{"$schema":"nativecad-dfm-pack/1","id":"marine","title":"Marine — hulls, deck hardware, through-hulls, corrosion and outboard mounting","sector":"marine","version":"2026-09-03","summary":"Hull scantlings by ISO 12215-5, deck-hardware and cleat sizing, through-hull/seacock hole sizes and waterline rules, marine fastener and galvanic-isolation practice, drainage, outboard transom heights, and the ISO/ABYC/USCG tests and materials a small-craft part is held to.","aliases":["boat","hull","deck hardware","cleat","seacock","through-hull","transom","outboard","bilge","stanchion","yacht","dinghy","kayak"],"crossSector":false,"size":"core","sources":[{"id":"iso-12215-5","title":"ISO 12215-5:2019 Small craft — Hull construction and scantlings — Part 5: Design pressures for monohulls, design stresses, scantlings determination","url":"https://www.iso.org/standard/72178.html","accessed":"2026-09-03"},{"id":"abyc-h27","title":"ABYC H-27 Seacocks, Thru-Hull Connections, and Drain Plugs","url":"https://abycinc.org/page/StandardsCatalog","accessed":"2026-09-03"},{"id":"abyc-h40","title":"ABYC H-40 Anchoring, Mooring and Strong Point Design and Installation","url":"https://abycinc.org/page/StandardsCatalog","accessed":"2026-09-03"},{"id":"abyc-e2","title":"ABYC E-2 Cathodic Protection","url":"https://abycinc.org/page/StandardsCatalog","accessed":"2026-09-03"},{"id":"iso-9093","title":"ISO 9093:2020 Small craft — Seacocks and through-hull fittings","url":"https://www.iso.org/standard/71651.html","accessed":"2026-09-03"},{"id":"iso-15083","title":"ISO 15083:2019 Small craft — Bilge-pumping systems","url":"https://www.iso.org/standard/71218.html","accessed":"2026-09-03"},{"id":"uscg-33cfr183","title":"33 CFR Part 183 — Boats and Associated Equipment (US Coast Guard)","url":"https://www.ecfr.gov/current/title-33/chapter-I/subchapter-S/part-183","accessed":"2026-09-03"},{"id":"gerr-boat-strength","title":"Dave Gerr, The Elements of Boat Strength (International Marine/McGraw-Hill, 2000)","note":"Reference text for scantling rules of thumb, stringer spacing, and galvanic series practice","accessed":"2026-09-03"},{"id":"outboard-shaft-length-guide","title":"BoatUS / outboard-industry transom-height and shaft-length convention (short/long/XL shaft)","url":"https://www.boatus.org/","accessed":"2026-09-03"},{"id":"astm-b98","title":"ASTM B98/B98M Standard Specification for Copper-Silicon Alloy Rod, Bar and Shapes for General Purposes (silicon bronze)","url":"https://www.astm.org/b0098_b0098m-19.html","accessed":"2026-09-03"},{"id":"astm-a276","title":"ASTM A276/A276M Standard Specification for Stainless Steel Bars and Shapes (Type 316)","url":"https://www.astm.org/a0276_a0276m-17.html","accessed":"2026-09-03"}],"entries":[{"id":"iso-12215-design-categories","kind":"standard","tier":1,"title":"ISO 12215-5 design categories A-D and their design pressures","summary":"ISO 12215-5 scantlings scale with design category: A (ocean, wind >40kn, wave >4m), B (offshore, ≤40kn/4m), C (inshore, ≤27kn/2m), D (sheltered, ≤18kn/0.5m) — the same hull dropped from category A to D can shed 30-50% of its bottom-panel thickness.","applies":["hull","scantlings"],"value":{"options":["A","B","C","D"]},"basis":"ISO 12215-5 Table 1 design category definitions drive every downstream design-pressure formula","sources":["iso-12215-5"],"tags":["iso12215","design-category","scantlings"]},{"id":"grp-single-skin-bottom-thickness","kind":"dimension","tier":1,"title":"Single-skin GRP bottom laminate thickness by LOA","summary":"A single-skin E-glass/polyester GRP bottom panel runs about 6 mm on a 6 m boat up to 12 mm on a 12 m boat (design category B/C planing hull), roughly linear with LOA — always confirm against an ISO 12215-5 panel calculation, this is a starting estimate only.","applies":["hull","grp","fiberglass hull"],"value":{"min":6,"max":12,"unit":"mm"},"basis":"ISO 