{
 "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": "ground-effect-height-chord-ratio",
 "name": "Ground effect: height/chord ratio (ram / chord-dominated regime)",
 "kind": "standard",
 "category": "Aircraft design",
 "group": "Ground-effect design",
 "year": null,
 "question": "What height-to-chord ratio do WIG craft fly at?",
 "tags": [
  "vehicle design",
  "ground-effect design",
  "rc design",
  "aerodynamics"
 ],
 "aliases": [
  "ground effect height chord ratio",
  "h/c ratio wig",
  "extreme ground effect",
  "ram effect wing",
  "chord dominated ground effect",
  "wig cruise height",
  "ekranoplan flight height",
  "ground effect lift to drag",
  "wig l/d"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
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 "xem_status": "free-files",
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 "url": "https://xemstudio.com/objects/ground-effect-height-chord-ratio/",
 "sheet_txt": "https://xemstudio.com/objects/ground-effect-height-chord-ratio/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": [
   "Rozhdestvensky defines extreme ground effect as clearances of 10% of the main wing chord or less, distinguishing chord-dominated ground effect (flow stagnation under the wing) from span-dominated (induced-drag reduction).",
   "Moore et al. split ram effect (h/c <= 10%) from normal ground effect, and a review concludes rectangular wings are most effective within 15% of chord (Frontiers 2022 review).",
   "An isolated AR 2-3 wing at about 20% chord clearance reaches L/D of roughly 35-45, but hull, pylons and tail cut that by about 65% to 12-16 for a whole craft (Rozhdestvensky, citing Kirillovykh).",
   "The file is a reference example built by Xem Studio from the numbers above. Sizes the sources do not fix are illustrative; scale the example to your own vehicle."
  ],
  "table": {
   "columns": [
    "parameter",
    "value or range",
    "source"
   ],
   "rows": [
    [
     "Extreme ground effect",
     "h <= 10% chord",
     "Rozhdestvensky 2006"
    ],
    [
     "Ram effect regime",
     "h/c <= 10%",
     "Frontiers 2022 (Moore et al.)"
    ],
    [
     "Most effective (rectangular wings)",
     "within 15% chord",
     "Frontiers 2022"
    ],
    [
     "Isolated wing L/D, AR 2-3 at 20% c",
     "35-45",
     "Rozhdestvensky (Kirillovykh)"
    ],
    [
     "Whole-vehicle L/D after integration",
     "12-16 (losses: hull ~40%, pylons ~15%, tail ~5%)",
     "Rozhdestvensky"
    ],
    [
     "Proposed GE-zone definition",
     "height where lift is ~30% above free-flight value",
     "Rozhdestvensky"
    ],
    [
     "Reference build",
     "span 600, chord 300",
     "computed (AR 2)"
    ]
   ]
  }
 },
 "sheet_text": "Ground effect: height/chord ratio (ram / chord-dominated regime) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/ground-effect-height-chord-ratio/  (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- Rozhdestvensky defines extreme ground effect as clearances of 10% of the main wing chord or less, distinguishing chord-dominated ground effect (flow stagnation under the wing) from span-dominated (induced-drag reduction).\n- Moore et al. split ram effect (h/c <= 10%) from normal ground effect, and a review concludes rectangular wings are most effective within 15% of chord (Frontiers 2022 review).\n- An isolated AR 2-3 wing at about 20% chord clearance reaches L/D of roughly 35-45, but hull, pylons and tail cut that by about 65% to 12-16 for a whole craft (Rozhdestvensky, citing Kirillovykh).\n- The file is a reference example built by Xem Studio from the numbers above. Sizes the sources do not fix are illustrative; scale the example to your own vehicle.\n\nparameter  value or range  source\nExtreme ground effect  h <= 10% chord  Rozhdestvensky 2006\nRam effect regime  h/c <= 10%  Frontiers 2022 (Moore et al.)\nMost effective (rectangular wings)  within 15% chord  Frontiers 2022\nIsolated wing L/D, AR 2-3 at 20% c  35-45  Rozhdestvensky (Kirillovykh)\nWhole-vehicle L/D after integration  12-16 (losses: hull ~40%, pylons ~15%, tail ~5%)  Rozhdestvensky\nProposed GE-zone definition  height where lift is ~30% above free-flight value  Rozhdestvensky\nReference build  span 600, chord 300  computed (AR 2)\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Progress in Aerospace Sciences (K.V. Rozhdestvensky, 2006): Wing-in-ground effect vehicles (review) — web — Publisher's page; dimensions are facts — https://www.hassanhameed.com/wp-content/uploads/2016/01/wingingroundeffectvehicles-130120003005-phpapp01.pdf\n- Frontiers in Aerospace Engineering (2022): Review of ground-effect experiments on rectangular, reverse-delta and delta wings — web — Publisher's page; dimensions are facts — https://www.frontiersin.org/journals/aerospace-engineering/articles/10.3389/fpace.2022.975158/pdf\n- NASA Langley (Fink & Lastinger): Aerodynamic Characteristics of Low-Aspect-Ratio Wings in Close Proximity to the Ground, NASA TN D-926 (1961) — web — Publisher's page; dimensions are facts — https://ntrs.nasa.gov/api/citations/19980231058/downloads/19980231058.pdf\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/ground-effect-height-chord-ratio/index.json\nAPI: https://xemstudio.com/api/geometry?object=ground-effect-height-chord-ratio\n",
 "sources": [
  {
   "publisher": "Progress in Aerospace Sciences (K.V. Rozhdestvensky, 2006)",
   "title": "Wing-in-ground effect vehicles (review)",
   "url": "https://www.hassanhameed.com/wp-content/uploads/2016/01/wingingroundeffectvehicles-130120003005-phpapp01.pdf",
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    "web"
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   "publisher": "Frontiers in Aerospace Engineering (2022)",
   "title": "Review of ground-effect experiments on rectangular, reverse-delta and delta wings",
   "url": "https://www.frontiersin.org/journals/aerospace-engineering/articles/10.3389/fpace.2022.975158/pdf",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "NASA Langley (Fink & Lastinger)",
   "title": "Aerodynamic Characteristics of Low-Aspect-Ratio Wings in Close Proximity to the Ground, NASA TN D-926 (1961)",
   "url": "https://ntrs.nasa.gov/api/citations/19980231058/downloads/19980231058.pdf",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
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 "related": [
  "ground-effect-height-span-ratio",
  "lippisch-reverse-delta-wig",
  "ekranoplan-wing-tail-layout",
  "tandem-wig-configuration",
  "power-augmented-ram-par",
  "wig-endplates"
 ],
 "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": "How high should a WIG model fly?",
   "a": "Extreme ground effect is below 10% of chord; reviews put rectangular wings' sweet spot within 15% chord (Rozhdestvensky; Frontiers)."
  }
 ],
 "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": "ground-effect-height-chord-ratio-wing",
   "formats": [
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    "stl"
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   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/ground-effect-height-chord-ratio/ground-effect-height-chord-ratio-wing.step",
   "stl": "https://xemstudio.com/files/hardware/ground-effect-height-chord-ratio/ground-effect-height-chord-ratio-wing.stl",
   "note": "endplated wing: span 600, chord 300 mm, anhedral 0°, endplates 30 mm (scale to your craft)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/ground-effect-height-chord-ratio/index.md"
}