Possibility of a foiling proa
Hi everyone,
since foiling a laser is possible these days I am trying imagine if a foiling proa could work.
Because of the tripod arrangement of the rudders and board it is interesting from a mech-engineering standpoint
I chose madness because its kind of proven and its all about the foiling and not designing a new boat.
first I tried to get some numbers on some sort off mainstream foilers
then tried to get some numbers on vertical lift the foils(rudders and board) of madness would need.
madness is very heavy in comparison to the other boats in the excel
Note1 (D/SA) is just for easy comparisment (no scientific intentions)
Note2 i think it might not be worth the trouble because madness is already very fast, BUT it might take off into something else i havent thought about and boil down to some cool proa foiler one day thats why im posting it.
next i’d like to post about my thinking on foils and turning them
in the foiling laser they use a sensor on the side of the standing foil that actuates the liftingfoil angle mechanically.
the sensor is so narrow it can come thru the dagerboard casing in a bit of extra cutout so the whole thing can be taken up right until the lifting foil hits the hull.
not sure how they did the sensor mechanism but the white piece stands for that.
here it also has a rudder in the middle
the lifting foil sys is working on its own(as in the laser) so the rudder function comes above deck.
a system to rotate the whole thing 180 also will come to the deck
Hello Loefbijter,
Thanks for the posts. With your interest in hydrofoil proas, you’re following in the wake of some notable designers. This is a mark of quality! If you have not already come across it, here is a webpage that details some past efforts:
Mr Smith’s Amazing Sailboats - Other Craft
Have you considered a design that uses fully immersed T-foils, but with them being angled, so that the foils’ force vector acts to windward?
Cheers,
Paul
Hi Aerohydro,
thanks for the site, a arrangement like kotaha is exactly what i was thinking off.
that seem to answer my topic question; yes it can be done, and was done in the early 70’s!
Not sure how Leif Smitt did the turning of the foil rudders, but what i get from the text is that there is a vertical hinge attatched to a C-form looking from above.
and on on end of the C is the bow and the other end is the rudder hinge.
so the now-bow foil is between ends of the C, and the now-stern foil is trailing behind the C?
haven’t thought about canting the T-foils, i can think of two things i would not want them to do.
this has the side effect of the rudder giving vertical lift and the lifting foil could become surface piercing which adds drag right?I guess i just dig those almost silent and spray-free blades the moth’s have.
the plus side might be less wetted surface when going fast and more vertical lift going slow?
and like you said, more windward lift.
figuring that out would be a big leap for me engineering wise.
easier for me would be purpose designed for either vertical of horizontal lift.
about the inverted T foil, is that a cross or “plus” arrangement?, so he would always have a horizontal component force?
I read an artikel the other day that morelli&melvin; used to joke at their office that the hull structure of the ac72 was merely a foil delivery system.Just like Kotaha and alot of other boats on your site.
I guess my initial question now comes down to:can you build a hydrofoil with the foiling laser tech and a newick-style rudder? because the newick style rudder was my initial idea
for the reason that the boat can take up the foils forces from the deepest to the highest point of the hull.
But why want a newick style foil, because there won’t be al lot of hull to stick a foil through in a foiling boat.
especialy when you want the foils at the end of the main hull.
The Kotaha system as I interpreted it seems very straightforward, and like your site says did not reach it full potential
I have done something on that topic, with models. I have used inclined foils to lift the craft and have the possibility of steering by simultaneuslychanging the inclination angle of both foils in opposite senses.
Regards
Fulgencio
Found this on Sailing Anarchy. More of a cat, but interesting.
http://sailinganarchy.com/2013/10/26/flexible-flyer/
Could not find other information.
Thanks for replying.
Not sure how Leif Smitt did the turning of the foil rudders, but what i get from the text is that there is a vertical hinge attached to a C-form looking from above. and on on end of the C is the bow and the other end is the rudder hinge. so the now-bow foil is between ends of the C, and the now-stern foil is trailing behind the C?
I’m not clear what you mean by ‘C-form’. Judging from the photos and plans that I’ve seen of the “Kotaha”, its foil and rudder set up is fairly fuss-free and uncomplicated. The bow rudder/foil unit is locked in place simply by securing the tiller, preventing it from moving about. The stern rudder/foil unit is free to turn, just as on any conventional sailboat.
haven’t thought about canting the T-foils, i can think of two things i would not want them to do. this has the side effect of the rudder giving vertical lift and the lifting foil could become surface piercing which adds drag right? I guess i just dig those almost silent and spray-free blades the moth’s have. the plus side might be less wetted surface when going fast and more vertical lift going slow? and like you said, more windward lift.
