Dinghy Design: Open 60 influence?

Magnus:

Proof is found in real world sail-able examples of boats. Not in theory, not in conjecture and not in models. The Weta mentioned is a real production boat from New Zealand, sold throughout the world to real people who both love the boat, as well as see far more potential in the design. I've embedded a link to Weta Marine above.

Directly from Mr. Lord's own posts, the elderly "Tantra" design had ONE example made, and it was destroyed a few years ago. This example did not include the curved lifting foils discussed here, and discussions of this new "Tantra II" design are just conjecture - not demonstrable fact. This design may or may not prove effective, it must be built and tested to determine any conclusions.

You may have the impression these discussions are about active designs being built. Many of these discussions are just talk although the people involved indicate progress is being made, no tangible boats ever emerge from the discussion.

Don't take my word for it, or anyone else's for that matter. Directly ask the proponents of the designs for a list of people owning the boat that you may contact for reference purposes. There is a large amount of Weta owner discussion on Sailing Anarchy, and many of the people who are enthusiastically trying to tune and enhance the boat are present on the forums there. Search for posts by "Vegas" (a member) on Sailing Anarchy.

A couple hours of Google time will quickly sort out the fantasy versus reality of boat designs discussed here. A former member here (who was problematic to many members) did a home build Weta-style design which was presented here and on Sailing Anarchy. I can't attest to whether or not the design was built or any reports from it, but it may be a starting point if you wish to build a similar design yourself. I had no personal problem with this person (I got along fine) but he's left this forum and subsequent contact reports he's happily spending far more shop time and building boats.

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CutOnce

 

Tantra II/ Curved Lifting Foils

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Mag, none of the "objections" as you put it have any technical basis whatsoever-the individuals involved seem incapable of a rational technical discussion.
The fact is that retractable curved lifting foils are PROVEN to work on multihulls and monohulls. So far as I know no designer has yet incorporated such foils in a dinghy design but there is no sound reason why they cannot be used. If the design is done carefully the resulting boat could be lots of fun and perform better than most dinghies its length. Curved foils have the advantage of very shallow draft when compared to the bi-foiler arrangement on a Moth as well as not requiring an altitude control system like a Moth. The boat would not be as fast as a Moth but would be much easier to sail. Downwind the foils may be able to be both lowered simultaneously allowing the boat to fully fly-but that is 100% controllable by the crew. A high performance version of this concept has a lot of potential.
The Tantra II configuration allows for a lightweight structure in a design that maximizes the RM that the foils can generate while allowing it to be sailed off the beach upwind with both foils retracted. The original Tantra design used molded in ,asymmetric , to-ed in leeboards with removable tips-the new design would have many of the proven characteristics of the original with added righting moment and lifting foils.
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Keep in mind that it took many years for multihull designers to take the chance and try the curved lifting foils pioneered by the ORMA tris on smaller boats. It may take a similar amount of time to see a system like this introduced, but who knows-all it takes is some interest from knowledgeable people. I'd be glad to answer any questions you may have......

Mag, the WETA is an excellent boat and can be readily purchased. New concepts such as the Tantra II and the application of curved lifting foils to dinghies
are not proven as yet but the technology of the curved lifting foils-and the viability of hydrofoils, when carefully applied to dinghy and multihull dinghy designs, is proven. Proven technology applied in a conscientious, intelligent manner to an experimental design is how progress is made but it must be approached from the standpoint that it will require development which can be costly in both time and money. If everybody listened to the excessive cautions thrown out by the "cutones" there would be no foiler Moth, no Nacra 20 with curved lifting foils, no V3 in the lead of the Barcelona World Race with curved lifting foils , no Hydroptere, no windsurfer ,no kiteboards etc.. Excessive caution kills innovation and there are those for whom the mere mention of new technology is anathema-especially when they don't understand it and cannot discuss it.
So if you're interested in exploring new ideas do the research you need to do and understand the difficulties faced by every sailboat innovator in developing new technology. I'll help in any way I can-as will others.


