Dynamic stability

[Bertil]

I want to put a movable wing on my 40-footer as described on "dynamicstabilitysystems.com". I do not know what kind of profile to use on the wing. I know that it should be assymetric perhaps with a camber. It should be working with as little drag as possible between 6 - 18 knots, but at the same time I like it to give me CL over 1.00 and more. The AR (=span/chord) will be appr 4,5 - 6.
Do you any suggestions and reason for your suggestion?

[JesperW]

I would suggest looking up their patent to see what info it provides.
http://www.uspto.gov/index.html

/j

[Bertil]

Sorry but I could not find it there. I have read the european patent, but it does not mention anything about the profile.

[Doug Lord]

You might have more success talking directly to the DSS people to see if you can work out a deal-rather than using their technology without permission.
http://dynamicstabilitysystems.com/#/profile

[Chris Ostlind]

You can use the technology for a personal craft. You just can't manufacture the thing for profit without making arrangements to pay a royalty under license.

One of the biggest reasons for having to post the description and drawings of the patented object is so that other creative individuals can utilize the form as a jumping-off point for potential improvements to the product.

Companies are buying and/or borrowing the patented products of competitors all the time. They take the thing apart, subject it to non-destructive testing, reverse engineer the mechanical, metallurgical and electronic aspects and look to find a better, more efficient method for making their own version.

Go ahead, make your own... just don't sell it or you open a new can of worms.

[Doug Lord]

Best course is to try to work a deal with the patent holder! Below is advice that is identical to that explained to me by my patent attorney:

http://www.research.uwaterloo.ca/ttlo/ip_articles/Enforcingapatent.pdf

"There is considerable confusion on the question of whether or not infringement can occur if the
use of a patented technology is personal or non-commercial. The USA and the Canadian Patent Acts do not
sanction such activities and therefore they constitute patent infringement. This would also include the use
of patented technology to conduct research in a university or a corporation. The “urban legend” of
experimental and personal/non-commercial use being excluded as infringement likely derives from the fact
that there are few cases brought to court for this type of infringement. The reason is that it is usually
impractical to pursue such infringement cases since they are difficult to detect and even if detected, the cost
in time and money of pursing legal action would ordinarily far exceed the damages that could be claimed and collected."

[Chris Ostlind]

Oh, and don't speed on your way to your workshop, don't spit on the sidewalk, don't act friendly to married womenfolk... and a whole host of other Dudley Do-Right offenses for which there is only one remedy.... to be consigned to patent purgatory for eternity.

Sheesh...

If this process, as mentioned in the post just above, were ever truly undertaken in global business, it would shut down the works for years. Literally, for years. So, the point is...?

I'd be willing to bet that there were two or three "patent infringements" of the work of others in Doug's last sailing "creation". The folks who hold, or have even specious claims to them, can't be bothered by the one-off builders and the entire tinkerers marketplace of ideas and low-key testing that is going on out there.

If someone does bother to write to you about your adventure on all this, then simply tell them sorry and move along the path.

The big issue for the folks who go to the trouble of filing a patent application is all about manufacturing of said patent outside the loop of control and gain of the holder. Most folks I know who hold patents are rather tickled when someone fiddles with their creation, looking to possibly improve the item. If you stumble onto something cool in your journey, you may even be able to approach the original holder and then everyone wins.

This business of stifling discovery at the tiniest end of the foodchain in this fashion is the result of an overactive paranoia combined with an excess of hours with nothing else to do.

[Cheesy]

Best course is to try to work a deal with the patent holder! Below is advice that is identical to that explained to me by my patent attorney:

http://www.research.uwaterloo.ca/ttlo/ip_articles/Enforcingapatent.pdf

"There is considerable confusion on the question of whether or not infringement can occur if the
use of a patented technology is personal or non-commercial. The USA and the Canadian Patent Acts do not
sanction such activities and therefore they constitute patent infringement. This would also include the use
of patented technology to conduct research in a university or a corporation. The “urban legend” of
experimental and personal/non-commercial use being excluded as infringement likely derives from the fact
that there are few cases brought to court for this type of infringement. The reason is that it is usually
impractical to pursue such infringement cases since they are difficult to detect and even if detected, the cost
in time and money of pursing legal action would ordinarily far exceed the damages that could be claimed and collected."

In this case I doubt it would matter at all, this concept would fail the 'prior art' requirement so the patent is not really enforceable anyway

[JesperW]

Talking about prior art... (And Bertil, since you're Swedish): Actually this product was propably invented by Arvid Laurin, silver medalist sailing 1936 Olympics, yacht designer of Laurinkostern, Monsunkryssaren etc.

He died 1998, having talked to others about the product...

[Bertil]

Thank you for your answers according the patent. I have by help of Excel made a "program" where I get very good performance mostly with apparent wind between 50-100 degrees, using as I call it a "leeway-ving". I have tried it up to 18 knots when the boat weighing 5400kg has lost almost the entire displacement. I think I made too big a ving, so now I will make it smaller, or put it in a bit in the boat in my calculations. It is my private boat, so I will not make any profit using the idea. Last season I put a bulb on the keel weighing 430kg(deep 3,2) on the keel that is made so you by a hydraulic pump can cant it up backwards.
My excel program tells me that I can get rid of the bulb and my waterballast-system. By the way I am very surprised that there isn't any discussion of this leeway-ving here on the forum, as the idea is so very good! It is much better, cheaper, more simpel and gives better performance then the canting keel. The faster you go with the leeway-ving, the more you get increasing righting moment and decreasing displacement. Perhaps is it the way to outperform multihulls. Still I haven't got any answer on my question.

[fcfc]

Just a side note.

Seems that this wing provides lift that counteract the heeling moment of sail. So far, so good.

But alas, in the real world, a wing that provides lift also provide DRAG.

Would be interesting to study.

[Bertil]

Of course it creates drag. But less than the decreased drag when the boat heels about 5 degrees less, and decreased resistance of friction and wave drag as the boats lifts when the dept is decreasing.

[SevenFeathers]

Please pardon the intrusion of a forum newbie (well, I'm not really new... just new here).

I too am curious about the validity of foil assisted stability, but I keep getting stumped when theory meets practice...