As long as the inverted canted T-foils are immersed most of the time, it probably wouldn’t be a problem if they happen to pierce the surface from time to time. By the way, the notion I had for the foils would be that they they’re very similar to those used on the Laser foiler, but with the entire unit simply canted over. There wouldn’t be a “vertical” rudder, just one that’s at an angle.
Cheers,
Paul
One facet of the proa design is that the forces acting on it will always be coming from the ‘same’ windward side of the vessel. The need to have a true symmetrical foil arrangement, with a horizontal wing and a vertical fin, as on the Laser foiler, just wouldn’t exist on a proa.
Cheers,
Paul
I really like your model Fulgencio!!!
Have you sailed it yet? Pictures? Videos? Is there any more information about it?
I am very curious about your proa-foiler!
Cheers,
Johannes
I have contemplated a similar system and I am curious. Why would you not move the struts and their pivot points to positions above the water line? I think its possible that they could be designed so that when the ama is flying and the vaka is loaded, that they are immersed and provide additional vertical lift, and as a consequence RM, until at speed as the vaka rises they clear the surface (passive altitude control?).The idea would be to mimic the effect of the angled foil tips of team NZ"s Ac72, except that while NZ paid a surface area penalty while in displacement mode the foils on your model would have less drag at displacement speeds. I would also wonder why given that the relation ship between CE and CLR will be governed by the cant of the foils and that a positive bow up attitude could be assured why not use a much more efficient high aspect uni rig.
I have done something on that topic, with models. I have used inclined foils to lift the craft and have the possibility of steering by simultaneuslychanging the inclination angle of both foils in opposite senses.
Regards
Fulgencio
Fulgencio,
I think you had videos on Youtube of towing tests of your model you show on the pictures; and the results were very impressive. I cannot find them anymore…
Could you post a link?
Did you go any further with this concept?
Thanks,
Laurent
http://www.youtube.com/watch?v=2_ETZoUQq1g
I did some towing tests in the 80ยด but no videos as far as I rememember I did a small video to explain the system some years ago (link above) and the aim was to steer rather than to fly. I have done nothing since then.
Fulgencio
To Timothy:
Thanks for your interest,
Most of the studies I have done, and models also, are of the type “Harryproa” , this is “weight to windward” and the long hull, fitted with the twin foils to leeward.
Of course the pivot points could be arranged above the waterline. I guess that, if you intend to fly, you shoul place the foils as low as possible, in order to reduce the takeoff speed. The length of the struts has to be carefully considered but my advise is not to make them too long since the contol of the proa will be worse. I have built models with a single sail -Una rig- The fore-aft stability has to be considered. Nevertheless it is easy to achive a good longitudinal stability by placing the sails center of effort rather aft: in that way, the fore foil is required to produce less sideforce than the after foil so that it has to be placed more horizontal, contributing that way to lift the bow. Some models I towed to see them fly were fitted with a third foil in the windward hull. This foil was either canted opposite to the other pair or was a “V” foil. The aim was to obtain a craft that could be managed without great effort or personal equilibre.
Fulgencio
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`Nevertheless it is easy to achive a good longitudinal stability by placing the sails center of effort rather aft: in that way, the fore foil is required to produce less sideforce than the after foil so that it has to be placed more horizontal, contributing that way to lift the bow.``
This is the approach I am going to try on a 1/4 scale model I am now making of a foil assisted proa I intend to build later.. I want to experiment with a canting foil on the safety ama of a pacific proa. I will use a vertical rudder that slides and rotates during a shunt rather than rudders at apposing ends. The foil will be canted at about 45 degrees so the rudder will be handling at least half the lateral resistance loads. The safety ama and therefore its"s foil will move to be slightly ahead of the center of effort so that the center of gravity will be behind the center of lift. I feel that this configuration should allow for additional righting moment lacking in the pacific proa and allow for some trim control by adjusting the cant angle of the foil. I would be interested to know what you think ,based on your experiments as to weather or not you think my approach is workable, and if it is, what I could do to increase my chances of a successful outcome.
Hi Timothy,
Although I do not see clearly how the moving rudder will be fitted I think your system can work. However, the advantage of using a canted foil is truly small when you have your weight to leeward. I would reccomend you to design a transversal sketch showing the force vectors involved, in order to asses the utility of the arrangment of the canted foil. Anyway, I feel curious. Please let me know if you have a preliminar design
Fulgencio
3D approximation . Foil size limited to constriction imposed by folded dimensions of boat for trailer and container. Otherwise all parameters are adjustable. Ideally the foil would handle 70% boat displacement at somewhere around 10 t0 15 knots. Hopefully a quarter sized scale model will at least better inform me about the relationships of these parameters.