12215-5 design-pressure and panel-size scaling for single-skin bottom laminates, category B/C","sources":["iso-12215-5"],"tags":["hull","grp","thickness","bottom"]},{"id":"cored-deck-panel-skins","kind":"dimension","tier":1,"title":"Cored deck panel: skin and core thickness","summary":"A cored deck panel typically pairs two 2-3 mm GRP skins with a 12-25 mm core (balsa, Coosa or foam); thin skins carry the in-plane/bending load while the core sets panel stiffness — going below 2 mm skin risks print-through and puncture.","applies":["deck","cored panel","sandwich construction"],"value":{"table":[{"param":"skin","min":2,"max":3},{"param":"core","min":12,"max":25}],"unit":"mm"},"basis":"ISO 12215-5 sandwich-panel scantling method: skin thickness from in-plane stress, core thickness from panel deflection/shear","sources":["iso-12215-5"],"tags":["deck","cored","sandwich","skin","core"]},{"id":"hull-stringer-spacing","kind":"dimension","tier":1,"title":"Hull bottom stringer/frame spacing","summary":"Longitudinal stringers or transverse frames under a GRP or aluminium hull bottom panel space 300-450 mm apart on a typical 6-12 m planing hull — closer spacing lets the panel scantling (and hence its thickness) shrink, the usual trade-off against added stringer weight.","applies":["hull","stringer","frame"],"value":{"min":300,"max":450,"unit":"mm"},"basis":"ISO 12215-5 panel unsupported-span input; Gerr's scantling rules of thumb for stringer spacing on planing hulls","sources":["iso-12215-5","gerr-boat-strength"],"tags":["hull","stringer","spacing","frame"]},{"id":"cleat-size-by-loa","kind":"dimension","tier":1,"title":"Horn-cleat length by boat LOA","summary":"Cleat size scales with boat length in a standard series: 150 mm (6 in) for dinghies/small runabouts, 200 mm (8 in) around 6-8 m, 250 mm (10 in) around 8-11 m, and 300 mm (12 in) for boats over ~11 m — undersizing a cleat concentrates line load onto a short horn and bends it.","applies":["cleat","horn cleat","deck hardware"],"value":{"options":[150,200,250,300],"unit":"mm"},"basis":"Common marine-hardware cleat sizing series matched to boat LOA and expected line diameter","sources":["abyc-h40"],"tags":["cleat","size","deck-hardware"]},{"id":"cleat-backing-plate-thickness","kind":"rule","tier":1,"title":"Cleat/stanchion backing plate minimum thickness","summary":"Every through-bolted cleat or stanchion base needs a backing plate of ≥ 6 mm 316 stainless (or aluminium) or ≥ 12 mm G10/FR4 laminate, spreading bolt load over enough deck-core area that a hard pull doesn't crush the core or pull the bolt through.","applies":["cleat","stanchion","backing plate","deck hardware"],"value":{"table":[{"material":"316 stainless / aluminium","min":6},{"material":"G10/FR4","min":12}],"unit":"mm"},"basis":"ABYC H-40 strong-point load-spreading requirement for deck hardware backing plates","sources":["abyc-h40"],"tags":["backing-plate","cleat","stanchion"]},{"id":"stanchion-dimensions","kind":"dimension","tier":1,"title":"Lifeline stanchion diameter and height","summary":"A lifeline stanchion tube is 25 mm (1 in) outside diameter in 316 stainless, 600-750 mm tall above the deck so the top lifeline sits around waist height; taller/thinner stanchions need a wall-thickness or diameter increase per ABYC H-40 load rules.","applies":["stanchion","lifeline","deck hardware"],"value":{"table":[{"param":"diameter","value":25},{"param":"height","min":600,"max":750}],"unit":"mm"},"basis":"Common 316-stainless stanchion tube stock size and ABYC H-40 lifeline height guidance","sources":["abyc-h40"],"tags":["stanchion","lifeline","diameter","height"]},{"id":"through-hull-nps-sizes","kind":"dimension","tier":1,"title":"Through-hull/seacock pipe sizes (NPS)","summary":"Through-hull fittings and seacocks are sized on the NPS (nominal pipe size) series 1/2, 3/4, 1, 1-1/4, 1-1/2 