++++++
Foilr: "podded contraption"?! Wow! I've never heard Mr. Bethwaites HSP's described like that-live and learn I guess.......

 

Open your eyes people.

More HYPE, Yes it is a fact than the site posted gave the 27.9 number a 85% plausibility. The site lists 17 speeds with rankings that range from 50% to 95% with 13 of the 17 scoring an identical 85%. How is plausibility rated? The "evidence" posted in support of the claims include spikes over distances of 80 feet, 44 metres, and 430 feet. The "scores" were 95%, 85%, and 95% respectively. How credible is a 85% ranking from a source that rates a 80 foot spike at 95%?

How credible are speed accuracy claims from the manufacturer of a GPS unit that does not do data storage and download?

Anyone that has spent any time looking at GPS data knows that single data points are very unreliable. All one has to do is set the GPS unit on a table and let it record for an hour. The GPS will tell you that it has gone for a walkabout at speeds up to 3 knots while all the time your lying eyes tell you it has not moved off the table.

Add the fact that wind induced currents are on the order of 3% of wind speed, and the fact that there is no mention of tidal current during the "record" runs and it is quite clear that GPS speed is not very accurate.

In 15 knots of wind the surface current is liable to be about .5 knot. Depending on the boat's heading the same speed through the water can vary by almost a knot on the GPS.

Even if we take for granted that the tidal current is zero, a 20 knot reading might be 16 or 24, depending on boat heading and which way the GPS hiccuped that second.

As far as being in denial about GPS speed "records" ... here is what Mothies have to say:

The people that actually sail the boat no longer believe the GPS hype either.

For someone that reads all the Moth sites, I'm surprised that Doug missed this.

It seems clear to me that Doug believes the speed numbers because he wants them to be true. My daughter believes in the tooth fairy because she wants to find money under her pillow. Just because someone believes something it does not make it so. Heck, there are probably people that think Mac26's are offshore racing boats.

 

Moth on Foils-GPS

The test reported on the UK site seems totaly ridiculous: a comparision of two GPS units w/o accompanying comparison of their stats. A more interesting comparison would have been taking two of the SAME units out and seeing what the readings were.There is a whole thread on Sailing Anarchy about the Velocitec and unless you assume the designer is outright lying or purposely exagerating it is the most accurate handheld "sport" GPS on the market with far less tendency toward spikes or other anomalies than the Garmin.
In a worse case scenario RHOUGH has pointed out that it is plausible that Rohan actually did 33.4 knots(38.5mph) rather than the paltry 27.9 knots Y&Y credits him with. Way to go Rohan!
Even though, thanks to Mr. Hough ,it seems possible that Rohan is approaching 40mph I think Rohan did exactly the right thing when announcing that he'd whipped Sam Pascoe's max speed: he simultaneously announced the 10 second average at around 23 knots. Which was the MAX speed only a short time ago.
Anyway you look at it it is absolutely clear that the top end speed of the foiler Moth has not been reached yet and you can count on seeing it here when it is.

 

Let's compare stats:

Velocitek Speed +/- 0.2 Knots

Garmin Speed +/- 0.05 m/s

0.05 meter/second = 0.097192225 knot

Comparing manufacturer claims, the Garmin Unit is twice as accurate as the Velocitek

The real issue is the nature of GPS. A GPS unit does not measure speed directly. Speed is calculated from a change in position over time. The speed indicated is only as accurate as the position information and clock used to make the calculation.

How accurate is the position? Outside North America the reported position is within 15m 95% of the time. In areas that have WAAS coverage (North America) the position is within 3m 95% of the time.

27.9 knot = 14.353 meter/second

27.9 knots reported by GPS means that the position changed 14.353 metres in 1 second. However the start point is +/- 15m and the end point is +/- 15m. How can anyone rely on a 14.353m position change when the accuracy of the system is only +/- 15m?

