High Performance MPX Foil/Self-righting Trimaran-The Test Model

Fire Arrow Foiler / MPX Foil System Testing and Development

For the sake of those that haven't seen post 1666:

Click on pictures for a better view:

 

I'm an idiot in this so forgive me but, would those pics mean less lift would be allowed for total submerged high speed? And it understand that might also cause not enough lift for low speed, but don't you want total submerged for less drag? Or I.e a single piercing with a foil. Or is it a case of higher lift area for low speed is now out of water where it's less draggy and lower lift needed at speed is just right?


Barry

 

Fire Arrow Foiler / MPX Foil System Testing and Development

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Checked the board tonight-mainfoil set at +2.5 degrees, rudder foil at zero degrees-just perfect-ready to sail Sunday morning.

click--

 

Fire Arrow Foiler / MPX Foil System Testing and Development

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Right! For this boat for now. According to Tom Speer it is better to not have the foil tip breach the surface, but I'm concerned right now with what works. I'm still in the middle of finding what the ideal AOI is for all conditions-or if there is one. So far the ama foils have worked fully submerged and with the tip exposed(see picture #3). In pictures A and B below the port ama foil maintains the same altitude at two different speeds with two different loads-which means the foil is working pretty well but there will be more testing.The third Fire Arrow picture shows a bit more ama altitude with the tip of the i-flap/foil exposed. Much more speed than the other two pictures.
Interesting that the full size cats using UptiP foils all sail with the inboard tip exposed-see last two pictures-Flying Phantom(picture by Pierrick Contin) and GC32(on a record run-picture from their site) :

 

Interesting stuff for sure! And makes sense, and I suppose even a second piercing is still less drag than a whole boat! I'm guessing that's also a advantage in the hydroptere dip stick style approach in than one part, one Pierce, and as it changes speed it rides in and out of pitches? I like the idea of no sensor( or wand) just rides as it needs where it needs. As far as foils what are the basics? Single sided foils, double sides with crucial angles of attack? Wait you did list foil in here so we here didn't you?


Barry

 

Fire Arrow Foiler / MPX Foil System Testing and Development

Theres a bunch of stuff on the forum about foils:
1) Foiler Design-search "Sailboats"
2) Sailing Foiler Design-in the Aerodynamics and Hydrodynamics forum.
3) The Little America's Cup thread(2013-here) and the 34th AC thread(here) also have little tidbits.
4) The basic foil types are fully submerged and surface piercing. Traditional surface piercing foils control altitude with speed and are always used in pairs-like Hydroptere. Fully submerged foils(Moth, Rave, Osprey, Hobie Trifoiler, the new Vampire and others) keep the foil submerged by the use of a surface sensing wand(or "feeler" in the Hobie Trifoiler case). UptiP foils use leeway coupling along with elements of a surface piercing foil(inboard tip) to produce a sort of hybrid fully submerged foil.
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The foils I'm using on the amas are based on the Team New Zealand UptiP foils which are a real foil design breakthrough because they have "intrinsic" altitude control when used as a single main foil on a cat(or as an ama foil on a tri).
This is a succinct description of those foils by Magnus Clarke. A more complex description by Tom Speer can be found in "Sailing Foiler Design":

"The Emirates Team New Zealand system, which is really the basis for C-Class foiling, relies upon the use of leeway to moderate the effect of the lifting foil and to help make the boat heave stable. As the boat sails down the track and begins to fly it speeds up a great deal due to reduced drag. This extra speed allows for a great deal more lift to be produced by the foils and so the boat rides higher, as the mass is constant. As the boat rides higher there is less foil in the water. If the strut is principally responsible for limiting leeway there is now less of it to do the work of keeping the boat moving forwards. The boat automatically corrects for this by yawing, at which point the strut will use a higher angle of attack caused by the leeway to create a force equivalent to the wing's side force.
The leeway, however, has an effect on the effective angle of attack that the foil wing experiences. As the boat crabs sideways the wing- or relatively horizontal- portion of the foil sees a lower effective angle of attack and as such the lift produced is moderated or reduced until the boat itself reaches dynamic equilibrium. This is also aided by the inboard tip starting to breach out of the water-this reduces available area to create lift for the boat and also leads toward dynamic stability in heave."
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Oh I'm reading!!!! Lots to soak in. What are the general foil shapes used? Naca, mh, symmetrical?

