{
 "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": "displacement-hull",
 "name": "Displacement hull and hull speed",
 "kind": "standard",
 "category": "Boat design",
 "group": "Hull types",
 "year": null,
 "question": "What is hull speed and why can't displacement boats go faster?",
 "tags": [
  "vehicle design",
  "hull types",
  "rc design",
  "aerodynamics"
 ],
 "aliases": [
  "hull speed",
  "displacement hull",
  "hull speed formula",
  "1.34 sqrt lwl",
  "speed length ratio",
  "waterline length speed",
  "displacement speed",
  "rc sailboat hull speed",
  "maximum hull speed"
 ],
 "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/displacement-hull/",
 "sheet_txt": "https://xemstudio.com/objects/displacement-hull/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 displacement hull is supported by buoyancy. Its bow wave lengthens with speed, and when the wave length equals the waterline length the boat is trapped climbing its own wave, so speed is limited by length (Good Old Boat).",
   "Hull speed in knots is 1.34 x sqrt(waterline in feet); some designers use 1.4. Doubling length does not double speed.",
   "Used on: Most large monohull sailboats (Good Old Boat).",
   "The file is a reference example built by Xem Studio from the numbers above (Length = IOM hull length 1000 mm (onemetre.net); beam and deadrise illustrative.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle."
  ],
  "table": {
   "columns": [
    "parameter",
    "value or range",
    "source"
   ],
   "rows": [
    [
     "Hull speed",
     "S (kn) = 1.34 x sqrt(LWL ft)",
     "Good Old Boat"
    ],
    [
     "Alternative constant",
     "1.4",
     "Good Old Boat"
    ],
    [
     "20 ft LWL",
     "~6.0 kn",
     "Good Old Boat"
    ],
    [
     "40 ft LWL",
     "~8.5 kn",
     "Good Old Boat"
    ],
    [
     "IOM RC yacht hull length",
     "1000 mm",
     "onemetre.net"
    ]
   ]
  }
 },
 "sheet_text": "Displacement hull and hull speed — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/displacement-hull/  (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 displacement hull is supported by buoyancy. Its bow wave lengthens with speed, and when the wave length equals the waterline length the boat is trapped climbing its own wave, so speed is limited by length (Good Old Boat).\n- Hull speed in knots is 1.34 x sqrt(waterline in feet); some designers use 1.4. Doubling length does not double speed.\n- Used on: Most large monohull sailboats (Good Old Boat).\n- The file is a reference example built by Xem Studio from the numbers above (Length = IOM hull length 1000 mm (onemetre.net); beam and deadrise illustrative.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.\n\nparameter  value or range  source\nHull speed  S (kn) = 1.34 x sqrt(LWL ft)  Good Old Boat\nAlternative constant  1.4  Good Old Boat\n20 ft LWL  ~6.0 kn  Good Old Boat\n40 ft LWL  ~8.5 kn  Good Old Boat\nIOM RC yacht hull length  1000 mm  onemetre.net\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Good Old Boat: Displacement hull speed 101 — web — Publisher's page; dimensions are facts — https://goodoldboat.com/displacement-hull-speed-101/\n- onemetre.net: The IOM class — web — Publisher's page; dimensions are facts — https://onemetre.net/OtherTopics/IOMclass/IOM.htm\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/displacement-hull/index.json\nAPI: https://xemstudio.com/api/geometry?object=displacement-hull\n",
 "sources": [
  {
   "publisher": "Good Old Boat",
   "title": "Displacement hull speed 101",
   "url": "https://goodoldboat.com/displacement-hull-speed-101/",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "onemetre.net",
   "title": "The IOM class",
   "url": "https://onemetre.net/OtherTopics/IOMclass/IOM.htm",
   "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": [
  "deep-v-hull",
  "modified-v-hull",
  "flat-bottom-hull",
  "cathedral-tri-hull",
  "tunnel-hull-catamaran",
  "three-point-hydroplane"
 ],
 "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": "Hull speed of a 1 m RC yacht?",
   "a": "LWL ~3.28 ft gives 1.34 x 1.81 = ~2.4 kn (formula from Good Old Boat)."
  }
 ],
 "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": "displacement-hull-hull",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/displacement-hull/displacement-hull-hull.step",
   "stl": "https://xemstudio.com/files/hardware/displacement-hull/displacement-hull-hull.stl",
   "note": "displacement hull, 1000 × 181 mm, deadrise 0° (sections illustrative, scale to your boat)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/displacement-hull/index.md"
}