Dynamic stability

I'm not going to answer the points you mention one at a time, as it is Saturday and I want to spend most of my time with my kids at the ski slope, but the one selected above just has to be addressed.

Really? You think you can reduce the keel bulb weight just because you have a foil sticking out of the side of the hull?

What happens when the foil breaks off, you are out blasting along in F5 conditions and you have full sail up because you think you are immune to the physics of the whole thing?

OOOOPS! "Sorry my friends if you are all getting wet today. The manufacturer said it would work flawlessly. I had no idea it could just snap off like that. Does someone have a radio so we can call for help, as the boat is pinned over on its side and has no way to right itself?"

Not to mention that she's taking huge amounts of water though the companionway and looks to be going down any minute now.

Is that what you meant by less weight in the bulb?

Multihull envy can be a dangerous thing. ;-)

 

This brings the discussion to an important point.

Boats must be designed anticipating failures of major design elements. Failure to do worst case analysis at design time results in huge problems like canting keel failures. The practical result is that the only people willing to risk using the technology are extreme racers that understand the inherent risk.

This brings a major engineering school tenet to the table - fail safe design. Designs should be engineered to fail safely - not fail catastrophically. Reducing keel bulb weight in a foil assist design is creating a fail-catastrophic scenario, just like hydraulic failure on a canting keel design.

On this lifting horizontal foil design, failure to move the foil across the boat on a tack or gybe places the boat in danger - the foil will be doing exactly the opposite of it's design brief - decreasing righting moment dramatically.

 

I suggest you look at the website mentioned before then your worries is gone: It says using the system you do not take the keel/bulb away, but you make it lighter then it fulfiils the need for lift and the need for producing righting moment for safe sailing, but no extra weight for performance. If you don't want to use the wing let it be in the hull, don't pull it out. Sail without the wing, probably you have to reef earlier. Then it's like sailing before you mounted the wing.
Comparing monohull with a canting keeler and monuhull with wing gives:
-No heavy and expensive canting keel arrangément.
-No need for extra foils to produce lift as in the canting keeler.
-Less weight in the keel.
-No need for a bulb.
-The wing produces more rigthing moment the faster you go. The canting keeler remains with the same righting moment it can get with the keel "max-canted".
-The wing produces more decrease in deplacement the faster you go. The canting keeler does not.
-No problem if you get caught with the wing out on the wrong side. It will be over the surface in the air and not as with canting keeler; Big problem!

 

You do have to provide power and a method for moving the foil from side to side. On a larger boat this means a similar arrangement to a canting keelboat. I question the ability to use "ropes" to move a large, hydrodynamically loaded foil across a boat of 20'+ without serious effort.

Wrong. The horizontal foil IS an extra foil. The keel is still there.

All of these claims need further review. Fundamentally, you are just trading displacement for increased drag IF the horizontal foil actually provides enough lift. There is no way you can affect one side of an equation without changing the other.

Bertil:

Looks like you implicitly believe & trust things you read on the Internet. Looks like you've been drinking the "free lunch" Kool Aid with Doug.

The website(s) you mentioned as validation are NOT unaligned third party peer reviews of the technology under question - they are marketing pieces designed to increase interest and credibility.

I am a professional engineer, and there is no way I would accept the marketing information claimed/implied without third party documentation, testing, evaluation and a National professional engineering body certifying the results.

From a layman's point of view it is easy to believe things you read on the Internet - especially if it is simply presented in an apparently logical and quasi- scientific fashion. The Internet accepts no liability, has no professional standing, has no accreditation and provides no insurance for malpractice or failure to meet expectations. You can't sue the Internet if you boat sinks.

I did carefully review the website cited - and did notice areas/claims that need further investigation. I'm not saying the technology is problematic - just that it merits further review.

Perhaps it is a professional attribute learned over time, but I do not trust web sites, do not trust claims of performance made without testing, attribution and public peer review.

From a layman's point of view, all you have to do is sit back two years and watch the market. If the technology presented is truly revolutionary and it does provide a "free lunch", it will quickly dominate the marketplace and Dynamic Stability Systems will become the Microsoft of Naval Architecture design licensing. DSS-equipped boats will win the Sydney-Hobart, The Vendee records will be re-written and I'll dine on crow.

--
Bill

 

I have done the mathematics of the wing on my boat. The results I am getting proves what is said on the website. I suggest that you as an engineer can make the mathematics yourself. It isn't so difficult to count on lift and righting moments.
I think they will win the Sydney Hobart and so on. Count on it and you will perhaps rethink, or you can give me better reasons than you have given me so far aboat DSS-systems.

 

Hi Guys,
As a new commer to this thread, I would loke to highlight the pros and cons with a leeway wing.

By using a leeway wing you are able to increase rightening moment when needed, as known lift increase by the square of speed, important to keep in mind.