Pictures: rough sketches of just one of MANY versions of a possible dinghy design incorporating curved lifting foils: (click on image)

 

Why, pray tell has the Moth gone to fixed foils and walking the boat out to depth? The "retractable" T-foil proven to be difficult to impossible to retract if the daggerboard trunk was adequately tight to prevent movement when foiling. It basically quickly became apparent to the people actually sailing the boat that "retractable" was a feature that wasn't valuable in light of the performance degradation and control slop introduced. How's that for rational?

Regular daggerboard slots are tight enough that moving the board when under way is difficult to impossible, except when the boat is going very slow and the board is developing little to no lift. Don't believe me? Go try. Curved boards exacerbate this problem as there has to be a matching curved trunk. Basically there are two conflicting design goals - a tight trunk that prevents the board from slipping when developing lift, and a trunk loose enough to allow lifting the board when desired. This is the type of real world compromise that must be reached in making a boat sailable. Rational analysis? I think so.

Shallow draft sailing generally has created the demand for centerboards that can pivot on hitting an obstruction instead of a daggerboard which basically means expensive damage on hitting an obstruction. You increase drag with a centerboard, given the long slot, but you eliminate grounding as a dangerous problem. Grounding a daggerboard boat at speed can be a boat killing experience.

The 1-2' draft advantage gained by curved foils that require a fixed daggerboard style slot isn't worth it to me when compared to a pivoting centerboard that basically removes grounding as a major problem. Pivoting centerboards DO have lower performance at the top end of the scale - but significant performance boats like the 5o5 and the former Olympic two man boat the Flying Dutchman are centerboard boats. No one can call a 5o5 a slow boat.

It really depends on your venue(s) and your definition of high performance. Real high performance demands a willingness to swim frequently, trapeze as a RM solution and lightning fast anticipation (not reaction time - it is too late) of wind changes and shifts.

All these discussions of application of ocean racing technology to monohull dinghies are blue sky for now. Before I'd even consider going down this road, I'd go out and sail a current high performance boat to help decide if you really want that level of speed and the work it entails. If I were you I might post a request on Sailing Anarchy to see if there is a Weta owner in your area that might get you out for a sail - that would give you an idea of what reasonably high performance is with a lower effort level than a I-14 or similar skiff type boat. I'm sure you can find a 5o5 owner nearby as well to get a complete spectrum of experience.

There is NOTHING like doing what you propose in a few different boats to help refine your design brief. Asking experienced sailors you get to know and trust will quickly sort the wheat from the chaff in regards to wild new design ideas. Rational? I think so.

All the above can be summarized as "It doesn't exist yet, may or may not work, and you'll have to spend lots to find answers, even if those answers are not what you really want."

If you are interested in building a proven design that meets a design brief, that is a very different situation than taking on the job of being someone elses R&D department, while also footing the bill. Rational assessment? I think so.

I'm more a fan of breaking large design risk into smaller, isolated chunks that prove or disprove design elements instead of grouping together large amounts of risk. For some reason, Mr. Lord thinks my approach too careful, but I've found that small incremental progress with controlled risk actually results in faster progress than trying to do everything at once. At least my methods work for me. Excessive caution? Don't think so. Lessons learned through scar tissue and experience? Yes.

Make your own assessment of what advice is sensible and will help you reach your design brief. Here is a sample thread that concludes with a boat built to meet the original design brief. Rational? Yes. Was excessive caution a problem? No.