What happens when the boat stops moving forward through the water?

Picture what happens when this lightweight speedster gets into a less-than-ideal situation like heavy seas on the nose or a botched gybe... or even just down-speed maneuvers where boat-speed through the water is minimal... or the extreme case of a survival situation offshore...

... that dynamic stability disappears and unless the boat is carrying enough form or ballast-borne stability it is going to be very, very tender... if not dangerous.

It will go like a bugger, then stop and fall over.

If the vessel is inherently able to handle these situations, then I think the stabilizing foil might be mostly redundant, no?

7F

[bistros]

I too am curious about the validity of foil assisted stability, but I keep getting stumped when theory meets practice...

What happens when the boat stops moving forward through the water?

It will go like a bugger, then stop and fall over.


You have committed the gross error of allowing theory to meet practice. As long as you keep the two separated adequately, you can theoretically do anything!

This forum has distinction of providing a soapbox for one of the world's theoretical leaders in foiling technology, and he seems quite able to keep theory pontification and personal practice from colliding.

[Bertil]

I propose you look at the internet: "dynamicstabilitysystems.com" and read what they say. Off course you need to have a keel with weight giving enough stability to meet the requirements for a safe boat. It is the added kilos for performance you can switch out by using the leeway-wing.

[Doug Lord]

Please pardon the intrusion of a forum newbie (well, I'm not really new... just new here).

I too am curious about the validity of foil assisted stability, but I keep getting stumped when theory meets practice...

What happens when the boat stops moving forward through the water?

Picture what happens when this lightweight speedster gets into a less-than-ideal situation like heavy seas on the nose or a botched gybe... or even just down-speed maneuvers where boat-speed through the water is minimal... or the extreme case of a survival situation offshore...

... that dynamic stability disappears and unless the boat is carrying enough form or ballast-borne stability it is going to be very, very tender... if not dangerous.

It will go like a bugger, then stop and fall over.

If the vessel is inherently able to handle these situations, then I think the stabilizing foil might be mostly redundant, no?

7F
===========================
Using foils to stabilize a boat is a well proven technology. The best examples I can think of are the Rave, Hobie trifoiler and Raptor 16. On these boats the crew sits in the center regardless how strong the wind is blowing and on the Rave and Tri-foiler RM is limited only by the structure of the boat.
The DSS system is a bit different but quite innovative featuring a sliding foil.
You can bet that company has done its homework and they have found that the increased RM trumps the increased drag-just like it does on the Rave,Tri-foiler and Raptor.
The DSS system allows a completely retractable foil which is a great advantage for light air. It seems like a well thought out system to me.

[Cheesy]

Doug, doesnt 'innovative' usually mean that something is new? ie not done before

[Doug Lord]

As best I can tell using a foil in the specific way DSS is using it is entirely new-at least I've never seen it before-have you?

[bistros]

Just took a good look through the Dynamic Stability Systems website. One first impression it looks scammy. Anyone advertising their intellectual property lawyers on every page isn't trying to prove a technology, they are trying to market an intellectual property. Having an yachting insurance firm, said lawyers and sailmakers as front line partners in a sailing technology company just doesn't ring true.

I'd rather see an accredited school of Naval Architecture or Engineering as a partner.

I agree that there may be some benefit to the concept - complete with a balance of negatives.

One thing I have learned in 30 years of engineering is that there is no such thing as a free lunch. People who promote a concept as providing nothing but benefits with no liabilities are generally grifters hoping their mark's lack of education and experience allows them to get excited and "invest".

I also look at people who value "intellectual property" as a primary balance sheet level business asset as suspect. Intellectual property is a twentieth century fantasy concept invented by lawyers to try to move ideas on to a balance sheet.

Ideas are not valuable - execution of ideas is potentially valuable. Once the execution of an idea is tangible, the market will quickly establish a real value. Letters patent are a legal construct that attempt to protect a potentially executable concept for a limited time period, allowing people to invest with less fear of loss. Patents, at least are intended to cover execution of ideas - diagrams, plans and explanations are part of the patent process.

The appearance of originality is a function of the obscurity of the source of inspiration. Most patents are granted because the source of the inspiration or prior art of execution is sufficiently obscure.

[Doug Lord]

The inventor in this case is a well known Naval Architect and they are investing big dollars in an ongoing test program.

[Cheesy]

There were pictures of a NZ boat that had a very similar looking system on another forum

[bistros]

The inventor in this case is a well known Naval Architect and they are investing big dollars in an ongoing test program.

A well known and respected Wall Street financier was just indicted for a 50 BILLION dollar Ponzi scheme. Well known and respected can be a fleeting quality. Non-commercial institutions like Universities and professional associations have more credibility with me (and savvy investors).

I'm not doubting the potential upside of this development. I'm just saying that it is balanced by a combination of downside factors that must be acknowledged and understood before buying into the concept.

In engineering, the simplest possible solution to a problem tends to be the most reliable. In this case, righting moment is the problem and the simple solution is a ballasted keel. As the last couple year's public canting keel failures demonstrate, complex systems fail more frequently.

There is no doubt that things like canting keels, this "sliding horizontal lifting foil" technology and other answers to righting moment issues can provide dramatic benefit when working right. Systems like this that require engine power, microprocessor control and hydraulics are questionably outside the realm of sail boats - to me they are actually power boats that have sails. Beside the religious issue of power needed to safely tack & gybe, which boat would I rather take my family on a long offshore passage on?

[Doug Lord]

Why would this system require engine power? Trying to put this simple, elegant "foil assist" stability enhancing system in the same category with a canting keel is just plain silly.

[bistros]

Why would this system require engine power? Trying to put this simple, elegant "foil assist" stability enhancing system in the same category with a canting keel is just plain silly.

How else do you propose anyone get the sliding foil across the boat (as in the animation) on a boat larger than 20 feet? Magic moon rays?

This is basically a canting keel less the bulb - where lift instead of weight is used. It still has to move side to side during tacks and gybes, and has to do so in a reliable and predictable fashion. It would be a serious mess if the foil didn't get across on a tack and it started to push the windward side up instead of pushing the leeward side up.