So let´s say we got a monohull sailboat were we are able to reduce keelweight as much as the boat is still self rightening and safe with keel.
Still sail well up to predicted speed before pushing out wing.

The good thing is that we got a lightwind boat that don´t need to carry extra unnecessary ballast in these conditions.
Float higher and don´t have to move the extra water. (Archimedes)
The pro is: faster lighter boat with less energy needed to go forward
So far so good
When we get to higher windspeeds and extra rightening moment is needed we add the wing.
Let´s say 6 knots We got for example a lift force of 300 kg
at 12 knots of speed we got from same wing 1200 kg, this is the beauty of dynamic stability.
We don´t lack power as the force from the sails also increase by the square of speed. Extra added drag from wing is paid.
The faster the boat goes, the more the wing add rightening moment,
and actually lift the hull, but not out of water . Less wet surface
With a keel with fixed weight we don´t get these dynamics.
So to increase stability traditionally you use waterballast or canting keel.
The extra added lift from the wing appears a bit aft of the keel and take load off the rudder.

All this together makes a lighter boat with less whet surface than traditional.
less pitch in sea. Dampened movements. Faster, less ballast needed.

Cons: Extra handling when tacking. Push button or rope
The construction have to be reliable and safe in all conditions.
Engineered so the wing brakes at a determined point if hitting obstacles in the sea (daggerboards Volvo Oceanrace) Easy handling, These things are relatively easy to obtain.

My opinion is that the pros are more than the cons.

Once had a boat with open transome in the early eighties, comments were the boat will sink, water fill cockpit etc..
Now many new boats got open transomes and all ocean racingboats got it.

There is allways a conservative approach to new things in the boating world.

 

Hi Guys,
As a new commer to this thread, I would loke to highlight the pros and cons with a leeway wing.

By using a leeway wing you are able to increase rightening moment when needed, as known lift increase by the square of speed, important to keep in mind.

So let´s say we got a monohull sailboat were we are able to reduce keelweight as much as the boat is still self rightening and safe with keel.
Still sail well up to predicted speed before pushing out wing.

The good thing is that we got a lightwind boat that don´t need to carry extra unnecessary ballast in these conditions.
Float higher and don´t have to move the extra water. (Archimedes)
The pro is: faster lighter boat with less energy needed to go forward
So far so good
When we get to higher windspeeds and extra rightening moment is needed we add the wing.
Let´s say 6 knots We got for example a lift force of 300 kg
at 12 knots of speed we got from same wing 1200 kg, this is the beauty of dynamic stability.
We don´t lack power as the force from the sails also increase by the square of speed. Extra added drag from wing is paid.
The faster the boat goes, the more the wing add rightening moment,
and actually lift the hull, but not out of water . Less wet surface
With a keel with fixed weight we don´t get these dynamics.
So to increase stability traditionally you use waterballast or canting keel.
The extra added lift from the wing appears a bit aft of the keel and take load off the rudder.

All this together makes a lighter boat with less whet surface than traditional.
less pitch in sea. Dampened movements. Faster, less ballast needed.

Cons: Extra handling when tacking. Push button or rope
The construction have to be reliable and safe in all conditions.
Engineered so the wing brakes at a determined point if hitting obstacles in the sea (daggerboards Volvo Oceanrace) Easy handling, These things are relatively easy to obtain.

My opinion is that the pros are more than the cons.

Once had a boat with open transome in the early eighties, comments were the boat will sink, water fill cockpit etc..
Now many new boats got open transomes and all ocean racingboats got it.

There is allways a conservative approach to new things in the boating world.

 

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Thats nuts: you can't seriously be saying that pulling an unloaded foil from side to side is equivalent to canting several tons of lead from side to side!! Your objections have been 100% dealt with by the DSS people and in the interview with Hugh Welbourn. This technology is a great idea that is being refined all the time by people that know what they are doing and have done the testing to prove it.
I'm doodling with some small boat ideas like a small keelboat that uses a foil like this to increase RM-the gains are really substantial. There are applications for this technology from small boats to large boats and from monos to multies-it is not a technology in need of "further review" -it is a proven technology that offers wide applications throught the spectrum of sailboat design.
----From Hugh Welbourn: "With DSS, the loss of the foil merely returns the boat to a normal configuration with its stability profile able to pass the relevant standard."
---- The fact that the lift/ drag ratio of a foil used to increase righting moment can be beneficial was proven long ago with fully submerged hydrofoil systems that were(and are today) used to develop all of the RM for the boat they are used on. Record breakers like Long Shot have used such a system to go really,really fast.

 

Bertil and Henning...

Bill has made some extremely powerful points and you guys are stuck on your position. So.... I'll tell you the same thing I tell Doug Lord when he starts to foam at the mouth with some ultra-revolutionary thing that is going to forever change the way people sail their boats.

