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

    ===============
    Thank you. I know the english language causes some of us problems and I'm sorry for dat.
    So the foiling you saw was a "spurt"?! Did you actually watch the Fire Arrow video?
     
  2. Marmoset
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    Marmoset Senior Member

    Not the same foils Doug is playing with but a single sided foil like Groucho has I suppose bypasses the described situation doesn't it? High outside low inside only with just the 2 sides.

    Barry
     
  3. Doug Lord
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    Doug Lord Flight Ready

    ===================
    Except that's not the way it works: if a foil is lifting the bottom is the high pressure side and the top is the low pressure side. If the low pressure side is subjected to high pressure lift will suffer. But, as is obvious, that doesn't mean the foil won't work........it just means there is a proven better way.
     
  4. Marmoset
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    Marmoset Senior Member

    Oh yeah I get ya, I mean no high pressure side, no low pressure side, it's not a wing so no lift. Might as well be a plate just dragging. I was just observing in the single fin case it's much like the case of left wing or right wing on a plane, long as airfoil is reversed lift is lift.
     
  5. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    Thats the thing: sailing foilers operate differently than airplanes because of leeway. It's taken me a while to begin to understand how important that can be in foiler design and to begin to understand how leeway affects the pressure distribution on a sailing hydrofoil.
     
  6. Marmoset
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    Marmoset Senior Member

    Aahhhh yeah, that's true! It'd be like constantly trying to make a wing fly at off angles.
     
  7. Gary Baigent
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    Gary Baigent Senior Member

    Not beating a dead horse (because I don't have out sloping asymmetric foils on my boat now), but they do work. A foil is a foil whether it slopes at any which way, still will provide lift. Ketterman had J type outfacing foils on his experiment, that is not the same as 40-45 degree angled foils. He is relying on the vertical upper section to counter leeway, different on 45 degree foils with a central hull dagger to counter leeway. His opinion on his Xboat that they didn't function - but in the photograph the float is lifted, admittedly with a lot of fuss, turbulence and spray.
    Go right back to the early pioneers, they had combinations of both angled in and out, like ladder foils on Williwaw - or the out facing 45 on the Morewood and other proa designs - or today on the angled up J semi V's on C Class, 32's and SL33's and others to come. What about the Wrong facing sections on those designs? Putting it simply from practical experience on full sized boats, they do work. May not be fashionable in some quarters - best to keep an open mind, no?
     
  8. Madrc570
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    Madrc570 Junior Member

    Outward facing foils

    Hi Gary, the outward facing foils work but not nearly as well as inward facing foils.
    Having Dihedral- inward facing allows the boat to be dynamically stable as the more it heels the closer the foil is to parallel with the water- creating more lift, the opposite occurs with adhedral and therefore the boat has a very limited heel angle before it can no longer stay on foils.

    This is at least is my understanding :)

    Regards
    Curtis
     
  9. Gary Baigent
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    Gary Baigent Senior Member

    That is correct, Curtis, Your point of dihedral lessening the lifting effect because the lee foil becomes more vertical but ... a foiler (at least mine) do not heel very much.
    On "conventional" in-facing foils, on a 45 degree angle foil design, not J's or L's, the faster you go, the higher the platform rises, and you get LESS stability because the platform foot base narrows with boat speed. That is why Hydroptere has an over square platform resulting from the very wide main beam.
    I fooled around with out facers because the faster you go the wider the platform becomes, hence you gain a more stable base, not less. But actually it was not necessary because Groucho is a wide platform anyway.
     
  10. Madrc570
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    Madrc570 Junior Member

    That's a very good point Garry!- I didn't really think of it that way- the widening of the platform with height :)

    I wonder whether an outward facing J or C foil might also be worth looking into...
    Mach 2 of my boat will probably hove some sort of experimental AMA foils like that!!

    Thanks

    -Curtis
     
  11. Marmoset
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    Marmoset Senior Member

    "That's a very good point Garry!- I didn't really think of it that way- the widening of the platform with height "


    That's what I was asking! Haha just kidding couldn't resist.
     
  12. Madrc570
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    Madrc570 Junior Member

    More on the outboard foils: leeway

    One more thing that I think has an effect on the performance of the outward foils is that for them to work the windward foil always has to be immersed.

    Due to leeway the pressure difference from the leeward foil would cancel out lift. The windward foil would have the opposite; lift and lateral resistance would increase with speed and leeway so without the windward foil in the water I don't think the boat would sail to windward...

    Doug- what do you think?

    -Curtis
     
  13. NoEyeDeer
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    NoEyeDeer Senior Member

    I assume you mean this one, first video in your post #1654.

    https://www.youtube.com/watch?v=4YBOEolFqiE

    Yes, I did watch it. All of it. The main hull doesn't get completely clear of the water until just after the 6 minute mark, and the boat is flying for about 20 seconds. After you tack it, it gets up again on the way back for about another 20 seconds, but seems rather unstable.

    I agree with the comments from Steve Clark and Daquiri. It's great that you've got it this far, and it's a good start, but it's only a good start as far as I can tell. I still think it'd be better to refine this model so it works well consistently, rather than dropping it and starting a new one.
     
  14. oldsailor7
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    oldsailor7 Senior Member

    Looks like you're getting there Doug.
    All you need is a bit more wind. :D
     

  15. Doug Lord
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    Doug Lord Flight Ready

    Fire Arrow Foiler / MPX Foil System Testing and Development

    ===================
    In the first foiling video, if you read the original commentary, the wind was very light -measured with a Davis windmeter at 5 mph or less(3 just after we launched) a couple of times before and during sailing. However, the waves were still there from the previous 14-18 hours of 15-18 mph wind all night down a 20 mile fetch and they were "bending around" the bridge about 400' to the left of the picture. In other words, the waves were bigger than would be expected for the light wind. On the reach back in there were good sized(for the model) quartering waves that caused her to roll once. In every instance that she flew she was 100% rock steady in pitch with a slight roll in waves. The roll she took on the way in was exacerbated by a powerboat wake that further amplified the waves. At no point was there anything remotely like "instability" and she was in complete control the whole time. She had a problem with tacking,as explained earlier, because of a radio programming issue-since corrected(maybe).
    Steve said:"You have not demonstrated, at least as far as I can see, the type of consistent and controlled foiling that say, Ian Holt, has achieved on his small trimarans. I would posit that this is the standard you need to reach before you can claim real success.
    While Ian has done a tremendous job with his Mini 40's comparing this boat with them is ludicrous. The Fire Arrow is a scale model of a 19.5' boat sailing with 3 people and supplies.It weighs roughly three times what a Mini 40 weighs and is NOT designed for topend speed but is designed for light air takeoff. For me, success was that first foiling video that showed a heavy foiler foiling in light air using a radical new type of foil system with two completely different altitude control systems-the first use of such a configuration on any boat anywhere to the best of my knowledge. And they worked perfectly for the first time in that video(see post 1744,next page). Sure there are improvements to be made-particularly considering that the rig was only developing 50-60% of its potential power. Those improvements have been made for our next test this Sunday.
    And again, for the record, I disagree emphatically with both their assessments and yours. Comparing this boat ,in any way, with a 6-7lb(?) Mini 40 race boat is an absurd comparison with zero merit.
    Latest Mini 40 video from Ian Holt: https://www.youtube.com/watch?v=5BJjFZjauZo&feature=youtu.be
     
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