{
 "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": "turn-fins",
 "name": "Turn fins (RC boats)",
 "kind": "standard",
 "category": "Boat design",
 "group": "Hull types",
 "year": null,
 "question": "What are turn fins on RC boats for?",
 "tags": [
  "vehicle design",
  "hull types",
  "rc design",
  "aerodynamics",
  "guide"
 ],
 "aliases": [
  "turn fin",
  "rc boat turn fins",
  "sponson turn fin",
  "hydro turn fin",
  "turn fin angle",
  "mono turn fin",
  "rc boat fins",
  "turning fin"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "not-scanned",
 "les": false,
 "free_files": 0,
 "url": "https://xemstudio.com/objects/turn-fins/",
 "sheet_txt": "https://xemstudio.com/objects/turn-fins/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": [
   "Turn fins are small vertical blades near the chine that give the hull grip in turns. On a deep-V mono a racer places a right-turn fin as close to the chine line as possible at 90 deg to the V surface (Model Gas Boats forum).",
   "On hydros, forward tilt makes the boat track left and lifts the starboard sponson; backward tilt does the opposite (Model Gas Boats)."
  ],
  "table": {
   "columns": [
    "parameter",
    "value or range",
    "source"
   ],
   "rows": [
    [
     "Mono fin placement",
     "near chine, 90 deg to V surface",
     "Model Gas Boats forum"
    ],
    [
     "Hydro fin forward tilt",
     "tracks left, lifts starboard sponson",
     "Model Gas Boats"
    ]
   ]
  }
 },
 "sheet_text": "Turn fins (RC boats) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/turn-fins/  (sheet CC BY 4.0)\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- Turn fins are small vertical blades near the chine that give the hull grip in turns. On a deep-V mono a racer places a right-turn fin as close to the chine line as possible at 90 deg to the V surface (Model Gas Boats forum).\n- On hydros, forward tilt makes the boat track left and lifts the starboard sponson; backward tilt does the opposite (Model Gas Boats).\n\nparameter  value or range  source\nMono fin placement  near chine, 90 deg to V surface  Model Gas Boats forum\nHydro fin forward tilt  tracks left, lifts starboard sponson  Model Gas Boats\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Model Gas Boats forum: Need help setting up a mono for the first time — web — Publisher's page; dimensions are facts — https://www.modelgasboats.com/forum/13-ask-the-editors-discuss-articles-general-boat-questions/21138-need-help-setting-up-a-mono-for-the-first-time\n- Model Gas Boats: Some tips on setting up a hydroplane hull — web — Publisher's page; dimensions are facts — https://modelgasboats.com/magazine/tech-articles-mainmenu-608/369-hydro-setup-tips\n\nNo true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.\nAPI: https://xemstudio.com/api/geometry?object=turn-fins\n",
 "sources": [
  {
   "publisher": "Model Gas Boats forum",
   "title": "Need help setting up a mono for the first time",
   "url": "https://www.modelgasboats.com/forum/13-ask-the-editors-discuss-articles-general-boat-questions/21138-need-help-setting-up-a-mono-for-the-first-time",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Model Gas Boats",
   "title": "Some tips on setting up a hydroplane hull",
   "url": "https://modelgasboats.com/magazine/tech-articles-mainmenu-608/369-hydro-setup-tips",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "not-scanned",
  "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": "Curved or straight?",
   "a": "Straight fins mainly affect tracking; curved fins affect turn tightness (Model Gas Boats)."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/turn-fins/index.md"
}