Simple? Theoretically, but not in the real world. Elegant? Less so under inspection.

Even of the foil was lightweight (under 200 pounds) the loads induced by lift while the boat is moving make it non-trivial to slide across - because the boat movement is causing lift to be generated.

In addition to the mechanical challenges, now the cabin has to deal with a lateral daggerboard slot (which can't leak) and that makes designing accomodations interesting.

Doug, none of these miraculous ideas come without drawbacks.

[Doug Lord]

You know I think it is totally irresponsible to engage in a discussion where-with NO KNOWLEDGE of the system you associate its inventor -Hugh Welbourn with a 50 billion dollar ponzi scheme and then argue points proven by DSS and Welbourn!!!!! Simple and elegant in the real world-you need more information!
Read this: http://www.harken.com/Interviews/DynamicStability.php
From the Harken page:
"Welbourn Design Group

Headed by Hugh Welbourn, The Welbourn Design group has been on the leading edge of innovation and yacht design for 30 years.


With its long history of involvement at the top end of yacht racing, the Welbourn Design office is recognized as one of the leading lights in foil development as well as performance optimization. "

[bistros]

You know I think it is totally irresponsible to engage in a discussion where-with NO KNOWLEDGE of the system you associate its inventor -Hugh Welbourn with a 50 billion dollar ponzi scheme and then argue points proven by DSS and Welbourn!!!!! Simple and elegant in the real world-you need more information!
Read this: http://www.harken.com/Interviews/DynamicStability.php
From the Harken page:
"Welbourn Design Group

Headed by Hugh Welbourn, The Welbourn Design group has been on the leading edge of innovation and yacht design for 30 years.


With its long history of involvement at the top end of yacht racing, the Welbourn Design office is recognized as one of the leading lights in foil development as well as performance optimization. "


Doug, faced with a simple, straightforward analysis of material presented on their web page you respond with a personal attack, and no mention of the issues I raised.

Nothing is simple, and no gains are free. Welcome to the real world.

[Doug Lord]

Wrong: I answered every single question you raised by posting this:
http://www.harken.com/Interviews/DynamicStability.php
Read it.

[Chris Ostlind]

Besides this fact... It's as funny as all get-out that monohull sailors still wanna be like multihullers with the inherent stability, weight and speed advantages of the multihull genre. They want it so bad that they are willing to add yet more complexity to their boats. This kind of addition further increases the chances that they will suffer a complexity related failure beyond any failure regime being sustained by the original non-foiled craft.

While looking at the article shown in the link supplied by Doug, I did get a surprise boost to an argument I put forward some couple of years ago. There was a rather peppy engagement here about the merits of canting keels vs just leaving the BS off the boat and sailing it well... or, horror of horrors for the led-sledders, simply go out out and get a multihull if they want real speed. In the article above, the designer of the foil in question, Hugh Welbourn, made a comment when asked this question:

"Do you feel this could replace the canting keel?

HW: Yes. The distinct shortage of canting keel boats being built other than Open 60s and Volvo 70s is an indication of a market voting with its feet.

The complications of cost, systems, weight overheads and above all the total loss scenario when canting keels fail have been seen to outweigh the benefits."

Nicely enough, that's the very same argument I made way back during the argument with Doug regarding canting keels and, as you might imagine, he used every one of his nasty invective comments to attempt to deride my position. Now, right out of the mouth of a guy that Doug, himself, brings to the discussion table, comes the simply phrased statement that supports my position on canting keels.

Douglas... it's time to man-up about your previous short-sighted exclamations in light of the realities being shared by your very own witness. You do regard this guy, Hugh Welbourn, as someone of professional standing, do you not?

[bistros]

Wrong: I answered every single question you raised by posting this:
http://www.harken.com/Interviews/DynamicStability.php
Read it.

Read it long before I posted my response. And YOU answered nothing.

Ropes? You think pulling yet more ropes while tacking or gybing to move the horizontal board is practical? Not on any boat I've sailed on (and yes, Doug I sail on full size boats). Tacking and gybing is the busiest time on a sailboat, and adding ANOTHER manual system that is timing critical to the process isn't exactly helping.

THINK FOR YOURSELF, rather than looking for Internet quotes from people with a vested interest in the project. Better yet, gybe a kite going downwind and now add a long travel rope pull that MUST be done in the middle of crossing the boat. On anything bigger than a dinghy, you have to have a person on a grinder and a tailer. THINK. Move another 20' of rope in 15 seconds, while dealing with spinnaker poles, spinnaker sheets, jib sheets and oh, yes, duck under the boom and vang.

Hydraulic movement of the board, with automatic control is a real world practical solution. Once you've got to move the board, you have to consider how the controls attach to the board - think about another stuffing box, attachment points and how you are going to pump hydraulic fluid on demand. People choose hydraulics for canting keels because it was the best compromise solution for the problem. I'm sure no one wanted to have an engine running to keep the pumps working, but they conceded it was necessary. Why? THINK for yourself.

The people that develop systems, and are selling the systems are consciously trying to minimize apparent liabilities and optimize benefits. It's called marketing, Doug. I do it. You do it. Everybody does it.

I have not said this idea is without benefit. I have said the benefits come at a price. I'm sure the developers (if they were being candid) would agree, and also they could point out dozens of problems I haven't noticed, that they may have already addressed.

Harken is selling bearings to deal with the vertical loads induced by the lifting plane. Is Harken unbiased? They seem to be getting "free" advertising on every page of the DSS site.

Bearings? Last time I attended engineering school, bearings were a maintenance prone, wear prone, failure prone component in a system. Bearings are necessary when there are unwanted forces applied to a system. THINK. Stiction. Wear. Environmental challenges. Failure modes. Maintenance.

Nothing is simple. When you THINK for yourself.

I've never stated this technology may not offer a NET benefit - but I do acknowledge that you have to add the pluses and minuses to reach a result.

[Bertil]

It is nice to see the dioscussion is in swing.
Some comments to the multihull-man. There are some advantages with a monohull equipped with the leeway-wing to multihulls:
-They cannot turn around so easy without giving the signs that it is to happen.
-Smaller width giving easier handling and less space in harbor.
-Bigger living space for given width.
-Less wet area per kilos deplacement.
-Cheaper to build.
-Dampening/slower movements in sea-state.
-Deplacement by less weight in keel/bulb narrowing/alike to the multihull.

