Dinghy Design: Open 60 influence?

[Doug Lord]

Dinghy Design: Open 60 influence? T2 curved foils

Below right is a rough sketch that shows a straight ,angled board compared to the curved foil being designed specifically for the T2 application. The angled foil(45 degrees) requires more area to develop the same or close to the same vertical lift* but it also requires the boat structure to be 3 feet wider and when retracted on both sides the beam of the boat increases 8'(!). When fully down the straight angled foil draws 8" more than the curved foil.
The angled foil will always be developing some vertical lift even when you don't want it no matter how much it is retracted-the ratio is always 50% lateral resistance-50% vertical lift. As you may be able to see on the "segmented" curved foil sketch, the curved foil can be retracted for light air, non- "foil assist" conditions to the point where approximately 90 % of the foil area is used just for lateral resistance, not lift. Additionally the lift profile of the curved foil is infinitely adjustable in small increments which is impossible with the straight angled foil. Note that what is adjusted, with the first 40% or so retraction of the curved foil from max deployment, is vertical lift-little to no lateral resistance is reduced as the foil is initially retracted. This incremental adjustability of vertical lift is one of the major advantages of the T2 specific curved foils.
The curved foil does not add any beam to the boat when retracted and could probably be trailered with the boards retracted.
Curved foils offer quite a bit of design latitude in tailoring them to a specific application. The T2 foils are matched to the characteristics of the boat allowing a range of adjustment from max lateral resistance- no vertical lift to max vertical lift and max lateral resistance. The boards will be able to be deployed for the specific conditions in a way that maximises their lift/drag ratio and improves the overall lift drag ratio of the boat.
--
The T2 has a unique design-not seen in any other dinghy anywhere- as best I can tell-that tailors the design specifically for the curved foils with enough beam to allow the foils to generate righting moment in addition to lateral resistance and vertical lift. This results in a unique hull shape suitable for adaptation as a "performance daysailer" or in a modified version as strictly a high performance dinghy. Because the foils develop vertical lift outboard of the hull CB(displacement or dynamic) they also add substantially to the Righting Moment(RM) of the boat increasing the power to carry sail significantly over a boat not having a design capable of maximising the use of the curved foils.

* Note the flatish area on the curved foil when fully deployed. It takes twice that area for the angled foil to even be comparable to the fully deployed curved foil. In addition, the angled foil is shown at 45 degrees because that is the best compromise between vertical lift and lateral resistance. Both the curved foil and the angled foil could conceivably be pivoted about a fore and aft axis so that the head of the foil can move inboard or outboard. That is probably not necessary on the curved foil since the lift profile can be varied so easily by incremental retraction from the max deployed position. Pivoting the angled foil to gain what can be gained in a normal T2 specific curved foil installation would be complicated and even then would still not be very satisfactory.


Pictures: left-segmented lift of curved foil. right- comparison of curved foil to straight angled foil.

 

[Doug Lord]

Dinghy Design: Open 60 influence? / Tantra II Summary

The Tantra II is based on a lot of work when I first started this thread and was looking at reverse curve foils(see post 10). I was looking at the original Tantra that I designed, built and sailed for years starting about 34 years ago. It was a unique concept then with the very functional molded in leeboards. I was looking for a good way to get the reverse curve foils even further out. As I did more research and heard from some foil experts including Greg Ketterman I realized that those foils probably wouldn't work too well-or at the very least would require substantial experimentation.
Looking back at the original Tantra planted a spark and I tried a combination of "normal" but much tighter curved foils as described earlier-they look real good from a technical design perspective and I think an updated version of the Tantra-T2 is an ideal platform to allow these foils to be exploited to the utmost in a monohull dinghy.
You can see pictures of the original Tantra next to rough sketches of the new concept ,T2, in post 66.

 

[CutOnce]

We get it.

Doug:

Best of luck going forward. I hope you get to actually foil in one of your designs before the clock runs out. Tick tock. Best picture I could ask to be posted would be you fully foiling with a smile on your face. Tick tock. Go do it.

