V-44 Albatross World Speed Sailing Contender

Discussion in 'Multihulls' started by Doug Lord, Sep 29, 2010.

  1. Doug Lord
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    Doug Lord Flight Ready

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  2. Marvout
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    Marvout Junior Member

    Aren't they only going half way with the concept? (I don't mean this facetiously at all...) Wouldn't you be able to get both wings up in the air, control them separately and get twice the drive area? Looks like there are four separate control areas. It appears like each wing has an upper and lower section. Run three of them for drive and the fourth for balance. A kind of fixed wing biplane Moth on steroids.

    Marvin
     
  3. tspeer
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    tspeer Senior Member


    No, the lift on the other panels would have to go the opposite direction to produce drive. The way they've arranged it, the horizontal wing to leeward produces upward lift and opposes the heeling moment of the vertical wing. It also helps cancel the trailing vortex at the foot of the wing for reduced induced drag.

    The ideal case might be identical lift distributions on the two wings. Then there would be no net heeling moment and the net force would be along the bisector of the two wings. Of course, the wind conditions on the two wings will be quite different, and the spanwise lift distributions will be different.
     
  4. Marvout
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    Marvout Junior Member

    I guess I had presumed the (air) foils were symmetrical and could be trimmed for sailing either way. If they are asymmetrical like a plane's wing then what I suggest wouldn't work.

    Marvin
     
  5. tspeer
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    tspeer Senior Member

    The sections looked asymmetrical in the renderings. I think that was one of the reasons for going with a flip-tacker configuration.
     
  6. Marvout
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    Marvout Junior Member

    The stresses in that design must be quite high. The impact of that thing landing must be pretty harsh. Or at least it has the potential to be.

    I wonder if the cockpit is self leveling? Could be a bit disconcerting if you forget to 'tack' the cockpit.

    MH
     
  7. NiklasL
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    NiklasL Student member

    Looks like a pitchpoler because of the short length.
     
  8. cavalier mk2
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    cavalier mk2 Senior Member

    I wonder how it would work in a pacific configuration with the horizontal wing suppling downforce/upforce when needed .
     
  9. Munter
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    Munter Amateur

    I wonder if a compression strut between the wings would be more effective than a massively reinforced joint between the wings?
     
  10. RHough
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    RHough Retro Dude

    Tom, have you looked at the pitch stability information they posted? I'm struggling with how that is going to work. It looks more like a pitch instabilty system me?

    R
     
  11. Doug Lord
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    Doug Lord Flight Ready

    V-39

    Randy, what do you see that leads to pitch instability? Maybe its staring me in the face and I don't see it?


    They say:

    " When the hulls are flying, the V-39 achieves longitudinal stability from a nose up pitching moment gained by a relatively forward centre of lift from the wing in ground effect and a relatively aft centre of gravity.

    A degree of water ballast will be present in the stern of the main hull to maintain an aft CG.

    Finally, the small hydrofoil at the base of the active rudder maintains the balance"



    click on image and then again on resulting image:
     

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  12. RHough
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    RHough Retro Dude

    First consider what would upset the vessel in pitch.
    The nose down pitch from thrust is balanced (literally) by the nose down pitch from the aft CG lever.
    What happens as the wind speed changes in gusts?
    Gust = greater trust = pitch down
    pitch down = CG forward as wing rotates forward on pitch axis reducing (over powering?) the stabilizing effect of the aft CG lever = more pitch down
    Pitch down = hull/fuselage frontal area increases forward of the CG = more pitch down

    As the vessel pitches down the stabilizing force of aft CG is reduced and each degree of down pitch increases the pitch down force. The pitch down forces are not linear, whist the stabilizing forces are. This requires active input.

    Now look at the CG placement and the location of the T foil. Both the trim weight water ballast and the T foil are off center. Any stability moment in pitch also produces a roll moment and a yaw moment.