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CutOnce

 

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1) The Moth has not "gone" to fixed foils-they started out with fixed foils. Bladerider offered retractable foils that worked technically but because of the
lack of static stability hooking up the foils and deploying them was too much of a hassle. A design problem not a concept problem: the RS 600FF uses retractable foils successfully as did I on my first foiler. The 16' Rave multifoiler uses retractable foils controlled from the cockpit which work very successfully and even allow two foil positions depending on the depth of the water at the sailing venue. The foils are controlled from the cockpit.
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2) Again, this is a design problem that, apparently, was not solved successfully in Mr. Once's experience. It was solved successfully by Dr. Sam Bradfield on the Rave and Scat-and by Buddy Melges on numerous scows.
Open 60's are regularly sailed single handedly as was V3 (that uses retractable curved foils). Knocking retractable curved foils because of the design failures in some instances is way wrong considering the PROVEN instances of their successful use.
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3) The old anti-daggerboard speel has been around for decades yet they are used now more than ever-I sailed with a daggerboard on my Windmill for years-never once damaging it or the boat. Windmills, RS600FF foilers, Moths, R Class foilers, Mirabaud, the Rave foiler, the Osprey foiler, Steve Clarks Aethon and many ,many more boats successfully use daggerboards. The Tantra II design would successfully use curved daggerboards.
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4) Curved foils are fairly simple to make and install successfully for an experienced tooler-there is no requirement-for any reason-to make them "fixed".
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5) The Tantra II concept design is NOT a "high performance" design compared to what a high performance design using this technology would look like-the numbers reflect a fairly high powered dinghy with a built in cooler and dry stowage compartment big enough to carry a pup tent. It uses sliding bench seats with backrests to make the boat comfortable and easy to sail. Because of the use of the lifting foils including the rudder T-foils and retractable gantry the boat should be very fast compared to other dinghies in the same size range. The numbers show that the singlehanded Tantra II should outperform the standard WETA trimaran.... There is no "performance daysailer" currently on the market with the built in features of the Tantra II and the fact that these features can be offered makes the design unique-not to mention the foils ,ease of sailing, comfort and downright fun such a boat could provide for one or two people.
Now, a high performance version using these same retractable curved foils could approach the speed of a Moth offwind(and maybe upwind) based on the "testimony" of Brett Burvil(who developed the first Moth foiler with three foils) and of John Ilett who both said that if the three foil surface piercing boat (developed by Burvill) hadn't been outlawed it might well have been at least equal to the current bi-foiler with the same level of development. The high performance version of the Tantra II concept has enormous potential.
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6) With all due respect this is just nonsense: curved lifting foils were pioneered in the early 90's on ORMA 60 tri's and in the last few years modern multihull design innovators proved their worth on small catamarans. These foils are not "ocean racing technology"--Foils are foils-lift is lift: if the boat is designed to take advantage of curved lifting foils there is absolutely no reason whatsoever that they wouldn't work. Proper design is everything-nothing blue sky about it:the technology is PROVEN!

 

This video shows the only monohull currently using curved lifting foils anywhere in the world as best I can tell. It should be noted that she is currently 400+ miles in front of her nearest rival.....

http://www.youtube.com/watch?v=anTb2eN0kug&feature=player_embedded


Seems to me that its time for some trickle down!!

 

Sounds so simple.

I'm guessing that it is not so simple in actual practice and that building and properly installing curved foil trunks is very difficult. I also suspect that maintaining definitve clearances for the entry and exit points of the foils is also quite problematic. As a layman, this looks to be a job reserved for extremely qualified fabricators, and not one for the everyday builder in his garage style shop.

When it is that hard to employ and build, I wonder what would be the worth in an overall sense when much simpler, angled daggerboards will work very well and have half, or less, the problems?

I think that this design correction is best left to the Morelli-Melvin types of this world and that the rest of the guys building their own easily constructed boats should be very happy doing it by the numbers with building styles that are quite a bit less demanding.