Barry

 

Two that I'm familiar with: Speers H105 and the NACA 63412 but there are many more. I use asymmetric foils on the amas loosely based on the 63412 and symmetrical foils for the main, rudder foil, rudder and daggerboard. According to Graham Bantock and others model foils work better thin-6-7% t/c ratio. Mine are around 8-9%. Ian Holt uses even thicker foils on his Mini 40 trimaran RC models-and they work very well.
google !

 

We'll there I can cheat! I have compufoil so so I can drag me in there and take a look at em. And makes sense as they go down in actual size the foil has to go up. Course all my Reynolds numbers are based on air! So.....


Barry

 

Fire Arrow Foiler / MPX Foil System Testing and Development

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UPDATE: No sailing tomorrow........

 

Hello again. Video of action from Perth today with two Mini40s and my prototype one metre cat is here:
http://youtu.be/5BJjFZjauZo

I am trying active foils, controlled by wands on the one metre cat but currently am finding fixed foils to be more effective

 

Mini 40 Foilers!

Great stuff Ian! Wish you'd take some close up pictures of your foils. What are the weights of the tris and cat? Have you tried a wand system with flaps are were you moving the whole foil? Really enjoy seeing your boats!
PS-if you haven't already take a look at the Vampire cat in this forum. Kevin Elway and Alan Smith are involved. They believe that the wand controlled canted T-foils eliminate the disadvantages of "normal" t-foils(as pointed out by Greg Ketterman) and are less drag than UptiP foils when used in a single main foil/two rudder foil configuration.

 

Quick question? Since one is flying the hull? Could foils and rudders be outward hung to simulate effective beam? Might not be even be worth the effort, just thinking out loud.


Barry

 

Fire Arrow Foiler / MPX Foil System Testing and Development

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Barry, I'm not sure I understand you. On my boat ,the ama foils are as far outboard as possible on a very small ama and there is just a single rudder.
This system works with the main, wand controlled, foil allowing light air takeoff then immediately beginning to unload as the ama foil picks up more and more of the load. The mainfoil is then relegated to working with the rudder on pitch control and/or creating extra RM thru downforce.
Hope that helps.....

 

Fire Arrow IIRR(Fire Arrow 2, Race Ready)

After the next long all foiling video and after the self-righting tests I'm considering building a smaller version of the Fire Arrow: LOA about 48"(with adjustable rudder gantry) ,Beam 68" using many of the parts from the big boat recycled down in size with one of my favorite tools -a 5" grinder. That's the good thing about working with carbon it can be modified a hell of a lot easier than starting from scratch. The foils,approximately half the carbon tubes, main foil+daggerboard, rudder +rudder foil-all "adjusted" to be right for the smaller, lighter race version. The beam on the Fire Arrow is 1.22 times the length, on the smaller boat the beam would be 1.4 times length. That's one of the things that I've considered doing to the Fire Arrow because it's obvious, with the testing already done, that the system allows more beam with no downside except slightly more weight.
The Fire Arrow is a high performance scale model of a 19.5' full size boat. The 22.13lb all up weight is equivalent to the fullsize boat with 3 175lb people and 29lb of supplies. The new model would use the same technology as the Fire Arrow in an effort to show the potential of the foil system used on a dedicated race boat with no "curved piece" attached to the ama, a relatively skinny main hull and probably just a single cross arm like the F3. The new boat would be fairly light. It would have more SA than a Mini 40 or F48 because it won't be built to a rule. It would be built to test a race version of this concept. By "race version" I mean a boat built as light as possible with nothing to scale-simply the fastest 48" model that this technology will allow. This would allow continuous refinement of the foil system because sailing time would go up dramatically.
But I kind of like this boat and haven't made a decision yet. Certainly nothing will happen until Dan and I get a great foiling video and do the self-righting tests. This boat requires that I have help to get it sailing-I can't just take it out alone. The existing Fire Arrow would have to be dismantled and cut up to use the parts on the new boat because I can't afford to buy the material to build a new boat from scratch . The new version would be easy to handle(for me alone) and permit the next level of testing the MPX foil system with everything fitting in the car easily. We'll see......
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UPDATE: I discovered that I had saved the 48" cat hull and deck mold and the 3' ama hull and deck mold(from the F3) when we moved 8 years ago. So that means I can build a very, very light weight 48" main hull and two amas with a nearly perfect finish with zero sanding should I decide to go ahead with a smaller boat.