{
 "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": "stepped-hull",
 "name": "Stepped hull",
 "kind": "standard",
 "category": "Boat design",
 "group": "Hull types",
 "year": null,
 "question": "How does a stepped hull make a boat faster?",
 "tags": [
  "vehicle design",
  "hull types",
  "rc design",
  "aerodynamics"
 ],
 "aliases": [
  "stepped hull",
  "step hull",
  "ventilated step",
  "stepped bottom boat",
  "rc stepped hull",
  "hull steps",
  "two step hull",
  "stepped vee",
  "stepped 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/stepped-hull/",
 "sheet_txt": "https://xemstudio.com/objects/stepped-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": [
   "Steps break the planing bottom into several high-pressure leading edges, reducing wetted area and friction drag. Each step must be ventilated, or the step face stays wet and drag rises (BoatTest).",
   "Steps can add roughly 8-12% performance but are not worthwhile at low planing speeds, about 35 knots for a 30 ft boat. Poor designs can hook in turns (BoatTest).",
   "Twin steps tolerate CG variation better than a single step (BoatTest).",
   "Used on: White Iveco (Fabio Buzzi, 1984).",
   "The file is a reference example built by Xem Studio from the numbers above (Reference RC mono: 585 mm length and 20 deg transom deadrise (SV Design Stealthwake data); 181 mm is an unlabelled width in the same source's deadrise diagram.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle."
  ],
  "table": {
   "columns": [
    "parameter",
    "value or range",
    "source"
   ],
   "rows": [
    [
     "Performance gain",
     "roughly 8-12%",
     "BoatTest"
    ],
    [
     "Worthwhile above (30 ft boat)",
     "about 35 knots",
     "BoatTest"
    ],
    [
     "Early hydro step",
     "75 mm step, 2/3 aft",
     "Wikipedia (Hydroplane)"
    ]
   ]
  }
 },
 "sheet_text": "Stepped hull — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/stepped-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- Steps break the planing bottom into several high-pressure leading edges, reducing wetted area and friction drag. Each step must be ventilated, or the step face stays wet and drag rises (BoatTest).\n- Steps can add roughly 8-12% performance but are not worthwhile at low planing speeds, about 35 knots for a 30 ft boat. Poor designs can hook in turns (BoatTest).\n- Twin steps tolerate CG variation better than a single step (BoatTest).\n- Used on: White Iveco (Fabio Buzzi, 1984).\n- The file is a reference example built by Xem Studio from the numbers above (Reference RC mono: 585 mm length and 20 deg transom deadrise (SV Design Stealthwake data); 181 mm is an unlabelled width in the same source's deadrise diagram.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.\n\nparameter  value or range  source\nPerformance gain  roughly 8-12%  BoatTest\nWorthwhile above (30 ft boat)  about 35 knots  BoatTest\nEarly hydro step  75 mm step, 2/3 aft  Wikipedia (Hydroplane)\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- BoatTest: Watch your step (stepped hulls) — web — Publisher's page; dimensions are facts — https://boattest.com/article/watch-your-step\n- Wikipedia: Hydroplane (boat) — web — Publisher's page; dimensions are facts — https://en.wikipedia.org/wiki/Hydroplane_(boat)\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/stepped-hull/index.json\nAPI: https://xemstudio.com/api/geometry?object=stepped-hull\n",
 "sources": [
  {
   "publisher": "BoatTest",
   "title": "Watch your step (stepped hulls)",
   "url": "https://boattest.com/article/watch-your-step",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Hydroplane (boat)",
   "url": "https://en.wikipedia.org/wiki/Hydroplane_(boat)",
   "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": "Why must steps breathe?",
   "a": "Without air the step face creates suction and drag rises sharply (BoatTest)."
  }
 ],
 "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": "stepped-hull-hull",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/stepped-hull/stepped-hull-hull.step",
   "stl": "https://xemstudio.com/files/hardware/stepped-hull/stepped-hull-hull.stl",
   "note": "stepped hull, 585 × 181 mm, deadrise 22°, 2 steps (sections illustrative, scale to your boat)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/stepped-hull/index.md"
}