[Chris Ostlind]

-Deplacement by less weight in keel/bulb narrowing/alike to the multihull.

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. ;-)

[bistros]

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.

[Bertil]

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!

[bistros]

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.

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.


-No need for extra foils to produce lift as in the canting keeler.


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


-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.


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.


-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!

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

[Bertil]

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.

[Henning P]

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.

[Henning P]

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.

[Doug Lord]

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. Bill

===================================
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.

[Chris Ostlind]

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.

[Chris Ostlind]

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"

[bistros]

===================================
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!

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.

[Doug Lord]

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

[/B]
======================
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.
------------------
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!

[bistros]

======================
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.

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!

[Chris Ostlind]

======================
You always bring that up with foils and experienced foilers have repeatedly told you it is not a problem!


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.

[Doug Lord]

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.

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

[Chris Ostlind]

I give quotes directly from Sailing Anarchy by known Moth sailors, as well as quotes directly from Rohan Veal's personal website and what do you present.... Nothing but Hot Air. Why am I not surprised?

Douglas, you must be running scared to find it necessary to refute the words of your very own foiling idol, Rohan Veal.

The term, Amusing, doesn't cover half of the laughter I'm enjoying at present. Thanks for the chuckle, Doug.

[Henning P]

Mr Ostlind

May suggest you and other interested people to read "Principles of Yacht Design" by Larsson and Eliasson

Then we can have a serious discussion, this is like a kindergarten.

Some people goes into future backwards

[bistros]

Mr Ostlind

May suggest you and other interested people to read "Principles of Yacht Design" by Larsson and Eliasson

Then we can have a serious discussion, this is like a kindergarten.

Some people goes into future backwards

I have read this book and many others. I have also seen many published designs, along with many photographs of his designs on the water from Mr. Ostlind. As he has published multiple designs and actually built boats, perhaps you could concede he has reasonable understanding of design issues.

Publishing a list of your own designs, qualifications and builder/owner's comments of your boats may be worthwhile to establish your own right to question his comments.

FACTS:

Questioning other people's expertise while providing no evidence of his own expertise, education or successful full-size boat building results is a regular negative tactic employed by Mr. Lord. Mr. Lord claims to be an expert on scientific issues relating to foiling, but exhibits NO evidence of personally foiling on one of his own designs. He has shown ZERO foil supported full size boats designed by him that have been photographed foiling with ANYONE helming. Mr. Lord has been asked to leave on-line forums for his behavior issues.

Here are some fair and reasonable questions for you:

1) Do you believe that a Dynamic Stability Systems (DSS) style foil in a MOVING boat has NO lift-created load because the boat is tacking or gybing?

2) Why would such a design require load bearings by Harken if there were no lift-created loads?

3) Do you believe that manual actuated rope & block based DSS foil movement methods are adequate, timely and reliable - without additional crew? For a 30'+ performance keel boat?

4) Do you believe that a DSS-equipped boat design, with reduced keel ballast (as per the designer's comments) provides the SAME level of fail-safe capability as a standard fully ballasted design?

As I have state quite clearly in prior posts, I am NOT questioning the up-side potential of this concept, but I do believe that there are potential negative issues worth further investigation.

Objective evaluation of sailing design innovations is the point of this web site, not unquestioned promotion of sales and marketing material. I'd rather see serious peer review of technology, along with the hard questions and solid answers than biased cheerleading and zombie-like promotion of every new idea.

I would welcome Dynamic Stability Systems response and frank discussion about their concepts. I'm certain that they have encountered many of the issues raised here, and have most likely anticipated and dealt with these problems.

[Chris Ostlind]

Mr Ostlind

May suggest you and other interested people to read "Principles of Yacht Design" by Larsson and Eliasson

Some people goes into future backwards

Read the book, Henny… several times, in fact.

I’m reminded of another magical new techno solution to an otherwise slow monohull that never seemed to gain any traction in the sailing community. The guys who developed this concept, much like Welbourn, had a good deal of reputation in the community already, so the thinking process was not willy-nilly.

I give you the Loop Keel. This could possibly be the most important contribution to weed collection, after the typical T-foil, that has ever been devised.

http://www.boatdesign.net/forums/sailboats/radically-different-yacht-keel-loop-keel-16265.html

Your buddy-in-thought, Doug Lord, had this to say within minutes of the initial thread posting...

Excellent thinking! Looks to me like the keel would develop enough lift(at higher speeds) to reduce displacement and therefore wetted surface? Did you find any need for additional pitch stability at faster speeds?

In response to Doug's post, the partner in the design process, Jon Howes, had this to say to Doug's effervescence about lifting surfaces and the loop keel concept in particular.


Doug,

Thanks for your comment but you have slightly missed the point here.

Howes was actually being nice in his response in a very British way. So, you see, Doug, Henny and Bertil, you dudes have gotten all warm and fuzzy about another miracle answer to what ails the sailing business when it comes to monohulls. Bistros has enlightened you all about the engineering realities of not getting any free lunch when it comes to the design world... especially when it comes to boats, and you Henning, find it necessary to sling a Kindergarten reference to protect yourself all while offering absolutely nothing as a rebuttal to the points that were made. Very interesting tactic.

Perhaps you guys can all take a breath of fresh air and approach the process rationally and leave the emotional stuff out of the formula? The loop keel was introduced just about two years ago and still, there are no commercial boat manufacturers using the technology... that I know of. If I were to make a wager on the DSS foil, I'd have to say, at this point, that there are some very significant marketing arguments that need to made and solved publicly, for something like this to catch-on as a mass market product. It will add complexity and expense to a boat in a marketplace where buyers are already running off to smaller and less complex craft as an answer to the present realities of global economics. As long as we're making suggestions to books, let me suggest that you all do some significant reading about marketing strategies, economics and just plain old common sense.

The comment by Bistros, that the mark of a product's success will be measured by the buying public, has proven itself on the Loop Keel and will likely do the same for the DSS fin. When you add complexity, you also add expense. When the expense factor hits the buying public, and they weigh that against a perceived value for the type of sailing they will do... you will have your answer.