and 2 in — a bilge pump discharge is typically 3/4-1 in, a raw-water intake for a small inboard 3/4-1-1/4 in, and a cockpit drain up to 1-1/2-2 in.","applies":["through-hull","seacock","plumbing"],"value":{"options":[0.5,0.75,1,1.25,1.5,2],"unit":"in"},"basis":"ISO 9093 / ABYC H-27 seacock and through-hull nominal pipe size series","sources":["iso-9093","abyc-h27"],"tags":["through-hull","seacock","nps","pipe-size"]},{"id":"through-hull-hole-diameters","kind":"dimension","tier":1,"title":"Through-hull hull-penetration hole diameters","summary":"Drill the hull penetration to match the fitting's tailpipe OD, not the NPS nominal bore: common through-hull hole sizes are ⌀22, 29, 35, 48 and 60 mm for the 1/2 through 2 in NPS series — undersizing binds the tailpipe, oversizing starves the flange's bedding-compound seal area.","applies":["through-hull","seacock","hull penetration"],"value":{"options":[22,29,35,48,60],"unit":"mm"},"basis":"Typical bronze/Marelon through-hull tailpipe OD by NPS size","sources":["iso-9093"],"tags":["through-hull","hole","diameter"]},{"id":"seacock-waterline-rule","kind":"rule","tier":1,"title":"Through-hull placement above/below the waterline","summary":"Every through-hull below the waterline, or within 300 mm above it at maximum heel, needs a seacock with a positive shutoff bolted to the hull (ISO 9093 / ABYC H-27: 3 bolts on ⌀ ≥ 25 mm fittings); higher drains that can never submerge may skip it.","applies":["through-hull","seacock","hull penetration"],"basis":"ABYC H-27 requires a seacock on every through-hull that can be submerged in normal operation or at the boat's maximum heel angle","sources":["abyc-h27"],"tags":["seacock","waterline","through-hull","rule"]},{"id":"marine-fastener-alloys","kind":"fastener","tier":1,"title":"Marine fastener alloys: 316 stainless and silicon bronze","summary":"Above-waterline and general deck-hardware fasteners are 316 (A4) stainless; fasteners into bronze through-hulls, shafts or wood use silicon bronze so both sit close on the galvanic series — never fasten 316 stainless into aluminium without isolation.","applies":["fastener","hardware","through-hull"],"value":{"options":["316 stainless","silicon bronze"]},"basis":"Corrosion-resistant, low-magnetic marine fastener alloys matched by galvanic compatibility to the part they join","sources":["astm-a276","astm-b98"],"tags":["fastener","316","silicon-bronze","material"]},{"id":"galvanic-isolation-rule","kind":"rule","tier":1,"title":"Isolating stainless/bronze fasteners from aluminium","summary":"Never bed a 316-stainless or bronze fastener/fitting directly against bare aluminium — insert a 1-2 mm nylon or Delrin isolation bushing/washer and a non-conductive bedding compound, or the anodic aluminium pits and fails within one salt-water season.","applies":["fastener","aluminium hull","corrosion"],"value":{"min":1,"max":2,"unit":"mm"},"basis":"Galvanic series separation between stainless/bronze and aluminium drives rapid anodic attack on the aluminium without a dielectric break","sources":["abyc-e2","gerr-boat-strength"],"tags":["galvanic","isolation","aluminium","corrosion"]},{"id":"anode-sizing-by-water-type","kind":"dimension","tier":1,"title":"Sacrificial anode alloy by water type","summary":"Match the anode alloy to the water: zinc (−1.05 V) for salt, aluminium (−1.10 V) for salt or brackish, magnesium (−1.60 V) for fresh only — zinc passivates in fresh water within 2–4 weeks. Size anodes for 1 year at ≤ 50 % consumption.","applies":["anode","cathodic protection","corrosion"],"value":{"table":[{"water":"salt","alloy":"zinc or aluminium"},{"water":"brackish","alloy":"aluminium"},{"water":"fresh","alloy":"magnesium"}]},"basis":"ABYC E-2 anode-alloy selection by electrolyte resistivity and passivation behaviour","sources":["abyc-e2"],"tags":["anode","zinc","aluminium","magnesium","cathodic-protection"]},{"id":"limber-hole-diameter","kind":"dimension","tier":1,"title":"Limber