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

Discussion in 'Multihulls' started by Doug Lord, Dec 28, 2010.

  1. Doug Lord
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    Doug Lord Flight Ready

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    Last edited: Feb 5, 2015
  2. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development--"curved piece"-TSA

    This post below(8/2/11) is the first mention of the "curved piece" and the creative black hole I have faced on what to actually call the damn thing. Its design and function is critical to the Fire Arrow design and concept and it deserves a name. :
    ==============================
    Late at night two days ago I was thinking of a 15' version of the Fire Arrow and was troubled once again by calling such a crucial piece in the ama function and design a "curved piece". Then a light flashed on and I came up with a technically correct name for the ama + the "curved piece" : a "two-stage ama". The reason "two stage ama" works is because the curved piece actually is part of the ama though quite distinct from the ama hull. And in sailing, the buoyancy of the ama hull and of the curved piece affects the RM of the boat in two distinct stages: Stage 1- when the ama hull is immersed the RM is enhanced by the 6lb(about 280lb full size) of buoyancy of the " ama hull", Stage 2- when the "curved piece" is immersed the RM due to the immersion of the ama hull is doubled by the immersion of the "curved piece".
    So from now on this feature of the Fire Arrow will be call a Two Stage Ama(TSA or 2S ama). Interestingly, in the testing done so far even in the overpowered conditions of the second video the second stage of the ama(the curved piece) has not been submerged. This hasn't been tested yet but ,theoretically, the high dihedral crossarms coupled with the Two Stage Ama(TSA) should allow self-righting from at least 90 degrees(if it ever gets that far).
    The 2nd stage of the ama(curved piece) is designed with about the same buoyancy as stage 1(the hull) and together they create fairly high static RM coupled with the over square beam and high dihedral crossarms. But it is stage 2 that determines the run angle of the planing ama surface and of the ama foil. I even considered making the junction between the two adjustable
    so the ride angle could be adjusted. The foils AOI(angle of incidence) is adjustable but the ride angle of the planing surface is not-at least on the Test Model. It could be adjustable on the full size version w/o a whole lot of trouble.
    But,again, whats really cool about the Fire Arrow concept is that sailing(foiling)- the main and rudder foil working together control the ride angle of the planing surface and the foil! In other words neither can pitch up or down on their own.

    click for best view:
     

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  3. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    ======================
    It's interesting how sometimes you can discover something new even though it's been right in front of you for a long time. That's the case with a characteristic of the Fire Arrow and it's ability to self-right. The original designed sailing weight was 16.688lbs,its final sailing weight was 21.13lb. At the 16.688 lb weight,3.9lb was "crew" and 3.9lb was ballast to go in a bulb at the juncture of the mainfoil and daggerboard. The original weight plus the excess weight-4.44lb.(caused by the way the boat was built and finished) was 21.13lb.,which, without ballast, would equal 3 175lb people and about 24 lb of miscel. supplies. I mentioned, just a little while ago, that I probably couldn't test the self-righting of the boat as I had originally hoped to because of the extra weight and that is probably true though we'll try adding an extra 3.9lb to the fin(removably) and see what happens.
    I've mentioned in several posts what went wrong and what went right-the most important part of "what went right" was that the boat foiled in a 5mph breeze with all that extra weight. And that means that if the boat had been built to its original design weight it would have surely foiled(fairly obvious) and what that means is really cool: not only would the boat have foiled it would have been likely to be self-righting! That means that this boat is real close to being a self-righting keelboat FOILER! And we're going to try it with an extra 4 pounds on the daggerboard to see what happens-there is a high likely hood she would foil with the extra weight and she might even self-right from a pitchpole.
    When I first started building models I always built them too heavy if I did an excellent finish on the boat-the only way for me to build a boat very light and with an excellent finish is to build tooling and build the boat out of molds-that's how I did the F3-the worlds first production RC foiler that I designed with the Bradfield foil system. I built six of them all coming out about 6.5 lbs for a 56" long by 72" wide foiler with 1668 sq.in.of sail.She would also take off in a 5mph breeze or lighter.
    The point of this is that I now know for sure, beyond any shadow of doubt, that a self-righting foiler is a realistic possibility-maybe not the Fire Arrow now but I still have a bunch of tooling that I can use to build a much lighter version of the Fire Arrow that I know for a fact will foil and be very highly likely to self-right from a pitchpole! The geometry of the Two Stage Ama and high dihedral crossarms makes it virtually impossible for the boat to capsize in the normal way-in fact the boat is self-righting from a knockdown past 90 degrees-with no ballast! And with ballast she would be self-righting from a pitchpole.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development--Self-Righting