I assume that you three guys have gone out to buy something and you weighed the cost benefit of any purchase you were going to make. I further assume that if that expenditure were being measured in the many thousands of dollars, it would be scrutinized even more. Since you are not going to be knocking-off any multihulls of the same length, that means that the decision to incorporate the DSS fin is all about the ego. Is that where you guys live in your decision making process?

Henny, if you knew anything about me and my design work, or my approach to modern thinking, you'd discover that I do invite new concepts in design, especially when it comes to boats. What I do not embrace, is a dramatic rush to a new source of technology when it has not been proved functionally AND it adds unnecessary complexity to the genre.

Isn't our world already complex enough for you? At some point is not a significant aspect of the designer's craft a need to resist the rush to ever more complexity and, instead, seek out creative solutions that are, at once, simpler and ultimately more effective for the end user?

Isn't it thoroughly amusing that you guys wish to add more and more stuff to a monohull in order to extract some hope of being able to sail as fast as does a multihull without any of the tricked-out devices that invite problems of a wide variety of types?

You refused to answer my position: That even if you included one of these DSS devices on your 30' monohull, you'd still be defeated convincingly by a whole host of 30' multihulls that are already on the market, starting with the comparison to the Seacart 30. If you really want to look into it seriously, I'd also be willing to bet that a large collection of smaller multihulls could also do the same thing. By refusing to address the issue placed before you, I can only conclude that you have no substantive answer that could come close to winning the point and that you are submitting.

I'd suggest that you guys cease adding more and more crap to your boats so that you can, hopefully, compete with what is already out there in the marketplace, as if it were some mystical pathway to the future, open to only you. All you will end-up doing is overly complicating the design process, exposing yourself to a significantly larger catastrophic failure regimen and increased maintenance and operating expenses for what should be a fun, albeit slower, boat.

[Doug Lord]

FACTS:

Questioning other people's expertise while providing no evidence of his own expertise, education or successful full-size boat building results is a regular negative tactic employed by Mr. Lord. Mr. Lord claims to be an expert on scientific issues relating to foiling, but exhibits NO evidence of personally foiling on one of his own designs.

===========================
You are an outright liar and more than that you do what you accuse me of all in an attempt to besmirch the name of a well known ,proven Naval Architect(Hugh Welborn) and his tested and proven DSS system. You associate his name with Madoff in the 50 billion dollar ponzi scam and raise questions about
his system that have been fully dealt with on two different sites that you have been referred to. You ,apparently, cannot carry out a discussion without attempting to PERSONALLY DISCREDIT anyone who holds a view other than yours. Pitiful!

[bistros]

===========================
You are an outright liar and more than that you do what you accuse me of all in an attempt to besmirch the name of a well known ,proven Naval Architect(Hugh Welborn) and his tested and proven DSS system. You associate his name with Madoff in the 50 billion dollar ponzi scam and raise questions about
his system that have been fully dealt with on two different sites that you have been referred to. You ,apparently, cannot carry out a discussion without attempting to PERSONALLY DISCREDIT anyone who holds a view other than yours. Pitiful!

Doug:

Go back and re-read the post. I indicated that reputation CAN BE fleeting. Nowhere did I indicate Mr. Welborn's reputation was in question. The association of Mr. Welborn and Mr. Madoff was made by you, not me.

Nowhere on the websites listed was data presented, analyzed or conclusions reached. You confuse Internet promotion with scientific evaluation.

Merry Christmas! I hope Santa Claus is good to you and your friends and family.

[Boston]

hate to interrupt the party
but I have a question about dynamic stability

I recently found a set of prints for a friendship sloop "Black Star"
and was wondering
why is the center of lateral resistance so far behind the center of sail area
thanks
B

[Timothy]

Did not a multihull begin as a momo hull with the added complexity of an out rigger.

[Chris Ostlind]

Great question.. so, let's turn the idea around 180 and ask if monohulls did not come from the inherent stability of a multihull way back in the dawn of time? As long as we're talking on a thread about stability, that is.

GOOGLE will set you free, Tim. Enter Tamil and Catamaran for one search and in another, enter seafaring and Polynesian. That should get you rolling.

What I suspect you are going to find is a Western-centric viewpoint as to the evolution of boats as used by mankind. There is quite a bit of evidence that ancient civilzations, such as the Harappan culture of the Indus valley were actively trading along the coasts of the Middle East, Africa and all the way to China, as far back as 4000 B.C.

When you couple this reality with the fact that the term catamaran is a word evolved from the Tamil (an ancient part of the Indian sub-continent cultures) Kattu and Marram, you begin to see the truly ancient establishment of the multihull type, be it two hulls or three. Here is a description of the development of the genre, as it might have taken place many thousands of years ago.

"The concept of the catamaran is indeed ancient.
The word catamaran comes from the Tamil word “kattumaram”,
meaning tied wood. Indeed, in ancient times the word was used to describe a raft made of logs or boats lashed together.So it is quite likely the concept of twin hulls came from the Indian continent.

Parava or Paravas, also known as Bharathar, Paravar, Meenparavar and Fernandos, is one of the oldest Tamil castes.Paravars had traditional sea based professions, such as pearl-diving,
fisheries, navigation, salt making, etc., The catamaran was the invention of the paravas,a fishing community in the southern coast of Tamil Nadu, India.
They could stay at bottom of deep for many hours (hmm..are these people employed in Navy as Divers? I don't think so)
Their engineering skills in ship-building in the olden days were profound.
Thousands of years ago, Tamil fishermen discovered that when they tied logs,hollowed them and made the logs pointed, they had at their disposal a vessel far more stable and nimble than an ordinary canoe:
Thus was the catamaran born."

You can make of it what you wish, recognizing the obvious ancient connections, or simply ignore the potential and maintain a comfortably western take on how it all took place; this business of boats meant for the business of, as well as pure sport of, sailing.

[Timothy]

I have read that the only reason that the west did not embrace the multi hull is because we are trammeled by what is termed a cultural imperative. private property, and hence the need to transport it and protect it. Large whale bodied hulls although they cannot sail well .can carry copious amounts of goods and cannon.