GO BUILD YOUR BEST REPRESENTATION OF WHAT YOU THINK THIS IDEA SHOULD BE, GET IT OUT ON THE WATER IN SERIOUS CONDITIONS IN FRONT OF A LOT OF NEUTRAL PEOPLE, SHOOT HUNDREDS OF MINUTES OF VIDEO TAPE WITH HUNDREDS OF HIGH RES STILL PHOTOS AND BRING BACK THE RESULTS. PUT SAID RESULTS BEFORE THE ASSEMBLED GROUP HERE AND WAIT FOR THE BROADER THINKING CAPACITY OF THIS LARGE COLLECTION OF VERY LEARNED FOLKS TO HAVE THEIR OPINIONS.

Oh... and make sure you do that energetic shaving of the keel bulb for significant reduction in weight as promised... and bring evidence that this was actually done.

While sailing under F5-F6 conditions with the foil fully deployed, quickly retract the foil within the hull and tell us what happened to the boat when it lost lift instantaneously with a significantly reduced keel bulb.

If you want this new device to be all that you claim, then you should not be hesitant to put all your testing discoveries before the group here where peer review can take place.

Go ahead, take your time... we can wait. The sailing world has gotten on just fine for thousands of years without the foil you describe and I'm sure it will continue to do so even if the testing turns-out to be a bust.

Finally, Let's say that your chosen boat is a 30', well-designed performance monohull. I'll bet that with all the changes you propose to your monohull, including the use of the lifting foil, you still won't be able to sail faster than a Seacart30 in the same wind and sea conditions... so the point you wish to make is...?

The testing is all done and Bertil turns to Henning and says, "We fiddled more, we added yet more complicated, vulnerable stuff to the boat and even took some of the lead away and, dammit... we lost sight of that friggin' Seacart and they kicked our butts upwind and down."

As Doug Lord would say... It's a revolution!! Not sure who is going to benefit, but it's a revolution, nonetheless.

 

I notice that none of you dreamers have mentioned the business of sailing with a nice hunk of seaweed on the foil.

Is this another of those moments in the discussion where you folks pretend there isn't a problem for stuff in the water when it comes to foiling of any kind? Over on Sailing Anarchy, there was a whole thread dedicated to the problems of hitting fish in certain waters and what that does to the foiling experience. There were also considerable numbers of comments about foil lift disruption simply because the foil surfaces received scratches.

I don't call that a revolution in the making guys. I call that a serious vulnerability for which there is no functional answer. Spend all that money to give your boat a so-called boost in performance and see it all wiped-out by a piece of commonly found seaweed, or a hamburger wrapper, or a plastic bag in the water from a grocery store.

It's because of stuff like this that Colin Chapman of Lotus and Formula1 design fame said, "simplicate and add lightness"

 

Doug, we agree on this point! An unloaded foil will not require a lot of power to move laterally on an UNMOVING boat.

As long as the boat IS moving, the lifting foil IS loaded. If this thing is as good at providing righting moment as claimed, it IS HEAVILY loaded. You are moving a highly loaded foil across the boat, not an unloaded one. The stiction load in this case is exactly 90 degrees to the expected travel direction of the foil. Coming back to a basic issue, there is no such thing as a free lunch! If the lifting foil provides as much righting moment assistance as a comparable canting keel, the lateral loads MUST BE the same!

Last time I looked (since I've sailed real boats myself in the past couple of years), boats don't stop moving during tacks & especially gybes. Have you every tried to move a dinghy dagger/centerboard while under lateral load? Was it easy? Why do people have 16:1 blocks on their 505 centerboards to change depth while reaching? Because it is easy?

You fail to critically THINK, and keep substituting text from other people's web pages for thinking. As my lawyer tells me, "You can't suck and blow at the same time", so Doug which is it: Does this thing provide increased righting moment, and the high loads associated, or is it unloaded and easy to move - providing no righting moment increase? Pick only one and apologize.

 

Bs & S

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You always bring that up with foils and experienced foilers have repeatedly told you it is not a problem! With this foil you can unload it, slide it in and out again OR you can use foils that pivot on each side of the boat and in heavily weeded areas sail with the board at a 30 degree sweep aft.
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Bistros, you aren't thinking: this foil would be moved when it was unloaded-like halfway thru a tack or gybe. The idea of moving it when it was loaded is absurd-and completely unnecesary.
And speaking of apologies: you certainly owe Hugh Welborn one for your outrageous comparison of him and his team to Madoff and the 50 billion dollar scam!

 

I can see clearly now. So the boat stops dead in the water. Once the VMG equals zero, the then unloaded foil gets effortlessly moved across at a leisurely pace. Once it is ready, the boat then accelerates from zero back up to speed on the new tack.

I was caught up on the whole unreasonable notion that it was good to keep the boat moving. I didn't understand the whole "helm's a-lee, stop for hors-d'oeuvres(1), gently move the foil, have a drinkie(2), re-start moving" method.

