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

Fire Arrow Foiler / MPX Foil System Testing and Development

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That wasn't the rigs problem, Paddy-that was my problem. On this kind of boat where I want very fast sheeting speed and have a rig that is very powerful the biggest RC winch available is not able to handle it unless the sheet is led horizontally so the main sheet does nothing to shape the sail or keep the forestay tight. I have the right adjustments for the downhaul, a super powerful vang and a peak halyard and an outhaul adjustment at the top and on the foot. In this video the little device I experimented with GCD(gaff control device) bent, slacking off the peak halyard allowing loads of twist, and the purchase wasn't good enough to start with.I have adjustable shrouds(led way aft and outboard) to take care of the forestay, which I did tighten this time. But mainly, I was so into getting the first foiling video that I simply didn't use the adjustments I had and/or they didn't work as well as they should have. All that is changed now AND if I use the adjustments that have been reinforced where necessary, that and the new battens will make a huge difference in the next video. I think I was sailing with 30 to 50% less power than the boat has available. And the video was shot in a 5mph wind! (Measured with a Davis windmeter)
Oh, and now I have a reefing system that works by removing a section of the wing mast and rolling up the foot of the main. All the stuff I did since that first foiling video is summarized in the post at the top of the last page(page 120)-it is a summary of what has changed since the pictures below were taken.
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That's fine Doug. I knew you would be getting on top of it.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

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The more I've thought about this the more I like it. IF it works it would replace the current wand based foil for "sport" applications-the wand would probably still be used on racing versions of this concept. Seems like it stands a chance of working resulting in downforce only when it is needed. Question is will it be too critical leading to a sort of porposing? Only one way to find out.
The cool thing is that a test foil can be made and attached to the boat just like the current fin/foil. The wands don't have to be removed-just simply retracted as shown below.
Bottom rough sketch shows my latest thinking on the concept with fences on each end of the center upside down asymmetric section. From the fence outboard the foil would be symmetric transitioning to asymmetric toward the tips. That section of the foil would begin to have washin from the middle of the distance between the fence and tip, approx. 3 degrees.
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The combination foil with an upside-down asymmetrical section in the center and with symmetrical sections transitioning to +3 degrees of washin toward the tips on each side will develop lift from takeoff due to the initial pitchup of the boat through to the main hull flying. The foil will control altitude in a similar manner to a surface piercing foil. As the main hull flies and more of the foil comes out of the water the whole boat will level off and begin to slightly pitch down.
And if the relationship of the asymmetrical section to the symmetrical sections is correct the center asymmetrical section will begin to develop downforce which would increase as speed increases , moderated by the influence of the outside sections. At least that's the idea.......
Note: the heeling force on the boat will reduce the downwards load on the foil to close to zero when the downforce kicks in.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

More on the automatic main foil: I'm designing the model version now and the way to set it up follows, based on the last sketch of the last post:
1) the sections of the foil outboard of the fences will twist(washin) from a nominal AOI(angle of incidence) of 2.5 degrees to an AOI close to the tip of +6 degrees,
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2) the center section consisting of an inverted asymmetrical section will be set up with the nose up 2.5 degrees.
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3) this is based on an expected(will be measured exactly in our next tests) 2.5 degree pitch down at speed, which will:
a.cause the inboard half(the immersed portion) of the outboardsections to have an an angle of attack of zero degrees, and,
b. cause the nose of the asymmetrical center section to operate at an AOA of zero degrees, which, if a similar foil to a 63412 is used, cause downforce to be developed with a section lift coefficient of about .3.
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The viability of this concept depends on, among other things, knowing the exact pitchdown of the boat at speed. This is where the damn no good go pro would come in handy or one of the cheaper versions-- to be able to watch the wand lever to tell exactly when the foil begins to develop downforce. It's probably not possible to see the wand with sufficient accuracy to tell that this has just started.

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I like the idea of fences!


Barry

 

Fire Arrow Foiler / MPX Foil System Testing and Development

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Do you think the foil will work?

 

Doug,

I have three concerns.