[Bertil]

It seems this tread turned out to be a disc comparing monos with multis. I don't mind, cause that is interesting too.I still have a believe that the weight of monos with leewaywing is narrowing(perhaps beeing alike) a multi with the same accomendation,(not a racermulti with only amas and a net between the hulls).
Take for example my 40-footer (width 4,5m) bulit in 2001, with a deep keel weighing 800kg and a total weight of 5200kg. I think a 40-foot multi with accomendations weighs about the same. If we produce my hull today with modern material I think you can reduce the weight on that monohull with 1000-1500 kg. Remember all weight the multi need for connecting the 2 or 3 hulls.
Then the potential for speed will be at least the same as for the multi as long as it sailing on at least 2 hulls.
And you get rid of the disadvantages with the multi as can suddenly turnover, space in harbor, wet area with 2 or 3 hulls compared to 1 hull, expensive to build and the jumping movements.
I have had multis my self, a catamaran 40feet, and 3 tris up to 30feet. And what I did not liked when sailing alone especially with the cat was the feeling of loosing control/risk for turning when it was windy here in Sweden between the islands, where suddenly the wind comes from shifting directions.

[Chris Ostlind]

Bertil,

Please name the designer, manufacturer and model of your boat.

[bistros]

It seems this tread turned out to be .....

Actually it has turned out to be another thread almost destroyed by Mr. Lord, where his unbridled, irrational obsession for all things foiling has turn attention away from your interest in modifying your boat and increasing performance.

The speed potential for two boats, one a catamaran and the other a monohull is not the same at the same displacement. The effective increase in waterline length of the catamaran leads it to a much higher hull speed in displacement mode. Reducing the weight of the monohull - even significantly does not mitigate the difference in effective waterline length.

Facing reality, when comparing similar monohulls to catamarans, the cats generally win hands down on performance issues.

They don't always win on many other accounts as you have pointed out.

From a distance, you appear to want to increase performance of your boat.

Adding the DSS-style foils may help, but there are many questions that should be asked & answered first. This is not like a bolt-on Nitrous Oxide kit for a Honda 4 cylinder sedan.

1) Is this particular boat the right choice to modify, and can you afford the risk to the boat and it's resale value in it's current condition? A 40' boat built in 2001 as a heavy displacement hull has got to be worth a fair amount. Cutting the hull to add a hull-wide daggerboard trunk is serious surgery with a lot of risk.

2) Does the outcome of the "Leeway Wing" modifications have enough potential for success to meet you goals in terms of performance and value? I know you've done some preliminary calculations, but if the modified boat does not keep up to the multihulls will you be disappointed?

Personally, I'd rather do a small scale experiment on a much cheaper hull than roll the dice on a 40' boat that may be valuable. Time is your friend, and waiting to see if the DSS system succeeds for other people reduces your risk dramatically. Out in front of leading edge technology is the bleeding edge, and sometimes it pays to let others do the bleeding.

I'd consider paying a professional Naval Architect / Professional Naval Engineer to review the design changes proposed - if your ideas are sound, you've got a written third party opinion that will be required for insurance & survey purposes. If you ideas have problems, it is far better to have them pointed out before money starts flowing.

My preliminary thoughts are that an appropriately sized DSS foil solution for your boat is going to require hydraulic (or similar reliable) actuation and control system development. This indicates to me that some type of reliable power source is going to be necessary to run the pumps. Much as Mr. Lord fails to understand, the DSS foils are highly loaded when the boat is moving, and you have to deal with that load to tack or gybe.

I also believe that IF your boat can have weight reduction done, the worst place to remove weight is the keel bulb - you have indicated it is a heavy boat, but the best place to have weight is in the keel bulb. I would look at every other option before reducing keel weight. You want your boat to fail safely if the DSS system was broken on a fishing buoy you failed to notice.

Best of luck with you decision making process!

[Paul B]

Objective evaluation of sailing design innovations is the point of this web site, not unquestioned promotion of sales and marketing material. I'd rather see serious peer review of technology, along with the hard questions and solid answers than biased cheerleading and zombie-like promotion of every new idea.

I would welcome Dynamic Stability Systems response and frank discussion about their concepts. I'm certain that they have encountered many of the issues raised here, and have most likely anticipated and dealt with these problems.

Agreed. There are some here who glom onto every piece of marketing and act as if it is gospel.

I noted the DSS folks had their site go live and did the rounds "selling" their idea for a couple of months earlier this year, then nothing.

It seems they claim a Boatspeed 23 was fitted with their system. How has that boat faired agaist similar "standard" BS23s on the racecourse? It seems a good practice would be to fit the system to a known entity (BS23 or other) and then sail it in all conditions and on all points against a control to determine the validity of the new system. Scientific Method or somesuch?

Wasn't the Druggie all fired up about a canting keel Melges 24 a few years ago? Didn't the folks running that project also shy away from direct comparisons with a standard M24? Wasn't it later shown that the stock M24 was faster?

How about putting the DSS system on a M24 and racing in a major regatta against the fleet? That might prove something.

[Hansen Aerosprt]

From personal experience, there are problems. Foils only work when they are moving appropriately in their design envelope. In the mid-'70s, I built a foil-stabilized speed record craft using an FD hull, a crossbar with adjustable AOA T-Foils (one pulled down and one lifted) and a semi-rigid wing similar to Ilan Gonen's. It was very fast and stable underway right up to the point of tacking in strong winds at which point it capsized irrecoverably. 6 hours in the water and a night in the hospital with serious hypothermia sorta 'cooled' us on the idea.

[Bertil]

To Chris:
The boat design is ONE 40. You can see it on the net ( I have the yellow one) thats on the net. Designer is Guy-Christer Lönngren from Finland. He also designed the Guy-boats, mostly as mine with a keel that is by hydraulics possible to fold backwards. I have the mast to coal-fiber, standing rig is dynemaa, and a lot of other things.
To Bistro: I will be back with some answers. Just now wrapping christmas gifts.

[Chris Ostlind]

The boat design is ONE 40.

