{ "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": "spade-rudder", "name": "Spade rudder", "kind": "standard", "category": "Boat design", "group": "Sailboat appendages", "year": null, "question": "What is a spade rudder and why do racing boats use it?", "tags": [ "vehicle design", "sailboat appendages", "rc design", "aerodynamics" ], "aliases": [ "spade rudder", "balanced rudder", "rudder balance", "rc yacht rudder", "spade vs skeg rudder", "rudder foil", "NACA 0012 rudder", "rudder area", "rudder stall" ], "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/spade-rudder/", "sheet_txt": "https://xemstudio.com/objects/spade-rudder/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 spade rudder hangs free of the keel with no skeg, so it acts as a pure foil and can be balanced with area ahead of the stock (Good Old Boat). Its stock must resist bending as well as twisting.", "Balance cuts helm load but too much makes steering hard to control: old practice capped it near 10%, modern rudders reach 17% (Good Old Boat, quoting designers).", "Spades run fat, round leading edges to resist stall; typical thickness 10-12% (Stewart).", "The file is a reference example built by Xem Studio from the numbers above (NACA 0012 per Perry; size illustrative.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle." ], "table": { "columns": [ "parameter", "value or range", "source" ], "rows": [ [ "Balance area", "up to ~17%; ~15% on boats over 45 ft (Perry)", "Good Old Boat" ], [ "Max thickness position", "30% chord", "Good Old Boat" ], [ "Thickness ratio", "10-12% typical (Stewart); 10-18% (Wurmfeld)", "Good Old Boat" ], [ "Favoured foil", "NACA 0012 (Perry)", "Good Old Boat" ], [ "Rudder area", "~1.4% of sail area (Tanton)", "Good Old Boat" ], [ "Max rudder angle", "35-40 deg", "Good Old Boat" ] ] } }, "sheet_text": "Spade rudder — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/spade-rudder/ (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 spade rudder hangs free of the keel with no skeg, so it acts as a pure foil and can be balanced with area ahead of the stock (Good Old Boat). Its stock must resist bending as well as twisting.\n- Balance cuts helm load but too much makes steering hard to control: old practice capped it near 10%, modern rudders reach 17% (Good Old Boat, quoting designers).\n- Spades run fat, round leading edges to resist stall; typical thickness 10-12% (Stewart).\n- The file is a reference example built by Xem Studio from the numbers above (NACA 0012 per Perry; size illustrative.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.\n\nparameter value or range source\nBalance area up to ~17%; ~15% on boats over 45 ft (Perry) Good Old Boat\nMax thickness position 30% chord Good Old Boat\nThickness ratio 10-12% typical (Stewart); 10-18% (Wurmfeld) Good Old Boat\nFavoured foil NACA 0012 (Perry) Good Old Boat\nRudder area ~1.4% of sail area (Tanton) Good Old Boat\nMax rudder angle 35-40 deg Good Old Boat\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Good Old Boat: The rudiments of rudders — web — Publisher's page; dimensions are facts — https://goodoldboat.com/the-rudiments-of-rudders/\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/spade-rudder/index.json\nAPI: https://xemstudio.com/api/geometry?object=spade-rudder\n", "sources": [ { "publisher": "Good Old Boat", "title": "The rudiments of rudders", "url": "https://goodoldboat.com/the-rudiments-of-rudders/", "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": [ "fin-keel-bulb", "skeg-hung-rudder", "daggerboard", "centreboard", "canting-keel", "wing-sail" ], "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 much balance?", "a": "Around 15%, rarely above 17% (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": "spade-rudder-appendage", "formats": [ "step", "stl" ], "price_usd": 0, "license": "Xem Studio Design License", "step": "https://xemstudio.com/files/hardware/spade-rudder/spade-rudder-appendage.step", "stl": "https://xemstudio.com/files/hardware/spade-rudder/spade-rudder-appendage.stl", "note": "rudder spade: 300 mm deep, 60 mm chord, NACA 00-series foil" } ], "markdown": "https://xemstudio.com/objects/spade-rudder/index.md" }