22.3 knots over 10 sec = 114.72 metres

Could be 99.72 metres (19.38 knots) or 129.72 metres (25.21 knots)

The nature of the GPS system does not allow for accurate speed measurement at low speeds over short times. It does not matter who builds the unit, the raw information from the GPS system has limited accuracy and should not be used for speed indication.

Using a GPS receiver for spot speed measurement is like using an elastic band for a tape measure. The results are not reliable, repeatable (except by chance), or accurate.

On another forum someone tried to dispute GPS errors with the observation that the two GPS units on his boat always agreed within 0.1 knot ... I asked him which side of his boat was a mile ahead or behind after sailing for an hour ...

I agree that the top speed of the Moth has not been reached, we don't know with any real degree of accuracy what the speeds are, but I'm sure they will get faster. Perhaps someone will drop one off a cliff with the GPS unit turned on and claim 50+ knots with a photo of the read-out.

 

My error.

"From the NAVSTAR GPS User Equipment Introduction document Section 3.7:

GPS receivers typically calculate velocity by measuring the frequency shift (Doppler shift) of the GPS D-band carrier(s). Velocity accuracy can be scenario dependent, (multipath, obstructed sky view from the dash of a car, mountains, city canyons, bad DOP) but 0.2 m/sec per axis (95%) is achievable for PPS and SPS velocity accuracy is the same as PPS when SA is off.

Velocity measured by a GPS is inherently 3 dimension, but consumer GPS receivers only report 2D (horizontal) speed on their readout. Garmin's specifications quote 0.1mph accuracy but due to signal degredation problems noted above, perhaps 0.5mph accuracy in typical automobile applications would be what you can count on."

Although Doppler shift should be more accurate than position comparison for speed, the fact remains that a GPS receiver at rest will record changes in position and non-zero speed.

The simple fact that an instrument reports both position change and speed change while sitting on a rock tells us that the same errors must be present when the unit is moving.

Every data track that I have ever looked at has random spikes from moment to moment. Take a look at this track from a 95% plausible speed report: Dart Track

Note that from 11:05 to 11:07 the reported altitude varies from 0 to -15 feet ... should we start a thread on sailing submarines? It would as valid as 27.9 knot GPS speed.

Look also at the reported headings, they vary from 356 to 27 ... randomly ... think how much more credible this "evidence" would be if the boat was not submerged and was sailing in some semblance of a straight line ... yet it was rated as 95% plausible?

 

Moth on Foils: Velocitek Responds

Here are Alex Stewarts(designer of Velocitek) comments regarding Mr. Hough's posts. I want to thank him very much for taking the time to respond and apologize for addressing my e-mail to him as "Stewart" instead of Alec:

From: stewart@velocitekspeed.com(Alec*Stewart) D
Hi Doug,
Thanks for the email. Here are my comments:
"The real issue is the nature of GPS. A GPS unit does not measure speed directly. Speed is calculated from a change in position over time. The speed indicated is only as accurate as the position information and clock used to make the calculation."
-This is not the case. All GPS receivers I know of (including ours and Garmin's) calculate speed based on the Doppler shift of the GPS signals from various satellites. Since the frequency of the GPS signals is not influenced by irregularities in the ionosphere, velocity solutions are much more accurate than position ones (position solutions rely on calculating the transit time of the signals which is influenced by variable conditions in the ionosphere).
"Using a GPS receiver for spot speed measurement is like using an elastic band for a tape measure. The results are not reliable, repeatable (except by chance), or accurate."
-Please borrow a gps receiver and drive around with it on the dash of your car somewhere where there are no tall buildings or trees. Compare the readings to your dash speedometer. I'm confident this exercise will change your mind.
"Let's compare stats:
Velocitek Speed +/- 0.2 Knots
Garmin Speed +/- 0.05 m/s"
-These stats are for steady conditions. Anyone who has used any kind of GPS speedometer can tell you that when you are constantly accelerating, turning and getting bounced around the accuracy suffers. Spikes in the output become apparent and the output can also lag in time.
The difference between Velocitek and mass market brands is in how we handle this problem. The mass market brands deal with speed measurements almost as an afterthought. They record maximums without any filtering. If there is one errant spike in a four hour session, they will grab it.
For us, speed measurement is the main event. We also have the benefit of knowing the device will be used in a boat.
Before we record a measurement as a maximum or as part of a ten-second average we screen it using a simple model of the dynamics of a sail powered, planning hull. If the measurement infers an acceleration that defies the laws of physics, we chuck it.
A simple way to test this is to put your S5 on the dash of your car. Floor the gas pedal up to 40mph and then slam on the brakes. You will see the numbers on the display keep up with your dash speedometer, but when you press the max recall button you will see something under 20 knots.
Our final layer of protection against spikes is that our devices allow the best 10 second average to be recalled instantly. This allows you to judge the credibility of a speed for your self.
Based on our experience with windsurfing where we see measurements like Rohan's all the time, a max of 27.9 knots with a 23 knot average is pretty reasonable.
I hope this helps. Please let me know if you have any more questions.
Best regards,
Alec
-----Original Message-----
From: Doug Lord [mailto:lorsail@webtv.net]
Sent: Saturday, July 08, 2006 6:23 AM
To: stewart@velocitekspeed.com
Subject: boatdesign.net
Stewart, when you have a chance could you comment on the (short) GPS discussion here:
Moth on foils 27.9 knots (32mph) - Page 14 - Boat Design Forums Address:http://www.boatdesign.net/forums/showthread.php?p=96019
**I would appreciate it-the forum isn't as big as SA but there are many technically inclined sailors participating.
****While I'm not a customer yet I will be soon. Thanks! Sail Fast, Doug Lord

 

Yep, as I posted, I was wrong about how GPS receivers do speed.

We are missing the point. 22.3 knots for 10 seconds or 27.9 knots for however long are indeed impressive numbers. Even if they may not be accurate by 10-20% they would still be noteworthy. No argument.

Where we differ is our perception of what implications Moth Speeds have to the rest of the world.

My opinion is that little boats, sailed by top athletes that display phenomenal performance (due in part to the unique physics of scale), have little or no interest for mainstream sailing. Foils on little boats are not going to spawn foils on production Hunters, Catalinas, or Beneteaus. Thus I do not feel that foiling Moths are anywhere near one of the great innovations of the last 100 years.

In contrast, Stainless Steel rigging, Alloy Spars, Dacron Sails and Lines, and Glassfibre Hulls have all changed sailing in the last 100 years. Almost every boat in a marina has all of these features. Better sailing through chemistry.

27.9 or whatever, yes very fast. Yes, remarkable. Portent of things to come outside of little boat racing in sheltered water, no.

Doug, you are a clever guy. I'll bet that you can build a fun to sail "sit in" boat. Why it has to be a single track foiler is beyond me.

Why not start with a trimaran platform to eliminate the gadgets needed to balance the thing and optimize the design for low speed take-off rather than top speed. You have already done most of the homework on what it takes for early lift off and you have a working prototype. I would think that the chances of success would be greater starting from what works now, rather than from a clean sheet of paper.

 

The MM56CX hybrid DAT hydrofoil

Stephen,

Sorry, I did not answer your question about the MM56CX drag. I am submitting it to the whole group because after testing it, I very much like the concept and have ambitious plans to build a motor yacht with this concept for myself if I become rich and famous someday- it would have retractible foils though to allow for porting and shallow Chesapeake Bay Operations, I have most of the sticky and difficult details worked out but don't choose to discuss that yet....