    Now we have:
    Pitch down = need for pitch up correction
    Pitch up correction (down force from T foil) also adds windward roll and weather yaw (from greater drag induced from down force)

    Is the vessel sable in roll?
    The total lift is somewhere to leeward of the CG, if the vertical height of the thrust vector as shown in the side view is extended to the combined lift vector shown on the front view the thrust acts at a point to leeward of the CG.
    Gust = greater lift = windward roll + pitch down
    Windward roll = increase AoA on T foil = up force from T foil
    Upward force from T foil adds to pitch down.

    How about yaw?
    Gusts increase lift = pitch down + windward roll + weather yaw
    Weather yaw = greater speed at WIG tip as it rotates = increased windward roll ...

    I could spend more time trying to figure out if the vessel is stable on any axis but you get the idea.

    Stability in 3D is an aircraft thing. Stability has a static aspect and a dynamic aspect. Consider a broomstick. Hang the broom stick from one end. It has both static and dynamic stability. If you push it from vertical it will return to vertical and settle back to it's original position (unless the suspension point is frictionless and there is no air resistance). Now suspend it from it's centre of mass. It will be stable in any position but will not return to any position. When the suspension point is moved to the bottom, it will be stable only as long as the centre of mass is directly above the suspension point. Sure it is possible to walk around with a broomstick balanced on your finger tip, but I'd hardly describe it as stable.

    I just don't see this ending well. I could be wrong and I don't see something obvious ... :confused:

    R
     
  13. cardsinplay
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    cardsinplay da Vinci Group

    I take it, then, that you've looked at the CV's of these guys, as well as their invested sponsors and you still think there's something terribly wrong?

    Hmmm....


    I did see the caveat.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    ================
    This isn't an answer but its-maybe the begining of an answer. I looked in Darrol Stinton's "Design of the Airplane" for his remarks on forward sweep.
    1) " forward sweep avoids premature tip stall, because the root stalls first. Ailerons tend to remain effective, but pitch up still occurs. However, forward sweep has an adverse effect upon directional stability.........."
    2) " Forward sweep causes vortices outboard to be shed ahead of those inboard. Tip stalling is suppressed by off-loading outboard sections. The spanwise lift distribution of a forward swept wing is nearly elliptic and further forward than for one swept back. This, with root losses helps to shift the aerodynamic center 7 percent to 10 percent further forward than for a swept back wing."
     

  15. RHough
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    RHough Retro Dude

    When was the last time I have been proved wrong and was not happy to learn from the experience?

    Have you never seen a design error from someone with good qualifications?

    I did not say "terribly wrong" did I?

    Let me be very clear, I don't see obvious positive dynamic stability. It is entirely possible to fly such a vehicle, helicopters are the most obvious example.

    Possible to fly and able to set a record are two different things. The Monofoiler speed record program got farther along than this one and I have not seen a full scale machine yet. Not saying we never will but it has been a few years. There are videos of proof of concept models.

    Sponsors?
    Design software, engineering consultants (the employer of the project founder), and a laptop with x-foil ... equal invested sponsors? No mention of money?

    The CV's?
    Egineering Lead/Founder works for Consultant Sponsor
    Project and Marketing Lead old school chum of founder
    and a CFD guy that has sailing experience ...

    Keeping a three person team structure flat is not much of a challenge. I don't see much experience actually building anything and no past successful designs are cited other than models. Hell if the models that I've designed and built count I can I list them and impress you? :p

    The single most impressive statement they make is this one:
    and second is:
    These statements are the ones that lead me to look closely at the project, since I feel that they indeed have a good handle on what the limits and challenges are.

    Randy
    Free Flight and RC Model Aircraft Designer and Builder
    RC Sailing Vessel Designer and Racer
    LSF Level 1 Glider Pilot
    Racing Sidecar Engine Builder, Chassis Designer and Builder, Professional Racer
    Crew Chief Sports 200 team and Spec Miata team
    Trimmer, Navigator, Tactician 2 time YRA Champion Crew
    USSailing Certified Race Officer

    Are you impressed yet? :p

    LMAOROTF
     
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