The idea is to design the foil to lift 100% displacement when fully canted off the wind, and to provide additional lift to windward at reduced angles for upwind work while still providing some additional RM and reducing the load on the rudder? Lift to be regulated by foil taper, and pitch by extended knuckles slightly above static waterline on bow and stern? The amma would swing for and aft with each shunt to move center of gravity aft of lifting foil and assure bow up attitude hopefully assuring a positive angle of attack and avoiding pitch pitch pole.It might be possible to make small course changes by playing with the foil and sheeting angles.Thoughts?

Michael Schacht (a.k.a. Editor, a.k.a. the forum Admin), had some positive results with a somewhat similar arrangement on a small scale model.  He wrote about it in as part of an article many moons ago and posted it here: http://www.proafile.com/archive/article/testing_with_models_i.

My only real concern with you concept is that, extending down from a safety ama, there will be quite a lot of extra foil area above the waterline and forward of the CLR.  Have you considered to effect of heel on weather-helm?

Thanks for the article . I have not seen that before . Very informative . His experiments lead me to believe that I may be on to something.
    Regarding weather helm ,the lateral resistance component would be shared equally by the foil and the rudder sailing with the windward ama just skimming the surface I am thinking that as the hull heels in the gusts the angle of the foil on the safety ama would increase producing more lift upwards and less sideways thereby loading up the rudder and shifting the center of lateral resistance aft negating any increased   weather helm. The increased wetted surface and resulting drag of the foil I think could perhaps result in lee helm. Just speculating.

I think I just died… that boat looks amazing! I already thought it looked good in your first post a while back, but this just tops it by a mile. 😊

I’ve toyed with the idea of a leeward foil as well, and while it’s probably the easiest way to get the vaka out of the water, you would be trading in the extra safety that the pod / safety-ama normally gives you, for a (potentially dramatic) performance gain. Being up on the foil would put you in the same sort of precarious situation as a trimaran flying two hulls. I very much like the idea of having an extra layer of safety to catch me if I fall, but that’s a personal preference, you’d just really have to watch out you don’t get flipped over when you’re up on the foil.—Do you see any realistic possibility of getting the foil in closer to the vaka, so you still have a useable safety ama even when foiling?

Greg also pointed out there’s a lot of the foil out above the waterline, what comes to mind for me there is that’s an awfully long lever for the forces acting on the foil (at least if you are planning to fly high enough so this thing is more or less horizontal), which would make the foil-ama connection even more highly loaded. Is there any good way of getting the connection moved down closer to the waterline to reduce the length of that lever? Or at you intending to fly the boat with a good bit of heel, with the foil well immersed?

I like the idea of getting the foil forward to reduce the chance of pitchpoling, but what about structural aspects of that? I’d think with the foil carrying 100% displacement, getting a canting setup for the safety ama would prove to be pretty tricky, because the loads in the joints are bound to be pretty enormous. What’s your thinking there? Do you think canting will be lighter in terms of overall weight, as opposed to having two separate foils? Having separate foils would also allow you to use normal 1-directional foils instead of having to use a bidirectional one.

Sorry if all the questions seem overly critical; I’m just playing the devil’s advocate here. 😉 All in all I really love the design, keep it up! 😊

Marco

Marco there are actually two foils on the safety ama .one is down on one tack and the other is down on the other. I wanted to make shunting a quick easy one line procedure so I have devised a system that may or may not work, where the mast and wishbone rotate as the ruder rotates and slides from beam to beam along a track, and the safety ama swings for and aft.at the same time as the foils which are interconnected by a pin on the center section of the safety ama,. rotate on the pin. To cant the foil, the center section of the safety ama which is cylindrical ,is rotated by means of a lever . The line to the lever acts as a water stay.  Perhaps safety ama is the wrong terminology for what holds the foils. It only displaces less than a thousand pounds but I feel that it would only need to provide stability in the event of a sudden gust while sailing in light winds, as dynamic lift from the foil would provide the additional RM needed at speed.
  I am worried about the unsupported portion of the cantilevered foils, more so the rudder than the ama foils, as I feel it could be at times under more load, and its lever arm increases with heel rather than decreases like the foil on the safety ama. On the other hand the boat fully loaded only displaces 4500 lbs so not a lot for the foil to lift. Moths and the ac 72 s have much bigger lever arm problems when fully flying. The boat is not intended to fly but to skim across the surface. I placed the lifting foils and safety amma as far from the aka as as I could with in the limits imposed by the boats folded for trailer and container transport configuration, The idea being that the farther lifting foils are from the windward ama the smaller and less immersed they can be.
I realize that this post is almost impossible to decipher so if anyone is interested I could put up an animation on u tube of the boat folding and shunting.  It might better illustrate the concept.

Cool.  The concept really looks worth continuing to explore.  Although I can’t doubt the potential I keep hearing John Harris of CLC reminding me about the magic of cheap, simple, easy to build and fast.  He is of the opinion (I’m paraphrasing here) that if you deviate from that mantra, proas lose their mojo.

—
Bill

I realize that this post is almost impossible to decipher so if anyone is interested I could put up an animation on u tube of the boat folding and shunting.  It might better illustrate the concept.

Yes please 😊

: http://youtu.be/KVo35Fo7pXU  I hope this link works. I realy don’t know what I am doing .Not great video but I think it shows what I am trying to achieve.

timothy - 24 September 2013 04:52 AM

: http://youtu.be/KVo35Fo7pXU  I hope this link works. I realy don’t know what I am doing .Not great video but I think it shows what I am trying to achieve.

Worked fine for me.  Very nice work.

—
Bill

Well, I just think the whole thing is extraordinary. The design, the intricate folding mechanisms and the animation as well are all brilliant. Thank you, Timothy

That is a brilliant design and a real piece of engineering.
The video works perfectly, and really show what you are trying to achieve.

Cheers,
Johannes