    Based on the thinking I've done recently(last post) I'm going to set a new target -not specifically for the current Fire Arrow but for the project as a whole
    and that is to prove that a self-righting multihull foiler is not only possible but that it can work well. The only limitation I can see so far is that the boat would have to have an intact mast after a capsize or pitchpole. There may also be a limitation on the number of crew on the boat. That it functions when the boat is singlehanded is the most important criteria. For self-righting to work, I think something like a Two-Stage ama is important as well as that the total buoyancy of the Two Stage Ama(hull+ curved piece) should be less than the total weight of the boat. That means at some point in a "hand of God gust" that the 2S ama would fully immerse and that's good because of the high dihedral of the crossarms which means that there would be righting moment past 90 degrees. Downsides include the fact that an oversquare platform like or similar to the full size Fire Arrow would hit bottom in this scenario if it actually went to 90 degrees in water less than 12' deep. In a pitchpole the maximum draft would be 9'. In shallower water than this the boat might hit the bottom but it would be impossible for a capsize or pitchpole to last more than a few seconds while the boat rights itself.
    And since the definition of "self-righting" has been stretched by some into meaning that it also includes action taken by the crew-I want to make it clear that what I'm talking about is automatic self-righting-requiring no action by the crew.
    So far we know that the foil system works very well and when we start getting video again that fact will be come obvious to anyone. Once we have that video we'll make a series of static tests to see exactly how much weight it will take to make this boat self-righting from a pitchpole.(and if it needs ballast to recover from a mast in the water capsize). In only the second video the boat righted itself from almost a 45 degree pitchpole-I want to find out what it will take to come back from a 90 degree-mast in the water- pitchpole. This boat may be too heavy for this to work in which case lighter boat using the same system will be built. This kind of testing can produce 100% accurate results for the full size version of the boat.
     
  5. Doug Lord
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    Doug Lord Flight Ready

    A funny thing just occurred on my trip thru the internet-the picture on the left is a new Kite foil found on the SA front page and the pictures on the right are the
    very experimental Ctwist batfoils that will be used on the D4Z cat and if they work there a version may replace the wand controlled main foil on the Fire Arrow:

    Story on the kite foil-

    This is a picture of the best kite racing foil today! It is made by SPOTZ which is a french company that has been pushing the leading designs and technologies of kite foil racing since the start.
    I am writing this article to point out how different they look from a Moth foil.

    I have tested a lot of different shapes, sizes and curves and have found that, the more curve that we add to our kite racing foils, the more stable it becomes with pitch and roll. A moth foil is very flat without much curve if any and I think this could be a major reason for even best sailors having a hard time in over 20 knots with big chop, for example; in Sorrento.

    I am definitely not an expert on foil design, nor am I an engineer, but I ride a hydrofoil almost everyday in San Francisco Bay and a flat foil wouldn’t work in over 10 knots for me!!??
    – Anarchist Joeey.
     

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  6. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development--gooseneck/vang

    This is a new type of vang (to me) that I just came up with for the D4Z cat.
    However, I wish I had thought of it for the Fire Arrow! Any new version of the Fire Arrow will use it and a large pocket luff main instead of a wing mast.
    The idea is to get the boom as low as possible while allowing the Trapeze Power Ballast System to move side to side. The top of the boom has an endplate mounted to it and the sail will be sealed to the endplate as best I can with,preferably,no gap. The mast and boom rotate together on a bearing like surface but the boom can pivot when the turnbuckle is tightened.The turnbuckle fits inside the sock luff of the main:
    UPDATE: New name for the thing: "vanganeck" and pictures below as of 2/13/15:

    click-
    Pictures, L to R-1-Sketch, 2&3-roughed in part, 4&5-finished and painted(2/14/15)
     

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    Last edited: Feb 14, 2015
  7. basil
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    basil Senior Member

    Doug,
    I think your vang design is quite innovative - but how do you adjust it once the sail is fitted over it? Won't be much use on a rig that uses spreaders. Which if you don't already have would help with forestay tension on the FA.

    And finally has FA foiled for any more than a few seconds at one time yet?
     