My bad. I guess I should buy a book on performance keel boating and give up on the whole skiff sailing thing. We obviously do things wrong with the whole VMG-matters wire-to-wire tacking nonsense. Here I thought I had only one to two seconds to get out on the opposite wire after putting down the helm.

I stand corrected. I'll try it your way next year once the ice is gone. Perhaps I should try adding a pair of pectoral fins(tm) to my boat so I don't have to trapeze.

(1),(2) - part of the technological "free lunch" of power enhancement at no cost!

 

I bring it up because there are many experienced foilers who agree with me. Over at Sailing Anarchy, there is a collection of comments from some of the best foilers and foiling craft design people and here's what some of them have to say...

Phil S: "Weed, plastic bags and jellyfish are a problem. Catching something on one side of the horizontal is much worse than something on a vertical."

Phil S: "Very slow if you do not get it off."

Bora Gulari: "true but every time i have gotten weed on the foils i have felt it way before i have seen it"

Simon N on I14's with T-foils: "... The "t" at the bottom was the first ideas on t-foils from Phil Morrison. There were a number of issues, not least getting weed off!"

JimC: "... Really need one of the experienced foiler sailors to answer this, but basically you stop and take it off because it slows you down, the same as if you are low riding at 5 knots and get weed on the foils you stop and take it off because it slows you down. "

Team Fugu: "... but if you could get a blade on the leading edge what would slice a fish, you'll probably also have fewer problems with the odd plastic bag or the constant weeds."

Doug Lord: "... Sure Rohan snagged a plastic bag and turned the boat over to get rid of it and continued racing regaining first place before losing right at the end of the race. The... theory seems to imply that all foilers are bad because Rohan snagged some weed or a plastic bag!"

Rohan Veal from personal blog regarding 2006 World Championship:
"From Thursday's Race Two: "However the good thing was that I was dragging around some weed for the last lap, so that was now gone and I could concentrate on catching Simon on the last lap. I closed the gap downwind again, but it wasn't enough and came through in 2nd."

Lost Championship points due to weed disrupted foil surfaces.

From Saturday's final heat: "... By this stage I had lost over 100m and Adam was now in front. Then we all tacked on the starboard and that was it. I don't know if it was weed (again) or my wand configuration, but I could not foil at all on that tack..."

Another entry from Veal's blog regarding the problems suffered by Simon Payne. This one from the race on Thursday that he won: Of significance was the race result for Payne in that heat, finishing fourth due to weeds on the foil. " ... The winning margin was about 30 seconds or so, with Jason in 2nd, Adam 3rd, and Simon in 4th after snagging some weed on a windward work."

More Veal on crap in the water: "In race two, I started mid line with Adam but shortly after crossing the line, I snagged a plastic bag in the water dropping 3 knots of speed instantly. I tacked to starboard to try and clear the bag, but it stayed on. I then tipped the boat over removed it and got going again."

Veal eventually lost that World title to Payne because the final race that would establish who would have the best standing, was decided when Veal engaged that plastic bag, had to get off the boat to get it unfouled and watched Payne rip away to the title. Seems to me that stuff in the water can be dreadfully decisive to some who have direct experience in the matter.

So, folks, you can clearly see that there are lots of comments about foils being reduced to zero value when something in the water is wrapped around the lifting surface. The comments are from some of the most visible and well-known sailors on foils these days, so they are not fluke comments.

If Doug wants to continue to live in his fantasy world about the topic, just remind him to read the quotes shown above a time or two and eventually, he will get it.

OK, Doug… go ahead and say you are sorry for the obviously poorly researched comment in your last post, as quoted above. I still have truly great amazement that you find it engaging to run your posting procedures as if you were running for a political office. You just sling the crap out there and see if anyone bothers to nail you for it.

When you are proven wrong and called out for the obvious disconnect of your comments, it would seem prudent for you to offer your finest and most sincere apology.

The readers of the thread are waiting, Mr. Lord.

 

Bs & S

You take those quotes out of context and say they agree with you-bull! You say that weed and debris are such a great problem that it makes the use of foils problematic which is absolutely untrue. Why would the Moth be the one of fastest growing new one design classes? Why would EVERY ORMA 60 trimaran use banana foils? Why are there growing numbers of hydrofoil ferries and powerboats like the Corsair hydrofoil power cat? Why are more and more development classes experimenting with hydrofoils? Why is Julian Bethwaite developing a bi-foiler version of a 49er?
You exaggerate a problem that is minor and solvable. You 100% misrepresent the story of Rohan losing because of a plastic bag-100% untrue!
The worldwide growth in hydrofoil development puts the problem in perspective: a rare and minor annoyance that is easily solved.

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See Moth on Foils posts 491,191 and 192.....