Bertil,

If you had told us from the beginning about the specific boat you have, it would have solved a whole bunch of my concerns from an aesthetic and design philosophy position. The ONE40 is very much for an owner who is already thinking outside the box of the typical norms. I'm sure the boat creates new conversations wherever you may go. I see how the DSS system might appeal to an owner who has invested in the design aesthetic of the ONE40.

From a technical standpoint, I both admire the swinging (fore/aft) keel form (especially for the waters in which you probably sail) and I have very serious concerns about the use of the DSS foil in combination with the swinging keel.

Let’s say you were to be sailing along at a fast pace, and encountered one of the many thousands of underwater formations that dot the archipelago environment of, say, Stockholm. Let’s further assume that relied on the DSS foil to provide your righting moment security. I think you could be in for some really interesting problems. This is especially true if you are considering the business of shaving weight from the existing swing keel of your boat.

What if you were banging along at 15 knots and the lightened keel hits a fixed object below the surface? The keel will fold-up to absorb the contact, as designed, and the reduction in righting moment will be considerable. At the same time, the boat will slow noticeably with the contact. This slowing, combined with a lighter RM weight of the keel, which is in a fully retracted status, will reduce the fixed righting moment to a very small number.

The slowed vessel will also not get as much lift from the DSS foil with the reduced speed and the whole boat will want to lay over on its side, as the wind will not change at all in this encounter. This is a position from which it will be difficult to recover until the keel drops to its fully deployed condition. A further delay in recovery will take place due to the lightened keel, even when it returns to full deployment. A whole complex series of actions will then be necessary to restore the boat to an upright condition. In the meantime, the crew and you will be scrambling to stay on the boat, as it will be over hard on its ear.

These are not the kinds of sailing qualities that I would want while out sailing with friends on a warm Saturday afternoon. You'd likely not see them again for another sail, as the above process could be very disruptive for the casual, or non-sailors among your friends.

Bill (Bistros) is much better at describing the physics of all these actions, as he is an engineer by trade. Let my description serve as the pragmatic, real world conditions that you could face should this type of scenario become a part of your summer sailing experience.

If you do go forward with the alteration to the DSS foil system, I wish you all the best in your sailing experiences. I hope that something like the event described above, will not become a process which you will experience often, if at all.

Best regards,

[Boston]

interesting thread guys
Im surprised no one mentioned the KISS principle yet
keep it simple stupid

[bistros]

To Chris:
The boat design is ONE 40. You can see it on the net ( I have the yellow one) thats on the net. Designer is Guy-Christer Lönngren from Finland. He also designed the Guy-boats, mostly as mine with a keel that is by hydraulics possible to fold backwards. I have the mast to coal-fiber, standing rig is dynemaa, and a lot of other things.
To Bistro: I will be back with some answers. Just now wrapping christmas gifts.

Very interesting design - obviously done by an artist with more of an eye for beauty than a lowly industrial designer with utilitarian low cost in mind. More Anna Sundstrand than Magnus Jaderberg to put it in Swedish terms.

Hard to admit it, but I fall more into the utilitarian industrial design side. I'm pretty function oriented, and physical beauty is an accident of functional requirements for me. I appreciate the functional swing keel, given your location.

If I were fortunate enough to own your boat, I would find it very hard to take a reciprocating saw to it and lessen the beauty in the quest for 4-5 knots more speed. It is certainly possible to make a classic car much faster, but then it is no longer a classic car. I can't imagine adding lateral foils for performance doing anything but reducing the long term value of your boat. And you would probably not attract any more beautiful women to go out if the boat was 10% faster.

If you want speed, you can buy & tinker with a much faster boat for far less than what you can sell your boat.

--
Bill

[Bertil]

To Chris:
If I get aground or pump up the keel it doesn't affect rigthing moment so much. When keel down it stands for 11% of the rigting moment, and with keel up for 6% of rigthing moment. The main part of righting moment comes from the wide hull 4,5m and the Bwl 2,85 when not heeled. When going fast using the wing it will decrease even more.
To Bistros:
-From my answer to Chris you can see the the designer hasn't only been thinking on designbeauty.
-I willnot destroy the looks of the boat mounting the wing, as when it is deployed only the outer end of the wing will be seen from close distance in plane with the hull. I will paint it yellow as the boat.
-Inside you will not see the wing as it is with its "garage" under the floor. So
I do not think it will decrease the resale value.
-I think the hull in GRP is a bit heavy for sailperformance as a multihull on all wind directions. But a hull of coalfiber would be 1000-1500kg lighter, then I think there will be a match. Think about that the boat with wing beeing ligther the faster it sails. The multi will have the same weight whatever the speed.
-Perhaps there will be nessasary with hydraulic to move the wing. (I have that onboard for the keel). But perhaps it will slide over by its weight when you tack. In both cases I will have control and I do not know how to put on the hydraulics or ropes as the garage is always filled with water. Ideas how to do it ???

[Doug Lord]

Why don't you make a deal with Hugh Welborn and take advantage of all their experience?

[bistros]

To Chris:
In both cases I will have control and I do not know how to put on the hydraulics or ropes as the garage is always filled with water. Ideas how to do it ???

I've done a little thinking about this. I envision a small stuffing box in the middle of the top surface of the "garage", making a shaft access into the boat hull. The drive shaft I see having a small toothed gear on it inside the garage, fitting down into a geared slot lengthwise in the top of the movable foil. Turning the shaft one way moves the foil to port, reversing the shaft moves the foil to starboard. This could also simplify installation/removal and calibration if the gear could pull up into a recess in the garage top.

I like gear drives because there is no unpredictable motion, no driveline losses and they can be very positive and the gear ratio is easy to adjust for both speed and strength. You could drive the shaft easily via a hydraulic pump, or via a manual crank handle if the hydraulics fail.

I hope my description is adequate to create a picture in your mind!

--
Bill

[Henning P]

Hi Guys,

Now we start to discuss serious matters, I´ve got a boat similar to Bertils.
Still under construction, Engine and steering ready, boat get 9 knots with 39 hp diesel. 5200 kg displacement It´s an easy driven hull. Rigging is the job right now.
Carbon rig and Gary Hoyt jib boom is waiting to be installed

My experience with folding keel is that I´ve been sailing Guy Christer Lönngren boats since 1986 all with this feature. Hit ground couple of times each season. No damage to boat structure or dramtic action on board.
Only minor deformation of lead.

