{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "rear-wing-dual-element",
 "name": "Dual-element (two-element) rear wing",
 "kind": "standard",
 "category": "Car design",
 "group": "Car aero",
 "year": null,
 "question": "What is a dual-element wing and why does it make more downforce?",
 "tags": [
  "vehicle design",
  "car aero",
  "rc design",
  "aerodynamics"
 ],
 "aliases": [
  "dual element wing",
  "two element wing",
  "double element wing",
  "main plane and flap",
  "slotted wing car",
  "wing gap overlap",
  "multi element rear wing",
  "flap gap race car wing",
  "biplane wing car",
  "2 element GT wing",
  "high downforce wing"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/rear-wing-dual-element/",
 "sheet_txt": "https://xemstudio.com/objects/rear-wing-dual-element/sheet.txt",
 "sheet": {
  "basis": "Design rules and figures from the cited sources; example geometry by Xem Studio",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "A dual-element wing adds a flap behind the main plane, separated by a small slot. The slot lets fresh air energise the flap's suction side so the pair can run far more camber before stalling than one element could.",
   "In Southampton's ground-effect tests the optimum slot was a 3.2% chord gap with 2.4% chord overlap, and the wing reached CL 3.03 (Zhang & Zerihan). In UIUC open-wheel front-wing tests, raising flap angle from 14 to 24 deg lifted CL from 1.95 to 2.37 (Jasinski & Selig).",
   "HP Academy pairs dual-element rear wings with 500-600 hp cars and larger splitters, i.e. more downforce means more drag and needs front balance to match.",
   "Used on: Champ Car and F1 front-wing configurations tested at UIUC.",
   "The file is a reference example built by Xem Studio from the numbers above (Geometry of the Zhang & Zerihan test wing; aoa is its 1 deg reference incidence.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle."
  ],
  "table": {
   "columns": [
    "parameter",
    "value or range",
    "source"
   ],
   "rows": [
    [
     "Main element chord",
     "223.4 mm (~0.59c)",
     "Zhang & Zerihan"
    ],
    [
     "Flap chord",
     "165.7 mm (~0.44c)",
     "Zhang & Zerihan"
    ],
    [
     "Reference (combined) chord / span",
     "380 mm / 1100 mm, AR 2.89",
     "Zhang & Zerihan"
    ],
    [
     "Optimum gap",
     "0.032c (12 mm)",
     "Zhang & Zerihan"
    ],
    [
     "Optimum overlap",
     "0.024c (9 mm)",
     "Zhang & Zerihan"
    ],
    [
     "Max CL, high flap angle",
     "3.028 at h/c 0.079",
     "Zhang & Zerihan"
    ],
    [
     "Flap deflection range tested",
     "4-44 deg (3D), 6-41 deg (2D)",
     "Jasinski & Selig (UIUC)"
    ],
    [
     "CL at alpha 6 deg",
     "1.95 (flap 14 deg), 2.37 (flap 24 deg)",
     "Jasinski & Selig (UIUC)"
    ],
    [
     "Swan-neck LMP wing, flap +8 deg",
     "1413 lb downforce",
     "Mulsanne's Corner"
    ]
   ]
  }
 },
 "sheet_text": "Dual-element (two-element) rear wing — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/rear-wing-dual-element/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)\nBasis: Design rules and figures from the cited sources; example geometry by Xem Studio\nCatalog version: 2026-10-20\n\nSizes: see table below\n- A dual-element wing adds a flap behind the main plane, separated by a small slot. The slot lets fresh air energise the flap's suction side so the pair can run far more camber before stalling than one element could.\n- In Southampton's ground-effect tests the optimum slot was a 3.2% chord gap with 2.4% chord overlap, and the wing reached CL 3.03 (Zhang & Zerihan). In UIUC open-wheel front-wing tests, raising flap angle from 14 to 24 deg lifted CL from 1.95 to 2.37 (Jasinski & Selig).\n- HP Academy pairs dual-element rear wings with 500-600 hp cars and larger splitters, i.e. more downforce means more drag and needs front balance to match.\n- Used on: Champ Car and F1 front-wing configurations tested at UIUC.\n- The file is a reference example built by Xem Studio from the numbers above (Geometry of the Zhang & Zerihan test wing; aoa is its 1 deg reference incidence.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.