--
CutOnce

 

[Munter]

OK - so the storage issue was just a red herring? In my view the level of innovation here is debatable. I still see a boat (with dry stowage) that is stabilised with high aspect bruce foils (and bouyancy pods). I saw pictures of something like this in AYRS journals from back in the 60s.

You make the interesting claim that a straight foil requires more area to develop the same amount of lift as a curved foil. How is this so? A horizontal foil will generate more vertical lift that a curved one while a vertical foil will generate none. Frankly, I think neither of us have a detailed understanding of the properties of curved boards but I invite you to provide some form of evidence to back up your statement. The ratios you have quoted seem to use an arbitrary selection of 45 degrees as the angle. Different angles will give different results. You have suggested earlier in this thread that a complex case could be used to adjust the angle of a curved foil so why can't the same thing be done with a straight foil to bring about the same result?

Beam wasn't raised as an advantage until it came up in the last couple of posts in this thread and it seems like a marginal issue. Beam has never been a concern of yours in the past if I correctly recall the proposed 16 foot wide 11 foot trimaran you were previously frothing over. In any case, there is no additional beam in the case of L shaped foils. At best, this is a peripheral issue and probably most pertinent inside class rules where beam is limited (ie A class). Your own sketch in post 100 seems to show outriggers well outboard of the leeboards already so it seems there is some room here.

Claiming that because scows and Open 60's can retract boards from tack to tack doesn't seem relevant when AFAIK the scows are using the well established and simple technique of pivoting centreboards and the Open 60's use mechanical assistance to raise boards and presumably don't tack much more often than once every couple of hours. The boat you are proposing would presumably operate completely differently to these so I don't see that they help substantiate your case.

L shaped foils also give you the touted "infinte adjustment" of lift vs leeway resistance through the adjustment of the leeway resisting area. I recognise that in light air the curved board give you the opportunity to have vertical area only and that this removes the drag associated with the lifting foil but is this always what you want? What about at the other end of the spectrum when you might be looking to get rid of leeway resisting area? For example, in heavy air you may wish to reduce vertical area without reducing lift and with the curved foil configuration this is not possible.

 

[Doug Lord]

Dinghy Design: Open 60 influence? / Tantra II

Basic design thinking of T2:
1) The entire concept of a "performance daysailer" is relatively unique. The Tantra II represents a type of performance monohull daysailer never seen before since it uses foils for lift-"foil assist"- on a boat that has a molded in cooler and molded in dry stowage. The boat uses a sliding bench seat for fast, very comfortable movable ballast(crew). Because of the curved lifting foils ,and their placement due to the unique hull design, the boat can carry more sail area than it could without them. The unique rig features a square top main and square top "ribbon jib" that allows for an exceptionally powerful sail plan with the CE lower than equivalent "normal" fractional rig. The rig would also permit the use of an asymmetrical spinnaker. The boat uses a reverse curve traveler, which is actually a combination of vang and mainsheet traveller, to allow the sheet to come from forward and eliminate any possibility of line getting in the way of the tiller or extension tillers. Using a variant of the sheeting system on the Swift Solo the main and jib are controlled with one sheet. The rudder is mounted in a retractable gantry which allows the whole boat to be shorter for trailering and stowage while permitting a very generous "footprint"( the distance between the main foils and rudder foil) that enhances pitch stability. Masthead flotation, as part of the rig structure, prevents the boat from turtling in a capsize.
--
2) The curved foils are used in this application( a performance daysailer monohull) to lift the boat and because of the unique hull design they also add righting moment and take care of lateral resistance. Because they are used as "foil assist" in conjunction with a rudder t-foil the boat will be very stable in pitch. The foils allow approximately 80% of the weight of the boat to be supported on one foil without requiring any form of altitude control. It is also possible that downwind the with the two main foils deployed that they would act like surface piercing foils allowing the whole boat to fly-though the degree to which that is possible(or desirable) is 100% adjustable. The curve is very important for shallow draft and for maximising the amount of vertical lift in a way that allows the lift profile to be infinitely adjusted- impossible with a t-foil, "J" foil or straight angled foil. Small vertical adjustments of the board can produce significant changes in the lift profile of the foil.
They are also fully retractable allowing the boat to be beach sailed. Because of the design of the foil support structure(molded in leeboard) the boat will be able to be sailed upwind with the foils completely retracted(tested extensively on the first Tantra). Using a system similar to the A Class DNA the curved foils can be simply adjusted for angle of incidence. Using a system similar to Steve Clarks Aethon the foil heads could be adjusted athwartship to further augment changes to the lift profile of the foils(probably not required) and finally on the prototype(s) the amount of foil toe-in would be adjustable. See posts 65-68 and post 106 for more on the curved foils as applied to the T2.

