kFOIL™

I've mentioned this system in some other threads but I bring it up here to ask for comments and to discuss it's relative merits. Also, I have recently had the good fortune to meet Eric Sponberg who is now the only authorized Naval Architect and Marine Engineer "Officially" licensed to design boats using the kFOIL system. Eric has been approached by an individual who wants a Mini 6.5 designed for the 2007 race and specifically wants to incorporate the kFOIL™.
Basically, for those who don't know, the system is a patented lateral resistance solution for canting keels where by one or two foils(wings) can be deployed from and retracted into the canting keel bulb. The system allows a canting keel without any daggerboard(s) or forward rudder so only the keel system itself impinges on interior room. It is designed to retract should it contact anything hard while sailing.
The system has several beneficial configurations from a single rotating wing as illustrated below to two folding ""ACC" type wings. It can be used on a canting keel fin deployed for upwind sailing and retracted for downwind sailing and light air. It can be used in conjunction with a low aspect ,low area fixed keel to upgrade windward performance folding out of the way when not needed.
The use of ACC type wings for extra lateral resistance was pioneered by Andy Dovell on Atomic and they have been proven to work successfully in canting keel applications. The kFOIL goes one step further by allowing the wing or wings to retract downwind or in light air.
Constructive comments (or otherwise ,I guess)
welcome.
This is an illustration of the deployed ,single wing version of the foil:
http://www.rcsailing.net/forum1/data/wgorgen/20043312449_kFOIL102.jpg

 

KFOIL For Mini 6.50

I was already waiting for you to come up with the KFoil design and you have done so now.
To ask Eric Sponberg to design a mini 6.50 is not an unlogic decision. I have looked a bit more closely at this attractive class, however, the designtask is a far cry from being simple. So is the foilsystem.

To optimise the hull, is it necessary to tanktest the system as a whole or do you first the hull and then the complete body? Or can you do without it.
Or, can tanktesting be simulated by other means since those tests are quite expensive. I have Wageningen nearby and sometime ago I have observed testingprocedures for certain vessels.
Another question: The 6.50 class is split in two sections I believe: The Proto and the Pogo. For which class the design will be made? I presume the Proto-class.

You have two slots in the keel, are you using a mechnical device to get the foils out of their respective slots because somthing must keep them from going back in their slots by the (strong) flow of water they 'll meet down.

I have a few other questions, but they are more related to the hull and not so much to the keel. Maybe thet pop up later as the direction of your thread allows it.

I have myself logged in the particular mini transat forum to be aware of the most current discussed issues. Masts and keels are top of the list. Specifically the race of 2003 had been a slaughterhouse.

It is my strong belief that for such a small racingmachine where every atom counts, any advance in keeldevelopment must be put into practise.

 

Ideally, it would be nice to tank test hull and keel to optimize the design features--winglet area, sweep angle, angle of attack, foils shape, degree of deployment in relation to keel angle, etc.--but I doubt that the design budget would allow that. In fact, I bet such a testing program for a small boat as this would cost more than the design itself.

Yes, there would be a mechanical system to deploy the winglets. Another consideration is to use a hydraulic ram and hand pump to actuate the winglets which might make the mechanical design simpler and easier to control at any arbitrary deployment setting.

We have not started the hull design yet--our skipper/owner is still puttting together the funding for it. Yes, this will be in the Proto class.

We anticipate that the rig will be a carbon fiber free-standing wingmast sloop, thereby giving us advantages above the waterline as well as below.

We will report more as the project proceeds. In the meantime, we welcome comments on kFOIL from readers.

Eric

 

I would be very interested in seeing a bit more scientific data on the proposed system, like some CFD work, or even better a good VPP study. The idea would be to see how it compares to another design.

I am of course wrong, but i think that people which have patents should have an obligation to develop (scientifically or experimentally) the idea. And not just get the patent, and stop somebody else/or group that would have been happy to develop the idea and try it. (i dont say that it is the case here, i am just waiting to see real explanation )

What makes me smile is that, in a sense, you are asking us to develop the idea.