I must clarify this testcraft is not my boat design- it is the brainchild of Rune Odegard of Sandane, Norway, and we supplied him with the data for him to analyze and report mostly. (Rune may be reached at rune@vestdata.no or rune@runeco.no, depending on if he is in or out of his office) Rune holds international patents on the application of dynamic support to trimarans for ferry service, and calls it a DAT, or Dynamically Assisted Trimaran. I created a new foil section for this task, designed the foils, & we built the boat (I and a freind of mine machined the 16ft wide 16 inch chord foil section on a VMC 150 CNC mill ourselves of solid aluminum, and I machined and welded all the struts as well as performed a lot of the hull welding) & then performed the tests for him based on prior work experience together on the Cirrus 120 and UT-928 SES ferry vessels built at Brodrene Aa in Hyen, Norway. He is very sensitive about the design, however I don't think he'll mind my posting this drag test result. These are tow test results with a rope and load cell- the scatter is due to the experimental data acquisition method and I think it is conservative- I must caveat the test was only somewhat valid- our 'thrust line' was not where it normally would be towing from the bow, and controlling fore aft trim during the hump region was highly difficult for the skipper of the testcraft- I was driving the tow boat and recording the data points. Drag reduction for these boats is accomplished through reduced wetted surface of course, but the flap angle & incidence angle vs speed schedule is critical to maintain- and very difficult while towing. We had to repeat the procedure over and over again refining it each time, and average the results. Later we had load cells on the outboards allowing a better drag curve to be generated, but only have these more sophisticated results for the lifting bodies. The normal foil application employs a computer programmed schedule of flap and trim, which has the tendency to optimize the drag curve better than we could during this test. Also, we had a hydraulic jump at hump caused by the bow wave reflecting off the inner strut- something we solved perhaps after this test, I am not certain- this testing was done in 2000-2001. I need to see if my partner has a final report in his archives I can officially post some of the results from.

Also, the original testcraft used 2 Berkeley waterjets to try to mimic the KaMeWa's likely to be specified in the full scale craft so we could get some experience with waterjet inlet broaching, etc. Unfortunately and as you may know, the Berkeley's and KaMeWa's are apples and oranges- Berkeley jets are more for drag boats and use pressure charged inlets while the KaMeWa jets are higher mass flow and usually employ more iso-kinetic inlets. This meant that our efficiencies were, well, pathetic on the model craft with the Berkeley jets installed (40% tops...). Nothing against Berkeley- they are fine jets, they just were not designed for this task- we should have just used outdrives probably. In the picture I posted, we had twin 250 Yamaha outboards on the back with much better efficiency, (probably around 60-65%) but also with lifting bodies we were testing for Navatek (You can find and download the report I wrote with Chris Hart and Bill McFann at ftp://www.foundation.csulb.edu/CCDoTT/Deliverables/2001/task 2.14.1/task 2.14.1_Final Report.pdf), with outboards or outdrives we could fly 100% of course, whereas the waterjet inlets were flush to the centerhull.

I will leave it to you to figure out the comparisons, but I think you will find it is dramatic. At high speeds, drag can probably conservatively be 1/3rd or so that of a semi-displacement hull. I would have to derive the curves for a similar semi-displacement boat and must get back to work, sorry. I will say that once we had this boat flying, we always seemed to need more weight, and the seakeeping was fabulous as I stated before. My absolutely favorite thing was to perform trials on this boat, and if it got rough it was the preferred place to be for absolutely positively certain as we watched the chase boat suffer. Too bad we could not have had this boat as the camera platform- it would be spectacular in that role. I wish we had it running to go film the Volvo ocean racers sailing down the bay!!!

Hydrofoils of course always have a cross over point before which they add drag, after which they reduce drag. Discussions of semi-displacement usually involve boats where this is critical to analyze carefully- In comparisons recently done for a large semi-planing cat, the centerfoil concept was proven too risky and would only add drag at cruise. Large trim tabs however took the top speed from 24 Knots to 28 Knots, pleasing the owner a great deal while also providing him with motion control since we also installed our dynamic motion control system.

Regards,

Rick