---
Preliminary Specs:

Tantra II
--LOA-15.5'
--Beam- 8.75'(pods fold to trailerable width)
--Sail Area-150sq.ft.+ asy-spin
--Draft-1.17'( 14" )
--Weight- 175lb
--Crew- 1-2
--W/SA-2.33 with one 175lb. crew (better than a Moth with a 154 lb crew= 2.56)
--SA/main foil area(one side only)- 85.7/1 (Moth= 78.2/1)
--SA/WS ratio(on foils)-12.5/1 (Moth= 13.65/1--A Class Cat(hull flying)= 6.96/1--C Class Cat (hull flying)= 8.42/1)
--Molded in leeboards serve as the support structure for the lifting foils and also permit sailing off a beach upwind with the lifting foils fully retracted
--Sliding Bench Seats
--Fully adjustable, retractable, curved lifting foils
--Retractable Rudder Gantry
--Wing Tip Rig RJ(ribbon jib)
--Reverse Curve Traveler(vangeller)




Pictures-rough, preliminary concept sketches of the Tantra II-click on image for best detail:

 

[Doug Lord]

Dinghy Design: Open 60 influence?---Design

The application of lifting foils to dinghies-multihull or monohull-is a growing phenomenon in small sailboat design. Widespread use of lifting foils on large racing trimarans has trickled down to a number of small catamarans including the C and A class cats as well as the NACRA 20 and Marstrom 20(?). From the big trimarans on down, the evolution of lifting foils has started with straight,angled boards eventually replaced with curved foils.
--
In monohulls the Moth class, R class and individual boats such as David Luggs original flying I-14( the first two person bi-foiler), Mirabaud and the M4 have led the way in developing the most efficient full flying foilers using just two foils for lift-a bi-foiler configuration. This bi-foiler arrangement remains a remarkable new foiling system -not seen before 1999 in successful applications to small racing sailboats.
These foilers are extraordinarily fast especially in the case of the most refined example-the Moth-the fastest sailboat under 20' beating both catamarans and the Aussie 18. Pretty good for an 11' dinghy!
--
Bi-foilers have been developed and refined over the last 10 years and the application of curved lifting foils to small multihulls is a recent development in just the last three years or so. What all this means to me is that lifting foils are more and more becoming recognized as important to the design of modern
fast sailboats. In small sailboats multihulls like the NACRA 20, A Class cat and others have led the way in "foil assist" design development where lifting foils are used to partially lift the boat. In multihulls "foil assist" ,as currently applied, results in a small loss of RM more than made up for by the vertical lift. In the application of curved lifting foils to monohull dinghies the design can allow for an increase in RM.
In small monohulls the Moth leads the way in foiler design with the constantly refined use of just two foils for lift and techniques like "Veal Heel".
The I-14 and National 12 lead the way in monohull dinghies in the use of "foil assist" to reduce wetted surface and/or improve pitch characteristics.
--
I've done and continue to do a lot of research on the applications of lifting foils to sailboat design. There is a tremendous opportunity for small boat designers in the application of foil assist to all monohulls and to dinghies in particular. Foil assist has been proven resoundingly in large and small sailboats- mono and multi. But like other applications of hydrofoils too often foil assist is viewed as only applicable to the highest performance designs. Two current designs -the I-14(fairly high performance) and National 12(moderate performance) illustrate just a small portion of the range of potential applications of partially lifting foils.
I'm convinced that the use of lifting foils does not have to be limited to just the highest performance dinghies but can be incorporated into new designs that could be classified as "performance daysailers" where the foils can add a level of performance and control not really associated with daysailers until now.
The performance daysailer, that uses state of the art technology to offer proven benefits to the venerable daysailer, is an area of small monohull design that has barely been scratched. The exploration of this area of small monohull design offers tremendous opportunities to the small boat designer and a whole new way to enjoy sailing to their potential customers.
Whether it is a concept design like the T2 above or another equally innovative design the tools, technology, and significant design benefits are available to small boat designers to use to create simply spectacular, easy to sail, cost effective and fun "performance daysailers" that could reinvigorate small boat sailing(and sales).
This is a magical time in the history of sailboat design where the opportunity for innovative design has seldom been greater. The resulting boats could be some of the most user friendly, exciting small sailboats ever produced.
-------
And thanks to Guillaume Verdier and the Open 60 V3 for sparking my imagination and opening my eyes to a potential that is just extraordinary.