hole diameter through stringers/frames","summary":"Limber holes that let bilge water pass under stringers and frames to the pump pickup run ⌀25-40 mm — too small clogs with debris and strands water in a compartment, too large weakens the stringer's shear web.","applies":["limber hole","bilge","stringer","drainage"],"value":{"min":25,"max":40,"unit":"mm"},"basis":"Common bilge limber-hole sizing balancing drainage flow against stringer/frame shear-web strength","sources":["iso-15083","gerr-boat-strength"],"tags":["limber-hole","bilge","drainage"]},{"id":"self-bailing-deck-height","kind":"rule","tier":1,"title":"Self-bailing cockpit sole height above waterline","summary":"A self-bailing cockpit sole must sit ≥ 150-300 mm above the static waterline (more toward 300 mm on a boat that squats under load or heels hard) so cockpit scuppers drain by gravity instead of siphoning seawater back in when the transom digs in.","applies":["cockpit","scupper","self-bailing","drainage"],"value":{"min":150,"max":300,"unit":"mm"},"basis":"USCG 33 CFR 183 and common small-craft practice for self-bailing cockpit freeboard over the loaded waterline","sources":["uscg-33cfr183"],"tags":["self-bailing","cockpit","waterline","drainage"]},{"id":"outboard-transom-heights","kind":"dimension","tier":1,"title":"Outboard transom height by shaft length","summary":"Outboard shaft length is set by transom height, top of transom to keel line: 15 in (381 mm) short shaft, 20 in (508 mm) long, 25 in (635 mm) extra-long, 30 in (762 mm) ultra-long — the wrong shaft cavitates (too short) or drags the lower unit too deep.","applies":["outboard","transom"],"value":{"options":[15,20,25,30],"unit":"in"},"basis":"Outboard-industry standard shaft-length series matched to transom height","sources":["outboard-shaft-length-guide"],"tags":["outboard","transom","shaft-length"]},{"id":"transom-thickness","kind":"dimension","tier":1,"title":"Outboard transom thickness","summary":"A transom built to carry an outboard runs 38-64 mm thick (cored GRP or solid timber/plywood core), scaling with engine weight and thrust; thin-transom boats need a doubler plate under the clamp/bolt pattern rather than relying on the raw laminate.","applies":["transom","outboard"],"value":{"min":38,"max":64,"unit":"mm"},"basis":"ISO 12215-5 transom scantling method scaled to outboard thrust and weight","sources":["iso-12215-5"],"tags":["transom","thickness","outboard"]},{"id":"material-grp-eglass-polyester","kind":"material","tier":1,"title":"E-glass/polyester GRP hull laminate","summary":"The default small-craft hull laminate is E-glass woven roving/chopped-strand mat in orthophthalic or isophthalic polyester resin, ~35-45% fibre weight fraction in a hand-laid hull, density ~1.5-1.6 g/cm3 — cheaper and more water-permeable than a vinylester laminate below.","applies":["hull","grp","fiberglass hull"],"value":{"table":[{"property":"fibre-weight-fraction","min":35,"max":45,"unit":"%"},{"property":"density","value":1.55,"unit":"g/cm3"}]},"basis":"Standard E-glass/polyester hand-laid marine laminate composition and density","sources":["iso-12215-5"],"tags":["material","grp","e-glass","polyester"]},{"id":"material-316-stainless","kind":"material","tier":1,"title":"316 (A4) stainless steel for deck hardware","summary":"316 stainless is the default marine deck-hardware/fastener alloy: ~8.0 g/cm3 density, molybdenum-alloyed for better chloride/crevice resistance than 304, though it still corrodes in an oxygen-starved crevice without flushing or isolation.","applies":["deck hardware","fastener","stanchion"],"value":{"value":8,"unit":"g/cm3"},"basis":"ASTM A276 Type 316 stainless bar/shape density and standard marine-grade corrosion behaviour","sources":["astm-a276"],"tags":["material","316","stainless"]}]}