Twin Wing Landyacht Concept

Goal - 100 kt/200 kph/120 mph with course racing landyacht

    • Current World Record is 94 mph with one-way asymmetrical yacht

Problem - Landyacht speeds are limited by three factors:

    • stability - rolling (heeling) moment limits available aerodynamic force
    • skidding - tire traction limits available aerodynamic force
    • efficiency - drag limits apparent wind angle (beta) which caps

Empirical Data -Limited

    • Annual NALSA speed trials - historical yacht speeds & yacht speed/wind speed ratio
    • SDSU wind tunnel test - rear wheels alone account for 30% to 40% of total aerodynamic drag

Design Approach - Twin Wing Concept

    • Inclined wing, displaced from centerline, reduces effective moment arm
    • Aerodynamic downforce adds to traction w/o adding inertia
    • Structural load paths eliminate large bending moments in axle, body - lighter weight
    • Delta wheel fairings
    • Concept sketches:
      rear quarter
      front quarter
      right side

Twin Wing Rationale

    • Consider a single wing, set to windward & inclined to leeward
    • Projection of lift vector passes close to leeward wheel (Fig. 1)
    • Force vector could pass through contact patch, producing zero moment
    • Produces downward component
    • Reflecting wing for other tack produces two, mutual supporting wings in an A-frame
    • Pilot controls each wing separately to control rolling moments
    • Initial feasibility looks promising, but light wind performance is a problem.

Delta Wheel Fairings

    • Best landyachts today use simple flat plate over wheel hub - minimum "frontal" area
    • Must work at + 15 - 30 degrees beta; zero beta drag is relatively unimportant
    • Traditional fairings increase "frontal " area, do not consider separation due to beta
    • Fat delta provides streamlined shapes in streamwise cutting planes

Aerodynamic Issues

    • Fairing shaping for fully attached flow
    • Wing/fairing & Wing/Wing interference
    • Low Reynolds number performance
    • Span/chord length tradeoffs (induced drag vs Reynolds number)
    • Body shape
    • Overall configuration sizing and optimization

Aerodynamic Tools:

    • Eppler PROFIL: single element airfoil design
    • MCARFA: multiple element airfoil analysis
    • CMARC: 3D analysis

Tool Deficiencies:

    • Mesh generation - difficult to handle wing/fairing geometry
    • Multiple element airfoil design
    • Inability to handle laminar separation bubbles or modest trailing edge separation

Progress to Date:

    • 2D airfoil design
    • Parametric study of 2 wings
    • Representative fairings & wing intersections modeled