You can visit www.guydesigngroup.fi

The reason is that the hydraulic cylinder got an overflow valve and act as a shock absorber. I´ve never been able to get the keel to go all the way up before the boat stops or passes obstacle.

When stop, sails down, start engine and reverse from where you came,
nothing dramatic, but a bit embarrassing.

The benefits are low draft when needed, shallow water in secluded bays, and high AR when sailing.

So I´m not unfamiliar to technical stuff onboard, including everything needed for comfort living.

What we need is qualified assistance for profile of wing and working mechanics for deploying and retraction.

This was what I was expecting from this forum.

[bistros]

Why don't you make a deal with Hugh Welborn and take advantage of all their experience?

Mr. Lord does make a good point here.

As I have stated before in this thread, I'm certain the DSS folks have encountered and dealt with many of the issues raised here. It would cost you nothing to contact them and inquire about costs, and also to obtain references of people who have had the DSS technology in use. Talking to existing paying customers is going to provide better feedback that you are going to get here from people (like me) theorizing. Paul B.'s comments regarding head to head performance of DSS-modified one design boats versus unmodified hit the target perfectly.

I do believe that the DSS website and subsequent marketing articles may not be frankly discussing all the negative issues with the technology.

I'm concerned about the loads on the horizontal foil - these loads may be very high, and also may be cyclical with out of cycle spikes in load and unload. It would be interesting to see data from load cells over time. Basic boat design acknowledges the design strength necessary for keels - this technology may require similar strength and structural engineering - which may be difficult to do adequately on a refit of an existing hull.

The DSS site indicates their "fail-safe" strategy is to engineer the foil to break before the "garage" or horizontal daggerboard trunk is damaged. A fully powered-up boat, with reduced effective displacement (due to DSS foil lift) may react violently to a foil failure - and the missing righting moment from the DSS foil may allow a complete knock down and swamping.

Welborn and company are the first place to start asking questions. If you get answers, please post them here!

Given the basic configuration of the concept, it certainly may be possible to test function using a deck mounted lateral foil as an experiment. This is probably how Welborn did his first experiments - trying a leeward foil without damaging the boat permanently. If a horizontal foil is going to provide benefit you would see results immediately. You could also quantify loads with load cells measuring the deck mounting points.

You could do a $4000 experiment that would give you a good idea about what to expect without damaging your boat unnecessarily.

--
Bill

[Boston]

http://www.dynamicstabilitysystems.com/

[Bertil]

I have got in touch with the inventor, and he will help us. When things begins to happen I will report on this forum how it developes. Thank you all for your interest!

[Boston]

keep us posted please
that thing was pretty cool

did anyone do any time trials with identical boats
one with and one without

[Doug Lord]

I have got in touch with the inventor, and he will help us. When things begins to happen I will report on this forum how it developes. Thank you all for your interest!
=============
Bertil, I'm very glad to hear that! Best of luck!

[Bertil]

Some things has happened with the so called lee-wing:
-A mailing between me and the inventor have been going on since I last wrote here. We also met at the Mets in Amsterdam last year where the inventor Hugh Welbourn showed a prototype.
-Hugh have tried it on a 27-footer with a leewing on one side. He have also tried ii on a 30-footer "Drinks Trolley" (see the net), and last spring a retrofit on a 38-footer.
-The results is closedhauled an increase in speed of app 5%, and when reaching 30-40%.
-The boat gets more stable in waves and feels as appr 30% bigger, and heeling 5-6% less. So it is very nice for cruising too.
-On the 38-footer the wing were mounted too near the bow of structural reasons and a new problem arised. When closehauled OK as expected, but when reeching the wing didn't work. It was disturbed by the bowwaves and did not work.
-My question to this forum is now:
Where to place the wing to avoid this?

[Perm Stress]

Why not to ask Hugh Welbourn? He is in the best position imaginable to answer this question.

[Doug Lord]

Some things has happened with the so called lee-wing:
-A mailing between me and the inventor have been going on since I last wrote here. We also met at the Mets in Amsterdam last year where the inventor Hugh Welbourn showed a prototype.
-Hugh have tried it on a 27-footer with a leewing on one side. He have also tried ii on a 30-footer "Drinks Trolley" (see the net), and last spring a retrofit on a 38-footer.
-The results is closedhauled an increase in speed of app 5%, and when reaching 30-40%.
-The boat gets more stable in waves and feels as appr 30% bigger, and heeling 5-6% less. So it is very nice for cruising too.
-On the 38-footer the wing were mounted too near the bow of structural reasons and a new problem arised. When closehauled OK as expected, but when reeching the wing didn't work. It was disturbed by the bowwaves and did not work.
-My question to this forum is now:
Where to place the wing to avoid this?

=========================
If I were you I'd ask Hugh Wellborn as PS suggested. Alternatively you could PM Vlad Murnikov who is using a very similar foil on his Speed Dream Prototype and is working with Wellbourn. Wellbourn has done the full size and tank testing necessary to answer your question-nobody here would have any better knowledge on this particular innovation. Good Luck!

PS- do you have any more info on the 38 footer-a link perhaps?

http://www.boatdesign.net/forums/sailboats/speed-dream-35-prototype-36205.html

http://www.boatdesign.net/forums/sailboats/hugh-welbournss-dss-25-a-32138.html

http://www.boatdesign.net/forums/sailboats/dynamic-stability-systems-imoca-approves-34317.html

[Bertil]

Sorry, but the problem comes from Hugh and he has not solved it. We need to have someone who knows how waves behave near the hull from hull out to app 2m.

[Doug Lord]

Sorry, but the problem comes from Hugh and he has not solved it. We need to have someone who knows how waves behave near the hull from hull out to app 2m.
========
Is it a displacement hull?
UPDATE: I've found out that there is a problem with this boat but just so there is no confusion it is not a Welborn design-it is a retrofit. I'd be interested in more detail Bertil.

[Bertil]

It is an displacement hull. I have got some ideas of how to solve the problem and will count on it and will be back here on the forum when I,m ready.