 

Dinghy Design: Tantra II / curved foils

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I mentioned earlier that curved foils would be simple for an experienced tooler( post 79, #4 )-I don't think they would be simple for an inexperienced first time builder. BUT that depends on the design you're working from as much as your experience level. If an inexperienced designer AND inexperienced tooler tried to do a boat like the Tantra II with curved foils from the design stage thru to building a one off I think it would be a disaster.
I disagree emphatically that angled foils would work well in this case and have "half or less" problems. The characteristics of the constant curve foils are MUCH more suitable to a dinghy design than would be angled foils because it is possible to vary the way lift is generated by moving the curved foil up or down a relatively small amount. That kind of control is not possible with angled foils. Further, the angled foils would have significantly more draft for the same maximum lift.
I don't think the Tantra II type is suitable for an inexperienced builder/designer at all and substituting angled foils would not make it more suitable or easier to design/build. And the performance of the resulting boat with curved foils would be much superior to any version with angled foils.
If you look at the sketch below there would be almost no way to include angled foils with the same lift characteristics as the curved foils. The concept, as I envisioned it, was for a production boat utilizing curved foils or a one-off built by a very experienced builder with a final design done by a naval architect/marine engineer friend of mine and myself.
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I'm begining to think that you're exaggerating the difficulty of curved foils vs angled foils used in a similar application to this. If you are an experienced builder with an excellent set of plans building a boat like the T2 would not be beyond your capability.
I have to stress that using angled foils would most likely be a very serious mistake on this type of boat-they would not function well in this application-compared to curved foils.

 

Reasoning that follows the same logic trail as mine.

Simplify and spend time thinking how you can obtain 80% of the benefit with 20% of the effort. The foils alone aren't going to be cheap - straight, uncurved production aftermarket foils for 5o5s, Fireballs and I-14s range from $1-5000 dollars from vendors like Phil's Foils, Larry Tuttle and Paul Beiker (Russell Brown). Adding even a constant radius curve, using a two part female mold and carbon construction put the foil cost in the $3-7K range plus initial tooling cost.

Once you've got the foils done, you have to construct a male mold for making the trunk(s).

As I tried to get across earlier, catamarans are a different breed - foil adjustment is done while the hull is out of the water - foils are dropped before tacking, and the foil on the "new" windward side is raised after the hull is out of the water - hence there is no lift-induced load and it is easy to move. I've never seen a cat sailor wander over to the leeward side of the boat to adjust a foil while under way at speed - it sure would not be easy. This kind of unloaded foil movement is not possible in a monohull, as the windward foil would not be out of the water like in a catamaran.

If Doug would like to build a set of foils and trunks, he could prove me wrong in a heartbeat. I'd be the first to congratulate him if he made a success out of a dual curved foil dinghy.

I think your reasoning on using straight, angled foils is logical and within the purview of the home builder.

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CutOnce

 

Doug,

Unfortunately, I can no longer represent an interest in this design discussion as I am not a serious lamination expert. I am former professional who worked in areas of cost effective analysis for manufactured goods who has a strong interest in sailing small craft. I am not a man who could turn a complex set of plans into a meaningful, workable and functioning design. I am also not setup financially to approach a local multi-axis router shop with the necessary files to create accurate master molds. The nearest shop to do such work is way over in the Seattle area and they charge a lot for their services before shipping.

I am sorry to say this, but you have succeeded in making this discussion unimportant to thousands of possibly interested members like me because it all implies a level of skill and experience that 99%+ of the members here do not have. I also suspect that a boat of this type will be quite expensive, simply because of the engineering and build requirements to make the critical parts. This is also not for me when it comes to a dinghy of this size from an un-proven design.

Good luck with your expression, but for me and others like me, this topic is of no further interest. I bid you goodbye.

 

