{ "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": "h-tail-twin-tail", "name": "H-tail / twin fin tail", "kind": "standard", "category": "Aircraft design", "group": "Tail configurations", "year": null, "question": "What is an H-tail (twin tail) and why use one?", "tags": [ "vehicle design", "tail configurations", "rc design", "aerodynamics" ], "aliases": [ "h-tail", "h tail aircraft", "twin tail", "twin fin", "twin vertical stabilizer", "double tail plane", "h-tail bomber", "twin rudder rc plane", "endplate fins stabilizer" ], "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/h-tail-twin-tail/", "sheet_txt": "https://xemstudio.com/objects/h-tail-twin-tail/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": [ "An H-tail puts two fins at the ends of the horizontal stabiliser. Bhattacharya et al. list redundancy and fins less affected by wing/fuselage downwash and fuselage turbulence as benefits, with propwash drag and boom weight as costs.", "The stabiliser end-plates the fins in the same way a T-tail's stabiliser end-plates a single fin (Kitplanes T-Tails), and splitting the fin area keeps each fin short.", "Arnedo describes twin (H) tails as 'much less common' than conventional, cruciform and T-tails.", "Used on: Consolidated B-24, B-25 Mitchell, Avro Lancaster, Handley Page Halifax, Petlyakov Pe-2.", "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": [ [ "Fin area split", "total Sv shared by two fins (each 8,000 mm^2 in reference build)", "computed from Vv 0.04" ], [ "Reference build", "Sh 40,000 mm^2, two fins 100 x 80 mm", "computed" ] ] } }, "sheet_text": "H-tail / twin fin tail — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/h-tail-twin-tail/ (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- An H-tail puts two fins at the ends of the horizontal stabiliser. Bhattacharya et al. list redundancy and fins less affected by wing/fuselage downwash and fuselage turbulence as benefits, with propwash drag and boom weight as costs.\n- The stabiliser end-plates the fins in the same way a T-tail's stabiliser end-plates a single fin (Kitplanes T-Tails), and splitting the fin area keeps each fin short.\n- Arnedo describes twin (H) tails as 'much less common' than conventional, cruciform and T-tails.\n- Used on: Consolidated B-24, B-25 Mitchell, Avro Lancaster, Handley Page Halifax, Petlyakov Pe-2.\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\nFin area split total Sv shared by two fins (each 8,000 mm^2 in reference build) computed from Vv 0.04\nReference build Sh 40,000 mm^2, two fins 100 x 80 mm computed\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- engrXiv (Bhattacharya et al., ICMMM 2023): Design and Computational Analysis of Y-tail Configuration for Maritime UAV — web — Publisher's page; dimensions are facts — https://engrxiv.org/preprint/download/6582/10812/9153\n- LibreTexts (Arnedo, Fundamentals of Aerospace Engineering): 2.2.3 Empennage — web — Publisher's page; dimensions are facts — https://eng.libretexts.org/Bookshelves/Aerospace_Engineering/Fundamentals_of_Aerospace_Engineering_(Arnedo)/02%3A_Generalities/2.02%3A_Parts_of_the_aircraft/2.2.03%3A_Empennage\n- Kitplanes (B. Wainfan): Design Process: T-Tails (2022) — web — Publisher's page; dimensions are facts — https://www.kitplanes.com/design-process-t-tails/\n- HAW Hamburg (Aircraft Design and Systems Group): Empennage sizing: tail lever arm as % of fuselage length (thesis; Table 2.1 typical tail volume coefficients) — web — Publisher's page; dimensions are facts — https://www.fzt.haw-hamburg.de/pers/Scholz/arbeiten/TextMcDavid.pdf\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/h-tail-twin-tail/index.json\nAPI: https://xemstudio.com/api/geometry?object=h-tail-twin-tail\n", "sources": [ { "publisher": "engrXiv (Bhattacharya et al., ICMMM 2023)", "title": "Design and Computational Analysis of Y-tail Configuration for Maritime UAV", "url": "https://engrxiv.org/preprint/download/6582/10812/9153", "formats": [ "web" ], "license": "Publisher's page; dimensions are facts", "license_verified": true, "hosted": false }, { "publisher": "LibreTexts (Arnedo, Fundamentals of Aerospace Engineering)", "title": "2.2.3 Empennage", "url": "https://eng.libretexts.org/Bookshelves/Aerospace_Engineering/Fundamentals_of_Aerospace_Engineering_(Arnedo)/02%3A_Generalities/2.02%3A_Parts_of_the_aircraft/2.2.03%3A_Empennage", "formats": [ "web" ], "license": "Publisher's page; dimensions are facts", "license_verified": true, "hosted": false }, { "publisher": "Kitplanes (B. Wainfan)", "title": "Design Process: T-Tails (2022)", "url": "https://www.kitplanes.com/design-process-t-tails/", "formats": [ "web" ], "license": "Publisher's page; dimensions are facts", "license_verified": true, "hosted": false }, { "publisher": "HAW Hamburg (Aircraft Design and Systems Group)", "title": "Empennage sizing: tail lever arm as % of fuselage length (thesis; Table 2.1 typical tail volume coefficients)", "url": "https://www.fzt.haw-hamburg.de/pers/Scholz/arbeiten/TextMcDavid.pdf", "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": [ "tail-volume-coefficient", "tail-moment-arm", "conventional-tail", "t-tail", "cruciform-tail", "v-tail" ], "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 did WWII bombers use H-tails?", "a": "Twin fins give redundancy and sit outside fuselage turbulence (Bhattacharya et al.); examples include the B-24, B-25 and Lancaster." } ], "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": "h-tail-twin-tail-tail", "formats": [ "step", "stl" ], "price_usd": 0, "license": "Xem Studio Design License", "step": "https://xemstudio.com/files/hardware/h-tail-twin-tail/h-tail-twin-tail-tail.step", "stl": "https://xemstudio.com/files/hardware/h-tail-twin-tail/h-tail-twin-tail-tail.stl", "note": "h tail layout: horizontal span 400 × chord 100, vertical 100 × 80 mm on a 500 mm boom, NACA 0009 surfaces" } ], "markdown": "https://xemstudio.com/objects/h-tail-twin-tail/index.md" }