\n\nparameter  value or range  source\nMain element chord  223.4 mm (~0.59c)  Zhang & Zerihan\nFlap chord  165.7 mm (~0.44c)  Zhang & Zerihan\nReference (combined) chord / span  380 mm / 1100 mm, AR 2.89  Zhang & Zerihan\nOptimum gap  0.032c (12 mm)  Zhang & Zerihan\nOptimum overlap  0.024c (9 mm)  Zhang & Zerihan\nMax CL, high flap angle  3.028 at h/c 0.079  Zhang & Zerihan\nFlap deflection range tested  4-44 deg (3D), 6-41 deg (2D)  Jasinski & Selig (UIUC)\nCL at alpha 6 deg  1.95 (flap 14 deg), 2.37 (flap 24 deg)  Jasinski & Selig (UIUC)\nSwan-neck LMP wing, flap +8 deg  1413 lb downforce  Mulsanne's Corner\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- University of Southampton / AIAA Journal: Aerodynamics of a Double-Element Wing in Ground Effect (Zhang & Zerihan, AIAA J. 41(6), 2003) — web — Publisher's page; dimensions are facts — https://eprints.soton.ac.uk/22605/1/AIAA-2057-653.pdf\n- University of Illinois / SAE: Experimental Study of Open-Wheel Race-Car Front Wings (Jasinski & Selig, SAE 1998) — web — Publisher's page; dimensions are facts — https://m-selig.web.engr.illinois.edu/pubs/JasinskiSelig-1998-MSEC-SAE-Trans-V107-S6.pdf\n- High Performance Academy: Aerodynamic performance devices for club level cars: front splitters — web — Publisher's page; dimensions are facts — https://www.hpacademy.com/courses/aerodynamics-fundamentals/aerodynamic-performance-devices-for-club-level-cars-front-splitters\n- Mulsanne's Corner: The Rise of the Swan Neck (2009 LMP rear wing CFD study) — web — Publisher's page; dimensions are facts — https://www.mulsannescorner.com/rearwingLMPCFD2009.html\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/rear-wing-dual-element/index.json\nAPI: https://xemstudio.com/api/geometry?object=rear-wing-dual-element\n",
 "sources": [
  {
   "publisher": "University of Southampton / AIAA Journal",
   "title": "Aerodynamics of a Double-Element Wing in Ground Effect (Zhang & Zerihan, AIAA J. 41(6), 2003)",
   "url": "https://eprints.soton.ac.uk/22605/1/AIAA-2057-653.pdf",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "University of Illinois / SAE",
   "title": "Experimental Study of Open-Wheel Race-Car Front Wings (Jasinski & Selig, SAE 1998)",
   "url": "https://m-selig.web.engr.illinois.edu/pubs/JasinskiSelig-1998-MSEC-SAE-Trans-V107-S6.pdf",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "High Performance Academy",
   "title": "Aerodynamic performance devices for club level cars: front splitters",
   "url": "https://www.hpacademy.com/courses/aerodynamics-fundamentals/aerodynamic-performance-devices-for-club-level-cars-front-splitters",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Mulsanne's Corner",
   "title": "The Rise of the Swan Neck (2009 LMP rear wing CFD study)",
   "url": "https://www.mulsannescorner.com/rearwingLMPCFD2009.html",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "rear-wing-single-element",
  "swan-neck-wing-mount",
  "gurney-flap-wickerbill",
  "wing-endplates",
  "front-splitter",
  "splitter-tunnels-front-diffuser"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [],
 "faq": [
  {
   "q": "What gap should a two-element wing use?",
   "a": "The Southampton ground-effect test found 0.032c gap and 0.024c overlap optimal for its geometry (Zhang & Zerihan). Treat that as a starting point and test."
  }
 ],
 "files_license": {
  "name": "Xem Studio Design License",
  "holder": "Xem Studio",
  "url": "https://xemstudio.com/license/",
  "note": "Xem Studio's own design: free to use, print, modify and sell things made from it; not to be republished or redistributed as files."
 },
 "offers": [
  {
   "file": "rear-wing-dual-element-rear-wing",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/rear-wing-dual-element/rear-wing-dual-element-rear-wing.step",
   "stl": "https://xemstudio.com/files/hardware/rear-wing-dual-element/rear-wing-dual-element-rear-wing.stl",
   "note": "dual element rear wing: span 1100 × chord 380 mm at 1°, endplates 200 mm, inverted NACA 4412 section (mounts from below)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/rear-wing-dual-element/index.md"
}