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Magnus, there are many designers that design for the homebuilt market and many plans sets available for that market. My concept for the Tantra II is NOT one of those and was never intended to be. What I've tried to illustrate is that there is definitely the potential for "trickle down" of the curved foil technology being used now on the Open 60 V3. The technology may one day be available for the homebuilt market but for now represents state of the art "foil assist" technology that will only be available as a production design , prototype or one-off for a very skilled builder. Before such technology can "trickle down" somebody has to show that it is technically feasible and would be likely to produce a boat that would be an improvement on current dinghy designs. That is what the T2 is the start of: the rough sketches and preliminary numbers indicate just such an improvement and the next step would be to build a one-off prototype.
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I'm not in complete agreement with you on your assertion that curved foils are too complex for a home builder. I'm fairly sure that I've read of a "homebuilder" adding curved foils to an A Class catamaran and your comments have inspired me to try to find that article.
I'm glad that you, apparently, won't pursue the angled foils in a dinghy variant as I strongly believe that that would be just spinning your wheels-while producing a boat that would perform poorly -at best.
If I find the article on the "homebuilt" application of curved foils I'll link to it here. Hope you find the design/boat you're looking for-good luck.
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PS- While such equipment would be nice to have to do a production prototype I can assure you that it is NOT REQUIRED to do a prototype or one off version of the T2 or one like it using curved foils. The original Tantra was built as a molded one-off and had I thought of the curved foils back then they would surely have been included.

 

Doug:

What people are trying to tell you is that Open 60 technology is not a great fit for the dinghy market. Adding two curved foils, along with two curved trunks is expensive, when compared to current product offerings - and homebuilding to avoid cost is not a feasible option for 99% of the people out there.

I personally question the application and effectiveness of the two lifting foils in a monohull dinghy design - but on the theoretical efficacy of that I guess we will have to disagree. My gut feeling is that there will be no net performance gain due to added weight, added drag and added complexity during maneuvers. Your gut feeling tells you (as always) that added weight, added drag, added cost and ease of use issues are not relevant. The only real answer that is acceptable is building one and demonstrating function when measured against a control sample without the curved lifting foils. Once you've built one it is easy to perform cost-benefit analysis and determine if anyone would actually pay X% more for Y% performance increase.

This is where my proposed concept of you buying a 29er (or 49er or whatever) and adding the two foils and two trunks makes sense - you can easily measure your modified boat against the same one design boat without the mods - and quantify results without question. Besides, both boats could be matched in terms of state of tune, rig, sails, crew etc. - essentially a level paying field where results can't be questioned.

Rather than nebulous Internet research-derived calculations using questionable formulas, you could measure speeds, elapsed times for both race legs and overall time - head to head. The numbers you can really trust are those measured on the water.

What do you say, why not prove your proposal on the water? Unless someone does this, the concept seems .... dead on arrival. This is much cheaper, faster and reliable than incorporating untested concepts in your modified aeroSKIFF hull.

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CutOnce

 

Dinghy Design: Open 60 influence? / Tantra II

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1) The comments I've received from people I respect a great deal are 100% positive regarding the potential application of curved foils to dinghy design.
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2) It's important to understand the nature of the foils to know how to apply them. In order to use the curved lifting foils so that they will give maximum benefit they have to be applied to a dinghy designed specifically for them. The idea of taking two equal boats like 29'ers or 49ers and replacing the normal foils on one with curved foils is a formula for failure of the curved foils since all their advantages are not being exploited. The T2 uses the foils in a manner that allows a fairly narrow ,low wetted surface, lightweight hull with the foils deployed in such a manner as to allow them to ADD to RM not subtract from it like they do on catamarans and trimarans with curved foils. This is critical for both the handling of the boat and the performance of the boat. The suggestion to use two identical boats not designed specifically to use curved lifting foils evidences a failure to recognize the nature of these foils and how they can best be used in a dinghy design.
But I appreciate your suggestions as to how to spend my money but I'd rather
see a prototype designed and built that uses the curved lifting foils in the best possible way to illustrate their value in dinghy design. I think the Tantra II is probably a good choice for a proto because it is not the highest performance design possible using curved foils but , rather, is a "performance daysailer" that will perform very well while still being able to provide "amenities" for daysailing like a molded in cooler and dry stowage compartment big enough to carry a small tent. Further, it illustrates how a boat using "foil assist" can be more that just a performance machine-it can use innovative design to bring much more to the table: an easy to sail, beach sailable, shallow draft dinghy capable of excellent performance in a wide range of conditions while offering comfort not available in any current boat capable of the performance of the T2.
It's an exciting concept that has a great deal of potential.