pix- two Verdier designs(click on image):


=============
Interesting stuff about the small boat below(oh yeah-forgot to mention: it uses twin retractable daggerboards)-this is translated from the French by
the esteemed translator "google": http://www.guillaumeverdier.com/index.php?/Actualites/Fin-de-chantier-pour-l-Irus-5.50.../

Birth of a dinghy high tech, fully designed by Guillaume Verdier, along 5.50 m planing hull and performance equivalent to catamarans.

The view from Jocelyn Blériot for Sailing Anarchy [03.06.2008]

Well, Giovanni Soldini's brilliant victory in The Artemis Transat aboard his all-conquering Guillaume Verdier Class40 gives me the perfect opportunity to present you this little rocket, born on the same naval architect's drawing board. Oh, OK, that's just a way of putting things because actually, the speed machine was built without any plans, the drawings having only existed in Guillaume's head. Initially, he had started building it for his own pleasure as well as to test new hull shapes before the 2001 Vendée Globe, but being a busy man, things moved very slowly at the yard. Well, his garage, actually.

The thing took up the whole space, and visitors would admire that work in progress… until one of them fell in love with the boat and decided he'd make one for himself - it's now complete and ready to sail, and bears the name Irus 5.50 (Irus being the Morbihan Gulf Island facing Guillaume's house, and 5.50 metres being the maximum length his garage would allow for). Pierre Lediberder, member of the Safran Sailing Team, is now the proud builder/owner of the first of what should be a series. The boat is 2,2 metres wide (4,7 metres wide including wings), and boasts the same righting moment as a Tornado Sport, with which it shares the same deck hardware and wingmast. The total weight, ready to sail, is 170 kg, for a construction in EGlass - Epoxy resin and carbon reinforcements. The idea is to achieve aboard a monohull the same type of performance as on 18' catamarans, providing planing sensations unheard of on a multi. The Irus 5,50 has been conceived to offer sensations which only come very late, and in extreme conditions, on a keelboat. Somehow, we get the feeling this could be a hit… And check out Soldini's Telecom Italia or the Safran Open 60 (VPLP Verdier design), their hull shapes actually partly come from the work carried out on this little beast.

