Foiling radio control trimarans

Discussion in 'Multihulls' started by PerthMini40man, Jun 9, 2016.

  1. OzFred
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    OzFred Senior Member

    You can quote old advice, or you can look at current wand equiped foilers. The most popular wand foiler in the history of mankind, maybe the universe, which had tried strut mounted wands, now universally uses a forward mounted wand (lately as far forward as possible on a bowsprit) because it works better than mounting it nearer or on the foil. It's more complex, but far better at controlling altitude and pitch coupling is likely one reason it works so well.
     
  2. Doug Lord
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    Doug Lord Flight Ready

    Two of the newest fullsize cats use different wand systems: the S9 uses wands mounted forward on each hull ,the Whisper uses midship wands mounted on each daggerboard. Neither of these rely on differential wand movement for most of the RM because they are too narrow and that would be draggy. Both these boats get RM assist from the foils at various times. The Vampire one off cat uses yet a different system: it retracts the windward foil sailing on only the lee wand controlled mainfoil.
    For differential wand movement to create most of the RM efficiently the platform needs to be square or oversquare.
    For RC boats the F3 was the first production RC foiler and one of the first to use wands. It was 56" LOA and 72" wide and the foils provided all the lift and the majority of RM. The RC Test Model Fire Arrow uses a single mainfoil with dual wands(that act as a single wand) and can develop a great deal of downforce to add to righting moment. The wand system allows the mainfoil to unload starting just after takeoff up to the point where downforce is required.
     
  3. Doug Lord
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    Doug Lord Flight Ready

    Rave wand animation:
     
  4. PerthMini40man
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    PerthMini40man Senior Member

    IMG_7248.JPG IMG_7257.JPG IMG_7258.JPG IMG_7261.JPG The boat is steadily getting better. Yesterday we had the best breeze so far, but I did not take number #3 rig with me to the lake - big mistake. It was a classic example of trying to sail an rc trimaran with too much sail area, and failing. Video is here:

     
  5. PerthMini40man
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    PerthMini40man Senior Member

    Here is the previous week's sailing



    FB Cover 2.jpg
     
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  6. UpOnStands
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    UpOnStands Senior Member

    Seems as if you are exceeding the speed limits of your foils. Can you reduce foil thickness and chord while increasing span? Together with some form of active camber adjustment as you mentioned before?
     
  7. PerthMini40man
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    PerthMini40man Senior Member

    I cannot reduce the foil thickness but I can increase the chord, but would would a greater chord produce more or less speed? The fast planes have smaller chords. What do you mean by "span"? Distance between the foils? No, cannot adjust that on this boat. "Span" = length of the foil? yes could make them a little longer
     
  8. UpOnStands
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    UpOnStands Senior Member

    By span I mean the length of the foils - so longer foils that are thinner both chord wise and thickness. If possible. Planform/thickness taper?
    The boat is so light relative to the sail area that it ends up dancing on the foil tips which of course is not so stable.
    In real life we'd be reefing to handle the stronger winds.
    Your work to date is impressive. If I had access to suitable water/wind I buy one.
     
  9. PerthMini40man
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    PerthMini40man Senior Member

    Understood. The problem with longer foils is that as the boat rises the beam (between the foils) reduces. I'll take some closeup photos of the foils later and put here for you to look at
     
  10. PerthMini40man
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    PerthMini40man Senior Member

    I recorded 24 KPH on the GPS on Sunday. That is respectable, as the top speed I have ever recor IMG_7241.JPG ded is 28.8 KPH. 30 KPH is my target
     
  11. UpOnStands
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    UpOnStands Senior Member

    Understood. And of course the boat's righting moment falls as hull rises. The foil COE moves more inboard as the boat rises.
    over 20 kph, time for active foil control?
     
  12. OzFred
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    OzFred Senior Member

    It would be interesting to see how you make your foils. Do you have any "how to" images or text?
     
  13. PerthMini40man
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    PerthMini40man Senior Member

    If I told you I'd have to kill you! Its a trade secret right now .............. It took Dave quite a few beers to work out how to make them. Couple of pics of two of the foil types attached. I have been using the blue ones to date. The orange foils are longer will test these on Sunday
     

    Attached Files:

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  14. UpOnStands
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    UpOnStands Senior Member

    Thanks for the photos.
    Suggested clip line shown on top foil. For strong wind days only?
     

    Attached Files:


  15. OzFred
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    OzFred Senior Member

    Fair enough, I have some ideas but making them accurately is a challenge. Maybe some questions that you can answer:
    1. What section are you using? If you can't reveal that, is it symmetric or asymmetric?
    2. Is the "tang" of each foil is the same so you can swap them in and out easily?
    Thanks!
     
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