Pictures: left-the well proven original Tantra design that was test sailed for over 5 years by itself and against US 1's(Windmill derivative). Right- a rough sketch of the Tantra II sail plan and an illustration of how the curved foils would be set up(deployed and retracted)-see previous posts(or my gallery) for more----

 

Yes Doug, I know you have no respect for me. I did not write my posts in this thread for you - that is pointless. I wrote my posts in this thread for other readers to provide balance.

Over time, I've come to believe the opinions I should consider carefully are those that have different views on things than I - people that easily agree with me are not worthy of review - as I already understand their position. It is the things I do not understand that are worth review.

Doug, you completely miss the point of research and quantifying things. Unless you have a control to measure against, you have no idea whether or not a design idea is actually beneficial. By putting the technology in a completely new hull, without having an example of the exact same hull without the technology as a baseline, you eliminate the ability to objectively evaluate the performance of the concept against a control group.

If you idea is worthwhile, using an existing one design as a baseline will allow immediate and unquestionable evaluation in a fast, cost effective manner. By reducing the variables to ONLY your new technology you get to see how the concept either stands up or fails to meet expectations - measurably.

Once you have quantifiable data driven results from which you can draw scientific conclusions, then you consider NEW applications of the technology. Putting a new, investigative technology in a completely new platform, with multiple new technologies in play at once eliminates the potential of knowing exactly where performance increases and decreases come from. It's called science. Given your love of people that you respect, if you look at Hugh Welbourne's research, he modified known designs and measured against unmodified hulls. Frank and Julian Bethwaite take the same approach. As do all serious researchers.

More random pencil sketches and pictures of long gone unsuccessful designs are pointless. One-off designs with no duplicates to use as a control are pointless in terms of evaluating research. You have to compare apples to apples, not apples to grapefruit. If you are aiming at a beach sailed daysailor, then change my suggestion from a '9er to something that fits - but start with a known entity.

If this is just talk, and you have no intentions of pursuing any substantive research into finding out if this concept actually works, why don't you just say so. If you are serious, ask the people you respect to read this post and tell you where my logic is wrong. They will all tell you it makes sense if you are serious. And they will encourage you to follow the advice if you want to get measurable results in a cost effective, timely fashion.

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CutOnce

 

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1) What you fail to understand is that there is no existing hull that I believe would illustrate the potential of this design concept. I'm afraid that you're stuck on finding out whether the foils work or not. I'm not -I know they will work and demonstrating their effectiveness in a boat designed specifically for them is the best way to proceed. The resulting prototype can be(and would be) raced against other boats in the same size range with similar capabilities. But there is more to this than you appear to understand: the foils permit the boat to carry more sail area than a conventional design which is one of the most important reasons to build a prototype. Further, the foils allow a unique type of boat that can have features no other boat of this performance capability has. To illustrate the full range of innovation in the T2 nothing would be suitable but a purpose designed prototype. Once the prototype proves satisfactory a second prototype would need to be built to fully refine the design. In my opinion this is ,without a doubt, the best way to develop a concept like the T2 with the exceptional level of innovation present in the design.
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2) This is an exceptionally obnoxious comment. Originally, I wanted to illustrate the fact that I believe that the use of curved foils(similar in concept to those used on the Open 60 V3) IS viable for dinghy design. I believe the rough sketches I have shown-which are not random- have illustrated the potential I wanted to show. They are just conceptual illustrations which fairly accurately capture the essence of the concept.
Using the term "long gone unsuccessful designs" to describe the original Tantra is insulting, completely uninformed, and shows the abysmal level of your discourse. You have shown, repeatedly, that you are willing to make completely uniformed comments about things you don't understand-and that is pretty much useless.

 

Doug:

1) Does it still exist? If not when was is destroyed? Years ago? If so, then it is long gone. QED.

2) Was it a success? How many were built? If more than one I apologize. If not, then it was not a design success. QED.