 

[Doug Lord]

Dinghy Design: Open 60 influence? / High Performance Design

I think it is possible to incorporate curved lifting foils into a high performance design- Verdier has already done a high performance dinghy design with dual straight daggerboards.
At this point I'm convinced that a foiler or foil assist dinghy whether high performance or not will benefit from a hull shape similar to the T2 concept because it allows the center of lift of the foils to be outboard of the center of buoyancy(or center of dynamic lift) of the hull allowing the foils to contribute to righting moment. It also allows the hull to be at its best in light air(narrow, low wetted surface) since it will be flying in stronger wind. Anyway you look at it, one of the biggest advantages of curved foils is the fact that they can add to righting moment in some monohull applications as opposed to take away from RM in their use on multihulls-it is an advantage of this type of foil unique to mono's.
--
A high performance version of this concept could use a combination of "J" foil and curved foil that would allow there to be a flap on each main foil allowing
the boat to fully fly at a "wand" controlled altitude(single or dual wands). This system would be more complicated than the T2 or Verdier system but would allow for a speed increase that could be substantial-at least it seems like it is worth looking into. It would allow greater RM than the surface piercing foils used on the original foiler Moth(see pix). The boat might be able to fly on just one main foil and the rudder t-foil or could, conceivably use both foils down in all conditions except extreme light air. This could allow the foils to contribute even more to RM as the wind picks up since the lee foil would lift vertically and the windward foil would pull down. The foils would not retract 100% but would reduce all up draft to around 6-8". The boat would retain the ability to sail upwind off a beach with the foils retracted. The system would probably be the most advantageous in a double handed twin trapeze version.
One disadvantage is that, as best I can tell at this early stage, the resulting foiler would NOT be able to take advantage of Veal Heel-a loss of 20-30% in "free" RM among other things. This may be off set by a gain in RM in the use of dual wands. By using a twin trapeze arrangement the foils would not develop RM except in the strongest of conditions keeping drag down compared to say, a Rave configuration where the crew sits in the center.
This high performance configuration would be able to carry substantially more sail than say a 49er with a great deal more positive pitch control. It would probably be easier to sail than a 49er in stonger winds as a result of better control. Or it could be designed to be faster with less sail area and less crew weight-lots of design options.
Anybody have any thoughts on the concept?

UPDATE: it may be a pretty simple adaptation to have the foil trunks able to take different types of foils with some kind of trunk insert if it seems warranted in the course of foil development.



Rough Sketch of Curved "J" Foil showing hull section, retractable foil, replaceable foil tip and wand, also the Moth with surface piercing foils(Brett Burvill) and an FD from Hanno Smitts site using ladder foils:

(click on image)

 

[Doug Lord]

Dinghy Design: Open 60 influence?--scows

I've seen several threads here on scows recently-one mentioned high performance scows. It seems to me that a scow could be a perfect boat to use curved foils instead of the angled boards used on most scows I've seen and sailed.
The curved foil would help to reduce wetted surface upwind and downwind and would work perfectly with the heeled attitude of a scow upwind.
--
Decided to sketch it out and see if it could work. I tried it on a tunnel hull section and found that, like catamarans, a curved foil used on a scow will slightly reduce RM. A scow with pivoting racks for extra RM and power to carry sail would really benefit. Without increasing RM a bit the benefits would still be there but reduced a bit in heavy air.

-rough sketch-tunnel hull scow w/racks and curved foils-click on image:

 

[Doug Lord]

Dinghy Design: Open 60 influence? / Tantra II vs scow/ "normal"dinghy section

The rough sketch of the scow section illustrates very well the superiority of a section like the T2 when considering the application of curved lifting foils to a monohull dinghy. The T2 allows the center of lift of the foil to be further outboard permitting it to increase the RM of the boat in addition to providing vertical lift. The same thing would be true of a "normal" dinghy hull as is true of the scow-RM would be slightly decreased. Not a deal breaker but definitely illustrates the value of the unique hull section of the T2.


rough sketches- left-scow with curved foil, center-T2, right- T2(not to scale) with vertical lift change with retraction illustrated(click on image)

 

[Doug Lord]