Item 1:

Foil drag near the surface may be higher than you want.
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Item 2:

The big discovery of ETNZ was that leeway could be used to change the AOA of a lifting foil.

It points out the importance of factoring leeway into understanding the lift available from a not quite horizontal foil. This makes accurate prediction of effective AOA very hard.

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Item 3:

The center of your main foil should probably be either symmetric or close to it. You want positive lift from the foil for some modes. The asymmetric foil section in your picture is probably not optimum for the function you have described.
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For you boat, I do not understand why not just continue to use your tee foil with a flap + wand. With a flap, you get an assy section with correct camber for both up lift and down lift.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

Thanks, Paul. The main foil, with dual wand controlled flap, is unquestionably the best for performance. But since this is a scale model of a "sport" boat and not a scale model of a race boat, I've been trying to see if I could come up with a surface piercing main foil that could somehow be designed to produce downforce before the main foil flys due to heeling force- to further simplify the foil system.
Right after takeoff, whether the main foil is a surface piercing foil or fully submerged wand controlled foil, it begins to unload with more and more of the load taken by the ama foil. That's all automatic. And the characteristic of the boat as it speeds up is to pitch down. My use of the asymmetric center section is to take advantage of the fact that an upside down asymmetrical foil will generate vertical lift(an airplane with an asy wing can fly upside down) with the right angle of attack and that while upside down it will generate downforce with a low positive angle of attack or zero positive AOA, while the inboard sections* of the symmetrical foil are at zero degrees angle of attack producing no vertical lift-all this when the boat is at max pitch down.
Whats hard in studying this is to remember that the heeling force is increasing as the boat speeds up and pitches down. And that the heeling force unloads the main foil.
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At max pitch down there is a symmetrical foil and asymmetrical foil cruising along right next to each other ,separated by fences. The symmetrical foil is at zero degrees AOA and so is the inverted asymmetrical foil. Because an asymmetrical foil can generate vertical lift at zero degrees AOA, it can generate downforce when inverted at the same angle of attack!
So I guess I think it's ,at least, worth a test.....
*which are the only portions of the symmetrical foils that are immersed at that point.

 

I think it should, but you have a way better grasp than I on adequate foil sections to lift in water. I do know the sections are thick enough to life in air so water yeah, I just don't know how much is enough or too much at that scale. I'm trying to study though!

 

Just adding, if I had foils used I can generate All the numbers and such, but again that's air not water. I still need to research what calculations, if even applicable! Are required in water.


Barry

 

Fire Arrow Foiler / MPX Foil System Testing and Development

Thanks, Barry. The fun thing with hydrofoils is that they operate at or near the air/water interface so all kinds of weird and wonderful things can happen.....

https://www.youtube.com/watch?v=7Mok3d4KiMI

 

Now that was a cool vid!

 

Fire Arrow Foiler / MPX Foil System Testing and Development

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Thanks. Had a little trouble tacking, but that was due to a programming issue with the radio that I screwed up....... But flying is flying! Especially when it's done with a heavy boat in light air-5mph measured........

 

That was the cool part, you could clearly tell it was semi flying even when it was down. Like a ballerina crossing the room! Haha

Barry

 

This is 21st Century Radio Control on steriods:

But in true form, he's clear he is keen to dish out a thrashing to whoever takes him on in a Vodafone virtual gaming event in which contenders use smartphones or tablets to sail around the Hauraki Gulf.
The best entrant will take on Spithill for real as they sit side by side in a helicopter armed with Samsung Galaxy Note 4s using Vodafone's 4G network to direct Team Vodafone Sailing's 60-foot trimaran.
Spithill is convinced he will get around the course faster than any New Zealander, despite having not sailed on the Hauraki Gulf competitively since the 2002 America's Cup.
"Whoever wins it, we go up in a chopper ... and the app on our phones is linked to the rudders on the boat and we both get to do a couple of time trials each," said Spithill from his home in California.
"This 60ft trimaran is one of the fastest boats in New Zealand and to be doing it by remote control and flying from a helicopter - it doesn't get much better than that."

http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11343777