When was the system licensed to Eric Sponberg ? After or before the individual required the kFOIL (cant find the TM sorry)?

I am asking the question because i am far from being convinced on its use on a mini. I dont really think it will be very effective;
1) just look at the size of a mini bulb, (250-300kg) , you ll never put enought area in there , or it would increase bulb wetted area by a large amount.
2) I dont think it is as efficient as a large aspect ratio daggerboard. ( a mini needs lateral area).
3) And finally downwind, when you can remove wings or daggerboard, u ll end up with a bigger wetted area + all the extra drag to hide the wings.

I see a possible use for downwind sportboats, see the last bethwaite sportboat keel (www.bethwaite.com) .

 

Nico,

Yes, we too would like more scientific data, and model testing and full-scale testing would likely be more reliable than CFD, and certainly better than a VPP. Ultimately, test results of some sort along with academic studies will be the goal, but of course, such testing costs money and time. It may be more easily obtainable on a larger boat design which has a bigger budget to afford it. For the Mini, we will likely confine our testing to full scale on the boat itself, which of course, requires that we design and build the boat first.

We are not asking for the readers to develop the idea, we're smart enough to do that ourselves. The reason for this post was to let the public know the kFOIL is available, and that we are working to really make it happen, be built, and spark interest in using it in other boat designs. As we develop design and testing results, Doug will probably publish meaningful reports.

The owner for the Mini approached Doug Lord first to use the kFOIL on his boat, and then Doug approached me for engineering. On discussing the concept, it certainly looked like a worthwhile idea and buildable, so we are proceeding with the details. During those discussions, the patent was pending and has now been approved.

We recognize that there may be extra drag issues with the kFOIL and its wing deployment, but overall they will likely be minimal. To counteract that, we are looking at significant improvements in the hull design, and certainly with the inclusion of a wingmast rig, we expect a lot more power in the boat, particularly downwind where, as you say, the extra drag on the keel could be detrimental. We think we can compensate for that with all the design factors that we'll be dealing with in this boat.

Eric

 

, i am sure that everybody on this forum know that kFOIL is available.


Summurizing your last paragraph; kFOIL will not improve performance, but with improvements on other part of the boat, you ll be able to "compensate". (nicely said)

We are talking about a racing boat here, right?
Why not just use a good package for lift production (a daggerboard) and use the improvements on other parts to do a better design.

Finally, i can see improvements done on mast design (they ll first race with carbon mast next year) , (but not sure about heavy free standing mast)
However, hoping to improve hull design is probably a lot to ask for, (even harder without experience on mini design).

 

We surmize that there will be significant lift advantages with the kFOIL which will benefit the boat's windward performance, and the purpose of this particular endeavor is to design a boat that is as good as or better than the current crop of Minis without using daggerboards. As you are aware, daggerboards have added drag as well as lift, are susceptible to damage, and are not necessarily the bees knees in boat design. We are looking for improvements in overall performance, and the kFOIL is certainly worth exploring. That's the point--to determine its advantages on an actual racing boat.

Remember that low weight is not everything--you cannot sacrifice weight to the exclusion of all else. There are some instances where the judicious addition of structural weight--such as in a free-standing rig (and what are we talking about here, a few pounds?)--could be quite beneficial. See my website (www.sponbergyachtdesign.com) for a complete discussion of the advantages of free-standing rigs.

Eric

 

kFoil development

There is a lot to learn about the kFOIL; thats for sure. But we are starting from a standpoint in which the benefits of wings used as a lateral resistance solution for canting keels ARE ALREADY KNOWN. I personally talked to Andy Dovell about his system as used on Atomic and other boats and he is convinced of their merit after much racing. The question is can the beneficial attributes of fixed wings be translated to a retractable wing system while still retaining the benefits of the wings upwind? I think the answer is probably yes.
The fact the the system is self contained in the canting keel itself lends itself to the application of canting keels to smaller boats and to cruising boats with canting keels. There are other applications and several different iterations of the system to be tested as time goes by ...