  8. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    Thanks. The D4Z sail doesn't fit over the "vanganeck". And I don't use spreaders-if anything perhaps diamonds but I doubt they'll be necessary.
    ---
    The Fire Arrow foiled perfectly several times, including upwind(see long video) on July 24,2014. That day the wind was very light and when she foiled the wind was was about 4.4 knots(5mph). We ran out of time or if the wind had come up she would have foiled all day. There was zero problem with the foils, in fact, both altitude control systems worked flawlessly. The only problem that day besides the main tension adjustment was the rudder dual rate and expo being set too high with no way to shut them off making it hard to tack. Skipper inexperience with this boat was a contributing factor to the tacking problem. That's been fixed ,I think.
     

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  9. Doug Lord
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    Doug Lord Flight Ready

    RC Foiler Experiments

    Here are a couple of RC foiler experiments by Ian Holt in Australia-a modified off the shelf "Skate" trimaran and at about 1:10 in, a one meter cat with wand controlled main foils. The wands appear to move the whole foil, rather than a flap. The The foil system seems to have a lot of potential!
    https://www.youtube.com/watch?v=Bs99rjdQc3M
     
  10. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    This is something I've been meaning to do since July: go thru the long video and write down every time she foiled regardless of how short a time.
    The two major times were: 11 seconds on port tack and 15-16+ on stb tack starting at about 6:20 in. The boat was still foiling when she went behind a tree so that time is arbitrary. She would have foiled to Miami if land wasn't in the way!
    There was a 10 second bit early on where she was semi-foiling on stb tack and two times at 3 seconds each and one foiling for 4 seconds. Once early she popped up for about one second upwind. About 38 seconds total in very unfriendly conditions with marginal wind- very light air-measured at 3-5 before we started and once after at 4mph and left over waves from the previous night. Interestingly, she tacked several times as the video started but had trouble near the end due to bigger waves cause by a powerboat wake. The waves cause trouble when they are "bigger" than the wind, that's for sure.
    Can't wait for the upcoming(April-May on) video!
    https://www.youtube.com/watch?v=4YBOEolFqiE
     
  11. Darth Reapius
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    Darth Reapius Junior Member

    How on Earth does "11 seconds on port tack and 15-16 seconds" mean "She would have foiled to Miami if land wasn't in the way!"
     
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  12. Doug Lord
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    Doug Lord Flight Ready

    At the end of the day, when those times were recorded, the wind had come up sufficiently that the boat could foil downwind easily. If I hadn't had to stop because of land she would have kept on foiling as long as the wind stayed up.
    The point is that the only thing that caused her not to foil was no wind-if there was wind she would foil-no wind,no foiling. The foil system was working perfectly.
     
  13. Darth Reapius
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    Darth Reapius Junior Member

    I think your definition of "working perfectly" isn't the same as other sailors... I sail minimum 3 times a week, and I never think the boat is working, in quotes, perfectly... Serious on water hours are required for even minor refinement. TBH I don't really care what anyone says about anything else, but regattas are won by the people who put the most time in off, and most importantly ON the water. What would you say if you put 10 hours in, got 30 mins foiling, then refined things, put heaps and heaps of time into practising manoeuvres, rake, rig, and more adjustments, got it out again, and got 3 hours foiling in 10 hours on the water. Would you look back and say damn! Maybe it wasn't even close to start, 30 minutes is nothing, then looked back and said 30 seconds is nothing...
     
  14. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    One of the most important characteristics of this test model will be the same on the fullsize 19.5' version and that is take off in very light air-5mph for the test model and about the same for the fullsize version.
    It has been perfectly acceptable to me to lose some top end speed to have the boat foiling in light air-most places in the US have a predominance of 10knots or under wind. In my opinion, other production foilers have failed when it took 12-15 knots of wind to start foiling-that definitely will not be the case with this boat.
    However, there may be a solution: removable foil tips. I came up with this a long time ago and it may be part of the solution in increasing potential top end speed. The downside is that if you go out with the shorter foils low wind speed takeoff will be compromised. And foil effectiveness is definitely compromised by reducing span, so this has to be looked at very carefully. Another test down the line.
     

  15. Darth Reapius
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    Darth Reapius Junior Member

    Are you seriously saying that time on the water means nothing?

    Why not just do the moth thing and have 3 different size foils, light, medium and heavy breeze?
     
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