Dinghy Design: Open 60 influence?

[Doug Lord]

Breakthru!
I've looked a t a lot of possible solutions for this including using some sort of roller that touched the board and allowed it to move with a hand crank or another means of causing rotation.(see post #117)
The breakthru comes in post #16 of this thread: Quant 28-foil assist keelboat / DSS

Hugh Welbourn makes a comment-the first I've ever read- about how the DSS foil on the Quant 28 is moved. It has a roller in a wetbox where the shaft of the roller is sealed like a stuffing box-only simpler. Cranking or rotating the roller slides the foil athwartship! It is a brilliant idea for that boat and foil system and a version of it would work w/o the wetbox for the single curved dinghy foil. The break thru is the certain knowledge now that a roller system will work!
The foil is a single molded asymmetric foil that slides in a trunk across the boat.
When centered it is retracted and it can be deployed on the port or stb side and adjusted at will. Using the roller system it could be tied into a sliding seat so that it is automatically deployed tack to tack.
Thanks for the inspiration, Hugh!

[Doug Lord]

This is a possible addition to a single curved lifting foil that I've just conceived of: instead of having the foil 100% retracted when centered as shown in the previous post the foil tips could be allowed to hang down below the hull on each side so that when the boat is beached the hull doesn't touch the sand! The tips could be designed to be replaceable....
I used replaceable tips on the orignal Tantra mentioned earlier in this thread and they worked very well.
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Also, here is a rough sketch of a gear system that would allow the foil to be tied into a sliding seat for automatic movement.


Rough Sketches,L to R: L= single curved lifting foil with tips that extend below hull when board is in centered(retracted) position, R= possible gear solution to moving board automatically without any disruption to the surface in the water.
click on image:

[Doug Lord]

I've been extremely busy for some time but when things settle down a bit I'm
going to start another thread focusing 100% on dinghy designs using a single curved lifting foil. I think the Tantra II concept(see earlier) has tremendous potential as well, but I think the single curved foil may be able to be applied in such a way as to produce an extraordinary dinghy with a higher percentage of "foil assist" than any current dinghy. The single curved foil has potential to be a relatively inexpensive "foil assist" solution with or without a rudder t-foil-and even if a rudder t-foil is used it could be significantly smaller that the foils on an I-14, National 12 or Moth.
I think a small dinghy using this foil offers unmatched performance potential compared to non- foil assist boats. Coupled with a sliding seat that can automate the movement of the foil and the full or 90% retractability of the foil
the boat could demonstrate exceptional performance with comfort and ease of sailing.
We'll see- I'll get into it when I can.

[Doug Lord]

Here is the basic concept of the Tantra II-a design based on an earlier design of mine. It will be some time before I can do any prototype development of this concept but anybody that would want to work further on the design is welcome. I think it has tremendous potential as shown in the original hull or in a newer version using the basic concept. It is the ONLY design application, that I am familiar with, where curved lifting foils add righting moment ,vertical lift and take care of the lateral resistance in a monohull dinghy.

Originally Posted by Doug Lord

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.
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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 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.

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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)

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Development Target: One of the most significant developments in foiler design may be a curved foil that uses a flap on the portion that lifts vertically that can be connected to a wand surface sensor rather than a Hobie trifoiler "feeler". The aspect ratio advantages of the curved foil(Greg Ketterman) would then be able to be easily adaptable to a retracting curved foil instead of using the "feeler" surface sensors on the non retractable, all moving Hobie Trifoiler foils. If anyone comes up with a good idea how to do it I will try it on the model in this thread: High Performance Self-Righting Trimaran: The Test Model
The results may be applicable to any boat using the right kind of curved foil.


Pictures-rough, preliminary concept sketches of the Tantra II and the original Tantra hull and rig-one of the first square top rigs ever-
click on image for best detail:

[Doug Lord]

I think it will be exciting in a few years(or decades) to see how and when dinghy design takes a turn again and applies modern foil technology to boats that don't necessarily require the most athletic of crew. Fear of foils is fading and it seems like a wide open area of small boat design to incorporate foil systems where the foil(s) contribute to RM, and ease of sailing, better handling and more fun for a wider audience as a result. It's already happening big time in small and large multies-maybe dinghies won't be too far behind....
The Moth, I-14, National 12 have already shown what can be done in the highest performance applications of full flying and foil assist for monohulls but there is a whole untapped world of monohull dinghy design that could benefit from what is known about foils now.
And the Open 60's have shown that adapting proven technologies from multihull foil assist applications can pay big dividends.


"sailing on foils is more fun!"

click on image-