Quant 23 Foiler Scow

Discussion in 'Sailboats' started by Doug Lord, Jun 8, 2015.

  1. David Cooper
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    David Cooper Senior Member

    I remember one recent thing I read about the Q23 commenting on there being issues with the directions it had to go in while foiling, thereby hinting at why it might not be winning races. It gave no concrete details though and I forget where I read it, but it was something linked to by Doug, probably in this thread (and it was written by one of the designers).
     
  2. OzFred
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    OzFred Senior Member

    Skiffs in general become difficult to sail quite quickly in breeze if you're doing anything other than windward/leeward courses. The boats are designed for a narrow range of apparent wind angles and to be steered through gusts and lulls to maintain it. Sailing too square is hard work and not very fast, too deep is just slow.

    Foiling magnifies the effects. Since most video of Quant 23s foiling is in fairly light breeze and flat water, the only real way to tell if it's going up or down wind is whether or not the kite is up (and it may even work upwind in certain conditions, a la the foiling Nacra 17). That's because the apparent wind is in a very narrow range and the sail trim is quite similar for up and downwind, so it's hard to tell between footing a bit upwind or going for speed downwind.

    I expect the Quant does quite will on windward/leeward courses in breeze they can foil in, but in other types of race where they are restricted to sailing specific angles they are at a disadvantage. A foiling Moth is almost impossible to sail on a square reach in a gusty 20kn, and not much faster than an Opti dead down wind 4kn. So if you're forced to sail those angles by the course, you may be beaten by a well–sailed Laser (and thrashed by any other skiff). But in a steady 10 to 12kn they'll beat almost anything under 7m, regardless of the course (excepting kites of course).
     
  3. Doug Lord
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    Doug Lord Flight Ready

    Dominion 2-HW*---"A" rig fitted today. Modern version of a gaff allows for an upper outhaul which makes a big difference on a sail with a big head. Just need to finish the Trapeze Power Ballast System and she'll be ready to fly.
    * inspired by the Quant 23 foiling keelboat and by Dominion(1898)

    "A" Rig:
    D2 A rig 1st set up   12-19-2017 003.JPG

    "B/C" Rig:
    D2  8-11-16 012.JPG
     
  4. Doug Lord
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    Doug Lord Flight Ready

    Quant 23-4 modes:
     
  5. Doug Lord
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    Doug Lord Flight Ready

    Dominion 2-HW inspired by the Quant 23 :

    Trapeze Power Ballast System:
    D2 TPBS--3-31-18 mostly done 001.JPG
    D2 TPBS trial fit--pivot  2-16-18 003.JPG

    FOILS:
    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
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  6. Tink
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    Tink Junior Member

    The video above lead me this one

    At about 1.20 the foil is almost skipping on the water, it is certainly very close to the surface of the water. Clearly this type of foils don’t have fences, how do they operate so close to the water and not suffer from ventilation?
     
  7. Doug Lord
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    Doug Lord Flight Ready

    They're good to about one chord below the surface but they can develop lift from planing.

    Quant 23 Benoit Marie 2.jpg

    Quant 23 and award.jpg
     
  8. OzFred
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    OzFred Senior Member

    They do, but the size and orientation of the foil means it can still generate quite a bit of lift acting as a planing surface.

    T foils are much more efficient (and hence much smaller) and are much more affected by ventilation (basically if they ventilate at all the boat stops foiling). T foil monohulls are also much harder to sail, particularly if they require more than one crew (there are probably fewer than 10 in the world that sail at all regularly).
     
  9. Tink
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    Tink Junior Member

    They seam quite stable as they change lift would it be fair to say the lift to drag ratio of the quant foil when foiling and planning is similar?
     

  10. Doug Lord
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    Doug Lord Flight Ready

    I wouldn't think so.
    And as to a "T-foil" being more efficient than a Welbourn foil-I doubt it: the Welbourn foil is the only foil that I know of that doesn't develop lateral resistance as well as vertical lift-it's 100% vertical lift. Further, depending on how the t-foil is sailed* it can develop drag due to having high and low pressure on the same side of the foil -something that never happens with a Welbourn foil.
    *this can be reduced by sailing with veal heel which unloads the vertical fin to some degree.
     
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