Dinghy Design: / Tantra II curved lifting foils

So far, I'm still satisfied that the T2 concept( post 110) shows the most advantageous use of curved foils on a monohull dinghy. The T2 allows the foils to be placed significantly further outboard than a "normal" dinghy hull section would permit and that lets the foils add to righting moment. It's a significant application because, on multihulls, the curved lifting foils actually reduce righting moment while providing a bit of vertical lift.
On Open 60's, as best I can tell, the foils don't add or subtract from righting moment.
So the T2 is the only application of curved lifting foils that not only provides vertical lift but also increases power to carry sail-and that is a formula for a fast dinghy. That works out to an approximate 50% increase in righting moment over what would be possible on a non-trapeze dinghy. Not a bad potential performance increase and a great raison d'etre for the use of this kind of foil system!
-----
Earlier, I mentioned the original Tantra-a successful experimental boat I designed and built in the 70's. It used molded in leeboards that worked real well . That boat is the inspiration for the T2 with its unique shape and "amenities" like a built in cooler and large dry stowage compartment. The T2 will be, for sure, a performance daysailer with the significant performance increase offered by the curved lifting foils.
Here are four pictures(again) of the original Tantra:

 

[Doug Lord]

I wonder if a single curved foil could be used on a dinghy hull? It doesn't make any difference which side the lateral resistance is on or if its not centered. So it seems it might be possible to have a single foil with a relatively tight curve that would develop approximately the same lift as a T-foil daggerboard but be fully retractable. It would also be able to remove the vertical lift leaving just the lateral resistance when that might be desired.
Probably not the performance potential of a T2 but when deployed for maximum lift might be able to be sailed advantageously with veal heel adding 20 to 30+% more righting moment-but only if the problems associated with surface piercing foils, altitude control and full flying athwartship stability were solved.Some people would recognize that "Veal Heel" as mentioned above, by definition, only works on a full flying foiler. For those that don't let me emphasize:this could only work on a version of the single foil system designed to fly the boat.
But for "foil assist" ,if properly designed, it would definitely produce enough lift to reduce wetted surface and allow the boat to plane earlier as well as having the "lift profile" 100% adjustable.

Rough sketches of one version- a continuous ,partially open athwartship curved trunk would allow the curved board to slide easily(with proper design) from one side to the other; board could be asymmetric, retracted board is totally within hull, would work well for "foil assist". A smaller radius(not by much) could provide more lifting surface when deployed and perhaps work similarly to a t-foil daggerboard. Problems would be similar to those of a surface piercing foil for a full flying version....:

(click on image)

 

[Doug Lord]

More thoughts on a single curved foil used on a dinghy for lateral resistance and vertical lift-a summary so far-version 1:
1) First application I've found where a single curved foil could replace the two foils required in every other current application of curved daggerboards,
-
2) Lots of potential to play with the radius of the curved board to maximize or minimize vertical lift,
-
3) Seems that it may be superior to a "normal" daggerboard in every case including storage(retraction w/o hitting the boom etc),
-
4) Problems include how to grip the board to slide it from one side to the other.
Might be possible to use some sort of hand crank, line that rotates a drum between the two trunks or?. Needs more thought.
-
5) Despite my first impressions in the previous post it does not appear to be able to increase RM(as does T2 dual board system), though this may change as the idea is refined.
-
6) When considering this single curved board system and the T2 dual board system it becomes abundantly clear that the use of curved lifting foils are not only possible on dinghies but can offer significant performance potential. By using innovative design these boards can be incorporated in dinghies from "performance daysailers" to scows to all out high performance twin trapeze dinghies.

 

[CutOnce]

I wonder if a single curved foil could be used on a dinghy hull? It doesn't make any difference which side the lateral resistance is on or if its not centered. So it seems it might be possible to have a single foil with a relatively tight curve that would develop approximately the same lift as a T-foil daggerboard but be fully retractable. It would also be able to remove the vertical lift leaving just the lateral resistance when that might be desired.
Probably not the performance potential of a T2 but then again when deployed for maximum lift would probably be able to be sailed advantageously with veal heel adding 20 to 30+% more righting moment. Hmmmm....
a sketch later on..

Regardless of where one puts it and how one curves its, it will result in asymmetrical and unequal performance on opposing tacks and various heel levels. The windward heel mentioned will also be asymmetrical. The windward heel righting moment "advantage" comes into full play when the Moth is lifted above the water, and the lofted weight is to windward of the foil now supporting the boat. In this case, unless the boat hull is lifted clear of the water, the same advantage is not fully realized.

In addition to the problematic "one-sidedness" of the design, practically (I know the original poster hates my practical comments) this design would be unrightable from a capsize, as there is simply nothing to stand on to gain righting leverage from a capsize. A slippery, curved board would be impossible to use for righting purposes. Much like my original comments a month or so ago, this technology that applies to ocean racing keelboats is not an easy or good fit with a dinghy.

It seems this concept is coming full circle - hopefully recognizing that two daggerboards have much more drag than one, and a central lifting T-foil is the optimal configuration for providing symmetrical lift and low drag performance on both tacks. Continuing the last few degrees in this circle the exercise arrives back to the Moth configuration.

--
CutOnce

 

[Doug Lord]

1) Regardless of where one puts it and how one curves its, it will result in asymmetrical and unequal performance on opposing tacks and various heel levels. There may be some that don't realize how this is supposed to work: the foil(at least at this point) is always on the lee side and is moved by the crew from tack to tack(gybe to gybe) in what amounts to a continuous curved trunk partially open in the middle of the boat. Or partially open from the cockpit sole all the way across.

2) The windward heel mentioned will also be asymmetrical. The windward heel righting moment "advantage" comes into full play when the Moth is lifted above the water, and the lofted weight is to windward of the foil now supporting the boat. In this case, unless the boat hull is lifted clear of the water, the same advantage is not fully realized.

3) In addition to the problematic "one-sidedness" of the design, practically (I know the original poster hates my practical comments) this design would be unrightable from a capsize, as there is simply nothing to stand on to gain righting leverage from a capsize. A slippery, curved board would be impossible to use for righting purposes.--
CutOnce

---------
1) That simply doesn't make any sense to me-look at canting keels-asymmetric placement with no negative effects. Look at dual boards on scows and mini's-no problem whatsoever. Look at the twin daggerboards on open 60s AND on much smaller boats like Verdier's twin board 18. The curved board will allow significant vertical lift that would be 100% adjustable-the lateral resistance being on one side is identical to numerous other boats and of no consequence.
-
2) I have claimed no windward heel advantage for the concept UNLESS it does lift the hull into full flying.(though my original comments might have been ambiguous since corrected) There are problems, mentioned above , with designing this foil to be able to lift the hull clear of the water-among them are that it would then have some of the characteristics of a surface piercing foil and might have to work like one(where athwartship stability full flying would be an additional problem). A wand based altitude control system is probably not possible but this is early to rule it out. The fact that the foil would create vertical lift(foil assist) that would be likely to be adjustable between 0 and 80% of the boats total weight is a tremendous advantage of the system. The fact that this can be accomplished with a single foil is truly remarkable. Much stronger and simpler than a "T"- foil.
-
3) Aside from the incorrect "one sided" argument, this is a really good point and I have not yet given it any thought. Thanks for considering it.

 

[Doug Lord]

Dinghy Design: Open 60 influence?--righting idea

... this design would be unrightable from a capsize, as there is simply nothing to stand on to gain righting leverage from a capsize. A slippery, curved board would be impossible to use for righting purposes. --CutOnce

================
Well, that didn't take long: with the board partially retracted, on a two person boat, two people could stand near where the board comes out of the hull braced against the board and hull and use a righting line(s) like a multihull and pull the boat back up.
Sorry, but that is not accurate.
This would actually work better than a "normal" daggerboard or one with a t-foil on it since no one would have to climb up out of the water onto a slippery board-the curved board would be just a few inches submerged-not sticking out of the hull at arms length above the water. And using the junction of the hull and board would help to keep the crew in place as they lean back with the righting line(s).

Rough sketch showing righting system( click on image) :